Evaluating urban flood hazard index (UFHI) of Dehradun city using GIS and multi-criteria decision analysis

Urban flooding is one of the major issues in Dehradun city. Lack of preparedness and lack of flood hazard zonation at city level resulted in increasing number of life losses every year. This research aims to evaluate urban flood hazard index (UFHI) and generate flood hazard zonation map, which can be used for prioritizing flood mitigation strategies and efficient allocation of resources in Dehradun city. UFHI is evaluated by linear combination of weighted overlay analysis of indicators using multiple criteria decision analysis. Here Satty’s AHP matrix is used for determining the weightage of each indicator. These indicators are integrated in geographic information systems as layers, resulting in a composite index map. Remote sensing data from Landsat 8 OLI, 2015; DEM 2013 of CARTOSAT-I data, and Survey of India toposheets, are used for creating base layer of the city. Six indicators which include, elevation, slope, drainage density, land use/land cover (LULC) runoff, flood water depth, and distance from river stream, are used for evaluation. As a result of analysis, urban flood hazard zones are identified and classified into—very high risk with 10 wards (16.67%), high risk with 20 wards (30.33%), medium risk with 22 wards (36.67%) and low risk with 8 wards (13.33%); out of the total 60 wards (smallest administrative unit) in city. The study indicates that two parameters namely LULC runoff and proximity to river stream have a direct co-relation to high flood hazard zones in Dehradun city. As a further scope of research, a greater number of indicators and micro-level studies can be taken up for more accurate results.