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

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 in-
fluence 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).