The purpose of this report is to summarize current knowledge on the geology and geomorphology of the Snoqualmie River Watershed, with emphasis on how this information relates to land use and aquatic habitat issues in the watershed. Included in the report are overviews of the current and historical land uses within the watershed, factors controlling fluvial geomorphology, an overview of the bedrock geology, glacial and post-glacial history, a description of specific reaches and tributaries within the watershed, human influences on geomorphic processes, and suggested further investigations. This report was prepared in support of the Snohomish River Basin Salmon Conservation Plan. The report is specifically intended to:

• Characterize the geologic history and active geomorphic processes in the Snoqualmie River valley;
• Provide a basis for assessing the role of active geomorphic processes in development of high-quality aquatic and riparian habitat;
• Identify circumstances in the watershed where geologic conditions or fluvial geomorphic processes pose a risk to existing or likely future land use; and
• Identify gaps in our present understanding of geologic conditions or geomorphic processes in the Snoqualmie River watershed as they relate to development of aquatic habitat or hazards to land use.

The information in this report will be used to identify existing and potential erosion, landslide, mass wasting, and sedimentation problems in the Snoqualmie Watershed, and how alteration of sediment transport has contributed to salmonid and other aquatic habitat degradation and loss. Additionally, the information will guide King County aquatic habitat protection and restoration decisions for the watershed.