Height above nearest drainage and application in flood inundation mapping in China

Local topography, a major governing factor of surface water movement, plays important roles in hydrological responses and associated geographical and ecological processes．But data sets highlighting local topographic characteristics covering contiguous China are lacking, let alone its wide applications．The height-above-nearest-drainage (HAND) concept, which derived from classical digital elevation model (DEM), was used to produce HAND data set for China with grid sizes of 250 and 1 000 m by SRTM DEM, then HAND data were applied for inundation mapping．Library of inundation maps for scenarios of water level rise of 1−10 m from low-flow condition along rivers and streams were developed．Such maps cover contiguous China with horizontal resolutions of 250 and 1 000 m．The great flood with peak discharge in July of 2020 along Pi River tributary of Huai He River was studied．The inundated areas retrieved from SAR images on July 20th of 2020 and simulated by HEC-RAS were compared with HAND-based inundation maps．Complementary to DEM with overall features of topography, HAND was found to signify local topographic characteristics over large regions．HAND could therefore be used as a simple but feasible and reliable approach, to map flooded areas．HAND data set of China produced in this work highlights localized topography for geography-related research．HAND-based inundation maps may shed light into flood risk management in China．