Abstract
Abstract. The importance of hydrological processes for landslide activity is generally accepted. However, the relationship between precipitation, hydrological responses and movement is not straightforward. Groundwater recharge is mostly controlled by the hydrological material properties and the structure (e.g., layering, preferential flow paths such as fissures) of the unsaturated zone. In slow-moving landslides, differential displacements caused by the bedrock structure complicate the hydrological regime due to continuous opening and closing of the fissures, creating temporary preferential flow paths systems for infiltration and groundwater drainage. The consecutive opening and closing of fissure aperture control the formation of a critical pore water pressure by creating dynamic preferential flow paths for infiltration and groundwater drainage. This interaction may explain the seasonal nature of the slow-moving landslide activity, including the often observed shifts and delays in hydrological responses when compared to timing, intensity and duration of precipitation. The main objective of this study is to model the influence of fissures on the hydrological dynamics of slow-moving landslide and the dynamic feedbacks between fissures, hydrology and slope stability. For this we adapt the spatially distributed hydrological and slope stability model (STARWARS) to account for geotechnical and hydrological feedbacks, linking between hydrological response of the landside and the dynamics of the fissure network and applied the model to the hydrologically controlled Super-Sauze landslide (South French Alps).
Highlights
The importance of understanding the hydrological system within a landslide is commonly accepted; including hydrological processes and their variability in landslide modelling is quite difficult and, often limited (Bogaard, 2001; Lindenmaier, 2007)
The model consists of a core model describing the dynamics of saturated and unsaturated flow in the soil and of sub-models that describe related hydrological processes such as interception, transpiration, and snow accumulation and snow melt
Hydrological feedback is the mutual dependence between landslide hydrological responses and effectiveness of the fissure network to transport water which increases with soil wetness (Tsuboyama et al, 1994; Noguchi et al, 1999; Sidle et al, 2000)
Summary
The importance of understanding the hydrological system within a landslide is commonly accepted; including hydrological processes and their variability in landslide modelling is quite difficult and, often limited (Bogaard, 2001; Lindenmaier, 2007). The main difficulties stem from spatial and temporal heterogeneity of bedrock geometry, material layering, hydrological material properties and dominant hydrological processes across the landslide (Malet et al, 2005; Krzeminska et al, 2013) This is true when dealing with slow-moving clayey landslides, where the continuous movement of the sliding material results in fissure formation with successive opening and closing of fissure apertures. We apply the above model (Krzeminska et al, 2012) to the hydrologically controlled slow-moving Super-Sauze landslide and explicitly take into account the mutual dependence between fissures (their geometry and effectiveness for transmitting the water downslope), hydrology and level of landslide activity. The main objective of this study is to model the influence of fissures on the hydrological dynamics of slow-moving landslides and to formulate a framework to incorporate feedback between fissure flow and stability state into landslide modelling
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