Subsurface Stormflow

Abstract Subsurface stormflow is a runoff producing mechanism operating in most upland terrains. In a humid environment and steep terrain with conductive soils, subsurface stormflow may be the main mechanism of storm runoff generation. In drier climates and in lowlands with gentler topography, subsurface stormflow may occur only under certain extreme conditions (high antecedent soil moisture), when transient water tables form and induce lateral flow to the channel. While an important contributor to the volume of flow in the stream, subsurface stormflow is also responsible for the transport of labile nutrients into surface water bodies. Since the flow path of water in the subsurface often determines the chemistry of waters discharging into the stream and hence the water quality, characterizing this subsurface flow path and the water's age and origin is important. Subsurface stormflow may also enhance positive pore pressure development in steep terrain and may be responsible for landslide initiation. Thus, subsurface stormflow is of great interest and importance beyond the conventional hydrological literature. This article examines the history of the study of subsurface stormflow processes, reviews theories on the generation of subsurface stormflow, and gives a detailed overview of current research in subsurface flow processes and the implication for future research.