Modeling the Hydrological Impacts of Vegetation Cover Changes in the Upper Oum Er-Rbia Watershed (Morocco)

In Morocco, the mountainous areas are often exposed to bulky and vicious flows of water and sediment. This process is exacerbated by the decrease in vegetation cover and the disruption in rainfall-runoff conditions, that frequently cause significant flooding. By exploring the main hydrologic elements of these processes, it is possible to understand the behavior and hydrological response of watersheds and thus plan accordingly. In this study, we focused on determining the morphometric characteristics of the upper Oum Er-Rbia River basin (UOERRB by assessing/ evaluating land use and land cover changes for a period of 32 years (1984-2016). We applied the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) to simulate four daily hydrological events. The concentration time is 7.7 hours. The four storm events examined to calibrate and validate the simulated outflow at the outlet indicate a good agreement between the hydrographs of the measured and simulated flows, with an average Nash-Sutcliffe efficiency (NSE) value ranging from 0.63 to 0.76. Between 2002 and 2016, we notice an average a 6.21 percent increase in vegetation cover of with annual rainfall increasing from 690 to 714.1 mm/year These results can contribute to a better understanding of the hydrologic processes and in better estimating the return flows and thus guiding management decisions and developments in the UOERRB.