introduction - lincoln county, oregon · lincoln county nhmp july 2015 page ce-3!...

Lincoln County NHMP July 2015 Page II-i

VOLUME II: HAZARD ANNEX

Introduction

Lincoln County and the cities of Depoe Bay, Newport, Lincoln City, Siletz, Toledo, Waldport, and Yachats are subject to the following natural hazards:

• Coastal Erosion • Drought • Earthquake • Flood • Landslide • Tsunami • Volcano • Wildfire • Windstorm • Winter Storm (Snow/ Ice)

The following sections identify and profile the location, extent, previous occurrences, and future probability of the hazards listed above. Additional information about each hazard can be found in the Oregon Natural Hazards Mitigation Plan – Regional Risk Assessment -‐ Region 1: Oregon Coast1. Mapped location, extent, and vulnerability information is located in Volume I, Section 2 – Risk Assessment.

1 Oregon Department of Land Conservation and Development (DLCD), 2015. Oregon Natural Hazards Mitigation Plan.

Page II-ii July 2015 Lincoln County NHMP

This page intentionally left blank.

Lincoln County NHMP July 2015 Page CE-1

COASTAL EROSION

Significant Changes Since the 2009 Plan

Causes and Characteristics of the Hazard Coastal erosion is a natural process that continually affects the entire coast. Erosion becomes a hazard when human development, life and safety are threatened. Waves, currents, tides and storms resulting in episodic and recurrent erosion constantly affect beaches, sand spits, dunes and bluffs. Shoreline retreat may be gradual over a season or many years, or it can be drastic, with the loss of substantial upland area during the course of a single storm event.

Various combinations of large waves, storm surges, rip cell embayments, high winds, rain, runoff, flooding, or increased water levels and ocean conditions caused by periodic El Niño events cause Ocean erosion. Coastal bluffs comprised of uplifted marine terrace deposits and especially coastal dunes are vulnerable to both chronic erosion hazards.

Coastal erosion hazard poses a threat to structures and other development through the retreat of the shoreline from periodic high rates of beach, dune and bluff erosion and from mass wasting of sea cliffs in the form of landslides and slumps due to wave attack and geologic instability.

Coastal erosion is considered a chronic hazard, meaning it is usually local in nature, and the threats to human life and property that arise from it are generally less severe than those associated with catastrophic hazards. However, the wide distribution and frequent occurrence of chronic hazards such as coastal erosion makes them more of an immediate concern.

The damage caused by coastal erosion is usually gradual and cumulative. However, storms that produce large winter waves, heavy rainfall and/or high winds may result in very rapid erosion or other damage that can affect properties and infrastructure in a matter of hours. The regional, oceanic and climatic environments that result in intense winter storms determine the severity of chronic erosion hazards along the Oregon coast.

History of Coastal Erosion in Lincoln County Chronic coastal erosion has impacted development along the Lincoln County coast for decades. Examples include the Jump Off Joe area in Newport, where a landslide, undermined by ocean wave attack, accelerated during the mid 1940s, carrying roads, drain

There are no significant changes in the potential for Coastal Erosions to occur in Lincoln County since 2009. However, additional information regarding the hazard as reported in DOGAMI Open-‐File Report OFR O-‐04-‐09 (2004) is included in this update. In addition, minor changes to the format of the section have occurred.

Page CE-2 July 2015 Lincoln County NHMP

pipes, and 15 houses seaward to their destruction.2 Other examples include the severe erosion which took place on the Salishan Spit in the early 1970s, resulting in the destruction of one home under construction. Only a massive effort to armor the shoreline saved the remaining development on the spit. In similar episodes, development on the Bayshore Spit at the mouth of Alsea Bay was threatened by rapid erosion, first in the 1985 El Nino, and again in similar conditions in the winter of 1998. Emergency shore front hardening was employed to save several homes in the Gleneden Beach area that were threatened by bluff face failure.

More information on the history of this hazard can be found in the Regional Risk Assessment for Region 1 of the Oregon NHMP.

Risk Assessment

Hazard Identification Coastal erosion is a chronic hazard affecting the entire Lincoln County Coast. There are a variety of identifiable factors which affect shoreline stability. Dune-‐backed shorelines, which are most susceptible to wave attack, make up only a small portion of the Lincoln County coast. Processes of wave attack, including undercutting and wave overtopping, are the primary processes affecting shoreline stability in these areas. Bluff-‐backed shorelines, while less susceptible to rapid shoreline retreat from wave attack, are nonetheless impacted over time by coastal erosion, particularly during large storm events which result in the formation of rip cell embayments.

Coastal recession rates for Lincoln County were estimated and mapped in the Environmental Hazard Inventory of Coastal Lincoln County, RNKR Associates, 1978. More recently DOGAMI produced two publications documenting the known extent and location of coastal erosion and associated hazards: Evaluation of Coastal Erosion Hazard Zones along Dune and Bluff-‐Backed Shorelines for southern Lincoln County: Seal Rock to Cape Perpetua (Open File Report O-‐07-‐03) and for northern Lincoln County: Cascade Head to Seal Rock (Open File Report O-‐04-‐09).3 Maps from both the RNKR and DOGAMI reports are available at the Department of Planning and Development; the DOGAMI reports are also available on their publications page: http://www.oregongeology.org/.

Probability Assessment Coastal erosion can, and does, occur along the entire Lincoln County coastline. The probability of a coastal erosion event happening is based in part on probabilistic (waves) and deterministic (water levels) values.4 The active hazard zone for Lincoln County includes coastal bluff and dunes that are undergoing erosion whether by waves, near-‐shore sediment

2 DOGAMI. Geologic Hazards on the Oregon Coast: Coastal Landslides. http://www.oregongeology.com/sub/earthquakes/Coastal/CoastalLandslides.htm 3 DOGAMI. 2004. Evaluation of Coastal Erosion Hazard Zones Along Dune and Bluff Backed Shorelines In Lincoln County, Oregon: Cascade Head to Seal Rock. Open-‐File Report O-‐04-‐09; and DOGAMI. 2007. Evaluation of Coastal Erosion Hazard Zones Along Dune and Bluff Backed Shorelines In Southern Lincoln County, Oregon: Seal Rock to Cape Perpetua. Open-‐File Report O-‐07-‐03.

4 Oregon Natural Hazard Mitigation Plan. Department of Land Conservation and Development, 2015.


transport, or mass wasting processes.5 The active-‐hazard zone for dune-‐backed shorelines reflects the area of historic transformation and for bluff-‐backed shorelines the active-‐hazard zone includes the beach, bluff toe, and escarpment. DOGAMI has completed coastal erosion hazard maps for Lincoln County that depict the following hazard zones:6

• Active-‐Hazard Zone: Area of active, ongoing erosion. • High-‐Hazard Zone: High likelihood that the area could be affected by active erosion

in the next 60 years. • Moderate-‐Hazard Zone: Moderate likelihood that the area could be affected by

active erosion in the next 60 to 100 years. • Low-‐Hazard Zone: Low but significant likelihood that the area could be affected by

active erosion in the next 60 to 100 years.

Within Lincoln County the active-‐hazard zone varies in width from a few meters on cliffy headlands to hundreds of meters on low slopping beaches. Along dune-‐backed beaches the active-‐hazard zone experiences near constant change due to movement of dunes, while on bluff-‐backed shorelines the active-‐hazard zone includes large areas of active, or potentially, active landslides. For more information see Appendix A “Erosion Hazard Maps” of Open-‐File Report O-‐04-‐09 and Plate 1 of Open-‐File Report O-‐07-‐03.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing coastal erosion is “high”, meaning at least one incident is likely within the next 10 – 35 year period. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.7

Vulnerability Assessment Buildings, parks and various infrastructure located along the ocean shore are vulnerable to coastal erosion. This is most obvious in low-‐lying, dune backed shoreline areas adjacent to bays or the ocean; it is also the case in areas of bluff backed beaches where buildings and infrastructure have been located on readily erodible materials (e.g., consolidated sand, weakly cemented sandstone, siltstone, etc.). The problem is historic.

There are numerous examples of buildings and infrastructure threatened or damaged by wave attack/erosion (e.g. Salishan Spit, Bayshore Spit).

The Oregon NHMP Hazard Profile considers Lincoln County to be the second most vulnerable county to coastal erosion. Particularly susceptible are the areas listed below:

• Yachats to Alsea Spit (erosion) • Waldport (erosion and flooding) • Alsea Spit (erosion) • Seal Rock (erosion and landsliding)

5 DOGAMI. 2014, unpublished draft. Risk Report for Lincoln County Study Area: Cities of Depoe Bay, Lincoln City, Newport, Siletz, Toledo, Waldport and Yachats, Oregon; and Lincoln County, Oregon.

6 DOGAMI. 2007. Evaluation of Coastal Erosion Hazard Zones Along Dune and Bluff Backed Shorelines In Southern Lincoln County, Oregon: Seal Rock to Cape Perpetua. Open-‐File Report O-‐07-‐03.



• Ona Beach to Southbeach (erosion and landsliding) • Newport (landsliding) • Beverly Beach (erosion and landsliding) • Gleneden Beach to Siletz (erosion, landsliding, and flooding) • Lincoln City (erosion and landsliding)

Highway 101 is the major infrastructure component vulnerable to coastal erosion. In Lincoln County, much of the problem is linked to the local geology. Bedrock conditions can and do change abruptly within very short distances. This results in an inconsistent highway foundation; some sections are more susceptible to erosion than others and require continuous maintenance. There is no practical solution outside of relocation of the highway; in most cases, this option is not financially feasible at this point in time.

The Lincoln County Natural Hazards Steering Committee rated Lincoln County as having a “moderate” vulnerability to the coastal erosion hazard; meaning between 1 -‐ 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.8 Note: this is not an official estimate.

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I, Section 2) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the Coastal Erosion hazard is rated #7, out of 13 rated hazards, with a total score of 180.

Community Hazard Issues Coastal erosion can affect utilities, transportation networks, and essential structures. Coastal erosion can cause immediate threat to life and property. Disruption of infrastructure, roads, and critical facilities may also have a long-‐term effect on the residents and economy of Lincoln County. If roads, lifelines, and critical facilities aren’t accessible due to coastal erosion, this compounds hazard events. Highway 101 is highly susceptible to coastal erosion and in many stretches, is the only connecting road going north-‐south. For example, in the event of a tsunami, those injured by the initial wave may not be able to reach area hospitals due to wave induced coastal erosion which could potentially make Highway 101 impassable. Therefore, construction, repair, and inspection of transportation networked with essential structures should receive high priority.

Property and structures subject to damage consist primarily of ocean front residences and commercial uses, such as motels. The susceptibility to damage of these properties can be

8 Ibid.


influenced and, in some cases, intensified by human activities. Major actions such as jetty construction and maintenance dredging can have long-‐term effect on large sections of the coast. This is particularly true along dune-‐backed and inlet-‐affected shorelines. The planting of European beach grass since the early 1900s has locked up sand in the form of high dunes. This in turn has contributed to the net loss of beach sand and increased beach erosion. Residential and commercial development can affect shoreline stability over shorter periods of time and in smaller geographic areas. Activities such as grading and excavation, surface and subsurface drainage alterations, vegetation removal, and vegetative as well as structural shoreline stabilization can all reduce shoreline stability. Finally, heavy recreational use in the form of pedestrian and vehicular traffic can affect shoreline stability over shorter time frames and smaller spaces. Because these activities may result in the loss of fragile vegetative cover they are of particular concern along dune-‐backed shorelines. Graffiti carving along bluff-‐backed shorelines is another byproduct of recreational use that can damage fragile shoreline stability. 9

More information on this hazard can be found in the Regional Risk Assessment for Region 1 of the Oregon NHMP.

Existing Authorities, Policies, Programs, and Resources

Lincoln County Land Use Planning

Lincoln County land use regulations addresses development on lands subject to ocean erosion. Section 1.1925 of the land use code establishes requirements for ocean front setbacks for new development designed to compensate for identified shoreline recession. In addition, Section 1.1930 establishes standards for development in beach and dune areas intended to prevent development in identified critical hazard areas and reduce adverse impacts of development on shoreline stability.

As previously noted, coastal erosion hazards are identified in Environmental Hazard Inventory of Lincoln County, RNKR Associates, 1978, and in DOGAMI Open File Reports 0-‐04-‐09 and 0-‐07-‐01. Maps included in these studies are available at the Lincoln County Department of Planning and Development.

Hazard Mitigation Action Items There are two identified Coastal Erosion action items for Lincoln County; in addition, several of the Multi-‐Hazard action items affect the Coastal Erosion hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

9 Department of Land Conservation and Development. Coastal Hazards Alleviation Technique

Lincoln County NHMP July 2015 Page DR-1

DROUGHT


Causes and Characteristics of the Hazard Drought can be defined in several ways. The American Heritage Dictionary defines drought as "a long period with no rain, especially during a planting season." Another definition of drought is a deficiency in surface and sub-‐surface water supplies. In socioeconomic terms, drought is present when a physical water shortage begins to affect people, individually and collectively, and the area’s economy.

Drought is typically measured in terms of water availability in a defined geographical area. It is common to express drought with a numerical index that ranks severity. The Oregon Drought Severity Index is the most commonly used drought measurement in the state because it incorporates both local conditions and mountain snow pack. The Oregon Drought Severity Index categorizes droughts as mild, moderate, severe, and extreme.

Meteorological or Climatological Droughts

Meteorological droughts are defined in terms of the departure from a normal precipitation pattern and the duration of the event. These droughts are a slow-‐onset phenomenon that can take at least three months to develop and may last for several seasons or years.

Agricultural Droughts

Agricultural droughts link the various characteristics of meteorological drought to agricultural impacts. The focus is on precipitation shortages and soil-‐water deficits. Agricultural drought is largely the result of a deficit of soil moisture. A plant's demand for water is dependent on prevailing weather conditions, biological characteristics of the specific plant, its stage of growth, and the physical and biological properties of the soil.

Hydrological Droughts

Hydrological droughts refer to deficiencies in surface water and sub-‐surface water supplies. It is measured as stream flow, and as lake, reservoir, and ground water levels. Hydrological measurements are not the earliest indicators of drought. When precipitation is reduced or deficient over an extended period of time, the shortage will be reflected in declining surface and sub-‐surface water levels.

There are no significant changes in the potential for droughts to occur in Lincoln County since 2009. Based on recent drought history the steering committee opted to increase the county’s vulnerability to drought to “high” based upon water availability and dry forest conditions that increase wildfire risk. In addition, minor changes to the format of the section have occurred.

Page DR-2 July 2015 Lincoln County NHMP

Drought is typically measured in terms of water availability in a defined geographical area. It is common to express drought with a numerical index that ranks severity. The Oregon Drought Severity Index is the most commonly used drought measurement in the state because it incorporates local conditions and mountain snowpack. The Oregon Drought Severity Index categorizes droughts as mild, moderate, severe, and extreme.

History of the Hazard in Lincoln County There are no records of a severe drought in Lincoln County; however, Lincoln County was included in an Oregon drought declaration that included all 36 counties (EO-‐92-‐21). Drought is generally averted as a result of the County’s high rainfall from moist air masses moving onto land from Pacific Ocean, especially during winter months. Table II-‐1 describes droughts that affected the region, but no recorded damages in Lincoln County could be found.

Table II-1 History of Droughts

Source: Oregon State Natural Hazard Mitigation Plan 2015; George and Ray Hatton, The Oregon Weather Book (1999), and the Oregon Secretary of State's Office, Archives Division

The Water Availability Committee utilizes the Surface Water Supply Index (SWSI) from the Natural Resources Conservation Service to derive the Oregon Drought Severity Index that is reported to the Drought Council10. The SWSI is an index of current water conditions throughout the state. The index utilizes parameters derived from snow, precipitation, reservoir and stream flow data. The data is gathered each month from key stations in each basin. The lowest SWSI value, -‐4.1, indicates extreme drought conditions. The highest SWSI value, +4.1, indicates extreme wet conditions. The mid-‐point is 0.0, which indicates a normal water supply.11 The table below shows the monthly history of SWSI values from 1982 to 2015. Research shows that the periods of drought have fluctuated; a severe drought period occurred from about 1987 to 1996 (with short periods of non-‐drought), between 1998 and 2010 a period of moderate drought occurred (punctuated by drier years). Since about 2006, conditions in the North Coast Basin have been near normal or wet, except for a few shorter periods of mild drought conditions (including from 2013 to 2014).

10 State Emergency Operations Plan, Drought Annex, (2002)

11 Barry Norris, “Planning for Drought,” Water Resources Department (2001).

Date Location Characteristics1904%1905 Statewide A/state%wide/drought/period/of/about/18/months1917%1931 Statewide A/very/dry/period/puncuated/by/brief/wet/spells/in/1920%21/and/1927

1928%1941 Statewide

A/significant/drought/affected/all/of/Oregon/from/1928/to/1941./The/prolonged/statewide/drought/created/significant/problems/for/the/agricultural/industry./Punctuated/by/a/three%year/intense/drought/period/from/1939%1941.

1976%1981 Western/Oregon

Intense/drought/in/western/Oregon;/1976%77/driest/year/of/century.

1985%1997 StatewideA/dry/period/lasting/from/1985/to/1994/caused/significant/problems/statewide./The/peak/year/was/1992,/when/the/state/declared/a/drought/emergency./

2001%2002All/Regions/except/2/&/3 Extreme/drought/conditions/in/the/region;/Deschutes/County/decleared/

state/of/emergency/promting/Drought/Declaration/by/Executive/Order//01%17/


Figure II-1 SWSI Values for the North Coast Basin (1982-2015)

Source: Department of Agriculture-‐Natural Resources Conservation Service, “Surface Water Supply Index, Upper Lincoln Basin” www.or.nrcs.usda.gov. Accessed March 2015.

The figure below shows the county’s current drought conditions monitor according to the National Drought Mitigation Center at the University of Nebraska, Lincoln. The measurement shown displays the percent area of drought severity conditions. It indicates that Lincoln County is currently experiencing abnormally dry conditions, but is not registering drought conditions.12

12 USDM “U.S. Drought Monitor Classification Scheme”

!4#

!3#

!2#

!1#

0#

1#

2#

3#

4#

1982# 1985# 1988# 1991# 1994# 1997# 2000# 2003# 2006# 2009# 2012# 2015#

Surface#Water#Supply#Index#


Figure II-2 U.S. Drought Monitor – Oregon

Source: National Drought Mitigation Center, University of Nebraska, Lincoln. Droughtmonitor.unl.edu, Accessed March 18, 2015.

Hazard Identification Lincoln County rarely experiences drought conditions. At the time the plan was developed, no data existed to assist in identifying the location or extent of the drought hazard in Lincoln County. Typically, droughts occur as regional events and often affect more than one county. In severe droughts, environmental and economic consequences can be significant. Although Lincoln County has not experienced the effects of a severe drought, the location and extent would presumably be countywide. In recent years, the State has addressed drought emergencies through the Oregon Drought Council. This interagency (state/federal) council meets to discuss climate outlooks, water and soil conditions, and advise the Governor as the need arises.

Probability Assessment Droughts are not uncommon in the State of Oregon, nor are they just an “east of the mountains” phenomenon. They occur in all parts of the state, in both summer and winter. Oregon’s drought history reveals many short-‐term and a few long-‐term events. The average recurrence interval for severe droughts in Oregon is somewhere between 8 and 12 years. Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a drought is “high,” meaning one incident is likely within the


next 10 – 35 year period.. Oregon has yet to undertake a statewide comprehensive risk analysis for drought, to determine probability or vulnerability for a given community. However, based upon the low availability of data the Oregon NHMPs Regional Risk Assessment assesses a low probability for drought in Lincoln County.13

Vulnerability Assessment Lincoln County is less vulnerable to drought impacts than most of Oregon, but droughts can still be problematic. Potential impacts to community water supplies are the greatest threat. Long-‐term drought periods of more than a year can impact forest conditions and set the stage for potentially destructive wildfires. Additional impacts are described in the following section, Community Hazard Issues. The Lincoln County Natural Hazards Steering Committee rated Lincoln County as having a “high” vulnerability to drought hazards, meaning 10-‐percent or more of the region’s population or assets would be affected by a major emergency or disaster. The Oregon NHMP does not assess a vulnerability rating for Region 1; however, the Oregon NHMP asserts that community water supplies are the greatest threat and that prolonged drought conditions (lasting more than a year) can affect forest conditions and lead to wildfires.14

Risk Analysis The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐6 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the drought hazard is rated #11, out of 13 rated hazards, with a total score of 145.

Future Climate Variability

One of the main aspects of the probability of future occurrences is its reliance on historic climate trends in order to predict future climate trends. Many counties in eastern Oregon are experiencing more frequent and severe droughts than is historically the norm, and many climate predictions see this trend continuing into the future. Temperatures in the Pacific Northwest region increased in the 20th Century by about 1.5 degrees Fahrenheit and are projected to increasingly rise by an average of 0.2 degrees to 1.0 degrees Fahrenheit per decade. Average temperature change by 2040 is projected to be 3.2 degrees Fahrenheit, and by 2080, 5.3 degrees Fahrenheit. Temperature increases will occur throughout all seasons, with the greatest variation occurring during summer months.15


14 Oregon Emergency Management, July 2003, County Hazard Analysis Scores

15 Climate Impacts Group, “Climate Change,” http://cses.washington.edu


Community Hazard Issues Drought is frequently an "incremental" hazard, meaning both the onset and end are often difficult to determine. Also, its effects may accumulate slowly over a considerable period of time and may linger for years after the termination of the event.

Droughts are not just a summer-‐time phenomenon; winter droughts can have a profound impact on agriculture, particularly east of the Cascade Mountains. Also, below average snowfall in higher elevations has far-‐reaching affects, especially in terms of hydro-‐electric power, irrigation, recreational opportunities and a variety of industrial uses.

Drought can affect all segments of a jurisdiction’s population, particularly those employed in water-‐dependent activities (e.g., agriculture, hydroelectric generation, recreation, etc.). Also, domestic water-‐users may be subject to stringent conservation measures (e.g., rationing) and could be faced with significant increases in electricity rates. In addition, water-‐borne transportation systems (e.g., ferries, barges, etc.) could be impacted by periods of low water.

There also are environmental consequences. A prolonged drought in forests promotes an increase of insect pests, which in turn, damage trees already weakened by a lack of water. A moisture-‐deficient forest constitutes a significant fire hazard (see the Wildfire summary). In addition, drought and water scarcity add another dimension of stress to species listed pursuant to the Endangered Species Act (ESA) of 1973.

More information on the drought hazard can be found in the Drought chapter of the State of Oregon’s Natural Hazards Mitigation Plan.


Existing mitigation activities include current mitigation programs and activities that are being implemented by city, county, regional, state or federal agencies and/or organizations.

Lincoln County currently addresses the drought hazard through water conservation measures and water monitoring.

Drought Council

The Drought Council is responsible for assessing the impact of drought conditions and making recommendations to the Governor’s senior advisors. The Water Availability Committee, a subcommittee of technical people who monitor conditions throughout the state and report these conditions monthly, advises the Drought Council. In this manner the Drought Council keeps up-‐to-‐date on water conditions.

Natural Resources Conservation Service

The United States Department of Agriculture Natural Resources Conservation Service (NRCS) has a regional service center located in Redmond (another is located in Warm Springs). The NRCS is dedicated to three main priorities involving resource preservation one among them


is water quantity and quality. The NRCS incorporates a conservation implementation strategy to preserve natural resources into the future.16

Hazard Mitigation Action Items

There are no identified Drought action items for Lincoln County; however, several of the Multi-‐Hazard action items affect the Drought hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

16 NRCS – Lincoln County “Information for Partners and Participants,” http://www.or.nrcs.usda.gov

Lincoln County NHMP July 2015 Page EQ-1

EARTHQUAKE


Causes and Characteristics of the Hazard Seismic events were once thought to pose little or no threat to Oregon communities. However, recent earthquakes and scientific evidence indicate that the risk to people and property is much greater than previously thought. Lincoln County is susceptible to earthquakes from three sources: 1) the off-‐shore Cascadia Subduction Zone (CSZ); 2) deep intra-‐plate events within the subducting Juan de Fuca Plate; and 3) shallow crustal events within the North American Plate.

All types of earthquakes in the region have some tie to the subducting, or diving, of the dense, oceanic Juan de Fuca Plate under the lighter, continental North American Plate. While all three types of earthquakes have the potential to cause major damage, subduction zone earthquakes pose the greatest danger. A major CSZ event could generate an earthquake with a magnitude of 9.0 or greater resulting in devastating damage and loss of life. Such earthquakes may cause great damage to the coastal area of Oregon as well as inland areas in western Oregon.

Subduction Zone Earthquakes

The Pacific Northwest is located at a convergent continental plate boundary, where the Juan de Fuca and North American tectonic plates meet. The two plates are converging at a rate of about 1.5 inches per year17. This boundary is called the Cascadia Subduction Zone (CSZ, see Figure II-‐3). It extends from British Columbia to northern California. Earthquakes are caused by the abrupt release of this slowly accumulated stress.

17 Interagency Hazard Mitigation Team. 2012. Oregon Natural Hazards Mitigation Plan. Salem, OR: Oregon Military Department – Office of Emergency Management

There are no significant changes in the potential for Earthquakes to occur in Lincoln County since 2009. However, there have been several new reports regarding the Cascadia Subduction Earthquake hazard that are document herein and within the Tsunami section. During the summer of 2015 DOGAMI will produce additional data that will enhance the county’s understanding of it’s vulnerability to the hazard. Minor changes to the format of the section have occurred.

Page EQ-2 July 2015 Lincoln County NHMP

Figure II-3 Cascadia Subduction Zone

Source: Shoreland Solutions. Chronic Coastal Natural Hazards Model Overlay Zone. Salem, OR: Oregon Department of Land Conservation and Development (1998) Technical Guide-‐3.

Although there have been no large recorded earthquakes along the offshore Cascadia Subduction Zone, similar subduction zones worldwide do produce "great" earthquakes with magnitudes of 8 or larger. They occur because the oceanic crust "sticks" as it is being pushed beneath the continent, rather than sliding smoothly. Over hundreds of years, large stresses build which are released suddenly in great earthquakes. Such earthquakes typically have a minute or more of strong ground shaking, and are quickly followed by numerous large aftershocks.

Subduction zones similar to the Cascadia Subduction Zone have produced earthquakes with magnitudes of 8.0 or larger. Historic subduction zone earthquakes include the 1960 Chile earthquake (magnitude 9.5), the 1964 southern Alaska (magnitude 9.2) earthquakes, the 2004 Indian Ocean earthquake (magnitude 9.0) and the 2011 Tohoku earthquake. Geologic evidence shows that the Cascadia Subduction Zone has generated great earthquakes, most recently about 300 years ago.18

Geologic evidence shows that the Cascadia Subduction Zone has also generated great earthquakes, and that the most recent one was about 300 years ago. Large earthquakes also occur at the southern end of the Cascadia Subduction Zone (in northern California near the Oregon border) where it meets the San Andreas Fault system.

