Prediction of rainfall-induced shallow landslides through integration of hydrological model with a slope stability model

Landslides are one of the most widespread natural hazards on earth and has been a major problem in many countries, especially in developing countries. Rainfall induced shallow landslides are ubiquitous on steep terrains of Himalayas, India and are accountable for substantial damage to properties, loss of human lives and livestock. They are densely distributed across territories, very frequent in time and space, and occur without any significant premonitory signals. Due to the surge in occurrence of extreme precipitation events as a result of climate change, rainfall induced landslides have become more frequent in the Himalayas. Since the mountains are becoming increasingly inhabited because of the population expansion, the geohazards like landslides have become more destructible. The Himalayas is one of the most vulnerable areas in the world and is a region of crucial interests.  The Himalayas has been receiving surplus amount of rainfall and which is a trigger for devastating landslides along the steep terrains.  Prediction of rainfall induced landslides can help the policy makers and local administration to propose appropriate mitigation strategies for unstable and vulnerable terrains.

In the present study, a hydrological model is integrated with a dynamic physically based slope stability model for the grid-wise forecasting of the stability of the terrain in the central Himalayas. The model has been optimised and calibrated based on remotely sensed data and multi-temporal landslide inventory corresponding to various landslide inducing precipitation events. HYDRUS 1D platform is used for the hydrological modelling which includes the derivation of SHPs and subsurface soil moisture. The hydrological model with finer resolution SHPs and subsurface soil moisture is later integrated with Transient Rainfall Infiltration and Grid-based Regional Slope-stability (TRIGRS) model to compute the factor of safety of the terrain. The integrated model is validated for the study area with the previous occurrence of the rainfall induced landslides. The integrated model shows higher positive rate for landslide prediction as compared with the utilization of simple slope stability model.

Keywords: Himalayas, landslides, HYDRUS 1D, TRIGRS