The Effects of Fires on Runoff and Infiltration
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THE EFFECTS OF FIRES ON RUNOFF AND INFILTRATION IN THE NAPA RIVER WATERSHED 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 by Vivian Esmeralda Gaxiola SPRING 2018 © 2018 Vivian Esmeralda Gaxiola ALL RIGHTS RESERVED ii THE EFFECTS OF FIRES ON RUNOFF AND INFILTRATION IN THE NAPA RIVER WATERSHED A Project by Vivian Esmeralda Gaxiola Approved by: __________________________________, Committee Chair Dr. Cristina Poindexter __________________________________, Committee Chair Dr. Tyler Hatch ____________________________ Date iii Student: Vivian Esmeralda Gaxiola 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. __________________________, Department Chair ___________________ Dr. Benjamin Fell Date Department of Civil Engineering iv Abstract of THE EFFECTS OF FIRES ON RUNOFF AND INFILTRATION IN THE NAPA RIVER WATERSHED by Vivian Esmeralda Gaxiola During October 2017, the North Bay Wildfires wreaked havoc and tragedy across northern California. The North Bay Wildfires were a series of wildfires that burned over 100,000 acres and killed over 20 civilians within the Mendocino, Napa, Lake, Solano, and Sonoma counties of Northern California. The North Bay Wildfires had a disastrous impact on the natural resources within each county they burned. For engineers, environmentalists, and water managers, determining the impact that a wildfire has on a watershed within a region is crucial as it can cause a greater risk of erosion, mudslides, and flooding. Wildfires have the potential to impact the evaporation, transpiration, infiltration, runoff, water quality, and water supply of a watershed. This study focused on the impact that the North Bay Wildfires had on infiltration and runoff within the Napa River Watershed of Napa County, California. A hydrologic model was prepared to simulate infiltration and runoff within the watershed and their impact from the North Bay Wildfires using United States Army Corps of Engineering (USACE) Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS). HEC-HMS simulated three scenarios: no fires, post-fire with low severity and post-fire high severity for a 1-year storm event in March 2018. Simulating the no fire condition help demonstrate the impact of the low and high severity post-fires. The results indicate that the North Bay Wildfires increased runoff by 3.4% and could have potentially increased runoff by 12.8% if fires had been high severity. The results also indicate that the North Bay Wildfires v decreased infiltration by 2-8% and could have potentially decreased infiltration by 10-35% if fires were high severity. By considering and understanding the impacts that fires have within a watershed, engineers, environmentalists, and water managers can work together to manage and improve the water infrastructure to control the release of water, protect the water supply (i.e. stored in reservoirs and groundwater) and natural resources. _______________________, Committee Chair Dr. Cristina Poindexter _______________________ Date vi ACKNOWLEDGEMENTS First, I want to thank God for the good health, strength and wellbeing throughout these years. My family members: Joel, Blanca, Byanka, Joel Jr. and Bryan Gaxiola, for their love and moral support. My partner, Andres Guillen, for his love and advice, and always being available for me. My faculty advisor, Dr. Cristina Poindexter, for advising me with the Masters Project. My committee member, Dr. Tyler Hatch, for providing feedback on the Masters Project. Lastly, to all professors who taught me new material at Sac State. I wouldn’t have finished the Graduate Program without any of their help. vii TABLE OF CONTENTS Page Acknowledgements ................................................................................................................ vii List of Tables ............................................................................................................................ x List of Figures .......................................................................................................................... xi Chapter 1. INTRODUCTION ............................................................................................................. 1 2. BACKGROUND ............................................................................................................... 2 2.1 Napa River Watershed ........................................................................................... 2 2.2 North Bay Wildfires ............................................................................................... 4 2.3 Impact of Atlas Fire on Napa River Watershed ..................................................... 6 2.4 Impact of Nuns Fire on Napa River Watershed ..................................................... 7 2.5 Impact of Tubbs Fire on Napa River Watershed ................................................... 9 2.6 Period of Interest for Simulation: March 2018 .................................................... 10 2.7 Previous Studies ................................................................................................... 11 3. DATA COLLECTION .................................................................................................... 13 3.1 Subbasins ............................................................................................................. 13 3.2 Reservoirs ............................................................................................................ 14 3.3 Precipitation ......................................................................................................... 17 3.4 Streamflow ........................................................................................................... 20 3.5 Runoff Curve Number ......................................................................................... 21 4. MODEL ........................................................................................................................... 24 4.1 Scenario 2 (Post-Fire with Low Severity) ........................................................... 25 viii 4.2 Scenario 1 (No Fire) ............................................................................................ 29 4.3 Scenario 3 (Post-Fire with High Severity) ........................................................... 29 5. ANALYSIS OF RESULTS .............................................................................................. 30 6. CONCLUSION AND RECOMMENDATIONS .............................................................. 33 Appendix A. Subbasins ......................................................................................................... 37 Appendix B. Subbasins Summary ......................................................................................... 38 Appendix C. Precipitation Gage Data Table ......................................................................... 42 Appendix D. Precipitation Areal Distribution ..................................................................... 45 Appendix E. Land Use Cover ............................................................................................... 46 Appendix F. Soil Hydrology ................................................................................................. 47 Appendix G. Jurisdictional Dams for State of California ..................................................... 49 Appendix H. Reservoir Data ................................................................................................. 50 Appendix I. Results Table .................................................................................................... 53 References ............................................................................................................................... 62 ix LIST OF TABLES Tables Page 1. Fires in Napa River Watershed……………….… ........... ……………………………. 5 2. Rector Reservoir Information……………….… ........... ……………………………. 16 3. Curve Numbers (Pre-Fire) ..................... ………….…………………………………. 21 4. Curve Numbers Summary………….……… ..................... …………………………. 23 5. Infiltration Rates Summary……………………….……… …………………………. 32 x LIST OF FIGURES Figures Page 1. Map of Watersheds in Napa County… .... ………….…………………………………. 3 2. October 2017 Fires in Napa River Watershed ……… .………………………………. 5 3. Atlas Fire Perimeter… ............................. ………….…………………………………. 7 4. Nuns Fire Perimeter… ............................. ………….…………………………………. 8 5. Tubbs Fire Perimeter… ......................... ………….…………………………………. 10 6. Creeks, Rivers, and Major Reservoirs…………….…………………………………. 15 7. Precipitation and Streamflow Gages… .. ………….…………………………………. 18 8. Thiessen Polygon……………………………….……… .. …………………………. 20 9. HEC-HMS Background Map ……………….……… ....... …………………………. 25 10. Subbasin-1 Information ......................... ………….…………………………………. 26 11. Subbasin-1 Loss Tab… .......................... ………….…………………………………. 26 12. Subbasin-1 Transform Tab .................... ………….…………………………………. 27 13. Reservoir Information ........................................................ …………………………. 27 14. Reach Information ................................. ………….…………………………………. 27 15. Junction-1..............................................