Paper 1 Section C Coastal erosion, deposition and management

Question 1

What is coastal erosion?

Answer 1

Erosion means wearing away the land. Coastal erosion means the sea causes this

1. Corrasion - waves fling material at the cliff and pieces fall off
2. Abrasion - pebbles wear away the rock they come into contact with - sandpaper effect
3. Hydraulic action - waves get into cracks in the rock, create pressure and as the wave falls back the pressure is released taking small bits of rock with it (makes the crack bigger)
4. Attrition - material in the sea bashes against eac other making pebbles smaller and more rounded
5. Solution (or Corrosion) - acid/salt in the water wears away the rock eg limestone

Question 2

How is material transported?

Answer 2

1. Traction - rolling heavy material
2. Saltation - water bounces the material along the bed
3. Suspension - light materila floating in the water
4. Solution - material dissolved in the water

Question 3

Whay is material deposited?

Answer 3

Deposition happens when the material is too heavy for the water to carry; when the water slows down

Question 4

What is longshore drift? Can you draw THE diagram accurately?

Answer 4

Longshore drift is the movement of material along the coastline. It depends on the direction of the prevailing wind.
Material is carried up the beach (swash) at the angle of the prevailing wind but returns to the sea (backwash) at right angles. Material therefore moves in a zig-zag pattern.

Question 5

Name at least 6 features of coastal erosion you might sea at the coastline
What causes different coastal features?

Answer 5

1. Headlands and bays
2. Caves, arches, stacks and stumps
3. Cliffs and wavecut platforms
   Coastal features depend on the rock type - resistant or weaker rocks.

Question 6

How are headlands and bays formed?

Answer 6

More resistant rock is separated by weaker rock.
The waves erode the weaker rock by hydraulic action and abrasion further inland than the more resistant rock
Deposition of the material forms the beach
(Aerial diagram)
Bays are sheltered areas - popular with tourists
The headlands may have caves, arches etc

Question 7

How are caves, arches, stacks and stumps formed?

Answer 7

Learn the diagram!
Cracks (lines of weakness - joints and bedding planes) in the rock on a headland are widened by hydraulic action and abrasion
A crack forms a cave which is further eroded by HA into the headland
Another cave may also have formed on the other side of the headland. When these are back to back the wall between the 2 will collapse causing a sea arch.
Further abrasion and HA as well as weathering (eg freeze- thaw, rain) on top of the arch make the roof collapse to form a stack
HA and abrasion cause the stack to become smaller. The stump may be covered at high tide.

Question 8

How are wavecut platforms formed?

Answer 8

Lines of weakness are widened by waves at high tide. HA causes a wavecut notch to be formed which erodes deeper into the cliff.
As nothing is then supporting the rock above the cliff will collaspe.
The sea will remove some of the material but the solid rock base remains which shows the extent of the erosion of the cliff.
The wavecut platform will be covered at high tide. Often a lighthouse marks where rocks are just below the surface of the sea.

Question 9

What features are formed by coastal deposition?

Answer 9

Beaches
Sand dunes and
spits are caused by deposition

Question 10

How are beaches formed?

Answer 10

Beaches are built up from deposits of sand
Created by constructive waves
Pebble beaches form where the waves are strong and wash away the sand. Pebble beaches are also called shingle beaches and are steeper than sandy ones.
What shape are the pebbles?

Question 11

How are sand dunes formed?

Answer 11

See diagram
Small hills (embryo dunes) of sand are formed round obstacles eg rocks.
These remain in place and vegetation (eg marram grass) grows making them more stable
Decomposing vegetation makes the sand more fertile
Ponds may develop in the shallow hollows (slacks) between the dunes

Question 12

Explain the formation of a coastal spit (or bar)

Answer 12

1. LOngshore drift moves sand along the beach in the directionof the prevailing wind
2. The coastline suddenly changes direction but LD continues (out into the sea)
3. Material is deposited in the sea to create a bank of sand
4. Occasionally the wind direction changes and a hook is formed at the end of the spit as the change of direction causes the sand to move in a different direction (a recurved end)
5. When the prevailing wind returns the spit will continue to ‘grow’. Sand dunes oftern form and the spit is used for tourism. Lifeboat stations are often at the end of the spit. Hurst Castle spit had a wartime look out post which was converted to a prison. Groynes are often used to reduce LD along the spit
6. A saltmarsh is created behind the spit where the water is shallow and sheltered. If there is a river mud deposits (mudflats) will build up
7. A ‘bar’ is a spit which joins land to land (eg across a bay)

Question 13

Name real examples of coastal features

Answer 13

The Dorset coastline on the south coast of the UK has:
Old Harry Rocks (Stacks and stumps)
Durdle Dor is a sea arch at Lyme Regis in Dorset
Swanage Bay is between Ballard Point (Headland) and Peveril point (headland)
There is a spit at Poole Harbour but we have used Hurst Castle Spit

Question 14

OS MAPWORK

Answer 14

Practice labelling and identifying features using 4 and 6 fig grid references. Page 65 of your revision guide

Question 15

What is hard engineering?

