Influence of Floating Structures on Tide- and Wind-Driven Hydrodynamics of a Highly Populated Marina

Abstract

Harbor siltation is a problem that will exist as long as harbors exist and it is intrinsically linked to their primary functionproviding shelter for anchorage and operative conditions for loading/unloading ships. In these semi-enclosed basins, flow characteristics are one of the main factors influencing siltation and water quality. One of the largest recreational ports of Europe, La Rochelle Marina (southwestern France), is not spared by siltation, which requires serious dredging operations during a major part of the year. In this context, a three dimensional model (TELEMAC 3D) has been used to investigate its hydrodynamics. Using a simplified approach, floating structures were implemented in the model. Comparison with observations has demonstrated the need to consider these structures in our study. They significantly reduce velocity in the inner parts of the marina and concentrate current on access channels. Numerical results also highlight the joint role of the macrotidal regime and wind stress in the movement of water masses and their residual circulation.

Characterisation of the Water Renewal in a Macro-Tidal Marina Using Several Transport Timescales

“…The semi-implicit Galerkin finite element method is used to solve continuity and momentum equations and a Lagrangian-Eulerian treatment of advective terms and a semi-implicit way ensure numerical stability. More insight and details about the equations are presented in [19]. TELEMAC-3D provides the possibility of taking into account passive tracers in the model domain.…”

“…The modelled area is 35 km wide and 100 km long and is discretised on a 41,000 nodes unstructured grid, with resolution from 2 km offshore to nearly 5 m in the marina [19]. The size of the computational domain (4757.9 km 2 ) is considered sufficiently large so that the prescribed boundary conditions negligibly affect the tracer mass in the marina (0.5 km 2 ) as requested by [27].…”

“…Floating docks and moorings that occupy more than a third of the marina surface were implemented in the model by adding head losses at the surface. Their implementation and their effect on circulation are presented in [19] as well as validation results in terms of currents and water levels.…”

“…In a previous study [19], the validation of the model was done in term of water levels and currents intensity, at numerous locations, inside and outside the marina. Here, the simulated velocities and trajectories of particles are compared with the observational data collected by the drifting buoys.…”

“…To describe water renewal mechanisms accurately, we performed a large number of simulations with a 3D hydrodynamic model calibrated and validated in a previous study [19]. The specificity of the model is to take into consideration the considerable number of structures floating in the marina (e.g., docks, boats).…”