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Analysis and Mapping of Water Erosion Vulnerability Using GIS for the Mghila Watershed, Northwest of Algeria

Ratiat Abdelkader, Haddad Ali, Bouaichi Ilham, Matene Chahrazed Naziha

Archives of Hydro-Engineering and Environmental Mechanics

2023

Vol. 70, nr 1

71--87

Intensification of extreme rainfall-runoff events in arid and semi-arid regions because of climate change induce the water erosion that contributes considerably to the loss of vegetal layers of soils and reduce the storage capacity of dams by silting of transported sediments from the watershed to the impoundment. This paper aims at proposing means for protecting the Mghila dam against silting by identification and delimitation of vulnerable areas to water erosion. This dam, built in the North-West of Algeria, ensures irrigated cultivation. Topographical, geological, and land use characteristics of the watershedwere analyzed using the geographic information system (GIS). Analysis of results has allowed the identification by area percentage four-vulnerability classes with sensitivity to the water erosion: low (18.89%), medium (13.08%), high (65.05%) and very high (8.38%). The spatial distribution of the lithological substratum friability, the vegetation cover and slope degrees have led to the development of an efficient strategy for the watershed management in order to reduce the effect of water erosion on soil degradation and silting of the Mghila dam.

Extreme Rainfall-Runoff Events Modeling Using HEC-HMS Model for Oued El Hachem Watershed, Northern Algeria

Haddad Ali

Archives of Hydro-Engineering and Environmental Mechanics

2022

Vol. 69, nr 1

45--57

Flood forecasting has become necessary for dam management during extreme hydrological events. The lack of streamflow data in ungauged watersheds of arid and semi-arid regions makes the assessment of water resources difficult. In this paper, the Hydrologic Modeling System developed by the Hydrologic Engineering Center (HEC-HMS) was applied to the Oued El Hachem watershed. Calibration and validation of the model have been performed, taking into account the lag time and the curve number CN that is expressed as a function of soil group, land use and antecedent runoff condition. The model was evaluated on the basis of the coefficient of determination, the Nash Sutcliffe Efficiency (NSE), and the percentage differences between peak and volume. Performance indices of calibration showed a good agreements between observed and computed flows. The validation of the model has given satisfactory results. The calibrated model can be used to manage the dam of Boukerdane during extreme rainfall events by forecasting the induced hydrographs from which adequate procedures will be operated in order to ensure the safety of the dam against possible overtopping.