A methodology associated with the simulation of tidal range projects through a coastal hydrodynamic model is discussed regarding its capabilities and limitations. Particular focus is directed towards the formulations imposed for the representation of hydraulic structures and the corresponding model boundary conditions. Details of refinements are presented that would be applicable in representing the flow (and momentum flux) expected through tidal range turbines to inform the regional modelling of tidal lagoons and barrages. A conceptual tidal lagoon along the North Wales coast, a barrage across the Severn Estuary and the Swansea Bay Lagoon proposal are used to demonstrate the effect of the refinements for projects of a different scale. The hydrodynamic model results indicate that boundary refinements, particularly in the form of accurate momentum conservation, have a noticeable influence on near-field conditions and can be critical when assessing the environmental impact arising from the schemes. Finally, it is shown that these models can be used to guide and improve tidal impoundment proposals.

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This study considers environmental impacts and the power production potential of a number of coastally attached tidal lagoons, proposed along the North Wales coast, UK. Initially, the impoundment shape, turbine and sluice gate locations were modified according to the regional bathymetric data. A refined 0-Dimensional approach was implemented to optimise the lagoon operation, based on given turbine and sluice gate specifications. In turn, a two-dimensional numerical model, based on an unstructured triangular mesh, has been refined to simulate the hydrodynamic processes, initially without and subsequently in the presence of the lagoons. The hydrodynamic model adopts a TVD finite volume method to solve the 2D shallow water equations, based on a second-order accurate spatial and temporal numerical scheme. An encouraging performance is apparent in reproducing the established conditions encountered in the region through comparisons against available data. The incorporation of tidal lagoons in the model appears to have a considerable effect on the flow structure in the region, by inducing high velocity accelerations near the sluices and turbines, depending on the stage of the tidal cycle. Considering a two-way generation regime, it is outlined that the loss of intertidal regions can be minimised, which is a major source of concern with regards to the environmental impact of such schemes through an ebb-generation operation. Particular focus is directed towards the comparisons between the 0-D and 2-D modelling results, an aspect which has not been reported previously. Predictions of the models diverge as the scale of the lagoon project increases, but it is highlighted that the 0-D methodology can be utilised for the optimisation of the processes in the initial stages of design before proceeding to more sophisticated numerical model simulations