Deep Intraplate Earthquakes

Occurring at depths from 18 to 60 miles below the earth’s surface in the subducting oceanic crust, deep intraplate earthquakes can reach magnitude 7.5.19 This type of earthquake is 18 Interagency Hazard Mitigation Team. 2012. Oregon Natural Hazards Mitigation Plan. Salem, OR: Oregon Military Department – Office of Emergency Management 19 Planning for Natural Hazards: Oregon Technical Resource Guide, Community Planning Workshop, (July 2000), p. 8-‐8.

!


more common in the Puget Sound; in Oregon these earthquakes occur at lower rates and have none have occurred at a damaging magnitude.20 The February 28, 2001 earthquake in Washington State was a deep intraplate earthquake. It produced a rolling motion that was felt from Vancouver, British Columbia to Coos Bay, Oregon and east to Salt Lake City, Utah.21

Crustal Fault Earthquakes

These are the most common earthquakes and occur at relatively shallow depths of 6-‐12 miles below the surface.22 When crustal faults slip, they can produce earthquakes of magnitudes up to 7.0. Although most crustal fault earthquakes are smaller than 4.0 and generally create little or no damage, some of them can cause extensive damage. Crustal earthquakes occur in the North American plate at relatively shallow depths of 10–20 km (6–12 mi) below the surface. Earthquakes related to volcanic activity can also affect the region.

The specific hazards associated with earthquakes are explained below:

Ground Shaking

Ground shaking is the motion felt on the earth’s surface caused by seismic waves generated by the earthquake. Ground shaking is the primary cause of earthquake damage. The strength of ground shaking depends on the magnitude of the earthquake, the type of fault that is slipping, and distance from the epicenter (where the earthquake originates). Buildings on poorly consolidated and thick soils will typically see more damage than buildings on consolidated soils and bedrock.

Ground Shaking Amplification

Ground shaking amplification refers to the soils and soft sedimentary rocks near the surface that can modify ground shaking from an earthquake. Such factors can increase or decrease the amplification (i.e., strength) as well as the frequency of the shaking. The thickness of the geologic materials and their physical properties determine how much amplification will occur. Ground motion amplification increases the risk for buildings and structures built on soft and unconsolidated soils.

20 Interagency Hazard Mitigation Team. 2012. Oregon Natural Hazards Mitigation Plan. Salem, OR: Oregon Military Department – Office of Emergency Management 21 Hill, Richard. “Geo Watch Warning Quake Shook Portland 40 Years Ago.” The Oregonian. October 30, 2002. 22 Madin, Ian P. and Zhenming Wang, Relative Earthquake Hazard Maps Report, DOGAMI, 1999.

“Due to the amount of faulting in the area, [the 1999 Klamath Falls earthquake] is just business as usual for such a geologically active region. Historic evidence, combined with geologic evidence for large numbers of earthquakes in the prehistoric past, suggest that one or more earthquakes capable of damage (magnitude 4 – 6) hit south-‐central Oregon every few decades, so it pays to be prepared.”

James Roddey, DOGAMI


Surface Faulting

Surface faulting are planes or surfaces in Earth materials along which failure occurs. Such faults can be found deep within the earth or on the surface. Earthquakes occurring from deep lying faults usually create only ground shaking.

Liquefaction and Subsidence

Liquefaction occurs when ground shaking causes wet, granular soils to change from a solid state into a liquid state. This results in the loss of soil strength and the soil’s ability to support weight. When the ground can no longer support buildings and structures (subsidence), buildings and their occupants are at risk.

The severity of an earthquake is dependent upon a number of factors including: 1) the distance from the earthquake’s source (or epicenter); 2) the ability of the soil and rock to conduct the earthquake’s seismic energy; 3) the degree (i.e., angle) of slope materials; 4) the composition of slope materials; 5) the magnitude of the earthquake; and 6) the type of earthquake.

Earthquake-Induced Landslides and Rockfalls

Earthquake-‐induced landslides are secondary hazards that occur from ground shaking and can destroy roads, buildings, utilities and critical facilities necessary to recovery efforts after an earthquake. Some Lincoln County communities are built in areas with steep slopes. These areas often have a higher risk of landslides and rockfalls triggered by earthquakes.

The severity of an earthquake is dependent upon a number of factors including: 1) the distance from the earthquake’s source (or epicenter); 2) the ability of the soil and rock to conduct the earthquake’s seismic energy; 3) the degree (i.e., angle) of slope materials; 4) the composition of slope materials; 5) the magnitude of the earthquake; and 6) the type of earthquake.

Tsunamis

Tsunamis are another secondary earthquake hazard created by events occurring under the ocean. A tsunami, often incorrectly referred to a “tidal wave,” is a series of gravity-‐induced waves that can travel great distances from the earthquake’s origin and can cause serious flooding and damage to coastal communities. Tsunami hazard is addressed in detail in a separate annex.

The severity of damage caused by an earthquake is dependent upon a number of factors including: 1) the distance from the quake’s source (or epicenter); 2) the ability of the soil and rock to conduct the quake’s seismic energy; 3) the degree (i.e., angle) of slope materials; 4) the composition of slope materials; 5) the magnitude of the earthquake; and 6) the type of earthquake.


History of the Hazard in Lincoln County The area of Oregon west of the Cascade Mountain Range is at high risk from earthquakes and their collateral damage. Risk is ultimately dependant upon location of the epicenter, soil conditions, and building construction.

A summary of significant earthquake events in the Lincoln County region is found in the table below.

Table II-2 Selected Earthquakes, M 5.0+ (1971-2008)

Source: Ivan Wong and others, "A Look Back at Oregon's Earthquake History, 1841-‐1994," in Oregon Geology, (1995), 125-‐1

The Pacific Northwest experienced a subduction zone earthquake estimated at magnitude 9 on January 26, 1700. The earthquake generated a tsunami that caused damage as far away as Japan. Cascadia subduction zone earthquakes and associated tsunamis have occurred on average every 500 years over the last 3,500 years in the Pacific Northwest. The time between events has been as short as 100 to 200 years and as long as 1000 years. The geologic record indicates that over the last 10,000 years approximately 42 tsunamis have been generated off the Oregon Coast in connection to ruptures of the CSZ (19 of the events were full-‐margin ruptures and arrived approximately 15-‐20 minutes after the earthquake).23


Date Location Magnitude Comments

Approximate+years:+1400+BCE,+1050,+BCE+600+BCE+400,+750,+900

Offshore,+Cascadia+subduction+zone

Probably8.0G9.0

Based+on+studies+of+earthquakes+and+tsunamis+in+Willapa+Bay,+WA.+These+are+the+midpoints+of+the+age+ranges+for+these+six+events.

January+1700 Offshore,+Cascadia+Subduction+zone

Approximately+9.0

Generated+a+tsunami+that+struck+Oregon,+Washington+and+Japan;+destroyed+Native+American+villages+along+the+coast.

November+1873 Brookings+area 7.3Intraplate+event;+origin+near+Gorda+block+of+the+Juan+de+Fuca+plate;+chimneys+damaged;+no+aftershocks

November+1962 Portland,+OR 5.2+to+5.5 Crustal+event,+damage+to+homes

March+1993 Scotts+Mills,+OR 5.6crustal+eventl++FEMAG1004GDRGOR;+$28+million+in+damage+(homes,+schools,+businesses,+state+buildings)

September+20,+1993 Klamath+County 5.9+and+6.0 Two+deaths,+$10+million+damage,+including+county+courthouse;+rockfalls+induced+by+ground+motion.


Figure II-4 Cascadia Earthquake Timeline

Source: DOGAMI

Lincoln County routinely has small earthquake events. The earthquakes shown in Figure II-‐5 are relatively insignificant. They were felt by a number of citizens but little to no structural/property damage resulted. The map shows clusters of earthquakes occurring off the shoreline of Lincoln County. There is no historic record of significant crustal earthquakes centered in the region in the past 153 years, although Oregon has experienced crustal earthquakes that originated outside the region. The geologic record shows that movement has occurred along numerous offshore faults as well as some onshore faults. The faulting has occurred over the past 20,000 years.

Figure II-5 Earthquake Epicenters (1971-2008)

Source: Oregon HazVu: Statewide Geohazards Viewer (HazVu)


More recently there have been a number of earthquakes off of the Lincoln County coast. In 2003 there was a magnitude 6.3 earthquake along the Blanco Fracture Zone, one of several seismically active transform faults off the coast of Oregon. In July of 2004 there was a magnitude 4.9 earthquake located 19 miles west of Yachats. Within a three-‐week period in April of 2008, there were more than 600 tremors, three of which were magnitude 5 or higher. 24

The Scotts-‐Mill Earthquake, which occurred 54 miles south of Portland on March 25, 1993, is largely considered Oregon’s most significant earthquake in written history, and was felt as far away as Newport. It had a magnitude of 5.7 and caused widespread, though generally minor, damage in the central and northern Willamette Valley. The damage estimate for this quake was $28.4 million. The Klamath County earthquakes on September 20, 1993, caused two deaths and approximately $7.5 million in damage. One person was killed when the car he was driving was crushed by a boulder in an earthquake-‐induced rock fall, and another person died of a heart attack. More than 1,000 homes and commercial buildings were damaged. 25

The last known great earthquake to hit the Lincoln County area was in January of 1700. This CSZ event also produced a tsunami, which is discussed in the Tsunami chapter.

Hazard Identification Until recently, earthquakes were thought to pose little risk to Oregon and its residents. Through geologic investigation and more recent earthquake events, this perception has changed drastically. The Cascadia Subduction Zone (illustrated in Figure II-‐3 above) presents the potential for an earthquake of magnitude 9.0 or higher. This presents a significant threat to Oregon’s coastal communities as they will likely be closer to the epicenter, and will therefore suffer more shaking and collateral damage. The Cascadia event would result in buildings and infrastructure suffering varying amounts of damage. Large portions of Highway 101 and roads across the Coast Range would likely be impassable. This would for the most part sever travel between the coast and the Willamette Valley.

The Oregon Department of Geology and Mineral Industries (DOGAMI), in partnership with other state and federal agencies, has undertaken a rigorous program in Oregon to identify seismic hazards, including active fault identification, bedrock shaking, tsunami inundation zones, ground motion amplification, liquefaction, and earthquake induced landslides. DOGAMI has published a number of seismic hazard maps that are available for Oregon communities to use. The maps show liquefaction, ground motion amplification, landslide susceptibility, and relative earthquake hazards. OPDR used the DOGAMI Statewide Geohazards Viewer to present visual maps of recent earthquake activity (Figure II-‐5), liquefaction (soft soils, Figure II-‐6), and expected ground shaking for crustal events (Figure II-‐7) and the Cascadia Subduction Zone event (Figure II-‐8). The extent of the damage to structures and injury and death to people will depend upon the type of earthquake, proximity to the epicenter and the magnitude and duration of the event. The soft soils figure

24 Milstein, Michael, The Oregonian, Earthquakes continue off Oregon Coast: April 14, 2008. http://blog.oregonlive.com/breakingnews/2008/04/quakes_continue_off_oregon_coa.html

25 USGS, Earthquake Hazards Program, Historic Earthquakes http://earthquake.usgs.gov/regional/states/historical.php?


below shows that the areas of the population along the coastline are more susceptible to liquefaction than areas further in land and away from rivers.

Figure II-6 Earthquake Liquefaction (Soft Soil) Hazard


Figure II-7 Combined Earthquake Events Expected Shaking and Active Faults


Figure II-‐8 shows expected shaking with a Cascadia Earthquake. The figure shows that the entire county will receive severe to violent shaking.


Figure II-8 Cascadia Earthquake Expected Shaking


The Department of Geology and Mineral Industries (DOGAMI), in partnership with other state and federal agencies, has commenced a program to identify seismic hazards and risks. A number of studies have been published. Among other data, DOGAMI has created maps that identify areas in selected Oregon communities that will suffer more damage, relative to other areas, during a damaging earthquake. As part of the Risk MAP project DOGAMI will provide additional risk assessment information for Lincoln County including a damage assessment during the summer of 2015.

Probability Assessment

According to the Oregon NHMP, the return period for the largest of the CSZ earthquakes (Magnitude 9.0+) is 530 years with the last CSZ event occurring 314 years ago in January of 1700. The probability of a 9.0+ CSZ event occurring in the next 50 years ranges from 7 -‐ 12%. Notably, 10 -‐ 20 “smaller” Magnitude 8.3 -‐ 8.5 earthquakes identified over the past 10,000 years affect only the southern half of Oregon and northern California. The average return period for these events is roughly 240 years. The combined probability of any CSZ earthquake occurring in the next 50 years is 37 -‐ 43%.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a crustal earthquake is “high”, meaning one incident is likely within the next 10 – 35 year period; the committee believe that the County’s probability of experiencing a Cascadia earthquake is “moderate”, meaning one incident is likely within the next 35 – 75 year period. The previous NHMP did not separately assess crustal and Cascadia earthquake events; as such these ratings are new. Based upon available


information the Oregon NHMPs Regional Risk Assessment supports these probability rating for Lincoln County.26

Vulnerability Assessment

The Oregon Department of Geology and Mineral Industries (DOGAMI) has developed two earthquake loss models for Oregon based on the two most likely sources of seismic events: 1) the CSZ, and 2) combined crustal events. Both models are based on HAZUS, a computerized program, currently used by the Federal Emergency Management Agency (FEMA) as a means of determining potential losses from earthquakes.

The CSZ event is based on a potential 8.5 earthquake generated off the Oregon coast. The model does not take into account a tsunami, which probably would develop from the event (but not affect Lincoln County). The 500-‐year crustal model does not look at a single earthquake (as in the CSZ model); it encompasses many faults, each with a 10% chance of producing an earthquake in the next 50 years. The model assumes that each fault will produce a single “average” earthquake during this time. Neither model takes unreinforced masonry building into consideration. DOGAMI investigators caution that the models contain a high degree of uncertainty and should be used only for general planning purposes. Despite their limitations, the models do provide some approximate estimates of damage. Further mention is made of the potential for a large local tsunami related to a CSZ event. See the Tsunami section for current research being conducted to determine potential tsunami impact potential.

The Lincoln County Natural Hazards Steering Committee rated Lincoln County as having a “moderate” vulnerability to the crustal earthquake hazard, meaning it expected that between 1 – 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster; the committee rated the County as having a “high” vulnerability to the Cascadia earthquake hazard, meaning more than 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster. The previous NHMP did not separately assess crustal and Cascadia earthquake events; as such these ratings are new. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.27

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I, Section 2) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the Cascadia earthquake hazard is rated #3, out of 13 rated hazards, with a total


27 Ibid.


score of 209; while the crustal earthquake hazard is rated #12, out of 13 rated hazards, with a total score of 140.

Research suggests that the Cascadia Subduction Zone is capable of producing magnitude 9 earthquakes. Projected losses in the Cascadia region alone could exceed $12 billion with over 30,000 destroyed buildings and 8,000 lives lost in the event of a magnitude 8.5 Cascadia Subduction Zone earthquake. Table II-‐3 presents damage figures for Lincoln County for both an 8.5 Cascadia subduction zone event and a 500-‐year event. It should be noted that the figures have a high degree of uncertainty and should be used only for general planning purposes.

Community Hazard Issues

The effects of earthquakes span a large area. The degree to which earthquakes are felt, however, and the damages associated with them may vary. At risk from earthquake damage are unreinforced masonry buildings (which are numerous in Lincoln County), bridges built before earthquake standards were incorporated into building codes, sewer, water, and natural gas pipelines, petroleum pipelines, and other critical facilities and private property located within the county. The areas that are particularly vulnerable to potential earthquakes in the county have been identified as those with soft, alluvial sediments (high liquefaction potential). Areas of high liquefaction potential largely follow river and stream drainage channels, marshy areas, areas near lakes, and along the coast. In addition, areas that have been filled or graded are highly vulnerable to liquefaction. The land around the Hatfield Marine Science Center and the surrounding facilities is an example of an area that would be highly susceptible to liquefaction during a large scale seismic event. Lincoln County vulnerability to earthquakes is ranked as “moderate.” 28

Earthquake damage to roads and bridges can be particularly serious by hampering or cutting off the movement of people and goods and disrupting the provision of emergency response services. Such effects in turn can produce serious impacts on the local and regional economy by disconnecting people from work, home, food, school and needed commercial, medical and social services. A major earthquake can separate businesses and other employers from their employees, customers, and suppliers thereby further hurting the economy. Lincoln County is particularly susceptible to being isolated, due to its location along the coastline. Finally, following an earthquake event, the cleanup of debris can be a huge challenge for the community.

Death and Injury

Death and injury can occur both inside and outside of buildings due to falling equipment, furniture, debris, and structural materials. Likewise, downed power lines or broken water and gas lines endanger human life. Death and injury are highest in the afternoon when damage occurs to commercial and residential buildings and during the evening hours in residential settings.29

28 Oregon Emergency Management, July 2003, County Hazard Analysis Scores

29 Planning for Natural Hazards: Oregon Technical Resource Guide, Community Planning Workshop, (July 2000).


Disruption of Critical Facilities

Critical facilities are police stations, fire stations, hospitals, and shelters. These are facilities that provide services to the community and need to be functional after an earthquake event. The earthquake effects outlined above can all cause emergency response to be disrupted after a significant event.30 Tables II-‐3 and II-‐4 (below) and tables in the city addenda, display damage and collapse potential for structures including critical and essential facilities.

Economic Loss

Seismic activity can cause great loss to businesses, either a large-‐scale corporation or a small retail shop. Losses not only result in rebuilding cost, but fragile inventory and equipment can be destroyed. When a company is forced to stop production for just a day, business loss can be tremendous. Residents, businesses, and industry all suffer temporary loss of income when their source of finances are damaged or disrupted.

The potential losses from an earthquake in Lincoln County extend beyond those to human life, homes, property and the landscape. A recent earthquake damage model has not been conducted for Lincoln County, however, HAZUS loss estimation will be included with updates of the county’s Risk Report (expected in 2016). Based upon data from a 1999 DOGAMI report rough loss estimates are available. The economic base in Lincoln County is estimated at $2,668,000,000 (in 1999 dollars; ranking 16 of 36 Oregon counties); it is expected that the county will incur total direct losses valuing $624,000,000 (in 1999 dollars) for the Cascadia model and $793,000,000 (in 1999 dollars) for the 500-‐year model. The CSZ event direct losses amount to a loss ratio of 13-‐percent, while the 500-‐year model event direct losses amount to a loss ratio of 17-‐percent.31

30 Y. Wang & J.L. Clark, Special Paper 29, Earthquake Damage in Oregon: Preliminary Estimates of Future Earthquake Losses. 1999. DOGAMI. 31 Ibid. The loss ratio is determined as a percentage of the expected losses to the county’s economic base.


Table II-3 Lincoln County Earthquake Damage Summary

Source: Y. Wang & J.L. Clark, Special Paper 29, Earthquake Damage in Oregon: Preliminary Estimates of Future Earthquake Losses. 1999. DOGAMI.

While the expected losses have increased due to increased development in the county, as well as inflation, the loss ratio and relative damage for the county is expected to be similar. See table on the following page for more information on expected losses.

These figures have a high degree of uncertaintly and should be used only for genera l planning purposes. Because of rounding. numbers may nat add up to 100%.

Because the 500 year model includes severa l earthquakes. the number of ladties opera tiona l the "day offer" cannot be ca lCulated.

44

Uncoln County

Injuries

Deaths

Displaced households

Short term shelter needs

Economic losses for buildings

Operational the day afte r the quake:

Fire stations

Police s tations

Schools

Bridges

Economic losses to:

Highways

Airports

Communication systems:

Economic losses

Operating the day of the quake

Debris generat01d

8.5 Cascadia event

Building type None

Agriculture 10

Commercial 3

Education 7

Government 4

IndustrW 3

Residential 22

500 year model

Building type None

Agriculture 10

Commercial 4

Education 7

Government 5

IndustrW 4

Residential 20

8.5 Cascadia subduction zone event 500 year model

358 436

7 9

592 847

401 577

$624 million $792 million

26% NA

22% NA

19% NA

51% NA




26% NA

446 525

Percentage of buildings in damage categories

Slight Moderate Exten.•ive Complete

13 17 17 26

5 20 30 42

9 16 21 30

6 17 29 44

5 19 29 44

30 26 12 10

Percentage of buildings in damage categories

Slight Moderate Extensive Complete

14 19 18 22

7 23 31 35

10 18 22 26

7 21 31 37

6 22 30 36

30 28 13 9

Earthquake damage in Oregon


Local business economies are at substantial risk if an earthquake damages or otherwise necessitates the closure of any of the major transportation routes in Lincoln County.

Bridge Damage

All bridges can sustain damage during earthquakes, leaving them unsafe for use. More rarely, some bridges have failed completely due to strong ground motion. Bridges are a vital transportation link – damage to them can make some areas inaccessible.

Because bridges vary in size, materials, siting, and design, earthquakes will affect each bridge differently. Bridges built before the mid 1970's often do not have proper seismic reinforcements. These bridges have a significantly higher risk of suffering structural damage during a moderate to large earthquake. Bridges built in the 1980’s and after are more likely to have the structural components necessary to withstand a large earthquake.32 Table C-‐34 of Volume IV, Appendix C, Community Profile indicates that currently 31-‐percent of state owned bridges, 24-‐percent of county owned bridges, and 100-‐percent of city owned bridges are identified as distressed with structural or other deficiencies. During an earthquake event these bridges may fail and limit movement throughout the county.

Bridges are a vital transportation link – with even minor damages making some areas inaccessible. In the event that bridges become impassible, alternate transportation routes/means would need to be identified and utilized.

Damage to Lifelines

Lifelines are the connections between communities and critical services. They include water and gas lines, transportation systems, electricity, and communication networks. Ground shaking and amplification can cause pipes to break open, power lines to fall, roads and railways to crack or move, and radio or telephone communication to cease. Disruption to transportation makes it especially difficult to bring in supplies or services. All lifelines need to be usable after an earthquake to allow for rescue, recovery, and rebuilding efforts and to relay important information to the public. According to the Oregon Resilience Plan it is expected to take three to six months to restore electric service, one to three years to restore drinking water and sewer service, and up to three years to restore healthcare facilities following a CSZ event. 32 University of Washington website: www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/faq.html#3.

2001 Nisqually Earthquake

A 6.8 magnitude earthquake centered southwest of Seattle struck on February 28, 2001, followed by a mild aftershock the next morning, and caused more than $1 billion worth of damage. Despite this significant loss, the region escaped with relatively little damage for two reasons: the depth of the quake center and preparations by its residents. Washington initiated a retrofitting program in 1990 to strengthen bridges, while regional building codes mandated new structures withstand certain amounts of movement. Likewise, historic buildings have been voluntarily retrofitted with earthquake-‐protection reinforcements.


Fire

Downed power lines or broken gas mains can trigger fires. When fire stations suffer building or lifeline damage, quick response to quench fires is less likely. See Table II-‐4 for more information on buildings susceptible to collapse.

Debris

After damage occurs to a variety of structures, much time is spent cleaning up brick, glass, wood, steel or concrete building elements, office and home contents, and other materials. For more information on debris damage and removal see the Oregon Resilience Plan.

Building and Home Damage

Wood structures tend to withstand earthquakes better than structures made of brick or unreinforced masonry buildings.33 Building construction and design play a vital role in the survival of a structure during earthquakes. Damage can be quite severe if structures are not designed with seismic reinforcements or if structures are located atop soils that liquefy or amplify shaking. Whole buildings can collapse or be displaced.

Changes in the state building code seek to address seismic safety: In 2007, for example, all of Lincoln County was updated to seismic zone D2, which requires an increase in construction standards. Structures built after the 1990s in the Northwest use earthquake resistant designs and construction techniques. However, many buildings have been built before these building code updates. Generally the older the building, the more susceptible it is to damage from an earthquake. Approximately, two-‐thirds of Lincoln County homes were built prior to 1990 (see Table C-‐28 within Volume IV, Appendix C, Community profile for more detail).

In 2007, DOGAMI completed a rapid visual screening (RVS) of educational and emergency facilities in communities across Oregon, as directed by the Oregon Legislature in Senate Bill 2 (2005). RVS is a technique used by the Federal Emergency Management Agency (FEMA), known as FEMA 154, to identify, inventory, and rank buildings that are potentially vulnerable to seismic events. DOGAMI surveyed 43 facilities in Lincoln County; of these eight are within the unincorporated areas of the county (see City addenda for facilities within city jurisdiction).

DOGAMI scored each building with a ‘low,’ ‘moderate,’ ‘high,’ or ‘very high’ potential of collapse in the event of an earthquake. It is important to note that these rankings represent a probability of collapse based on limited observed and analytical data and are, therefore approximate rankings.34 To fully assess a building’s potential of collapse, a more detailed engineering study completed by a qualified professional is required, but the RVS study can help to prioritize which buildings to retrofit.

33 Wolfe, Myer, et al. Land Use Planning for Earthquake Hazard Mitigation: A Handbook for Planners, Special Publication 14, Natural Hazards Research and Applications Information Center. 34 State of Oregon Department of Geologic and Mineral Industries, “Implementation of 2005 Senate Bill 2 Relating to Public Safety, Seismic Safety and Seismic Rehabilitation of Public Building”, May 22, 2007, Open File Report 0-‐07-‐02.


The table below displays the rankings of all facilities within the county’s jurisdiction; each “X” represents one building within that ranking category. Of the buildings evaluated by DOGAMI using RVS, one building has very high (100% chance) collapse potential, and one building has high (greater than 10% chance) collapse potential; both are part of the Eddyville Charter School. All of the county’s public safety buildings located in the unincorporated areas of the county have “low” collapse potentials.

Table II-4 Rapid Visual Survey Scores

Source: DOGAMI 2007. Open File Report 0-‐07-‐02. Statewide Seismic Needs Assessment Using Rapid Visual Assessment.

The county and cities have opted to create one action item for all the facilities that have a “high” or “very high” rating (see Appendix A). The buildings with ‘high’ or ‘very high’ collapse potential include multiple public safety and education facilities located throughout the county all of which can play a key role in during disasters events or during long-‐term recovery. Please see the city addenda for a list of facilities within each jurisdiction (note: some county facilities are located within city jurisdiction, as such they are represented in the applicable addendum table).

More information on the Earthquake hazard can be found in the Earthquake section of the State of Oregon’s Natural Hazards Mitigation Plan and within the Oregon Resilience Plan.


Existing mitigation activities include current mitigation programs and activities that are being implemented by city, county, regional, state or federal agencies and/or organizations.

