INTERACTION BETWEEN HYDRODYNAMICS AND SALT MARSH DYNAMICS: AN EXAMPLE FROM JIANGSU COAST

Abstract

Salt marshes are distributed along more than 400 km of the Jiangsu coast in Eastern China, which are regarded as important habitats and serve as coastal protection as well. Previous research has proven that salt-marsh vegetation can reduce current velocity and dampen waves by its stems and leaves. Reversely, hydrodynamic forces also have a significant influence on the growth of salt-marsh vegetation. To study the interaction between hydrodynamics and salt-marsh development on the Jiangsu coast, a 2D schematized model has been built by using a new interactive structure between flow, wave and vegetation modules of the process-based model Delft3D. In the hydrodynamic simulations, the impact of vegetation on waves and currents is quantified. In the vegetation growth module, the development of salt marshes is influenced by inundation time and shear stress from hydrodynamic simulations. The feedback loop is completed by hydrodynamic modules receiving the newly updated data of salt-marsh field from the vegetation growth module. The results show that wave height and current velocity are significantly influenced by vegetation. Reversely, the dynamics of marsh vegetation greatly rely on hydrodynamic conditions. Consequently, this interaction between hydrodynamics and salt marsh induces temporal variations of each other. In the model, the salt marsh is especially sensitive to the waves. Though wave height is relatively small on the Jiangsu coast, in terms of bed shear stress, waves may be of great importance to the development of salt marsh.