A tidal river is a river whose flow and level are influenced by tides. A section of a larger river affected by the tides is a tidal reach, although it may sometimes be considered a tidal river if it has been given a separate name. The Brisbane River, which flows into the Pacific Ocean from the east coast of Australia, is also a tidal river.

Generally, tidal rivers are short rivers with relatively low discharge rates but high overall discharge; generally this implies a shallow river with a large coastal mouth. In some cases, high tides impound downstream flowing freshwater, reversing the flow and increasing the water level of the lower section of river, forming large estuaries. High tides can be noticed as far as 100 kilometres (62 mi) upstream. Oregon's Coquille River is one such stream where this effect can be noticed.



The tidal behaviour of a river is an important consideration in riverboat navigation. For major rivers, such as the Saint Lawrence River (and the associated Saint Lawrence Seaway), publications such as an atlas of surface currents (or tidal currents) may be available, based on sophisticated hydrodynamic models, subject to empirical validation.[1]

Working with the tides instead of against the tides contributes to a low-carbon economy.


See alsoEdit


  1. ^ "The Making of a Surface Current Atlas of the St. Lawrence Estuary, Canada" (PDF), Transactions on the Built Environment vol 40, WIT Press, 1999