coastal erosion battalio
TRANSCRIPT
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Coastal Hazards and Adaptation,
Pacifica Library, Pacifica, California USA
,
Sponsored by Wild Equity Institute
Bob Battalio, PE, Principal, PWAo atta o
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Speaker: Bob Battalio
Professional Civil Engineer (CA,WA,LA,OR)Coastal Processes training from UC Berkeley, 1985
Principal @ Philip Williams & Assoc., Ltd (PWA), San Francisco www.pwa-ltd.com
Worked on Pacifica Pier Abutment Repair, Pacifica State Beach Renovation, Ocean
Beach Littoral Processes Stud CA Sea Level Rise Coastal Erosion Stud FEMA
Guidelines for Pacific Coast Flood Studies
President, California Shore and Beach Preservation Association (Non profit)
Pacifica resident since 1989
Lives in Vallemar with wife Bethe and two sons Sam and Jake
Surfer
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Geo ra hic Settin
OUTLINE
Coastal Flood and Erosion Hazards,
Accelerated Sea Level Rise
Management Approaches in Pacifica
Bob Battalio @ Ocean Beach, December 1994. Copyright ©, Martha Jenkins, 1994
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e nor ern par o ac ca coas s
geologically uplifted and eroding
The southern part of Pacifica is a series of
valleys between headlands
The bluffs and headlands are eroding
Bluff / headland erosion and creek
beaches
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Daly City / Pacifica Coast: San
Andreas Fault crosses just
north of Mussel Rock.
The cliffs are comprised of theMerced Formation, poorly
consolidated sedimentary materials,
orme ur ng e a e ocene an
Pleistocene epochs. The formation
was then uplifted in the late
Quarternary Period, now up to 750
ee a ove presen sea eve .
The Merced formation largely
consists of interbedded sandstone
an s a e. e area s su ec o
land slides and wave erosion.
Mussel Rock is an outcrop of greenstone, and is part of the
Cretaceous Franciscan Complex
found on the west side of the
San Andreas Fault, in Pacifica.’
Source: USGS, on-line
rca ear y s
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Source: FEMA, Guidelines for Pacific Coast Flood Studies, 2005
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Uplifted and Erodingxamp e – a y y,
• Narrow beach backed by
~150 t u s
• Merced Formation (fine
,
weakly consolidated)
• Prone to large slumps
and landslides
• Long-term erosion rate
-. .• Future erosion predicted
to be 1.8-4.5 ft/yr, 3 ft/yr
recommended for
infrastructure setback Source: PWA, 2008
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Decadal Climate
Changes of 30 +/- years
Erosion Rate Increasing
1.0 ft/yr 1938-1995
Source: Battalio, 1996
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Source: Collins , Kayen and Sitar, 2007
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Source: Collins , Kayen and Sitar, 2007
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Layers and seeps; Manor Bluffs, Pacifica Aug 2010© Bob Battalio, 2010
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Seeps, rills and piping; Manor Bluffs, Pacifica Aug 2010© Bob Battalio, 2010
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Piping ! Manor Bluffs, Pacifica Aug 2010© Bob Battalio, 2010
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Drain Pipes
S rinkler Head
Manor Bluffs, Pacifica Aug 2010© Bob Battalio, 2010
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Talus cone; Manor Bluffs, Pacifica Aug 2010© Bob Battalio, 2010
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s or c ore nes an ros onRates
USGS
Hapke, C. and Reid, D. 2006. The National Assessment of Shoreline Change: A GIS compilation of vectorshorelines and associated shoreline change data for the sandy shorelines of the California Coast. U.S.Geological Survey. USGS Open-File report 2006-1251.
Hapke, C., Reid, D., and Borrelli, M. 2007. The National Assessment of Shoreline Change: A GIS compilation of vector cliff edges and associated cliff erosion data for the California Coast. U.S. Geological Survey. USGS Open-File report 2007-1112.
NAIP Ima er
NAIP imagery is acquired at a one-meter ground sample distance (GSD) with a horizontal accuracy thatmatches within six meters of photo-identifiable ground control points, which are used during image inspection.
