Abstract
Abstract. Groundwater dynamics may play a significant role in landslides. A detailed model is developed of the groundwater dynamics in landslides in varved clays in the Trièves area in the French Alps. The varved clays consist of a sequence of alternating silt and clay layers, covered by a colluvium layer and intersected by fissures. The hydraulic conductivity of the clay layers is negligible compared to the silt layers. It is conceptualized that fissures form a hydraulic connection between the colluvium and the varved clays. Groundwater recharge flows through the colluvium into the fissures, where water is exchanged horizontally between the fissure and the silt layers of the varved clays. Groundwater flow in the colluvium is simulated with the Boussinesq equation, while flow in the silt layers of the varved clays is simulated with the Richards equation. Longitudinal outflow from the fissure is simulated with a linear-reservoir model. Scattered data of relatively short monitoring periods is available for several landslides in the region. A good similarity between observed and simulated heads is obtained, especially when considering the lack of important physical parameters such as the fissure width and the distance between the monitoring point and the fissure. A simulation for the period 1959–2004 showed some correlation between peaks in the simulated heads and the recorded occurrence of landslides, while the bottom of the varved clays remained saturated during the entire simulation period.
Highlights
The hydrological mechanisms taking place in landslides are often not investigated extensively, whereas their importance is frequently recognized (e.g. Reid and Iverson, 1992; Iverson, 2000; Wilkinson et al, 2002; Lindenmaier et al, 2005; Schulz et al, 2009; Wienhofer et al, 2010; Bogaard et al, 2012)
The objective of this paper is to present an approach for the quantification of groundwater dynamics in varved clays and relate these dynamics to observed landslide movements
Van Asch et al (1996) describe a conceptual hydrological model equivalent to the model used in this research, but use different equations to represent the groundwater dynamics
Summary
The hydrological mechanisms taking place in landslides are often not investigated extensively, whereas their importance is frequently recognized (e.g. Reid and Iverson, 1992; Iverson, 2000; Wilkinson et al, 2002; Lindenmaier et al, 2005; Schulz et al, 2009; Wienhofer et al, 2010; Bogaard et al, 2012). The hydrological mechanisms taking place in landslides are often not investigated extensively, whereas their importance is frequently recognized Water flow through fissures in landslides is an example of a hydrological process that is discussed frequently, but rarely quantified (Van Beek and Van Asch, 1999; Krzeminska et al, 2012). At least 15 % of the area covered by the varved clays is considered to be unstable (Jongmans et al, 2009). Infiltration of precipitation is the most important triggering mechanism for landslides in varved clays, as increased pore water pressure on the slip plane results in a reduction in stability (Van Asch et al, 1996, 2007; Van Genuchten and Van Asch, 1988; Van Genuchten, 1989; Vuillermet et al, 1994)
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