Walla Walla River, Mill Creek, United States Department of and Coppei Creek Agriculture Forest Geomorphic Assessment Service May 2010 Walla Walla County Conservation District and U.S. Forest Service, TEAMS Enterprise Unit Prepared by: Thomas Brian Bair, Project Fisheries Biologist, Forest Service TEAMS Enterprise Unit Michael McNamara, Hydrologist/Geologist, Forest Service TEAMS Enterprise Unit Anthony Olegario, Fisheries/Engineer, Forest Service TEAMS Enterprise Unit Chad Hermandorfer, Hydrologist, Forest Service TEAMS Enterprise Unit Katherine Carsey, Botanist, Forest Service TEAMS Enterprise Unit Compiled: April, 2010; Revised: May 2010 Acknowledgements: Thanks to all the helpful staff at the Walla Walla County Conservation District including Rick Jones, Mike Denny, Jonathon Thompson, Audrey Ahman, and others. Thanks also to landowners Ron Johnson and other landowners for allowing us access to their property and cooperating with our study. Thanks lastly to all the U.S. Forest Service TEAMS members who contributed to this document. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-3272 (voice) or (202) 720- 6382 (TDD). USDA is an equal opportunity provider and employer. Walla Walla River, Mill Creek, and Coppei Creek Geomorphic Assessment Table of Contents Executive Summary ........................................................................................................................ 1 Summary of Findings ................................................................................................................. 1 1. Introduction and Purpose ............................................................................................................ 3 Project Area ................................................................................................................................ 3 2. Methods ...................................................................................................................................... 5 Channel Surveys and Sediment .................................................................................................. 5 Cross-section Survey and LiDAR .............................................................................................. 5 Riparian Vegetation Surveys ...................................................................................................... 5 3. Watershed Conditions ................................................................................................................. 7 Streams and Riparian Areas ....................................................................................................... 7 Streams, Communities, and Land Uses .................................................................................... 10 Walla Walla River ................................................................................................................ 10 Mill Creek ............................................................................................................................. 11 Coppei Creek ........................................................................................................................ 13 Fisheries ................................................................................................................................... 15 Geology and Soils .................................................................................................................... 18 4. Assessment Reach Conditions .................................................................................................. 21 Hydrology ................................................................................................................................ 21 Climate.................................................................................................................................. 21 Surface Water ....................................................................................................................... 21 Channel Forming Flows and Floods ..................................................................................... 25 Hydrology and Climate Change ........................................................................................... 28 Hyporheic Flows ................................................................................................................... 28 Channel Conditions .................................................................................................................. 29 Confinement, Entrenchment Ratio, and Floods .................................................................... 36 Channel Properties: Width/Depth, Slope, Substrate ............................................................. 37 Large Woody Debris ............................................................................................................ 47 Sediment ............................................................................................................................... 50 Bank Stability ....................................................................................................................... 57 Aerial Photo Comparisons .................................................................................................... 57 Floodplain Mapping Analysis............................................................................................... 60 Riparian Vegetation .............................................................................................................. 69 5. Recommendations – Assessment Reaches ............................................................................... 79 Walla Walla River Goals .......................................................................................................... 80 Short-Term Objectives (5 years) .......................................................................................... 80 Long-Term Objectives (5 to >20 years) ............................................................................... 81 Recommended Actions / Strategy for Walla Walla River.....................................................81 Proposed Projects ................................................................................................................. 82 Mill Creek Goals ...................................................................................................................... 83 Short-Term Objectives (5 years) .......................................................................................... 84 Long-Term Objectives- (5 to >20 years) .............................................................................. 84 Recommended Actions / Strategy for Mill Creek.................................................................85 Proposed Projects ................................................................................................................. 86 Coppei Creek Goals ................................................................................................................. 87 Short-Term Objectives (5 years) .......................................................................................... 88 Long-Term Objectives (5 to >20 years) ............................................................................... 89 Recommended Actions / Strategy for Coppei Creek.............................................................89 Proposed Projects ................................................................................................................. 89 i Walla Walla River, Mill Creek, and Coppei Creek Geomorphic Assessment 6. References ................................................................................................................................ 91 7. Glossary .................................................................................................................................... 93 8. Appendices ............................................................................................................................... 99 Appendix A: Riparian Planting Guidelines .............................................................................. 99 Appendix B: Reference Condition Plant List ......................................................................... 105 Appendix C: Reach-Scale Existing Geomorphic Characteristics and Channel Geomorphic Data Summary ........................................................................................................................ 106 List of Tables Table 1. Geologic events in the Walla Walla, Mill Creek, and Coppei Creek assessment areas, Walla Walla County, Washington ........................................................... 19 Table 2. The bankfull, 50-, 100-, and 500-year flood