Sediment transport and deposition creates coastal landforms and landscapes

Sediment transport

PROCESS	EXPLANATION	PARTICLES TRANSPORTED
Traction	Sediment rolled along shoreline, pushed by waves & currents	Pebbles, cobbles & boulders
Saltation	Sediment bounced along the shoreline, driven by either water or wind	Sand
Suspension	Sediment carried in the water	Silts & clays
Solution	Dissolved material	Chemical compounds
Longshore drift	Material moved along shoreline by waves that approach beach at an angle. Swash moves sand & shingle up the beach at an angle (direction of prevailing wind) but the backwash is at right angles to the beach. ↳ The sediment is dropped when the force transporting sediment drops. Deposition can occur in the following ways: • Gravity settling • energy of transporting water becomes too low to move sediment • Flocculation • Small sediment particles clump together due to electrical/chemical attraction & become large enough to sink	All
Currents & tides	Strong underwater currents & tides move sediment in direction of their movement	All

Depositional landforms

LANDFORM	PROCESSES
Spit	• Long, narrow stretches of sand or shingle that protrude into sea • Materials moved along coast by longshore drift • Direction of movement continues despite coastline curving or where there is an estuary
Bay beach	A swash-aligned feature where waves break and move sediment into a bay where a beach forms ↳ Deposition can occur in the bay as wave energy is refracted by headlands
Tombolo	• Formed where a spit joins the mainland at one end to an island at the other
Barrier beach/Bar	• Where a spit has developed right across a bay because there are no strong current to disturb the process • A lagoon is formed behind it
Hooked spit	• A spit which end is curved landward • Hook caused by more pronounced waves from a secondary prevailing wind
Cuspate foreland	• A triangular shaped feature extending out from a shoreline • They are formed due to two dominant wind & wave patterns causing deposition from two directions

A cuspate foreland

The sediment cell concept

Positive feedback

🔗 Where a change causes a further effect, continuing or even accelerating the original change

Negative feedback → Acts to lessen the effect of an original change & ultimately reverse it

🔗 A sediment cell is comprised of sources, transfers and sinks (closed system) - constantly trying to reach a dynamic equilibrium

• Erosion in one place (source) can be balanced by deposition in another eg. spit (sink) - due to transfers of sediment w/in the cell (eg. longshore drift, currents etc) Sediment budget → Amount of sediment gained from sources & lost to sinks

Sediment cells