Longshore Transport of Sediment in Freshwater Bay, West of Port Angeles

Abstract

Using digital photographs, this study investigates sediment movement eastwards by the dominant northwest swell in Freshwater Bay, WA. Twenty samples were taken at five locations and analyzed with the Cobble cam analysis package. It was found that sand and smaller pebbles were more prevalent on the western updrift shore than on the delta face and that no silt and clay were found on the foreshore. Sand was not evident on the most eastern site and mean sediment grain size increased eastward. Wave rays hit the western face of the delta orthogonal to the shore and result in more pronounced cusps in the eastern direction. The westerly portion experiences oblique waves and results in longshore transport eastward in Freshwater Bay. Pacific Ocean swell from the west had the most impact while local wind-generated waves from the northeast and northwest had the least. Pebbles were selectively moved by the wave regime for each section of beach. All the sediment along the western delta was removed and indicates that longshore transport is sediment starved.