Incorporation of Unsaturated Soil Properties in the Prediction of Rainfall Induced Landslides Using TRIGRS and Scoops3D Models: Fid-Bau Portal

Incorporation of Unsaturated Soil Properties in the Prediction of Rainfall Induced Landslides Using TRIGRS and Scoops3D Models

Musaib, A. / Divya, P. V.

Abstract

Landslides triggered by rainfall are becoming major threat in residual soil slopes worldwide. Several rainfall triggered shallow landslides were reported in residual soil slopes of Idukki in Kerala, India, during monsoon. Existing slope susceptibility maps and rainfall thresholds are generally based on statistical methods, which seek empirical relations between the geomorphological, topographical, geological, and environmental factors with the past landslides, without taking into consideration the geotechnical properties of the soil. Both saturated and unsaturated soil properties are important in analyzing the stability of residual soil slopes subjected to rainfall infiltration. In the present study, a landslide susceptibility model was developed for a region in Idukki by using two physical-process based models, TRIGRS (transient rainfall infiltration and grid-based regional slope-stability) and Scoops3D, which have the potential to incorporate both saturated and unsaturated soil properties in the regional modelling analysis. Transient rainfall infiltration analysis was performed using TRIGRS and the resulting pore water pressure profiles imported in Scoops3D for stability analysis. The developed model was validated with past rainfall event of August 2018, which was responsible for many landslides at Idukki, India. Predicted and the observed landslide points were compared against each other in both temporal and spatial perspectives using LR_classindex. The results show that the models have a good capability of landslide prediction, and therefore, these can be used for the development of both slope susceptibility map and in designing of warning system against the rainfall induced landslides.