Some Coastal Landforms are Caused by Deposition


  • Form when constructive waves deposit sediment on the shore.
  • Shingle beachesare steep and narrow; have large particles.
  • Sand beachesare wide and flat; have small particles.
  • Berms- ridges of sand and pebbles found at high tide marks.
  • Runnels- grooves in the sand running parallel to the shore, formed by backwash draining to the sea.
  • Cusps- crescent-shaped indentations that form on beaches of mixed sand and shingle.



  • Longshore drift- deposits material across the river mouth, leaving a bank of sand and shingle sticking out into the sea.
  • Simple spit- straight spit that grows out parallel to the coast.
  • Occasional changes to the dominant wind and wave direction may lead to a spit having a curved end.
  • Compound spit- a spit with multiple recurved ends.
  • The area behind the spit is sheltered and so develops into mudflats and saltmarshes.




Offshore Bars and Tombolos

  • Bars- formed when a spit joins two headlands together. This can occur across a bay or across a river mouth.
  • A lagoonforms behind the bar.
  • Bars can a form off the coast when material moves towards the coast. These may remain partly submerged by the sea – offshore bars.
  • A bar that connects the shore to an island is a


Barrier Islands

  • Long, narrow islands of sand that run parallel to the shore ad are detached from it.
  • Form in areas with a good supply of sediment, a gentle slope offshore, powerful waves and a small tidal range.
  • Formation: ice melt caused rapid sea level rise; flooding the land behind beaches; transported sand offshore; deposited in shallow water.
  • A lagoon or marsh forms behind the barrier island, where the coast is sheltered.


Sand Dunes

  • Formed when sand deposited by longshore drift is moved up the beach by the wind.
  • Sand trapped by driftwood or berms is colonised by plants and grasses. The vegetation stabilises the sand and encourages more sand to accumulate there, forming embryo dunes.
  • Over time, the oldest dunes migrate inland as newer embryo dunes are formed.
  • Mature dunes can reach 10m in height.


Estuarine Mudflats and Saltmarshes

  • Mudflatsand saltmarshes form in sheltered, low-energy environments.
  • As silt and mud are deposited by the river or the tide, mudflats develop.
  • Mudflats are colonised by vegetation that can survive the high salt levels and long periods of submergence by the tide.
  • Plants trap more mud and silt, and gradually they build upwards to create an area of saltmarsh that remains exposed for longer and longer between tides.
  • Erosion by tidal currents or streams forms channels in the surface of mudflats and saltmarshes. These may be permanently flooded or dry at low tide.