Okhimath landslides and its impact assesment on the Madhyamaheshwar and the Kaliganga Sub-Watersheds using high resolution IRS 1C/ 1D data
M. M. Kimothi1, J. K. Garg1, V. Joshi2, R. Pahari3 and N. Juyal4
1Space Applications Centre, ISRO, Ahmedabad - 380 015
2G. B. Pant Institute of Himalayan Environment and Development, Almora
3Dasholi Gram Swarajya Mandal, DGSM, Gopeshwar
4Physical Research Laboratory, Ahmedabad - 380 015
Landslide constitutes a major natural hazard in the Alaknanda basin and every year cause considerable loss of life, a damage of communication routes, human settlements and other landcover. In recent times its frequency and severing has increased which is worrying the locals and the planners as well. The August 1998 landslide tragedy of the Madhyamaheshwar and the Kaliganga sub-watersheds in Okhimath Tehsil of Ruderprayag district has surpassed all the past records of calamity in this region. A few villages were completely wiped out and more than 30 villages have suffered large-scale damage of life and property. In order to ascertain the factors responsible for this tragedy in Madhyamaheshwar and the Kaliganga sub-watersheds, an attempt has been made to analyse high-resolution IRS 1C/1D (pre and post damage LISS III and PAN) data in conjunction with archived multitemporal satellite and ancillary data in GIS environment. These data were supported by field checks for accuracy assessment. To assess the impact on terrain conditions especially slope activation various thematic maps/ information were generated from 1966 to 1998 (pre and post) period and integrated. (a) Forest vegetation and landuse/ landcover (1966, 1988 April, 1998 of pre damage period and Oct/ Nov. 1998 of post damage period), (b) temporal change in landslide (active and Old), (c) potential hazard prone settlement, and (d) biotic pressure zone at 1:50,000 scale and 1:25,000 scales. Beside this, geology and lithology, lineaments, slope, drainage/ RF/ Village location maps have also been generated at 1:50,000 scale. All these maps were subsequently integrated in GIS environment for generating Potential landslide hazard prone and biotic pressure zone maps. It has been found that during the last 32 years, from 1966 to 14 April 1998 (pre damage), the sub-watersheds do not show major loss of forest cover. Instead a steady state persisted in terms of natural resources condition showing more than 50% forest cover. Thus, apparently no direct relationship between the activation of slope and extent of forest cover is seen when viewed on total sub-watersheds basis. However, when viewed at micro-watershed level the study found a very significant role played by forests and land use change for the destabilization of the slope and the failure in the Madhyamaheshwar and the Kaliganga sub-watersheds especially in middle slopes (1000 - 2000 m altitude), where majority of the villages are situated. Attitudinally this zone is predominantly belonging to degraded Pine forest and was excessively utilized by the local people making it scantier. Mounting pressure on the forests located in the vicinity of villages with time and over pressurization of cultivable area on slopes (which are moderate to steep) have been found as one of the major factor for the land degradation.
Page 1 of 1