土石流の総合的観測その2. 1975年焼岳東斜面上々堀沢

Abstract

Every summer since 1970, observation had been carried out to measure the flowing state ofdebris flow on the eastern slope of Mt. Yakedake in Japan Alps. During this period, a new synthe-tic observation system has been developed and improved which has made us possible to get manyphysical informations about the flow with automatic and remote-controlled recording.Last summer, three year project has started in order to investigate the occurrence mechanismof debris flow, and our system extended over all the course of valley Kamikamihorizawa from theupper head to the lower fan. In last rainy season, debris flows have occurred at least eight timeson this valley, and the flowing states have been caught by the observation system. From theobservation results, occurrence place, frontal velocity, head height of debris flow, amount of erosionby the flow and the motion of large stones at the head of debris flow, etc were clarified and occurrenceconditions of the debris flow were examined with reference to hydrological characteristics in thatvalley.