Analysis of the hydrosedimentary circulation in the mouth of dominated wave environment using grain size analysis, wave/current modeling and image processing case of the principal Rivers in Zemmouri bay

This paper focuses on hydrosedimentary circulation in the mouth of dominated wave environment using grain size analysis, wave/current modeling and image processing, applied to the Zemmouri bay rivers. To identify the sediment dynamics in this area, various methods and materials were used, starting with a detailed description of the meteo-oceanographic conditions on the sampling dates (March 24th, 2022) and (December 18th, 2022), followed by a granulometric analysis of collected sediments of various sizes from fine to coarse, to extract the main granulometric parameters such as Mz, S₀ and Ski which are used as an input for sediment transport modeling using the GSTA model. Results showed a good correlation between wind directions and sediment trend path, mostly directed North-East in the winter and West in summer with a coastal drift current responsible for supplying the beach and transporting fine materials from the river. This study highlights the dynamic of the mouth of Boudouaou Rivers showing very dynamic and sensitivity to seasonal meteorological variations. Moreover, the littoral drift essentially controls these lateral sedimentary movements during oblique wave conditions. Offshore directed sediment transports occurred during moderate (less strong) wave conditions are possibly influenced by “windows” observed in the surf line that could be related to rip currents. In addition, results show that surface currents have a major influence on sediment circulation at river mouths by mobilising them in the nearshore or even in the shoreface areas and maximum sediment transport occurs when the directions of the waves and surface currents are combined. On the other side, SEDTRANS05 model (Neumeier et al. 2008) showed that sediments delivered to the open sea could be mobilized or remobilized by the hydrodynamic conditions prevailed during the events studied. Finally, the XRF results showed valuable information on their mineralogical nature and the continental origin of the sediments collected at the mouths of the study area. This study highlighted the importance of combining several methodologies for studying the hydrosedimentary dynamics of rivers which can help to better understand the coastal dynamics of microtidal coasts.