Spits and Lagoons

Spits are long, linear stretches of beach material which have a curved tip. They are found wherever there is a sudden change in the direction of a coastline.  They are depositional features which result from longshore drift and coastal sea currents.  Longshore drift causes material to be moved along a coastline.  Longshore drift aids deposition.  When an oblique wave reaches a coastline, material is swashed diagonally up the beach. The backwash carries material vertically back down the beach where it meets another incoming wave which moves it diagonally up the beach again. In this way, longshore drift moves material along a beach.

At the point where the coastline changes direction, the oblique waves lose their energy and material is no longer carried.  Deposition occurs and the beach is effectively lengthened.  Also, ocean currents carry material along the coast.  These also lose energy where the direction of the coast changes leading to deposition.  Over time a spit will develop.  Spits are commonly found at river mouths with wide estuaries. The curved tip of a spit results from the effect of incoming waves which spread wider and curve as they enter the estuary or as a result of an opposing wave acting against the tip of the spit. Spits may develop across a bay and lead to the formation of a lagoon – a lake cut off from the sea but which may flood at high tide. Donegal golf course is built on a spit.  Inch Strand on the Dingle peninsula is also a spit.