Flood Plain Modelling using River Hydraulic Modelling Approach: A case study
This research work was carried out at ICAR-IARI, New Delhi, India. The presentation of the research was delivered at ESRI-India Conference. This research work was conferred as the best paper award.
Flood inundation is a natural disaster which almost every year accounts for loss of properties as well as human lives in different regions across the world. The present study was carried out to simulate and map inundated areas 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.
In year 2013, there was huge devastation in Rudraprayag and Uttarkashi area due to heavy flooding. This study estimates the loss occurred during this event as well as presents future flooding scenarios through simulation modelling. To carry out the research, a high resolution imagery of Google Earth was employed for visualization, LULC extraction, delineation of flood hazard maps and to increase accuracy of hydraulic model. A digital elevation model of Cartosat-1 stereo data (1 arc degree vertical resolution) was used to extract elevation related information.
Total six flood plains for each river were simulated using river flow data. The first river flow data having least value was the real flow data related to flood event of 2013 while other flow data were hypothetical and were used to simulate flood plains so that future scenarios could be generated as well as mapped and loss to various LCLU categories can be measured. The velocity mapping was also performed through water surface profiles.
It was observed through the analysis that flood events of similar degree of 2013 or higher may account for considerable loss to agriculture, built-up areas and roads. In Uttarkashi region, agriculture, built-up areas and roads were found to be damaged while due to a good distance of agriculture from river plain, there was no loss to agricultural land in Rudraprayag area but built-up areas and roads were found to be affected by flood water.
This type of simulation study is very much helpful to policy makers and disaster managers for their preparedness to any forthcoming flood event. Keywords: HEC Models, ArcMap, HEC GeoRAS, Flood simulation Modeling, Inundation Mapping, River Hydraulic Modeling.