Net Shore-drift and Artificial Structures Within Grays Harbor, Willapa Bay, and Mouth of the Columbia River, Washington

Download or read book Net Shore-drift and Artificial Structures Within Grays Harbor, Willapa Bay, and Mouth of the Columbia River, Washington written by Berenthine Patrice Thomas and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Net shore-drift, the overall result of sediment transport in the littoral zone, was studied along the shore within Grays Harbor, Willapa Bay, and mouth of the Columbia River, Washington. The length and direction of drift cells, which are discrete sediment compartments, was delineated using geomorphologic and sedimentologic indicators. Eight drift cells were identified in Grays Harbor, seven within Willapa Bay, and three along the section of the Columbia River shore studied. Drift cell lengths range from 200 m to approximately 6 km with an average of 1.5 km. Net shore-drift directions vary considerably with maximum fetch identified as the most important factor in sediment transport. Local fetches within the embayments are responsible for transport within one-half of the drift cells, while open ocean fetch accounts for transport in one-third of the drift cells. Transport within the remaining one-sixth of the drift cells is most likely due to a combination of local and open ocean fetch. The sediment within the drift cells is mainly derived from re-working of sand dunes along the shore. The majority of the shore in the study areas is characterized by no appreciable net shore-drift. This lack of drift is due to extensive tidal flats, salt marsh vegetation in close proximity to the shore, and a lack of appropriate sediment in these estuarine environments. The extent of structures along the shore of these areas was also identified. Human modification along the shore includes the use of jetties, groins, bulkheads, and breakwaters. All of these structures consist of riprap. In a few locations, other materials were used in conjunction with the riprap. Shore defense structures are most extensive along the section of the Columbia River studied but are also prevalent along the shore within Grays Harbor and Willapa Bay. The largest structures are the massive jetties at the mouth of the Columbia River and at the entrance to Grays Harbor.