The role of subsurface runoff through bedrock on storm flow generation

Abstract

Abstract:The influence of bedrock subsurface flow on storm runoff generation was investigated in Japan in two regions in Japan underlain by three bedrock types. One region, with approximately 2500 m of relief, is located in the Japan Alps, central Japan (In a region), where six small forest-covered watersheds underlain by granite and Mesozoic shale were studied. Two of these watersheds were instrumented to monitor stream discharge and the other four are springs occurring at the bedrock exposure. The other study area is in northern Kyoto prefecture, western Japan (Oe region). Here, spring distribution and seasonal flow were monitored in two steep basins underlain by serpentinite rocks. Distinctly different runoff responses were observed: the granite watershed exhibited a large and rapid runoff peak that coincided with the rainfall peak (type 1); and the shale and serpentinite basins exhibited small initial runoff peaks followed by a maximum peak discharge five to ten times greater with a convex recession limb (type 2). Runoff response from bedrock springs had characteristics similar to type 1 hydrographs; however, discharge increased only when the antecedent precipitation index was large and the runoff peak was delayed between 10 h and 1 week after rain events. The specific discharge of the springs decreased with increase in altitude in the Oe region, especially in dry periods. This decline in discharge with elevation suggests that a deep subsurface flow system through bedrock fissures contributes to the storm water flow in serpentinate basins. When comparing runoff response and spring discharge, slow or double peak runoff response may be a good indicator of the influence of bedrock subsurface outflow on storm runoff generation in steep mountainous regions.

True colors – experimental identification of hydrological processes at a hillslope prone to slide

“…Finally, we could not detect any dye staining at the soil-bedrock interface during our experiments. These findings are in contrast to many hillslope hydrology studies, where the soil-bedrock interface is described as a prominent lateral drainage feature (Onda et al, 2001;Tani, 1997;Uchida et al, 2002Uchida et al, , 2005.…”

“…Accordingly, SSF can develop along (1) soil pipes in the unsaturated zone (Mosley, 1979;Zuidema, 1985), (2) soil pipes in the saturated zone due to transient groundwater rise (Uchida et al, , 2005, (3) along preferential flow structures in the soil matrix in the saturated zone (Rohde, 1987;Sklash et al, 1986), or at (4) the soil-bedrock interface (Brammer and McDonnell, 1996; Tromp-van Meerveld 876 P. Schneider et al: Experimental identification of hydrological processes at a hillslope prone to slide . Other studies highlight the important role of the underlying bedrock, which can significantly contribute to runoff formation in steep terrain (Haught and Tromp-van Meerveld, 2011;Onda et al, 2001;Uchida et al, 2002Uchida et al, , 2005. Accordingly, it is important to understand to which extent the bedrock is connected to soil structures and the soil matrix, especially for predicting pore water pressure development in slopes, e.g., for predicting shallow landslides (Tromp-van Meerveld and Weiler, 2008).…”

Form and function in hillslope hydrology: characterization of subsurface flow based on response observations

“…Many catchments reportedly showing double-peak hydrographs are headwater catchments with predominantly steep slopes and shallow soils, and in many cases with periglacial slope deposits (Burt and Butcher, 1985;Onda et al, 2001;Graeff et al, 2009;Birkinshaw and Webb, 2010;Fenicia et al, 2014;Wrede et al, 2015;Martínez-Carreras et al, 2016). Such systems are characterized by pronounced subsurface structures and therefore are prone to heterogeneous flow patterns and preferential flow at the plot and hillslope scale.…”

“…This hypothesis is backed by a study comparing catchments of different geology (Onda et al, 2001), where the prolonged response of double-peak hydrographs was identified as an indicator of deeply percolating subsurface flow through bedrock fissures. This theory might also apply to the catchment investigated here, with its fractured schist bedrock (Kavetski et al, 2011).…”

Characteristics and controls of variability in soil moisture and groundwater in a headwater catchment

“…Fenicia et al, 2010). Groundwater dynamics and subsurface flow pathways are a key control on runoff generation and flow dynamics in a variety of different catchments (Onda et al, 2001;Soulsby et al, 2007), with strong evidence coming from hydrochemical analysis of streamwater. The hydrology of the riparian zone may be particularly sensitive to groundwater connections (Vidon and Hill, 2004).…”