Runoff processes in headwater catchments—an experimental study in Western Ghats, South India

Field observations and experiments were conducted to study runoff in a headwater region in the mountains near the west coast of Karnataka, a south Indian state. Three catchments were studied. Pipeflow was observed in all three cases, and there was no subsurface lateral flow through the soil matrix. Pipeflow was a significant contributor to quickflow in two catchments. In the third, grassed catchment, a new mechanism of runoff, called pipe overland flow in this paper, was discovered, which contributed to quickflow. The contributing area for pipeflow increases with the magnitude as well as duration of rainfall, but a dual behaviour with respect to average rainfall intensity shows up in one of the catchments.