Approved for public release; distribution is unlimited / Naval operations are highly dependent upon environmental conditions that can either adversely affect successful completion or hinder the safety of personnel. Each warfare community has defined environmental thresholds and operating limits that restrict the execution of any intended maneuver. As the warfare environment continues to shift from open ocean to the littoral, environmental prediction and modeling efforts of the shallow water surroundings need to be developed in order to support these operations. A hydrodynamic model, Water Quality Management and Analysis Package (WQMAP), has been developed by Applied Sciences Associates, Inc. that is designed specifically to provide accurate littoral environmental prediction. WQMAP is one of several hydrodynamic models used operationally by the Naval Oceanographic Office (NAVOCEANO) to predict currents and water elevations in littoral regions. Implementations of shallow water hydrodynamic models in foreign waters are usually data-starved for model forcing and validation. In a series of studies, NAVOCEANO intends to model various bays within the continental United States, where sufficient data exists, to study the sensitivity of lack of data on model results. This study will utilize WQMAP to design a hydrodynamic model in San Diego Bay to predict currents in order to investigate the impact of grid resolution on model results, and to provide proper current predictions for Fleet training and operations. / Lieutenant, United States Navy

Accurate prediction of nearshore waves and currents is of critical importance in littoral naval operations. This study examines the effects of complex bathymetry on nearshore currents. Data collected by an array of 12 pressure and velocity sensors in the Nearshore Canyon Experiment (NCEX), conducted near La Jolla, California in 2003, were analyzed to investigate the variability of nearshore currents near a submarine canyon. Time series of pressure, 3-component velocity, and wave heights along the 10 meter depth contour were analyzed to determine the relative importance of tides, waves, and winds in the forcing of nearshore currents outside the surf zone. Additionally, the spatial variability of the observed currents was investigated in relation to the nearby canyon head. Case studies are examined to determine how different wave and tide conditions affect the currents near the canyon. In low-moderate wave conditions, tides dominate longshore currents, whereas cross-shore currents show the passage of irregular bore-like features. The currents are coherent away from the submarine canyon and decay towards the canyon head. Strong longshore currents were observed near the canyon head during a large wave event that were likely driven by an alongshore pressure gradient associated with wave set-up variations.

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Before tidal stream energy is exploited, tidal power resource and environmental assessments must be undertaken. This thesis explores limits to power extraction for tidal sites defined by a strait between an island and landmass. Numerical simulations provided by Fluidity are used to analyse power extraction from locations in the strait and around the island for an idealised island-landmass domain and an actual coastal site. The numerical model is verified by comparing predictions with analytical solutions for inviscid flow past a circular cylinder located in the centre of a channel and in the vicinity of a wall. The model is then validated against laboratory measurements of flow patterns for impulsively-started flow past a submerged circular cylinder, and for flow past a surface-piercing circular cylinder in oscillatory laminar shallow flow. It is demonstrated that the numerical method captures satisfactorily the mechanisms of early wake formation, which indicates the model can be applied to assess tidal stream resource within the coastal geometries considered herein. Finally, the methodology to account for power extraction is satisfactorily verified for bounded and unbounded flows. Contrary to current practices, results from a parameter study for different idealised coastal sites reveal that the maximum power extracted in the strait is not well approximated by either the power extracted naturally at the seabed or the undisturbed kinetic power. Moreover, an analytical channel model underpredicts the maximum power extracted in the strait due to its inability to account for changes in the driving head resulting from power extraction and flow diversion offshore of the island. An exception is found for islands with large aspect ratios, with the larger dimension extending parallel to the landmass; i.e. the island-landmass geometry approaching that of a channel. In this case, the extracted power is satisfactorily approximated by the power naturally dissipated at the seabed and there is good agreement with the analytical model. The maximum power extracted in the strait is shown to decrease when water depths offshore are greater than in the strait, underlining the importance of fully understanding the wider bathymetry of a given site. A similar conclusion is reached when strait blockage is reduced. The power extraction in the strait is found to be sensitive to both viscosity and seabed friction, and these parameters need to be properly estimated during the setup and calibration of models in order to reduce uncertainty. Power extraction increases when turbines are sited simultaneously both in the strait and offshore. Tidal power assessment is performed for Rathlin Sound, off the coast of Northern Ireland. Again, no clear relationship is found between maximum power extracted in the strait and either the power dissipated naturally at the seabed or the undisturbed kinetic power. A similar ratio of power extracted to undisturbed kinetic power is obtained as for the equivalent idealised model. The analytical channel model underpredicts the maximum power extracted. The actual and idealised coastal site models indicate similar responses to changes in seabed friction, and similar reduction in power extraction with decreasing strait blockage.

This thesis presents a technique for storm surge forecasting. Storm surge is the water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level by almost 20 feet. Numerical modeling is an important tool used for storm surge forecast. Numerical model ADCIRC (Advanced Circulation model; Luettich et al, 1992) is used in this thesis for simulating hurricanes. A statistical technique, EST (Empirical Statistical Technique) is used to generate life cycle storm surge values from the simulated hurricanes. These two models have been applied to Freeport, TX. The thesis also compares the results with the model SLOSH (Sea, Lake, and Overland Surges from Hurricanes), which is currently used for evacuation and planning. The present approach of classifying hurricanes according to their maximum sustained winds is analyzed. This approach is not found to applicable in all the cases and more research needs to be done. An alternate approach is suggested for hurricane storm surge estimation.

