DAM BREACH MODEL OF LAKE ANZA DAM USING HEC-RAS A Project Presented to the faculty of the Department of Civil Engineering California State University, Sacramento Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Civil Engineering (Water Resources Engineering) by Robert Joseph Greenberg SPRING 2018 DAM BREACH MODEL OF LAKE ANZA DAM USING HEC-RAS A Project by Robert Joseph Greenberg Approved by: __________________________________, Committee Chair Cristina Maria Poindexter, P.E., Ph.D. __________________________________, Second Reader Scott Meyer ____________________________ Date ii Student: Robert Joseph Greenberg I certify that this student has met the requirements for format contained in the University format manual, and that this project is suitable for shelving in the Library and credit is to be awarded for the project. __________________________, Graduate Coordinator ___________________ Saad Merayyan, Ph.D. Date Department of Civil Engineering iii Abstract of DAM BREACH MODEL OF LAKE ANZA DAM USING HEC-RAS by Robert Joseph Greenberg For this project, HEC-RAS was used to create an inundation map for the failure of the Charles Lee Tilden Dam in Berkeley, California. A two-dimensional HEC-RAS model was created to simulate the Lake Anza Reservoir, C.L. Tilden Dam, and surrounding topography. HEC-RAS used the Shallow Water Equations to calculate hydraulic characteristics along the most likely path of dam breach flow. The inundation map, which shows the areas which would be adversely affected by the breach of the dam, was created using the maximum depth of water at each point along the dam breach flow’s path. This method can effectively predict the areas which will be inundated by water released by a dam failure and allows evacuation personnel to make informed decisions about which populated areas to evacuate in the case of such an emergency. _______________________, Committee Chair Cristina Maria Poindexter, P.E., Ph.D. _______________________ Date iv ACKNOWLEDGEMENTS I would like to express my deepest appreciation to all those who supported me in the completion of this report. I would like to express my deepest gratitude to my grandmother, Lu Charlotte, without whom, I wouldn’t have been able to attend graduate school. Furthermore, I would like to thank my parents for supporting me throughout this endeavor. A special thanks to Lara Schenck for the helping me not only with the report, but also supporting me through the entirety of my time in school. For assisting me in generating a usable terrain file, I’d like to thank fellow graduate student, Robert Sherrick. I’d also like to thank Luis Mercado, who assisted me with running the experiment and writing the report. Last, but not least, I’d like to thank Cristina Maria Poindexter for her support as my advisor through this project. v TABLE OF CONTENTS Page Acknowledgements .................................................................................................................. v List of Figures ........................................................................................................................ vii Chapter 1. BACKGROUND ................................................................................................................ 1 2. METHODS ........................................................................................................................ 5 3. RESULTS ...................................................................................................................... 15 4. CONCLUSIONS .............................................................................................................. 24 APPENDIX A. Inundation Maps at Different Time Intervals ............................................ 25 References .............................................................................................................................. 28 vi LIST OF FIGURES Figures Page 1. Oroville Dam Spillway Failure, February 2017 .... .……………………………….1 2. Diagram of Jurisdictional Dam Criteria ........................... ……………………………. 2 3. Lake Anza ................................................ ………….………………………………….3 4. C.L. Tilden Dam................................................................... …………………………. 4 5. HEC-RAS Geometry Editor ........................................ .………………………………. 7 6. Storage Area Editor ........................................................ ……………………………. 10 7. Connection Editor ................................. ………….…………………………………. 11 8. Dam Breach Parameters ..................................................... …………………………. 13 9. Trees growing on the dam face ................................. .………………………………. 14 10. Maximum Depth Map .................................................... ……………………………. 15 11. Depth Vs. Time at Curran Trailhead ................................. …………………………. 16 12. Depth Vs. Time at Little Farm ........................................... …………………………. 17 13. Extent of Flooding 2 hours after dam breach ............ .………………………………. 18 14. Maximum Extent of Flooding at Interstate 80 Overcrossing .………………………. 19 15. Interstate 80 Freeway ......................................................... …………………………. 20 16. Interstate 80 Freeway at San Pablo Exit ............................. …………………………. 20 17. Max Depth along Interstate 80 Freeway ................... .………………………………. 21 18. DSS Wise Results ........................................................ ……………………………. 22 vii 1 1. BACKGROUND Figure 1: Oroville Dam Spillway Failure, February 2017 During the winter of 2017, there was record rainfall throughout the State of California leading to proportionately large runoff. California’s reservoirs, which had been practically empty in previous years due to prolong drought were rapidly filling and the California Department of Water Resources (DWR) needed to release water as to not overtop the reservoirs. Lake Oroville, the second largest reservoir in California, was one such dam and its spillway was damaged, critically curtailing the amount of water that could be released through conventional means. This situation led to the eventual overtopping of the concrete weir at the emergency spillway and extensive scouring of the hillside below the spillway (see Figure 1). As this was unfolding, authorities in downstream communities evacuated over 180,000 people for fear that a catastrophic 2 damage failure would lead to massive loss of life (Independent Forensic Team, 2018). After the evacuation was lifted and several of the communities that had been evacuated filed lawsuits, there were doubts about the necessity of evacuating so large a population. It was revealed that so large an evacuation was made due to lack of information on the area that would be inundated by a catastrophic failure of the dam thus necessitating the authorities to take a conservative approach to the evacuation. As a result of this revelation, the California State Legislature amended the California Water Code by adding section 6161 requiring all owners of jurisdictional dams to create inundation maps and make them available to the public. Figure 2: Criteria for Jurisdictional Dams. (Department of Water Resources, State of California, n.d.) Jurisdictional dams are defined as any dam that is higher than 6 feet impounding 50 or more acre feet of water or higher than 25 feet impounding more than 15 acre feet of water as shown in (see Figure 2) (Department of Water Resources, State of California, n.d.). 3 Figure 3: Lake Anza To explore the methods used by engineers to generate inundation maps, I chose to model the failure of the Charles Lee Tilden Dam which impounds Lake Anza (see Figure 3), a small lake in the San Francisco Bay Area’s Tilden Park. The lake was a favorite swimming hole for me as a child and its listing on the Department of Water Resources Jurisdictional Dams list with a hazard rating of “high” caught my interest (Department of Water Resources, State of California, 2017). The dam (see Figure 4) is placed high in the Berkeley-Oakland Hills along Wildcat Creek which runs north from the saddle created by Vulmer and Grizzly Peak till it exits Wildcat Canyon just east of Interstate 80 before flowing into San Pablo Bay to the northwest. The majority of Wildcat 4 Creek is within Tilden Regional Park, part of the East Bay Regional Parks District and is accessible via fire trails and paved roads in certain locations. Figure 4: C.L. Tilden Dam 5 2. METHODS The data required to use the model at a rudimentary level is topography and information on the dam and its reservoir. The topography can be found in a number of ways; it can either be manually entered or generated using a terrain file from an outside source. Manually entering data involves drawing the river reaches then generating a series of cross sections to establish a hydraulic profile, but doing so is tedious and prone to error. An electronic terrain file, generated either through Light Detection and Ranging LIDAR, satellite mapping, or surveys is quicker and generally more accurate. For this experiment, an electronic terrain Digital Elevation Model (DEM) file downloaded from the United States Geologic Survey (USGS) website was used. This terrain file did not include the topography below the surface of Lake Anza (the bathymetry). The USGS DEM file also came with a projection file allowing for spatial projection in mapping software. Sacramento State graduate student Robert Sherrick, who is currently completing his culminating project