Dynamics of erosion in the Mediterranean Algerian zone: factors explaining variations in runoff and erosion under different land uses
In Algeria, water and soil, vital resources needed for production, are currently experiencing degradation in terms of quantity and quality. This process continues to grow and is reflected by the decline and exhaustion of these resources and the worsening of environmental problems. In the Algerian watersheds, the erosion processes are creating serious problems: land degradation, siltation of dams, flooding and destruction of infrastructure. In this context, there is a need for research on contingent factors. Our aim in this work was to understand the dynamics of erosion dynamic and to analyze the influence of land use and human activity on the variation of runoff and erosion. The study involved the monitoring of morphological and analytical criteria and an examination of the hydrodynamic behavior of the soil along transects representing sandstone and marl substrates, and along which land use changes successively. The results show the soil variations are due to the dynamics of erosion. The main factors affecting the erosion dynamics are the land use, the characteristics of the land cover and human activity and development. During the measurement period (1993-2004) the maximum runoff coefficient (Kr max) exceeded 30% on bare soil and even reached 60% during exceptional storms (frequency of occurrence &gt; 0.1) on closed and compacted soils. Annual erosion (sheet erosion and rills) was 1.5 to 6.8 t•ha‐1•yr‐1 on bare soil, but overall erosion (sheet and linear (gully)) varies in even greater proportions and may reach record values (54 t•ha‐1•yr‐1). Relevant indicators are those relating to the soil and its surface state: soil characteristics, closed and open surfaces, roughness and soil cover, and those indicators related to the rainfall event (intensity, height and frequency).The effect of the slope is not negligible but can be reduced by a judicious use of the sloping terrain.