The Columbia River is the primary source of sediments for the beaches between Tillamook Head, Ore., and Point Grenville, Wash., also called the Columbia River Littoral Cell (CRLC). During the past century, the shoreline along the southwest Washington coast has accreted substantially, providing an expanding land mass favorable to development. Recently, however, that growth trend has slowed throughout the region and has reversed in certain areas, yielding dramatic erosion rates. State and federal agencies have invested millions on erosion protection measures along the coast. However, the causes and timescales of erosion remained speculative until a 1997 Southwest Washington Coastal Erosion Study that prompted the states to begin monitoring CRLC beaches.