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.

The spatial and temporal evolution of contributing areas

“…Variable contributing areas and their extent and associated thresholds are likely different for headwater watersheds across geographic regions (see, for example, the compilation of hillslope precipitation thresholds in Weiler et al [2006] or Ali et al [2013]). The importance of the smaller-scale patterns of hillslope to stream connectivity for hydrograph dynamics, however, can change when moving from headwater systems (zero to third order) in a downstream direction to larger river systems (greater than or equal to, e.g., third or fourth order).…”

Temporal variability of subsurface stormflow formation

“…Subsurface stormflow (SSF) can play a key role for the runoff generation on hillslopes (see reviews by Jones and Connelly, 2002;Weiler et al, 2006). Considerable contributions to stream flow have been observed from SSF in lateral preferential flow paths where water flows with much higher flow velocities than in the surrounding soil matrix (e.g.…”

A paradigm shift in stormflow predictions for active tectonic regions with large-magnitude storms: generalisation of catchment observations by hydraulic sensitivity analysis and insight into soil-layer evolution

“…Both phenomena are commonly produced from the geophysical process of soil-layer evolution, but it is not easy to find a direct causal relationship between them because both may be mediated by a long evolutionary history. For example, if the development of macropores tends to be encouraged in clayey soil rather than in sandy soil through a long history of soil-layer evolution, the dependence of stormflow responses on the soil hydraulic properties might be quite different from that expected from idealised homogeneous properties (Weiler et al, 2006). If the drainage capacity of the downslope flow is so large that the storage change in response to the flow rate is negligible compared to that in the vertical unsaturated flow, the dependence of the RBPI values on slope length may almost disappear, as shown in the right panel of Fig.…”

“…Although the dependences deductively introduced from the surface topography as usually used in distributed runoff models might be often regarded doubtful by on-site observations in active tectonic regions (Montgomery and Dietrich, 2002;Weiler et al, 2006;McDonnell et al, 2007), only a few studies have focused on intercomparison (Negley and Eshleman, 2006;Uchida et al, 2006;. Since many observations of stormflow responses have already been obtained, a higher priority should be given to an inductive detection of the dependences on catchment properties by the intercomparison of these data to apply the results to runoffmodel parameterisations.…”