Date of Award

2024-12-01

Degree Name

Doctor of Philosophy

Department

Environmental Science and Engineering

Advisor(s)

Rosa M. Fitzgerald

Abstract

Surface currents study provides invaluable understanding into the physical dynamics of oceans, bays, estuaries, and nearshore environments, offering critical insights about water movement and related coastal processes. These currents play a fundamental role in understanding the state of estuarine and marine systems, such as their effects on sediment transport, heat distribution and climate change, nutrient distribution, and pollutant dispersal. In addition, surface current data provides significant economic and ecological implications for coastal communities essential for managing resources effectively and ensuring the resilience of coastal regions against environmental and anthropogenic pressures. This study was driven by the need to address the significant data gap in surface current measurements for two critical Texas estuaries, Galveston Bay (GB) and Sabine Lake (SL). Additionally, it sought to evaluate the performance of the robust 3D hydrodynamic model, SCHISM, in estimating surface currents by comparing its predictions against observations from High-Frequency (HF) radar systems. The insights gained from this assessment are intended to support the application of SCHISM in advanced hydrodynamic simulations, including storm surge modeling, sediment transport analysis, and oil spill trajectory predictions. The model was used to make a simulation of a part of the Texas coast encompassing GB and SL using input data covering the month of April 2023 to produce surface current and HF radar data was extracted for the same month from the newly installed two HF radar networks comprising three radars at the bay and two radars at the lake. Robust data analytical techniques were employed to ensure the model outputs were comparable to the radar datasets. The intercomparison process included qualitative evaluations, focusing on the alignment of current vector directions, and quantitative analyses, which assessed current magnitudes and correlations in the eastward (U) and northward (V) current components. An important finding of this study is the relationship between qualitative comparisons and quantitative analysis. Days characterized by predominant northward currents exhibited significant correlation coefficients exclusively in the northward (V) direction for both the bay and the lake. Similarly, on days dominated by eastward currents, significant correlation coefficients were observed exclusively in the eastward (U) direction in the bay and lake. Also, notably, SCHISM and HF radar also effectively captured the trend and magnitude of surface currents on days with both eastward and northward currents in the bay and lake. Overall, SCHISM demonstrated strong performance in accurately simulating surface currents, closely aligning with the established methodology of HF radar. The model achieved high correlations (up to 0.94), a robust index of agreement (up to 0.95), and low error metrics throughout the study period. The model's performance was significantly influenced by physical factors, particularly wind, tidal forces, and freshwater inflows in both the bay and the lake. This finding underscores the critical importance of accounting for environmental variables in surface current predictions when using hydrodynamic models like SCHISM and observational technology such as HF radar, especially in dynamic coastal regions like Galveston Bay and Sabine Lake.

Language

en

Provenance

Recieved from ProQuest

File Size

140 p.

File Format

application/pdf

Rights Holder

Cletus Ozoemena Ogbodo

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