inundation map updates using a geographic information

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21st Century Dam Design

Advances and Adaptations

31st Annual USSD Conference

San Diego, California, April 11-15, 2011

On the CoverArtist's rendition of San Vicente Dam after completion of the dam raise project to increase local storage and provide

a more flexible conveyance system for use during emergencies such as earthquakes that could curtail the regions

imported water supplies. The existing 220-foot-high dam, owned by the City of San Diego, will be raised by 117

feet to increase reservoir storage capacity by 152,000 acre-feet. The project will be the tallest dam raise in the

United States and tallest roller compacted concrete dam raise in the world.

The information contained in this publication regarding commercial projects or firms may not be used for

advertising or promotional purposes and may not be construed as an endorsement of any product or

from by the United States Society on Dams. USSD accepts no responsibility for the statements made

or the opinions expressed in this publication.

Copyright 2011 U.S. Society on Dams

Printed in the United States of America

Library of Congress Control Number: 2011924673

ISBN 978-1-884575-52-5

U.S. Society on Dams

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Telephone: 303-628-5430

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U.S. Society on Dams

Vision

To be the nation's leading organization of professionals dedicated to advancing the role of dams

for the benefit of society.

Mission USSD is dedicated to:

Advancing the knowledge of dam engineering, construction, planning, operation,

performance, rehabilitation, decommissioning, maintenance, security and safety;

Fostering dam technology for socially, environmentally and financially sustainable water

resources systems;

Providing public awareness of the role of dams in the management of the nation's water

resources;

Enhancing practices to meet current and future challenges on dams; and

Representing the United States as an active member of the International Commission on

Large Dams (ICOLD).

Inundation Map Updates 1137

EMERGENCY ACTION PLANNING INUNDATION MAP UPDATES USING A GEOGRAPHIC INFORMATION

SYSTEM

Kareem A. Bynoe1 Ray Barham2

Michael Woodruff3 Shirley Williamson4

Paul F. Shiers5

ABSTRACT Emergency action planning is a critical component in the management of all medium and high hazard hydroelectric facilities. An effective emergency action plan (EAP) could mean the difference between a dam failure that results in a major catastrophe with many casualties and one where few or no casualties occur. Although having an EAP will not guarantee the prevention of casualties, it will help facility owners be reasonably prepared for a dam failure emergency. Inundation maps are a key component of an EAP. The Federal Energy Regulatory Commission (FERC) states that the purpose of an inundation map is to show the extent and timing of expected flooding from a dam failure. Although unlikely, recent dam failures serve as a reminder that adequate emergency planning and inundation maps are of importance. FERC has issued new guidelines for EAP inundation mapping that includes providing data in a geographic information system (GIS) compliant format. To implement these changes the licensee must consult with the various state and local emergency management agencies (EMAs) to understand their GIS capabilities and specific inundation mapping needs. The purpose of this paper is to present an overview of the new FERC guidelines; discuss the major advantages of GIS based inundation maps; outline the steps that Alcoa Power Generating Inc (APGI) used in their recent inundation map updates; describe the GIS capabilities of the EMAs and APGIs consultation process; and review the current progress made by APGI to provide a more usable tool that meets a wide range of needs.

1 Lead Engineer, PB Americas, Inc., Boston, MA 02116, [email protected] 2 Technical Manager, Alcoa Power Generating Inc., Tapoco Division, Alcoa, TN 37701, [email protected] 3 Civil Engineer, Federal Energy Regulatory Commission, Duluth, GA 30096, [email protected] 4 Senior Project Engineer, PB Americas, Inc., Boston, MA 02116, [email protected] 5 Senior Project Manager, PB Americas, Inc., Boston, MA 02116, [email protected]

