The frequency of rainfall-triggered landslides is increasing across the world. Infiltration of rainwater into the slopes with low permeable soil increases the pore water pressure and reduces the stability of slopes. Also, in the recent past, Kerala experienced many rainfall-triggered landslides. One of the most efficient way to prevent rainfall-triggered landslides would be the usage of composite geosynthetics which can combine the functions of pore pressure dissipation and reinforcements. In the present study, soil is collected from a nearby site where landslide has occurred and the geotechnical characterisation of the soil was carried out. An attempt was made to investigate the performance of steep soil slopes with and without the geosynthetics when subjected to rainfall, numerically. The study highlights the importance of the use of a composite geogrid in reinforced soil slopes composed of locally available marginal soil. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.