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Chastain, C.E., 1976

Hydrodynamic processes and sea cliff/platform erosion, Favorite Channel, Alaska

Bibliographic Reference

Chastain, C.E., 1976, Hydrodynamic processes and sea cliff/platform erosion, Favorite Channel, Alaska: University of California, Santa Cruz, Ph.D. dissertation, 75 p., illust., 1 map.

Abstract

A bedrock platform borders the east shore of Favorite Channel, a fjord in southeast Alaska. Level lines across this platform, together with surficial geology and local hydrodynamic parameters, were analyzed in light of existing theoretical concepts and experimental data concerning the effects of waves on sea walls and rubble mound breakwaters. This analysis yielded the following conclusions: (1) The present cliff-platform configuration is the result of processes presently taking place that were initiated following retreat of Pleistocene glaciers from the inland waterways of southeast Alaska. (2) Erosion that has produced the cliff-platform configuration is primarily the result of hydraulic action, which brings about cliff retreat. (3) The residual surface left as a consequence of cliff retreat--the platform--exhibits a consistent seaward slope that is independent of the external variables of tidal range, sea level fluctuations, cliff height, and amount of overlying rock debris. As a consequence of the consistent seaward slope, the elevation of the cliff-platform junction varies directly with platform width. (4) Cliff retreat is brought about by undercutting, which is caused by the combined wave forces resulting from the backwash of the preceding wave a nd hte velocity field in the succeeding wave trough.

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