1138 21st Century Dam Design Advances and Adaptations

BACKGROUND APGI, a wholly owned subsidiary of Alcoa Inc. (Alcoa), owns and operates two FERC-licensed projects in Tennessee and North Carolina consisting of eight hydroelectric plants. The Tapoco Project (Figure 1), located in Tennessee and North Carolina, consists of four hydroelectric plants (Santeetlah and Cheoah in North Carolina and Chilhowee and Calderwood in Tennessee) and is situated on the Little Tennessee and Cheoah Rivers. The Yadkin Project (Figure 2), located wholly in North Carolina, consists of four hydroelectric plants (High Rock, Tuckertown, Narrows, and Falls) situated on the Yadkin River. The purpose of the APGI hydroelectric plants is to supply the Alcoa smelters in the southeastern US with a sustainable source of power for the production of aluminum.

Figure 1. Tapoco Project


Figure 2. Yadkin Project

The Tapoco and Yadkin project dams have been classified as high or significant hazard, and therefore EAPs and inundation maps are required for the projects.

FERC GUIDELINES AND AGENCY COORDINATION Adequate up-to-date emergency planning is of paramount importance for all dam owners. In particular, high and significant hazard dams under FERCs jurisdiction are required to maintain emergency action plans (EAPs) that are updated annually and tested frequently. EAPs are an important part of any dam safety program and contain notification flow charts and inundation maps, establish emergency procedures, specify responsibilities, and outline actions to be undertaken prior to and during an emergency situation. The content requirements for EAPs can be found in Chapter 6 of the FERC Engineering Guidelines for the Evaluation of Hydropower Projects available from FERCs website:


(http://www.ferc.gov/industries/hydropower/safety/guidelines/eng-guide/chap6.asp) Comprehensive reviews and updates of the Tapoco and Yadkin project EAPs were conducted in 2009 as part of their five-year reprint cycle. The update of the EAPs included improving the format of the notification flow charts, re-assigning EAP responsibilities to the appropriate APGI personnel, modifying emergency procedures, and revising the inundation maps. As recommended in the FERC guidelines, APGI coordinated the EAP update activities with upstream and downstream dam owners, state and local emergency management agencies (EMAs), and federal agencies such as the National Weather Service. Through this coordination, APGI was able to update and streamline its notification flow charts and actively involve the interested adjacent dam owners and EMAs in the EAP exercises. In addition, coordination with the adjacent dam owners and EMAs played an important role in how the inundation maps were revised. A dam breach analysis for the APGI projects was completed using DAMBRK and the breach analysis results from DAMBRK (i.e. wave height and travel time) were used to create the inundation maps. The general requirements of the inundation maps are that they illustrate on the map or specify in a table the maximum inundation elevations expected for a dam failure that occurs during two antecedent flow conditions: fair weather and inflow design flood. This information, along with wave front travel times at critical locations, cross sections used for the dam breach analysis, and clearly identified inundation areas must be provided. Licensees are requested to use the most current topographic information and aerial photos available. Figure 3 is an example of an earlier Tapoco Project EAP inundation. A relatively new addition to the FERCs guidelines is a recommendation that all data (inundation boundaries and cross sections used in the analysis) used to create the inundation maps, including the maps themselves, be provided to interested EMAs and the FERC in a geo-referenced format suitable for use in a Geographic Information System (GIS). Metadata, data about the data, is also required to be submitted with the geo-referenced files. Metadata records are an integral part of a GIS by keeping a record of the source of data and pertinent information related to the contents of a GIS file. Figure 5 is an example of a metadata record for the Yadkin Project Fair Weather failure inundation file. The current guidelines also indicate that the licensee should show on each inundation map three geo-reference points to facilitate the geo-referencing of the entire inundation map in the FERCs GIS after it is converted to a digital image format. The reference points and digital version of the inundation maps are also required to be submitted to the FERC. Figure 4 is an example of a current Tapoco Project inundation map which has incorporated the FERC map recommendations.


