昭和56年8月石狩川洪水における同時水位観測による河床抵抗の挙動特性の検討

抄録

The Ishikari River was hit by the largest recorded flood in August 1981, which caused a severe disaster in the basin. Comprehensive flood observations were conducted during the flood. In this study, behavior characteristics of river bed resistance are expressed by the relation of comparable bed roughness and the Froude number, which are calculated by data obtained in the simultaneous water level observations during the flood. Compared with the results of flume experiments, it is found that the bed resistance in Ishikari River during the 1981 flood is in the range between dune-covered and flat beds. The comparable roughness in the section near the river mouth is thirty times as large as the diameter of bed material, and six times in the adjacently upstream section. It is also suggested that dunes tend to develop in the section where the water surface gradient decreases during the decreasing period of discharge.