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Prognosis and mitigation strategy for major landslide-prone areas Varunavat Parvat landslide in Uttarkashi

Prognosis and mitigation strategy for major landslide-prone areas A case study of Varunavat Parvat landslide in Uttarkashi township of Uttarakhand (India)

Sequence of

Sequence of sliding events of Varunavat Parvat One month prior to this large scale sliding small slide scarps were observed by the author on Varunavat Parvat above Bus stand, Indra Colony, Masjid Mohalla and Horticulture colony areas and these small slide scarps were witnessing headward shift. This phenomenon was also observed by the geologists of Geological Survey of India and local authorities. DMMC (2003), has predicted the gradual merging of these small slide scarps with active scarp of nearby Tambakhani slide and possible emergence of Prognosis and mitigation strategy 625 Plate 3. Close view of Ramlila Ground slide in late September, 2003. Huge volume of slide debris is accumulated in the back portion of multistoreyed hotels located in the heart of Uttarkashi township Plate 4. Close view of Ramlila Ground slide in October, 2003 with most of the multi-storeyed hotels are completely buried under slide debris along with a part of Rishikesh-Gangotri National Highway. The slide debris and boulders have even spread to the immediate down slope area of Ramlila Ground

DPM 17,5 626 Plate 5. Close view of Horticulture Colony – Masjid Mohalla slide large slide zones in Bus stand, Masjid Mohalla and Horticulture colony areas. Present study has revealed that during the series of cloud burst events of July/August, 2003 the Ramlila Ground slide was triggered as a small slide zone of 40m length and 30m width in the close vicinity of large active slide of Tambakhani on Varunavat Parvat. The active slide zones of Ramlila Ground slide witnessed rapid headward shift during the months of August and September, 2003 and completely merged with the active scarp of large Tambakhani slide on 23 September, 2003, consequently, the slide debris and rolling boulders started hitting multi-storied hotels in the Bus Stand area. It was with in the short span of 24 hours that this slide zone transformed into a large complex slide and multi-storied hotels, commercial and residential complexes at Bus Stand along with 100 m stretch of National Highway were buried under the huge volume of slide debris that gradually extended to Ramlila Ground. On 1 October 2003 the head-ward shifting of another active slide scarp (developed in the upslope of Masjid Mohalla and Horticulture Colony localities of Uttarkashi township) completely merged with the active slide scarp of Ramlila Ground and Tambahkani slide (Plate 1), consequently, yet another large slide zone emerged and slide debris and boulders damaged major part of Masjid Mohalla and Horticulture colony. Causative factors for these sliding events have been analyzed on the basis of satellite image study and detailed field investigations. Interpretation of pre and post disaster satellite images from Indian Remote Sensing Satellites (IRS 1D LISS-III False Colour Composites of 13 April 2003 and IRS-P6 LISS-III False Colour Composites of 16 April 2004; 7 September 2004; 11 April 2005 and 9 August 2005) has been carried out to precisely mark the extent of various landforms, extension of major discontinuities and changes in the landscape after landslide activity of September/October, 2003. ARC GIS 9.0 software was used to create the morphotectonic map through integration of GIS layers of geo-environmental parameters viz. geomorphology, structure and landslide in order to assess the influence of tectonics on the landforms and landslide activity. Response Late in the evening on 23 September, 2003 some locals and officials of Irrigation Department noticed major sliding activity in the form of large heap of debris material

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