Figure 3. Superseded Tapoco EAP inundation Map

Figure 4. Current Tapoco EAP inundation Map


Figure 5. Metadata Record, Yadkin Project Fair Weather Inundation

As the inundation maps will be used by the EMAs and adjacent dam owners, they were contacted to better understand how they utilize GIS as part of their emergency management activities, ascertain their interest in receiving inundation boundary information, and their preferred data format. APGI was pleased to learn that a majority of the EMAs and adjacent dam owners have incorporated GIS in their emergency preparedness activities and were very interested in receiving additional information from APGI to supplement the hard copy inundation maps available to them in the past EAPs. As part of the coordination with the EMAs and adjacent dam owners, APGI determined that the national spatial projection (coordinate system) required by the FERC was different than the local spatial projection system used by the EMAs and adjacent dam owners. Therefore, to facilitate the ease of sharing of GIS data between the EMAs, adjacent dam owners and APGI, a widely-used local coordinate system for each project was chosen. Data for the FERC were re-projected to the national spatial projection


before it was submitted to FERC. The re-projection of the GIS data was done within APGIs GIS.

ADVANTAGES OF INUNDATION MAPS UTILIZING GIS As part of an EAP, inundation maps are used to show the extent and timing of expected flooding from a dam failure to licensee staff, EMAs and adjacent dam owners. In the unlikely event of a dam failure, having the inundation maps readily available in a hardcopy format for reference helps to facilitate timely decisions to minimize property damage and reduce the potential for casualties. As stated in FERCs guidelines, having the inundation maps available in a GIS format presents added advantages such as: Maps can be created in formats that are interchangeable among different coordinate

systems. This was done for the APGI projects to facilitate sharing of information to the EMAs and FERC in a coordinate system native to their GIS.

It makes revising maps easier for new downstream development. Base maps showing streets and structures can be updated as more current information becomes available. During the coordination with the EMAs and adjacent dam owners, APGI issued drafts of the inundation maps to all participants to verify street names and facilitate their review to identify any critical areas that should be documented on the maps.

Different layers of inundation zones can be kept within GIS to show different flooding effects from varying breach assumptions, breaches of different structures (e.g., main dam vs. saddle dike), possible domino failures, etc. The inundation maps for the Tapoco and Yadkin projects assume a domino failure of the downstream structures due to the volume of water that would be released at each of the most upstream developments. To be conservative, at each cross section, only the maximum water surface elevation for the two failure scenarios is shown on the hard copy maps. Utilizing a GIS for the inundation maps allows APGI to prepare custom failure maps for a single dam breach under either failure scenario if needed.

It allows the maps to be easily tailored depending on the users needs. Tailoring of the maps to meet specific needs has been one of the most valuable benefits of the GIS inundation maps. As an example, GIS mapping allowed the Yadkin project the ability to efficiently create specific dam failure maps for the Falls Dam which has much lower breach elevations and does not impact downstream dam owners. Figure 6 is an illustration of the difference in inundation extent between a PMF failure of the Falls Dam vs. the maximum PMF inundation of another upstream Yadkin dam. As a second example, during the Tapoco project 2010 functional exercise, inundation maps were updated in realtime. As the functional exercise progressed the emergency operations centers were able to update their GIS with the location of incident reports, identify appropriate locations to establish temporary road closures, and identify a suitable landing site outside of the inundated areas for a rescue helicopter to land.


Figure 6. Maximum PMF Inundation Comparison, Falls Development

It allows for a general estimate of the number of people at risk from a dam failure.

With the inundation boundaries, building footprints and census statistics for a county, the EMAs, licensees, and FERC have the ability to not only estimate the number of structures that are impacted but the number of people at risk in the event of a dam failure. Figure 7 illustrates the number of structures identified to be within either the sunny day or PMF inundation zones adjacent to one of the Yadkin reservoirs.