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Manor
Long Term
-0.6 m/yr
o
+0.4 m/yr
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Manor
Short Term
-0.8 m/yr
o
+0.4 m/yr
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Sharp Park
Long Term
-0.7 m/yr
o
-0.3 m/yr
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Sharp Park
Short Term
-0.8 m/yr
o
-0.1 m/yr
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Sharp Park
South
Long Term
- . m yr
To
-0.1 m/yr
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Sharp Park
South
Short Term
- . m yr
To
-0.4 m/yr
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Rockaway
Long Term
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Rockaway
Short Term
About
- . m yr
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Linda Mar
Long Term
0 m/yr To
+ .
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Linda Mar
Short Term
-0.2 m/yr To
- .
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• ear ore ur one ro e
•
•Sand Transport
•Wave Runup and Overtopping
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The shoreface is shaped by wavesand water levels and is dynamic.
Width changes with volume.
Elevation of
cliff or dune junction
with the beach
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Conceptual Model of Bluff Erosion=
Bluff Recedes
,
toe elevation (relative to water levels)
Hard Bluff = Erosion potential increases at toe
and fronting beach / rock; toe elevation
Total Water Level = Tide + Runup
decreases
Tide
Run up Breaking wave momentumcauses wave setup and runup
Elevation of
cliff or dune junction
with the beach
“ ”
Bluff erosion increases with the
extent and duration of total water level above toe elevation
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Learning from Restoration Experience
More than a shoreline, the wave-shaped shore zone is on the order of
thousands of feet wide and a hundred feet tall !
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Example of wave focusing and spreading due to depth
refraction
Larger breakers
Smaller breakers
Photos: DEBORAH LATTIMORE
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Golden
Cell
Littoral Cell
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Wave Runup and overtopping defines
inland extent of coastal hazard zones(source: FEMA, 2005)
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OVERTOPPING Sharp Park Seawall, Pacifica, CA Jan 11, 2001Photos © Bob Battalio 2001
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Example Flood Hazard Mapping
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Ocean Tides and Water LevelsEXTREME HIGH WATER LEVELS
APPROXIMATE ESTIMATES
(FEET NAVD)
’- -
100-year coastal twl sheltered TBD
100-year coastal twl exposed 21 to 35’
Notes:
Swl = Still Water Level (not including waves)
Twl = Total Water Level (includes waves)
NGVD is about +2.7 feet NAVD
Values do not include future sea level riseSources: NOAA NOS, PWA and others
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ema maps
Existing Federal Emergency Management Agency (FEMA)
g ta oo nsurance ate ap
Based on 1980s conditions and standard of practice
(underestimates existing flood risk)
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New FEMA Maps will show greater flood risk
Since 1980’s (when FEMA last mapped flood hazards)
•Large coastal flood events (1982-3, 1997-98, etc.) affect risk calculation
•Sea level has risen
•Shore has eroded / receded
•New Guidelines for Pacific Coast Flood Studies
•Extreme rather than average runup and overtopping
•Momentum –Force basis for inland limit of Hi h Velocit Zone •Consider erosion during extreme event
•More accurate consideration of wave setup
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• ong erm
•Recent Historic
•
•Implications to Coastal Hazards
•Flooding
•Erosion
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Sea level - the past 300 thousand years
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–
Global average: 7 inches in the 20th century
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Accelerated Sea Level Rise Predictions
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Future sea level riseDelta Vision Blue Ribbon Task Force (2008)
B 2050: 16 in 40 cm
By 2100: 55 in (140 cm)
Used by BCDC, Coastal Conservancy, USACE,
California Climate Change Strategy
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Source: Pacific
Institute
http://www.pacinst.org/reports/sea_l
evel rise/ _
Note: First
order
approximate
estimate for
State-wide
vulnerabilit
assessment,
not for general
or local use
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Sea Level RiseRecession
depends partly on
sediment supply
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Risk - Mapping Erosion Hazards
Cliff
Dune
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Note: First
approximate
estimate for
State-wide
vu nera y
assessment,
not for general
or local use
Estimated Erosion with Sea Level Rise Source: PWA, 2009
http://www.pwa-ltd.com/about/about_news.html#OPC_Report
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of ac ca
from
North to South
Commentary !
