The Andaman and Nicobar Islands which comes under agro-climatic zone XV are characterised by least variations of maximum and minimum temperature during the entire year. Due to the influence of SW monsoon which prevails from May to September and followed by NE monsoon along with the cyclone thrash out in November, Port Blair of South Andaman district receives a huge volume of annual rainfall i.e in excess of 3000 mm. This investigation has been carried out to determine rainfall induced landslide at Chakkargaon of Port Blair. 2D Electrical Resistivity Tomography (ERT) and Self potential technique have been applied to assess the slope instability of this area. The elevation model of the area is prepared using Surfer software. Four 2D ERT profiles with the Wenner array configuration were carried out to study the distribution of subsurface electrical resistivity of the slope. Geo-electrical data shows several zone of low resistivity values (12 Ohm-66 Ohm), identified as a water saturated weathered /fracture zone. The water saturated zone plays a major role in the triggering process of landslide as they increase the unit weight of the mass. The negative potential values (-0.2mV to -0.34mV) of Self-Potential at various parts of the subsurface may have been due to water infiltration at the fracture as well as weathered zone and indicate the direction of the water flow.
During the monsoon period, due to intense rainfall and the water infiltration cause a decrease in soil suction and shear strength and increase in shear stress, which might have induced slope failure at Chakkargaon slope. Therefore, it is necessary for continuous monitoring of water content within the slope using 2D electrical resistivity tomography and self-potential method on a regular basis. The integrated analysis enable us for a better understanding of slope stability and developing an early warning system of slope failure by which we can reduce the severity of damage.