transportation longshore drift oblique angle deposition sand spit salt marsh
baymouth bar tombolo lagoon beach undertow backshore
foreshore runnel ripple cusp berm
The mud, sand, shingle, pebbles and stones found in the sea and carried along by waves is referred to as the waves load. These materials have been sourced a number of ways: zz
zz zz
they were brought inland from offshore by constructive waves; they were transported along the coastline by longshore drift.
Longshore drift
Coastal materials such as sand and silt are transported along the coast by longshore drift. The prevailing wind causes waves to approach the coast at an oblique angle. The swash moves material up the shore, while the backwash brings it straight back out, following the slope of the shore. The sequence is repeated and in this way material is moved along the shore in a zigzag pattern (Fig. 9.14).
Movement of sand particles
Beach Sea
SKILLS ACTIVITY
Draw a labelled diagram describing the process of longshore drift.
they were eroded from the coast by destructive waves that were forming the features of coastal erosion;
Longshore drift
direction Fig 9.14 Longshore drift. Coastal Deposition
Just like a river in its ‘old age’, the sea deposits the load it has been carrying when it loses its energy. Deposition is carried out by constructive waves whose swash is stronger than their backwash.
Deposition is most likely to occur: zz zz zz
in shallow waters, such as bays, where waves slow down due to wave refraction; when waves enter sheltered areas (bays/coves);
in calm weather when there is little wind and the wave only has a limited amount of energy.
