Graduation Semester and Year
Fall 2025
Language
English
Document Type
Thesis
Degree Name
Master of Science in Civil Engineering
Department
Civil Engineering
First Advisor
Yu Zhang
Abstract
Hurricane Beryl generated a complex hydrodynamic response along the Texas coast and Lower Brazos River, producing storm surge, elevated coastal water levels, intense rainfall, and widespread inundation. Low-gradient coastal rivers such as the lower portion of the Brazos River are particularly sensitive to the interaction of these drivers, yet the inland decay of surge energy and its interplay with watershed runoff remain poorly quantified. This study aims to characterize the physical mechanisms controlling water-level amplification, flow reversal, surge attenuation, and inundation development during Hurricane Beryl along the Lower Brazos and to determine the relative contributions of surge and rainfall to the intensity and timing of the resulting flood. A two-way nested Delft3D FM modeling system was developed, comprising a Gulf of America parent model and a higher-resolution regional model covering the Lower Brazos River. The Gulf model reproduced coastal water levels with good skill at Freeport Harbor (RMSE = 0.16 m; NSE = 0.55), and boundary conditions derived from it enabled the regional model to achieve similar performance at Freeport (RMSE = 0.15 m; NSE = 0.61). Inland evaluation at West Columbia yielded high agreement in temporal variability (NSE = 0.92) but larger magnitude errors, reflecting the sensitivity of inland hydraulics to channel geometry, floodplain roughness, and storage processes. Together, the nested models provided a dynamic framework for examining surge propagation and interactions with local runoff and downstream propagating flood wave. Results show a clear sequence of surge-governed processes: a shift from tidal to surge-dominated water levels at the mouth, reversed flow development and stagnation zone formation, and inland propagation of reverse flow. Fourier decomposition isolates the low-frequency surge signal and reveals its attenuation upstream of XS_68. Rainfall-runoff analysis indicates that runoff from the 128 km² watershed between Rosharon and West Columbia reached approximately 3.4 hours after peak rainfall, coinciding with surge-induced hydraulic blockage and amplifying upstream water-level rise. Simulated inundation patterns demonstrate extensive activation of floodplain storage and two-dimensional flow connectivity once channel capacity was exceeded. Overall, the findings show that flooding during Hurricane Beryl resulted from the compound interaction of storm surge and rainfall, governed by backwater dynamics, floodplain connectivity, and the inland decay of surge energy.
Keywords
Hydrodynamic Modeling, Surge, Stagnation zone, Flow Reversal, Downstream Hydraulic Control Lower Brazos River, Delft3D-FM
Disciplines
Civil Engineering | Hydraulic Engineering
License
This work is licensed under a Creative Commons Attribution 3.0 License.
Recommended Citation
Khan, Sabiha Tasnuva, "Coastal Flooding along the Lower Brazos during the Landfall of Hurricane Beryl -A Model-Based Investigation" (2025). Civil Engineering Theses. 468.
https://mavmatrix.uta.edu/civilengineering_theses/468