Hydrological and mechanical effects of roots in shallow landslide analysis: A physically-based approach

This study provides the first insights of a methodology for estimating the additional cohesion exercised by vegetation roots in a hillslope landslide analysis within a coupled ecohydrological-stability model. The existing coupled system is able to simulate the spatial distribution and temporal dynamics of Factor of Safety (FS) as a function of soil moisture dynamics. The model takes into account the hydrological effects of vegetation which, through the root water uptaking, contributes in reducing the soil water content and, thus, in increasing the slope stability. The additional mechanical root cohesion is estimated in a Fiber Bundle Model (FBM) framework that allows for the evaluation of the root strength as a function of stress-strain relationships of populations of fibers. The use of such model requires the knowledge of the root architecture to evaluate the additional reinforcement from each root diameter class. In order to reproduce such characteristics, we adopted a branching topology model based on the Leonardo’s rule that gives an estimation of the amount of root and the diameters distribution with depth at particular stage of plant life. The methodology has been tested in a simple synthetic hillslope with different configurations of vegetation types, i.e. tree and shrubs. The topological model has been calibrated using observed root area (AR) profiles of two considered vegetation types.