A model coupling ecological and hydrodynamic processes for simulating the biogeomorphology of a coastal salt marsh

A process-based ecological model (SMM-YE) was coupled with a hydrodynamic model (Delft3D) for understanding the biogeomorphology of coastal salt marsh in the Yangtze Estuary. The original SMM-YE mainly consists of modules for seed germination, propagule dispersal, seedling establishment, and biomass growth of marsh vegetation. Delft3D was used to simulate tidal movement, sediment transport, and geomorphological development. Against the field measurements (2014‒2019), the coupled model improved the simulation accuracy of the vegetation expansion pattern and deduced better the spatial heterogeneity of elevation change at the two study sites with different sedimentary regimes, compared to the original SMM-YE. Based on the interactions between vegetation and hydrological processes, the dynamics of marsh-edge scarp movement were also captured with a high match degree by using the coupled model. The model coupling biotic and abiotic processes revealed the simulation superiority in the spatiotemporal heterogeneity of tidal marsh biogeomorphology with high vegetation and hydro-sedimentary dynamics.