Geomorphology and Landslide Proneness of Kerala, India A Geospatial study

Abstract

It was thought for a long time that only the younger and tectonically active mountains are prone to landslides and hence more attention was given in studying them the world over. But, when the landslides have started occurring in other mountain regions of high rainfall and human interventions also, these mountains too came under the purview of landslide studies. The studies thus widened to the other mountains revealed that the various geological/terrain parameters and the degree of anthropogenic activities occur in different combinations and assign varying grades of landslide probabilities. According to it, these mountains succumb to different degrees of landslides when heavy rainfall occurs. The state of Kerala, which is 600 km long in North Northwest–South Southeast and 35 to 120 km broad in East-West directions, is one such a region of recurring landslides. It is a unique physiographic/geomorphic province with highly elevated NNW-SSE oriented Western Ghat Mountains in the east, that are rimmed by the sub parallel systems of landforms like composite slopes, marginally raised lateritic uplands and the coastal plains successively in the west with gradual descending elevation, thus providing a step like topography. The regular annual rainfall of the southwest monsoons cause devastating landslides in Kerala due to the unique geomorphic setting. So the present study was carried out to analyse the geomorphology of the region in details, which is dominantly evolved by the tectonics, to elucidate its input over the landslides. In the study, the geomorphic features were studied in detail using the (i) satellite false colour composite imagery wrapped over the digital elevation model of the terrain, (ii) shaded relief maps and (iii) the topographic cross sections drawn over the above satellite data wrapped 3D terrain model. These were accomplished using the advanced options available with geospatial technology. The study revealed that due to the high degree of deformation and the resultant development of geomorphology of the study area, the rainwater infiltrates and cause landslides in the form of rock and cliff topples, rock and cliff falls, landslides, talus and debris falls/flows.