3. Coastal Deposition
What is coastal deposition?
Coastal deposition is the opposite of coastal erosion:

Waves have less energy so deposit (drop materials)

Constructive waves are active – the swash is strong so carries material towards the beach.

Tends to create features made of sand- beaches (sand or shingle), sand spits, sand bars, tombolos,
lagoons and salt marshes.
The Process of Long Shore Drift
Sand spits are formed by the process of long shore drift.
The swash transports materials in constructive waves
towards the beach. The direction of the swash is
determined by the angle of the prevailing wind. The swash
deposits materials on the beach.
Backwash removes materials from the beach at a right
angle and carries it back out to sea, before swash takes
over and transports it back to the beach.
The process of swash and backwash continues and effectively moves sand along the beach.
Sand-Spit Formation
A sand-spit is formed when the materials carried by the swash are deposited at the end of the beach. In
order for a sand-spit to form, the following events must happen:
1.
The coastline must change direction.
2.
The water must be shallow and gentle to allow the deposits of sand to build up and stabilise.
Sand Bar and Lagoon Formation
A sand bar is created from a sand spit.
The sand spit continues to grow, and eventually hooks up/meets the other side of a bay. This cuts off a
body of water from the sea, forming a lagoon.
Tombolo
A tombolo forms when the sand spit
continues to grow and joins up with a
nearby island.
CfE Higher Geography: Lithosphere
Dalziel High School
D.Gallacher 2015