Fagherazzi, SergioXu, Yiyang2025-09-222025https://hdl.handle.net/2144/512442025The valuable ecosystem services provided by salt marshes are driving restoration projects worldwide. However, predicting the final vegetated area based on physical drivers remains challenging. In this study, we utilize a fully coupled 3D vegetation-hydrodynamic-morphological modeling system to simulate both the final vegetation cover and the timescale required to reach it under various environmental conditions. Our simulations reveal that marsh development occurs in three distinct phases: a preparation phase, marked by sediment accumulation in the absence of vegetation; an encroachment phase, during which vegetation expands; and an adjustment phase, where the vegetated area stabilizes while the marsh vertically accretes to accommodate sea level rise.Key drivers such as sediment concentration, settling velocity, sea level rise, and tidal range all significantly influence the equilibrium vegetation cover and the timescale of marsh development, though their effects vary. Our simulations also indicate that the Unvegetated-Vegetated Ratio is closely related to the sediment budget during marsh development under most conditions. To better understand the dynamics of coastal tidal flats transforming into vegetated salt marshes, we implemented a state-of-the-art numerical model. This model reveals that areas with rapid geomorphic reorganization tend to experience high sediment convergence and local resuspension, leading to the formation of deep channels adjacent to accreting salt marshes. These areas typically lie at the end of major sediment transport pathways. Geomorphic reorganization spreads progressively as sediment pathways extend landward. Tidal flows—both flood and ebb—play distinct roles in shaping the intertidal landscape. Flood flows deposit sediments at the terminus of sediment pathways, while ebb flows carve new channels around these deposits. Over time, these depositional areas evolve into salt marshes. Once formed, new channels are reoccupied by flood flows, creating a self-sustaining process that drives marsh expansion landward. This hydro-dynamically controlled sediment delivery and deposition, akin to flood tidal deltas, promotes landscape autogenic divergence.We simulated four coastal bays using realistic suspended sediment concentrations, employing the same modeling framework to mobilize sediment onto the marsh during five typical tidal cycles. Our results show that sedimentation patterns vary geographically, which we attribute to differences in marsh elevation. Lower marshes, more frequently flooded, receive larger sediment loads, leading to higher sediment deposition in these areas.en-USAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/GeophysicsGeomorphologyThesis/Dissertation2025-09-190000-0002-2266-4743