This page shows tidal cycles in the Waikareao estuary modeled by Tay 2011.
The bar on the left shows current velocity.

It demonstrates how the upper reaches of the estuary are exposed for long periods during a tidal cycle, this has a large influence on species composition.

Reference:

Tay, H. W. (2011). Nutrient dynamics in shallow tidally- dominated estuaries. (Doctoral dissertation) University of Waikato, Hamilton, New Zealand. Retrieved from http://researchcommons.waikato.ac.nz/