SchoolsEddyville(Charter(School(57(Eddville(School(Road,(Eddyville)

X X X

Public+SafetyDepoe(Bay(RFPD(6445(Gleneden(Beach(Lp,(Gleneden(Beach)

X

Siletz(RFPD(7751(Logsden(Rd,(Logsden)

X

North(Lincoln(Fire(&(Rescue(I(Kernville(Station(37625(Siletz(River(Hwy,(Lincoln(City)North(Lincoln(Fire(&(Rescue(I(Otis(Fire(Department(381(Old(Scenic(Hwy,(Otis)

X

North(Lincoln(Fire(&(Rescue(I(Rose(Lodge(5284(Salmon(River(Hwy,(Rose(Lodge)

XX

Seal(Rock(RFPD(10333(NW(Rand(St,(Seal(Rock)

X

Seal(Rock(RFPD(I(Bayshore(Station(2009(NW(Hilton(Dr,(Seal(Rock)

X

Facility

Level+of+Collapse+PotentialLow+++(<+1%)

Moderate+(>1%)

High+(>10%)

Very+High+(100%)


At an individual level, preparedness for an earthquake is minimal as perception and awareness of earthquake hazards are low. Strapping down heavy furniture, water heaters and expensive personal property as well as having earthquake insurance are steps toward earthquake mitigation.

City and county building officials enforce building codes for new construction and can coordinate inspection activities in the event of an earthquake. Lincoln County has also mapped critical facilities and major public buildings and inspections of these facilities can be assigned quickly when an earthquake occurs.

Lincoln County Public Works participates in inter-‐agency drills intended to improve capability to respond to events such as earthquakes. Once an earthquake occurs, an evaluation of roadways and bridges for damages will occur. Initial damage assessment will be logged and a plan of action developed. Life-‐line routes (arterial routes) have been identified and will receive priority. It is expected that inter-‐agency support will be critically needed.

Lincoln County bridges are inspected every two years. Bridges are inspected in accordance with National Bridge Inspection Standards (NBIS). The County uses the NBIS inspections to guide bridge maintenance work. In the event of a critical finding, emergency repair work may be initiated. Bridges found to be incapable of carrying legal loads are posted with load limits.

The Oregon State Building Codes Division adopts statewide standards for building construction that are administered by the state, cities and counties throughout Oregon. The codes apply to new construction and to the alteration of, or addition to, existing structures. Within these standards are six levels of design and engineering specifications for seismic safety that are applied to areas according to the expected degree of ground motion and site conditions. The structural code requires a site-‐specific seismic hazard report for critical facilities such as hospitals, fire and police stations, emergency response facilities, and special occupancy structures, such as schools and prisons. The seismic hazard report required by the structural code for essential facilities and special occupancy structures considers factors such as the seismic zone, soil characteristics including amplification and liquefaction potential, any known faults, and potential landslides. The findings of the seismic hazard report must be considered in the design of the building. The residential code incorporates prescriptive requirements for foundation reinforcement and framing connections based on the applicable seismic zone for the area.

Retrofitting of existing buildings may be required when such buildings are altered or their occupancy is changed. Requirements vary depending on the type and size of the alteration and whether there is a change in the use of the building that is considered more hazardous.


There are three (3) identified Earthquake action items for Lincoln County; in addition, several of the Multi-‐Hazard action items affect the earthquake hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

Lincoln County NHMP July 2015 Page FL-1

FLOOD


Causes and Characteristics of the Hazard Flooding results when rain or snowmelt creates water flow that exceed the carrying capacity of rivers, streams, channels, ditches, and other watercourses. In Oregon, flooding is most common from October through April when storms from the Pacific Ocean bring intense rainfall. Most of Oregon’s destructive natural disasters have been floods.35

Anticipating and planning for flood events is an important activity for Lincoln County. Federal programs provide insurance and funding to communities engaging in flood hazard mitigation. The Federal Emergency Management Association (FEMA) manages the National Flood Insurance Program (NFIP) and the Hazard Mitigation Grant Program (HMGP). The NFIP provides flood insurance and pays claims to policyholders who have suffered losses from floods. The HMGP provides grants to help mitigate flood hazards by elevating structures or relocating or removing them from flood hazard areas. These programs provide grant money to owners of properties who have suffered losses from floods, and in some cases, suffered losses from other natural hazard events.

Flood Sources

The principal flood sources for the unincorporated area of Lincoln County include the: Salmon River, Siletz River, Yaquina River, Alsea River, Little Elk Creek, and the Pacific Ocean. The incorporated areas of the county are affected by many of the same rivers and also the following: Alsea Bay, Big Creek, Depoe Bay, Depoe Creek/ Slough, Devils Lake, Drift Creek, Olalla Creek/ Slough, Red River, Schooner Creek, Siletz Bay, Yachats River, and Yaquina Bay.36 See the City addenda for a listing of main flood sources for each community.

35 Taylor, George H. and Chris Hannan. The Oregon Weather Book. Corvallis, OR: Oregon State University Press. 1999 36 FEMA, Lincoln County Flood Insurance Study, effective December 18, 2009, and FEMA, Risk MAP Discovery Report, January 10, 2013 (MAS-‐05-‐03).

Significant changes to this section include the addition of national flood insurance program information incorporating reporting on repetitive flood loss and severe repetitive flood loss properties. Incorporation of Risk MAP products including exposure analysis. In addition, the format of the section and minor content changes has occurred.

Page FL-2 July 2015 Lincoln County NHMP

Flood Types

The main types of flooding that occur in Lincoln County include: (1) riverine flooding, caused mostly by prolonged, high intensity rainfall events, and (2) ocean flooding from high tides and large, wind-‐driven waves.

Riverine floods

Riverine floods occur when water levels in rivers and streams overflow their banks. In Lincoln County, riverine flooding occurs primarily on lands in the five major river valleys (Alsea, Salmon, Siletz, Yachats, and Yaquina rivers) and along the larger tributaries. Most communities located along such water bodies have the potential to experience this type of flooding after spring rains, heavy thunderstorms or rapid runoff from snow melt. Riverine floods can be slow or fast-‐rising, but usually develop over a period of days.

The danger of riverine flooding occurs mainly during the winter months, with the onset of persistent, heavy rainfall, and during the spring, with melting of snow in the Cascade and Coast Ranges.

Coastal floods

Coastal flooding occurs in low-‐lying coastal areas and is caused by heavy rain, storms, large waves, and even tsunamis produced by underwater seismic events. Areas exposed to this intensive wave action are termed by FEMA as high velocity zone, or “V-‐zones”. Special regulations are usually applied in these areas.

History of Floods in Lincoln County37

Riverine flooding events with significant damage potential are relatively frequent; historically, floods with an estimated recurrence interval of 10 to 15 years have caused substantial property damage. Records for coastal flooding are mostly anecdotal, but the recurrence of damaging coastal floods has been less frequent than riverine floods.

Riverine flooding in Lincoln County typically occurs following snow accumulation in the upper reaches of watersheds in combination with southwestern storms that may bring warmer temperatures and heavy precipitation. Along the coast the high spring tides combined with storm surges produced by strong winds from winter storms often cause flooding.

In addition to the events listed below the county has received presidential disaster declarations designation for the following events that included flooding: DR 184 (1964), DR 319 (1972), DR 413 (1974), DR 1099 (1996), DR 1107 (1997), DR 1632 (2006), DR 1672 (2006), DR 1683 (2007), DR 1733 (2007), DR 1956 (2011), DR 1964 (2011, Tsunami), and DR 4055 (2012).

37 Ibid. Most of the information in this section was obtained from the FIS, additional footnotes are provided as applicable.


More information on the history of the flood hazard can be found in the Regional Risk Assessment for Region 1 of the 2015 Draft Oregon NHMP. Additional information is available in the Lincoln County Flood Insurance Study (2009), and the FEMA Risk MAP Discovery Report (2013) and Risk Report (2014, unpublished draft).

Table II-5 Flood History

Source: FEMA, Lincoln County Flood Insurance Study, effective December 18, 2009, and FEMA, Risk MAP Discovery Report, January 10, 2013 (MAS-‐05-‐03).

Hazard Identification

FEMA Flood Insurance Rate Maps (FIRMs) and the accompanying Flood Boundary and Floodway maps are the most comprehensive resource for identifying areas subject to flood hazards in Lincoln County. FIRMs and Floodway maps delineate the boundaries of areas subject to inundation by the “base flood.” The base flood is defined as an event having a 100-‐year recurrence interval or a 1% probability of occurring in any year. The maps also provide, in areas of detailed study, projected water surface elevations for the base flood. In general, based on experience with the flood events of the past two decades, Lincoln County’s FIRM maps have proven to be fairly accurate in depicting areas subject to riverine flooding. There have been no large magnitude coastal flooding events since the FIRMs were issued in 1980, so the accuracy of the maps in relation to coastal flooding is largely untested.

The special flood hazard area is depicted in the map below (the areas in red show the 0.1% annual flood risk, 100-‐year floodplain), for more detailed information visit the Oregon Risk MAP website and click on the “Mapping Tools” tab: http://www.oregonriskmap.com/. Additional maps are provided within Volume III, Jurisdictional Addenda.

Lincoln County is currently undergoing a revision of their flood study/ mapping, preliminary maps were provided in 2014 and are expected to become final in 2016. To view the draft FIS and preliminary maps contact Lincoln County planning or DOGAMI.

River Communities Record/Flood Other/Flood/Events

Salmon Unincorporated/county November/2006 No/other/records/available

Siletz Siletz,/Lincoln/City November/26,/1999

November/2006,/November/1998,/February/1996,/March/1931,/1921,/November/1909

Devlis/Lake//D/River Lincoln/City 1972 No/other/records/available

Yaquina/River Newport,/Toledo

November/16,/1973;December/1964/(Toledo)

February/1986,/January/1980,/December/1975

Alsea/River//Bay Waldport December/22,/1964

November/2006,/December/1998,/February/1996,/December/1980,/January/1974,/January/1972,/November/1960,/December/1955

Yachats/River Yachats No/records/available No/records/available

Pacific/Ocean All January/3,/19392011/(distant/tsunami),/1973,/December/1967,/February/1967,/1964,/1964/(distant/tsunami),/1960,/1952


Figure II-9 Special Flood Hazard Area

Source: Oregon HazVu: Statewide Geohazards Viewer (HazVu), accessed May 22, 2015


National Flood Insurance Program (NFIP)

The Lincoln County Flood Insurance Rate Maps (FIRMs) were modernized in December 2009. The table below shows that as of September 2014, Lincoln County (including the incorporated cities) has 2,614 National Flood Insurance Program (NFIP) policies in force (1,204 of these are for properties developed before the initial FIRM). According to data from 2012, the proportion of single-‐family homes (excluding condominiums) that have flood insurance (the market penetration rate) for Lincoln County is 38.5% (1,053 policies out of 2,734 residential properties in the SFHA). There is approximately $624 million of insurance in force within the county; and there have been 327 paid claims for a total pay out of $4.86 million.

The table displays the number of policies by building type and shows that the majority of residential structures that have flood insurance policies are single-‐family homes and that there are 129 non-‐residential structures with flood insurance policies. The last Community Assistance Visit (CAV) for Lincoln County was on April 15, 2004 (the most recent CAV was in Newport on June 29, 2006). The county, and cities, are not members of the Community Rating System (CRS).

Table II-6 Flood Insurance Detail

Source: Information compiled by Department of Land Conservation and Development, April 2015.

Flood insurance covers only the improved land, or the actual building structure. Repetitive loss structures (RL) are defined as a National Flood Insurance Program (NFIP)-‐insured structure that has had at least two paid flood losses of more than $1,000 each in any 10-‐year period since 1978. Severe repetitive loss properties (SRL) is defined as a residential property that is covered under an NFIP flood insurance property and has had at least four

Single'Family

2'to'4'Family

Other'Residential

Non7Residential

Minus'Rated'A'Zone

Minus'Rated'V'Zone

Lincoln'County ',' ',' 2,614 1,204 1,926 70 489 129 74 2County* 12/18/09 9/3/80 1,229 556 1,168 17 8 36 32 2Depoe'Bay 12/18/09 10/15/80 109 23 67 6 34 2 1 0Lincoln'City 12/18/09 4/17/78 793 477 378 20 369 26 24 0Newport 12/18/09 4/15/80 209 46 91 16 66 36 12 0Siletz 12/18/09 3/1/79 21 8 20 0 0 1 1 0Toledo 12/18/09 3/1/79 10 2 7 1 0 2 1 0Waldport 12/18/09 3/15/79 109 62 65 9 12 23 2 0Yachats 12/18/09 3/1/79 134 30 130 1 0 3 1 0

Lincoln'County '$''''624,346,700' 327 255 53 '$''''4,863,715' 44 1 ',' ','County* 319,808,200$''''' 261 201 49 3,934,949$'''' 37 1 NP 4/15/04Depoe'Bay 27,904,800$'''''' 2 0 0 5,222$'''''''''' 0 0 NP 8/20/98Lincoln'City 144,636,800$''''' 38 33 2 739,292$''''''' 4 0 NP 4/16/04Newport 57,434,300$'''''' 0 0 0 ,$''''''''''''''''' 0 0 NP 6/29/06Siletz '$''''''''3,658,400' 1 1 1 '$''''''''44,263' 0 0 NP 8/20/98Toledo 3,099,100$'''''''' 2 2 0 33,157$'''''''' 0 0 NP 2/22/00Waldport 27,034,100$'''''' 18 15 1 84,999$'''''''' 2 0 NP 3/6/01Yachats 40,771,000$'''''' 5 3 0 21,833$'''''''' 1 0 NP 3/7/01

Repetitive'Loss'Structures

Severe'Repetitive'Loss'Properties

Total'Paid'Amount

CRS'Class'Rating

Last'Community'Assistance'Visit

*'Portion'of'entire'county'under'Lincoln'County'political'jurisdiction,'NP','Not'Participating'

Pre7FIRM'Policies

EffectiveFIRM'and'FIS

InitialFIRM'Date

Total'PoliciesJurisdiction

Policies'by'Building'Type

JurisdictionInsurancein'Force

Total'Paid'Claims

Pre7FIRM'Claims'Paid

Substantial'Damage'Claims


paid flood losses of more than $5,000 each or for which at least two separate building claims payments with the cumulative amount exceeding the market value of the building. Repetitive loss structures and severe repetitive loss properties are troublesome because they continue to expose lives and valuable property to the flooding hazard. Local governments as well as federal agencies such as FEMA attempt to address losses through floodplain insurance and attempts to remove the risk from repetitive loss of properties through projects such as acquiring land and improvements, relocating homes or elevating structures. Continued repetitive loss claims from flood events lead to an increased amount of damage caused by floods, higher insurance rates, and contribute to the rising cost of taxpayer funded disaster relief for flood victims.

The community repetitive flood loss record for Lincoln Countywide identifies 44 RL properties (37 in the unincorporated areas of the county, four in Lincoln City, two in Waldport, and one in Yachats). Twenty-‐six of the RL properties are not insured and five are pending and uninsured. There have been 105 paid repetitive loss claims totaling $1.77 million. There are no repetitive loss structures within the cities of Depoe Bay, Newport, Siletz, and Toledo. There is one SRL property identified in Lincoln County; another SRL property not shown in the table has been mitigated. Substantially damaged buildings located in the Special Flood Hazard Area do not require benefit-‐cost analysis to qualify for mitigation funds.

Table II-‐7 and Figure II-‐10 provide information on the identified RL and SRL properties. The figure shows that the vast majority of RL properties are located on the Siletz River upstream from Lincoln City.


Table II-7 Repetitive and Severe Repetitive Flood Loss Detail

Source: Information compiled by Department of Land Conservation and Development, April 2015. Notes: V = Validated Severe Repetitive Loss Property, PU = Pending Uninsured Severe Repetitive Loss Structure

RFL$or$SRL$Property

General$Location Jurisdiction

Property(1 see(map UnincorporatedProperty(2 see(map UnincorporatedProperty(3 see(map UnincorporatedProperty(4 see(map UnincorporatedProperty(5 see(map UnincorporatedProperty(6 see(map UnincorporatedProperty(7 see(map UnincorporatedProperty(8 see(map UnincorporatedProperty(9 see(map UnincorporatedProperty(10 see(map UnincorporatedProperty(11 see(map UnincorporatedProperty(12 see(map UnincorporatedProperty(13 see(map UnincorporatedProperty(14 see(map UnincorporatedProperty(15 see(map UnincorporatedProperty(16 see(map UnincorporatedProperty(17 see(map UnincorporatedProperty(18 see(map UnincorporatedProperty(19 see(map UnincorporatedProperty(20 see(map UnincorporatedProperty(21 see(map UnincorporatedProperty(22 see(map UnincorporatedProperty(23 see(map UnincorporatedProperty(24 see(map UnincorporatedProperty(25 see(map UnincorporatedProperty(26 see(map UnincorporatedProperty(27 see(map UnincorporatedProperty(28 see(map UnincorporatedProperty(29 see(map UnincorporatedProperty(30 see(map UnincorporatedProperty(31 see(map UnincorporatedProperty(32 see(map UnincorporatedProperty(33 see(map UnincorporatedProperty(34 see(map UnincorporatedProperty(35 see(map UnincorporatedProperty(36 see(map UnincorporatedProperty(37 see(map UnincorporatedProperty(38 see(map Lincoln(CityProperty(39 see(map Lincoln(CityProperty(40 see(map Lincoln(CityProperty(41 see(map Lincoln(CityProperty(42 see(map WaldportProperty(43 see(map WaldportProperty(44 see(map YachatsTotal (B( (B(

InsuredFlood$Zone Occupancy

Historic$Building

Total$Paid$Claims

Total$Paid$Amount

SRL$Indicator

NO A08 SINGLE(FMLY No 3 26,113.76$((((((((( (((NO X SINGLE(FMLY No 3 10,457.57$((((((((( (((SDF A SINGLE(FMLY No 4 41,754.60$((((((((( VNO A SINGLE(FMLY No 2 55,354.37$((((((((( PUNO A SINGLE(FMLY No 2 66,702.15$((((((((( (((NO A05 SINGLE(FMLY No 2 28,227.69$((((((((( (((NO A SINGLE(FMLY No 2 15,700.00$((((((((( PUNO A SINGLE(FMLY No 3 8,324.06$((((((((((( (((NO A SINGLE(FMLY No 2 6,372.60$((((((((((( (((YES A SINGLE(FMLY No 3 18,716.77$((((((((( (((NO A09 SINGLE(FMLY No 2 14,629.49$((((((((( PUNO A SINGLE(FMLY No 2 65,623.69$((((((((( PUNO A05 NON(RESIDNT No 2 4,624.62$((((((((((( (((NO A06 SINGLE(FMLY No 2 52,693.92$((((((((( (((NO A09 SINGLE(FMLY No 2 20,015.42$((((((((( PUNO A SINGLE(FMLY No 2 59,709.07$((((((((( (((YES A08 SINGLE(FMLY No 2 2,706.80$((((((((((( (((YES A04 SINGLE(FMLY No 3 108,668.36$((((((( (((NO C SINGLE(FMLY No 2 60,636.34$((((((((( (((YES A04 SINGLE(FMLY No 2 7,566.47$((((((((((( (((NO A09 ASSMD(CONDO No 2 60,549.39$((((((((( (((NO C SINGLE(FMLY No 3 86,244.16$((((((((( (((NO B NON(RESIDNT No 2 12,184.31$((((((((( (((NO A05 ASSMD(CONDO No 2 37,106.00$((((((((( (((NO A08 SINGLE(FMLY No 2 35,428.91$((((((((( (((YES A SINGLE(FMLY No 3 111,683.83$((((((( (((YES A08 SINGLE(FMLY No 2 5,574.43$((((((((((( (((NO A09 SINGLE(FMLY No 2 8,797.16$((((((((((( (((YES A08 SINGLE(FMLY No 7 71,335.75$((((((((( (((NO A SINGLE(FMLY No 2 5,912.66$((((((((((( (((NO A SINGLE(FMLY No 2 102,348.62$((((((( (((YES A11 SINGLE(FMLY No 2 4,449.29$((((((((((( (((NO A11 SINGLE(FMLY No 3 60,290.64$((((((((( (((NO AE SINGLE(FMLY No 3 9,076.98$((((((((((( (((YES A09 SINGLE(FMLY No 2 87,110.48$((((((((( (((NO A SINGLE(FMLY No 2 9,297.27$((((((((((( (((YES A09 SINGLE(FMLY No 2 16,670.20$((((((((( (((NO C SINGLE(FMLY No 2 31,021.01$((((((((( (((YES V13 NON(RESIDNT No 2 269,509.58$((((((( (((NO A SINGLE(FMLY No 2 26,007.72$((((((((( (((NO B SINGLE(FMLY No 3 10,280.03$((((((((( (((NO AO SINGLE(FMLY No 2 23,985.74$((((((((( (((YES A02 SINGLE(FMLY No 2 6,428.74$((((((((((( (((NO AO SINGLE(FMLY No 2 5,952.54$((((((((((( ((((B( (B( (B( 0 105 1,771,843.19$((((


Figure II-10 Repetitive Loss and Severe Repetitive Loss Properties

Source: Department of Land Conservation and Development, June 2015.


Probability of Future Occurrence

Research has documented a pattern of climate variability in the Northern Pacific known as the Pacific Decadal Oscillation (PDO.) The PDO is a long-‐lived pattern of climate variability with alternating warm/dray-‐cool/wet cycles, which persist for 20-‐30 years. The predictability for this climate oscillation is not currently known but it is suggested that the riverine floods associated with high intensity precipitation events may tend to “cluster” in the decades of the cool/wet cycle of the PDO. 38

Although ocean storms can be expected every year, property damage associated with coastal flooding is rare in Lincoln County.

El Niño effects, which tend to raise ocean levels and produce higher intensity storms, occur about every three to five years.39 V zones (wave velocity zones,) depicted on FEMA’s Flood Insurance Rate Maps, are areas subject to 100-‐year flood events (i.e., 1% chance in any given year). The Flood Insurance Rate Maps also show areas vulnerable to sheet-‐flow from waves over-‐topping dunes (AO and AH zones).

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a riverine or a tidal flood is “high”, meaning one incident is likely within the next 10 – 35 year period. As can be seen from the recent history of flood events in the county, floods with recurrence intervals of 10-‐15 years, can be expected to result in moderate to substantial property damage. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.40


The Lincoln County Natural Hazards Steering Committee rated the County as having a “moderate” vulnerability to the riverine and tidal flood hazards, meaning between 1 -‐ 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.41

Low-‐lying areas along the lower portions of the County’s major rivers (Salmon, Siletz, Yaquina, Alsea, Yachats) and larger tributaries are the areas most vulnerable to flood hazards. Here, riverine flooding can be exacerbated by high tides. Also, along the lower portions of the Salmon, Siletz and Alsea Rivers, rural subdivisions and substantial recreational and second home development took place in the 1960s and 1970s, (before Lincoln County entered the National Flood Insurance Program and implemented a system of flood hazard area regulation.) As a result, there are numerous structures located in flood hazard areas

38 Mantua, Nathan. The Pacific Decadal Oscillation. University of Washington, Seattle, WA.

39 Taylor, G.H. and Hatton, R.R. The Oregon Weather Book: A State of Extremes. Oregon State University Press, Corvallis, OR. 1999


41 Ibid.


along these rivers that are classified as ‘pre-‐FIRM”, meaning their construction predates requirements to elevate above the base flood level, and are therefore subject to damage during larger flood events. The county has worked actively, mostly along the Siletz River (Lower Siletz Mitigation Project,) to assist property owners in retrofitting many of these pre-‐FIRM residences to meet current elevation requirements. This project has been a success for both homeowners and the government agencies that assisted. Having these homes elevated and out of harm’s way will certainly reduce the amount of property losses as well as insurance payments in the future. There are still, however, substantial numbers of structures in harm’s way in these areas.

Also, some areas along major rivers, highways and roads, in particular Highway 229 along the lower Siletz River, are subject to inundation and damage by flood waters. Highway 229 was flooded and therefore closed as recently as November 2006.

In general, the following are subject to damage by riverine flooding:

• Pre-‐FIRM residential structures, especially repetitive loss structures/properties as shown in Table II-‐6, II-‐7, and Figure II-‐9.

• Manufactured homes inside manufactured home parks

• Roads and highways

The primary economic activities at risk from riverine flood events include:

• RV park and campground operations

• Other businesses that rely on road and highway transportation corridors that may be interrupted by flooding.

There are no known critical facilities located within identified flood hazard areas in Lincoln County.

Coastal developments within FEMA-‐designated Velocity (V) zones and A-‐O zones include the Bayshore development on Alsea spit and the Salishan development on the Siletz spit. The majority of residences in both developments are post-‐FIRM, meaning that they are built in compliance with current flood hazard area regulations. There has been no record of significant damage from flooding in either of these areas.

Table II-‐8 below shows the real market value exposure analysis for the unincorporated areas and communities within the Risk Report study area (Figure II-‐11); see Volume III, Jurisdictional Addenda, for real market value exposure analysis for the incorporated cities.


Figure II-11 Risk Report Study Area Communities

Source: DOGAMI exposure analysis using tax lot data and Risk MAP depth grids, Lincoln County Risk Report (2014, unpublished draft)

Table II-‐8 summarizes the amount of real market value (RMV) exposed to the 1% and 0.2% flood hazard recurrence intervals within the unincorporated areas of the county within the study area (Figure II-‐10). The data shows that there are 414 buildings exposed to the 1% flood recurrence interval (riverine and coastal) with a total value of $55.9 million and an exposure ratio of 8.82%. The table also shows that there are 181 buildings exposed to the 0.2% riverine flood recurrence interval with a total value of $6.1 million and an exposure ratio of 0.96%.


Table II-8 Actual Exposure of RMV for 1% and 0.2% Flood Scenarios

Source: DOGAMI exposure analysis using tax lot data and Risk MAP depth grids, Lincoln County Risk Report (2014, unpublished draft) Note 1: The 1% flood zone is a combination of the riverine and coastal 1% flood zones. The 0.2% flood zone is inclusive of the riverine 1% flood zone. Note 2: The 1% exposure is the only recurrence interval that includes coastal flooding zones. Note 3: Total RMV -‐ $633,814,705 for 7,400 buildings (does not include data for Otter Rock and Beverly Beach) Note 4: Coastal High Hazard Zone outside of flood depth grid. The Risk Report (2014, unpublished draft) conducted an exposure analysis for the purposes of estimating the number of buildings that are vulnerable to damage from either riverine or coastal flooding. Based on this inventory it is estimated that there are a total of 2,275 buildings located within a special flood hazard area inundated by riverine and coastal 100-‐year floods (1% chance flood, SFHA). The data shows that 8.7% of buildings in the county are within a SFHA; 7.2% of buildings within unincorporated communities and 9.3% of buildings within incorporated cities. The unincorporated communities of Otis and Wakonda Beach are particularly vulnerable with 12.7% and 11.4% of their buildings, respectively. Among incorporated communities Toledo has the largest percentage of its buildings in a regulated flood hazard area (29.0%); Siletz (11.1%), and Waldport (21.6%) also have significant percentages. Lincoln City has the largest number of buildings within the SFHA (656).

