Coastal Deposition Landscapes

Transportation

Transportation is the movement of material by the sea. The material carried by the sea is called load and is usually material that has been eroded and picked up by waves. The load carried by the sea varies from large rocks to fine silt. There are 4 specific processes of transportation that you need to know:

• Traction - this is where large rocks and boulders are rolled along the sea floor.

• Saltation - this is where small stones and pebbles are bounced along the sea floor.

• Suspension - this is where light material is held in suspension just below the surface of the sea (suspended load). 

• Solution/Dissolved Load - this is where minerals are dissolved in the water and tiny invisible particles are transported by the sea (not to be confused by the erosional process of solution!).

Deposition

Coastal deposition is an important aspect in the development of our coastlines especially for those islands here in the Caribbean. A major part of coastal deposition is the influence of constructive waves that deposit their load to create these natural features overtime. There are two terms that need to taken note of before we embark on discovering the deposition landforms. They are:

• Longshore Drift - Longshore drift is the movement of material along the coastline in a zig-zag fashion. Waves hit the coastline at an angle (the same direction as the wind), so the swash goes onto the beach at an oblique angle. Once the wave breaks the backwash returns to the sea at right angles to the coastline (due to gravity). This movement is repeated, transporting material from one end of the beach to the other. (See diagram below for a visual)

The coastal features formed through Coastal Deposition are as follows:

• Beaches - a deposit of sand an/or pebbles found at the coast. Beaches are in fact the most common and widespread landforms acknowledged for coastal deposition. Sandy beaches are formed in sheltered stretches of coasts where the constructive waves are only capable of carrying finer sediments. Meanwhile beaches with more shingle than sand tend to form along high-energy coastlines where the transportation and deposition of heavier sediments are possible.

It should be acknowledged that Bayhead Beaches are also a thing. This occurs where deposition has taken place due to wave refraction. This is due in part to the waves entering the bay having less energy than those at the headlands.

• Spit - this can be described as a narrow finger of sand or pebbled that juts out into the sea from the land. This forms when Longshore Drift occurs along a coastline and meets a bend. 

Breakdown of the formation: The load being transported over time extends into the sea at the point where the coastline changes its shape (the bend). Fine muds are deposited in the very calm sheltered water behind a spit to form a mudflats and saltmarshes. The tip of the spit becomes curved to form a recurved tip or hook owing to changes in the wind and wave direction.

It should be noted that the spit is formed above sea level (it is actual land) meaning it does not become submerged by the sea at high tide.