Degree

Doctor of Philosophy (PhD)

Department

The Department of Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

River-dominated deltas evolve through a complex interplay of river discharge, tide, atmospheric forcing, and geomorphic feedback, yet the processes governing short-term hydrodynamic variability and long-term connectivity remain insufficiently quantified. This dissertation advances understanding of these mechanisms through an integrated examination of 1) cold-front-driven hydrodynamics, 2) channel–floodplain water exchange, and 3) nonlinear interactions among forcing factors within the Wax Lake Delta (WLD), a naturally developing delta in coastal Louisiana. Although this work does not explicitly examine sediment transport or nutrient dynamics, the hydrodynamic processes investigated fundamentally regulate and drive sediment redistribution and biogeochemical functioning within deltaic environments. The results show that cold fronts are major drivers of short-term hydrodynamics in the WLD. Their passage reorganizes water levels, currents, and water transport pathways, strongly influencing wetland flooding and the shifting pathways of material exchange between channels and floodplains. Findings also reveal that channel–floodplain connectivity is highly dynamic and strongly modulated by wind direction, discharge magnitude, and local morphology. Floodplains exhibit distinct exchange behaviors across the landscape, and the balance between channelized and overbank transport shifts markedly under different forcing conditions. Connectivity therefore emerges as an adaptive property of the delta rather than a fixed spatial pattern. A key contribution of this work is the quantification of nonlinear hydrodynamic interactions among tides, river flow, and wind forcing. Using newly developed indices, the study demonstrates that nonlinear processes can substantially amplify or suppress water-level fluctuations, tidal range, and flow velocity in ways that cannot be predicted from individual forcings alone. These nonlinear effects are most pronounced in shallow regions, where they strongly influence sediment delivery, delta progradation, and wetland resilience. Collectively, these findings provide a unified framework for understanding how episodic atmospheric events, fluvial inputs, and nonlinear processes interact to shape the behavior and stability of river-dominated deltas. The results offer actionable insights for coastal restoration, sediment-diversion design, and long-term management of vulnerable deltaic landscapes under changing environmental conditions.

Date

12-16-2025

Committee Chair

Li, Chunyan

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Available for download on Friday, December 15, 2028

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