- Sediment: Naturally occurring material that is broken down by processes of weathering and erosion and is transported by the action of wind, water or ice or by the force of gravity acting on the particles.
- Sediment include silk, sand, gravel, pebbles and boulders
- Sediment comes from:
- Rivers bring material from the land e.g salt marshes in estuaries
- Erosion of coastal land, dunes, cliffs which create sediment.
- Some come from the sea or ocean floor e.g in a storm
- Transported by longshore drift and ‘up and down’ movement of material with tides and storms.
- Longshore drift is a transportation process which involves the constant movement of material along the coast. Waves hit the coast at angles, which washes material along the coast. Known as a marine transport process as it has been moved by water.
- Common to the prevailing wind.
Sediment
Transportation #2:
- Traction: Rocks and pebbles rolling/being dragged
- Suspension: When small sediments like sand and clay particles float up in the water
- Solution: When material has dissolved in the water
How
Does Attitriction From LSD Change Sediment:
- As sediment and shingle move along the beach they wear down and become more rounded. They also get smaller due to the wearing down and larger beach along a coast of shingle – it gets smaller and rounder.
Deposition
Processes:
- Main deposition = gravity setting.
- Moving water carries sediment
- When water calms or slows it does not have the energy to carry sediments
- Sediments settle from the gravity force.
- Forms a beach
- Flocculation = clay particles sticking together and they form a salt marsh as they’re larger and heavier then they start to sink.
- Gravity setting: Faster moving water carries larger sediment and when it slows down it deposited sediment (the biggest drop first)
Beaches:
- The build-up of sediments such as sand and pebbles
- Sources: Cliffs, LSD, river sediments from the sea/ocean
- Material gravity settles along the coast where waters are protected e.g in bays
- Flocculation also contributes sediments where clay particles stick together.
- Sand and pebbles build up enough to form a beach
- A ‘bayhead beach’ is a beach that forms at the end of a bay
- A beach builds up in protected coastal areas with low energy, constructive waves.
- Examples of a bayhead beach are Maya Beach in Thailand.
Spits:
- Long beach peninsula that connects one land to another
- They form by: the prevailing wind and waves hit the coast
- LSD transports sediment along the coast
- When it changes direction a spit can form. Because LSD sediment continues into the sea to form a long sediment peninsula.
Hooked/Recurved
Spits:
- Wind direction often changes
- End of the spit is blown in a different direction e.g into a esturays. This curves the spit and makes it look like a hook e.g Hurst Castle in Hampshire.
Barrier
Beach/Sand Bars:
- A spit forms from LSD
- It grows enough to connect across land e.g across a bay or estuary.
- This is called a bar, barrier beach, or sand bar. Can also be made from shingle.
- It forms a lagoon behind the bar
- The Haff coast is an examples
- Haff: A long shallow lagoon separated from the open sea by a narrow sandbar or barrier beach.
Offshore
Bar:
- A beach or bar that is not connected to the land at all
- Reduction in wave energy might mean sand is deposited by gravity settling as the water is not moving fast enough to suspend the sand.
- Where rivers meet the ocean, the sediment loads can be deposited due to the water speed slowing down, causing a bar to develop
- Finally, offshore bars form when a spit might be cut from the mainland by a storm or waves e.g Ninian Tombolo, Scotland
Tombolo:
- A double-sided beach that is actually a bar that joins to a small island off the coast
- Forms from currents coming in opposite directions and the sediment meets and get deposited
- For example, common behind small island close to the coast. The island breaks incoming waves from the ocean, and wave refraction around the island into sheltered lower-energy waters means sand is deposited through gravity settling
Cuspate
Foreland:
- A large flat area of land that is like a triangle in shape from above
- Land deposited due to complex processes such as long-shore drift from opposite directions building up material
- Can also form when two spits join and the land behind then fills with sediment e.g. from a river
Sediment
Cells:
- Areas of the coast where sediments are roughly contained in that area i.e. there is a source, transfer and sink within the cell
- Created by the key player the Environment Agency (government body) to help understand and manage the coastal processes