The volume between low and high water over the area of a bay, lagoon or estuary, roughly its surface area multiplied by the tidal range. The prism sets how much water must pass through the entrance each cycle, so it controls inlet currents, flushing and the stable cross-section of a natural inlet. Filling marshes or building causeways shrinks the prism, and the inlet tends to shoal in response.
Restoring the marsh adds to the tidal prism, so expect the inlet to scour a bit deeper over a few years.
Also heard as
- prism
- tidal volume
Related terms
Flood
Tidal current running in from the sea and up rivers and estuaries, mostly while the water is rising.
Ebb
Tidal current running out toward the sea and down rivers and estuaries, mostly while the water is falling.
Tidal range
The vertical difference between a high water and the neighbouring low water.
Ebb-dominant
Describes an estuary or inlet where ebb currents are stronger than flood currents, pushing sediment seaward.