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Tidal barrages could contribute to mitigating climate change, but their deployment is not without potential welfare costs attributable to the degradation of ecosystem services. Economic valuation of natural resources provides a common metric for quantifying the disparate costs and benefits of barrage construction in a way that provides transparency when trade-offs are considered. However, very little is currently known about the value of environmental impacts associated with tidal barrages. Using the Taw Torridge estuary in North Devon as a case study, this research proposes an Environmental Benefits Assessment methodology that supports application of the ecosystem services concept to local environmental impact appraisal, and facilitates economic valuation. This methodology is novel in that it evaluates benefits, as opposed to services, and considers a comprehensive suite of benefits in a single assessment: an approach rarely attempted in practice, but essential if ecosystem services approaches are to fully support resource management needs. The subsequent empirical valuation uses stated preference techniques to examine the different ways people use and value the estuary ecosystem, determine how strongly they rank different costs and benefits of tidal barrages, and elicit willingness to pay (WTP) to reduce the habitat loss resulting from a tidal barrage development. The study provides the first empirical valuation of UK estuarine mudflats, but makes a further contribution to the environmental economics discipline by deploying both contingent valuation and choice experiment methods. Additionally, a novel application of the Analytic Hierarchy Process (AHP) is used to examine the consistency of WTP with expressed preferences for habitat protection in relation to other barrage attributes. The alternative stated preference techniques result in comparable WTP values and the importance attached to habitat loss (as measured by the AHP) is strongly associated with WTP and also with its scope sensitivity, indicating that WTP is largely driven by environmental preferences.

Computer technology is growing fast in recent years. Modeling technique is used in predicting or in planning engineering works and even in preventing disaster. Modeling is widely used in many domains and unmanned Real-time online operation modeling systems on prediction become popular. Model may become inaccurate due to a number of uncertainties in the approximation and by numerical reasons. Data Assimilation technique is developed to solve this problem. Measured data is used to improve the model results. In this research, the Cressman scheme was chosen as the data assimilation scheme and used for correcting the modeling system. An idealized model was constructed first as Taiwan Strait. In order to test the stability if data assimilation system several geographical variations and data availability cases were designed, eg adding varying bottom topography, an island added in the domain, different measurement data locations. In order to test the model sensibilities an error was inserted to the boundaries. Model results were first corrected with data assimilation system for a period of time, a Harmonic Analysis was, then, used for reanalysis the corrected time series on the boundaries. The new boundary condition is used in the new model run for making predictions. A true topography and island system as Taiwan Strait was tested with the true astronomical tide as the boundary input. The data assimilation system using the Cressman scheme could reduce the RMSE effectively. The factor that affects the efficiency of the data assimilation system is the number and the location of the measurement data.

The Esdolomada Sandstone member 2 crops out in the Tremp-Graus Basin of north-central Spain and forms the uppermost part of the Eocene Roda Formation. The second Sandstone unit within the Esdolomada member (ESD2) consists of bioturbated and shell-rich, very-fine sandstones as well as stacked sets of fine- to coarse-grained cross-stratified sandstones. The overall upward trend in the member is commonly upward thickening and coarsening of beds into and through the cross-stratified interval, though at some few locations there is no obvious trend or even upward thinning of beds. The internal architecture of the member is one in which groups of beds lie between master surfaces that dip highly obliquely to the migration direction of the individual cross strata. The ESD2 is interpreted to be a shelf tidal sand bar within the overall transgressive Esdolomada Sandstone member. It is likely that these bars migrated in a coast parallel fashion, as suggested by the cross-bed orientations, but also accreted laterally away from the coast along the seaward-dipping master surfaces. LIDAR (light detection and ranging) data collection for the Esdolomada member was attempted along the Isábena River near the village of Roda de Isábena, with a total lateral coverage of approximately 3 kilometers. Detailed outcrop measurements were made in accessible areas along the same transect. Outcrop analogs are the best source of data to understand reservoir heterogeneities and to build reservoir analogs for fluid flow simulations. Sand-rich, offshore tidal sandbodies are usually surrounded by marine mudstones, and are recognized from their very orderly stacking of cross-stratified sets (more orderly than in fluvial settings) , their complex internal architecture of master surfaces dipping obliquely to the direction of migration of the contained cross strata and their significant sandstone/mudstone heterogeneities. Tidal bar systems such as the ESD2 are appealing hydrocarbon prospects for several reasons. Primarily, they are relatively coarse grained, have a high degree of lateral continuity, and are relatively clean sands. In places where sand beds are stacked, they create enough thickness to offer good vertical permeability; however, mud-draped cross-beds can create heterogeneities in this type of system that buffer fluid flow. Due to a fairly unsuccessful attempt to obtain LIDAR coverage of the ESD2, in order to build an analog reservoir model, surfaces were instead based on measured sections and outcrop photomosaics. Using Schlumberger’s Petrel software, facies logs were created from measured section data, and then interpolated to make a facies and porosity model. / text

Submerged sediment-laden ice blocks that form on the intertidal mud flats of the Minas Basin pose a potential threat to tidal turbines planned for deployment in the Minas Passage. Laboratory prepared ice blocks of varying sediment content, salinity, and length scale were melted in seawater of different temperatures. The effect of sediment inclusions on melt rate is related to changes in heat supply and the heat required to melt a unit mass of ice, where the former is affected by the strength of the convective current and the latter by the ice block properties. A melt rate model for submerged sediment-laden ice is developed, with free convection the dominant deterioration mechanism. The model provides probable upper limits to the lifetimes of submerged ice blocks in the field, and has been used to predict lifetimes of large submerged ice blocks using temperatures representative of seawater in the Minas Basin.