Table II-‐6 (above) summarizes flood insurance policy coverage and claims information for Lincoln County and its incorporated cities, while Table II-‐9 (below) shows the building exposure within the various SFHA recurrence intervals and provides the number of NFIP policies by jurisdiction (information is aggregated for county unincorporated areas. As can be seen from this data, the number of flood insurance policies in effect is sometimes lower, and at other times greater, than the number of buildings present in the SFHA. Though many improved properties may include more than one building, it is still apparent that there are buildings (residential and non-‐residential) located in flood hazard areas that are not covered by flood insurance. Within the study area communities (Figure II-‐9) 5.3% of buildings are exposed to 100-‐year flood recurrence interval; there are 1,229 policies in the county unincorporated (including policies for property outside of the Risk Report study area). Claims history indicates that flood hazard areas in the unincorporated county are those with the greatest exposure to flood damage (Table II-‐6 and Figure II-‐9). The percent of buildings with insurance within the incorporated cities (7.5%) is approximately equal to the percent of buildings that are exposed (7.3%); however, according to the Risk Report data and the NFIP policy information the policies and the exposed buildings do not necessarily coincide with each other. The discrepancy between the percent of buildings exposed and the percent with

RMV$Exposed #$BuildingsExposure$Ratio RMV$Exposed #$Buildings

ExposureRatio

All#exposed#Buidlings $55,905,017# 414 8.82% $6,084,536# 181 0.96%

0=3#Ft#Flood#Exposue $27,607,450# 268 4.36% $5,519,127# 150 0.87%

3=6#Ft#Flood#Exposue $7,584,692# 44 1.20% $564,638# 28 0.09%

>6#Ft#Flood#Exposue $6,510,440# 28 1.03% $771# 3 0.00%

Coastal#High#Hazard $14,202,435# 74 2.24% $0# 0 0.00%

1%$(100:year) 0.2%$(500:year)


insurance is greatest in Toledo, Siletz, and Waldport; while Depoe Bay, Newport, and Yachats appear to have more policies than buildings that are exposed.

Updated risk assessment information will be provided as part of the Risk Report in 2016, which will be updated to include Hazus loss estimation for all areas of the county. See NFIP section (above and in Risk Assessment) for residential insurance market penetration information.

Table II-9 Building Exposure for Flood Scenarios and Percent Insured

Source: DOGAMI exposure analysis using tax lot data and Risk MAP depth grids, Lincoln County Risk Report (2014, unpublished draft); NFIP Information compiled by Department of Land Conservation and Development, April 2015. Note 1: The exposed buildings in each flood zone are inclusive of the buildings in the lower zones. Note 2: The 1% exposure is the only recurrence interval that includes coastal flooding zones. ^ = The unincorporated county area includes all unincorporated land outside of rural communities. As shown in Figure II-‐X this area was not included in the Risk Report study area. n/a = data not available for this area. 0 = There is no exposure for this flood zone. * = Data for this area was not available/ modeled ** = Because unincorporated land outside of the study area was not included this value undercounts by about half the total number of buildings within the unincorporated areas of the county. The Risk MAP Hazus analysis to be complete in 2015 will include all unincorporated area.

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I, Section 2) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the Riverine Flood hazard is rated #7, out of 13 rated hazards, with a total score of 180; the Coastal Flood hazard is rated #10, out of 13 rated hazards, with a total score of 160.

Buildings10%(10-yr)

2%(503yr)

1%(1003yr)

0.2%(5003yr)

Gleneden&Beach,&Lincoln&Beach 2,475 6 10 104 4.2% 10 n/a n/aOna&Beach,&Seal&Rock,&Bayshore 2,004 * * 80 4.0% &B& n/a n/aOtter&Rock,&Beverly&Beach 420 * * 0 0.0% &B& n/a n/aOtis 2,100 30 100 136 6.5% 171 n/a n/aWakonda&Beach 821 * * 94 11.4% &B n/a n/aUnincorporated&County^ n/a n/a n/a n/a n/a n/a n/a

Unincorporated,Total** 7,820 36 110 414 5.3% 181 1,229 n/aDepoe&Bay 1,116 1 2 18 1.6% 3 109 9.8%Lincoln&City 6,645 2 2 656 9.9% 2 793 11.9%Newport 5,693 6 10 41 0.7% 13 209 3.7%Siletz 611 1 21 46 7.5% 51 21 3.4%Toledo 1,883 134 194 218 11.6% 240 10 0.5%Waldport 1,608 * * 348 21.6% &B& 109 6.8%Yachats 862 0 0 15 1.7% 26 134 15.5%

Incorporated,Total 18,418 144 229 1,342 7.3% 335 1,385 7.5%Total 26,238 180 339 1,756 6.7% 516 2,614 10.0%

PercentBuildings-Exposed

Percent-with-

InsuranceNFIP-

Policies

Buildings-Exposed-in-SFHA


Community Hazard Issues The extent of the damage and risk to people caused by flood events is primarily dependent on the depth and velocity of floodwaters. Fast moving floodwaters can wash buildings off their foundations and sweep vehicles downstream. Roads, bridges, other infrastructure and lifelines (pipelines, utility, water, sewer, communications systems, etc.) can be seriously damaged when high water combines with flood debris, mud and ice. Extensive flood damage to residences and other structures also results from basement flooding and landslide damage related to soil saturation. Surface water entering into crawlspaces, basements and daylight basements is common during flood events not only in or near flooded areas but also on hillsides and other areas far removed from floodplains. Most damage is caused by water saturating materials susceptible to loss (e.g., wood, insulation, wallboard, fabric, furnishings, floor coverings and appliances.)

If not properly protected from the entry of flood waters, mechanical, electrical and similar equipment can also be damaged or destroyed by flooding.

Older, pre-‐FIRM manufactured homes are particularly susceptible to flood damage, as many have a lower level of structural stability than “stick-‐built” (standard wood frame construction) homes. Current regulations require manufactured homes in floodplain zones to be both elevated and anchored to provide structural stability during flood events comparable to site built homes.

Flood events impact businesses by damaging property and interrupting commerce. Flood events can cut off customer access and close businesses for repairs. A quick response to the needs of businesses affected by flood events can help a community maintain economic viability in the face of flood damage.

Bridges are a major concern during flood events as they provide critical links in road networks by crossing water courses and other significant natural features. However bridges and their supporting structures can also be obstructions in flood-‐swollen watercourses and can be damaged by debris jams and erosion scour.


Lincoln County has actively pursued several flood Authorities, Policies, Programs, and Resources in an effort to reduce vulnerability to damage and disruption from flooding events.

Current initiatives to mitigate the effects of potential flooding in Lincoln County are many. These actions are varied from projects initiated by homeowners and neighborhood associations to county policies and procedures aligned with the National Flood Insurance Program.

Home and business owners and neighborhood associations in and around the County’s floodplains continue to address mitigation activities for flooding. Riparian zones have been established to reduce erosion, review of building plans/codes and emergency strategies to mitigate damage from floods are being developed.


Lincoln County Comprehensive Plan and Land Use Code

Lincoln County has enacted a Comprehensive Land Use Plan and is implementing land use regulations in compliance with ORS 197 and the Statewide Planning Goals. The County has enacted and enforces a flood hazard area overlay zone, which is applied to all areas mapped as subject to inundation by the base flood. The regulations are designed to reduce the risk of flood damage to new and substantially improved structures within known flood hazard areas.

Lincoln County Public Works

Lincoln County annually, using the culvert inventory, visually inspects and cleans culverts on county roads. Culverts needing replaced are identified and targeted for replacement. Culverts during past flooding events that could not handle the flow are looked at for replacement with a larger culvert.

Bridges are inspected by an outside consulting firm every two years. Lincoln County inspects bridges every six months. During flood events crews keep a visual check on bridges for drift buildup. After a major flood, crews are dispatched to recheck bridges for flood damage.

Digitized Flood Insurance Rate Map

As part of the development of the County’s Land Information System (LIS), the County has completed the digitizing of the Flood Insurance Rate Maps (FIRM) and the Flood Boundary and Floodway maps. This digital layer can now be applied in conjunction with the County’s digital tax lot layer to more readily identify individual properties and structures in relation to the mapped flood hazard area boundaries. It should be noted that this digital layer has no official statues for regulatory or insurance purposes; the FIRMs are the officially adopted maps for these purposes. And, since the original source of this digital layer (the FIRMs) was produced at a large scale and low level of detail, the overlay of this information on the County’s more geodetically accurate tax lot layer must be viewed as an approximation of the flood hazard area boundary. Nonetheless, this information has proven to be a very useful tool in assisting planners and property owners in generally identifying flood prone properties, and especially in identifying areas where more detailed field reconnaissance (e.g. elevation survey) is needed. Updated FIRMs were completed in 2014 and preliminary maps were provided to Lincoln County; these maps will eventually become the regulatory maps for the County (expected in 2016). Digital data was also provided to the County with the release of the preliminary maps.

Emergency Services Notification

Lincoln County Emergency Services maintains a phone list for selected owners and residents of properties in flood hazard areas along the County’s major rivers. In most cases, these contacts are for residents and owners of homes in the lowest elevation portions of the flood plain, and thus the first to be threatened in the event of a flood. When a flood event is predicted, Emergency Services makes contact with these affected homeowners and advises them of the forecasted conditions. These owners participate in a phone tree, and make additional calls within their neighborhood to advise other property owners of the probable timing and extent of flooding in their area. Throughout a flood event, Emergency Services


maintains contact with these selected owners and residents as they monitor current and forecasted conditions.

Lower Siletz Flood Mitigation Project

In 1999, the County launched an effort to reduce future flood damages along the lower Siletz River. Utilizing funding provided through FEMA’s Hazard Mitigation Grant Program (HMGP) and Flood Mitigation Assistance (FMA) grant program, the Lincoln County Planning and Development Department developed the Lower Siletz Basin Flood Mitigation Action Plan (2000.) Plan implementation activities, also using HMGP and FMA funding, were undertaken by the Planning and Development Department over the following two years. This work focused primarily on providing funding and technical assistance to property owners for elevating or removing existing pre-‐FIRM structures. In all, 59 residential structures within the project area were mitigated through elevation or removal, including 31 (out of a total of 44) repetitive loss properties. In total, an estimated $1.68 million was invested in mitigation within the project area, which represented a combination of grant funds, ICC insurance settlements, and private funds.

National Flood Insurance Program

Lincoln County participates in the National Flood Insurance Program, which enables property and business owners to qualify for federally underwritten flood insurance. Flood insurance policies in effect in the County and the coverage provided by these policies are depicted in Table II-‐6. The County’s flood hazard area overlay zone comprises the county’s NFIP qualifying flood plain regulation. These standards require all new development to be elevated above the projected level of the base flood, along with a number of other building design and construction standards intended to reduce the risk of flood damage. In several regards, the County’s flood hazard area development regulations exceed minimum NFIP standards. Strict enforcement of these regulations is required to maintain eligibility for participation in the NFIP; the Lincoln County Department of Planning and Development is charged with this responsibility.

Hazard Mitigation Action Items There are five (5) identified Flood action items for Lincoln County; in addition, several of the Multi-‐Hazard action items affect the Flood hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

Lincoln County NHMP July 2015 Page LS-1

LANDSLIDE


Causes and Characteristics of the Hazard Landslides are a major geologic threat in almost every state in the United States. In Oregon, a significant number of locations are at risk from dangerous landslides and debris flows. While not all landslides result in property damage, many landslides do pose serious risk to people and property. Increasing population in Oregon and the resultant growth in home ownership has caused the siting of more development in or near landslide areas. Often these areas are highly desirable to prospective homeowners owing to their location along the coast, rivers and on hillsides.

Landslides are fairly common, naturally occurring events in various parts of Oregon. In simplest terms, a landslide is any detached mass of soil, rock, or debris that falls, slides or flows down a slope or a stream channel. Landslides are classified according to the type and rate of movement and the type of materials that are transported.

In a landslide, two forces are at work: 1) the driving forces that cause the material to move down slope, and 2) the friction forces and strength of materials that act to retard the movement and stabilize the slope. When the driving forces exceed the resisting forces, a landslide occurs.

Landslides can be grouped as “on-‐site” and “off-‐site” hazards. An “on-‐site” slide is one that occurs on or near a development site and is usually relatively slow moving. Slow moving slides cause the most property damage in developed areas. On-‐site landslide hazards include features called slumps, earthflows and block slides. “Off-‐site” slides typically are rapidly moving and begin on steep slopes at a distance from homes and development. A 1996 “off-‐site” slide in southern Oregon began a long distance away from homes and roads, traveled at a high velocity and resulted in five fatalities and a number of injuries, in addition to substantial property damage.

Landslides are classified based on causal factors and conditions and exist in three basic categories.

Falls

This type of landslide involves the movement of rock and soil which detaches from a steep slope or cliff and falls through the air and/or bounces or rolls down the slope. This type of slide is termed a rock fall and is very common along Oregon highways where they have been cut through bedrock in steep canyons and along the coast.

There are no significant changes in the potential for Landslide to occur in Lincoln County since 2009. However, additional information regarding the hazard as reported in DOGAMI Open-‐File Report OFR O-‐04-‐09 (2004) is included in this update. In addition, minor changes to the format of the section have occurred.

Page LS-2 July 2015 Lincoln County NHMP

Slides

This type of landslide exists where the slide material moves in contact with the underlying surface. Here the slide moves along a plane and either slumps by moving along a curved surface (called a rotational slide) or along a flat surface (called a translational slide). While slow-‐moving slides can occur on relatively gentle slopes and are less likely to cause serious injuries or fatalities, they can result in significant property damages.

Flows

Flow landslides are characterized as plastic or liquid in nature where the slide material breaks up and flows during movement. A flow occurs when a landslide moves down slope as a semi-‐fluid mass scouring or partially scouring rock and soils from the slope along its path. A flow landslide is typically rapidly moving and tends to increase in volume as it moves down slope and scours out its channel.

Rapidly moving flow landslides are often referred to a debris flows. Other terms given to debris flows are mudslides, mudflows, or debris avalanches. Debris flows frequently take place during or following an intense rainfall event on previously saturated soil. Debris flows usually start on steep hillsides as slumps or slides that liquefy, accelerate to speeds as high as 35 miles per hour or more, and travel down slopes and channels onto gentle sloping or flat ground. Most slopes steeper than 70 percent are risk from debris flows.

The consistency of a debris flow ranges from watery mud to thick, rocky, mud-‐like, wet cement which is dense enough to carry boulders, trees and cars. Separate debris flows from different starting points sometimes combine in canyons and channels where their destructive energy is greatly increased. Debris flows are difficult for people to outrun or escape from and present the greatest risk to human life. Debris flows have caused most of their damage in rural areas and were responsible for most of landslide-‐related deaths and injuries during the 1996 storm in Oregon.

Conditions Affecting Landslides

Natural conditions and human activities can both play a role in causing landslides. Certain geologic formations are more susceptible to landslides than others. Locations with steep slopes are at the greatest risk of slides. However, the incidence of landslides and their impact on people and property can be accelerated by development. Developers who are uninformed about geologic conditions and processes may create conditions that can increase the risk of or even trigger landslides.

There are four principal factors that affect or increase the likelihood of landslides:

• Natural conditions and processes including the geology of the site, rainfall, wave and water action and seismic tremors, including earthquakes and volcanic activity.

• Excavation and grading on sloping ground for homes, roads and other structures.

• Drainage and groundwater alterations that are natural or human-‐caused can trigger landslides. Human activities that may cause slides include broken or leaking water or sewer lines, water retention facilities, irrigation and stream


alterations, ineffective storm water management and excess runoff due to increased impervious surfaces.

• Change or removal of vegetation on very steep slopes due to timber harvesting, land clearing and wildfire.

History of the Hazard in Lincoln County Landslides accompany almost every major storm system that impacts western Oregon. Although most landslides occur in the undeveloped forested areas of the county, landslides have also occurred in more developed areas. In recent history, particularly noteworthy landslides accompanied storms in 1964, 1966, 1982, and 1996. A major winter storm in November 1996 produced more than 9,500 landslides throughout western Oregon, including Lincoln County. More recently, similar winter storm events have resulted in significant slide damages in Lincoln County, including closures of Highway 101 at Cape Perpetua and Cape Foulweather, on Highway 18, and on old Highway 101, which lost a bridge. This isolation due to highway failures became problematic for business and commerce as well as for emergency response vehicles. Private property damage due to landslides has also occurred in recent years, including damage to a restaurant in Toledo, the destruction of a house on the Yaquina Bay Road near Newport, and damage to homes and streets at the west end of NW 57th Street in Newport. Most recently, heavy rains in November 2006 triggered a 17-‐18 acre landslide near Immonen Road, a county road located in the northern portion of the county. This slide continues to be active and has caused extensive damage to the county road.

Numerous slow moving slides affect portions of Highway 101 along the coast, including the very large Johnson Creek slide just south of Cape Foulweather.


The Johnson Creek landslide, as seen in Figure II-‐12, is located along the Oregon coast south of Cape Foulweather and is a result of coastal processes. The landslide has a long history of impacting U.S. Highway 101, which passes over the middle section of the slide. The slide is up to 26 m thick, 200 m long, and 360 m wide. Total movement of the slide, as estimated from geologic cross-‐sections, is 28 m horizontally and 6 m vertically. The most recent significant movement of the slide occurred in early 2002, when it moved approximately 25 cm horizontally and several centimeters vertically.42

Figure II-12: Johnson Creek Landslide on Highway 101

Source: DOGAMI, Johnson Creek Slide Project

DOGAMI maps the State Landslide Information Layer for Oregon (SLIDO); Figure II-‐13 relies on the 2012 SLIDO data and shows Lincoln County landslides that have been identified on published maps. The database contains only landslides that have been located on these maps. Many landslides have not yet been located or are not on these maps and therefore are not in this database. This database does not contain information about relative hazards43 The map shows that the history of landslide events is high and distributed throughout the county, and where they do occur they are in non-‐populated areas.

42 USGS. March, 16, 2007. Johnson Creek Landslide. http://landslides.usgs.gov/monitoring/johnson_creek/

43 DOGAMI. Statewide Landslide Information Database for Oregon (SLIDO-‐2). http://www.oregongeology.org/sub/slido/index.htm


Figure II-13 Mapped Landslides

Source: DOGAMI Statewide Lanslide Information Layer for Oregon (SLIDO), accessed June 15, 2015



Geologic and geographic factors are important in identifying landslide-‐prone areas. Stream channels, for example, have major influences on landslides, due to undercutting of slopes by stream erosion and long-‐term hillside processes.

The Oregon Department of Forestry (ODF) Storm Impacts Study conducted after the 1996-‐97 landslide events, found that the highest probability for the initiation of shallow, rapidly moving landslides was on slopes of 70 to 80 percent steepness. A moderate hazard of shallow rapid landslide initiation can exist on slopes between 50 and 70 percent.

In general, areas at risk to landslides have steep slopes (25 percent or greater,) and/or a history of nearby landslides. In otherwise gently sloped areas, landslides can occur along steep river and creek banks, and along ocean bluff faces. At natural slopes under 30 percent, most landslide hazards are related to excavation and drainage practices, or the reactivation of preexisting landslide hazards.

The Oregon Department of Geology and Mineral Industries (DOGAMI) is active in developing maps and collecting data on hazard risk. DOGAMI publications addressing the identification of areas subject to landslide hazard for Lincoln County include Environmental Geology of Lincoln County (Bulletin 81, 1973), LIDAR Data and Landslide Inventory Maps of the North Fork Siuslaw River and Big Elk Creek Watersheds, Lane, Lincoln, and Benton Counties, Oregon (Open Fire Report O-‐12-‐07), and Evaluation of Coastal Erosion Hazard Zones in Lincoln County, Oregon (Open File Reports 0-‐04-‐01 and 0-‐07-‐01). More information can be found on landslide mapping via DOGAMI Special Paper 42 Protocol for Inventory Mapping of Landslide Deposits from Light Detection and Ranging (LIDAR) Imagery.

In addition, as part of the Lincoln County Comprehensive Plan, hazards along the developed coastal area were identified and mapped in Environmental Hazard Inventory of Coastal Lincoln County, RNKR Associates, 1978. Hazard areas may also be determined by other means including site specific geotechnical reports. Maps included in the RNKR study are part of the Lincoln County Comprehensive Plan Inventory and are available at the Department of Planning and Development.


The probability of rapidly moving landslides occurring depends on a number of factors; these include steepness of slope, slope materials, local geology, vegetative cover, human activity, and water. There is a strong correlation between intensive winter rainstorms and the occurrence of rapidly moving landslides (debris flows); consequently, the Oregon Department of Forestry tracks storms during the rainy season, monitors rain gages and snow melt, and issues warnings as conditions warrant. Given the correlation between precipitation / snow melt and rapidly moving landslides, it would be feasible to construct a probability curve. Many slower moving slides present in developed areas have been identified and mapped; however the probability and timing of their movement is difficult to quantify. The installation of slope indicators or the use of more advanced measuring techniques could provide information on these slower moving slides.


Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a landslide is “high,” meaning at least one incident is likely within the next 25 year period. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.44


To a large degree, landslides are very difficult to predict. Both location and extent of landslide hazard are affected by a variety of variables. Many people are unaware of their exposure to landslide risk. Therefore there are a large number of structures, infrastructure, and other community assets within Lincoln County potentially vulnerable to landslides. New private development is subject to regulations which are intended to reduce risk from known landslide hazards. However, there is substantial private development in the county which pre-‐dates land use or building code regulations and is therefore subject to increased risk.

Landslides contribute a large amount of infrastructure damage on an annual basis. Given the widespread nature of the landslide hazard throughout the county, roads, drainage facilities and other public facilities are often, of necessity, located in areas subject to landslide hazards.

The Lincoln County Natural Hazards Steering Committee rated the County as having a “moderate” vulnerability to landslide hazards; meaning that between 1 -‐ 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.45

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the landslide hazard is rated #6, out of 13 rated hazards, with a total score of 195.

Community Hazard Issues Depending upon the type, location, severity and area affected, severe property damage, injuries and loss of life can be caused by landslide hazards. Landslides can damage or temporarily disrupt utility services, roads and other transportation systems and critical lifeline services such as police, fire, medical, utility and communication systems, and emergency response. In additional to the immediate damage and loss of services, serious


45 Ibid.


disruption of roads, infrastructure and critical facilities and services may also have longer term impacts on the economy of the community and surrounding area.

Increasing the risk to people and property from the effects of landslides are the following five factors:

• Improper excavation practices, sometimes aggravated by drainage issues, can reduce the stability of otherwise stable slopes.

• Allowing development on or adjacent to existing landslides or known landslide-‐prone areas raises the risk of future slides regardless of excavation and drainage practices. Homeowners and developers should understand that in many potential landslide settings that there are no development practices that can completely assure slope stability from future slide events.

• Building on fairly gentle slopes can still be subject to landslides that begin a long distance away from the development. Sites at greatest risk are those situated against the base of very steep slopes, in confined stream channels (small canyons), and on fans (rises) at the mouth of these confined channels. Home siting practices do not cause these landslides, but rather put residents and property at risk of landslide impacts. In these cases, the simplest way to avoid such potential effects is to locate development out of the impact area, or construct debris flow diversions for the structures that are at risk.

• Certain forest practices can contribute to increased risk of landslides. Forest practices may alter the physical landscape and its vegetation, which can affect the stability of steep slopes. Physical alterations can include slope steepening, slope-‐water effects, and changes in soil strength. Of all forest management activities, roads have the greatest effects on slope stability, although changing road construction and maintenance practices are reducing the effects of forest roads on landslides.

• Lincoln County is susceptible to extreme winter storms and rainfall. High rainfall accumulation in a short period of time increases the probability of landslide. An extreme winter storm can produce up to 6 inches of rainfall in a 24 hour period; if the storm occurs well in into the winter season, when the ground is already saturated, the hydraulic overload effect is heightened.


Oregon Department of Forestry (ODF)

The Oregon Department of Forestry has provided a preliminary indication of debris flows (rapidly moving landslides) in Western Oregon. Their debris flow maps include locations subject to naturally occurring debris flows and include the initiation sites and locations along the paths of potential debris flows (confined stream channels and locations below steep slopes). These maps neither consider the effects of management-‐related slope alterations (drainage and excavation) that can increase the hazard, nor do they consider very large landslides that could possibly be triggered by volcanic or earthquake activity. Areas


identified in these maps are not to be considered “further review areas” as defined by Senate Bill 12 (1999).46 Information used to develop the ODF Debris Flow maps include:

• Digital elevation models at 30-‐meter resolution, based on U.S. Geological Survey data, were used to derive slope steepness and then to develop polygons for assigned hazards. Note that actual slopes are steeper than these digitally elevated models.

• Mapped locations of Tyee soil formation and similar sedimentary geologic units. • Oregon Department of Forestry Storm Impacts and Landslides of 1996 study; debris

flow initiation and path location data. • Stream channel confinement near steep hill slopes based on U.S. Geological Survey

Digital Raster Graphics. • Historical information on debris flow occurrence in western Oregon (from Oregon

Dept. of Forestry, U.S. Forest Service, DOGAMI, Bureau of Land Management, and the Oregon Department of Transportation).

• Fan-‐shaped land formations below long, steep slopes. • Areas of highest intensity precipitation do not appear to be correlated with known

areas of high and extreme debris flow hazard, so precipitation intensity was not used to develop risk (hazard) ratings.47

Oregon Department of Geology and Mineral Industries (DOGAMI)

As previously noted, DOGAMI has engaged in an extensive program to identify and measure the extent of landslides in Oregon. Several DOGAMI publications specific to Lincoln County provide information and mapping of landslide areas. These maps are available at the Lincoln County Planning and Development Department and are often referenced by prospective home buyers and builders, and are also used in the administration of hazard area regulations.

Debris Flow Warning System

The debris flow warning system was initiated in 1997 and involves collaboration between the Department of Forestry, DOGAMI, the Department of Transportation, local law enforcement, and National Oceanic and Atmospheric Administration (NOAA) Weather Radio and other media.

