Case Study Coastal Management

Question 1

Location?

Answer 1

Overstrand, North Norfolk

Question 2

Reasons for protection: rapid erosion - waves?

Answer 2

Waves are very powerful as they’ve built up over fetch of 3000km and are more destructive. Prevailing wind direction is from NE so waves but cliff almost straight on.

Question 3

Reasons for protection: rapid erosion - cliff?

Answer 3

Cliff is v weak - chalk bedrock is covered by thick 2-5m layer of glacial till which is unconsolidated so erodes easily and is particularly unstable when wet - as v heavy!

Question 4

Reasons for protection: rapid erosion - effects?

Answer 4

Rapid erosion leads to collapse and retreat of the cliffs, ave. 1m per year at Overstrand although a single storm can erode hundreds of tonnes of material

Question 5

Reasons for protection: rapid longshore drift - waves?

Answer 5

Waves approach the coastline at an angle - they approach NNE facing coastline from NE which is prevailing wind direction

Question 6

Reasons for protection: rapid longshore drift - effects?

Answer 6

Moves material from SE to NW, waves move up beach at angle but return at right angles due to gravity - material therefore moved along beach from SE to NW in process.
Moves about 2000METER CUBED of sediment/year

Question 7

Reasons for protection: interaction of erosion&longshore drift?

Answer 7

Longshore drift quickly removes material (glacial till) that has been eroded from the cliff, leaving base of cliff exposed to further attack by waves.

Question 8

Measures taken: sea wall?

Answer 8

• Concrete w stepped section at base.
• It absorbs and deflects force of waves, prevents waves from attacking cliffs behind.
• Steps dissipate energy of retreating wave weakening backwash and minimising removal of material from beach.
• Crenelated front helps dissipate breaking wave energy further.

Question 9

Measures taken: wooden groynes?

Answer 9

• Some zig zag and some straight
• Reduced longshore drift by trapping material as it moves along beach
• Zig zag structure is to inc. SA where material can be trapped
• Some gaps exist to ensure small amount of sediment are able to move
• 13 to the SE and 3 to the NW of Overstrand sea wall

Question 10

Measures taken: drainage pipes?

Answer 10

• Remove excess water from cliffs
• This prevents unconsolidated glacial till in cliffs becoming heavy and unstable
• Reducing likelihood of slumping

Question 11

Resulting effects: erosion?

Answer 11

Overall reduction in rate of erosion - it is only 1m per year compared to much higher rate before implemented.
This is largely due to sea wall which prevent powerful waves reaching weak cliffs behind.

Question 12

Resulting effects - cliff?

Answer 12

Cliffs remain unstable as there is visible evidence of continued regular cliff slumping proving that drains are not wholly effective.
However, this is not as regular as it used to be show by vegetation growth on cliff face.

Question 13

Resulting effects: longshore drift?

Answer 13

Longshore drift continues and groynes are not v effective at trapping the sandy beach sediment - this was shown by minimal build up of beach material on southern side of groyne.

Longshore drift at Overstrand moves 2000 METRES CUBED sediment/year

Question 14

Possible conflicts: locals?

Answer 14

Locals want better coastal defences as some are ineffective (e.g. Groynes) and some need repair (e.g. Wooden revetments damaged by winter storms) and so cliff retreat continues at ave. rate of 1m per year.
Locals want better defences for better protection to property and farmland.

Question 15

Possible conflicts: local government?

Answer 15

Lack of funding from the local gov. because Overstrand is only a small settlement with pop. 1100 it is not high priority for them and so funding given to larger settlements on coast e.g. Sheringham NW of Overstrand w over 7000 residents & has much larger sea wall

Question 16

Possible conflicts: environmentalists?

Answer 16

They have mixed opinions - Norfolk contains some of UK’s most unspoilt coastline and much of area designated AONB so environmentalists want as little human interference as possible.

However where habitats are threatened by coastal retreat e.g. Birds nesting on cliffs, they may support improved protection.

Question 17

Sustainability: current hard engineering (e.g. Sea wall)?

Answer 17

• Not very.
• Provides some protection in present but high initial cost (£5000 per M) and on going costs of repair.
• Rising sea levels due to global warming means needs to be raised at further cost.
• Or is totally ineffective meaning relocation of people is only option.

Question 18

Sustainability: doing nothing?

Answer 18

Not sustainable as letting nature take its course will cause stress and financial loss to 1100 who live there
Local habitats may be threatened by salt water inundation which is significant as much of coast is AONB.

Question 19

Sustainability: managed retreat?

Answer 19

• May be sustainable
• The resultant lagoon/marshes would reduce erosion of the land behind by dissipating wave energy
• There would be some loss of human property/land especially in areas unprotected e.g. Trimingham
• Permanent changes to habitats within AONB.