Application of Geoinformatics on Mountain Land Hazard Mapping:
A Case of Annapurna Himalayas, Central Nepal
Krishna Poudel
Department of Geography, Tribhuvan University, Prithwi Narayan Campus, Pokhara, Nepal
P.O. Box 214, Pokhara, Fax ++977-61-25200
Email: gislab@pngeog.mos.com.np
Key Words: Mountain, Instability, Landslide, Human welfare, Sustainable development.
Abstract
Nearly one-fifth of the world's land surface is under the mountainous topography. There is a grievous coincidence of weak and vulnerable poor people, limited availability of resources, and fragile surface conditions, which causes the processes or conditions that may initiate and are often the main, immediate causes of damage. For the betterment of the human lives and their welfare, it needs to give the appropriate knowledge about the possibilities of hazard and to provide them the better alternatives. For the analysis two different methods have been applied. The method-1 is designed to give a general spatial association of different factors of the surface. The method-2 is applied for the computation of the Landslide Susceptibility Score (LSS). Based on these methods, the possible hazard prone areas of the region have been delineated. 13.8 percent of the 304 total settlement units of region are over the very high hazard-prone parcels. Field verification also confirmed the results depicted from the map analysis.
1. Introduction
Nearly one-fifth of the world's land surface is under the mountainous topography. Weak geological structure, steep and rugged surface, high altitude variation along with seasonal monsoon triggers result the high degree of fragility in the whole Himalayan territory (Bhandary, 1987: 1-88). Even under those fragile parcels of land a significant number of people are residing and adapting atypical socioeconomic activities. Those people are eking out their life support-bases from those fragile units of land. There is a grievous coincidence of weak and vulnerable poor people, limited availability of resources, and fragile surface conditions, which causes the processes or conditions that may initiate and are often the main, immediate causes of damage. Landslide is one of the most visible and commonly perceived destructive phenomena of most of the hill-slope in the mountain watersheds. For the betterment of the human lives of those who are residing over such surface conditions needs to provide appropriate knowledge about the possibilities of probable hazards and to give them the better alternatives in their conventional activities which might be essential steps for the human welfare and sustainable development. Present study is designed to identify the fragile parcel of land of mountainous topography in a micro spatial scale and suggestion have been made to reduce the possibilities of human vulnerability on those specific units.
2. Study Area
The study is concentrated on the upper part of the four perennial river basins Modi, Seti, Madi and Mardi of Annapurna Himalayan Range, Central Nepal. Geographically the region is extending from 28°13' north to 28°37' north latitude, and 83°43' east to 84°16'east longitude (Figure 1). The region covers an area of 1450 square kilometers. The area is extending nearly from 600 m asl at the lower part to 8000 m asl at the higher ridge. The area includes human settlement zone at the lower part, seasonal grazing at the middle part and permanent snow cover at the upper part.
Geomorphology of the region is characterized by the morphometry of the major river network systems. Upper part of the four major rivers and their numerous tributaries drain the area. The permanent stream network depicted in the 1:63,360 scale topographic map with 100 ft (30.56m) contour interval have been digitized in ARC/INFO PC-based vector GIS and calculated some morphometric parameters of the region (Table 1).
