Beach erosion caused by sea level rise is a serious problem for people over the world. Beaches play important roles in disaster prevention, recreational use, and nurturing unique ecosystems. Beach nourishment is capable of maintaining the position of the shoreline and the natural environment. However, applying artificial nourishment to the whole beach area is not a practical method due to high costs and the large quantity sand required. There has been no framework for effective adaptation of beach nourishment to solving coastal erosion issues. In this study, we focus on the beach nourishment as an adaptation to beach erosion due to sea level rise and attempt to construct a framework for proper beach nourishment. The framework for the adaptation proposal is as follows: (i) Prediction of shoreline changes and future beach width due to sea level rise; (ii) Determination of beach width to be protected in terms of disaster prevention, ecosystem conservation and recreation respectively; (iii) Specifying vulnerable areas where the area of and width of the beach Step; (iv) Estimation of sand volume and its cost applied only to the vulnerable area. This framework was applied to Japanese beaches where the determine beach width indicated that when a beach width of more than 10 m is needed for prevention against disasters, more than 20 m for ecosystem conservation, and more than 30 m for recreation use. The volume of sand required to maintain the beach width along the whole Japanese beach varies from 61× 106 to 2,300× 106 m3, and by the use of this framework, it is possible to estimate practical nourishment volume and its associated costs for disaster prevention, ecosystem conservation and recreation use.
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