STUDY ON FACTORS OF RAPID CHANGE TOWARD ARTIFICIAL COASTLINE-THE EXAMPLE OF SETOHAMA BEACH IN SOTOBO AREA IN CHIBA PREFECTURE

Factors of rapid change from natural sandy beach to artificial coastline covered by concrete armor units were investigated at the Setohama Beach in Sotobo area in Chiba Prefecture. The Setohama Beach was famous for oceanic recreation in the past, and along the coastline a national road runs. With the shoreline recession, wave overtopping became severe, and land reclamation over the sandy beach was carried out as well as the construction of gently sloping revetment in front as the measure at the sacrifice of natural sandy beach. A part of local people welcomed land reclamation because of widening of parking lot and the others claimed loss of nature. This process of change was investigated by field observation and comparison of past aerial photographs.