The Oum Er-Rbia estuary is located on the Atlantic littoral of Morocco. It undergoes severe clogging due to the sand deposition in its outlet. The current study examined the indicators of the morphodynamic evolution in the littoral system including the Oum Er-Rbia estuary and the neighboring beaches over 1970-2017. The methodology adopted was based on the analysis and the interpretation of aerial photographs and Google Earth images under a GIS environment and field work. The morphodynamic evolution was discussed by taking into account the evolution of hydraulic facilities installed in the watershed area, especially the construction of dams, as well as the dredging works in the Oum Er-Rbia estuary. The results highlight the morphologic evolution estimated in terms of surface units observed in the estuary and the neighboring beaches. The evolution of the littoral system was mainly influenced by the closest dam location and by the dredging works, in addition to the regulation of the river flow by the installation of hydraulic facilities upstream.anthropogenic factors such as hydraulic facilities, engineering works of protection and rehabilitation, dredging, etc. [6][7][8][9][10].The bathymetry and the morphology of an intertidal plain and transversal section of a shallow bottom estuary cause a tide asymmetry that affects the flow duration, compared to the ebb time, and the celerity of the tide current [1,2,[10][11][12]. In coastal environments, the waves generate coastal currents that interact with incident waves and lead to the sediment transportation and the process is favored when the angle between the waves and the coastal line is significant [13][14][15][16]. As a response to coastal hydrodynamics, the alternation of sedimentation and erosion processes in the estuary can generate net sedimentary balances through a tide cycle [17,18].The installation of hydraulic reservoirs in upstream areas affects the hydrodynamic equilibrium and sedimentary balances downstream, due to the flood water regulation and the decrease of the solid sediments supply [19][20][21][22][23][24][25]. Blott) [26] concluded that the morphodynamic evolution of Mersey estuary in England through a period of 150 years was mainly controlled by engineering and rehabilitation works, such as the construction of training walls and dredging. Besides, the importance of other factors, notably sea level change, tide amplitude, wave current, and supply of fresh water was relatively reduced [26].The perturbation of estuarine hydrodynamics is permanently regulated by morphologic transformations through sedimentation and erosion processes mobilized to re-establish the hydrodynamic equilibrium [21,22,27]. The morphodynamic change concerns the estuary outlet, the main channel, and the intertidal plains [19,20,28]. In addition, the morphodynamic change in the estuary affects the morphology of neighboring littoral areas and, consequently, causes the shoreline fluctuation [3,[29][30][31]. Numerous works have analyzed the morphologic evolution of coastal systems t...
L'estuaire d'Oum Er-Biâa est situé sur le versant atlantique marocain, à 60 km au sud de Casablanca. Cette étude concerne le comportement hydrogéochimique du phosphore, élément essentiel dans le fonctionnement des écosystèmes côtiers et océaniques.Le phosphore sédimentaire au niveau de l'estuaire d'Oum Er-Biâa est majoritairement sous forme minérale (76 % à 95 %), avec prédominance de la fraction calcique P-Ca (45 % à 90 %) qui est de nature apatitique non mobilisable. La biodisponibilité du phosphore dans l'estuaire d'Oum Er-Biâa est assurée principalement par la fraction ferrique P-Fe (2 % à 38 %). La répartition spatiotemporelle de cette fraction est contrôlée d'une part, par la nature du sédiment (teneurs en fraction fine et matière organique) en amont de l'estuaire (zone vaseuse) et, d'autre part, par les variations de la salinité et le taux de concentration de minéraux d'oxyde de fer, et notamment, la magnétite, en aval de l'estuaire (zone sableuse).The study of the estuary of Oum er-Biâa, located on the moroccan atlantic near the Azemmour city, far 60 km in the south of Casablanca, focus on the hydrogeochemical behavior of phosphorus. In the sediment of the estuary of Oum er-Biâa, total phosphorus was mainly in mineral form (76%-95%), with a predominance of the fraction related to calcium (45%-90%), that was in apatitic form and not mobilizable. The ferric fraction P-Fe (2%-38%) contributed mainly to the biodisponibility of phosphorus in this estuary. The temporal and spatial variations of this fraction were controlled on the one hand, by the characteristics of the sediment (particule fraction < 63 µm and organic matter) and, on the other hand, by the salinity. Indeed, the upstream muddy zone rich in organic matter had a high capacity to uptake the phosphorus (P-Fe and ROP) in march and july. In the downstream sandy zone, the magnetite presented a great importance for the adsorption of phosphorus, specially at high salinity during may and october
Le réservoir du barrage Daourat a fait l'objet, au cour du cycle hydrologique 1996-1997, d'une étude pour comprendre le fonctionnement hydrogéochimique du réservoir. Le régime hydrologique du réservoir Daourat (9,5 Mm3) résulte des apports externes et de la gestion propre du réservoir. La colonne d'eau ne présente aucune période de stratification (lac polymictique chaud) ni d'anoxie. L'influence des réservoirs situés en amont (Al Massira 2 800 Mm3 et Imfout 18 Mm3) ne permet pas d'expliquer le fonctionnement biogéochimique du réservoir Daourat. Cette retenue semble être beaucoup plus contrôlée par les apports du bassin versant local et par la charge interne du réservoir.The study of the Daourat reservoir during the hydrological cycle 1996-1997, focus on the water column and the sediment in order to understand the hydrogeochemical functioning. The hydrological mode of the Daourat reservoir (9,5 Mm3) is a result of the external contributions of the area catchment and the management of the reservoir. The water column of this reservoir does not present any period of stratification and any period of anoxia. It is a warm polymictic lake. The influence of the upstream reservoir (Al Massira 2 800 Mm3 and Imfout 18 Mm3) does not explain the physicochemical and geochemical functioning of the Daourat reservoir. Indeed, this reservoir seems to be much more controlled by the contributions of the local area catchment and by the internal load of the reservoir
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