Landslide hazard zonation of Tawaghat-Jipti route corridor, Pithoragarh, Uttaranchal State: using GIS and probabilistic technique approach

Abstract

The stratigraphically important Tawaghat -Jipti Route corridor along Kali River Valley in Pithoragarh district of Uttaranchal State is characterized by formidable physical features. The lofty hill ranges, steep valleys, cliffs, gorges and huge accumulation of scree and debris mass owe their origin to complex physical, geologic and tectonic processes. Being a part of the active Himalayan orogenic belt, the natural hazards viz. landslides and earthquakes forms an integral part of the study area. In the investigated area, landslides are by far the most significant natural hazard in terms of damage caused to lives and properties. Landslides in the study area are triggered both due to natural phenomena (high rainfall, seismicity) and anthropogenic activities (road development and deforestation). Commonly observed slope failures include block slide, debris slide and earth creep. The presented study aims to develop a methodology that could produce a hazard map over a large area with higher degree of accuracy in a GIS environment; incorporating utility of information theory in landslide hazard zonation. In all, 37 variables are identified as conditioning and triggering factors and accordingly probabilistic prediction map is prepared by this method. On the basis of histogram distribution, the polygon elements are classified into five hazard classes viz. very low (Ij <= -0.02), Low (-0.02 < Ij < 0.103) moderate (0.10 <Ij <0.23), high (0.23 < Ij < 0.40) and very high (Ij > 0.40) landslide hazard prone zones. Further, this probabilistic prediction map is compared with the actual landslide map generated from recent satellite data (IRS ID LISS-III+PAN, December 2002) for the accuracy of prediction. The generated hazard maps agree with the observed landslide incidences. Thus, this adopted approach effectively proves its efficacy in deriving a reliable landslide hazard zonation.