TRANSPORTATION AND DEPOSITION

Coastal transportation and deposition are both important coastal processes. (Forces or actions that shape the coasts)

Deposition; Deposition occurs when the sea lacks enough energy to carry its load(the forces responsible for sediment transportation are overcome by the weight of the matter carried or friction) or when large amounts of sediment are made in the river system. Beginning with the heaviest material, it drops its load of sand, rock particles, pebbles, sediment or shingle. Deposition will most likely occur when sea loses energy because the swash is stronger than the backwash. This happens when either waves enter an area of shallow water, waves enter a sheltered area or there is not enough wind so the waves slow down and deposit material. The location is also a factor, so coastal deposition will occur where there are large supply of materials from cliffs, rivers, beaches, or an irregular coastline. A sheltered location so that there is very little wave erosion, a gentle slope and a large load all contribute to the amount of deposition.

external image Beaches.jpg
Many landforms can be formed in addition to coasts by deposition such as: Bar, spit, tombolo and cupsate foreland. The formation of spits, for example, depends on the longshore drift. Spits are formed when longshore drifts and the shoreline do not go in the same direction. They have a strange feature which can be detached from the land and can take a hook-shape or curve.

Longshore drift: Longshore drift occurs when waves approach a coast line at an angle, due to the wind. Therefore there is a sideways component to the swash which moves the Material being transported diagonally up the beach. The longshore drift is therefore influenced by the swash as well as the backwash because the backwash provides the vertical movement due to gravity. The factors that generate longshore drift are; suspended and bed load transport,the type of waves and the quantity of wind. Because heavier material is harder and takes more time to move it can grade the beach material. The coarsest materials tend to be found at the limit of the wave action.

File:Longshore drift.svg
File:Longshore drift.svg

Transportation: Transportation is the movement of sediments due to the sea, it is very similar to Longshore drift except that is does not only take place at the coast.
Here is an amination explaining transportation and longshore drift
longshore.2.gif