The energy of the tides represents one globally existent source of renewable energy, and has the potential to play a major role in a sustainable future. An assessment of the potential for tidal energy extraction using marine current turbines at a particular location in the Beaufort River near Parris Island, South Carolina is presented. The Marine Corps Recruit Depot located on Parris Island is situated between the confluence of the Broad and Beaufort Rivers. These rivers are tidally dominated, and experience some of the largest tidal ranges in the southeastern United States, between 2.5 and 3 meters during spring tide periods. Because Parris Island already has much of the necessary land-based infrastructure in place, there is logical potential for the extraction of kinetic energy from the nearby tidal streams using underwater turbines for power production. In order to evaluate the potential of a particular location to produce significant amounts of energy using these types of devices, extensive investigations must be conducted to determine important site characteristics such as water depth, current velocity, and water level fluctuations over time. This potential was investigated using in-situ measurements in the vicinity of the pump station on Parris Island, and by developing a numerical model of the region using the Regional Ocean Modeling System (ROMS). This model was calibrated using the results from the in-situ measurements, and was then used to determine the impacts of tidal energy extraction on the local flow field. Results from in-situ measurements indicate that tidal currents along the portion of the Beaufort River analyzed in this study are driven primarily by the semi-diurnal M2 tidal constituent. The tidal range at the study site is approximately 2 meters on average, with a mean depth-averaged current velocity magnitude of 0.57 m/s predicted for a period of one year. A mean depth-averaged current velocity magnitude of 0.59 m/s was observed over the course of the longer-term ADCP deployment from November 12 to December 17, 2009. The maximum current speed at the site is approximately 1.2 m/s at the water surface. The ROMS model applied to the coastal areas surrounding Parris Island, SC produces results that closely resemble in-situ measurements collected previously during both the boat-based survey and the longer-term ADCP deployment. In the analysis of the effects of energy extraction from the system, four separate cases were considered in which 10, 20, 30, and 60% of the total kinetic energy contained in the flow was dissipated near the location of the longer-term ADCP deployment. Minimal impacts on the local hydrodynamics were observed across the four cases considered.

Tide-influenced point bars represent a significant proportion of shallow-marine deposits, commonly developed along meandering channels in most backbarrier and estuarine systems. However, sedimentological studies to characterize this type of deposit are still emerging. They often present very heterogeneous internal architectures which development is controlled by the complex flow patterns operating in tidal environments. The study of the sedimentological and morphological characteristics of these features provides better understanding of the hydrodynamic processes that shape coastal systems and control their evolution as well as it contributes to better reservoir potential prediction and production strategy optimization, as tidal point bars may represent hydrocarbon reservoirs in subsurface and their heterogeneous characteristics directly impact reservoir quality. In this study, we investigated six modern tidal point bars located along distinct estuarine tidal channels in Georgia. Using core data, 2D shallow seismic data and current measurements and flow velocity profiles, we discussed the main hydrodynamic controls on sediment transport and distribution, and determined how they affect the morphology, the internal architecture and the sediment distribution within these bars. We confirmed that the influence of fluvial input in tidal channels plays an important role on the development of the morphology and the heterogeneous architecture of point bars as it adds more complexity to the system hydrodynamics, promoting more asymmetric variations in water level fluctuations and huge variations of current velocities. We proved that point bars developed in distinct tide-influenced channels and estuaries, although present very different sedimentary facies distribution, may have sedimentary facies in common, which organization is analogous to surface processes operating at each environment. We demonstrated that differences in tidal asymmetries between the ebb and flood channels produce sedimentological differences between the different parts of the bar. This study showed that tidal point bars present distinct heterogeneous sediment distributions, morphologies and internal architectures that do not conform to the existing theoretical models of fluvial point bars and highlighted that, despite the differences in local hydrodynamic conditions, similarities identified between the different bars permitted us to distinguish the sedimentological responses to regional allogenic events, which can be mistakenly interpreted as sedimentological responses to local autogenic events.

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The generation of electricity from tidal currents is an emerging industry with the potential to contribute to the UK energy supply in a predictable and sustainable way. The development of the technology requires the cost effective subsea installation of energy conversion systems in an energetic and challenging marine environment. One concept developed for the fastening of tidal energy converters to the seabed is the Active Gravity Base (AGB), which offers potential reductions in installation cost and time, relative to existing fastening methods. The performance of this concept in response to unsteady flow conditions is explored within this thesis. The dynamic behaviour of a tidal current is driven by a range of factors from gravitational forces of celestial bodies to high-frequency fluctuations of turbulent eddies. The response of the AGB concept to the unsteadiness of tidal currents is herein considered under the two broad time-scales; the directionality of the mean semi-diurnal cycle and the high frequency variations from a given mean flow velocity. The correlation between the direction and velocity of the tidal flow was assessed using hourly averaged data provided by the Admiralty Charts in the northern UK waters. The resulting directionality model was used to predict the performance of the AGB under a range of quasi-steady flow conditions. High frequency velocity measurements of a potential tidal energy site were obtained through collaboration with the University of Washington and the Pacific Northwest National Laboratory. This data was used to estimate the maximum perturbation from the mean velocity that can be expected on an annual basis. An experimental facility was developed within the re-circulating water flume at the University of Edinburgh to examine the dynamic loads generated by controllable two-dimensional flow perturbations. This was successfully achieved using a configuration of twin pitching foils with independent motion control. A relationship between the foil pitch angle and velocity perturbation time series was predicted using a vortex model of the foil wakes. This configuration was shown to be able to generate significant flow fluctuations within the range of reduced frequencies 0:06 ≤ k ≤ 1:9, with a peak gust intensity of Ig = 0:5. The numerical solution was validated against experimental results.