Coastal transport and deposition Flashcards
What is longshore drift?
Lateral (sideways) transport of sediment as swash pushes it up the beach and backwash pulls it down the beach at 90 degrees to the shore
Where does longshore drift occur?
It occurs on the beach foreshore and the nearshore seabed
What drives LSD in the foreshore zone?
Waves
What drives LSD in the nearshore zone?
Currents
What happens during LSD if the updrift supply of sediment is interrupted?
It is no longer able to replace the sediment it removes
What is an example of LSD being unable to replace the sediment it removes?
Benin, West Africa where there are prevailing SW winds and a long fetch and it suffers from major LSD and the coastline is receding by 10 metres/year
Why isn’t Benin’s beach being replenished by updrift LSD?
Largely due to Ghana’s Akosombo Dam which traps river sediment resulting in sediment starvation and therefore coastal erosion down drift
What are tides?
Tides are rapid changes in sea level due to the gravitational pull of the moon and sun
What does swash aligned mean?
Sediment moves up and down the beach with little lateral transfer
What does drift aligned mean?
Sediment is transferred along the coast by longshore drift
What happens when a drift aligned beach meets a change in coastal direction?
I forms a spit
What is an example of somewhere with a double spit as a result of LSD?
Poole Harbour in Dorset
Where is an example of a barrier beach enclosing a lagoon?
Swanpool Beach in Cornwall
Where is an example of a cuspate foreland?
Dungeness in Kent
