Processes involved in the morphodynamic evolution of Zemmouri Bay: hydro-sedimentary and cinematic modelling of the coastline.

Résumé

The Central Algerian coast, between Cap Matifou in the East and Cap Djinet in the West is characterized by a very dynamic and complex coastal area, which allows studying and better understanding the impact of anthropic and natural processes on sediment dynamics. During these last years, the coastal of the bay of Zemmouri was exposed to many constraints related to the human activities, such as the abusive extraction of sand in the beaches (beache of Zemmouri, beach of Mandoura) that of the beds of wadis (wadi of Isser, wadi of Corso,,,,,). This situation gives this coastal a high vulnerability to coastal risks. The main objectives of this research is to study the coastal geo-hazards, among which we cite: coastal erosion, marine flooding. In the morphodynamic context, the results of the morphodynamic parameters of the sandy beaches show a more or less intermediate comportment along the coast of Zemmouri. The spatio-temporal evolution of the shoreline during the period (1980 -2017), allows to have that the erosion is more important in the Eastern part than the Western and Central part.To had better understand the mechanisms at the origin of erosion, a complementary study on the classification of beaches was carried out. Then a study on the spatio-temporal evolution of the seabed. In order to have an idea on the morpho-hydro-sedimentary functioning of the bay of Zemmouri. For the hydro-sedimentary context, we have used a Mike 21 numerical and Arc Gis mapping software. The results of this model show that the underwater morphology of the continental shelf of the bay of Zemmouri is characterize by relatively irregular seabeds; this model also showed that the study area is submit to the influences of swells of sectors 315°N, 45°N and 360°N. The cartography of the coastal vulnerability with regard to the sea level rise has permitted to define and identify the coastal risk areas. The results show that 24, 58 km of the Zemmouri coastline, i.e. 52 %, presents a high to very high vulnerability. The mapping of marine flooding is based on the use of the method of Hoozemans et al. 1993. The principal results of the simulation of the phenomenon of marine flooding show that the land most affected by the maximum level of flooding (5 to 6 m) is essentially the low-lying coasts (the beaches and wadi beds). Coastal erosion and marine flooding are constraints that must be integrated into coastal strategies and plans.

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