What is evidence of longshore drift?

What is evidence of longshore drift?

The transport of sand and pebbles along the coast is called longshore drift. The prevailing wind (the direction the wind ususally blows from) causes waves to approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle (usually 45º).

What does groyne mean?

A groyne (in the U.S. groin), built perpendicular to the shore, is a rigid hydraulic structure built from an ocean shore (in coastal engineering) or from a bank (in rivers) that interrupts water flow and limits the movement of sediment. It is usually made out of wood, concrete, or stone.

How does a groyne work?

A groyne functions as a physical barrier by intercepting sand moving along the shore. Sand is gradually trapped against the updrift side of the structure, resulting in a wider beach on this “supply-side” of the structure. However the downdrift beach is deprived of the sand trapped by the groyne and therefore it erodes.

How much does a groyne cost?

Artificial reefs are estimated cost around EUR 15,000 to 35,000 per running meter of structure (Deltares, 2014). According to Scottish Natural Heritage, in 2000 construction costs for rock groynes ranged between GBP 10,000 and 100,000£ (12,500 – 125,000€) per structure.

How do groynes protect the coastline?

Groynes control beach material and prevent undermining of the promenade seawall. Groynes interrupt wave action and protect the beach from being washed away by longshore drift. Longshore drift is the wave action that slowly erodes the beach.

How can we protect the coastline from erosion?

Sea walls. Concrete walls that are placed at the foot of a cliff to prevent erosion. They are curved to reflect the energy back into the sea.

How can we protect the coasts?

Coastal Protection Methods

1. Sea Wall. In front of the cliff face on the South beach lies a road that winds down to the golden sand.
2. Rock Armour. Rock Armour is when large boulders are placed at the base of soft cliffs or sand dunes.
3. Gabions. Gabions are large wire cages filled with small stones.