Figure 7. Identification of Structures within the Inundation Extents

UPDATING THE INUNDATION MAPS

To assist in streamlining the inundation map updates, it was necessary to outline the steps needed to achieve the final goal of multi-functional, geo-referenced inundation maps. The steps identified for the APGI projects were as follows: Comprehensive review of previous inundation maps. A comprehensive internal

review of the previous inundation maps was undertaken to identify necessary revisions to the existing maps. The maps were also reviewed for functionality, and usability improvements such as the size of labels, the thickness of line weights, the visibility of impacted structures, etc. were noted.


Field observations. As required by the FERC, the licensee annually conducts general observations to identify any significant developments downstream of the projects that may be impacted by a dam failure. If changes to downstream development have occurred, they are incorporated into the inundation maps. If significant development has occurred that would either increase or decrease flooding in a region, a new dam breach model may be required. Although there has been residential growth downstream of the APGI project reservoirs, to date the growth is not significant enough to alter the floodplain downstream of the project such that a new dam breach model is required.

Consultation with local and state EMAs and adjacent dam owners. For both projects, APGI contacted all local and state EMAs and adjacent dam owners to inform them of the impending updates to the EAPs and the inundation maps. As part of the consultation process APGI informed the agencies and adjacent dam owners that the inundation maps would be updated in a GIS format and inquired if they used a GIS for their emergency planning activities, if they were interested in receiving inundation boundary data from APGI, and their native format.

Identify a functional coordinate system. Based on the consultation with the EMAs and adjacent dam owners, a general coordinate system was chosen to match their native GIS coordinate systems. For simplicity, the data for the FERC were exported to a FERC-compliant format after all edits and comments had been completed and incorporated into the data sets.

Acquire supplemental GIS data. APGIs GIS data repository contained detailed topographic data and limited orthophotos in the immediate vicinity of the project reservoirs, initially collected to support relicensing activities. Upon comparison of the inundation water surface elevations from the DAMBRK model results to the existing topographic data and orthophotos, it was determined that additional data would be needed to supplement what was currently available. Therefore, to produce seamless inundation maps, the best publicly available topographic data and orthophotos for both projects were downloaded from various sources.

Develop a universal base map. The base map, consisting primarily of orthophotos, transportation networks and annotation (text labels), was developed to provide supporting information to an inundation map user without detracting attention from the most important information i.e. the inundation levels at critical cross sections and flood wave travel times. It was determined early on that although true color orthophotos make for a great overall landscape picture, the color images made it difficult for the inundation boundaries to stand out from the base map. Therefore, a black and white mosaic of the orthophotos was created for the base map allowing greater flexibility for display and visualization of the inundation boundaries and travel time tables.

Develop efficient GIS processes. Automation of repeated processes minimizes production time and provides for better consistency between maps when working in a


GIS. However, as was learned during the development of the inundation maps for the Tapoco and Yadkin projects, if each map is unique from the other maps in a series there is very little automation that can be done to minimize production time.

Produce drafts for internal and external review. By allotting time in the map production process for an internal and external review of the inundation maps, the final production of the inundation maps met the needs of the EMAs and APGI. The draft maps were exported to a PDF file format for ease of distribution to all parties.

Produce final hardcopy maps for submittal to the FERC and the EAP books. Full size photo original prints were produced for reprographics purposes.

Export final data for the FERC, the EMAs, adjacent dam owners and APGI. Utilizing a GIS for management of the spatial data simplified the process of exporting the inundation data into various coordinate systems for the end user. Built into most, if not all, commercial GIS software are tools and procedures that will automatically spatially align data to the native coordinate system of the users. However, as was done for the FERC, data can be saved to any user-specified coordinate system to guarantee alignment of data in the end users native coordinate system.

SUMMARY

In summary, utilizing a GIS for the updating of the EAP inundation maps has resulted in a more functional and flexible product for dissemination of time sensitive information. An additional benefit, as a result of the consultations with the EMAs and adjacent dam owners, has been the improvement in communication between the EMAs and APGI to better coordinate responses to emergency situations and facilitate the sharing of information.

inundation map updates using a geographic information

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