干旱区生态环境知识资源中心

The region of Ain Sefra is an arid region suffering from sand encroachment. In this study, we are calculating the shifted sand quantity and efficient wind directions during a period of 30 years (1985 to 2015) in order to classify the danger. The study shows that efficient winds in the region are characterized by their potential drift estimated at 220 till 329. This classifies the region as medium. Besides, the resultant drift potential is 76 to 99 with a migration coefficient of 0.3 which gives a medium classification to the zone and proves the Aeolian erosion complex system and its interrelation with other factors. Efficient winds generally blow from South-west to North-east with an angle of 234 degrees. Furthermore, there are other directions causing sand drifting. Sand movement quantity is estimated between 23.03 and 15,224 m(3)/m/year according to effective wind threshold speed, which is 5 to 6 m/s. Autumn is the period when sand mobility is higher, but it decreases in winter. On the other hand, sand potential movement was well shown through satellite imagery between 1985 and 2015. Indeed, it closely corresponded to the previous study. It showed sand movement direction from South-west to North-east, and sand surface increase reached 16.44% of the global zone surface. Whereas, it decreased - 2.5% between 1985 and 2015. There is an important concentration of sand accumulation under the western mountain foothills along which sand moves. This shows that the ground particularities play a crucial role in this phenomenon.