Since 2008, ODF meteorologists have not issued Debris Flow Warning for Oregon since they do not have sufficient resources. However, information is provided by the National Weather Service (NWS) and broadcast via the NOAA Weather Radio, and on the Law Enforcement Data System. The information provided does not include the Debris Flow Warning system as originally designed since the NWS does not have the geologic and geomorphology expertise. Instead they provide the following language in their flood watches that highlights the potential for landslides and debris flows48:

46 Western Oregon Debris Flow Hazard Maps: Methodology and Guidance for Map Use. (1999). 47 Ibid. 48 NOAA, NWS. Letter dated December 20, 2010 from Stephen K. Todd, Meteorologist-‐in-‐Charge.


A flood watch means there is a potential for flooding based on current forecasts. Landslides and debris flows are possible during this flood event. People, structures and roads located below steep slopes, in canyons and near the mouths of canyons may be at serious risk from rapidly moving landslides.

DOGAMI provides additional information on debris flows through the media. The Department of Transportation provides warning signs to motorists in landslide prone areas during high-‐risk periods.49

Landslide Brochure

The Department of Geology and Mineral Industries (DOGAMI) developed a landslide public outreach brochure in cooperation with several other state agencies. Forty thousand copies were printed in November 1997 and were distributed widely through building code officials, county planners, local emergency managers, natural resource agency field offices, banks, real estate companies, insurance companies, and other outlets. Landslide brochures are available from DOGAMI, the Office of Emergency Management (OEM), Oregon Department of Forestry (ODF), and the Department of Land Conservation and Development (DLCD).50

Oregon State Building Code Standards

The Oregon Building Codes Division adopts statewide standards for building construction that are administered by the state and local municipalities throughout Oregon. The One-‐ and Two-‐Family Dwelling Code and the Structural Specialty Code contain provisions for lot grading and site preparation for the construction of building foundations.

Both codes contain requirements for cut, fill and sloping of the lot in relationship to the location of the foundation. There are also building setback requirements from the top and bottom of slopes. The codes specify foundation design requirements to accommodate the type of soils, the soil bearing pressure, and the compaction and lateral loads from soil and ground water on sloped lots. The building official has the authority to require a soils analysis for any project where it appears the site conditions do not meet the requirements of the code, or that special design considerations must be taken. ORS 455.447 and the Structural Code require a seismic site hazard report for projects that include essential facilities such as hospitals, fire and police stations and emergency response facilities, and special occupancy structures, such as large schools and prisons. This report includes consideration of any potentially unstable soils and landslides.51

49 Interagency Hazard Mitigation Team. 2012. Oregon Natural Hazards Mitigation Plan. Salem, OR: Oregon Military Department – Office of Emergency Management

50 Ibid.

51 Planning for Natural Hazards: Oregon Technical Resource Guide. Community Planning Workshop. (July 2000). Chapter 5.


Lincoln County Land Use Planning

Lincoln County addresses development in areas subject to geologic hazards Section 1.1925 of the Lincoln County Code. This section outlines standards for development in identified landslide areas, including requiring site specific engineering geologic reports.


Lincoln County Public Works Department monitors areas in the county road system susceptible to landslide. Where feasible, the department will attempt to stabilize failing slopes with the use of rip rap, jersey barriers or other appropriate means. Likewise, trees within a slide area that are determined to be hazardous are removed. Once stable, hydro-‐seeding occurs to restart vegetation growth.

As noted, landslides usually occur during high precipitation events. Maintenance of culverts and other components of drainage systems are critical in preventing slope and road bed failures, and are monitored closely during storm events.

In the case of large landslides, such as the one that occurred on Immonen Road in the fall of 2006, the Public Works Department attempts keep the road open to vehicular traffic. If this is not possible, the department attempts to provide a detour route. Large landslides generally can not be “fixed.” As they stabilize over time, the department makes repairs to the road. Large, stable landslides are monitored for new movement.


There are three (3) identified Landslide action items for Lincoln County; in addition, several of the Multi-‐Hazard action items affect the Landslide hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV. To view city actions see the appropriate city addendum within Volume III.

Lincoln County NHMP July 2015 Page TS-1

TSUNAMI


Causes and Characteristics of the Hazard A tsunami generally begins as a single wave but quickly evolves into a series of ocean waves, generated by disturbances from earthquakes, underwater volcanic eruptions, or landslides (includes landslides that start below the water surface and landslides that enter a deep body of water from above the water surface). In these cases the initial tsunami wave mimics the shape and size of the sea floor deformation that causes it.

The wavelength of a tsunami generated by sea floor deformation may be 100 miles or more in the deep ocean, with a wave height of only a few feet or less. These waves may reach speeds of up to 500 m.p.h. As tsunamis approach land where the water depth decreases, the forward speed of the tsunami will slow, but wave heights increase to as much as 100 feet. For simplicity, tsunamis can be divided geographically into two categories: those of distant origin and those generated locally. The distant tsunami is one that is usually generated by a subduction zone earthquake elsewhere in the Pacific and would take up to 24 hours to reach the Oregon coastline. A local tsunami is generated by a subduction earthquake off the Oregon Coast and would take minutes to reach the Oregon coastline. The Oregon Coast has experienced both types.52

A tsunami from a local source will probably be stronger, higher and travel farther inland (overland and up river) than a distant tsunami. The tsunami wave may be traveling at 30 mph when it hits the coastline and have heights of 20 to 60 feet, potentially higher depending on the coastal bathymetry (water depths) and geometry (shoreline features). The tsunami wave from a nearby earthquake will break up into a series of waves that will continue to strike the coast over an 8 to 10 hour period. Tsunami activity can continue even longer for a major Pacific-‐wide tsunami. The first wave is not always the most destructive; for example, some computer simulations for the Central Oregon Coast, show that waves arriving in the second or third hour may be as big or bigger than the initial wave. The deep ocean trenches off the coasts of Alaska, Japan, and South America are known for their underwater subduction zone earthquakes and are the source of many tsunamis.

The Pacific Northwest is located at a convergent plate boundary, where the Juan de Fuca and North American tectonic plates meet. The two plates are converging at a rate of about 1-‐2

52 State of Oregon Emergency Management Plan. Natural Hazards Mitigation Plan: Tsunami. 2002

There are no significant changes in the potential for Tsunami to occur in Lincoln County since 2009. However, additional information regarding the hazard is included in this update in relation to enhanced mapping and assessments of the hazard. In addition, minor changes to the format of the section have occurred.

Page TS-2 July 2015 Lincoln County NHMP

inches per year. This boundary is called the Cascadia Subduction Zone. It extends from British Columbia to northern California. Subduction zone earthquakes are caused by the abrupt release of slowly accumulated stress. Subduction zones similar to the Cascadia Subduction Zone have produced earthquakes with magnitudes of 8 or larger. Historic subduction zone earthquakes include the 1960 Chile (magnitude 9.5) and 1964 southern Alaska (magnitude 9.2) earthquakes. These types of earthquakes have been known to produce tsunamis.

Tsunami destruction can come from both the tsunami wave and from the rapid retreat of the water from the coastline. Tsunami waves tend to be fast moving rising surges of water. As a tsunami wave enters coastal bays and rivers, it may move as a high velocity current or a breaking wave that travels up an estuary as a bore (wall of turbulent water like the waves at the coast after they break). This inland surge of water can often cause most or all of the damage from a distant tsunami. For example, in Seaside the damage from the 1964 Alaskan tsunami occurred along the Necanicum River and Neawanna Creek, well inland from the coast. In addition, storm waves ride on top of the tsunami waves and may cause even more destruction.53

History of the Hazard in Lincoln County The Pacific Northwest experienced a subduction zone earthquake estimated at magnitude 9 on January 26, 1700. The earthquake generated a tsunami that caused damage as far away as Japan. Cascadia subduction zone earthquakes and associated tsunamis have occurred on average every 500 years over the last 3,500 years in the Pacific Northwest. The time between events has been as short as 100 to 200 years and as long as 1,000 years. The geologic record indicates that over the last 10,000 years approximately 42 tsunamis have been generated off the Oregon Coast in connection to ruptures of the CSZ (19 of the events were full-‐margin ruptures and arrived approximately 15-‐20 minutes after the earthquake).54 Numerous distant tsunami events have also occurred in the past, including 28 documented by Oregon wave gauges since 1854, notable events are listed below.

Figure II-14 Cascadia Earthquake Timeline

Source: DOGAMI

53 State of Oregon Emergency Management Plan: Natural Hazards Mitigation Plan: Tsunami, March 2002



In March 1964, a tsunami struck southeastern Alaska following an earthquake beneath Prince William Sound and arrived along the Alaska coastline between 20 and 30 minutes after the quake, devastating villages. Damages were estimated to be over $100 million. Approximately 120 people drowned. The tsunami spread across the Pacific Ocean and caused damage and fatalities in other coastal areas. Four children drowned at Beverly Beach and significant property damaged was incurred, including $5,000 in Depoe Bay. Along the entire Oregon Coast damage was estimated to be between $750,000 and $1 million. Tsunamis of lesser magnitude occurred along the Oregon Coast in 1946, 1960, and 1968. Tsunami wave heights reached 10-‐11.5 feet at Depoe Bay and 11.5 feet at Newport.55

A 9.0 magnitude earthquake originating from Japan caused approximately $7.1 million worth of damages along the Oregon Coast. Particularly, there was extensive damage to the Port of Brookings (Curry County; $6.7 million), as well as the Port of Depoe Bay (Lincoln County; $182,000), and Charleston Harbor (Coos County; $200,000); Salmon Harbor on Winchester Bay (Douglas County) and the South Beach Marina in Newport (Lincoln County) were also affected. On March 15, 2011 Governor Kitzhaber declared a State of Emergency was declared by Executive Order in Curry County. Approximately 40% of all docks at the Port of Brookings were destroyed or rendered unusable (including a dock leased by the U.S. Coast Guard) compromising commercial fishing and U.S. Coast Guard operations. Along the Oregon Coast local official activated the Emergency Alert System and sirens, implemented “reverse 9-‐1-‐1” and conducted door-‐to-‐door notices in order to evacuate people form the tsunami inundation zone. Local governments activate their Emergency Operations Centers and the state activated its Emergency Coordination Center.

Hazard IdentificationTsunami inundation modeling attempts to identify areas affected by tsunamis, and the water depths, current strengths, wave heights, and wave arrival times associated with an event. Generally this analysis is conducted for “worst case” scenarios, but it can also be used to look at damages from tsunamis of lesser magnitude Areas along the coast, low-‐lying areas along bays or inlets that connect to the ocean should be designated as hazard zones. Areas along rivers that connect to the ocean should also be designated as tsunami hazard areas for at least three kilometers inland and as far as ten kilometers inland for large, flat coastal rivers.56 In the event of an 8.8 magnitude earthquake, 60-‐200 miles off the coast, and during high tide, the inundation elevations would be: Siletz Bay, 40 feet; Depoe Bay, 31 feet; Newport, 31 feet; Yaquina Joe Point (Waldport), 26 feet; and Yachats, 27 feet.57

DOGAMI has conducted analysis resulting in extensive mapping along the Oregon Coast. The maps depict the expected inundation for tsunamis produced by a magnitude 8.8 to 8.9 undersea earthquake. The tsunami hazard maps were produced to help implement Senate Bill 379 (SB 379), which was passed by the 1995 regular session of the Oregon Legislature. SB 379, implemented as Oregon Revised Statutes (ORS) 455.446 and 455.447, and Oregon Administrative Rules (OAR) 632-‐005 limits construction of new essential facilities and special occupancy structures in tsunami flooding zones. In this analysis they have taken into

55 DOGAMI Distant Tsunami Inundation Map (2013)

56 Geohazards International. Preparing Your Community for Tsunamis: A Guidebook for Local Advocates. 2007

57 Lincoln County Emergency Services, June 2007. Lincoln County Hazard Analysis


account topography, bathymetry data, and information about potential regional tsunami sources. It should be noted that these maps were produced in 1995. Since then DOGAMI and other agencies have conducted a large number of tsunami inundation studies. An update of these maps was completed in 2013, as described below.

Tsunami inundation maps were created by the Department of Geology and Mineral Industries (DOGAM() to be used for emergency response planning for coastal communities.58 There are 30 tsunami inundation map panels for Lincoln County (15 for the local source tsunami scenarios and 15 for the distant source tsunami scenarios).

The local source tsunami inundation maps display the output of computer modeling showing five tsunami event scenarios shown as “T-‐shirt” sizes S, M, L, XL, and XXL. The transition line between the wet and dry zones is termed the Wet/ Dry Zone, only the XXL Wet/ Dry Zone is shown on the map. The distant source tsunami inundation maps show the affects of tsunamis generated by earthquakes along the “Ring of Fire” (the Circum-‐Pacific belt, the zone of earthquake activity surrounding the Pacific Ocean). The distant tsunami inundation maps model the 1964 Prince William Sound event (Alaska M9.2) and a hypothetical Alaska Maximum event scenario; only the Alaska Maximum Wet/ Dry Zone is shown on the map. Both the local and distant source tsunami inundation maps show simulated wave heights and inundation extents for the various scenarios.

For more information on the regulatory and non-‐regulatory maps visit the Oregon Tsunami Clearinghouse resource library:

Regulatory (SB 360) -‐ http://www.oregongeology.org/tsuclearinghouse/pubs-‐regmaps.htm

Non-‐Regulatory Tsunami-‐Inundation Maps: http://www.oregongeology.org/tsuclearinghouse/pubs-‐inumaps.htm

Evacuation maps (brochures) are available for the populated areas of Lincoln County. The Department of Geology and Mineral Industries (DOGAMI) developed the evacuation zones in consultation with local officials; local officials developed the routes that were reviewed by the Oregon Department of Emergency Management (OEM). The maps shows the worst case scenario for a local source and distant source tsunami event and are not intended for land-‐use planning or engineering purposes. There are twelve (12) evacuation brochures created for Lincoln County covering the following communities: Lincoln City North, Lincoln City South, Gleneden Beach/ Salishan Spit, Lincoln Beach, Depoe Bay, Newport North, Newport South, Toledo, Seal Rock, Waldport, Yachats North (San Marine), and Yachats.

For more information on the evacuation brochures visit the Oregon Tsunami Clearinghouse resource library:

http://www.oregongeology.org/tsuclearinghouse/pubs-‐evacbro.htm

A free application is also available that displays the evacuation routes in coastal areas of Oregon:

iPhone: https://itunes.apple.com/us/app/tsunamievac-‐nw/id478984841?mt=8

58 DOGAMI website and Lincoln County Risk Report (2014, unpublished draft)


Android: https://play.google.com/store/apps/details?id=org.nanoos.tsunami&hl=en


It is difficult to predict when the next tsunami will occur. With respect to distant sources, Oregon has experienced ten tsunamis in the last 135 years with only three causing measurable damage. Thus, the average recurrence interval for tsunamis on the Oregon coast from distant sources would be about 15 years. However, the time interval between events has been as little as one year and as much as 73 years. Since only a few tsunamis caused measurable damage, a recurrence interval for distant tsunamis does not have much meaning for this region.

A tsunami originating from a Cascadia Subduction Zone earthquake could be exceedingly destructive and thus is of greater concern than distant tsunamis. The average recurrence interval for a CSZ event is between 500 and 600 years. There have been seven CSZ events in the last 3500 years with time between individual events varying from 150 to 1000 years. The last CSZ even occurred approximately 300 years ago. According to the Oregon NHMP, the return period for the largest of the CSZ earthquakes (Magnitude 9.0+) is 530 years with the last CSZ event occurring 314 years ago in January of 1700. The probability of a 9.0+ CSZ event occurring in the next 50 years ranges from 7 -‐ 12%. Notably, 10 -‐ 20 “smaller” Magnitude 8.3 -‐ 8.5 earthquakes identified over the past 10,000 years affect only the southern half of Oregon and northern California. The average return period for these events is roughly 240 years. The combined probability of any CSZ earthquake occurring in the next 50 years is 37 -‐ 43%.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a local source tsunami event is “moderate”, meaning one incident is likely within the next 35 – 75 year period; the committee believes that the County’s probability of experiencing a distant source tsunami event is “high”, meaning one incident is likely within the next 35 year period. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.59


The Lincoln County Natural Hazards Steering Committee rated the County as having a “high” vulnerability to the local source tsunami event, meaning that more than 10-‐percemt of the county’s population or assets would be affected by a major emergency or disaster; the committee rated the County as having a “low” vulnerability to the distant source tsunami event, meaning that less than 1-‐percent of the county’s population or assets would be affected by a major emergency or disaster. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.60

The Oregon coast is at risk from tsunamis that originate from local and distant sources. Lincoln County has six communities in the tsunami inundation zone (from north to south):


60 Ibid.


Lincoln City, Depoe Bay, Newport, Toledo, Waldport, and Yachats. Figure II-‐15 below, shows the amount and percentage of developed land within the SB 379 tsunami-‐inundation zone as of 2007; the data shows that Waldport and Yachats have the most developed land within the tsunami inundation zone; Lincoln City, Newport, and unincorporated areas also have significant percentages in the inundation zone.

Figure II-15 Developed Land in Tsunami-Inundation Zone

Source: Wood N (2007) Variations in City Exposure and Sensitivity to Tsunami Hazards in Oregon. USGS. http://pubs.usgs.gov/sir/2007/5283/sir2007-‐5283.pdf

Figure II-‐16 shows the number and percentage of residents within the SB 379 tsunami-‐inundation zone. The data indicate that the unincorporated areas of the county, Lincoln City, and Waldport have the highest number of residents within the tsunami-‐inundation zone; while Waldport, Yachats, and Lincoln City have the highest percentage within the tsunami-‐inundation zone.

Figure II-16 Residents in Tsunami-Inundation Zone

Source: Wood N (2007) Variations in City Exposure and Sensitivity to Tsunami Hazards in Oregon. USGS. http://pubs.usgs.gov/sir/2007/5283/sir2007-‐5283.pdf

Newport’s South Beach district is an example of a highly vulnerable populated area. This includes South Beach State Park, which during the summer time, can become teeming with visitors and tourists. Some other vulnerable areas include Waldport, which is at an elevation


of 12 feet, and the motels at the D River in Lincoln City, which are at an elevation of only 10 feet. Although most communities have evacuation maps and evacuation plans, many casualties are expected from a local tsunami event. The built environment in the inundation zone will be especially hard hit. It is estimated that if a CSZ tsunami were to hit Lincoln County, 40% of the population and 40% of real property would be affected. 61

In 2013, DOGAMI produced new Tsunami Inundation Maps (TIMs) for the entire Oregon coast. The TIMs identify both local and distant tsunami inundation zones by event size. The maps also tabulate the affected buildings located within the local and distant source tsunami inundation zones. Table II-‐10 shows the number and percentage of buildings located in the local source Tsunami Inundation Zones. Approximately one-‐third of all buildings in the county are located within the “Extra Large” (one event per 1,050-‐1,200 years) tsunami inundation zone; the unincorporated areas of the county account for approximately half of those buildings, while Lincoln City and Newport account for about one-‐third. Particular cities of concern include Yachats, Waldport, and Lincoln City, which have approximately 70%, 44%, and 34% of their buildings in the “Extra Large” tsunami inundation zone. Notably, 20% of Waldport’s building stock is located within the “small” (one event per 300 years) tsunami inundation zone.

Table II-10 Buildings within the Local Source Tsunami Inundation Zones

Source: DOGAMI Tsunami Inundation Map Data compiled for all mapped areas by OPDR. Note 1: Buildings counts are based on polygon centroids and are cumulative with the mapped areas. Note 2: One event per: 300 years (S), 425-‐525 years (M), 650-‐800 years (L), 1,050-‐1,200 years (XL), 1,200 years (XXL) Note 3: The data above may include duplicate counts based on overlaps of the 15 plates that map the tsunami indundation zone in Lincoln County.

Table II-‐11 shows the number and percentage of buildings located in the distant source Tsunami Inundation Zones. Fewer than 2% of all buildings are located within the Alaska M9.2 tsunami inundation zone, while approximately 5% of all buildings are located within the Alaska Maximum tsunami inundation zone. Particular areas of concern include the unincorporated county, Waldport, Yachats, and Newport. Although not included in the tabulations the county’s ports, particularly Depoe Bay and the South Beach Marina in Newport are highly vulnerable to distant source tsunamis.

61 Lincoln County Emergency Services, June 2007. Lincoln County Hazard Analysis.

# % # % # % # % # %Entire'County 32,567 1,830 5.6% 4,223 13.0% 6,524 20.0% 10,807 33.2% 11,502 35.3%

Lincoln'City 6,805 346 5.1% 970 14.3% 1,380 20.3% 2,285 33.6% 2,391 35.1%Depoe'Bay 1,262 9 0.7% 14 1.1% 30 2.4% 264 20.9% 320 25.4%Newport 6,381 413 6.5% 832 13.0% 1,130 17.7% 1,518 23.8% 1,622 25.4%Toledo 2,051 36 1.8% 62 3.0% 111 5.4% 237 11.6% 247 12.0%Waldport 1,691 345 20.4% 468 27.7% 570 33.7% 749 44.3% 758 44.8%Yachats 900 47 5.2% 156 17.3% 474 52.7% 633 70.3% 653 72.6%Unincorporated'Areas 13,477 634 4.7% 1,721 12.8% 2,829 21.0% 5,121 38.0% 5,511 40.9%

TotalBuildings

Local1Source1(CSZ)1Tsunami1Inundation1EventSmall Medium Large Extra1Large Extra1Extra1Large


Table II-11 Buildings within the Distant Tsunami Inundation Zones

Source: DOGAMI Tsunami Inundation Map Data compiled for all mapped areas by OPDR. Note 1: Buildings counts are based on polygon centroids and are cumulative with the mapped areas. Note 2: One event per: 300 years (S), 425-‐525 years (M), 650-‐800 years (L), 1,050-‐1,200 years (XL), 1,200 years (XXL) Note 3: The data above may include duplicate counts based on overlaps of the 15 plates that map the tsunami indundation zone in Lincoln County.

Coastal communities in Lincoln County are threatened to varying degrees by CSZ-‐related tsunami inundation. In the tables below, population vulnerability is characterized in terms of exposure, demographic sensitivity, and short-‐term resilience of at-‐risk individuals.62 Nate Wood, et al. (USGS) performed a cluster analysis of the data for coastal communities in the Pacific Northwest to identify the most vulnerable communities in the region.63 The tables below provide community specific information and identify the most vulnerable communities based upon the cluster analysis. Wood, et al. conducted a comprehensive analysis to derive overall community clusters based on (1) the number of people and businesses in the tsunami hazard zone, (2) the demographic characteristics of residents in the zone, and (3) the number of people and businesses that may have insufficient time to evacuate based on slow and fast walking speeds.64 The study placed all communities within Lincoln County within the following cluster category: “Relatively low numbers of residents, employees, or customer-‐heavy businesses in the tsunami hazard zones that will likely have sufficient time to reach high ground before tsunami wave arrival”.65 Lincoln City and Toledo were noted to have slightly higher percentages of their population in the over age 65 category which may benefit from specific age related mitigation measures. The report suggests that education efforts that recognize demographic differences may be the best evacuation related mitigation measure for the Lincoln County communities.66

62 Nathan J. Wood, Jeanne Jones, Seth Spielman, and Mathew C. Schmidtlein. “Community clusters of tsunami vulnerability in the US Pacific Northwest”, PNAS 2015 112 (17) 5354-‐5359.

63 Ibid

64 Ibid.

65 Ibid.

66 Ibid.

# % # %Entire'County 32,567 534 1.6% 1,655 5.1%

Lincoln'City 6,805 33 0.5% 86 1.3%Depoe'Bay 1,262 3 0.2% 7 0.6%Newport 6,381 44 0.7% 326 5.1%Toledo 2,051 8 0.4% 14 0.7%Waldport 1,691 144 8.5% 457 27.0%Yachats 900 29 3.2% 67 7.4%Unincorporated'Areas 13,477 273 2.0% 698 5.2%

TotalBuildings

Distant0Source0(A7ASZ)0Tsunami0Inundation0EventAlaska0M9.2 Alaska0Maximum


Table II-‐12 provides exposure analysis for the total number of residents, employees, public venues, dependent care facilities, and community businesses that are located within the “Large” local tsunami-‐hazard zone. The table shows that the unincorporated county (2,222) and Lincoln City (1,257) have the largest number of residents in the “Large” local tsunami-‐hazard zone; while Newport (1,445) and Lincoln City (584) have the largest number of employees located in the zone. The cities of Lincoln City (23) and Newport (10) have the largest number of public venues in the “Large” local tsunami-‐hazard zone; while Waldport (10) has the largest number of dependent care facilities in the zone and Newport (53) has the largest number of community businesses in the zone. Based upon the cluster analysis all of the communities within Lincoln County are categorized within the least vulnerable group with regard to people or facilities in tsunami-‐hazard zones; although the report notes that Newport does have a high number of employees exposed to the tsunami-‐hazard zone.67

Table II-12 Total Number in Tsunami-hazard Zones

Source: Nate Wood, “Community clusters of tsunami vulnerability in the US Pacific Northwest” (2015).

The sensitivity of communities within Lincoln County is also related to demographic characteristics of the population. Table II-‐13 shows the results of an analysis of commonly used demographic variables associated with block level data in the 2010 US Census.68 The data shows that Yachats (42%), Waldport (27%), and Lincoln City (16%) have the highest percentage of their populations within the tsunami-‐hazard zone. In addition, the table shows that Depoe Bay (40%), Yachats (33%), Waldport (28%), and the unincorporated county (29%) have a relatively high percentage of their population greater than 65 years of age. In addition, the table shows that Waldport (60%) has a high percentage of renter-‐occupied households. The cluster analysis (Wood et al) suggests that Lincoln County communities have relatively minor variability in racial composition, housing tenure, and age compared to other communities in the study.69 The study does suggest that mitigation efforts may want to focus on the needs of older residents within Depoe Bay, Newport, Waldport, Yachats, and unincorporated Lincoln County; while the needs of renters and Hispanic or Latino populations may be more important in Lincoln City and Toledo.

67 Ibid.

68 Ibid.

69 Ibid.

Community Residents EmployeesPublic2Venues

Dependent2Care2

FacilitiesCommunity2Businesses

Lincoln2City 1,257 584 23 1 27Depoe2Bay 27 0 0 0 0Newport 578 1,445 10 1 53Toledo 104 44 0 1 0Waldport 552 283 6 10 32Yachats 289 10 0 0 3Unincorporated 2,222 341 8 0 17

Total,number,in,tsunami1hazard,zones


Table II-13 Characteristics of Residents in Tsunami-hazard Zones


The ability to reach higher ground before tsunami wave arrival is a critical aspect of population vulnerability to local tsunami hazards in Lincoln County. Table II-‐14 shows the total number of residents and employees that may not have sufficient time to evacuate, assuming a slow walk (1.1 m/s), a local tsunami event; the table also shows the number of public venues, dependent care facilities, and community businesses that have significant customer presence in places where travel times out of hazards zones are greater than the predicated wave arrival times.70 The table shows that few individuals would have difficulty evacuating; Lincoln City has the largest number of residents and employees that may have difficulty evacuating.

