The Effect of Erosion Control Practices on the Vulnerability of Soil Degradation in Oued EL Malleh Catchment using the USLE Model Integrated into GIS, Morocco

Abstract

Water erosion is a major problem in semi-arid region where decreases the dam reservoir design capacity, agricultural yield productivity, and increases other environmental impacts. This phenomenon is widely predominant in Morocco, particularly in the Oued El Malleh watershed in the Casablanca Settat region. Most soil erosion happens gradually which makes it challenging to notice. Hence, the monitoring of soil degradation under a modelling-based, such as Geographic Information System (GIS) can help the decision-makers to quantify the eroded soil and choose the best mitigation measures. Many erosion control practices have been implemented in The Oued El Malleh watershed in 2008, which covers a surface area of 3127 km2. Even though, the soil erosion still dramatic in the region. To date, no one has attempted to work on the impact of the soil conservation factor at the level of the Oued El Malleh watershed, as well as monitoring the sustainability and effectiveness of the water erosion control practices already implemented. Therefore, periodic monitoring and evaluating soil degradation is imposed. To achieve this purpose, we used the Universal Soil Loss Equation (USLE) to spatially assess water erosion in the study area, to find out the most vulnerable area to erosion, to notice the efficiency of the actual erosion control practices and elaborate on new mitigation measures. The results of this study have been shown that the rate of soil loss in the Oued El Malleh, including the actual control erosion interventions, varies from 0 to 90 t. ha-1.year-1; with an average erosion rate of 0.65 t. ha-1.year-1. The study area characterized by a moderate to severe slopes, in some area, the Length and Steepness Factor LS exceeds 90 %. For this reason, we have been elaborated new soil loss map, including soil conservation measures according to the slope. The soil loss rate; following this approach; varies from 0 to 64 t.ha-1.year-1. Furthermore, the followed approach could be valuable for assessing the soil loss in similar area.
 HIGHLIGHTS
 
 Casablanca-Settat agricultural lands become progressively infertile and depleted soils
 Soil degradation by water erosion is a tidal problem in the Oued El Malleh watershed
 Soil loss was estimated at a watershed level using the USLE model and ArcGIS tool
 The soil loss rate is estimated to be 0.65 t. ha-1.year-1, and the average sedimentary yield is found at 8.27 t. ha-1.year-1
 Sustainable land management can limit soil degradation
 
 GRAPHICAL ABSTRACT