A model of hydrological and mechanical feedbacks of preferential fissure flow in a slow-moving landslide

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 slowmoving 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).

Dry Spells and Extreme Precipitation are The Main Trigger of Landslides in Central Europe

“…Wetting/drying cycles are considered important in cracking, even in deep-seated failure movements and despite the fact that preferential flow paths will only influence the soil mantle 52 . It has also been shown that soil swelling, continuous opening/closing of the fissures, and compaction/compression forces of upslope material will result in increased pore-fluid pressure and thereby act as important drivers of activity in clay-rich, slow moving earthflows 10,53,54 . Despite the fact that forested slopes are somewhat less susceptible to occurrence of desiccation cracks than bare surfaces, the enlargement of tension cracks (Fig.…”

Historic drought puts the brakes on earthflows in Northern California

“…It will be both illuminating and important to continue to monitor these earthflows as rainfall returns, particularly given the hypothesis that extreme drying may increase pathways for runoff into earthflows through development of cracks [Krzeminska et al, 2013;McSaveney and Griffiths, 1987]. Catastrophic failure of earthflows is not common but the current extreme drought may generate an unprecedented, nonlinear response [Pelletier et al, 2015].…”

Hydraulic Conductivity and Pore Water Pressures in a Clayey Landslide: Experimental Data

“…Several authors recognized the role of discontinuities as preferential flow paths that facilitate the propagation of pore water pressure associated to rain (among others, [4−8]). The influence of discontinuities on landslide behavior was also discussed by Hencher [9], Sharma & Nakagawa [10], and Krzerminska et al [11], for a two-fold mechanism: faster pressure build-up and enhanced drainage. Vitone and Cotecchia [12] and Cotecchia et al [13] considered fissures as an internal factor predisposing the slope failure from both mechanical and hydraulic points of view.…”