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Regional Setting

The Columbia River littoral cell extends from Tillamook Head, Oregon to Point Grenville, Washington and has four major concave-shaped, offset sections of prograded shoreline separated by the Columbia River and two large coastal plain estuaries of Willapa Bay and Grays Harbor.  The sediment budget for the region is governed by the Columbia River, the second largest river in the United States and the largest river that discharges to the northeastern Pacific Ocean, with modern mean annual water discharge of 6,800 m3 s-1.  Wide and gently sloped beaches throughout the littoral cell front barrier-beach plains that have developed over the past several thousand years with large linear dune ridges and broad dune fields and swales.  The prograding barrier beaches along this tectonically active coastal margin have experienced episodic erosion and sudden 1 to 2 m subsidence events associated with large earthquakes of approximately 500 yr recurrence intervals.

The Columbia River littoral cell from Tillamook Head, Oregon to Point Grenville, Washington. Click on the image to link to a printable version.

Spilling breaking waves over wide surf zones, with multiple longshore bars are characteristics of the nearshore environment.  Infragravity (low frequency) energy and rip currents typically dominate the inner surf zone and complex nearshore circulation patterns are also common.  Tides throughout the cell are mixed semi-diurnal with a 2 to 4 m range.  The wave climate is large with annual mean significant wave heights of 2 m and peak periods of 10 s, and extreme winter storms producing significant wave heights of over 7 m and peak periods over 17 s.  Strong El Niņo events occurring at decadal frequency influence wave patterns, particularly direction, affecting longshore sediment transport.

Ecology - SEA Program | USGS - Coastal & Marine Geology

This is http://www.ecy.wa.gov/programs/sea/swces/overview/setting.htm
Maintained by CMAP, Washington Department of Ecology
Address questions and comments to George Kaminsky
Modified 22 Mar 2012