The watershed of the upstream course of Oued el Khil (South-East Tunisia) Geomorphological study

The watershed of the upstream course of Oued el Khil is part of south-east Tunisia, of the Matmata-Dahar plateau also called Jbel Demmer. It covers parts of the governorates of Medenine and Tataouine between the delegations of Beni Khadeche, Ghomrassen and Bir Lahmar. This watershed is encased in a relief of a plateau of modest altitude divided into three tiered plateaus. The study area is characterized by a variety of geological rocks. Its monoclinic cuesta type structure presents a double to triple cuesta and forms of witness buttes and outliers.

The quaternary landforms and deposits are well linked to climate change which has manifested by dynamics of water and wind action. They present deposits of coarse elements (blocks, pebbles, gravel ...) and other fine (silts and sands) and sometimes mixed (blocks, silts, pebbles and sands ...). At the level of the Jurassic cornices and on the slopes, develop various deposits and quaternary landforms such as taffonis, friable colluvium and consolidated one by limestone crust and landslides. Mini-glacis with or without crust and mini-glacis-terraces extend over the foothills, and terraces at the bottom of the valleys. These landforms were established during the different periods from the Lower Pleistocene to the Holocene.

Currently, the most remarkable morphodynamic evolution is manifested by water erosion which is characterized by stripping, badlands, receding heads from ravines and the destruction of the Jessour. The manifestation of wind erosion corresponds to the development of Nebkas, regs, dunes and veneers.