amrouni, oula institut national des sciences et technologies de la mer - laboratoire du milieu marin, Salammbô, Tunisia , medina, raúl universidad de cantabria - environmental hydraulics institute, Santander, Spain , abdeljaouad, saâdi campus universitaire tunis el manar - faculté des sciences de tunis - laboratoire de ressources minérales et d’environnement, Rommana, Tunisia

Morphodynamics of a microtidal sandbar beach under storm condition: case of the Mahdia nearshore, Tunisia

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The effects of global climate change are illustrated by rising sea level and the increase of intensity of storm events. The highest waves generated attack the upper beach. This combination of the two factors would produce severe erosion, threatening the coastline. The Ras Dimas-Cape Africa (Mahdia, Tunisia) coastline and adjacent areas are particularly exposed to such impact. The aim of this study is to assess the response of wave-dominated sandbar beach under storm events in two different cross shore cases in the Mahdia beaches. The methodology adopted is based on the surveyed bathymetry of the nearshore (2004-2006), completed with the morphodynamic numerical model SMC (Tunisian SMC software, Hispano- Tunisian project of coastal rehabilitation, TUNEROSION). The model has been developed and validated by the Spanish Government and the Ocean and Coastal research Group (GIOC) (University of Cantabria, Spain). Coastal modelling provides the wave high and wave induced set-up created by breaking wave and the sediment transport volume calculated as a function of local conditions. The response of sandbars to storm condition is moving onshore and migrates seaward. The morphodynamic result is however an accretion of the nearshore under the storm wave at the center of the bay (two sandbars with gentle slope). Nevertheless, in the southeast beach, where we find single sandbar, the sediment budget is characterized by shoreline retreat during high wave energy and the migration offshore of this sanbar beach.

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Storm , beach profile , sandbar , SMC , PETRA , morphodynamics , Mahdia , Tunisia

bulletin de l’institut scientifique, section sciences de la terre

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