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This thesis examines methods for designing and analyzing kinetic turbines based on blade element momentum (BEM) theory and computational fluid dynamics (CFD). The underlying goal of the work was to assess the potential augmentation of power production associated with enclosing the turbine in an expanding duct. Thus, a comparison of the potential performance of ducted and non-ducted turbines was carried out. This required de ning optimal turbine performance for both concepts. BEM is the typical tool used for turbine optimization and is very well established in the context of wind turbine design. BEM was suitable for conventional turbines, but could not account for the influence of ducts, and no established methodology for designing ducted turbines could be found in the literature. Thus, methods were established to design and analyze ducted turbines based on an extended version of BEM (with CFD-derived coe cients), and based on CFD simulation. Additional complications arise in designing tidal turbines because traditional techniques for kinetic turbine design have been established for wind turbines, which are similar in their principle of operation but are driven by flows with inherently different boundary conditions than tidal currents. The major difference is that tidal flows are bounded by the ocean floor, the water surface and channel walls. Thus, analytical and CFD-based methods were established to account for the effects of these boundaries (called blockage effects) on the optimal design and performance of turbines. Additionally, tidal flows are driven by changes in the water surface height in the ocean and their velocity is limited by viscous effects. Turbines introduced into a tidal flow increase the total drag in the system and reduce the total flow in a region (e.g. a tidal channel). An analytical method to account for this was taken from the eld of tidal resource assessment, and along with the methods to account for ducts and blockage effects, was incorporated into a rotor optimization framework. It was found that the non-ducted turbine can produce more power per installed device frontal area and can be operated to induce a lesser reduction to the flow through a given tidal channel for a given level of power production. It was also found that by optimizing turbines for array con gurations that occupy a large portion of the cross sectional area of a given tidal channel (i.e. tidal fences), the per-device power can be improved signi cantly compared to a sparse-array scenario. For turbines occupying 50% of a channel cross section, the predicted power improves is by a factor of three. Thus, it has been recommended that future work focus on analyzing such a strategy in more detail. / Graduate

The steep continental slopes of the southern Celtic shelf have long been thought to be a major export region for the flux of sediment from the south west approaches to the deep ocean (47-49°). Recent studies have suggested that the transfer of energy from the large barotropic tidal currents to internal tides, and higher frequency internal waves is locally enhanced, and provides a mechanism for the re-suspension and downslope transport of bed material on the upper slope region. This material is thought to be preferentially transported at the head of the many submarine canyons that exist along these ocean margins, where the barotropic tidal currents are locally amplified and internal wave energy focused. A unique 23 day deployment of the benthic lander STABLE (Sediment Transport and Boundary Layer Equipment) in July 1990, was at a depth of 388m on La Chapelle Bank continental slope. The site was at the head of a canyon, and at a depth thought to be critical for the generation of internal tidal energy. It was also at the deep water end of a transect of two current meter moorings across the slope. These measurements have shown that during summer stratified conditions the barotropic and baroclinic tides are sufficiently energetic near to the bed to mobilise the sand/gravel sized sediment on the upper slopes and at the shelf break. Eulerian residual bottom currents and maximum tidal currents are orientated cross-slope and this has important implications for sediment transport. The shelf break is predicted to be a region of bed load parting with bedload transport shelfwards at the shelf break and downslope immediately oceanward. On the critical slope region peaks in suspended sediment concentration occur at times of locally enhanced maximum down-slope flow (40cmsˉ¹) and maximum current shear. This suggests that sediment is being eroded from the bed locally and confirms a net flux of material downslope. Above the boundary layer suspended particulate matter will be transported with the net flow of water which is predominantly along-shelf and polewards. A second 10.4 day deployment of STABLE (II) in January 1994 was at a depth of 879m on the Goban Spur. These observations demonstrated the variability of continental slope processes on the margins of the Celtic shelf. During the deployment, weaker tidal currents (maximum of 24cmsˉ¹) were orientated along-slope and there was no evidence to suggest that the fine cohesive sand/mud sized sediment was mobile. Current meter measurements show that any suspended material will be predominantly transported along-slope and poleward. This will be periodically reversed and the net flux will be equatorward. The two studies have highlighted the temporal and alongslope variability of geological and hydrodynamical conditions near to the bed and highlight the difficulties in estimating shelf-ocean fluxes of material across the whole of the north-west European continental margin.

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