Accounting for soil parameter uncertainty in a physically based and distributed approach for rainfall-triggered landslides

In this study we propose a probabilistic approach for coupled distributed hydrological-hillslope stability models that accounts for soilparameters uncertainty at basin scale. The geotechnical and soil retention curve parameters are treated as random variables across thebasin and theoretical probability distributions of the Factor of Safety (FS) are estimated. The derived distributions are used to obtain thespatio-temporal dynamics of probability of failure, in terms of parameters uncertainty, conditioned to soil moisture dynamics. Theframework has been implemented in the tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated BasinSimulator-VEGetation Generator for Interactive Evolution)-Landslide model and applied to a basin in the Luquillo ExperimentalForest (Puerto Rico) where shallow landslides are common. In particular, the methodology was used to evaluate how the spatial andtemporal patterns of precipitation, whose variability is significant over the basin, affect the distribution of probability of failure, throughevent scale analyses. Results indicate that hyetographs where heavy precipitation is near the end of the event lead to the most criticalconditions in terms of probability of failure