Historical aspects of soil erosion in the Mejerda catchment, Tunisia

Agricultural use and related water erosion leads to significant changes in the sedimentological and hydrological characteristics of watersheds and thus means negative consequences for rural development. This research work aimed at putting present-day soil erosion of the important Mejerda catchment in to a historical context. The catchment of wadi Mejerda in northern Tunisia has experienced soil erosion due to weather and human impact during thousands of years. We used historical texts and results from archeological research that go back to 1000 B.C. as well as data collected during the last century. Soil erosion from different types of agricultural landscape management was analyzed together with information on the soils’ production potential, hydrographical network, and flood frequency. The results showed that water erosion has increased the hydrographic network by 65 km and increased the deltaic plain as much as 15 km2/century. The soil productivity has, however, also decreased significantly. Moreover, due to river choking, the number of overflowing occurrences has multiplied over the last century. Finally, it is shown that water erosion follows a specific cycle of degradation throughout the watershed. These findings could be considered for better water and soil management in the context of semiarid areas