Dapeng Bay is located in the southwest coast of Taiwan. It is a cystic shaped shallow lagoon, which has only one entry for exchanging lagoon water with the coastal current. The water quality is depending on the refreshing rate and the mixing level in the lagoon. In order to understand the circulation pattern monthly measurements using an ADP are carried out. Three water quality monitoring stations are constructed for regular online observation of the water quality in the lagoon. The flows are on the west-northwest direction during the flood and toward the west during ebb. Strong currents are observed in the tidal inlet channel. The general circulation patterns are mainly dominated by tide though wind effects can observed from the measurements. This study established a three-dimensional hydrodynamic modeling system using the FVCOM model developed at the U.S. Marine Ecosystem Dynamics Modeling Laboratory for the simulation of Dapeng Bay currents. The study includes the comparison of the recent circulation and the flow fields after broaden of the inlet navigation channel. This will change not only the shape but also dredge the channel deeper. These variations may differ the circulation patterns and the exchange quantities as well. The model results are first compared with the observations for the present situation as calibration. The simulation results for the studies of the changing of the inlet channel will be discussed.

The current study has applied the Genetic Algorithm (GA) for the boundary parameters calibration in the hydrodynamic-based tidal model. The objective is to minimize the deviation between the estimated results acquired from the simulation model and the real tidal data along Taiwan coast. The manual trial-error has been widely used in the past, but such approach is inefficient due to the complexity posed by the tremendous amounts of parameters. Fortunately, with the modern computer capability, some automatic searching processes, in particular GA, can be implemented to handle the large data set and reduce the human subjectivity when conducting the calibration. Besides, owing to the efficient evolution procedures, GA can find better solutions in a shorter time compared to the manual approach. Based on the preliminary experiments of the current study, the integration of GA with the hydrodynamic-based tidal model can improve the accuracy of simulation.

The coastal wetlands at Aransas National Wildlife Refuge near Austwell, Texas, support the last migrating population of whooping cranes during the winter months (October through April). With a population currently at 216 individuals, these are the rarest cranes in the world. The wetlands in which they winter are a part of the San Antonio Bay system, a bay that receives constant fresh water flow from the Guadalupe River. Currently there is a plan for using water diverted from the Guadalupe River just before it enters San Antonio Bay as a water supply for the greater San Antonio metropolitan area located 200 km to the northwest. The Guadalupe River delivers nutrients and sediment into the estuary along with fresh water. Because of the importance of sediment within a tidal wetland ecosystem, it is imperative to understand the sediment budget and underlying forces that drive it if one is to ultimately grasp how this ecosystem functions. To document natural and anthropogenic factors exerting control over sediment movement in this system, three sites on tidal creeks near the boundary between marsh and bay were chosen. The Gulf Intracoastal Waterwayparallels the marsh edge. Over six, non-consecutive weeks water level and velocity were automatically monitored in the tidal creeks. Automated water samplers extracted water samples that were analyzed for suspended sediment. In addition, bedload traps were deployed in one creek to monitor sediment movement along the channel bottom. Inflow exceeded outflow during the study. As a result there was a net influx of suspended sediments into the marsh. Bedload material also moves with current direction, and it appears to move in response to barge induced outflow currents. Barges passing on the Gulf Intracoastal Waterway exert influence on water level, flow direction, and velocity within tidal creeks. Natural factors such as winds, tides, and freshwater input from upland runoff or river discharge also impact suspended and bedload sediments.

This thesis presents a technique for storm surge forecasting. Storm surge is the water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level by almost 20 feet. Numerical modeling is an important tool used for storm surge forecast. Numerical model ADCIRC (Advanced Circulation model; Luettich et al, 1992) is used in this thesis for simulating hurricanes. A statistical technique, EST (Empirical Statistical Technique) is used to generate life cycle storm surge values from the simulated hurricanes. These two models have been applied to Freeport, TX. The thesis also compares the results with the model SLOSH (Sea, Lake, and Overland Surges from Hurricanes), which is currently used for evacuation and planning. The present approach of classifying hurricanes according to their maximum sustained winds is analyzed. This approach is not found to applicable in all the cases and more research needs to be done. An alternate approach is suggested for hurricane storm surge estimation.

This study maps the facies architecture and geometry of stratigraphic surfaces within the tide-influenced upper Sego Sandstone exposed in the Book Cliffs between Crescent Junction and Thompson Springs, Utah. A bedding diagram was constructed by correlating 32 measured stratigraphic logs across this 8.5 kilometer strike-oblique outcrop to interpret depositional environments and the sequence stratigraphic setting of this tidally-influenced sandstone. Five facies associations are defined: marine shale, lower shoreface, tidally-influenced bedsets, heterolithic tidal bedsets, and tidal flat deposits. Vertical facies trends define two sandy intervals separated by a marine shale, that are interpreted to record episodic progradation of deltaic shorelines. Erosion surfaces at the base of these intervals are interrupted to record tidal scouring of the sea floor during falling stage regression. Sandstone-bodies within these intervals shingle westward recording delta lobes that thinned and became more heterolithic. Although sandstone intervals are interpreted to record progradation, internal cross stratification is dominantly tidal-flood oriented. This is interpreted to record preferential preservation of bedload transported by flood tidal currents onshore, even though net sediment was directed offshore in a suspended ebb-oriented hypopycnal plume and as fluid mud during uncommon river floods. Deposits above high-relief erosion surfaces observed to cut down into the upper Sego Sandstone do not meet the criteria for incised valley fills. These surfaces are interpreted to record tidal current enlargement of distributary channels after abandonment. Such incisions thus do not necessarily record changes in sea level.