Winthrop Area (W2) Assessment of Geomorphic and Ecologic Indicators Methow River, Methow Subbasin Okanogan County, Washington U.S. Department of the Interior Bureau of Reclamation Pacific Northwest Region Boise, Idaho December 2011 U.S. DEPARTMENT OF THE INTERIOR The Department of the Interior protects and manages the Nation’s natural resources and cultural heritage; provides scientific and other information about those resources; and honors its trust responsibilities or special commitments to American Indians, Alaska Natives, and affiliated island communities. MISSION OF THE BUREAU OF RECLAMATION The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Cover Photo: View – Methow Subbasin, Washington – Bureau of Reclamation Date: May 21, 2007 Photo by: David Walsh Winthrop Area (W2) Assessment of Geomorphic and Ecologic Indicators Methow River, Methow Subbasin Okanogan County, Washington U.S. Department of the Interior Bureau of Reclamation Pacific Northwest Region Boise, Idaho December 2011 This page intentionally left blank Table of Contents Executive Summary ...................................................................................................................... 1 Overview ................................................................................................................................. 3 Introduction ................................................................................................................................. 3 Purpose of Assessment ........................................................................................................ 4 Assessment Methods ........................................................................................................... 5 Methow River Watershed ................................................................................................... 5 Regional Setting ............................................................................................................................. 7 Watershed Conditions ................................................................................................................ 10 Reach Characterization .............................................................................................................. 12 Surficial Geology .............................................................................................................. 12 Geologic Valley Confinement........................................................................................... 15 Active Channel and Floodplain Designations ................................................................... 18 Channel Gradient Determinations ..................................................................................... 20 Fish Usage ......................................................................................................................... 21 Fish Species of Interest.......................................................................................... 21 Fish Usage in W2 Reach ....................................................................................... 21 Spring and summer Chinook salmon .................................................................... 21 Migratory corridor to reach major spawning areas in upper watersheds; and also for adult holding, spawning, rearing, foraging, and potentially winter refugia .................................................... 21 Steelhead ............................................................................................................... 21 Migratory corridor to reach major spawning areas in upper watersheds; and also for adult holding, spawning, rearing, foraging, and potentially winter refugia .................................................... 21 Bull trout................................................................................................................ 21 Migratory corridor to reach major spawning areas in upper watersheds; and also for foraging and rearing .......................................... 21 Coho salmon .......................................................................................................... 21 Adult holding, spawning, and juvenile rearing; note, naturally spawning coho are increasing as a result of the Yakama Nations reintroduction effort ..................................................................... 21 Pacific Lamprey .................................................................................................... 21 Adult holding, spawning, and juvenile rearing ..................................................... 21 December 2011 i Table of Contents Reach Scale Physical Indicators ................................................................................................ 22 Reach-based Ecosystem Indicators Summary .................................................................. 22 Upper W2 Section ....................................................................................................................... 26 Channel Segment Characterization ................................................................................... 26 Channel Segment M8 ........................................................................................................ 29 Channel Morphology ............................................................................................. 29 Lateral Channel Migration .................................................................................... 29 Hydraulic Connectivity ......................................................................................... 32 Vegetation Structure .............................................................................................. 34 Aquatic Habitat...................................................................................................... 36 Summary ............................................................................................................... 38 Channel Segment M7 ........................................................................................................ 39 Channel Morphology ............................................................................................. 39 Lateral Channel Migration .................................................................................... 39 Hydraulic Connectivity ......................................................................................... 42 Vegetation Structure .............................................................................................. 45 Aquatic Habitat...................................................................................................... 47 Summary ............................................................................................................... 50 Lower W2 Section ....................................................................................................................... 50 Channel Segment Characterization ................................................................................... 50 Channel Segment M6 ........................................................................................................ 52 Channel Morphology ............................................................................................. 52 Lateral Channel Migration .................................................................................... 52 Hydraulic Connectivity ......................................................................................... 55 Vegetation Structure .............................................................................................. 57 Aquatic Habitat...................................................................................................... 59 Summary ............................................................................................................... 62 Conclusions ............................................................................................................................... 62 List of Preparers .......................................................................................................................... 65 Literature Cited ........................................................................................................................... 67 Glossary ............................................................................................................................... 69 ii December 2011 Table of Contents Appendix A – Reach-based Ecosystem Indicators Appendix B – Photographic Documentation Appendix C – GIS Databases List of Figures Figure 1. Methow watershed and W2 assessment area location map ............................................ 6 Figure 2. Generalized geologic map .............................................................................................. 9 Figure 3. Surficial geologic map of the W2 assessment area ...................................................... 14 Figure 4. Winthrop (W2) assessment area geomorphic channel segment delineations ............... 17 Figure 5. Hydraulic connectivity between the active channel and floodplain areas in the W2 Reach ............................................................................................................................................. 19 Figure 6. W2 assessment area longitudinal channel profile ........................................................