山地流域における直接流出の生起過程

Abstract

This paper describes first the new measuring instruments for syncronized record, and secondly the results observed by using such measuring instruments, and some con-siderations based on these results, in the research basin of the tributary of the RiverYasu.These results and considerations are as follows:1) As soon as a rain begins to fall, the very small increment of discharge in a channelis observed. This increment seems to be caused by channel precipitation.2) Additional runoff component in initial duration of rainfall is the flow, through thesurface layer composed of fallen leaves and organic matter, ' having the nature of interf low, to which Darcy's law is applicable.3) The hydrograph calculated by method of characteristics shows fairly good accordancewith the observed hydrograph. But after a certain time, an appreciable difference betweenboth hydrograph appears, and the difference becomes abruptly large for the heavy rainfall.4) The former seems to be caused by the rainwater running into the channel directlyafter infiltration, the latter by the change of interception mechanism, the change of mec-hanism of runoff like as the occurrence of overland flow, the decrease of infiltration rate.