Assessment of erosion: use of nuclear techniques and conventional methods—case of the Fergoug watershed, Algeria

The importance of the soil degradation in the Mediterranean area, more particularly in Algeria, has revealed the need for a diagnosis of the erosion processes’ dynamism. In this context, the present work discusses the results obtained by different approaches (conventional methods, Revised Universal Soil Loss Equation (RUSLE), and fallout radionuclides (use of FRNs)). The use of nuclear techniques (FRNs) such as Cesium-137, Lead-210, and Beryllium-7 as tracers can provide an invaluable amount of information on rates of soil loss that is associated with sheet and rill erosion as well as on the redistribution and transfer of that sediment within the landscape. This work mainly presents the results obtained by the application of nuclear isotopes. In the Fergoug watershed study, the use of conventional and nuclear methods has led to converging results. The latter can be summarized as follows: sheet erosion from 1.5 to 10 t·ha −1 ·year −1 for bare soil and 0.1 to 4 t·ha −1 ·year −1 for cultivated soil. The use of the RUSLE method has shown that erosion is medium to very high (1 to 33 t·ha −1 ·year −1 ). Estimates of erosion by Cesium-137 ( 137 Cs) provided a good understanding of the distribution of the isotope at the slope level and therefore of erosion. The erosion rate is from 26 to 42 t·ha -1 ·year -1 , depending on the models used. On the other hand, sedimentation reached 35 and 55 t·ha -1 ·year -1 downstream of the slopes. The variation of 137 Cs between transects and along the same transect is linked to erosion. The 137 Cs method has provided a great deal of information and thus constitutes, by its accuracy and speed, an effective and valuable tool for assessing erosion for medium term (50 years) and monitoring the impacts of land use. It can enable one to overcome the various constraints and limits encountered in the various conventional approaches. It thus appears to be an essential alternative or an effective tool to supplement the conventional methods.