Geography - Coasts

Question 1

What are the differences between constructive and destructive waves?

Answer 1

Constructive:
- strong swash
- long wavelength, short fetch
- builds the beach

Destructive:
- strong backwash
- short wavelength, long fetch
- erodes the beach, making it steeper

Question 2

Explain the different types of coastal erosion.

Answer 2

• Attrition - rocks smash against each other and become smaller, rounder and smoother.
• Abrasion - rocks are smashed against the cliff wearing it away.
• Solution - rocks are dissolved
• Hydraulic action - the power of the wave forces air and water into cracks making them bigger.

Question 3

What is the difference between discordant and concordant coastlines?

Answer 3

Concordant - when the geology (rocks) are arranged parallel to the coastline.

Discordant - when the geology (rocks) are at 90 degrees to the coastline.

Question 4

What 3 factors affect the power of a wave?

Answer 4

• Fetch (the distance which the wind has blown over the sea)
• Power of the wind
• Length of time the wind has been blowing for

Question 5

Describe the formation of a wave cut platform/notch.

Answer 5

1. The sea attacks/erodes the base of the cliff (hydaulic action and abrasion)
2. A wave cut notch is formed
3. As the notch increases in size, the cliff becomes unstable so collapses, meaning that the cliff face retreats
4. A wave cut platform is left behind where the cliff previously was
5. This process repeats and the cliff continues to retreat

Question 6

How are headlands and bays formed?

Answer 6

1. On a discordant coastline, the cliff is made up of different types of rock/geology.
2. The soft rock is less resistant so is eroded by the waves, creating bays. Bays are sheltered so material is often deposited by constructive waves, forming beaches.
3. The hard rock is more resistant so is eroded much less and therefore remains, forming headlands.

Question 7

Outline the steps of how a stump is created.

Answer 7

1. Waves attack/erode a cliff/headland, creating a crack in the rock
2. Hydraulic action widens the crack, forming a cave
3. Abrasion fully breaks through the cave, creating an arch
4. The arch continues to erode and is unsupported so collapses, leaving a stack
5. Waves weaken the bottom of the stack; it falls over, forming a stump

Question 8

Describe the process of longshore drift.

Answer 8

A wave approaches the beach in the direction of the prevailing wind, meaning that the wave’s swash carries material towards the beach at an angle. The backwash goes straight back to the sea (at a 90 degree angle to the beach) due to gravity. This causes material to be transported along the coastline.

Question 8

Describe the process of longshore drift.

Answer 8

A wave approaches the beach in the direction of the prevailing wind, meaning that the wave’s swash carries material towards the beach at an angle. The backwash goes straight back to the sea (at a 90 degree angle to the beach) due to gravity. This causes material to be transported along the coastline.

Question 9

Describe the formation of a spit.

Answer 9

Longshore drift carries material along the coastline, where the coastline changes direction deposition of material takes place forming a piece of land jutting out into the sea. When the wind changes direction, a hook can be made at the end of the spit. Behind a spit, the water is very sheltered as the waves cannot get past the spit so silts are often deposited, forming a salt marsh.

Question 10

What are the impacts of longshore drift on the coastline?

Answer 10

• Can destroy a beach by removing all the material from it
• Can change the shape of a beach
• Can create landforms such as spits
• Can make estuaries used as harbours too shallow because of deposited material

Question 11

Explain the factors affecting rate of landform change on two contrasting coastlines.

Answer 11

Holderness:
- Boulder clay is less resistant.
- Rock groyne stopped longshore drift and narrowed the beach.
- Sea wall and granite rip-rap at Withernsea to slow down erosion.
- The removal of sediment offshore has made the coastline more vulnerable
- Frequently subjected to powerful destructive waves from the North Sea.

Jurassic coastline:
- Discordant coastline created Swanage Bay and Headlands of Durlston and Ballard Point which have Old Harry’s stack.
- Concordant coastline has hard limestone parallel to coastline and in one place has punched through the outer layer and created Lulworth Cove from the less resistant clays and sands.
- Weight of buildings on cliff top e.g. The Grand Hotel in Swanage increase landslides.
- The construction of 19 timber groynes, restoration of the sea wall, beach replenishment with 160,000 tonnes, cliff regrading - reduced rate.

Question 12

What is cost/benefit analysis?

Answer 12

Weighing up the costs of protection against the benefits of protection.

Question 13

What are the two types of mass movement?

Answer 13

Rotational slumping - caused by water entering dry cracks in the cliff and saturates the soil so it becomes too heavy for the cliff and it slides down, quick movement of a lot of material

Soil creep - slow downhill movement of soil

Question 14

What is weathering and what are the 3 types?

Answer 14

Weathering - the breakdown of rock in-situ

Physical Weathering - water gets into cracks, freezes and expands over night widening cracks (freeze-thaw weathering) or rock heated during day, expands and at night cools and contracts - layers peel off (onion skin weathering)

Biological - roots get into cracks and as plant grows, roots expand widening the cracks.

Chemical - acidic rain reacts with alkaline rock e.g. limestone and breaks it down

Question 15

What are the different options for managing the coastline?

