A STUDY OF THE CHARACTERISTICS OF SUSPENDED SEDIMENT LOAD IN THE KATANIWA RIVER BASIN

摘要

The authors conducted a set of survey on suspended sediment load transportation in the Kataniwa River, during the flood on June 22nd-23rd ′97, and analyzed the concentration of suspended sediment. The following relationships are found out through the analysis; 1) the shape of suspended load flux hydrograph is corresponding to the discharge hydrograph, 2) on the other hand, the one of wash load is not corresponding to the discharge hydrograph, but to the hyetograph. These relationships lead to the hypothesis that the suspended load yields at the riverbed and is transported with the flood flow, and that the wash load yields at the surface of the basin and pours into the channel rapidly. To investigate a mechanism of these relationships, a numerical model which evaluates concentration of suspended sediment load on a tributary basin, was newly developed. Two types of the sediment yield model were demonstrated in accordance with grain size. The larger coarser grain size was produced at the riverbed, and the smaller finer size like wash load was produced on the surface of the basin. The results of the simulation of suspended load show fairly good agreement with the observed data.