1. A Positive Feedback Between Sediment Deposition and Tidal Prism May Affect the Morphodynamic Evolution of Tidal Deltas
- Author
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Zhang, Xiaohe, Fagherazzi, Sergio, Leonardi, Nicoletta, and Li, Jiufa
- Abstract
Tidal deltas are fragile systems whose morphology can be easily impacted by variations in water and sediment fluxes caused by natural and human processes. Here we explore the relation between tidal prism and sediment dynamics in tidal deltas using the recent evolution of the Yangtze River estuary, China, as an example. Using the numerical model Delft3D, we examine how changes in delta morphology can trigger variations in tidal signal, suspended and bed load transport, and how these could ultimately cause additional morphological changes. Our results show that a positive feedback between sediment deposition and tidal prism dominates the morphodynamic evolution of the delta. Accretion of the shoals in the delta front increases the dissipation of tides and decreases the tidal prism leading to weaker tidal flows. This reduction in tidal currents lowers the sediment flushing capacity of the system, promoting deposition on the shoals and tidal dissipation. This positive feedback potentially traps more sediment in the delta topset and possibly offsets the decrease in sediment load triggered by the construction of upstream dams, often present in tidal deltas. Reduced tidal prism diminishes tidal discharges and peak velocities, preventing sediment flushing and favoring sediment trappingPositive feedback has mitigated the drastic reduction in sediment load triggered in the last decade by the construction of the TGDPositive feedback between deposition and tidal prism highlights the importance of the shoals for the stability of the entire delta
- Published
- 2018
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