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Abstract
The cartography of floods by two different approaches enabled us to determine the limits and the advantages of each one of them. This cartography has been applied to the El Maleh basin situated in the South-East of Morocco. The HEC-RAS approach consists of a combination of the surface hydrologic model and the digital terrain model data. This combination allows thereafter the mapping of the flood zones by the use of the WMS software. Thus it can predict the probability occurrence of floods at various frequency times and determine the intensity of the flood (depth and velocity of flood water) inside the El Maleh river by using the existing hydrological data. Otherwise FHI method approach introduces a multi-criteria index to assess flood risk areas in a regional scale. Six parameters (flow accumulation, distance from drainage network, drainage network density, slope, land use, and geology) were used in this last method. The relative importance of each parameter for the occurrence and severity of flood has been connected to weight values. These values are calculated following an Analytical Hierarchy Process: AHP, a method originally developed for the solution of Operational Research problems. According to their weight values, information of the different parameters is superimposed, resulting to flood risk mapping. The use of the WMS model allowed us to accurately map the flood risk areas with precisely flood heights in different levels. However, this method is only applicable for a small portion of the basin located downstream of the hydrological station. Otherwise, the FHI method allows it to map the entire basin but without giving an indication of the water levels reached by floods. One method does not exclude the other since both approaches provide important information for flood risk assessment.
Highlights
Flood is considered to be the most common natural disaster worldwide during the past decades, producing many environmental and socio-economic consequences within the affected flood plain [1] [2]
The TIN is a type of DEM created from digital contour data sourced from the GDEM-ASTER website
To verify the inconsistency of the matrix, we propose to use the Analytical hierarchy process (AHP) method which consist of the calculation of the consistency ratio (CR) which permit the comparison between the consistency index (CI) of the matrix in question versus the consistency index of a random-like matrix (RI)
Summary
Flood is considered to be the most common natural disaster worldwide during the past decades, producing many environmental and socio-economic consequences within the affected flood plain [1] [2]. A flood is an overflow of water that submerges land, and may cause damage to agricultural lands, urban areas, and may even result in loss of lives [3] [4]. Flood hazard maps are useful tools for planning the future direction of city growth, and are usually used to identify flood-susceptible areas [5]. Flood zonation mapping and hazard analysis for different areas often involve multiple criteria/factors that have to be geographically related to one to another [6]. Hydrodynamic modelling approaches have been used by various researchers to provide flood susceptibility mapping [7]. Combination of HEC-RAS and GIS has a great capability in simulation of flood hazard zoning [9] [10]
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