Abstract
Abstract The modified topographic index () based on digital elevation models (DEMs) was employed to delineate flood-prone areas in Mahanadi basin, India. and flood inundation maps were compared to obtain the threshold () beyond which the area is assumed to be inundated by flood and the exponent of the . Scale dependence was also investigated to evaluate the sensitiveness of spatial resolution of the DEMs. DEMs of five resolutions, namely, ASTER global, SRTM, GMTED2010 (30 arc-seconds), GMTED 2010 (15 arc-seconds), and GMTED 2010 (7.5 arc-seconds), were used and ASTER global was preferred due to its low error compared to the remainder. Flood frequency analysis was conducted to obtain the relationship between flood-prone areas and flood magnitude. It was observed that (i) the exponent in the showed little variation, (ii) is reduced with reducing spatial resolution of the DEM, and (iii) error is also reduced as the DEMs' resolution is reduced.
Highlights
Flooding is the most frequent hazard worldwide and occurs due to continuous heavy rainfall and failure of hydraulic structures
It was noted that ER1 was significantly larger than ER2 in all the cases and as the digital elevation models (DEMs) resolution is reduced to 30 m, the error reduces drastically
DEMs are used to calculate the TIm on the basis of which the flood-prone areas are delineated
Summary
Flooding is the most frequent hazard worldwide and occurs due to continuous heavy rainfall and failure of hydraulic structures. Sharma et al (2018), as part of their studies on Northeast India, opined that reliance on satellite products is increasing due to insufficient hydrologic gauge stations These restraints and opportunities suggest simple but effective digital elevation model (DEM)-based approaches that facilitate extraction of topographicbased indices to compute flood inundation area/mapping (Liu & Gupta 2007; Manfreda et al 2008). The proposed methodology is applied to the Mahanadi River basin, India
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