Terrain Factors Induced Slope Instability in CNG 37 – Ghat section, Panthalur, The Nilgiris

Abstract

— Landslides are short-lived phenomena but can cause extraordinary changes in the landscape, destroying life and property. Mitigation and management of natural disasters are important issues. Recognising this, the United Nations in the year 2004 made gout “Learning from today’s disaster for tomorrow’s hazards”(UNISDR website). The Nadugani Hill is situated in SE of Panthalur taluk, Nilgiris District. The ghat section is 6.5 km in length. The region has moderate climatic conditions. The average rainfall in this ghat section is 3500mm. In this ghat section, two major activities, like tea plantation and heavy truck movement, lead to slope instability during heavy monsoon season. The study mainly aimed to use terrain factors and identify land susceptibility zonation. In this context, a detailed investigation was carried out using geomorphology, parent rock weathering, structural mapping, runoff and anthropogenic activities. The ghat section is covered by a thick Reserve Forest, a tea plantation and a smaller area enclosed by settlement. Hornblende biotitic gneiss and patches of charnockite in some places cover the study area. The gneissic rocks are highly fissile in nature. NE - SW fault controls the drainage systems, contributing to landslides. The structural data delineated from IRS-RS2, L-IV data and the lineaments are oriented in NE - SW. Morphology is one of the prime factors that cause which is landslides. Satellite imageries identify structural and fracture valleys in this study area. The thematic maps were converted into a digital format using ARC Map (10.2v) software. GIS-based Decision Support System provides advanced models of a system to identify land susceptibility zonation. Based on the analysis, the study area has been categorized into low, moderate, high and very high classes.