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Disaster management strategy for potential slide zones of Kumarkhera in Narendra Nagar township of Tehri Garhwal district, Uttarakhand, India

Disaster management strategy for potential slide zones of Kumarkhera in Narendra Nagar township of Tehri Garhwal district, Uttarakhand, India

Geology The extension

Geology The extension of Krol-Chandpur Nappe of Himanchal Pradesh is found in Narendra Nagar, Mussoorie and Nainital synclines occurring in one continuous belt. Narendra Nagar syncline is en echelon to the Mussoorie syncline with an intervening antiform in the core of which the underlying rocks are seen as a “window”. The Narendra Nagar syncline is highly compressed in the vicinity of Narendra Nagar town (Raina, 1978). The rocks constituting this area are those of Krol formation. According to Valdiya (1980) the Krol formation comprises alternating limestone and green slates in the lower part and thinly bedded purple and maroon shale with subordinate bands of dolomite in the middle part. However upper Krol comprises grey and blue limestone and lenses of flat pebble conglomerate. Geomorphology The geomorphic setup of Kumarkhera and surrounding area is defined by highly dissected denudo-structural hills that have witnessed large-scale gravity transport in the past. The present landscape of the area has been shaped by denudation of hills and large-scale gravity transport in the past. The first and second order streams (nalas) are Disaster management strategy 363 Plate 5. A field view of overloading of subsidence prone hill slope of Kumarkhera due to ill-conceived construction of two to three storied houses in the toe portion of an old landslide. Some small active slide scarps are also seen in the immediate upslope of habitation

DPM 19,3 364 Plate 6. Close view of construction of shops in the immediate upslope of Highway near a zone of active sliding and subsidence mostly incised with moderate to steep valley. The slope morphology is concavo-convex and steep hill slope with old slide scarp in the immediate upslope of Kumarkhera indicates that the area witnessed debris rock fall in the past. The habitation of Kumarkhera appears to be sitting over the body portion of an old debris rock fall zone. This is also evident by debris material and boulders on the concavo-convex slope of Kumarkhera and surrounding area. This debris rock fall material, has been reworked, by two small seasonal streams, as they cause bank erosion, during the rainy season. One small temporary shop (khoka) witnessed subsidence during the rainy season of 2003. Discussion Slope failures in Himalaya are common due to undercutting of slopes by fluvial erosion, shaking during earthquakes and in the monsoon influenced areas by the heavy rainfall leading to saturation and erosion of slopes (Brunsden and Jones, 1984, Owen, 1991; Owen et al., 1995, 1996). Cumulative effects of natural factors and anthropogenic activities have been cited as the causes for some of the potential slide zones of Uttarakhand (Uniyal, 2004). The frequent occurrence of the natural phenomenon of landslide in and around the human habitations in hilly areas also demonstrates that anthropogenic activities like rigorous cutting of slope for developmental activities in the fragile terrain of Himalaya have accelerated the natural processes of mass wasting to a certain extent and in some cases the anthropogenic activities have even advanced the occurrence of natural hazards by many years (Uniyal and Prasad, 2006). The causative factors, for