Progress towards understanding stormflow generation in headwater catchments

An emerging concept of stormflow generation in steep, forested headwaters i s presented that incorporates dynamic hydrologic linkages among and within distributed geomorphic units. The hydrogeomorphic concept is based on field studies at Hitachi Ohta watershed in Japan. For drier antecedent condition s, stormflow is generated primarily as saturation overland flow from narrow riparian zones and as direct channel interception. As moisture increases, subsurface flow from the soil matrix augments stormflow. Further increases in wetness induce incipient runoff from hollows with shallow soils as well as macropore drainage. During very wet conditions, self-organized preferent ial flow networks develop that efficiently drain hillslopes; hollows also c ontribute significantly to stormflow.