The role of bedrock groundwater on runoff and landslide initiation

点击翻译按钮获取中文摘要

To examine runoff generation processes in very steep terrain underlain by relatively unweathered granite and shale, several small watersheds were monitored ; two are in shale and two are in granite in Ina, two are in Shale in Kanuma, central Japan. The shale catchments had distinctly different runoff responses to the same storm event, whereas the two granite catchments had similar runoff response ; high peak runoff coincides with rainfall peak. Most of the storm runoff water is defined as 'old water', in shale basins, and more than half in the granite basin. Soil water percolated vertically downward into bedrock even during storm event in shale watershed, whereas subsurface storm flow parallel to slope is observed in granite watersheds. These data suggest that subsurface storm flow is dominant even in very steep mountains, and subsurface flow through soil mantle is dominant in granite basins, whereas bedrock flow is dominant in shale basins.