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Daly City, Fort Funston, Lake Merced, Ocean Beach
Photos: DEBORAH LATTIMORE
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Sharp Park, Manor, Mussel Point
Photos: DEBORAH LATTIMORE
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Mussel Point, Pacifica Aug 2010 © Bob Battalio, 2010
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PACIFICA 1983
Source: Shore & Beach 7/98
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Pacifica 98
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Shore & Beach cover
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Esplanade Seawall
Photographs © Bob Battalio, 2005
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Armoring; Manor Bluffs, Pacifica Aug 2010 © Bob Battalio, 2010
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Jan 20, 2010
Photographs © Bob Battalio, 2010
ec ,
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Lands End ! Manor Bluffs, Pacifica Aug 2010 © Bob Battalio, 2010
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Sept 13, 2009 ?
March 25, 2010
Jan 6, 2010
Photographs © Bob Battalio, 2010
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Aug 2010 © Bob Battalio, 2010
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Aug 2010 © Bob Battalio, 2010
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Ocean View !
Aug 2010 © Bob Battalio, 2010
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“Shotcrete” Reinforced concrete
retaining wall, with color and
texture
Aug 2010 © Bob Battalio, 2010
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Photographs © Bob Battalio, 2010
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No dry beach below “The Bluffs at Pacifica,”, Pacifica Aug 2010 © Bob Battalio, 2010
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Sharp Park
Photos: DEBORAH LATTIMORE
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California Coastal Records Project ; 1972 Photo
Copyright © 2004-2005 Kenneth & Gabrielle Adelman - [email protected]
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California Coastal Records Project ; 2005 Photo
Copyright © 2004-2005 Kenneth & Gabrielle Adelman - [email protected]
A i g d Sh F M h l g
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Armoring and Shore Face Morphology
Potential Seawall Effects on Eroding Shore
1. Reduction of erosion behind the structure.
2. Placement losses of near shore area.
3. Passive erosion of near shore.
4. Active erosion of near shore.• Reduction of sediment supply
• Increased wave reflection
• Increased local scour
• Accelerated currents and sand transport
.
6. Change in appearance
Armoring and Shore Face Morpholog
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Armoring and Shore Face Morphology
Seawall Impacts: Placement Loss and Passive Erosion
Figure Adapted from Surfrider Foundation, “Impacts of Seawalls”
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Coastal Armoring Effects
Shoreline armoring on an erodingshore results in loss of intertidal
.
Example: Officer’s Club, Fort Ord,
Monterey Bay, CA showing beach
recovery after armoring removed and
back beach erosion.
2002
ource: a orn a oas a ecor s ro ec
2005
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Long Term Shore Morphology Changes
With Armoring (Eroding Shore)
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Beach Blvd Seawall soon after construction
Source: Geomatrix Consultants, Nov, 1987
Our Children’s future ?
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Our Children’s future ?
,
High maintenance
Public costs
No ecology
No Beach
t B o b
B a t t a l i o
P h o t o
c o p y r i g
h
Beach Blvd Seawall, winter high tide conditions
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Sharp Fairway Parks
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Sharp - Fairway Parks,
California Coastal Records Project ; 1987 Photo
Copyright © 2004-2005 Kenneth & Gabrielle Adelman - [email protected]
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Source: Peter Baye, PhD, 2009 Laguna Salada Talk
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Source: Laguna Salada Resource Enhancement Plan, PWA and others , 1992.
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Source: Peter Baye, PhD, 2009 Laguna Salada Talk
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Laguna Salada is much
smaller than in 1892
Photo: California Coastal
Records Project
Map: PWA, 1992
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Source: Laguna Salada Resource Enhancement Plan, PWA and others , 1992.
100-yr runoff flood with no dischargeabout 12.7’ NGVD (PWA, 1992)
100- r coastal flood
about 11’ NGVD –
rough estimate
Proposal to “Hold the Line” at Laguna Salada
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One of the alternatives is similar to Beach Blvd seawall which has performed poorly,
required extensive maintenance and resulted in loss of beach.
Source: Geomatrix Consultants, Nov, 1987
Proposal to “Hold the Line” at Laguna Salada
ARUP, Dec 8, 2009 recommends raising earthembankment to +30’ and armoring for about 1,800
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Proposal to Hold the Line at Laguna Salada embankment to 30 and armoring for about 1,800feet, similar to this graphic from prior GeomatrixReport, to cost about $6-$7 Million plus about$60, 000 to $70,000 per year in maintenance.
