Degree
Doctor of Philosophy (PhD)
Department
Oceanography and Coastal Sciences
Document Type
Dissertation
Abstract
River deltas are among the Earth's most dynamic ecosystems, supporting over 500 million people globally while providing essential ecosystem services; yet they face unprecedented challenges from climate change, sea-level rise, and anthropogenic modifications. Vegetation acts as an ecosystem engineer, actively modifying hydrodynamic processes and morphological evolution. However, quantitative relationships between seasonal vegetation dynamics, water transport timescales, and system-scale hydrological connectivity remain poorly understood. This dissertation quantifies the influence of vegetation on water movement and age across seasonal to decadal timescales in river deltas. This research integrates high-resolution hydromorphodynamic modeling with dynamic vegetation simulation to investigate vegetation-hydrodynamic interactions from local to system-wide scales in river deltas. We find that vegetation creates multi-scale effects on transport processes, significantly influencing local-scale water age distributions within deltaic floodplains, while having limited effects on the network scale. Vegetation presence controls volumetric flow toward deltaic floodplains, with the spatial distribution of vegetation having a larger impact than stem density. Coupled ecomorphodynamic modeling reveals that seasonal vegetation dynamics facilitate the formation of larger islands while stabilizing channels and improving network geometric efficiency. Simulations that include biogeomorphic feedback result in more elongated morphologies, whereas non-vegetated deltas expand laterally. Seasonal vegetation dynamics emerge as a key influence on channel network formation and dynamics. Water age distributions are spatially partitioned: channels display unimodal distributions that are strongly correlated with sedimentation, while islands exhibit multimodal patterns with weakened sediment-age correlations. System-scale hydrologic connectivity exhibits regime shifts, with discharge being the main driver in non-vegetated systems compared to vegetation in vegetated systems. Key findings of this dissertation include: vegetation creates distinct local versus network scale transport effects; seasonal vegetation dynamics promote efficient network organization through biogeomorphic feedback, thereby enhancing system resilience; vegetation induces hydrological connectivity regime shifts that alter system responses to hydrological forcing; and seasonal dynamics are critical for predicting long-term evolution. This research advances understanding of deltaic ecohydromorphodynamics while providing practical insights for coastal management and restoration strategies. Findings demonstrate that coordinating sediment delivery with vegetation cycles can enhance the efficiency of coastal restoration strategies, such as sediment diversions, where network geometric efficiency can serve as a design criterion.
Date
10-27-2025
Recommended Citation
Jean Louis, Madoche, "ECO-HYDRO-MORPHODYNAMICS OF RIVER DELTAS: HOW VEGETATION SHAPES WATER TRANSPORT TIMESCALES, CHANNEL NETWORKS, AND SYSTEM CONNECTIVITY" (2025). LSU Doctoral Dissertations. 6920.
https://repository.lsu.edu/gradschool_dissertations/6920
Committee Chair
Hiatt Matthew
Included in
Geomorphology Commons, Hydraulic Engineering Commons, Hydrology Commons, Other Civil and Environmental Engineering Commons, Water Resource Management Commons