WAVES STORMS   EROSION Ocean Shores Ft. Canby Washaway Beach Westport What's happening dams jetties

Jetties and shoreline change In the early 1900s, jetties were built at the entrances to the Columbia River and Grays Harbor. These jetties were designed to scour out sandbars and keep navigation channels open. Beaches, inlet entrances, and the nearby sea floor are still changing as a result of jetty construction over a century ago. River deltas scoured The jetties narrowed inlets and increased tidal currents. These currents flushed sand out of tidal deltas. Beach growth and erosion Over decades, sand from the scoured deltas accumulated, causing beaches near the jetties to grow. Campgrounds and condominuims were built on this newly accreted land. The delta sand is now gone and beaches near the jetties are experiencing erosion. Erosion and accretion near jetties   Where there is net littoral drift, jetties can block the flow of sand, causing erosion and accretion. North Jetty, Grays Harbor Built 1908--1916. For decades, the North Jetty trapped sand, causing Ocean Shores to grow. Many miles of land formed. In recent years, erosion has occurred near the jetty on North Beach. South Jetty, Grays Harbor Built 1898--1902. Following jetty construction, South Beach accreted. In recent decades, erosion has occurred near the jetty at Westhaven State Park and along South Beach. North Jetty, Columbia River Built 1908--1916. Following jetty construction, the Fort Canby beach grew rapidly. The beach reached its maximum distance seaward in 1942, then began to erode. Grays Harbor Entrance: delta & sea floor changes   Construction of the jetties in the early 1900s changed the Grays Harbor bar, shoals, and the adjacent coast. After jetty contruction, the inlet channel and the bar deepened; offshore shoals eroded and moved onshore; beaches 6 to 19 miles away grew or accreted for several decades. Grays Harbor: before jetty construction, 1900 Ebb-tidal currents moved sand out of the estuary. Longshore currents carried this sand north and south along the coast and deposited it on beaches.   Grays Harbor: after jetty construction, 1999 Sand from the ebb-tidal delta piled onshore, creating new land, a deeper nearshore zone, and a steeper shoreface. Sources: The Southwest Washington Coastal Erosion Study. Maarten Buijsman, George Kaminsky, et al., Regional Sediment Budget Analysis of the Columbia River Littoral Cell, USGS.   Southwest Washington Coastal Erosion Study. A recent study of Washington's coastal processes and shoreline changes.

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