Landslide Risk Assessment in a Century-Old Tea Plantation Range Following Monsoonal Extremes in the Western Ghats of Kerala, India

Abstract

Landslides pose a significant threat in the Kannan Devan Hill (KDH) region of the Western Ghats (WG) in Peninsular India, particularly during the monsoon season. This study seeks to explore the various factors contributing to landslides, beyond the primary trigger of heavy rainfall. In alignment with the United Nations Sustainable Development Goals (UN-SDGs), which emphasize sustainable cities, climate action, and disaster risk reduction, we employed the Frequency Ratio (FR) method on Geographic Information System (GIS) platform to evaluate the influence of geological characteristics, terrain morphology, and human activities on landslide occurrences. As a result of this analysis, we developed a Landslide Susceptibility Zonation (LSZ) map for the KDH region. The map classifies the area into three risk categories: low-risk (20.96%), moderate-risk (46.40%), and high-risk (32.64%). These classifications reflect the combined effects of various contributing factors, with heavy rainfall and increased surface runoff identified as key drivers of landslide events. A focused analysis of the catastrophic Pettimudi Landslide (Idukki district, Kerala, dated 28.08.2020 Map No: 20202/03, NRSC/ISRO, Hyderabad, 2020), further demonstrated the complex interplay between climatic, geological, geomorphological, and anthropogenic factors in triggering such disasters. The study underscores the critical need for integrated preventive measures to mitigate future landslide risks, thereby enhancing the resilience and sustainability of vulnerable regions in accordance with global development objectives.