LAUSR

Abstract This study presents a method to map the risk of submersion of the lower Tunisian coasts, by taking as an example the coastal sabkhas system of a part of the bottom of the gulf of Hammamet between the sabkhas of Sidi Khlifa and Halq El Minjel. Total Water Levels (TWLs) were estimated by considering a water level rise for 2100 estimated by IPCC scenarios (2007) and the runup during storms. Similarly, local hydrodynamic parameters such as tidal level, storm surge, wave setup, swash and coastal erosion have been taken into consideration. The mapping approach of potentially submersible areas is based on geographic information system (GIS) modeling. Based on a static method, the approach relies on the crossing of topographic data and extreme water levels in order to assess potentially floodable areas. The mapping application has shown that the areas that are likely to be annexed to the sea are important (17.5 km2). Part of the Halq El Minjel sabkha of 16.1 km2 will be transformed into a permanent lagoon. Thus, coastal wetland ecosystems will be threatened by changes in living conditions since the rather saline biocenosis will be transformed into euryhaline and eurytherm lagoon biocenosis. However, reforestation and conservation of the coastal dune in these low-lying areas could help protect the backshore from expected risk of storm surges.