The impacts of bathymetry and geometry on salt dynamics in well-mixed estuaries.

Xiaoyan Wei, Mohit Kumar, Henk Schuttelaars

Thursday 2 july 2015

11:15 - 11:30h at Europe 1 & 2 (level 0)

Themes: (T) Managing deltas, (ST) Saline and freshwater interaction

Parallel session: 11K. Managing deltas - Saline

Understanding salt dynamics is of great importance to adequately model salt intrusion, baroclinic forcing and sediment transport. In this contribution, we focus on the importance of estuarine bathymetry and geometry on the residual salt transport. An idealized three dimensional model is set up which couples the water motion and salt dynamics for well-mixed estuaries. The tidal velocities and salinity components up to the second order are obtained semi-analytically using a perturbation method, where quantities are expanded in a small parameter (the ratio of the M2 tidal amplitude to the water depth at the estuarine mouth). The model resolves several residual salt transport processes, i.e., the tidal advection due to the correlation between tidal velocity and salinity, and estuarine circulation in both the longitudinal and lateral directions. The unresolved processes are parametrized as diffusive processes using a prescribed along-channel diffusion coefficient Kx , and a cross-channel diffusion coefficient Ky. The response of the salinity distribution for varying estuarine bathymetry and geometry will be investigated, and the relative importance of each salt transport mechanism will be discussed. The results will help to understand the change of salt intrusion as observed in, for example, the Pearl River Estuary, and can provide a scientific basis for estimating salt intrusion in real estuaries.