The aim is to protect the coastline by preventing the waves eroding the coastline

Involves the use wood, concrete or stone

Sea walls Revetment Gabions Groynes Rip-rap Offshore breakwater http://www.think-energy.com/ThinkEnergy/1

6-18/case-studies/case-study-5.aspx

Made of stone or concrete.

Reflects waves and withstands waves breaking on it

The wall prevents the base of the cliff being eroded away

May have a curved top to reflect more wave energy

Advantages◦ Strong and sturdy will last a

long time Disadvantages

◦ Ugly◦ Expensive

The base of the wall can be undercut by the sea resulting in it collapsing into the sea.

Often rip-rap is placed in front of the wall to prevent this

A sloping concrete or wooden wall with gaps between each piece

Can have stones piled up behind them

They dissipate (weaken) the strength of the waves beforeing hitting the cliffs

Advantages◦ Fairly cheap

Disadvantages◦ Are laid on a beach

which can disrupt access to the sea and tourist activity

◦ Do not last that long

Strong wire baskets filled with stones that gradually get covered with grass and sand

The stones dissipate the strength of the waves before they hit the cliffs

Can be placed on a beach or in front of a cliff

Advantages – dissipate the energy of the waves before hitting the cliffs thus preventing erosion, cheap,

Disadvantages – ugly, may not last a long time

A low wall built out into the sea

This traps sand that is moved by longshore drift

This reduces erosion as there is a larger beach, which absorbs more wave energy

This means if any waves do hit the cliff they have a much reduced energy, which results in less erosion

Advantages◦ Help to create a larger

beach which is good for tourists

◦ Traps sand and pebbles, making a bigger beach preventing less cliff face erosion

Disadvantages◦ Prevents the movement

of sand down the coast leaving other areas unprotected and move vulnerable to erosion (see Holderness case study

Material is trapped here, so the land is higher up

This is the last groyne, no more sand is trapped which leaves these cliff vulnerable to erosion

Large interlocking man-made boulders which protect the coast by breaking up the waves.

Advantages◦ A cheap(ish) way of

protecting the coastline when used with other sea defences. For example a sea wall. Rip-rap placed at the base to prevent undercutting of the sea wall

Disadvantages◦ Ugly

Located in the sea below the low water mark

It may be dumped interlocking material or concrete wall

Protects the shore from all waves

Offshore breakwaters

Advantages – protects the shore from all waves

Disadvantages -ugly, will ruin the surfing tourist industry

Cliff collapse, beach nourishment

Cliffs made of sand or clay are said to be made of soft rock

This makes them very susceptible to erosion

The soft rock absorbs rainfall and becomes waterlogged. This makes it heavy. When the base of the cliff is eroded by waves a portion of the cliff will slump.

Drainage pipes to remove excess water

A sea wall may be placed at the base of the cliff to prevent erosion

Geotextiles - this is a webbing that is nailed to the cliff and helps to hold the cliff together

Replaces material lost by erosion each year.

•Advantages•Cheap•Uses natural materials

•Disadvantages•Uses dredged material from out to sea. This means there is less material protecting the coastline and reduce the energy of incoming waves. This results in waves with more energy hitting the coastline. This could increase the rate of erosion

To protect or not to protect?

Protecting the coastline costs a lot of money The Government has to decide whether to

protect the coastline To do this it puts an economic (money) value

on the land to be protected. If this ‘value’ is more than the cost of the sea

defences then the coast will be protected If the value of the land is less than the cost of

the sea defences then the coast will not be protected

Farmland has low economic value so often is left to the sea in what is termed ‘managed retreat’

Managed retreat is the letting of the land to erode into the sea

Houses and businesses are generally protected but it is not always the case◦ See Happisburgh case study