Estimation of sediment supply of Tedori river to Ishikawa coast, Japan

Abstract

    In recent decades, sand and gravel mining and dam constructions conducted in the Tedori River have affected seriously morphology of both river and Ishikawa coast, Japan. This paper aims to estimate temporal variation in sediment supply of the lower Tedori river to Ishikawa coast using a dataset consisting of river topography and related human intervention over the period of 58 years. The results indicate that dredging activity and sand and gravel mining induced a decrease in sediment supply to the Ishikawa coast in the period of 1950 -1991. The sediment supply reached the lowest value at 0.72×105 m 3 /yr during the period 1972 - 1991. Due to totally prohibited sand and gravel mining in 1991 together with Tedorigawa dam operation in 1981, the sediment supply slightly recovered to 1.02×105 m 3 /yr in the period of 1991 - 2007. Time lag between erosion occurred in the Ishikawa coast and that occurred in the lower Tedori river was attributed to the indirect effect of sand and gravel mining conducted in the reach of 0-7km upstream far from the river mouth.