Methodology of Beach Erosion Control for the Reduction of a River Delta and Its Application

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In this research project, a methodology for beach erosion control for the reduction of a river delta was investigated based on the stabilization of sanday coasts in the sedimentation system, as well as their large scale coastal behavior. The main results are summarized as1)Reduction processes of a river delta and its prediction Investigated the reduction process of the river deltaic coasts of the Kurobe, Abe, Fuji, Tenryu rivers, there clearly exist two modes of shoreline changes due to distinct types of erosive wave. The first mode is defined to be an erosive wave propagating down-coast as a diffusion phenomenon, and the second was estimated from the variation from the erosive wave and defined to be an erosive wave propagating down-coast as a wave phenomenon. We conclude that shoreline change due to beach erosion can be described as space-time change propagating down-coast as a diffusion phenomenon, upon which shoreline variation propagates as a wave phenomenon faster than the shoreli … More ne change. The erosive wave of the first mode are subject to changes as positive and negative erosive wave due to the initial and boundary conditions at the river mouth in relation to the sediment input from the river and local change in the river delta. A long-term shoreline change prediction model was established introducing the representative stormy wave and swell. Its application was made to hindcast the long-term shoreline change on the Joetsu-Ogata coast.2)Methodology for beach erosion control Based on the methodology for beach erosion control using headlands and large scale coastal behavior, a methodology for sandy beach stabilization by establishing sandy beaches was investigated. Its application was made to the Niigata coast. Pratically, in the application of the methodology the sediment source management must be made. Therefore, the fundamental problems were investigated referring to the Shizuoka coast, and principal methodology for the preservation of river deltaic coasts were proposed.3)Applications of the methodology Applications were made to the Niigata and Joetsu-Ogat coasts. As the Niigata coast headlands have been being constructed, beach erosion control by structures, beach nourishment, and formation of sandy beaches were compared by numerical simulation. The third one, methodology for beach erosion control using headlands is the most effective for the long-term sandy beach stabilization. Applications of both the methodology and long-term shoreline prediction model were made to establish a possible method for sandy beach stabilization by the formation of stable sandy beaches on the Joetsu-Ogata coast. Less