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

Abstract

Abstract. In active tectonic regions with large-magnitude storms, it is still difficult to predict stormflow responses by distributed runoff models from the catchment properties without a parameter calibration using observational data. This paper represents an attempt to address the problem. A review of observational studies showed that the stormflow generation mechanism was heterogeneous and complex, but stormflow responses there were simply simulated by a single tank with a drainage hole when the stormflowcontribution area was spatially invariable due to the sufficient amount of rainfall supply. These results suggested such a quick inflow/outflow waveform transmission was derived from the creation of a hydraulic continuum under a quasisteady state. General conditions necessary for the continuum creation were theoretically examined by a sensitivity analysis for a sloping soil layer. A new similarity framework using the Richards equation was developed for specifying the sensitivities of waveform transmission to topographic and soil properties. The sensitivity analysis showed that saturationexcess overland flow was generally produced from a soil layer without any macropore effect, whereas the transmission was derived mainly from the vertical unsaturated flow instead of the downslope flow in a soil layer with a large drainage capacity originated from the macropore effect. Both were possible for the quick transmission, but a discussion on the soil-layer evolution process suggested that an inhibition of the overland flow due to a large drainage capacity played a key role, because a confinement of the water flow within the soil layer might be needed for the evolution against strong erosional forces in the geographical regions. The long history of its evolution may mediate a relationship between simple stormflow responses and complex catchment properties. As a result, an insight into this evolution process and an inductive evaluation of the dependences on catchment properties by comparative hydrology are highly encouraged to predict stormflow responses by distributed runoff models.

A Novel Method of Quantifying Catchment‐Wide Average Peak Propagation Speed in Hillslopes: Fast Hillslope Responses are Detected During Annual Floods in a Steep Humid Catchment

“…Soils on temperate vegetated hillslopes are permeable enough that most rainfall infiltrates, temporarily forming a perched water table above the bedrock or layers of low infiltration capacity (e.g., Anderson et al, 1997;Asano et al, 2002;McDonnell, 1990;Montgomery & Buffington, 1997;Noguchi et al, 1999;Uchida et al, 2002). When this perched water table extends to the upper hillslope during wet conditions, a lateral subsurface flow is typically generated along preferential flow paths or through pressure transmission, causing stream flow to increase suddenly (e.g., Anderson et al, 1997;Buttle & McDonald, 2002;Haga et al, 2005;McGuire & McDonnell, 2010;Sidle et al, 2000;Tani, 1997Tani, , 2013Turton et al, 1992;Uchida et al, 2004;Wienhöfer & Zehe, 2014). When hillslopes become saturated to the point that water storage is almost maximized, the shapes of the hyetograph and hydrograph become similar (Sidle et al, 2000;Tani, 1997Tani, , 2008Tani, , 2013Torres et al, 1998).…”

“…When this perched water table extends to the upper hillslope during wet conditions, a lateral subsurface flow is typically generated along preferential flow paths or through pressure transmission, causing stream flow to increase suddenly (e.g., Anderson et al, 1997;Buttle & McDonald, 2002;Haga et al, 2005;McGuire & McDonnell, 2010;Sidle et al, 2000;Tani, 1997Tani, , 2013Turton et al, 1992;Uchida et al, 2004;Wienhöfer & Zehe, 2014). When hillslopes become saturated to the point that water storage is almost maximized, the shapes of the hyetograph and hydrograph become similar (Sidle et al, 2000;Tani, 1997Tani, , 2008Tani, , 2013Torres et al, 1998). Theoretical studies of catchment hydrological behavior have suggested that the relative roles of hillslopes in catchment responses may change with the wetness condition of the catchment (Botter & Rinaldo, 2003;Robinson et al, 1995).…”

Review of Forest Soil Mitigation Effects on Stream Runoff

“…1．浸透流説と水みち説 Liang et al, 2011;Beven and Germann, 20131979Harman and Sivapalan, 2009Troch et al, 20031963 30cm Brutsaert, 2005Brutsaert, 1994Brutsaert, 20052013Freeze 1972 Freeze 1980Mosley, 19791988McDonnell, 1990Freeze 1962 1963 A 10 mm h -1 A 0.05 mm h -1 B 5 mm h -1 Kosugi, 1996HYDRUS 1D (Šim nek et al, 2013 0.5 0.2 -10 cm 1.7 6x10 -3 cm s -1 Fig. 3 Temporal changes in the distribution of volumetric water content in response to constant rainfall intensity of 10 mm h -1 calculated using a one-dimensional vertical form of the Richards equation.…”