Environmental Analysis of some Model Areas in the Upper Uonogawa Watersheds from the Viewpoint of Natural Torrent Control Engineering

A river has various ecological functions such as the selfcleaning ability, the ecological system of the aquatic fauna and flora, the interaction of surface water and ground water, the formation of a special climate caused by higher evaporation, the effect on the landscape, the recreational function and so on. These factors have to be taken into consideration in watershed management and torrent control engineering. Therefore, the construction methods in watershed management and torrent control engineering should be evaluated according to the effects which these methods have for preserving these functions. This research is an attempt to analyze how nature friendly the torrent control engineering applied in Japan is. This analysis was performed by collecting basic data on rivers located in an alpine area in Yuzawa. Actually, the survey area locates in the upper Uonogawa watersheds and includes the upper course of Uonogawa itself, Daigentagawa and Noborigawa. The surveyed distance of these river courses extends to 7,500m, 8,000m, and 12,000m, respectively