Coastal transport- longshore drift questions

Question 1

Describe the process of longshore drift [3]

Answer 1

Sediment is moved along the coastline in a process known as longshore drift. The prevailing wind blows waves carrying sediment into the beach at an angle (swash), the waves break on the shore and as the water runs back into the sea it carries the sediment back down the beach, perpendicular to the angle of the shoreline under the influence of gravity (backwash). This results in a zigzag motion as sediment is transported along the coastline. This process means that over time beaches can change shape.

Question 2

What is longshore drift [1]

Answer 2

The angled approach of waves due to the direction of the prevailing wind

Question 3

What is longshore drift and what coastal defence mechanism is associated with it? Give examples

Answer 3

The prevailing wind is the known common direction that the wind blows along a coast, whether that is east, south west etc. it is specific to each specific site. Longshore drift is the movement of sediments along a coast. The direction of the local prevailing winds dictate which direction the sediments will move. Longshore drift causes a zig zag movement of the sediment along the coast as the swash moves the sediments 45 degrees up the coast and the backwash pulls the sediments 90 degrees back towards the sea, see diagram.Groynes are wooden structures that help prevent the movement of sediment along a coast (see diagram); this may be desirable in areas that want to develop more sand along their coasts whether that be for tourism or as a further coastal defence system. The north wales coast shows a distinct longshore drift movement eastwards from Rhos to Rhyl. Groynes are present here.