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 Mo...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.展开更多
The construction of small dams and hillside reservoirs is a common practice for dealing with erratic and unevenly distributed rainfalls in arid and semi arid areas. Moreover, these small hydraulics structures are reco...The construction of small dams and hillside reservoirs is a common practice for dealing with erratic and unevenly distributed rainfalls in arid and semi arid areas. Moreover, these small hydraulics structures are recommended as a solution to adapt to climate change in rural areas. They are fundamental for the sustainability of the water resources. However, these dams are potential sinks for upstream sediment. Therefore, it would be useful to monitor and measure the amount of sediments in small dams because it is necessary to understand siltation and better functioning of these vital structures. This control and these measurements require the application of the bathymetry or topography surveys which is too expensive for the responsible of these small dams. In this context, this paper proposes a simple and low cost method called: Triangulation of the estimated silted level. This method is based on direct measurement of the accessible silted level in dam. This new method is compared with another method based on the initial Elevation-Capacity curve of dam, usually used when the bathymetry is not attainable. The results of both of them have been verified with those of the bathymetry and electrical tomography methods and validated the proposal method as the most approximate. Therefore, this method is recommended as a new direct and simple technique to evaluate the amount of silting in small dams and hillside reservoirs.展开更多
文摘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.
文摘The construction of small dams and hillside reservoirs is a common practice for dealing with erratic and unevenly distributed rainfalls in arid and semi arid areas. Moreover, these small hydraulics structures are recommended as a solution to adapt to climate change in rural areas. They are fundamental for the sustainability of the water resources. However, these dams are potential sinks for upstream sediment. Therefore, it would be useful to monitor and measure the amount of sediments in small dams because it is necessary to understand siltation and better functioning of these vital structures. This control and these measurements require the application of the bathymetry or topography surveys which is too expensive for the responsible of these small dams. In this context, this paper proposes a simple and low cost method called: Triangulation of the estimated silted level. This method is based on direct measurement of the accessible silted level in dam. This new method is compared with another method based on the initial Elevation-Capacity curve of dam, usually used when the bathymetry is not attainable. The results of both of them have been verified with those of the bathymetry and electrical tomography methods and validated the proposal method as the most approximate. Therefore, this method is recommended as a new direct and simple technique to evaluate the amount of silting in small dams and hillside reservoirs.
