一ツ瀬川上流域における山腹崩壊地からの濁水発生の現地観測

抄録

The Hitotsuse River which flows in the middle part of Miyazaki Prefecture, Japan, had been in a severe problem of high turbid water prolongation in recent years. Consequently, new countermeasures were needed to improve river environment on the watershed to minimize the problem. In order to obtain a better understanding on the turbidity generation, field measurements of turbid water were performed on a representative collapsed mountain slope in the upstream region of the watershed. Site reconnaissance revealed that there were 3 types of turbid water generation from the collapsed slope, namely: Type A: Erosion on the slope face, Type B: Waterside erosion at the slope toe, and Type C: Waterside erosion in the downstream river bed. The quantitative analysis clarified that most of the turbid material was generated by both Type A and Type B. Therefore, treatment at both the slope face and the slope toe of the collapsed mountain slope were essential to control turbid water generation.