Estuarine dams can result in profound changes to estuarine environments.
However, their impact on estuarine currents, stratification, and
sediment fluxes is not well understood. To develop a general
understanding, an idealized modeling study was carried out using the
Coupled-Ocean-Atmosphere-Wave-Sediment Transport Modeling System.
Idealized estuarine geometry was based on 10 estuaries with estuarine
dams. Tide and river forcing were varied to produce strongly stratified,
partially mixed, periodically stratified, and well-mixed estuaries. Each
model ran for one year. Next, the models were subject to the
construction of an estuarine dam and run for another year. Then, the
pre- and post-dam conditions were compared. Results showed that
estuarine dams amplify the tidal range and reduce the tidal currents.
The post-dam estuaries tended to be salt wedge and strongly stratified
types during freshwater discharge, but during no freshwater discharge
they became fjord, bay, or periodically stratified types based on the
estuarine parameter space. For all estuaries, the estuarine turbidity
maximum moved seaward, and the suspended sediment concentrations tended
to decrease. While the depth changes depended on the estuary type, the
surficial sediment texture shifted to being muddier for all types. In
terms of sediment flux mechanisms, the estuarine dam reduced the
exchange flow and Stokes transport. The estuarine dam also increased the
seaward river runoff for cases with strong river, and increased the
landward tidal pumping for cases with strong tides. This study is one of
the first to generalize the effect of estuarine dams to a range of
estuarine types.