Engineering response to shore erosion near Grays Harbor, WA, USA

Problems caused by shoreline change near the Grays Harbor entrance on Washington's Pacific coast have recently progressed to an extent that required engineering analysis and design. Erosion is occurring at three locations, South Beach and North Beach (Pacific Ocean beaches south and north of the entrance, respectively) and at Half Moon Bay inside the entrance. Analysis revealed that the erosion at South Beach and North Beach is an expression of change in the ebb tidal shoal, and the consequent change in nearshore wave conditions, which are remolding the nearshore profile. Half Moon Bay erosion is caused by progressive changes in wave climate and sediment supply resulting from southward migration of the navigation channel in the entrance. Engineering studies resulted in different structure types, design lives, and intended interaction among waves, sediments, and structures at the three erosion sites. The analyses and design considerations are described for each.