Numerical simulation of tidal circulation in the Obhur Lagoon, on the eastern coast of the Red Sea, Saudi Arabia

• Published in: Arabian journal of geosciences 2022, Vol.15 (8), Article 719
• Main Author: Madah, Fawaz
• Format: Article
• Language: English
• Subjects: Coefficients; Correlation coefficient; Correlation coefficients; Diurnal variations; Earth and Environmental Science; Earth science; Earth Sciences; Finite element method; Inlets (waterways); Lagoons; Mathematical models; Modelling; Neap tides; Nesting; Numerical models; Original Paper; Parameters; Physical properties; Simulation; Tidal constituents; Tidal models; Tidal range; Two dimensional models; Water levels
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-022-09945-z

A two-dimensional depth-averaged numerical model was developed, with the aim of describing the tidal circulation patterns in the Obhur Lagoon. The lagoon is located in the central Red Sea, on the eastern coastline, about 30 km north of Jeddah City, Saudi Arabia. The Delft3D modelling system was employed to achieve the aim of the study, using a curvilinear mesh with a high resolution of 10–30 m inside the lagoon region. The 2D numerical model was forced by the major semidiurnal ( M 2 , S 2 , N 2 , K 2 ) and diurnal ( K 1 , O 1 , P 1 , Q 1 ) tidal constituents, obtained from a regional tidal model by applying a nesting approach. The influence of different numerical and physical parameters on the model results was investigated to find the optimal settings. The performance of the tidal model was evaluated by comparing the simulated water levels with the available water level observations. The IOA parameter and Taylor diagram were considered to assess the model performance statistically. It was found that the numerical model is able to reproduce the tidal levels in the study area to a good degree. The numerical model simulates the tidal conditions in the lagoon region with correlation coefficients of 0.81 and 0.79. The RMSD was found to be ranged between 0.038 and 0.041 m. The IOA parameter confirms the model ability in reproducing the tidal elevations with value > 0.95. The tidal range is relatively small and is dominated by the principal lunar ( M 2 ) component, with an amplitude of 0.072 m. The relation F  =  (O 1  +  K 1 ) / ( M 2  + S 2 ) indicates a mixed, predominantly semidiurnal regime ( F  = 0.52). The simulation results suggest that the inlet of the lagoon including the southern part is tidally dominated. The model results suggest that the ebb neap tide is characterized by slightly higher velocities in comparison with the flood neap tide. This study constitutes a first step towards understanding and modelling the tidal circulation in the Obhur Lagoon.