Source: Geomatrix Consultants, Nov, 1987
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Ground Water Rises with Sea Level Rise
Ocean Lake, lagoonShore
Sea Level Rise
Ground Water Rise
Sh T i i h S L l Ri
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Shore Transgression with Sea Level Rise
up and inlandShore moves up and inland
Wave runup
and overtoppingSand Transport Inland
Sea level Rise
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Coastal Levees don’t work well over long term;
oo amage r s g er ue o poor p ann ng
Inland Flooding risk
temporarily preventing shore
migration and then failingLevee
Sea Level Rise
Long Term Erosion removes beach in front of levee;
and Storms
hydraulic loading on levee increases over time;
Event Erosion fails levee; More water overtopping;
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Accreted Sediments
Sharp Park
March 18, 2010Photograph © Bob Battalio 2010
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Accreted Sediments
Sharp Park
March 18, 2010Photograph © Bob Battalio 2010
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Rockaway Cove, Hidden Cove, Mori Point
Photos: DEBORAH LATTIMORE
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Montara Mountain, Pedro Point, Shelter Cove, Linda Mar
Photos: DEBORAH LATTIMORE
Comparison of 1866 & Current
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Comparison of 1866 & Current
1866 Location
Current Location
Linda Mar – Pt San Pedro - cobble substrate with sand cover
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Photograph © Bob Battalio 2005
1. Pacifica State Beach (Linda Mar), Pacifica
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1. Pacifica State Beach (Linda Mar), Pacifica
ASBPA Best Restored Beaches 2005
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2009
Managed
Retreat Project
2004
1. Pacifica State Beach, April 15, 2005, Post Construction of Managed Retreat Project
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Photograph, courtesy of City of Pacifica
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• azar u nera y ssessmen s
•
•Regional Coastal Zone Management
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Hazard Assessments
•Map Coastal Flood and Erosion Hazard Zones•
•Existing Conditions, hazards with projection of historic trends
•Future Conditions, hazards projected for range of sea level
rise
•Assess Vulnerability•Proximity of asset to mapped hazard indicates vulnerability
, ,
•Rank Vulnerability Risk in terms of time and severity
•Develop Action Plan to prioritize and mitigate risks over time
•Assets•Property & Infrastructure
•Ecology
• ecrea on
•Community
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Re ional Coastal Zone Mana ement
•Use Boundaries Based on Coastal Processes•
•State, Federal, other special districts
•
• State (Coastal Conservancy, Ocean Protection Council,Boating and Waterways, State Parks, Caltrans, DWR)
•Federal (NOAA, NPS, USACE)
•Joint (Coastal Sediment Management Workgroup)
•Use Existing Templates / Authorities
•Local Coastal Plan, General Plans, Climate Action Plan•Redevelopment
•Parks Plans
•Public Participation
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ADAPTION: a slow, usually unconscious modification of individual and
social activity…...
ADAPTATION: a form or structure modified to fit a changed
env ronment.(Selected from Dictionary.com)
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California Strategy for Adaptation to Climate Change
What is adaptation? Adaptation involves minimizing the impacts of climate
http://www.energy.ca.gov/2009publications/CNRA-1000-2009-027/CNRA-1000-2009-027-F-ES.PDF
change already set in motion. The ultimate goal of adaptation is to enhance
society's long-term resilience to imminent climate impacts.
at s a mate aptat on trategy o prepare or t e expecte mpacts
of climate change, California has developed a statewide adaptation strategy incoordination with efforts targeting greenhouse gas mitigation policies.
. Consider project alternatives that avoid significant new development in areas
that cannot be adequately protected (planning, permitting, development, and
building) from flooding, wildfire and erosion due to climate change. The most
risk-averse approach for minimizing the adverse effects of sea level rise andstorm activities is to carefully consider new development within areas
vulnerable to inundation and erosion. State agencies should generally not
, ,
structure will require significant protection from sea level rise, storm surges,
or coastal erosion during the expected life of the structure.
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Climate change, like a wave, is a moving frame of reference
Bob Battalio @ Pacifica, Copyright ©, Franco, 2000
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Adaptation, like surfing, is navigating changing conditions
Bob Battalio @ Pacifica, Copyright ©, Franco, 2000
A d t i f d id
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And extension of a good ride.
Bob Battalio @ Pacifica, Copyright ©, Franco, 2000
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550 Kearny Street, Suite 900
San Francisco, CA
415.262.2300
www.pwa-ltd.com
Bob Battalio, PE
[email protected] 415-262-2313