Geomorphology-based index for detecting minimal flood stages in arid alluvial streams (original) (raw)
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Flash Flood Risk Estimation of Wadi Qena Watershed, Egypt Using GIS Based Morphometric Analysis
Applied Environmental Research, 2018
Flash flooding is one of the periodic geohazards in the eastern desert of Egypt where many parts of Upper Egypt, Sinai, and Red Sea areas were hit by severe flash floods, for example in 1976, 1982, 1996 and January 2010. The hazard degree for each sub-basin was determined using the approach developed by El-Shamy for assessing susceptibility of sub-basins to flash flooding risk. To identify at-risk sub-basins, two different methods were applied. The first method is based on the relationship between the drainage density and bifurcation ratio, and the second one uses the relationship between drainage frequency and bifurcation ratio. The three morphometric parameters (the bifurcation ratio, drainage density, and stream frequency) were extracted and calculated for each sub-basin of the watershed. Based on the final hazard degree resulting from the two methods, a detailed hazard degree map was extracted for all sub-basins. The results illustrate that there are no sub-basins with low risk ...
2017
Remote Sensing techniques with GIS were used to evaluate flash flood hazard in Wadi Qena. Wadi Qena represents a large, wide, dry and long valley slopes down from the south of the Galala height to the town of Qena. Its southern stretches considered as very promising land for the agriculture expansion. The surface area of Wadi Qena is about 15,588 km 2. Flash flood hazard in Wadi Qena is evaluating by the integration of some quantitative geo-morphometric parameters and Tropical Rainfall Monitoring Mission (TRMM) satellite data of the last flashflood in 28th January 2013. Streams were automatically extracted from ASTER DEM data. Wadi Qena classified into 151 sub-basins. The various morphometric parameters of Wadi Qena sub-basins have been computed. flash flood hazard map of the most dangerous sub-basins was prepared by combining all the spatial layers of morphometric parameters for the sub-basins included in it by GIS analysis. the majority of the sub-basins range from low to medium hazard degree Except one sub-basin located at the eastern part of the wadi is classified as high hazard degree. This technique may help in evaluating the hydrographic basin and offers a base map delineating both recharge and flooding area. Flash flood has double-edged effects one is a destructive and life terminator, the second is a beneficent, if it can be controlled and directed for the development the community. This technique helps in diminishing the flood hazards and increases recharging the shallow aquifers.
A Hydrological and Geomorphometric Approach to Understanding the Generation of Wadi Flash Floods
The generation and processes of wadi flash floods are very complex and are not well understood. In this paper, we investigate the relationship between variations in geomorphometric and rainfall characteristics and the responses of wadi flash floods. An integrated approach was developed based on geomorphometric analysis and hydrological modeling. The Wadi Qena, which is located in the Eastern Desert of Egypt, was selected to validate the developed approach and was divided into 14 sub-basins with areas ranging from 315 to 1488 km 2. The distributed Hydrological River Basin Environment Assessment Model (Hydro-BEAM) was used to obtain a good representation of the spatial variability of the rainfall and geomorphology in the basin. Thirty-eight geomorphometric parameters representing the topographic, scale, shape and drainage characteristics of the basins were considered and extracted using geographic information system (GIS) techniques. A series of flash flood events from 1994, 2010, 2013, and 2014, in addition to synthetic virtual storms with different durations and intensities, were selected for the application of this study. The results exhibit strong correlations between scale and topographic parameters and the hydrological indices of the wadi flash floods, while the shape and drainage network metrics have smaller impacts. The total rainfall amount and duration significantly impact the relationship between the hydrologic response of the wadi and its geomorphometry. For most of the parameters, we found that the impact of the wadi geomorphometry on the hydrologic response increases with increasing rainfall intensity.
Morphometric analysis of low mountains for mapping flash flood susceptibility in headwaters
2022
Morphometric indices from high-resolution DEMs can contribute to the estimation of flash flood susceptibility in mountainous areas. We have screened 25 morphometric indices commonly used in literature, and based on a correlation matrix, selected those which showed the strongest relationship with flash flood generation: area (A), drainage texture (Rt), drainage density (Dd), elongation ratio (Re), form factor (Ff), lemniscate method (k), Gravelius coefficient (GC), forested area (Fa) and relief ratio (Rr). Among them Dd, Rt and Rr were in direct relationship with the probability of flash flood generation, while A, Re, Fa, Ff, k and GC are in inverse relationship with the intensity of flash floods. Our summary map shows the prioritization of the subwatersheds on a scale of 0 to 9. The flash flood risk ranking was empirically verified using 20-year water regime data obtained from 14 official stream gauges. Our conclusions only partially agree with former observations which may be expla...