Regional Beach Sand Volumes of the Pacific Northwest, USA

by Curt D. Peterson, Portland State Univ, Portland, United States,
Don J. Pettit, Portland State Univ, Portland, United States,
Mark E. Darienzo, Portland State Univ, Portland, United States,
Phillip L. Jackson, Portland State Univ, Portland, United States,
Charles L. Rosenfeld, Portland State Univ, Portland, United States,
A. Jon Kimerling, Portland State Univ, Portland, United States,



Document Type: Proceeding Paper

Part of: Coastal Sediments

Abstract:

Eight small littoral cells ranging from 5-60 km in length have been surveyed by beach profiling and seismic refraction to establish active beach sand volumes in the Pacific Northwest region. Regional tectonic uplift in this convergent margin setting has produced shallow wave-cut platforms (1-3 m depth subsurface) under beaches of variable width (150-450 m). Thicker beach deposits are located in barrier spits and over wave-cut platforms lowered by local erosion and tectonic down warping. Cross-section areas of beach transects range from 15 to 3,425 m², while cross-section areas above MHHW (an indicator of shoreline erosional susceptibility) range from 0 to 528 m². Maximum MHHW cross-section areas south of bounding headlands and jetty structures in six of the eight cells suggest a small, net northward littoral transport in the study region. Total cell sand volumes range from 0.6 ? 10⁶ to 90 ? 10⁶ m³ while longshore normalized, total sand volumes (cubic meters per meter shoreline) range from 77 to 1,489 m³ in the eight study cells, indicating extremely variable sand supply in this complex coastal zone.

Subject Headings: Sandy soils | Sand (hydraulic) | Littoral drift | Beaches | Seismic tests | Littoral zones | Erosion | United States | Pacific Northwest

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