Influence of bathymetric changes on hydrodynamics and salt intrusion in estuarine system

A vertical (laterally integrated) two-dimensional numerical model has been applied to study the hydrodynamic characteristics and salt water intrusion in the Tanshui River estuarine system. The cross-sectional profiles measure d in 1978 and 1994 are schematized for model simulations. Detailed model ca libration and verification have been conducted with water surface elevation s, tidal current, salinity distributions, and residual velocities measured. The overall performance of the model is in qualitative agreement with the available field data. The model was then used to study how hydrodynamics an d salt water intrusion change in response to changes in bathymetry. The mod el simulations indicate that more tidal energy propagates into the estuarin e system in 1994 because of the substantial increase in river cross-section s. The limits of salt intrusion in 1994 extended farther inland than those in 1978. On the other hand, the extent of mangrove wetland in the lower est uary has increased over the past 20 years and is likely a result of the inc reased salinity in the estuary.