[ Modélisation hydrodynamique DELFT3D des courants de marée de la plage sous-marine du littoral sud-ouest de la Côte d’Ivoire ]
N’Guessan Eric Yao1, Konan Roger Assie2, and Josias Boanerges Nongbe3
1 UFR Environnement, Université Jean Lorougnon GUEDE, BP 150 Daloa, Côte d’Ivoire
2 UFR Environnement, Université Jean Lorougnon GUEDE, BP 150 Daloa, Côte d’Ivoire
3 UFR-STRM, Université Felix Houphouët-Boigny, Cocody-Abidjan, 22 BP 582 Abidjan 22, Côte d’Ivoire
Original language: French
Copyright © 2024 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The fundamental tool of this study is the two and three-dimensional modeling software DELFT 3D. It was used to model the hydrodynamic processes of the harbor of San-Pédro (Côte d’Ivoire) and its immediate marine environment, with the input parameters such as tidal variations in tides and river flows, as well as average annual wind speeds. Studies focused on the behavior of current fields, water level variation, and the nature of the tidal wave. The calibration of the model followed by an analysis of the literature led us to choose a coefficient of 0.03 m-1/3.s, with which the model performs very well. Current fields tend to follow the wind direction, parallel to the coast at sea, while they fit the morphology of the roadstead. At sea, currents are exclusively linear at low water, and exceptionally gyratory at flood stage in front of the San-Pedro river outlet. In the roadstead, they are gyratory and linear, alternating in some places and permanently gyratory in others. The shape of the current also depends on its speed, with a limit of 1.5 cm/s for the appearance of gyratory currents at lower speeds. The current speeds in the roadstead are between 0 and 6 cm/s while at sea they are between 5 and 11 cm/s, exceptionally between 10 and 34 cm/s in front of the outlet. As water level variations are highly dependent on tide and season, they are greater in the roadstead (4cm on average) than at sea. The wave is stationary in roadstead, with the existence of the seiche phenomenon, and progressively dominant at sea. The seiche wave determines the directions of entry and exit of water from the roadstead, with low tide corresponding to an outflow of water and high tide, a period of transition between the ingress and egress of water from the roadstead.
Author Keywords: DELFT 3D, Foreshore, Submersion rate, Coastline, San-Pedro.
N’Guessan Eric Yao1, Konan Roger Assie2, and Josias Boanerges Nongbe3
1 UFR Environnement, Université Jean Lorougnon GUEDE, BP 150 Daloa, Côte d’Ivoire
2 UFR Environnement, Université Jean Lorougnon GUEDE, BP 150 Daloa, Côte d’Ivoire
3 UFR-STRM, Université Felix Houphouët-Boigny, Cocody-Abidjan, 22 BP 582 Abidjan 22, Côte d’Ivoire
Original language: French
Copyright © 2024 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The fundamental tool of this study is the two and three-dimensional modeling software DELFT 3D. It was used to model the hydrodynamic processes of the harbor of San-Pédro (Côte d’Ivoire) and its immediate marine environment, with the input parameters such as tidal variations in tides and river flows, as well as average annual wind speeds. Studies focused on the behavior of current fields, water level variation, and the nature of the tidal wave. The calibration of the model followed by an analysis of the literature led us to choose a coefficient of 0.03 m-1/3.s, with which the model performs very well. Current fields tend to follow the wind direction, parallel to the coast at sea, while they fit the morphology of the roadstead. At sea, currents are exclusively linear at low water, and exceptionally gyratory at flood stage in front of the San-Pedro river outlet. In the roadstead, they are gyratory and linear, alternating in some places and permanently gyratory in others. The shape of the current also depends on its speed, with a limit of 1.5 cm/s for the appearance of gyratory currents at lower speeds. The current speeds in the roadstead are between 0 and 6 cm/s while at sea they are between 5 and 11 cm/s, exceptionally between 10 and 34 cm/s in front of the outlet. As water level variations are highly dependent on tide and season, they are greater in the roadstead (4cm on average) than at sea. The wave is stationary in roadstead, with the existence of the seiche phenomenon, and progressively dominant at sea. The seiche wave determines the directions of entry and exit of water from the roadstead, with low tide corresponding to an outflow of water and high tide, a period of transition between the ingress and egress of water from the roadstead.
Author Keywords: DELFT 3D, Foreshore, Submersion rate, Coastline, San-Pedro.
Abstract: (french)
L’outil fondamental de cette étude est le logiciel de modélisation numérique à deux et trois dimensions DELFT 3D. Il a été utilisé pour modéliser les processus hydrodynamiques du port de San-Pédro (Côte d’Ivoire) et de son environnement marin immédiat, avec comme paramètre d’entrée : les variations de la marée et des débits fluviaux ainsi que la moyenne annuelle du vent. Les études se sont portées sur le comportement des champs de courant, la variation du niveau d’eau, et la nature de l’onde de marrée. Le calage du modèle suivi d’une analyse de la littérature nous a amené à choisir un coefficient de 0,03 m-1/3.s, avec lequel le modèle est très bon. Les champs de courant ont tendance à suivre la direction du vent, parallèle à la côte en mer, tandis qu’ils épousent la morphologie de la rade. En mer les courants sont exclusivement linéaires en étiage et exceptionnellement giratoire en crue en face de l’exutoire du fleuve San-Pedro. En rade, ils sont giratoires et linéaires, alternativement pour certains endroits et giratoires permanemment pour d’autres. La forme du courant dépend aussi de sa vitesse, avec une limite de 1,5 cm/s d’apparition des courants giratoires en baissant les vitesses. Les vitesses en rade sont entre 0 et 6 cm/s alors qu’en mer ils sont entre 5 et 11 cm/s, exceptionnellement entre 10 et 34 cm/s en face de l’exutoire. Les variations de niveau d’eau dépendant fortement de la marée et de la saison, elles sont plus importantes en rade qu’en mer. L’onde est stationnaire en rade, avec l’existence du phénomène de seiche, et à dominance progressive en mer. L’onde de seiche détermine les directions d’entrée et de sortie d’eau de la rade avec la basse mer qui correspond à une sortie d’eau et la pleine mer, une période de transition entre l’entré et la sortie d’eau de la rade.
Author Keywords: DELFT 3D, Estran, Taux de submersion, Littoral, San-Pédro.
