Surge channel

A surge channel is a narrow inlet, usually on a rocky shoreline, and is formed by differential erosion of those rocks by coastal wave action.

The narrow confines of the channel create powerful currents that reverse themselves rapidly as the water level rises and falls, and cause violent hydrodynamic mixing.

However, there is relatively little exchange of water between channels; experimental studies and mathematical modelling of the coastline near Hopkins Marine Station in California have shown that water is rapidly mixed within each channel, but that it mostly moves in an oscillatory manner.

Surge channels have been likened to 'containment vessels', retaining water borne gametes and probably enhancing the effectiveness of external fertilisation of marine species dwelling within them.

[3][4] Surge channels can form in reefs,[2]: 14 [5] and the term is sometimes also applied to breaches of coastal dunes by storms.