Impact of Rainfall Variability on Landslide Stability: A Study on Chattogram Hill Tracts Using GeoStudio Software

Rainfall is a dominant trigger for landslides in the Chattogram Hill Tracts (CHT), where weak soil layers and steep slopes increase vulnerability. This study examines the influence of rainfall intensity and duration on slope stability through numerical simulations with GeoStudio (SEEP/W and SLOPE/W). Results show that slope behavior varies with soil type and rainfall scenario: steep silty sand slopes (75°) undergo rapid retrogressive failures under prolonged rain, clayey sand slopes (55°) undergo shallow translational failures during short, intense storms, and lean clay slopes (65°) tend to fail gradually or with a delay due to low permeability. The findings demonstrate that both the length and intensity of rainfall influence the buildup of pore-water pressure and the failure process. Prolonged moderate rain causes gradual weakening, while brief, heavy rainfall can trigger immediate collapse. These results highlight the importance of considering rainfall variability in slope stability assessments and strengthening site-specific mitigation and monitoring efforts in the CHT.