宮古島下地町前浜海岸浸食はなぜ始まった？　災害実態調査を中心として

概要

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Maebama beach has extremely been eroding by Tropical Typhoon waves since 1994. Some people say, without any scientific evidence, the erosion is due to some effect of the construction of KURIMA bridge. There are no data of waves and currents. But, there are much data of Typhoons, passed near Okinawa Islands, and the profile of the beach. Analyzing the available data and the photographs of the beach, it become clear that the beach has been nourishing by wind waves and swell from Typhoons. Wind waves incoming to the beach are caused by seasonal wind blown from the north sea of the Island. The courses of the Typhoons passed near MIYAKO Island are classified in two patterns. One of them corresponds to the course of Typhoons passed through the south western sea of the Island, and the other is the course of Typhoons passed through the north eastern sea of the Island. Few Typhoon, passed the north eastern sea of the Island, has been occurred for two years in last twenty years. The swell from the Tyhoon passing the Island has been acting to the sands on the beach to transport to the north side. This seems to be the main reason of the erosion of MAEBAMA beach.
琉球大学工学部の論文