Environmental Impacts Of The Regulation Of TheShinano River, Niigata Prefecture, Japan

Abstract

The coastal zone of Niigata Prefecture is severely affected by erosion. This study was developed to investigate the relationships between river regulation and changes to the coastal zone. Regulation of the Shinano River began during the Meiji Period with the construction of a long jetty. The jetty was built to avoid the silting of the river mouth, and allow the significant maritime trade to continue with inland transport via the Shinano River. Additional regulation involved the dredging of two channels southward from the mouth of the Shinano River, the Sekiya and the Ohkozu, for the purpose of flood mitigation in the Niigata Plain. To evaluate changes to the coastline, several approaches were used. Firstly, six sets of aerial photographs were examined. Then, the sediments grain-size parameters and mineral variation were analyzed to find the correspondence with shoreline changes. As a third approach, field surveys were conducted and historical data on the coastal process was assessed. The coast in the vicinity of the artificial channels accreted and there was erosion on the down-drift side of the river mouth.