Modelling tidal flow for assessment of hydro-kinetic energy and bathing water quality in coastal waters

In this study, a hydro-environmental numerical model is utilised to further demonstrate the applicability of computer models to predict tidal flow in coastal waters. In particular, high resolution model simulations are performed at two selected sites: the Ogeechee Estuary, USA to assess the hydro-kinetic energy potential near Rose Dhu Island, a small island in the estuary; and at Swansea Bay, UK to assess faecal coliform pollution levels in the bay. Model results from the Ogeechee Estuary simulations revealed that better representation of branching smaller creeks located inshore enhanced the magnitude of tidal currents by approximately 30% near Rose Dhu Island. Evaluation of spatial and temporal distribution of currents revealed that local hot-spots of hydro-kinetic energy exist within the estuary and a maximum annual power of 4.75MW is available from the tidal streams surrounding the island. Investigation of the sensitivity of model parameters related to intertidal storage and bottom friction showed that ebb tide dominance in the estuary is reduced by lowering wetland elevation and by increasing bottom friction in the channel. Increasing the marsh friction to represent the resistance offered by marsh vegetation decreased the influence of intertidal storage on tidal distortion as ebb-dominance is reduced. Model results from the Swansea Bay simulations showed that three distinct flow patterns exist in the bay including re-circulating eddy like patterns, due to the presence of a headland located towards to the south-west end of the bay. The model-predicted distribution of Faecal Indicator Organisms (FIO) helped identify major pollution sources that negatively influence the rating of the Swansea Bay bathing water site. Investigation of the spatial distribution of FIO concentrations at the Designated Sampling Point (DSP) revealed that that the samples collected at DSP for compliance monitoring would correctly represent the pollution levels in the surrounding areas, however, at locations further off-shore significant spatial variability by up to five times was observed. As expected, intermittent peaks in FIO concentrations were noticeable following rainfall events, however, a strong temporal variability within a day was also observed at the DSP with concentration values varying by up to ten times in magnitude