Shallow landslide triggering in unsaturated vegetated slopes: Efficient computation of susceptibility maps

Abstract

A modelling platform is developed to study the coupled hydromechanical processes occurring in shallow unsaturated slopes prone to landslide hazards. It is supplemented with a Graphical User-Interface (GUI) and relies on a finite element solver here referred to as cLiNUs (Computational Landslide Initiation through Numerical Simulations), which discretizes and solves the partial differential equations governing momentum and water mass balance for stratified deposits. cLiNUs allows the versatile simulation of hydrologic processes causing infiltration, surface runoff, moisture increase, deformation, and failure in shallow slopes. In addition, it is coupled with a novel vectorization strategy that enables the mapping of model computations on digital elevation models (DEM) to generate landslide susceptibility maps throughout the duration of storm events. The GUI includes routines for simple parameter initialization, selection of hydro-mechanical constitutive laws, determination of boundary conditions, and results’ visualization. The program also enables a straightforward use of data about stratigraphy (i.e., multiple soil layers within a slope profile), vegetation cover, swelling/shrinkage response of unsaturated soil deposits and water runoff, thus ensuring a variety of analyses for educational and scientific purposes. The capabilities of the new computational platform are illustrated with reference to multiple examples showcasing its ability for landslide susceptibility assessment at the scale of individual slopes. Furthermore, selected examples of regional scale performance are discussed, including spatiotemporal predictions of landslide triggering for a well-documented series of debris flows and runoff simulations taking into account the role of vegetation. The proposed framework opens new possibilities in landslide hazard zonation studies by enabling the incorporation of important datasets that otherwise would remain neglected (i.e., vegetation/land cover and its role on surface/subsurface flow, deformability/hydraulic properties of soil deposits, complex layering sequences of stratified slopes, transient rainfall, among others) while at the same time, relying on a user-friendly interface.