On the Effects of Intertidal Area on Estuarine Salt Intrusion

Worldwide, estuaries are increasingly constrained by human interventions, such as wetland reclamations. Intertidal area has an important influence on the extent of estuarine salt intrusion. Previous research has shown conflicting effects of intertidal area on the salt intrusion. Therefore, this study explores this interaction for three estuary classes: (a) salt wedge, (b) partially mixed, and (c) well-mixed. Our findings show that the effect of intertidal area on the salt intrusion depends on the estuary class: enlarging the intertidal area reduces the salt intrusion for salt wedge and partially mixed estuaries, but vice versa for well-mixed estuaries. These opposing responses are explained by the balance between salt fluxes driven by the estuarine circulation versus by the tidal oscillation. In general, enlarging intertidal area results in the suppression of the estuarine circulation. Such system understanding is especially relevant in an era of increasing coastal urbanization.