| Sediment release and deposition due to a dam removal were investigated in the Arase Dam, Kumagawa River, Japan. In the first year of dam removal, about 26% of trapped sediment were washed away and it formed new sand bar and riffle on the downstream of dam but the sediment release were sharply decreased in the second year (>3% of total). The river bed stability seems to be affected by the dominant gravel and cobble size sediment and rock framework effect at the rapid which existed before dam construction. In terms of impact on suspended sediment supply, we could not monitor significant changes assumed by the dam removal. The dam removal properties were compared at the point of relation between sediment size and actual tractive force and it showed that sediment size treated in the Arase dam relatively large and it made difference of resilience for the unusual sediment supply. |
