In recent past we have witnessed nature’s fury in Uttarakhand state of India. There were clearly two flood events in Mandakini valley on 16th and 17th June of 2013 and later was associated with the breach of Chorabari Tal. The present study was carried out to simulate flood plain and to map inundation area of Alaknanda, Mandakini and Bhagirathi rivers in the region of Rudraprayag and Uttarkashi of Uttarakhand respectively using hydraulic modeling on GIS based HEC-GeoRAS platform through detailed parameterization of river channels. A high resolution Geoeye image from Google earth was used for visualization, LULC extraction, delineation of flood hazard maps and to increase accuracy of hydraulic model. The cartosat DEM of 1 arc degree vertical resolution was used to extract elevation data for hydraulic model. Keeping in view recorded rainfalls during June 2006 (i.e. 21.24 mm/day at Rudraprayag and 9.70 mm/day at Uttarkashi) and recent June 2013(i.e. 105.2 mm/day at Rudraprayag and 267.76 mm/day at Uttarkashi), six flood plains for each river were simulated using six flow data corresponding to one bank station at every reach. Overlaying of flood plains on land use layer resulted in estimates of losses for different scenarios. Vulnerability analysis was also performed in different flood plains. A considerable loss to agriculture, built-up areas and roads was found in Uttarkashi region while due a good distance of agriculture from river plain, there was no loss to agriculture in Rudraprayag area but built-up areas and roads were found to be affected by flood water.
