Hydrodynamic Modeling of Khenifiss Coastal Lagoon, Southern Atlantic Coast of Morocco: implications for Sediment Infilling

• Hamza El Behja ^[1] ; Abdelmounim El Mrini ^[1] ; Driss Nachite ^[1] ; Mohammed Bouchkara ^[2] ; Khalid El Khalidi ^[2] ; Bendahhou Zourarah ^[2]
  1. [1] Abdelmalek Essaâdi University: Tétouan
  2. [2] Department of Earth Sciences, Faculty of Sciences, Chouaïb Doukkali University, El Jadida, Morocco
• Localización: Thalassas: An international journal of marine sciences, ISSN 0212-5919, Vol. 41, Nº. 1, 2025
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Dialnet Métricas: 1 Cita
• Resumen

  • Coastal lagoons offer vital ecosystem services that enhance human well-being and promote biodiversity conservation. The molding and governance of the development and evolution of these ecosystems primarily stem from their hydrodynamic conditions, representing a pivotal factor influencing the majority of physical and ecological processes in lagoon environments. These encompass the distinct characteristics of water level fluctuations and water circulation patterns. These hydrodynamic forces exert a profound influence on various aspects of lagoon morphology, sediment transport, water quality, and overall ecological functioning. Khenifiss, recognized as Morocco’s largest coastal lagoon on the Atlantic coast, is presently undergoing noteworthy transformations, including sediment infilling, dune migration, alterations in its inlet, and the narrowing of the main channel. Consequently, these changes have resulted in a reduction in water surface area, an increase in vegetated shores, a diminished supply of water to the salt flats upstream of the lagoon, and a decline in fish productivity. This study employs modeling techniques to develop a hydrodynamic model that monitors variations in water levels and circulation patterns across different segments of the lagoon. The resulting data will be analyzed to gain a deeper understanding of how tidal influences, wave action, and wind stress interact to shape the lagoon’s dynamics. Special attention will be given to how these factors contribute to sediment infilling within the lagoon’s channels. A hydrodynamic finite element for 2D free-surface flows was used to simulate and describe water level changes and water circulation in the lagoon under tide and wind forcing mechanisms over 15 days. The analysis of water level fluctuations along the main channel unveils a discernible pattern, indicating a gradual decrease in tidal amplitude. Specifically, during spring tide, the maximum tidal amplitude decreases from 2.14 m in the inlet to 2 m in the inner main channel. Conversely, during neap tide, the maximum tidal amplitude is observed at 1.06 m in the inlet and 0.8 m in the inner main channel. Current directions align with the channel’s main axes, resulting in a complete 180-degree reversal between incoming (flood) and outgoing (ebb) tides. The highest values of current velocity are observed at the entrance and the narrowest portion of the central channel of the lagoon. During spring tides, the velocity exceeds 1.4 m/s at the entrance, while during neap tides, it does not exceed 0.7 m/s, creating areas of complete calm. Tidal asymmetry in Khenifiss lagoon results in dominant flood tides, with stronger and more prolonged inflows compared to ebb tides, contributing to the sediment infill issue in the lagoon. This study is an initial attempt to simulate the lagoon’s hydrodynamics using a modeling approach. If developed further into a sediment transport model, it holds the potential to offer viable solutions to the lagoon’s urgent sediment-related concerns, particularly the infilling of both the inlet and the main channel, which play a vital role in the lagoon’s survival.