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A laterally averaged two-dimensional numerical model is used to simulate hydrodynamics
and cohesive sediment transport in the Tanshui River estuarine system. The model handles
tributaries as well as the main stem of the estuarine system. Observed time series
of salinity data and tidally averaged salinity distributions have been compared with
model results to calibrate the turbulent diffusion coefficients. The overall model
verification is achieved with comparisons of residual currents and salinity distribution.
The model reproduces the prototype water surface elevation, currents and salinity
distributions. Comparisons of the suspended cohesive sediment concentrations calculated
by the numerical model and the field data at various stations show good agreement.
The validated model is applied to investigate the tidally averaged salinity distributions,
residual circulation and suspended sediment concentration under low flow conditions
in the Tanshui River estuarine system. The model results show that the limit of salt
intrusion in the mainstem estuary is located at Hsin-Hai bridge in Tahan Stream, 26
km from the River mouth under Q75 flow. The null point is located at the head of salt
intrusion, using 1 ppt isohaline as an indicator. The tidally averaged sediment concentration
distribution exhibits a local maximum around the null point.