Physically-based definition of rainfall thresholds for shallow landslides in a tropical mountain watershed of the Colombian Andes

Landslides cause important impacts around the world, with many human and economic losses. For its prediction, rainfall thresholds have been used to represent the relationship between precipitation and landslide occurrence. Distributed physically-based models have also been used to define thresholds for shallow landslides based on the variation of the factor of safety (FS) due to rainfall infiltration. In this work, rainfall intensity (I) and duration (D) thresholds are determined in a tropical mountain watershed of Envigado (Colombia) using two physically-based models: TRIGRS and Papa's model. In both cases, multiple simulations were made to determine the critical rainfall intensity and duration conditions that cause instability in a percentage of the total area (ac) of the study site and to compare the characteristics of the threshold curves of both models. These critical I-D conditions were fitted to powerlaw equations and a comparison was made between the curves obtained using different ac values. The rainfall thresholds determined with both models presented a good fitting to a power-law equation, but Papa's model had a higher correlation (R > 0.99) for the different ac values that were implemented. SCG-XIII INTERNATIONAL SYMPOSIUM ON LANDSLIDES. CARTAGENA, COLOMBIAJUNE 15th-19th-2020