THE NEGATIVE EFFECT OF NOURISHMENT AT A STEEP ROCKY BEACH AND COUNTERMEASURES:CASES ANALYSIS

This paper introduces 4 domestic and oversea cases of nourishment at steep rocky beaches, where the coast, which faces deep water, is steep. In such cases, offshore waves approach the coast without bottom friction and energy dissipation. As a one-off breaking, they strongly erode the coast, and create erosional landforms without sediment or with a narrow skirt beach near the high tide line under the sea cliff. It is hard to carry out open sand nourishment at such a beach. Some of our domestic nourishment projects were suffered from the severe loss of sand. We made introductions in this paper to the model of combining the groins and continuous offshore submerged-dikes and the model of combining the groins and double parallel offshore submerged-dikes, which may stop the loss of sand nourished at foreshore flow-out, and promote the dissipation of the offshore wave energy and then stop the littoral drift to protect the nourished beach from erosion. It proves that it is possible to construct a broad artificial beach at a steep rocky beach with the support of specific combination of hard structures.