Landslide Hazard Mapping Using GIS: A Case Study from Kulekhani Watershed, Makawanpur

Abstract

Kulekhani Watershed is situated in Makawanpur district of Central Development Region, and about 30 km. west of Kathmandu valley. This watershed houses storage type reservoir, one of its only kind in Nepal. Landslides occurrence is a frequent phenomena in the study area and the disaster of 1993 and preceding year wreaked havoc. So, the problem of landslide hazard and mitigation is pivotal to address development challenge.

The study aims to develop causal factor maps by verifying digital data. The various maps are Slope, Aspect, Relief, Internal Relief, River Distance, Landuse and Geology which are formed, stored and analysed using GIS. These factors then applied in methodologies based on “Bivariate Statistical Analysis” viz. Frequency Ratio, Statistical Index Method, Landslide Susceptibility Analysis, Weight of Evidence Modelling and Certainty Factor in ILWIS 3.0. The weight maps were formed from 7 factor maps through different methods and final hazard maps were created classifying into 3 hazard areas i.e. Low, Moderate and High. The analysis of the results shows that there do not lay any major differences in methods and their prediction of hazard areas and landslides are almost coherent.

The landslide susceptibility map indicates that the area covering low, moderate and high hazard class for 5 different approaches is in the range of approx. 28-31%, 32-37% and 3639%

respectively. The detected landslides in the area for the 3 hazard areas by applying abovementioned various methods are in the range of approx 8-10%, 27-29% and 62-66%. The study estimated the accuracy of landslide hazard mapping results based on criteria considering the number of landslides occurrence. Based upon this predicted results were found to be reliable. The result of the experiment has also shown that application of GIS has proven to be an effective tool in landslide hazard assessment.