GCSE geography physical cliff collapse case study and managment

Barton-on-sea is a small settlement in the christchurch bay in Hampshire.

It has been badley effected by cliff collapse and over the years many buildings have fallen into the sea. As a result extensive coastal defences have been built which have been moderatly effective with some land-slips still occuring.

the cillf collapse is due to:

• the rock is made of weak sand and clay which is very unstable.
• permeable sand on top of impermeable clay which means water cant escape and make the cliffs very heavy.
• very strong prevailing winds increse the rate of erosion
• building on top of the cliffs increase the weight and interfere with drainage.

Hard engineering involves using artifiacal structures to control the force of nature.

Sea Walls:

concrete or rock barrier built at the foot of clifs or at the top of a beach. Has a curved face to reflect the waves back into the sea, uaually 3-5m high. costs up to £10million per Km.

Advantages: effective. often has a walkway or promenade for people to walk along

Disadvantages: obtrusive and looks unnatural. very expensive and has a high mantainance cost.

Groynes:

Timber or rock structures built out to the sea from the coast. They trap sediment being moved by long-shore drift, and broaden the beach. the wider beach acts as a buffer to the incoming waves, reducing wave attck at the coast. they cost up to £5,000 per metre.

Advantages: results in a bigger beach which helps with tourism. provides useful structure for fishers. not too expensive.

Disadvantages: by stopping long shore drift it starves the beach of sediment further up the coast. can cause visual pollution.

Rock armour:

piles of large boulders dumped at the foot of the cliff. the rocks force the wave to break, absorbing their energy and protecting the cliffs. the rocks usually brought in by barge to the coast. they cost £1,000-£4,000 per metre.

Advantages: relativly cheap and easy the maintain. can provide habitat for wildlife.

Disadvantages: expensive to transport the the rocks from abroad. do not fit with loacl geology. obtrusive.

Soft engineering try to work with the natural coastal processes and they do not involve artifical structures.

Beach norishment:

the addition of sand or shingle to an existing beach to make it higher and broader. the sediment is usually obtained locally s that it blends and there is less transport.cost about £3,000 per metre

Advantages: relativly cheap and easy to maintain. blends in with existing environment. increases tourist potential.

Disadvantages: needs constant maintenance unless structures are built to retain the beach.

dune regeneration:

sand dunes are effective buffers to the sea yet thet are easily damaged and destroyed, especially by trampling. marram grass can be planted to stabilise dunes and help them to develop. areas can be fenced to keep people off newly planted dunes. They cost about £2,000 per 100m.

advantages: maintains a natural coastal environment that is popular with people and wildlife. relativly cheap

disadvantages: time consuming to plant the marram grass and fence off. damaged by storms. people don't like not being allowed to go somwhere. 

marsh creation:

this invloves allowing low-lying coastal areas to be flooded by the sea to become salt marshes. this is an example of managed retreat. salt marshes are effective barriers to the sea. They cost £5,000-£10,000 per hectare depending on land value.

Advantages: quite cheap. creates habitat for wildlife.

Disadvantages: loss of land. farmers need to be compensated.