Table II-14 Total Number That May Not Have Sufficient Time to Evacuate, Assuming a Slow Walk


An individual’s ability to move faster during evacuation is another element of short-‐term resilience to tsunamis. Table II-‐15 shows the number of individuals that may not be able to evacuate a local tsunami assuming a faster walk speed (1.52 m/s). Similar to the slow walk evacuation (above) there are few individuals that would have difficulty evacuating within Lincoln County.

70 Ibid.

Community

Total&Residents&in&Hazard&Zone

Hispanic&or&Latino

American&Indian&or&Alaska&Native

Under&5&years&in&age

Single?mother&

households

More&than&65&years&in&

age

Living&in&group&

quarters

Renter?occupied&

households

Lincoln&City 16% 6% 5% 4% 6% 21% 1% 46%Depoe&Bay 2% 2% 1% 1% 1% 40% 0% 37%Newport 6% 4% 2% 5% 6% 24% 1% 39%Toledo 3% 7% 12% 4% 8% 12% 0% 48%Waldport 27% 3% 4% 2% 6% 28% 0% 60%Yachats 42% 6% 3% 2% 3% 33% 0% 41%Unincorporated 10% 3% 4% 3% 4% 29% 3% 25%


Dependent2Care2


Lincoln2City 233 16 1 0 0Depoe2Bay 0 0 0 0 0Newport 0 0 0 0 0Toledo 0 0 0 0 0Waldport 2 0 0 0 0Yachats 0 0 0 0 0Unincorporated 42 0 0 0 0


Table II-15 Total Number That May Not Have Sufficient Time to Evacuate, Assuming a Fast Walk


Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the local tsunami hazard is rated #5, out of 13 rated hazards, with a total score of 201 and the distant tsunami hazard is rated #9, out of 13 rated hazards, with a total score of 161.

Community Hazard Issues Issues associated with the risk of a tsunami event in Lincoln County include population and property distribution in the hazard area, adequate tsunami warnings, and sufficient information on utilities, and infrastructure that may be impacted by a tsunami. People and properties located in low-‐lying areas near the ocean are at greatest risk from tsunami inundation.

Tsunamis generated by a CSZ event just off the Oregon coast can strike the coast within five to thirty minutes leaving little time for an official warning and likely disrupting power, transportation, communications, water and wastewater service, food availability and public safety (among others).. The actual ground shaking of the earthquake may be the only warning received.

Conversely, distant tsunamis generated by earthquakes or other events occurring thousands of miles away will take several hours to reach the coast. In these cases there will be time for an official, coordinated warning and evacuation.

A significant tsunami event can be expected to cause disruption of power, contamination of water supplies, loss of essential communication systems, a large amount of debris, and traffic congestion. Dealing with evacuees would be a major challenge in the first days after


Dependent2Care2


Lincoln2City 15 0 0 0 0Depoe2Bay 0 0 0 0 0Newport 0 0 0 0 0Toledo 0 0 0 0 0Waldport 0 0 0 0 0Yachats 0 0 0 0 0Unincorporated 26 0 0 0 0


the event. The tourist industry would be non-‐existent for a considerable period of time and damaged public facilities would have to be restored or replaced at considerable cost.

Boats and ships in harbor are also at great risk from the sudden changes in sea level. The water level can change so fast that lines holding ships to the pier have the potential to break. Navigating in these conditions would be treacherous as well as unpredictable; dangerous currents can continue for hours while the water in the harbor shifts back and forth.

The rapidly increasing sea level caused by the tsunami picks up debris, rocks, logs and other materials that act as projectiles causing additional damage and dangers.


Lincoln County Comprehensive Plan and Land Use Code Lincoln County has enacted a Comprehensive Land Use Plan and is implementing land use regulations in compliance with ORS 197 and the Statewide Planning Goals. The County has enacted and enforces a coastal flood hazard area overlay zone, identified on FIRM maps as V zones, which is applied to all areas mapped as subject to high velocity ocean waters, including but not limited to storm surge or tsunami inundation. The regulations are designed to reduce the risk of tsunami damage to new and substantially improved structures within known tsunami hazard areas. The V-‐zones of the FIRMs do not reflect the known local or distant source tsunami events. Currently neither the county nor the cities have a tsunami hazard overlay zone; the county and cities have included an action item within this plan to evaluate and adopt new policies to increase community resilience to the tsunami hazard (Tsunami #2).

For more information see the Department of Land Conservation and Development’s “Preparing for a Cascadia Subduction Zone Tsunami: A Land Use Guide for Oregon Coastal Communities”.

After planning approval, or prior to issuance of a development permit for construction of, conversion to, or replacement of any development on the following list, the owner or developer shall consult with the local building official to determine whether ORS 455 applies, specifically the “prohibition of construction for certain facilities and structures” and, the “regulation of certain vulnerable structures”, identified in the 2001 Edition of the statutes as ORS 455.446 and ORS 455.447

Tsunami Inundation Maps

DOGAMI was instrumental in the passage of SB 379 (1995) resulting in changes to Oregon Revised Statute 445.446 and 445.447. The agency, using a combination of regional tsunami simulations and professional judgment, created tsunami hazard maps for the entire coast to implement ORS 455.446 and 455.447. The statute limits the construction of new essential facilities and special occupancy structures in the mapped tsunami inundation zone. Examples of essential structures are fire and police stations and hospitals. These have been used to create evacuation maps of all of the coastal incorporated cities of Lincoln County: Lincoln City, Depoe Bay, Newport, Waldport, and Yachats. Based on the new TIMs DOGAMI produced in 2012, changes to the SB 379 line are being considered by the state.



Once an earthquake or tsunami occurs, an evaluation of roadways and bridges will occur for damages. Initial damage assessment will be logged and a plan of action developed. Life-‐line routes (arterial routes) have been identified and will receive priority. It is expected that inter-‐agency support will be highly needed. Lincoln County Road Dept. participates in inter-‐agency drills.

Lincoln County bridges are inspected every two years. Bridges are inspected in accordance with National Bridge Inspection Standards (NBIS). The County uses the NBIS inspections to guide bridge maintenance work. In the event of a critical finding, emergency repair work may be initiated. Bridges found to be incapable of carrying legal loads are posted.


There are two (2) identified Tsunami action items for Lincoln County; in addition, several of the Multi-‐Hazard action items affect the Tsunami hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV. To view city actions see the appropriate city addendum within Volume III.

Lincoln County NHMP July 2015 Page VE-1

VOLCANO


Causes and Characteristics of Volcanic Eruption Lincoln County, and the Pacific Northwest, lie within the “ring of fire,” an area of very active volcanic activity surrounding the Pacific Basin. Volcanic eruptions occur regularly along the ring of fire, in part because of the movement of the Earth’s tectonic plates. The Earth’s outermost shell, the lithosphere, is broken into a series of slabs known as tectonic plates. These plates are rigid, but they float on a hotter, softer layer in the Earth’s mantle. As the plates move about on the layer beneath them, they spread apart, collide, or slide past each other. Volcanoes occur most frequently at the boundaries of these plates and volcanic eruptions occur when molten material, or magma, rises to the surface.

The primary threat to lives and property from active volcanoes is from violent eruptions that unleash tremendous blast forces, generate mud and debris flows, or produce flying debris and ash clouds. The immediate danger area in a volcanic eruption generally lies within a 20-‐mile radius of the blast site. The following section outlines the specific hazards posed by volcanoes.

Volcanoes are commonly, but not always, conical hills or mountains built around a vent that connects with reservoirs of molten rock below the surface of the earth.71 Volcanoes are built up by an accumulation of their own eruptive products: lava or ash flows and airborne ash and rocks. When pressure from gases or molten rock becomes strong enough to cause an upsurge, eruptions occur. Gases and rocks are pushed through the vent and spill over, or fill the air with lava fragments. Figure II-‐17 diagrams the basic features of a volcano.

The effects of a major volcanic event can be widespread and devastating. The Cascade Range in Washington, Oregon and northern California is one of the most volcanically active regions in the United States. Volcanoes produce a wide variety of hazards that can destroy property and kill people. Large explosive eruptions can endanger people and property hundreds of miles away and even affect the global climate. Some volcano hazards such as landslides can occur even when a volcano is not erupting.

Although there are no active volcanoes in Lincoln County, it is important for counties to know the potential impacts of nearby volcanoes. While the immediate danger area around a volcano is approximately 20 miles, ash fall problems may occur as much as 100 miles or more from a volcano’s location.

71 Tilling, Robert I., Volcanoes, USGS General Interest Publication, (1985).

There are no significant changes in the potential for Volcano hazards to occur in Lincoln County since 2009. However, some new information was incorporated from the Central Cascades Volcano Coordination Plan. In addition, the format of the section and minor changes have occurred.

Page VE-2 July 2015 Lincoln County NHMP

Figure II-17 Volcanic Hazard from a Composite Type Volcano

Source: Walder et al, “Volcano Hazards in the Mount Jefferson Region,” 1999; W.E. Scott, R.M. Iverson, S.P. Schilling, and B.J. Fischer, Volcano Hazards in the Three Sisters Region, Oregon: U.S. Geological Survey Open-‐File Report 99-‐437, 14p., 200.,

Related Hazards

Ash / Tephra

Tephra is fragmented volcanic rock of any size ejected from a volcano. It consists of volcanic ash (sand-‐sized or finer particles) and larger fragments. During explosive eruptions, tephra together with a mixture of hot volcanic gas are ejected rapidly into the air from volcanic vents. Larger fragments fall down near the volcanic vent while finer particles drift downwind as a large cloud. When ash particles fall to the ground, they can form a blanket-‐like deposit, with finer grains carried further away from the volcano. In general, the thickness of tephra deposits decreases in the downwind direction. Tephra hazards include impact of falling fragments, respiratory problems, damage to crops and other vegetation, contamination of drinking water, roof collapse, burial of transportation routes, and mechanical or electrical failure of car and jet engines.


During an eruption that emits tephra, deposition is controlled by the prevailing wind direction. 72 The predominant wind pattern over the Cascades is from the west, and previous eruptions seen in the geologic record have resulted in most ash fall drifting to the east of the volcanoes. 73

Lava flows

Lava flows are streams of molten rock that erupt relatively non-‐explosively from a volcano and move downslope, causing extensive damage or total destruction by burning, crushing, or burying everything in their path. Secondary effects can include forest fires, flooding, and permanent reconfiguration of stream channels. 74

Pyroclastic flows and surges

Pyroclastic flows are avalanches of ash, rocks, and gas at temperatures of 600 to 1500 degrees Fahrenheit. They typically sweep down the flanks of volcanoes at speeds of up to 150 miles per hour. Pyroclastic surges are a more dilute mixture of gas and ash. They can move even more rapidly than a pyroclastic flow and are more mobile. Both generally follow valleys, but surges sometimes have enough momentum to overtop hills or ridges in their paths. Because of their high speed, pyroclastic flows and surges are difficult or impossible to escape. If it is expected that they will occur, evacuation orders should be issued as soon as possible for the hazardous areas. Objects and structures in the path of a pyroclastic flow are generally destroyed or swept away by the impact of debris or by accompanying hurricane-‐force winds. Wood and other combustible materials are commonly burned. People and animals may also be burned or killed by inhaling hot ash and gases. The deposit that results from pyroclastic flows is a combination of rock and ash and is termed ignimbrite or welded tuff. These deposits may accumulate to hundreds of feet thick and can harden to resistant rock. 75

Lahars and debris flows

Lahar is an Indonesian term that describes a hot or cold mixture of water and rock fragments flowing down the slopes of a volcano or river valley.76 Lahars typically begin when floods related to volcanism are produced by melting snow and ice during eruptions of ice-‐clad volcanoes like South Sister, Mt. Hood, Mt. Rainier, or Mount Shasta. Heavy rains can also generate lahars or melting snow on steep, unconsolidated slopes of volcanoes, even if no eruption occurs. Floods and debris flows can be generated by the displacement of water from volcanic lakes, which can overtop dams or move down outlet streams.

72 Oregon State Natural Hazard Mitigation Plan. 2012.” Volcanic Hazards Chapter,” http://csc.uoregon.edu/opdr/sites/csc.uoregon.edu.opdr/files/docs/ORNHMP/OR-‐SNHMP_volcano_chapter.pdf 73 Ibid. 74 Oregon State Natural Hazard Mitigation Plan. 2012.” Volcanic Hazards Chapter,” http://csc.uoregon.edu/opdr/sites/csc.uoregon.edu.opdr/files/docs/ORNHMP/OR-‐SNHMP_volcano_chapter.pdf 75 Ibid. 76 USGS website: http://volcanoes.usgs.gov/Hazards/What/Lahars/lahars.html


Lahars and debris flows react much like flash flood events in that a rapidly moving mass moves downstream, picking up more sediment and debris as it scours out a channel. This initial flow can also incorporate water from rivers, melting snow, and ice. By eroding rock debris and incorporating additional water, lahars and debris flows can easily grow to more than ten times their initial size, but as they move farther away from the volcano they eventually begin to lose sediment load and decrease in size.77

Lahars and debris flows often cause serious economic and environmental damage. The direct impact of the turbulent flow front, along with impacts from boulders, logs, and other debris incorporated in the flow, can easily crush, abrade, or shear off at ground level just about anything in the flow path. Even if not crushed or carried away by the force of the flow, buildings and valuable land may become partially or completely buried by one or more cement-‐like layers of rock debris. By destroying bridges and roads, lahars and debris flows can also trap people in areas vulnerable to other volcanic hazards, especially if the debris deposits are too deep, too soft, or too hot to cross.78

Volcanic Landslides (debris avalanches)79

Landslides and debris avalanches are a rapid downhill movement of rocky material, snow, and (or) ice. Volcanic landslides range in size from small movements of loose debris on the surface of a volcano to massive collapses of the entire summit or sides of a volcano. Steep volcanoes are susceptible to landslides because they are built up partly of layers of loose volcanic rock fragments. Landslides on volcano slopes are triggered not only by eruptions, but also by heavy rainfall or large earthquakes that can cause materials to break free and move downhill.

Earthquakes

Earthquakes are another potentially hazardous event associated with volcanic eruptions. Volcanic earthquakes are commonly smaller than magnitude 2.5, roughly the threshold for felt shaking by observers close to the event. Swarms of small earthquakes may persist for weeks to months before eruptions, but little or no damage would occur to buildings in surrounding communities. Some volcanic related swarms may include earthquakes as large as about magnitude 5.

History of the Hazard in Lincoln County The closest volcanoes to Newport are in the Three Sisters area approximately 125 miles to the east. Given the right wind conditions, ash fall in Lincoln County could be a concern.

The Cascade Range of the Pacific Northwest has more than a dozen active volcanoes. These familiar snow-‐clad peaks are part of a 1,000 mile-‐long chain of volcanically active mountains which extends from southern British Columbia to northern California. Cascades volcanoes tend to erupt explosively and eruptions have occurred at an average rate of 1-‐2 per century during the last 4,000 years. Future eruptions are certain. Seven Cascades volcanoes have 77 Ibid. 78 Ibid. 79 Wright and Pierson, Living With Volcanoes, USGS Volcano Hazards Program Circular 1973, (1992).


erupted since the first U.S. Independence Day slightly more than 200 years ago. Four of those eruptions would have caused considerable property damage and loss of life had they occurred today without warning. The most recent events were Mt. St. Helens in Washington (1980-‐86) and Lassen Peak in California (1914-‐1917). The existence, position and recurrent activity of Cascades volcanoes are generally thought to be related to the convergence of shifting crustal plates. As population increases in the Pacific Northwest, areas near volcanoes are being developed and recreational usage is expanding. As a result more and more people and property are at risk from volcanic activity.

Figure II-18 Eruptive and major debris-flow and flood events in the central Cascades of Oregon during the past 14,000 years.

Source: Central Cascades Volcano Coordination Plan. The events printed in italics are poorly dated, so their ages are less well known than those in normal font. The Mazama tephra fall was produced by the cataclysmic eruption of Mount Mazama that created Crater Lake 7,700 years ago.

Mount St. Helens Case Study

On May 18, 1980, following two months of earthquakes and minor eruptions and a century of dormancy, Mount St. Helens, Washington, exploded in one of the most devastating volcanic eruptions of the 20th century. Approximately 0.67 cubic miles of volume was removed (lowering the mountain 1,314 feet), 57 people died, lahars damaged 27 bridges and nearly 200 homes, 4 billion board feet of timber was blown down, and damage exceeded 1.2 billion dollars.80 Fortunately, most people in the area were able to evacuate safely before the eruption because the U.S. Geological Survey (USGS) and other scientists had alerted public officials to the danger. As early as 1975, USGS researchers had warned that Mount St. Helens might soon erupt. Coming more than 60 years after the last major

80 Brantley, Steve and Bobbie Myers. Mount St. Helens – From the 1980 Eruption to 2000. USGS Fact Sheet 036-‐00 Online Version 1.0. http://pubs.usgs.gov/fs/2000/fs036-‐00/

Mount Jefferson area Three Sisters Mafic%volcanoes%north%and%south%of%Three%Sisters% Newberry%Volcano%

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

Year

s ag

o

Floods and debris flows from moraine-dammed lakes

Lava flows, scoria cones, and tephra falls from Forked Butte and other nearby vents

Tephra falls, pyroclastic flows, lava domes, and lava flows from South Sister flank vents

Floods and debris flows from moraine-dammed lakes

Mazama tephra fall

Lava flows and tephra falls from Middle Sister

Lava flows, scoria cones, and tephra falls from Belknap Crater and numerous vents in McKenzie and Santiam Pass areas

Lava flows, scoria cones, and tephra falls from Sand Mountain vents and Twin Craters

Older lava flows, scoria cones, and tephra falls in Sand Mountain area

Lava flows, scoria cones, and tephra falls in Davis Lake area

Final lava flows, scoria cone, and tephra fall from Mount Bachelor volcanic chain

Lava flows, scoria cones, and tephra falls from Sims Butte and Cayuse and Le Conte Craters

Lava flows, scoria cones, and tephra falls during later stages of Mount Bachelor volcanic chain

Lava flows, scoria cones, and tephra falls from East Rim fissure vents

Central Pumice cone, tephra falls, and several obsidian flows in caldera

Tephra falls and East Lake obsidian flows in caldera

Large flood along Paulina Creek

Tephra fall, pyroclastic flow, and Big Obsidian Flow in caldera

Lava flows, scoria cones, and tephra falls from vents on north, south, and east flanks

Lava flows, scoria cones, and tephra falls from vents on north, south, and east flanks

Lava flows, scoria cones, and tephra falls from vents on north and south flanks


eruption in the Cascades (Lassen Peak, 1915), the explosion of St. Helens was a spectacular reminder that the millions of residents of the Pacific Northwest share the region with live volcanoes.81


The volcanic Cascade Mountain Range is not within Region 1 counties (see locations of potentially active volcanoes in Figure II-‐19 below).

Figure II-19 Potentially Active Volcanoes of the Western United States

Source: USGS. http://www.volcano.si.edu/reports/usgs/maps.cfm#usa

In Figure II-‐17 above, triangles indicate volcanoes that have been active during the past 2,000 years. Other potentially active volcanoes are represented with white triangles.

To identify the areas that are likely to be affected by future events, pre-‐historic rock deposits are mapped and studied to learn about the types and frequency of past eruptions at each 81 Dzurisin, Dan, Peter H. Stauffer, and James W. Hendley II, Living With Volcanic Risk in the Cascades, USGS Fact Sheet 165-‐97, (2000).


volcano. This information helps scientists to better anticipate future activity at a volcano, and provides a basis for preparing for the effects of future eruptions through emergency planning.

Scientists also use wind direction to predict areas that might be affected by volcanic ash; during an eruption that emits ash, the ash fall deposition is controlled by the prevailing wind direction. The predominant wind pattern over the Cascades is from the west, and previous eruptions seen in the geologic record have resulted in most ash fall drifting to the east of the volcanoes. As a result of likely wind patterns, the extent of ash fall associated with a volcanic event would be widespread. Because Lincoln County is far west of the Cascade Range, however, it is not likely to be significantly affected by volcanic ash. The potential and geographical extent of volcanic ash fall from Mt. Hood and Mt. St. Helens are depicted in Figures 3 and 4, respectively.

Geologic hazard maps have been created for most of the volcanoes in the Cascade Range by the USGS Volcano Program at the Cascade Volcano Observatory in Vancouver, WA and are available at http://vulcan.wr.usgs.gov/Publications/hazards_reports.html.

Scientists use wind direction to predict areas that might be affected by volcanic ash; during an eruption that emits ash, the ash fall deposition is controlled by the prevailing wind direction. The predominant wind pattern over the Cascades originates from the west, and previous eruptions seen in the geologic record have resulted in most ash fall drifting to the east of the volcanoes. Regional tephra fall shows the annual probability of ten centimeters or more of ash accumulation from Pacific Northwest volcanoes (generally expected to fall east of the Cascades). Figure II-‐20 depicts the potential and geographical extent of volcanic ash fall in excess of ten centimeters from a large eruption of Mt. St. Helens.

Figure II-20 Regional Tephra-fall Maps

Source: USGS



The annual probability of volcanic activity in or affecting Lincoln County can only be estimated with great uncertainty, but, depending on the type of eruption, ranges from roughly 1 in 1,000 to 1 in 10,000. However, as precursors of volcanic unrest begin the probability of eruption increases greatly. The precursors might include increased seismic activity, temperature and chemical changes in groundwater, ground deformation and release of volcanic gases.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a volcanic event is “low,” meaning one incident is likely within the next 75 – 100 year period (or longer). Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.82


All of the Pacific Northwest is vulnerable to impacts from volcanic activity. Like the rest of Coastal Oregon, Lincoln County has some risk of being impacted by volcanic activity in the Cascade Range. The Lincoln County Natural Hazards Steering Committee rated the county as having a “low” vulnerability to volcanic hazards; meaning less than 1-‐percent of the region’s population or assets would be affected by a major emergency or disaster. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.83

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐6 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the volcano hazard is rated #13, out of 13 rated hazards, with a total score of 114.

Community Hazard Issues Volcanic eruptions can send ash airborne, spreading the ash for hundreds or even thousands of miles. An erupting volcano can also trigger lahars, debris flows, floods, earthquakes, rockfalls, and avalanches. Volcanic ash can cause respiratory problems, electrical storms, agricultural damage, roof collapse, and can contaminate water supplies and severely disrupt transportation.84 Lava flows can crush or bury everything in their path, including structures,

82 Oregon Natural Hazard Mitigation Plan, Department of Land Conservation and Development, 2015.

83 Ibid.

84 Dzurisin, Dan, Peter H. Stauffer, and James W. Hendley II, Living With Volcanic Risk in the Cascades, USGS Fact Sheet 165-‐97, (2000).


roads, railroads, power lines, gas lines, and other important infrastructure; lava flows can also dam rivers and streams, causing floods and contamination of drinking water, and they can ignite fires.

Businesses and individuals can make plans to respond to volcano emergencies. Planning is prudent because once an emergency begins, public resources can often be overwhelmed, and citizens may need to provide for themselves and make informed decisions. Knowledge of volcano hazards can help citizens make a plan of action based on the relative safety of areas around home, school, and work.85

Building and Infrastructure Damage

Ashfall of 0.4 inches is capable of creating serious although temporary disruptions of transportation, operations, sewage disposal and water systems. The history associated with the Mount St. Helens eruption in 1980 resulted in closed highways, airports and other transportation systems for several days to, in some cases, weeks.

Ash can cause substantial problems for internal-‐combustion engines and other mechanical and electrical equipment. Additionally, it can contaminate filters, oil systems and scratch surfaces. Fine ash can cause short circuits in electrical transformers, which in turn cause power outages.

Pollution and Visibility

Ash and tephra fallout from an eruption column can blanket areas within a few miles of the vent with a thick layer of pumice and ash. High altitude winds may carry finer ash from tens to hundreds of miles from the volcano, affecting downwind communities and posing a hazard to aircraft. Fine ash in water supplies will cause brief muddiness and chemical contamination. Ash suspended in the atmosphere is especially a concern for airports, where aircraft machinery could be damaged or clogged. Additionally, ashfall decreases visibility and disrupts daily activities.

Economic Impacts

Volcanic eruptions can disrupt the normal flow of commerce and daily human activity without causing severe physical harm or damage. Ash a few millimeters thick can halt traffic, possibly up to one week, and cause rapid wear of machinery, clog air filters, block drains and water intakes, kill or damage agriculture and severely impact tourism and the economy of the region. The interconnectedness of the region’s economy can be disturbed after a volcanic eruption.

Death and Injury

Inhalation of volcanic ash can cause respiratory discomfort, damage or result in death for sensitive individuals miles away from the volcano. Likewise, emitted volcanic gases such as fluorine and sulfur dioxide can kill vegetation for livestock or cause a burning discomfort in

85 Scott, W.E. et al, Volcano Hazards in the Three Sisters Region, Oregon, USGS Open-‐File Report 99-‐437, (2001).


the lungs. Hazards to human life from debris flows are burial or impact by boulders and other debris.



Existing authorities, policies, programs, and resources include current mitigation programs and activities that are being implemented by city, county, regional, state or federal agencies and/or organizations.

State

Central Cascades Volcano Coordination Plan, 2007

The purpose of this plan is to coordinate the actions that various agencies must take to minimize the loss of life and damage to property before, during, and after hazardous geologic events at Central Cascades volcanoes. OEM and the USGS are partnering to update the plan in 2015, the first coordination meeting occurred on February 27, 2015.

State Natural Hazard Risk Assessment

The state risk assessment chapter on volcanic events provides a useful overview of volcanic risks in Oregon and documents historic volcanic activity. It also recommends a multi-‐hazard approach, given the uncertainty of most of Oregon being impacted by volcanic hazards in the foreseeable future.

A major existing strategy to address volcanic hazards is to publicize and distribute volcanic hazard maps through DOGAMI and USGS. The volcanoes most likely to constitute a hazard to Oregon communities have been the subject of USGS research. Open-‐file reports (OFR) address the geologic history of these volcanoes and lesser-‐known volcanoes in their immediate vicinity. These reports also cover associated hazards and possible mitigation strategies. They are available for volcanoes near Lincoln County including: Mount Saint Helens, Three Sisters, Newberry Volcano, and Crater Lake.

