Southwest Washington shorelines accrete sediment from jetty construction, and other findings from the USGS
As part of a study of coastal beaches around the country, the USGS has published "Historical shoreline change along the Pacific Northwest coast." Among several findings, one is that 36% of beach transects in OR and WA were determined to be eroding. The average rate of long-term shoreline change for the entire PNW coast was 0.9 meter per year (m/yr) of progradation with an uncertainty of 0.07 m/yr. This rate is based on 8,823 individual transects.
Long-term shoreline change was generally more progradational in Washington than in Oregon. This is primarily due to the influence of the Columbia River and human perturbations to the natural system, particularly the construction of jetties at both the mouth of the Columbia River and at Grays Harbor, Washington. The majority of the beaches in southwestern Washington have responded to these large-scale engineered structures by experiencing dramatic beach progradation during the past century. Although these beaches are still responding to the human effects, in several locations beaches that had been rapidly prograding are now either prograding at a slower rate or eroding.
This report gives some long-term perspective on our coastal shorelines and also notes how sea level rise, storm wave heights, El Nino events, and plate tectonics may affect beaches.
Ruggiero, Peter, Kratzmann, M.G., Himmelstoss, E.A., Reid, David, Allan, John, and Kaminsky, George, 2013, National assessment of shoreline change—Historical shoreline change along the Pacific Northwest coast: U.S. Geological Survey Open-File Report 2012–1007, 62 p., http://dx.doi.org/10.3133/ofr20121007.
Hat tip to the Oregon Climate Change Research Institute and USGS.
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