Assessment of Soil Erosion Risk from Runoffs under Arid and Semi-arid Climate Zones in Africa

Soils are a vital natural resource that deserves more attention and affection, because they are full of everything that living beings need to survive. Now, soil hydric erosion is a phenomenon that causes serious problems of flooding and limiting food production in semi-arid climate zones, leading to a chronic socio-economic and environmental disasters. This process is further exacerbated by the ever-increasing global warming. This study aims to better understand the processes and consequences of water erosion, in order to better prevent the risks that could be associated with the rising of global temperature. The study area is located in the semi-arid climate of Isser watershed in the northern-west of Algeria. Soils of the area have a silty-clay texture. The surfaces are covered with little gravel (8%), covered to 72% of vegetable debris and are cracked up to 53%. These characteristics may reduce the runoff velocities and protect soils against erosion. However, clearing, overgrazing and farming systems favor runoffs that cause transfers of sediments through the destruction of the surface physical-chemical properties and thereby its natural structural stability. The study shows a slowdown in the infiltration rate of runoff water when soils are severely dehydrated. This may be an explanation for the paradoxes of the recent floods in arid and semi-arid areas of the world. Soils aridification due to global warming could increase its cracking and damage their structural stability. This climatic phenomenon will result in the recurrence of floods and the massive infiltration of surface water into groundwater, thus generating their pollution. The study also shows that the sum of all chemical properties (moisture, OM, soil carbon, calcite, and total nitrogen) in percentage is highly correlated with soil structural stability. Therefore, the key factor in mitigating this process would be to maintain a sufficient level of organic matter in the soils.