Rainfall seasonality on landslide probability: a modelling approach

Departament of Geosciences and Environment, National University of Colombia, Colombia

^a Corresponding author: emunozh@unal.edu.co

Abstract

Precipitation is one of the main landslides triggering factors because the amount of infiltrated water into the ground causes changes in pore pressure due to the decrease in suction or the rising water table level. In this paper we estimated the return period of landslides from a rainfall stochastic behavior. Using rainfall intensity and duration probability density functions (pdf) and Philip’s infiltration model, the pdf of water infiltrated volume into the soil was obtained. Then, assuming the soil reaches saturation, the pdf of depth wetting front (zw) was obtained. Finally, with zw and the Mohr-Coulomb rupture criteria, the pdf of the Factor of Safety (FS) was determined. Subsequently, landslide occurrence was analyzed under different hydroclimatic scenarios, such as dry and wet seasons and El Niño Southern Oscillation (ENSO) phases. The occurrence of shallow landslides depends more on intensity storm than duration storm, and they are more likely to happen during La Niña phase than during El Niño phase because both storm duration and storm intensity tend to increase.