City of Seattle State of the Waters 2007 Volume I: Seattle Watercourses State of the Waters 2007 Volume I Table of Contents Acknowledgments .................................................................................................................................xi Contents of the 2007 State of the Waters Report.................................................................................xiii Executive Summary.............................................................................................................................xiv Key Findings................................................................................................................................... xv Factors Affecting Seattle Watercourses .........................................................................................xvi Watershed-Scale Conditions.....................................................................................................xvi Stream-Scale Conditions ........................................................................................................xviii Biological Communities............................................................................................................ xx Part 1 Introduction .............................................................................................1 Understanding the State of Seattle Waters.............................................................................................. 1 Overview of Seattle-Area Water Bodies................................................................................................. 2 Watercourses and Streams ................................................................................................................ 2 Lakes................................................................................................................................................. 3 Estuaries............................................................................................................................................ 5 Marine Ecosystems........................................................................................................................... 5 Part 2 A Brief Primer on Stream Ecosystems......................................................7 Conditions at the Watershed Scale........................................................................................................ 10 Stream Hydrology........................................................................................................................... 10 Stream Hydrology Prior to Urban Development....................................................................... 10 Urban Impacts on Stream Hydrology........................................................................................ 11 Receiving Water Quality................................................................................................................. 12 Water Quality Prior to Urban Development.............................................................................. 12 Urban Impacts on Water Quality............................................................................................... 13 Water Quality Indicators............................................................................................................ 15 Conditions at the Stream Scale............................................................................................................. 19 Riparian Habitat.............................................................................................................................. 19 Riparian Ecosystems Prior to Urban Development................................................................... 19 Urban Impacts on Riparian Areas.............................................................................................. 19 Instream Habitat.............................................................................................................................. 20 Sediment and Wood Recruitment and Transport Prior to Urban Development ........................ 20 Urban Impacts on Sediment and Wood in Streams ................................................................... 21 Stream–Floodplain Connections Prior to Urban Development................................................. 21 Urban Impacts on Stream–Floodplain Connections.................................................................. 22 Stream Habitat and Channel Types Prior to Urban Development............................................. 22 Urban Impacts on Stream Habitat and Channel Types.............................................................. 25 Table of Contents i City of Seattle State of the Waters 2007 Volume I: Seattle Watercourses Aquatic Biological Communities ................................................................................................... 25 Salmonids in Aquatic Ecosystems............................................................................................. 25 Salmonids in Stream Ecosystems.............................................................................................. 28 Urban Impacts on Salmonids..................................................................................................... 28 Benthic Invertebrates in Stream Ecosystems ............................................................................ 28 Urban Impacts on Benthic Invertebrates ................................................................................... 29 Part 3 Assessing the State of the Waters .........................................................31 Evaluating Conditions at the Watershed Scale ..................................................................................... 33 Hydrology Assessment Methods ....................................................................................................33 Data Collection and Compilation .............................................................................................. 33 Data Analysis............................................................................................................................. 34 Water Quality Assessment Methods ............................................................................................... 35 Water Quality Indicators............................................................................................................ 36 Data Compilation....................................................................................................................... 37 Data Quality Assurance Review................................................................................................ 37 Data Analysis............................................................................................................................. 39 Evaluating Conditions at the Stream Scale........................................................................................... 49 Riparian Habitat Assessment Methods ........................................................................................... 50 Data Collection and Compilation .............................................................................................. 50 Data Accuracy and Limitations ................................................................................................. 50 Data Analysis............................................................................................................................. 50 Instream Habitat Assessment Methods........................................................................................... 51 Data Collection and Compilation .............................................................................................. 51 Data Accuracy and Limitations ................................................................................................. 52 Data Analysis............................................................................................................................. 52 Biological Assessment Methods..................................................................................................... 53 Fish Surveys .............................................................................................................................. 53 Benthic Invertebrate Sampling.................................................................................................. 54 Part 4 Conditions in Seattle Watercourses .......................................................55 Fauntleroy Creek .................................................................................................................................. 57 Fauntleroy Creek Key Findings...................................................................................................... 58 The Fauntleroy Creek Watershed.................................................................................................... 61 Watershed-Scale Conditions........................................................................................................... 62 Fauntleroy Creek Hydrology..................................................................................................... 62 Fauntleroy Creek Water Quality................................................................................................ 63 Stream-Scale Conditions ................................................................................................................ 67 Fauntleroy