Scoggins Dam in northwest Oregon lies within the Gales Creek fault zone (GCF), a northwest-striking system of active faults forming the boundary between the Coast Range and the Tualatin Valley about 25 km east of Portland, Oregon. Geologic mapping published in 2020 shows the dam to lie within a block-faulted releasing stepover between the right-lateral, NW-striking Scoggins Creek and Parsons Creek strands of the GCF. The Scoggins Creek strand is presently mapped beneath the existing dam about 200 m north of the south abutment. Preliminary results from paleoseismic trenching by the U.S. Bureau of Reclamation, Portland State University, and the U.S. Geological Survey indicate that these two major fault strands have had multiple surface rupturing earthquakes in the Holocene. To confirm the accuracy of the 2020 geologic map and the geometry of the GCF in the releasing stepover region, we completed additional geologic mapping of the dam, reservoir, and an alternative dam site downstrea ...

Link to the ScienceBase Item Summary page for the item described by this metadata record. Service Protocol: Link to the ScienceBase Item Summary page for the item described by this metadata record. Application Profile: Web Browser. Link Function: information

Coastal erosion is a widespread process along most open-ocean shores of the United States that affects both developed and natural coastlines. As the coast changes, there are a wide range of ways that change can affect coastal communities, habitats, and the physical characteristics of the coast-including beach erosion, shoreline retreat, land loss, and damage to infrastructure. The U.S. Geological Survey (USGS) is responsible for conducting research on coastal change hazards, understanding the processes that cause coastal change, and developing models to forecast future change. To understand and adapt to shoreline change, accurate information regarding the past and present configurations of the shoreline is essential. A comprehensive, nationally consistent analysis of shoreline movement is needed. To meet this national need, the USGS is conducting an analysis of historical shoreline changes along open-ocean coasts of the United States and parts of the Great Lakes. As more data are gathered, periodic updates are made, which provide information that can be used in multidisciplinary assessments of global change impacts.