Environmental Wave Barriers for Small Craft Harborsby Jeffrey F. Gilman, Nottingham & Drage Inc, Seattle, United States,
Dennis Nottingham, Nottingham & Drage Inc, Seattle, United States,
Document Type: Proceeding Paper
Part of: World Marina '91
This paper describes the history and development of the environmental wave barrier and the current planning and design being undertaken for a major expansion of the small boat harbor at Seward, Alaska. Through physical modeling, to be undertaken in the spring and summer of 1991 in Vancouver, British Columbia, we hope to further develop the wave barrier concept where moderately high waves and an environmentally sensitive site intersect. The need for environmentally acceptable breakwaters adequate to protect small craft harbors from waves up to 3 m. in height has led to the development of a new safe wave reflecting structure. Previously, similar wave 'fences' had been tested and used, but through the course of our research we have found that these barriers are not totally effective. The first 'permeable wave barrier' that we designed was successfully installed at a U.S. Coast Guard facility in Oregon in 1980. Continued monitoring of the facility has verified the as-designed performance of the breakwater, even in severe storm events exceeding the original design parameters. As it was environmentally desirous to allow for circulation and fish passage, the breakwater's wave board, supported by steel piling, was not extended completely to the ocean bottom; hence the terms 'permeable' or environmental' wave barrier. The further development of the environmental wave barrier for higher wave heights necessitates the incorporation of high-capacity tension piles into its design. While the first wave barrier utilized conventional steel pipe piles, the next facility will use the spin-fin pile. The spin-fin employs fins welded to pipe piles at an angle; thus, the pile actually screws into the ground during driving. As a result, pile pull-out capacity is greatly increased; especially under repeated failure loads. This paper includes a brief discussion of spin-fins.
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