Federal

Volcano Monitoring

USGS and Pacific Northwest Seismic Network at the University of Washington conduct seismic monitoring of major Cascade volcanoes in Washington and Oregon. The USGS serves as the primary dissemination agency for emergency information. As activity changes, USGS scientists provide update advisories and meet with local, state, and federal officials to discuss the hazards and appropriate levels of emergency response.86

86 Central Cascades Volcano Coordination Plan, 2007.


Techniques for monitoring active or potentially active volcanoes focus on three areas— earthquakes (seismicity), ground deformation, and volcanic gases. Magma intruding a volcanic system breaks rock and causes slippage on faults, thereby creating earthquakes; it adds material at depth and heats and pressurizes ground water, thereby bowing up the ground surface; and it releases volcanic gases, mainly water vapor, carbon dioxide, and sulfur dioxide. Heat and volcanic gases from magma warm and add telltale chemicals to the ground water, which affects the composition of spring water throughout the area.

Some monitoring occurs in real-‐time or near real-‐time as data are telemetered from field sites to base stations; other monitoring is done on a periodic basis and requires visits to the field or gathering data from satellites.

Earthquakes in central Oregon are detected and located in real-‐time by the Pacific Northwest Seismic Network (PNSN) at the University of Washington, a cooperative undertaking of the university, USGS, and University of Oregon. Compared to areas that have frequent earthquakes, the station spacing in central Oregon is relatively large, so only earthquakes greater than magnitude (M) 1 or 2 are able to be located routinely. Six stations added in the Three Sisters area since ongoing uplift was recognized in 2001 have reduced the magnitude threshold for location there to about M 0.5 to 1, if all stations are operating. Eight stations were added in the Newberry Volcano area in 2011. These stations, along with a very sensitive seismic array installed by a geothermal energy company on the west flank of the volcano, have significantly reduced the magnitude threshold for location of earthquakes on Newberry. In addition, a cache of instruments at USGS Cascades Volcano Observatory is available to rapidly augment the existing networks should conditions warrant.

Continuous Global Positioning System (CGPS) receivers are able to track ground deformation in real time for a single point on Earth’s surface. At present CGPS receivers at Redmond, Mount Bachelor, and two near South Sister operate in real time. Such a sparse network is of limited use in understanding the complex nature of ground deformation in a volcanic environment. Eight CGPS receivers were installed at Newberry Volcano, along with seismometers, in 2011. This network significantly improved monitoring capabilities at Newberry.

Broader regional coverage is afforded by periodic USGS surveys (typically annual or every few years; more often if conditions warrant) of an array of benchmarks in the Three Sisters and Newberry areas by temporary deployment of GPS instruments. Both areas also have a system of precisely surveyed lines along roads or trails that are used for tilt leveling, a procedure that is capable of measuring slight crustal movements. Another technique called InSAR uses satellite radar data to detect crustal movements over broad areas.

USGS scientists measure output of volcanic gases by airborne surveys. Flights to central Oregon volcanoes are made every few years in order to develop baseline information; additional flights occur as conditions warrant. During times of increased concern, flights could occur as often as atmospheric conditions allow. Annual sampling and chemical and isotopic analysis of spring water from the area permit a broad regional view of how magmatic intrusion is affecting the chemical composition of shallow ground water.

By combining the results of these and other techniques and an understanding of a volcano’s past behavior, the goal of volcano monitoring is to issue forecasts as accurately as possible about the state of a volcanic system and the probability for the onset of potentially


hazardous conditions. Once an eruption has begun, monitoring information is used to forecast the character and expected outcome of the eruption, as well as its end.87

Emergency Coordination

During times of volcanic crisis, USGS scientists will monitor events closely and, together with PNSN and the Oregon Department of Geology and Mineral Industries, issue information statements, alert warnings, updates, and briefing as necessary to keep public officials, the media, and the public aware of potential hazards and other pertinent information. The USGS and the National Weather Service will work together to provide warnings about lahars, floods, and downwind ash-‐fall hazards.

Currently, agencies require information on hazards that affect nearby areas much like airlines and the Federal Aviation Administration require information on tephra plumes that can be hazardous to aircraft hundreds of miles from the source. The information required by these two groups is not always the same, and therefore the USGS in cooperation with various agencies, has developed two hierarchies of alert levels; one directed toward emergency response on the ground and the other towards ash hazards to aircraft.

The USGS issues statements of ground-‐based hazards which are transmitted as appropriate to state and federal agencies including FEMA and the National Weather Service. The counties receive information from Oregon Emergency Management then transmit the notifications as appropriate to local emergency management networks.88

Warning Systems

The best warning of a volcanic eruption is one that specifies when and where an eruption is most likely to occur and what type and size eruption should be expected. Such accurate predictions are sometimes possible but still warrant further research. The most accurate warnings are those in which scientists indicate an eruption is probably hours to days away based on significant changes in a volcano’s earthquake activity, ground deformation and gas emission. Experience from around the world has shown that most eruptions are preceded by such changes over a period of days to weeks.

A volcano may begin to show signs of unrest several months to a few years before an eruption. In these cases a warning that specifies when it might erupt months to years ahead of time are extremely rare. The strategy that the USGS uses to provide volcano warnings in the Cascade Range volcanoes in Washington and Oregon involves a series of alert levels that correspond generally to increasing levels of volcanic activity. As a volcano becomes increasingly active or as incoming data suggest that a given level of unrest is likely to lead to a significant eruption, the USGS declares a corresponding higher alert level. This alert level ranking thus offers the public and civil authorities a framework they can use to gauge and coordinate their response to a developing volcano emergency.

87 USGS-‐Volcano Hazards Program, http://volcanoes.usgs.gov/observatories/cvo/

88 Scott, W.E. et al, Volcano Hazards in the Three Sisters Region, Oregon, USGS Open-‐File Report 99-‐437, (2001).


Education and Outreach

General information on volcano hazards may be found on the USGS Volcano Hazards website: http://volcanoes.usgs.gov.

USGS Open File Reports describe the geographic extent of impacts from volcanic activity originating in the Cascades and can be found on the USGS Cascades Volcano Observatory website: http://volcanoes.usgs.gov/observatories/cvo/.


There are zero identified Volcano action item for Lincoln County; however, several of the Multi-‐Hazard action items affect the Volcano hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

Lincoln County NHMP July 2015 Page WF-1

WILDFIRE


Causes and Characteristics of the Hazard Fire is an essential part of Oregon’s ecosystem, but can also pose a serious threat to life and property particularly in the state’s growing rural communities. Wildfires occur in areas with large amounts of flammable vegetation that require a suppression response. Areas of wildfire risk exist throughout the state; central, southwest and northeast Oregon having the highest risk. The Oregon Department of Forestry has estimated that there are about 200,000 homes in areas of serious wildfire risk.

The impact on communities from wildfire can be huge. In 1990, Bend’s Awbrey Hall Fire destroyed 21 homes, caused $9 million in damage and cost more than $2 million to suppress. The 1996 Skeleton fire in Bend burned over 17,000 acres and damaged or destroyed 30 homes and structures. Statewide that same year, 218,000 acres burned, 600 homes were threatened and 44 homes were lost. The 2002 Biscuit fire in southern Oregon affected over 500,000 acres and cost $150 million to suppress.

Wildfire can be divided into three categories: interface, wildland, and firestorms.

Interface Fires

Essentially an interface fire occurs where wildland and developed areas meet. In these locations, both vegetation and structural development combine to provide fuel. The wildland/urban interface (sometimes called rural interface in small communities or outlying areas) can be divided into three categories.

1. The classic wildland/urban interface exists where well-‐defined urban and suburban development presses up against open expanses of wildland areas.

2. The mixed wildland/urban interface is more typical of the problems in areas of exurban or rural development: isolated homes, subdivisions, resorts and small communities situated in predominantly wildland settings.

3. The occluded wildland/urban interface where islands of wildland vegetation exist within a largely urbanized area.

Wildland Fires

A wildland fire’s main fuel source is natural vegetation. Often referred to as forest or rangeland fires, these fires occur in national forests and parks, private timberland, and on

There are no significant changes in the potential for Widlifre to occur in Lincoln County since 2009. Information has been updated as needed to include new incidences of the hazard since 2009 (including large wildfires). In addition, the format of the section and minor content changes has occurred.

Page WF-2 July 2015 Lincoln County NHMP

public and private rangeland. A wildland fire can become an interface fire if it encroaches on developed areas.

Firestorms

Firestorms are events of such extreme intensity that effective suppression is virtually impossible. Firestorms often occur during dry, windy weather and generally burn until conditions change or the available fuel is consumed. These events typically produce their own weather and wind events as well; as such, the high winds and dry weather are not just the conditions that drive the fire behavior. The disastrous 1991 East Bay Fire in Oakland, California is an example of an interface fire that developed into a firestorm.

Conditions Contributing to Wildfires

Ignition of a wildfire may occur naturally from lightning or from human causes such as debris burns, arson, smoking, and recreational activities or from an industrial accident. Once started, four main conditions affect the fire’s behavior: fuel, topography, weather and development.

Fuel is the material that feeds a fire. Fuel is classified by volume and type. As a western state, Oregon is prone to wildfires due to its prevalent conifer, brush and rangeland fuel types.

Topography influences the movement of air and directs a fire’s course. Slope is a key factor in fire behavior. Unfortunately, hillsides with steep topographic characteristics are also desirable areas for residential development.

Weather is the most variable factor affecting wildfire behavior. High risk areas in Oregon share a hot, dry season in the summer months and early fall with high temperatures and low humidity.

The increase in residential development in interface areas has resulted in greater wildfire risk. Fire has historically been a natural wildland element and can sweep through vegetation that is adjacent to a combustible home; additionally, fires at lower elevations historically have lower intensity. Typically it is the embers/ fire brands that ignite homes rather than the flaming front; as such, defensible space and fire resistant building materials are often the best mitigation strategies. New residents in remote locations are often surprised to learn that in moving away from built-‐up urban areas, they have also left behind readily available fire services providing structural protection.

History of the Hazard in Lincoln County The two most significant fires in Lincoln County occurred more than one hundred years ago. In 1849, the Siletz Fire claimed more than 800,000 acres between Lincoln and Polk County. The 1853 Yaquina Fire burned more than 450,000 acres of Douglas fir, Sitka spruce, and western cedar within Lincoln County. The Big Creek Fire (near Yachats) in 1936 burned buildings and a schoolhouse near a logging camp. Flames destroyed an “auto camp” near Yachats, and then continued toward the town. Some residences were lost, but the town was saved. Depoe Bay also lost homes to the flames, but firefighters kept the town from burning.


The 1987 fire season included the Shady Lane Fire and the Rockhouse Creek fire burning 6,291 acres.

Oregon Department of Forestry’s Western District includes Benton, Lincoln, Polk, and southwest Yamhill counties. Table II-‐16 displays the history of fire in the Western Oregon District since 1987. The 1500 Fire (2007, Benton County near Corvallis) accounted for the largest fire season in the district since the 1987 season.

Table II-16 Western Oregon District Fire Summary (1987-2014)

Source: Compiled from Oregon Department of Forestry Western Oregon District Annual Reports 2013, 2014

Year #&Fires Acres Cost1987 40 6,291 $3,151,1551988 37 193 $54,7701989 47 160 $42,3541990 26 28 $14,3751991 50 61 $24,5141992 53 56 $49,6831993 33 38 $21,3061994 41 34 $36,0351995 35 68 $117,5731996 51 49 $45,8901997 31 66 $12,1301998 37 190 $42,7371999 33 68 $43,8972000 43 17 $11,6602001 43 112 $35,9382002 76 279 $88,4012003 49 431 $28,0692004 18 53 $69,5492005 35 158 $40,0692006 48 50 $86,4062007 33 545 $1,341,9982008 27 13 $47,9312009 22 42 $135,0522010 21 9 $10,7572011 21 5 $24,9842012 26 12 $61,3532013 35 132 $132,5672014 36 -.- -.-20-Year-Average 36 121 $125,10310-Year-Average 30 107 $209,0135-Year-Average 28 40 $57,415


Hazard Identification Lincoln County adopted its current Community Wildfire Protection Plan (CWPP) in 2010 and utilizes it as a component of the wildfire chapter of this Natural Hazard Mitigation Plan.89 The Salishan Hills community created a separate CWPP in 2012, covering this unincorporated community northeast of Gleneden Beach.90 A CWPP seeks to protect the community from wildfire hazards by: 1) identifying and prioritizing hazardous fuel treatments; and 2) recommending measures for reducing structural ignitability. In order to achieve these goals, the CWPP identifies the location and extent of wildfire hazard areas. Developing an assessment takes into account a variety of factors including: fuel hazards, risk of wildfire occurrence, homes, businesses, and essential infrastructure at risk, other community values at risk, and local preparedness and firefighting capability. Figure II-‐19 depicts the mapped fire hazard in Lincoln County. According to this model Lincoln County ranges from a “low” to “moderate” fire hazard. Most wildfires in Lincoln County occur in the wildland/urban interface zone. Therefore, the County has a number of communities that are at risk to wildfire as shown in Table II-‐17. Ranges of the wildfire hazard are further determined by the likelihood of fire ignition due to natural or human conditions and the difficulty of fire suppression.

89 Lincoln County Community Wildfire Protection Plan, 2010, Available at: http://www.oregon.gov/odf/fire/lincolncocwpp.pdf

90 Curran, Michael. The Salishan Hills Community Wildfire Protection Plan (2012), Available at: http://www.oregon.gov/odf/FIRE/SalishanCWPP.pdf


Figure II-19 Lincoln County Fire Hazard

Source: Oregon Explorer, 2005 Communities at Risk

750,000

23.7

Map

This map is a user generated static output from the Oregon Explorer MapViewer (http://tools.oregonexplorer.info/oe_map_viewer/Viewer.html?

Viewer=OE) and is for reference only. Data layers that appear on this map mayor may not be accurate, current, or otherwise reliable.

540,000

© Oregon Explorer (http://oregonexplorer.info)

17.0

THIS MAP IS NOT TO BE USED FOR NAVIGATION

1:

WGS_1984_Web_Mercator_Auxiliary_Sphere

Miles17.00 8.52

NotesAdd your notes here

LegendCounties (2009-13)Community at Risk: Overall Rating

Low:Total weighted score of 0-9Moderate:Total weighted score of 10-16High:Total weighted score of 17+

States & ProvincesOther States and ProvincesOregon

Ocean_Basemap


Lincoln County contains four sub eco-‐regions within the coast range: the Coastal Lowlands, the Coastal Uplands, the Volcanics, and the Mid-‐Coastal Sedimentary. The Coastal Lowlands is a diverse ecoregion and contains a variety of ecosystems and natural habitats. Typically the coastal lowlands are comprised of beaches, dunes, and marine terraces. Wet forests, lakes, estuarine marshes, and tea-‐colored streams characterize the landscape. The Coastal Uplands ecoregion is characterized by headlands and low mountains surroundings the Coastal Lowlands. The Volcanics and Mid-‐Coastal Sedimentary are mainly forest areas with dense coniferous forests, steep grades, and areas of unstable soils; it also features intense anthropomorphic disturbances such as frequent logging activity and other resource extraction. The slopes in these ecoregions are prone to failure when disturbed91.

Vegetative Mapping for Fire Regime and Condition Class

The Lincoln County CWPP includes a Fire Regime and Condition Class analysis of the condition of the vegetation on the public lands managed by the agencies.

Because of the wide variability in vegetative types in Lincoln County, the Fire Regime – Condition Class approach was selected as the best method to describe the range of conditions present on the ground.

Fire Regime -‐ Condition Class considers the type of vegetation and the departure from its natural fire behavior return interval. Five natural (historical) fire regimes are classified based on the average number of years between fires (fire frequency) combined with the severity of the fire on dominant overstory vegetation. The table suggest that the county as a whole has a very long fire return interval (greater than 200 years). Although large fires are not expected to occur often, why they do occur the may burn more intensely and be more difficult to suppress.

Table II-17 Fire Regimes

Source: Adapted from Lincoln County CWPP (2010)

Fire Regime Condition Class categorizes a departure from the natural fire frequency based on ecosystem attributes. In Condition Class 1, the historical ecosystem attributes are largely intact and functioning as defined by the historical natural fire regime. In other words, the stand has not missed a fire cycle. In Condition Class 2, the historical ecosystem attributes

91 Thorson, T.D., Bryce, S.A., Lammers, D.A., Woods, A.J., Omernik, J.M., Kagan, J., Pater, D.E., and Comstock, J.A., 2003. Ecoregions of Oregon (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,500,000).

Fire%Frequency

Fire%Severity Percent Acres

1 0#$#35#years Low#and#Mixed#Severity <#1% 232 0#$#35#years Replacement#Severity 1% 5,2883 35#$#200#years Low#and#Mixed#Severity 8% 48,2484 35#$#200#years Replacement#Severity 12% 77,3335 >#200#years Any#Severity 76% 481,986

Historic%Fire%RegimeFire%RegimeGroup


have been moderately altered. Generally, at least one fire cycle has been missed. In Condition Class 3, historical ecosystem attributes have been significantly altered. Multiple fire cycles have been missed. The risk of losing key ecosystem components (e.g. native species, large trees, soil) is low for Class 1, moderate for Class 2, and high for Class 3. The table below shows that there is a significant po0rtion of the county that is either moderately departed (Condition Class 2) or severely departed (Condition Class 3) from it’s natural fire regime and associated fuel characteristics. Departure from normal conditions is an indication that an area may have higher wildfire potential. Most of the forestland east of the coast range, and in particular the northeast corner of the county, is in Condition Class 2.92

Table II-18 Condition Class

Source: Adapted from Lincoln County CWPP (2010)

While each of the fire regimes described exist in Lincoln County, Fire Regime I and Fire Regime II generally describe the forest condition that is present at the lower elevations adjacent to the more densely populated, wildland urban interface (WUI) areas of the county. The forest vegetative species shift cited above however is causing a greater presence of Fire Regime III at lower elevations with an increasing dominance of non-‐native species and increased fuels loading in those sites. This results in higher levels of fire intensity, crowning and spotting potential.

Fire Behavior

Wildland fire behavior is comprised of three components: fuels, topography and weather. While these three parameters individually define fire behavior, their interactive dynamics offer insight for effective mitigation approaches. The fire behavior triangle helps demonstrate the relationship between these three parameters.

92 Lincoln County CWPP (2010)

Condition'Class Attributes Percent Acres

Condition'Class'1

*Fire&regimes&are&within&or&near&an&historical&range.*The&risk&of&losing&key&ecosystem&components&is&low.*Fire&frequencies&have&departed&from&historical&frequencies&(either&increased&or&decreased)&by&no&more&than&one&return&interval.*Vegetation&attributes&are&intact&and&functioning&within&an&historical&range.

41% 257,385

Condition'Class'2

*Fire&regimes&have&been&moderately&altered&from&their&historical&range.*The&risk&of&losing&key&ecosystem&components&has&increased&to&moderate.*Fire&frequencies&have&departed&(either&increased&or&decreased)&from&historical&frequencies&by&more&than&one&return&interval.&This&change&results&in&moderate&changes&to&one&or&more&of&the&following:&fire&size,&frequency,&intensity,&severity&or&landscape&patterns.*Vegetation&attributes&have&been&moderately&altered&from&their&historic&ranges.

44% 277,456

Condition'Class'3

*Fire&regimes&have&been&significantly&altered&from&their&historical&range.*The&risk&of&losing&key&ecosystem&components&is&high.*Fire&frequencies&have&departed&(either&increased&or&decreased)&by&multiple&return&intervals.&&This&change&results&in&dramatic&changes&to&one&or&more&of&the&following:&fire&size,&frequency,&intensity,&severity,&or&landscape&patterns.*Vegetation&attributes&have&been&significantly&altered&from&their&historic&ranges.

12% 73,789


The fuels aspect of fire behavior takes into consideration loading, size and shape, compactness, horizontal and vertical continuity and chemical composition. Each of these parameters offers opportunities for effective hazardous fuels treatment mitigation actions.

Topography takes into account elevation and slope position and steepness, aspect and shape of the country. Areas of steep slopes and higher elevations exist in the Coast Range of Lincoln County.

The greatest potential to impact fire behavior lies with hazardous fuels management, varying in scope from defensible space around individual homes and structures to well planned, landscape scale treatments to mimic the effects of periodic low intensity fire.

Forests ecologically within the historical norm are also more fire tolerant and are less susceptible to high intensity, stand replacement fires. Ultimately, fire behavior is related to the structure of the forest fuels. Hazardous fuels treatment strategies are the subject of ongoing research efforts.93

Probability of Future Occurrence

In Oregon, wildfires are inevitable. Although usually thought of as being a summer occurrence, wildland fires can occur during any month of the year. The vast majority of wildfires burn during June to October time period. Dry spells during the winter months, especially when combined with winds and dead fuels, may result in fires that burn with intensity and a rate of spread that cause difficultly for local resources that typically don’t have their full staffing in the winter season. The threat of wildfire continues today. However, wildfire risk to human welfare and economic and ecological values is more serious today than in the past because of the buildup of flashy fuels, changes in vegetation composition over time, construction of houses in proximity to forests and rangelands, increased outdoor recreation, and a lack of public appreciation of wildfire.94

The natural ignition of forest fires is largely a function of weather and fuel; human-‐caused fires add another dimension to the probability. Dry and diseased forests can be mapped accurately and some statement can be made about the probability of lightning strikes. Each forest is different and consequently has different probability and recurrence estimates. Wildfire has always been a part of these ecosystems and sometimes with devastating effects. The intensity and behavior of wildfire depends on a number of factors including fuel, topography, weather, and density of development. There are a number of often-‐discussed strategies to reduce the negative impacts of these phenomena. They include land-‐use regulations, management techniques, site standards, and building codes. All of these have a bearing on a community’s ability to prevent, withstand, and recover from a wildfire event.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a wildfire event is “high,” meaning at least one incident is likely within the next 10 – 35 year period. Based upon available information the Oregon NHMPs

93 Science Basis for Changing Forest Structure to Modify Wildfire Behavior and Severity by Russell T. Graham, Sarah McCaffrey, and Theresa B. Jain. RMRS-‐GTR-‐120, USDA Forest Service, 2004.

94 Ibid


Regional Risk Assessment supports this probability rating for Lincoln County (although a comprehensive analysis has not been performed).95


Wildfires are a natural part of forest and grassland ecosystems. Past forest practices included the suppression of all forest and grassland fires. This practice, coupled with hundreds of acres of dry brush or trees weakened or killed through insect infestation, has fostered a dangerous situation. Present state and national forest practices include the reduction of understory vegetation through thinning, mastication, and prescribed (controlled) burning.

The Wildland Urban Interface of Lincoln County

Over the last ten years, public recognition of the term “wildland urban interface” (WUI) has become greater with increased incidences of wildland fires, loss of residences, and highly visible smoke columns. The term “wildland urban interface” describes the boundary and intermixture of structural development adjacent to and within areas dominated by wildland fire vegetation. Fire suppression tactics in interface areas, both structural and wildland, are continually adapting to provide better safety for firefighter and the public.

Each year a significant number of people build homes within or on the edge of the urban/wildland interface, thereby increasing wildfire hazards. Many Oregon communities (incorporated and unincorporated) are within or abut areas subject to serious wildfire hazards, complicating firefighting efforts and significantly increasing the cost of fire suppression.

The following are defined as “Interface Communities/Jurisdictions” within Lincoln County and have been given a risk/vulnerability rating by ODF.

95 Oregon Natural Hazard Mitigation Plan. Department of Land Conservation and Development, 2015


Table II-19 Lincoln County Communities at Risk

Source: ODF, Communities at Risk (2006)

Column headings in the above table are described below:

Risk= the likelihood of a fire occurring

Hazard= resistance to control once a wildfire starts, being the weather, topography and fuel that adversely affects suppression efforts

Protection Capability= risks associated with inadequate wildfire protection capabilities, including capacity and resources to undertake fire prevention measures.

Values= human and economic values associated with communities or landscapes.

Note: Ratings were developed statewide, so the ratings of Low, Medium, and High are relative to other communities. A Local Community Wildfire Protection Plan may assess risks differently.

The Lincoln County CWPP identifies wildland-‐urban interface communities (Figure II-‐20). The wildland-‐urban interface refers to areas where wildland vegetation meets urban developments or where forest fuels meet urban fuels such as houses. Lincoln County utilizes the following classifications to describe WUI conditions:96

Interface Condition: a situation where structures abut wildland fuels. There is a clear line of demarcation between the structures and the wildland fuels along roads or back fences. The development density for an interface condition is usually 3+ structures per acre;

96 Lincoln County CWPP (2010)

Community/Jurisdiction Risk Hazard Protection Value OverallCentral(Oregon(Coast(RFPD M M M H MDepoe(Bay M L M H MDepoe(Bay(RFPD H L M H MLincoln(County M M M H MLincoln(City H L L H MNewport M L H H MNewport(RFPD M L H H MNorth(Lincoln(RFPD L L M H MSeal(Rock(RFPD M L H H MSiletz((City) H L M H MSiletz((Reservation) H L M H MSiletz(RFPD M M M H MToledo((City) M L L H MToledo(RFPD M L M H MWaldport((City) M L H H MYachats((City) L L M L MYachats(RFPD M M M H M


Intermix Condition: a situation where structures are scattered throughout a wildland area. There is no clear line of demarcation; the wildland fuels are continuous outside of and within the developed area. The development density in the intermix ranges from structures very close together to one structure per 40 acres;

Occluded Condition: a situation, normally within a city, where structures abut an island of wildland fuels (park or open space). There is a clear line of demarcation between the structures and the wildland fuels along roads and fences. The development density for an occluded condition is usually similar to that found in the interface condition and the occluded area is usually less than 1,000 acres in size;

Rural Condition: a situation where the scattered small clusters of structures (ranches, farms, resorts, or summer cabins) are exposed to wildland fuels. There may be miles between these clusters;

High Density Urban Areas: those areas generally identified by the population density consistent with the location of incorporated cities, however, the boundary is not necessarily set by the location of city boundaries or urban growth boundaries; it is set by very high population densities (more than 7-‐10 structures per acre);

Infrastructure Area WUIs: those locations where critical and identified infrastructure is located outside of populated regions and may include high tension power line corridors, critical escape or primary access corridors, municipal watersheds, areas immediately adjacent to facilities in the wildland such as radio repeater towers; and

Non-‐WUI Condition: a situation where the above definitions do not apply because of a lack of structures in an area or the absence of critical infrastructure. This classification is not considered part of the wildland-‐urban interface.


Figure II-20 Wildland-Urban Interface

Source: Lincoln County CWPP (2010)

The Lincoln County Natural Hazards Steering Committee rated the county as having a “moderate” vulnerability to wildfire hazards; meaning between 1 – 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster. Should


several wildfires start in Lincoln County’s forests, estimates are that fifty percent of the population would be impacted, primarily by smoke and an estimated five percent of the population would suffer some property damage. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.97

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the wildfire hazard is rated #4, out of 13 rated hazards, with a total score of 205.


Threat to Life and Property

The interface between urban and suburban areas and these resource lands are producing increased exposure to life and property from wildfire. In many cases, existing fire protection services cannot adequately protect new development. Wildfires that also involve structures present complex and dangerous situations to firefighters.

