LITTORAL BYPASSING AND BEACH RESTORATION IN THE VICINITY OF FORT HUENEME CALIFORNIA

William J. Herron, Robert L. Harris

Abstract


Port Hueneme Harbor, California, constructed in 19^0, resulted in the average annual erosion of 1,200,000 cubic yards from the shoreline downcoast of the harbor. The cause was diversion by the north jetty of the harbor of littoral sand movement into the Hueneme canyon, A sand bypass system was established in i960 - 6l by construction, one mile upcoast, of Channel Islands Harbor fronted by an offshore breakwater 2,300 feet in length and located on the 30-foot-depth contour. This breakwater serves a dual function of sheltering the harbor entrance and acting as a littoral sand trap. Three cycles of biennial littoral sand bypassing havebeen successfully completed resulting in supply of 11,000,000 cubic yards of sand to the eroding shoreline at an average annual cost of $0.40 per cubic yard, including annual maintenance and amortization of structures. Comparison of design of the structure to the impounding characteristics experienced during three bypass cycles indicates that the dimensions and capacity of a sand trap formed by an offshore breakwater can be based upon the diffraction patterns of prevailing wave trains at the two ends of the structure and is independent of the depth and dimensions of the entrapment area. Rate of impoundment is equal to the rate of littoral drift at Port Hueneme.

Keywords


littoral bypassing; beach restoration; Port Hueneme

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