Validation of Flash Flood Simulations Using Satellite Images and Community-Based Observations—Impact of Infiltration and Small-Scale Topographical Features

Abstract

AbstractThis work is aimed at investigating flash floods in the region of El Gouna, Egypt, by using a 2D robust shallow-water model that incorporates the Green-Ampt model to find the most realistic infiltration setting for this desert area. The results of different infiltration settings are compared to inundation areas observed from LANDSAT 8 images as well as to community-based information and photographs to validate the results despite scarce data availability. The model tends to overestimate infiltration in the study area if tabulated Green-Ampt parameters for the dominant soil texture class are considered. Specifically, bare soils with no vegetation tend to develop a surface crust, leading to significantly decreased infiltration rates during heavy rainfalls. Comparing the results of different infiltration settings with the observed data showed that the crust approach or the consideration of sandy clay loam instead of sand led to more plausible results for the considered study area than those obtained using the values for sand from two different sources in the literature. Furthermore, small-scale structures, which are not appropriately captured in the original digital surface model, but significantly affect the resulting flow field, have been included based on the available information leading to much more plausible results.