Study of Vulnerable and Water Erosion Risk Areas in Sareg Catchment (Central Tunisia) Using Remote Sensing, GIS and P.A.P/R.A.C. Qualitative Approach

Abstract

The study of water erosion has always been a major concern for human societies. Efforts to reduce resulting forms of degradation and to understand their extent have not ceased. This article aims to identify vulnerable and water-erosion-prone areas in the study area. This is achieved through a predictive and descriptive approach leading to the integration of main physical parameters from various sources with direct observation data. The use of remote sensing, GIS and direct observation according to PAP/RAC guidelines has made it possible to prioritize areas at risk of erosion. The basin's lands show a general predisposition to water erosion, with 80% of them experiencing significant, high or very high erosion, including 20% for the last two categories. This situation is linked to a high erodibility of the geological outcrops of the basin (81%), with a low to very low degree of soil protection through vegetation cover (80% of the surface). The descriptive phase shows eroded surfaces of about 18%, a proliferation of ravines (12% of the surfaces) of which 6% are hierarchical ravines and bad lands. The integration phase, while confirming most of the previous data, provides an overview of the trend towards the extension of gullies observed during the descriptive phase to neighboring lands that were not initially subject to erosion. This study shows that a good integration of descriptive and predictive methods can lead to a good understanding of water erosion, which will facilitate solutions to control this phenomenon. It also shows the importance of GIS, remote sensing and their integration with direct field observation in order to produce a document that can be used, at a low cost, as a decision support tool.