Name 4 examples and how they work

Answer 15

Hard engineering is the use of solid materials to manage coastal erosion

1. A curved sea wall - built of concrete and curved to reflect the enegry of the waves back to sea as they hit the wall. They also act as a barrier against flooding.
2. Revetments - can be sloping or stepped (Blackpool). These break the force of the waves and allow the water to return to the sea without eroding the land.
3. Rip rap/rock armour is large boulders placed at the base of the coastline/cliff. They have gaps between them and allow the waves to break on to them, absorbing the energy, and return through the gaps back to the sea.
4. Gabion crates are rock filled ‘baskets’. these are piled on top of each other and work like rip rap. They also protect the cliff behind (usually soft rock). Vegetation can grow on them and make them look more natural.
5. Grounes are used to protect the beach from longshore drift and hold sand in place. They also allow waves to break on to them, absorbing the energy. Buils at right angles to the coastline.

Question 16

What is soft engineering?

Give 3 examples

Answer 16

This is the use of cheaper materials to protect the coastline. They often blend into the coastline too and are more sustainable. However they need more maintenance.

1. Beach renourishment - sand and shingle is dredged fromthe sea bed and sprayed back onto the beach by ship. eg Eastbourne, East Sussex
2. Beach reprofiling - the beach is reshaped to create wider shelves and steeper slopes. The waves can break against the slopes and water sink through the wider areas.
3. Dune regeneration - marram grass is planted to stabilise the dunes and help them develop. Fences keep people away fromnewly planted areas. They also protect existing dunes. eg West Sussex

Question 17

What are the advantages and disadvantages of coastal management schemes?

Answer 17

Seawalls
Advs: effective at stopping the sea
Disad: Look unnatural; very expensive to build and maintain
Revetments - effective at breaking wave energy
But also expensive and may look unnatural.
Rip-rap - cheaper option and easy to maintain. Provide interest at coast
But rocks need to be brought to area and therefore not natural in their surroundings, expensive to transport.
Gabions: Cheap, improve cliff drainage and do eventually merge with landscape.
But unattractive initially and rust over time - need to be replaced.
Nourishment - Cheap, easy to maintain, blends in with surroundings and creates bigger beaches (tourism)
BUt needs constant maintenance
Reprofiling: As above
Dune regen: natural environment, good for wildlife. Cheap. But time consumin to plant and construct. Can be damaged by storms
Fencing needs regular maintenance.

Question 18

What is managed retreat?

Answer 18

This is the partial flooding of the coastline where land is of low-value by the sea.
KNOW THE DIAGRAM
Land used to be protected by a sea wall which has now broken.
Rather than rebuild it managed retreat was used.
An earth bund was built and trees planted on it to stabilise it.
The land as flooded in front of it.
Over time a nature reserve has been developed with bird watching facilities.

Question 19

Assess the impact of managed retreat (also known as coastal realignment) at Medmerry Wetlands

Answer 19

Medmerry is near Chichester in S Eng
Flat-low-lying land, mainly used for farming and caravan parks - low value land.
Area was protected by a low sea wall that was breached (ie the sea came over it)
2013 an earth bund (natural embankment) was ‘built’ and the land was flooded
Cost £28m
Now created a natural saltmarsh which absorbs the additional water and any wave energy
Protects the surrounding coastland and caravan parks in the area
A wildlife habitat/nature reserve has been created which attracts local people and tourists.
Roads, settlements and other farmalnd protected by the earth bund.

Question 20

Using an area you have studied analyse the need for coastal management and its effectiveness

Answer 20

USE YOUR FIELDWORK!
Blackpool, NW Eng
What were the issues?
Old sea defences that hadn’t been upgraded and were allowing the coastal area to be flooded.
Storms and powerful waves causing much damage to the coastline and buildings behind putting at risk many commercial properties
Blackpool is the most popular seaside resort in the UK therefore bringing many financial and economic advantages to the area

Type of managment is hard engineering
Curved sea wall, revetment (stepped down to the sea to encourage tourists to sit)
Flat grassland behing the sea wall and before the tramlines and road to protect from flooding and absorb any sea water
Cost over £70million

How effective do you think they have been? Think about the results for your fieldwork - what did most people say? What did the coastguard say? What do the sea defences look like? Do they add charachter to the area? Do they attract tourists to interact with them?