Answer 15

1. Hold the line: coastline held at present place by building or maintaining defences
2. Advance the line: build new defences to build up the coast into the sea
3. Retreat the line (managed retreat): allow the coastline to retreat by not maintaining defences or punching hole in defences
4. Do nothing: take no action including the maintenance or removal of defences.

Question 16

Using named examples, explain why some coastlines are protected and others are not.

Answer 16

Happisburgh - retreat the line due to:
- Cost of defences (sea wall, rip rap and groynes) - £6m
- Benefit of defences - £6m protected (Agricultural land worth £1m, 20-35 properties worth £4-7m, Grade 1 & 2 listed buildings, and a Caravan park)
- Defences would reduce sediment transport along the coast.
- Buy and demolish scheme would cost less than the defences.

Sea Palling - hold the line due to:
- Cost of defences (9 offshore reefs, 150,000 tonnes of rip rap, 1.4million m3 of sand) - £20m
- Benefit of defences - £345m e.g. Norfolk Broads National Park - £18m in biodiversity, £310m in recreation and £17 million providing drinking water
Will provide protection for all assets behind beach e.g. several sites of special scientific interest and 6000ha of farmland and other settlements.
- Recharge will help to supply sediment to other areas along the coast

Question 17

Give examples of hard and soft engineering options for coastal management.

Answer 17

Soft engineering: beach replenishment (where sand is placed on the beach), cliff regrading (where angle of cliff is reduced), managed retreat (where areas are allowed to flood)

Hard engineering: rip rap (large boulders placed on beach) recurved seawall (to absorb energy of waves), groynes (barriers at 90 degrees to stop longshore drift), offshore reef (causes waves to break out at sea)

Question 18

What are the advantages and disadvantages of hard and soft engineering?

Answer 18

Soft engineering:
+ cheap, easily available, fewer environmental impacts
- Doesn’t last very long, can be flimsy and ineffective, uses up land (managed retreat)

Hard engineering:
+ permanent, effective, reduces wave energy
- Expensive, ugly, needs constant maintenance

Question 19

What are the physical factors that increase vulnerability?

Answer 19

• Storm surges, tropical storms etc
• Narrowing of the land between Britain and Europe funnels water
• Low lying areas
• Climate change and sea level rise

Question 20

How do social and economic factors increase vulnerability?

Answer 20

• Areas of large % of people who have long-term health problem or disability means they will find it difficult to move.
• Low levels of educational achievement means they may not be aware
• Large proportion of the population who are elderly and do not want to move
• Low levels of income mean they are unable to afford to move
• Large population
• Low income countries who do not have the ability to defend themselves
• Location of key services e.g. hospitals, transport routes, water treatment plants, power plants.

Question 21

How do severe weather events and climate change increase vulnerability to coastal flooding in one named location?

Answer 21

London:
- Storm surges in the North Sea off the East coast of Britain being funnelled towards Thames estuary e.g. winter storms of 2013/14
- If this coincides with a high tide or spring tide sea level will be even higher
- Isostatic recovery - the South East is sinking by 1.5mm a year raising sea levels.
- Sea levels also rising due to climate change

Question 22

How can the risk of coastal flooding be reduced?

Answer 22

• Monitoring and forecasting extreme events e.g. Met Office and Environment agency
• Online hazard mapping - awareness of which areas are at risk
• Emergency planning - prepared with actions before, during and after can avoid loss of life
• Coastal defences

Question 23

Using named examples, explain why some coastal communities are at greater risk in the future than others.

Answer 23

Maldives:
- Over 1000 small islands
Most of the land is no more than 1m above sea level
- An increase in sea levels of up to 59cm by 2100 is predicted.
- Islands are at greater risk from the effects of hurricanes
- Is ranked 119th out of 228 in the world for GDP (LIC)

London:
- Whilst London is at risk it has the £535m (£1.6 billion in today’s money)
Thames Barrier completed in 1982
- It protects 1.25 million people, £200 billion worth of property, tube network, historic buildings, power supplies, hospitals and schools.
- It has been used just under 200 times.

Question 24

What will be the impacts of rising sea level in a named location?

Answer 24

Maldives:
- Most of the Maldives will be washed away in 30 years
- 3 of the 200 inhabited islands have already been evacuated
- As sea levels rise, the coral reef habitat which forms the islands, is being destroyed - fishing yields have halved and is the second biggest industry.
- Tourists will stop coming and over 90% of government income comes from tourist taxes.
- The 400,000 residents will be forced to leave
- Tidal surges flood homes regularly and cause salinisation preventing crops from growing.

Question 25

How are governments dealing with the problem of rising sea levels?

Answer 25

Maldives:
- Hulhumale reclaimed island from the sea - 2m above sea level
- The capital Male has a 3m sea wall surrounding the island
- Floating golf courses to enable tourism to continue
- Houses being built on stilts on the highest ground
- Plans to relocate the population to a new territory such as in Sri Lanka, India or Australia - environmental refugees

UK:
- The Thames Flood Barrier costing £535m, opened in 1982
- Increasing expectation that individuals and communities should help themselves to prepare