2B.11a hard engineering approaches

Question 1

groynes

Answer 1

• timber or rock structures built at right angles to the coast
• they trap sediment being moved along the coast by longshore drift and build up the beach

PROS
- the built-up beach increases tourist potential and protects the land behind it

• relatively inexpensive - £5,000 to £10,000 each (at 200-metre intervals)

CONS
- groynes starve beaches further along the coast of fresh sediment because they interrupt longshore drift –> increased erosion elsewhere

• unnatural and rock groynes are unattractive

Question 2

sea walls

Answer 2

• made of stone or concrete at the foot of a cliff or at the top of a beach
• usually, have a curved face to reflect waves back into the sea

PROS

• often have a long promenade for people to walk on
• effective prevention of erosion

CONS

• they reflect wave energy rather than absorbing it
• they can be intrusive and unnatural looking
• (the most expensive coastal defence) - build & maintain (£6,000 a metre)

Question 3

rock armour

Answer 3

• large rocks placed at the foot of a cliff or at the top of a beach
• forms a permeable barrier to the sea, breaking up the waves

PROS
- relatively cheap and easy to construct and maintain (about £50 per m^3)

CONS

• can be very intrusive
• rocks can be dangerous

Question 4

revetments

Answer 4

• sloped walls, often made of wood, placed parallel to the backshore
• they are able to take the force of breaking waves, they weaken their erosive strength and protect the backshore

PROS
- relatively inexpensive to build (up to £4,500 a metre)

CONS

• look intrusive and unnatural
• need high levels of maintenance

Question 5

offshore breakwater

Answer 5

• a partly submerged rock barrier designed to break up the waves before they reach the coast

PROS
- an effective permeable barrier

CONS
- visually unappealing
costly, between £1 million and £2 million

Question 6

Holderness

Answer 6

only 9.2km of the Holderness (85km long) are protected by hard-engineering structures

Question 7

groynes example

Answer 7

MAPPLETON
two rock groynes were built in 1991
at Cowden (3km south of Mappleton), the resultant sediment starvation caused erosion of the cliffs to increase from 2.5m a year to 3.8 between 1991 and 2007)

Question 8

sea wall example

Answer 8

WITHERNSEA

a straight sea wall was built was 1875 but over time, wave energy scoured the base of the wall, causing it to collapse

Question 9

hard-engineering

Answer 9

this involves building structures along the coast