Personal Choices

Many interface areas, found at lower elevations and drier sites, are also desirable real estate. More people in Oregon are becoming vulnerable to wildfire by choosing to live in wildfire-‐prone areas.98

A community at risk is a geographic area within and surrounding permanent dwellings (at least one home per 40 acres) with basic infrastructure and services, under a common fire protection jurisdiction, government, or tribal trust or allotment, for which there is a significant threat due to wildfire.

Private Lands

Private development located outside of rural fire districts where structural fire protection is not provided is at risk. In certain areas fire trucks cannot negotiate steep grades, poor road surfaces, narrow roads, flammable or inadequately designed bridges, or traffic attempting to evacuate the area. Little water during the fire season, and severe fuel loading problems add to the problem. In some areas, current protection resources are stretched thin, thus

97 Oregon Natural Hazard Mitigation Plan. Department of Land Conservation and Development. 2015

98 National Wildland/Urban Interface Fire Protection, Fire protection in the Wildland/Urban Interface: Everyone’s responsibility, Washington D.C., (1998).


both property in the interface and traditionally protected property in the forests and cities are at greater risk from fire. While the Firewise program has increased knowledge of the fire risk and preparedness for fire season however, many property owners in the interface are not aware of the problems and threats that they face, and owners in some areas have done little to manage or offset fire hazards or risks on their own property.

Drought

Recent concerns about the effects of climate change, particularly drought, are contributing to concerns about wildfire vulnerability. Unusually dry winters and hot summers increase the likelihood of a wildfire event, and place importance on mitigating the impacts of wildfire before an event takes place.

More information on this hazard can be found in the Regional Risk Assessment for Region 1 of the Oregon NHMP (2015).


Existing authorities, policies, programs, and resources include current mitigation programs and activities that are being implemented by city, county, regional, state or federal agencies and/or organizations. Local fire prevention and hazardous fuels treatment efforts have been an integral component of the local interagency coordination picture since the early 1980’s.

Oregon Department of Forestry (ODF)

The Oregon Department of Forestry is involved with local fire chiefs and fire departments as well as rural fire protection districts to provide training. Firefighters get a broad range of experience from exposure to wildland firefighting. Local firefighters can also obtain their red card (wildland fire training documentation), 3.1. 22 and attend extensive workshops combining elements of structural and wildland firefighting, defending homes, and operations experience. ODF has been involved with emergency managers to provide support during non-‐fire events as well as working with industrial partners such as timber companies to share equipment in extremely large events.

Lincoln County Comprehensive Plan and Land Use Code

Lincoln County has enacted a Comprehensive Land Use Plan and implementing land use regulations in compliance with ORS 197 and the Statewide Planning Goals. As a part of the comprehensive plan, the county has placed large portions of the county in farm and forest use zones, which serves to limit most forms of development in rural portions of the county, development that would likely increase wildfire hazard.

In addition, the county has enacted land use regulations which address fire protection for new development in both urban and rural settings, and include provisions for access, water supply, fuel breaks and similar fire safety issues.

Community Wildfire Protection Plans

Through the CWPP process, the overwhelmingly clear answer to the wildland fire mitigation question is to reduce the potential for extreme fire behavior by reducing the amount of


hazardous fuels in high-‐risk areas on both public and private lands. The Lincoln County CWPP is in need of an update; an update of the CWPP will provide additional information regarding the probability and vulnerability ratings for the county, increase the understanding of high risk communities, and provide additional mitigation measures.

Emergency Operations Plans

The county, and cities, have Emergency Operations Plans (EOP). The EOPs describe how the jurisdictions will organize and respond to emergencies and disasters. The plan includes specific information related to wildfires.


There is one (1) identified wildfire action item for Lincoln County; in addition, several of the Multi-‐Hazard action items affect the wildfire hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

Lincoln County NHMP July 2015 Page WS-1

WINDSTORM


Causes and Characteristics of the Hazard High wind events are a regular occurrence Lincoln County, particularly in exposed coastal areas. Windstorms with destructive force are less frequent, though their pattern is fairly well known. These storms form over the North Pacific during the cool months (October through March), move along the coast and swing inland in a northeasterly direction. Wind speeds vary with the intensity of the storms. Gusts exceeding 100 miles per hour have been recorded at several coastal locations, but generally lessen as the storms move inland. These storms can be very destructive as documented in the now infamous Columbus Day Storm of October, 1962. Less destructive storms can still topple trees, power lines, and cause building damage. Because coastal Windstorms typically occur during winter months, they are sometimes accompanied by heavy precipitation.

A windstorm is generally a short duration event involving straight-‐line winds and/or gusts in excess of 50 mph. Although windstorms can affect the entirety of Lincoln County, they are especially dangerous in developed areas with significant tree stands and major infrastructure, especially above ground utility lines. A windstorm will frequently knock down trees and power lines, damage homes, businesses, public facilities, and create tons of storm related debris.

Though tornadoes are not common in Oregon, these events do occasionally occur and sometime produce significant property damage and even injury. Tornadoes are the most concentrated and violent storms produced by earth’s atmosphere, and can produce winds in excess of 300 mph. They have been reported in most of the counties throughout the state since 1887. Most of them are caused by intense local thunderstorms common between April and October. Tornados are most common offshore of Lincoln County during winter months.

History of the Hazard in Lincoln County The Columbus Day storm in 1962 was the most destructive windstorm ever recorded in Oregon in terms of both loss of life and property. Damage from this event was the greatest in the Willamette Valley, where the storm killed 38 people and left over $200 million in damage. Hundreds of thousands of homes were without power for short periods, while others were without power for two to three weeks. More than 50,000 homes suffered some damage and nearly 100 were destroyed. Entire fruit and nut orchards were destroyed and livestock killed as barns collapsed and trees blew over. In Lincoln County gusts exceeded 120 miles per hour. See Table II-‐20 for a listing of additional events that have occurred in Lincoln County.

There are no significant changes in the potential for the Windstorm hazard to occur in Lincoln County since 2009; therefore, there are no significant changes in this section from the 2009 Plan. However, the format of the section, hazard history, and minor content changes has occurred.

Page WS-2 July 2015 Lincoln County NHMP

Table II-20 Lincoln County Windstorm History

Source: Taylor, G.H. and Hatton, R.R., 1999, The Oregon Weather Book, A State of Extremes: Corvallis, Oregon, Oregon State University Press; Oregon NHMP (2015)

A windstorm is generally a short duration event involving straight-‐line winds and/or gusts in excess of 50 mph. Windstorms can affect developed areas of the county with significant tree stands and major infrastructure, especially above ground utility lines.

Date Affected)Area Type Comments

October(1962

Nearly(Statewide WindWind(speeds(of(131(mph(on(the(Oregon(coast((Columbus(Day(Windstorm(Event.)(Considered(most(destructive(windstorm(in(Oregon's(history.(Damage(estimated(at($170(million(statewide.

March(1963

Coast(and(Northwest(Oregon

Wind 100(mph(gusts.(Widespread(damage.

October(1967

Western(and(Northern(Oregon

WindWind(speeds(of(100(to(115(mph.(Significant(damage(to(buildings,(agriculture(and(timber.

March(1971

Nearly(Statewide WindNotable(damage(in(Newport.(Falling(trees(took(out(power(lines.((Building(damage.

December(1973

Newport TornadoTore(off(roof(of(a(real(estate(building,(blew(out(several(windows,(damaged(two(other(roofs,(and(moved(a(garage(off(of(its(foundation

November(1984

Waldport Tornado Damage(category(5.($250K(in(property(damage.

January(1986

North(and(Central(Oregon(Coast

WindWinds(of(75mph(left(approximately(five(thousand(residents(without(power

January(1987

Oregon(Coast WindWind(gusts(to(96(mph(at(Cape(Blanco.(Significant(erosion((highways(and(beaches.)(Several(injuries.

December(1987

Oregon(Coast/(N.W.(Oregon

WindWind(speeds(up(to(60(mph(on(the(coast.(Saturated(ground(enabled(winds(to(uproot(trees.(

March(1988

North(and(Central(Oregon(Coast

WindWinds(along(the(Oregon(coast(reached(55(to(75(mph.(One(fatality(near(Ecola(State(Park.((Uprooted(trees.((

January(1990

Lincoln(County,(South(Cascades,(Pendleton

Wind/RainHigh(winds(and(heavy(snow.(Most(of(the(damage(occurred(in(Lincoln(City

February(1990

Oregon(Coast Wind Wind(gusts(of(53(mph(at(Netarts.((Damage(to(docks,(piers,(and(boats.((

January(1991

Most(of(Oregon Wind Winds(of(63(mph(at(Netarts.(57(at(Seaside.

November(1991(

Oregon(Coast( WindSlow]moving(storm.(25]foot(waves(offshore.(Buildings,(boats,(damaged.(Transmission(lines(down.

January(1993

Oregon(Coast,(Northern(Oregon

WindWinds(of(up(to(98(mph(in(Tillamook.((Widespread(damage,(esp.(Nehalem(Valley.((

December(1995

Statewide WindGusts(over(100(mph(recorded(in(Newport.((Sea(Lion(Caves:(119(mph.((Followed(path(of(Columbus(Day(Storm.((Four(fatalities,(many(injuries.((Widespread(damage((FEMA]110]DR]OR)

November(1997

Western(Oregon Wind 80(mph(winds(in(Newport.((Severe(beach(erosion.((Trees(toppled.

November(2006

Statewide Wind/Rain Winds(of(up(to(100mph

December(2007

Oregon(Coast Wind Winds(of(over(100(mph

December(2008

Clatsop,(Lane,(Tillamook,(Lincoln(Counties

Wind Intense(wind(and(rain(events.(Resulted(in(nearly($8(million(in(estimated(property(and(crop(damage(in(the(affected(counties.

February(2011

Clackamas,(Clatsop,(Crook,(Douglas,(Lincoln,(Tillamook(

Wind/(RainDR]1956;(Severe(Winter(Storm,(Wind,(Flooding,(Mudslides,(Landslides,(and(Debris(Flows

March(2012

Western(Oregon Wind/(RainDR]4055;(Severe(Winter(Storm,(Wind,(Flooding,(Mudslides,(Landslides,(and(Debris(Flows

April2014

Benton,(Lane,(Lincoln,(Linn(Counties

Wind/(RainDR]4169;(Severe(Winter(Storm,(Wind,(Flooding,(Mudslides,(Landslides,(and(Debris(Flows


As of the 2014 Oregon Residential Specialty Code, Oregon Basic Wind Speeds for 50 Year Mean Recurrence Interval, Lincoln County is listed within the highest wind speed category as an area impacted by 85-‐110 mph wind speeds.

For winter weather events (including high winds,) the National Weather Service monitors gauging stations and provides public warnings for storms and high winds.

Windstorms in Lincoln County usually occur from October to March, and their extent is determined by their track, intensity (the air pressure gradient they generate), and local terrain.99 The National Weather Service uses weather forecast models to predict oncoming windstorms, while monitoring storms with weather stations in protected valley locations throughout Oregon.100

Extreme weather events are experienced in all regions of Oregon. The regions that experience the highest wind speeds are in the Central and North Coast of Region 1. The table below shows the wind speed probability intervals that structures 33 feet above the ground would expect to be exposed to within a 25, 50 and 100 year period. The table shows that structures in Lincoln County, within Region 1, can expect to be exposed to higher wind speeds than most regions within the state.

Table II-21 Probability of Severe Wind Events by NHMP Region

Source: Oregon Natural Hazard Mitigation Plan

99 State of Oregon Natural Hazards Mitigation Plan (2015)

100 “Some of the Area’s Windstorms.” National Weather Service, Portland. http://www.wrh.noaa.gov/pqr/paststorms/wind.php

25#Year(Event((4%(annual(probability)



Region(1:Oregon'Coast 75'mph 80'mph 90'mph

Region(2:North'Willamette'Valley 65'mph 72'mph 80'mph

Region(3:Mid/Southern'Willamette'Valley 60'mph 68'mph 75'mph

Region(4:Southwest'Oregon 60'mph 70'mph 80'mph

Region(5:MidBColumbia 75'mph 80'mph 90'mph

Region(6:Central'Oregon 60'mph 65'mph 75'mph

Region(7:Northeast'Oregon 70'mph 80'mph 90'mph

Region(8:Southeast'Oregon 55'mph 65'mph 75'mph


Figure II-‐21 visualizes the maximum wind speed that structures 33 feet above the ground would expect to be exposed to; for Lincoln County that expected wind speed is less than most of the state at 85 mph.

Figure II-21 Oregon Building Codes Wind Speed Map

Source: Oregon Residential Specialty Code, 2014..


Windstorms affect Lincoln County on nearly a yearly basis. More destructive storms occur once or twice per decade. According to the State NHMP Region 1 –Coastal Oregon where Lincoln County is located is likely to experience windstorms of 75 mph during a 25-‐year cycle. It should be noted that some of the report incidents are localized events that do not affect large areas of the county or cities.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a windstorm event is “high,” meaning one incident is likely


within the next 10 – 35 year period. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.101


Many buildings, utilities, and transportation systems within Lincoln County are vulnerable to wind damage. This is especially true in open areas, such as natural grasslands or farmlands. It is also true in forested areas, along tree-‐lined roads and electrical transmission lines, and on residential parcels where trees have been planted or left for aesthetic purposes. Structures most vulnerable to high winds include insufficiently anchored manufactured homes and older buildings in need of roof repair.

Fallen trees are especially troublesome. They can block roads and rails for long periods of time, impacting emergency operations. In addition, up-‐rooted or shattered trees can down power and/or utility lines and effectively bring local economic activity and other essential facilities to a standstill. Much of the problem may be attributed to a shallow or weakened root system in saturated ground. In Lincoln County, trees are more likely to blow over during the winter (wet season). Also, irrigation wheel lines frequently get tangled in windstorms, and ultimately affect the agriculture economy.

The Lincoln County Natural Hazards Steering Committee rated Lincoln County as having a “high” vulnerability to windstorm hazards; meaning between more than 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster (particularly if utility lines are damaged). Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.102

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the windstorm hazard is rated #1, out of 13 rated hazards, with a total score of 240.


The damaging effects of windstorms may extend for distances of 100 to 300 miles from the center of storm activity. Positive wind pressure is a direct and frontal assault on a structure, pushing walls, doors, and windows inward.

Negative pressure also affects the sides and roof: passing currents create lift and suction forces that act to pull building components and surfaces outward. The effects of winds are


102 Ibid.


magnified in the upper levels of multi-‐story structures. As positive and negative forces impact and remove the building protective envelope (doors, windows, and walls), internal pressures rise and result in roof or leeward building component failures and considerable structural damage.

Windstorms can result in collapsed or damaged buildings, damaged or blocked roads and bridges, damaged traffic signals, streetlights, and parks, among others. Roads blocked by fallen trees during a windstorm may have severe consequences to people who need access to emergency services. Emergency response operations can be complicated when roads are blocked or when power supplies are interrupted.

Historically, falling trees have been the major cause of power outages in Lincoln County. Overhead power lines can be damaged even in relatively minor windstorm events.

Industry and commerce can suffer losses from interruptions in electric service and from extended road closures. They can also sustain direct losses to buildings, personnel, and other vital equipment. There are direct consequences to the local economy resulting from windstorms related to both physical damages and interrupted services.

Windstorms can be particularly damaging to manufactured homes and other non-‐permanent housing structures, which, in 2011, accounted for 14.7% of the housing units in Lincoln County (see Appendix C, Community Profile for more information), special attention should be given to securing these types of structures.




The county, cities, and utility districts routinely maintain hazard trees to keep utility lines and other infrastructure safe from damage in wind events.


Lincoln County crews actively work to locate and remove hazardous trees located along county roads. This often involves working with abutting property owners. This work is scheduled throughout the year in an attempt to reduce storm related damage. However, in Lincoln County there are a great many trees and the problem can never be eliminated.

When a Windstorm is forecasted, as one was in 2007, the road crew is placed on alert and assigned to different locations through out the county for quick response. Each crew is in radio contact and notified when a hazard has occurred. Each crew carries a power saw for removal of trees that have blown over. The vehicle (pickup) is equipped with a snow plow that allows the crew to quickly push the tree off of the road. This reduces the amount of time exposed to additional trees blowing over and opens the road quickly and efficiently.


Crews must evaluate each occurrence as to the possibility of down power lines and the potential for additional blow down.

The Oregon Building Code (both residential and other codes) sets standards for structures to withstand 80 mph winds. It is based on the International Residential Code and the International Building code.

Existing strategies and programs at the state level are usually performed by Public Utility Commission (OPUC), Building Code Division (BCD), Oregon Department of Forestry (ODF), Oregon Emergency Management (OEM), Oregon Department of Transportation (ODOT), and the Oregon Emergency Response System (OERS), who all have vital roles in providing windstorm warnings statewide.

The Public Utility Commission ensures the operators manage, construct and maintain their utility lines and equipment in a safe a reliable manner. These standards are listed on the following website: http://www.puc.state.or.us/PUC/safety/index.shtml

The OPUC promotes public education and requires utilities to maintain adequate tree and vegetation clearances from high voltage utility lines and equipment.

Oregon Emergency Management strives to reduce any damage and impacts caused by windstorms by working in partnership with PUC, ODOT. ODF promotes mitigation strategies and programs that reduce tree-‐caused damage to utility systems and highway corridors.

FEMA has recommended having a safe room in homes or small businesses to prevent residents and workers from “dangerous forces” of extreme winds to avoid injury or death. This recommendation is provided through FEMA’s resource manual: Taking Shelter From the Storm103.


There are two (2) identified windstorm action items for Lincoln County; additionally, several of the Multi-‐Hazard action items affect the windstorm hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

103 http://www.fema.gov/safe-‐room-‐resources/fema-‐p-‐320-‐taking-‐shelter-‐storm-‐building-‐safe-‐room-‐your-‐home-‐or-‐small-‐business

Lincoln County NHMP July 2015 Page WT-1

WINTER STORM (SNOW/ICE)


Causes and Characteristics of the Hazard The National Climatic Data Center has established climate zones in the United States for areas that have similar temperature and precipitation characteristics. Oregon’s latitude, topography, and proximity to the Pacific Ocean give the state diversified climates. Lincoln County is primarily located within Zone 1: Oregon Coast. The climate in Zone 1 generally consists of wet winters, relatively dry summers and mild temperatures throughout the year.104 These wet winters result in potentially destructive winter storms. Winter storms commonly produce rain, freezing rain, and high winds, and although not common, they may produce snow and ice. Severe storms affecting Oregon with snow and ice typically originate in the Gulf of Alaska or in the central Pacific Ocean. Winter storms occur over coastal Oregon regularly during November through February and often bring high winds.105

Figure II-22 Oregon Climate Divisions

Source: Oregon Climate Service,

The principal types of winter storms that occur in Lincoln County include:

104 Oregon Climate Service, “Climate of Lincoln County,”

105 Oregon State Natural Hazards Mitigation Plan (2015)

The Winter Storm hazard was not assessed in the 2009 Plan, therefore, this section provides new content to the Lincoln County NHMP.

Page WT-2 July 2015 Lincoln County NHMP

Snow Storm

Snowstorms require three ingredients: cold air, moisture, and air disturbance. The result is snow, small ice particles that fall from the sky. In Oregon, the further inland and north one moves, the more snowfall can be expected. Blizzards are included in this category. Within Lincoln County heavy snowfall is uncommon, but may occur at higher inland elevations.

Ice Storms

Ice storms are a type of winter storm that forms when a layer of warm air is sandwiched by two layers of cold air. Frozen precipitation melts when it hits the warm layer, and refreezes when hitting the cold layer below the inversion. Ice storms can include sleet (when the rain refreezes before hitting the ground) or freezing rain (when the rain freezes once hitting the ground).

Extreme Cold

Dangerously low temperatures accompany many winter storms. This is particularly dangerous because snow and ice storms can cause power outages, leaving many people without adequate heating.

History of Winter Storms in Lincoln County

Winter storms producing snow, ice, and cold temperatures occurred most notably in January 1980, January 2002, January 2004, February 2007 (DR-‐1683), December 2007 (DR-‐1733), January 2011 (DR-‐1956), January 2012 (DR-‐4055), and February 2014 (DR-‐4169). Additionally, a severe winter storm of 1950 impacted the entire state of Oregon. While many places experienced high winds, cold weather and snow.

In recent years, the challenge facing the region is the significant increase in population and growth in tourism as a local industry. Both of these shifts have generally brought new population to the area, particularly with little or no experience with living and working in severe winter weather. This condition impacts shelter, access to medical services, transportation, utilities, fuel sources and telecommunication systems. In severe winter storm conditions, travelers must seek accommodations, sometimes in communities where lodging is limited or overextended. A significant amount of supplies including food and fuel are transported into Lincoln County and in severe winter conditions, these necessities are often limited when road conditions are unfavorable. Likewise, unfavorable road conditions make emergency response operations more difficult to a more fragile population.


Winter storms occur in all parts of the county. The extent depends upon air temperatures, the level of moisture in the atmosphere, and elevation.

A severe winter storm is generally a prolonged event involving snow and cold temperatures. The characteristics of severe winter storms are determined by the amount and extent of snow, air temperature, and event duration. Severe storms have various impacts in different


parts of the county. The National Weather Service Pendleton office monitors the stations and provides public warnings on storm, snow and cold temperature events as appropriate.


The recurrence interval for severe winter storms throughout Oregon is about every 13 years; however, there can be many localized storms between these periods. Winter storms do occur in western Oregon regularly from November through February. Lincoln County experiences winter storms every few years.

Lincoln County’s Natural Hazards Mitigation Steering Committee believes that the County’s probability of experiencing a winter storm event is “high,” meaning one incident is likely within the next 10 – 35 year period. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this probability rating for Lincoln County.106


. In Lincoln County, extreme cold and heavy snow can disrupt business practices. Likewise, schools have trouble heating their buildings. The freezing and melting of snow around manholes often lead to potholes, and power outages can be frequent in adverse weather. Finally, extreme cold can cause breaks in water pipelines when temperatures drop below 10 F. Specific estimates of property and infrastructural damages for winter storm events are not available at this time.

The Lincoln County Natural Hazards Steering Committee rated the County as having a “moderate” vulnerability to winter storm hazards; meaning that more between 1 – 10-‐percent of the region’s population or assets would be affected by a major emergency or disaster. Based upon available information the Oregon NHMPs Regional Risk Assessment supports this vulnerability rating for Lincoln County.107

Risk Analysis

The risk analysis involves estimating the damage, injuries, and costs likely to be incurred in a geographic area over a period of time. Risk has two measurable components: (1) the magnitude of the harm that may result, defined through the vulnerability assessment (assessed in the previous section), and (2) the likelihood or probability of the harm occurring. Table 2-‐7 of the Risk Assessment (Volume I) shows the county’s Hazard Analysis Matrix which scores each hazard and provides the jurisdiction with a sense of hazard priorities, but does not predict the occurrence of a particular hazard. Based on the matrix the winter storm hazard is rated #2, out of 13 rated hazards, with a total score of 213.


107 Ibid.

Page WT-4 July 2015 Lincoln County NHMP


Life and Property

Severe winter storms contribute to threats on life and property. Injury and death are often associated with traffic accidents on snow and/or ice covered roads, physical exertion linked to shoveling snow and other activities involved in traveling through snow, and hypothermia from prolonged exposure to the cold. When streets and roads are affected by severe snow and ice, emergency vehicles including police, fire and medical may experience difficulty in reaching targeted destinations.

Roads

County, state, city and many private roads are routinely monitored for snow and ice. Jurisdictions and many private landowners in the rural-‐urban interface plow snow on a regular basis. Extreme snowfall and ice conditions usually place more demand on local jurisdictions, staff and budgets. Impassible roads hamper emergency response operations.

Power Lines

Extreme cold temperatures have caused power outages that interrupt services and damage property. Many outlying ranches and farms have generators and are generally self-‐ sufficient in these events. However as the general population becomes more urban, fewer numbers of people have resources such as wood stoves, a traditional back up source for heat. Rising population growth and new infrastructure, particularly tourism related, create higher probability for damage to occur from severe winter storms as more life and property are exposed to risk.

Water Lines

The most frequent water system problems related to extreme cold weather are breaks in water mainlines. Breaks occur during severe cold event impacting residents and business. Inadequate insulated potable water and fire sprinkler pipes can rupture and cause extensive damage to property. Aligned with the population growth, Lincoln County has a significant number of new residential and commercial structures which have been built under current codes that recognize severe cold weather conditions.




County and municipal Public Works and Road Departments have plans in place to mitigate and respond to severe winter storms. The plans are updated annually and routinely implemented. Utility companies have existing restoration plans that include routine upgrade


and repair, emergency restoration, and public education. Additionally, schools and employers of large scale businesses and agencies have “snow-‐day” plans.

Studded tires can be used in Oregon from November 1 to April 1. They are defined under Oregon Law as a type of traction tire. Research shows that studded tires are more effective than all-‐weather tires on icy roads, but can be less effective in most other conditions.

Highway maintenance operations are guided by local level of service (LOS) requirements. In general, classifications of highways receive more attention. Routes on the National Highway System network, primary interstate expressways and primary roads, will be cleared more quickly and completely. Critical areas like mountain passes will have snow-‐chain requirements for vehicles, and many local streets are “snow emergency routes” that will be cleared of parked cars. Parking lot and sidewalk snow removal is mostly the responsibility of property owners, sometimes by local ordinance.

Oregon Department of Transportation (ODOT) spends about $16 million per year on snow and ice removal from the state highway system though winter maintenance practices. These practices include: snow plowing, sanding roadways for ice, and using anti-‐icing chemicals.

Through the educational collaboration between the Oregon Department of Forestry and the Pacific Northwest Chapter, International Society of Arboriculture (ISA) the How to Recognize and Prevent Tree Hazards activity brochure was created.

TripCheck provides traffic incident, weather, and highway condition reports, as well as useful links to bus, rail, airport, and truck information. The website provides road condition images from approximately 140 road cameras, including over 40 in rural areas such as mountain passes where knowing road conditions can be crucial to safety: http://www.TripCheck.com/.

The National Weather Service issues severe storm watches and warnings when appropriate to alert government agencies and the public of possible or impending weather events. The watches and warnings are broadcast over NOAA weather radio and are forwarded to the local media for retransmission using the Emergency Alert System.


There are zero (0) identified winter storm action items for Lincoln County; however, several of the multi-‐hazard action items affect the winter storm hazard. An action item matrix is provided within Volume I, Section 3, while action item forms are provided within Volume IV, Appendix A. To view city actions see the appropriate city addendum within Volume III.

introduction - lincoln county, oregon · lincoln county nhmp july 2015 page ce-3!...

Documents