Analysis of Relationship Between Landslides and Rainfall in Karwar, Uttara Kannada District, Karnataka, India

Abstract

Landslide is a hazardous geological phenomenon and a common occurrence in hilly regions. It causes loss of life and destruction of property depending on the intensity of its occurrence. Landslide is the movement of mass of rock, earth or debris down the slope. One of the important triggering factors for landslide occurrence is rainfall and is usually considered for slope failure predictions, yet the relationship between rainfall and landslide occurrences is very complex. An attempt is made to understand the relationship between rainfall and landslide in the study area. A devastating landslide occurred in October 2009 in Kadwad village of Karwar taluk in Uttara Kannada district, killing 19 people and burial of several houses. On the same ill fated day, there occurred landslides at 21 more locations in Karwar. The landslide incidence was triggered due to heavy rainfall on 2nd and 3rd October 2009 which resulted in mass movement of debris. For this study, daily precipitation data from Karnataka State Natural Disaster Monitoring Centre/District Disaster Professional, Karwar and landslide records from media and other sources of that particular year were considered for the statistical analysis to understand landslide mechanism. Analysis shows a strong correlation between landslide occurrence and rainfall pattern. The landslide incidence is determined by the magnitude of the short episode of rainfall intensity with the threshold value of above 260 mm in that particular year. Thus the rainfall with less than the minimum threshold value did not cause triggering of landslide whereas landslide occurred above the threshold value. The possible cause for the triggering of Kadwad landslide is not due to saturation of soil caused by antecedent precipitation but it is due to short term intensive rainfall.