Coastal transport and deposition

Question 1

What is longshore drift?

Answer 1

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

Question 2

Where does longshore drift occur?

Answer 2

It occurs on the beach foreshore and the nearshore seabed

Question 3

What drives LSD in the foreshore zone?

Answer 3

Waves

Question 4

What drives LSD in the nearshore zone?

Answer 4

Currents

Question 5

What happens during LSD if the updrift supply of sediment is interrupted?

Answer 5

It is no longer able to replace the sediment it removes

Question 6

What is an example of LSD being unable to replace the sediment it removes?

Answer 6

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

Question 7

Why isn’t Benin’s beach being replenished by updrift LSD?

Answer 7

Largely due to Ghana’s Akosombo Dam which traps river sediment resulting in sediment starvation and therefore coastal erosion down drift

Question 8

What are tides?

Answer 8

Tides are rapid changes in sea level due to the gravitational pull of the moon and sun

Question 9

What does swash aligned mean?

Answer 9

Sediment moves up and down the beach with little lateral transfer

Question 10

What does drift aligned mean?

Answer 10

Sediment is transferred along the coast by longshore drift

Question 11

What happens when a drift aligned beach meets a change in coastal direction?

Answer 11

I forms a spit

Question 12

What is an example of somewhere with a double spit as a result of LSD?

Answer 12

Poole Harbour in Dorset

Question 13

Where is an example of a barrier beach enclosing a lagoon?

Answer 13

Swanpool Beach in Cornwall

Question 14

Where is an example of a cuspate foreland?

Answer 14

Dungeness in Kent