Sediment transportation, LSD and landforms

What is traction?

• sediment rolls along the sea floor, pushed by waves and currents

• The sound of it can be heard from the beach

• Pebbles, cobbles and boulders are moved

What is saltation?

• sediment bounces along

• Caused by wind or the force of water

• On dry windy days bouncing sediment can be seen on shore

• Small, sand sized particles

What is suspension?

• sediment is carried in the water column

• Soft rock coasts (holderness) the sea is often brown due to suspended silt and clay

What is solution?

• dissolved material is carried in the water as a solution

• Of limited importance

• Limestone is carried as chemical compounds

What is a swash aligned coast?

Waves meet parallel to the coast

Limited longshore movement of sediment

What is a drift aligned coast?

• wave crests break at an angle to the coast so sediment is carried and deposited at an angle

• This causes consistent LSD and elongated depositional features

What is the formation of (recurve) spits? - Spurn Head (spit) -Hurst Castle (recurve)

Spit

• LSD continuously deposits sediment beyond a turn in the coastline

• Length is dependent on amount of sediment transported or the flow of a river carrying sediment away

Recurve

• when the end of a spit curves landwards into shallower water due to secondary wind

Bayhead beach - lulworth cove, Dorset

• swash aligned coast deposits sediment to form a beach

• Due to wave refraction and erosion is concentrated on headlands beaches eventually have more deposition

Bar/ barrier beach - Chesil beach

• drift aligned

• A sand or shingle beach connecting two areas of land with a shallow water lagoon behind

• This is caused when a spit grows so long it extends across a whole bay, closing it off

Tombolo - St Ninions, Shetland

• drift aligned

• A sand/shingle bar that connects to an offshore island

• Forms due to wave refraction around an island that creates an area of still water when it collides

• Deposition increases

• Opposing LSD currents can also cause still water also

Cuspate Foreland - Dungeness Kent

• drift aligned

• A triangular shapes feature extending out from a shoreline

• Thought to form from the growth of two spits from opposing LSD directions

What is gravity setting?

• energy transporting water becomes too low to carry sediment

• Large sediment us deposited first

Why are depositional features vulnerable?

• Made from unconsolidated material

• Vulnerable to change

• Dynamic

• Storms can cause change

• Storms at spring tide can cause more extreme change

• Leads to redeposition elsewhere