History of Sand Drift Disaster at the Estuary of Assabu River in Esashi, Hokkaido, Japan

Abstract

Sunasaka coastal forest was established at the place where once Yanagisaki Village had existed. People in Yanagisaki had been forced to move to the opposite side of Assabu River because of a sand drift disaster. The disaster was considered to be caused by overcutting of the natural coastal forest early in the Meiji period. But Takeshiro Matsuura, the explorer in the late Edo period, recorded that the coast was mainly covered by herbaceous plants with no trees. Hamanaka, the foreshore of Yanagisaki, had long been used as pasture and many horses had been kept there. There were some cases of denudation caused by overgrazing around Hamanaka. These facts imply that the occurrence of the sand move was caused by overgrazing rather than overcutting. Blown sand during winter had threatened the students on the way to school, and many children had had to attend the work in spring to remove the accumulated sand from the paddy fields. Because the mouth of Assabu River tends to close during winter, a bypass channel has had to be excavated annually since the Edo period to prevent overflow. But the frequency decreased with the calming down of the sand move, presumably because of the establishment of the costal forest. We could not find information about the excavation in any historical records, but it become clear by conducting interviews with elderly.