The elaboration of vulnerability maps remains a fundamental tool in the management and study of flood-related risks (floods and hydric erosion). This study aims to develop these maps through Geographic Information Systems (GIS), which can be used as basic documents for any action of developments in the watershed of Oued El Maleh in M'Saken region (eastern Tunisia). This region is characterized by the weakness of its topography and its slopes. Its rainfall, generally irregular and sometimes aggressive and torrential, can transform rivers which are often very little marked in nature, to real torrents with great erosive power, able to lead to flooding. This natural vulnerability is accentuated by the spreading of several urban areas in submersibles zones, in particular that of M'Saken, and by the development of the agricultural lands. In this context, the present study focused on the collection of digitized topographic maps, of Landsat images and others of Google Earth in order to create an integrated database in a Geographic Information System. The results are thematic maps which make it possible to define and analyze, by superposition of several layers of information, the natural environment; and to carry out a spatial analyzes required to characterize, map, and study the vulnerability.

The watershed Sidi Salah, located in the north of Sfax (Tunisia), Knew an important water and soil conservation installations. These installations present certain operating anomalies that make them unable to well manage the hydric erosion phenomenon. This work aims to identify those anomalies and to characterize the responsible factors in order to promote the sustainable management of water and soil at the level of the watershed. The study was based on the photo-interpretation of the satellite images with high resolution, the field observation and the chemical analyses of the soil samples taken in various sites of the watershed. The results allowed us to reveal some anomalies as the loss of embankments and the destruction of the masonry installations. The responsible factors are mainly naturals, related to the turbulent water flows and the soft lithology of the soil rich in gypsum and limestone.