Evaluation of sedimentation vulnerability at small hillside reservoirs in the semi-arid region of Tunisia using the Self-Organizing Map

Small hillside reservoirs are fundamental for the sustainability of the water resources in the semi-arid region of Tunisia, where the government has constructed small dams since 1990. However, flash floods and severe erosion are jeopardizing the life of those small hydraulic structures prompting an assessment of the vulnerability of semi-arid catchments to erosion. In this study, we investigated the degree of erosion in 23 catchments by considering six variables related to erosion: the specific sediment yield, the hypsometric integral, the topographic index, the rainfall-related attribute as well as lithological and vegetation cover. More importance was assigned to the hypsometric integral and how it controls erosion vulnerability. The Self-Organizing Map of Kohonen, a robust clustering method, was implemented to analyze the patterns of the six variables. The results revealed four groups of catchments with different vulnerabilities to erosion. In addition, there is a global trend of increasing erosion risk from the Southwest to the Northeast of the semi-arid region of Tunisia.