AQA A GCSE Revision: The Coastal Zone

PART A: THE COAST IS SHAPED BY WEATHERING, MASS MOVEMENT, EROSION, TRANSPORTATION AND

DEPOSITION

1. What are the different types of waves that

operate at the coast?

Destructive Waves operate in storm conditions and

are about 5 or 6 metres high. The SWASH is weak and

the BACKWASH is strong and there is A LOT OF

EROSION. The FREQUENCY is also high, which means

there are more hitting the beach in a minute than

constructive waves.

Constructive Waves operate in calm weather and are

about a metre high. The SWASH is strong and there is

weak BACKWASH as the water percolates through the

beach sediment. Erosion is LIMITED. They’re involved

with the TRANSPORT and DEPOSITION of material

creating depositional landforms (beaches, bars etc.).

2. What will determine how large a wave will be?

i. The fetch – how far the wave has come from

ii. How strong the wind is

iii. How long the wind has blown for

3. But how do the waves actually shape the coastline? This is due to EROSION, TRANSPORTATION & DEPOSITION.

Erosion is destructive waves wearing away the coastline. It happens when the waves are packed with energy. Erosion

can create landforms but eventually wear them away. The sea erodes the coast in four ways (these are the

PROCESSES OF EROSION)

I. HYDRAULIC ACTION/ POWER - water crashes against the cliffs/rocks, and the air and water is trapped and

compressed in cracks. When the sea moves away again the air expands explosively weakening the rocks,

enlarging the cracks and breaking pieces off.

II. ABRASION (sometimes known as CORRASION) - is very effective and is caused by broken rock fragments

battering the land, cliffs etc. and breaking off other pieces of rock. Operates like ‘sandpaper’.

III. ATTRITION - occurs when rock fragments collide into smaller and get worn down into smoother and smaller

pebbles.

IV. SOLUTION - involves chemical action of sea on rock. If the rock is limestone, it dissolves in the sea-water-

some sea salts can also react with certain rocks and cause them disintegrate.

4. Once the waves have eroded sediment how is it

transported?

Transport along the coast is when waves move material

across a beach. This is called LONGSHORE DRIFT.

Longshore drift happens when waves break at an OBLIQUE angle to the shore (not right angles) due to the

prevailing wind.

This means that each wave pushes

material along the beach a bit more.

(swash carries the material up the

beach at an angle and the backwash

drags the material down the beach at

right angles.)

Many depositional features such as

spits are formed by this process.

5. What other named processes of

transport are there?

6. What happens once the sea has finished transporting the sediment? DEPOSITION. This is the dumping of

eroded material on the land by constructive waves. It happens when the waves have less energy. Deposition

creates a variety of landforms, which are discussed later.

7. What other processes can shape the coastline?

WEATHERING! This is the breakdown of rock in situ (i.e. the stone doesn’t move). This

can happen due to Mechanical Weathering or Chemical Weathering:

Mechanical Weathering: includes freeze-thaw. Temperatures drop below freezing at

night and then rise during the day. As a result, any water in the cracks freezes and

expands and then thaws. Over time the expansion when the water turns to ice will

break the rocks apart.

Chemical Weathering: This includes solution. Water reacts with the calcium

carbonate in rocks like limestone and chalk. The rocks are dissolved and are washed

away.

8. What is ‘mass movement’?

The waves and the other processes discussed above can result in ‘mass movements’ on cliffs. There are two main

types:

Sliding – large chunks of rock slide down the slope

quickly without warning.

Slumping – common where cliffs are made of clay. The

clay becomes saturated during heavy rainfall and

oozes down towards the sea as part of a mud or debris

flow (more on this later in the Christchuch Bay case

study.

PART B: DISTINCTIVE LANDFORMS RESULT FROM DIFFERENT

PROCESSES

9. What are the landforms created by erosion?

WAVE-CUT PLATFORM - Waves erode rocks along the

shoreline by hydraulic action, abrasion and corrosion. A notch

is slowly formed at the high water mark which may develop into a cave. Rock above

the notch becomes unstable with nothing to support it, and it collapses. The

coastline (cliffs) can retreat over many years and a WAVE-CUT PLATFORM forms as

this process continues as only the base of the cliffs are left as the cliffs recedes.

HEADLANDS AND BAYS - If there are alternate bands of hard and softer rock in the

coastline, the harder rocks take longer to erode than the softer rocks- because the

sea has less effect. The hard rock will be left jutting out forming one or more

HEADLANDS, usually with cliffs. The softer rock will be eroded to form BAYS, the

erosion means the bays will usually slope more gently inland, creating room for a

BEACH TO FORM. Can you work out where the hard and soft rocks are found on this

map of the coast at Swanage in Dorset?

CAVES, ARCHES AND STACKS - A

crack in a headland can be eroded-

wave energy is usually strong there

because the headland juts out. This

forms one or more wave cut

notches/caves. Further erosion

enlarges the cave and it breaks

through the headland forming an

ARCH. The roof of the arch is often

unstable and eventually collapses

leaving a STACK or SERIES OF

STACKS. Areas with limestone or

chalk geology are prone to this kind

of erosion. MAKE SURE YOU REFER

TO ACTUAL NAMED PROCESSES

HERE.

10. What are the landforms of deposition?

BEACHES - Deposition forms BEACHES. Depositional landforms are most common on

lowland coasts, beaches are the most common depositional landform. Beaches are

accumulations of sand and shingle deposited by waves and currents. The sediment comes

from cliff erosion but most is brought down to the coast by rivers. They can be SWASH

ALIGNED or DRIFT ALIGNED:

Swash Aligned beaches are where waves approach parallel to the shore and break with swash moving directly up the beach and the backwash returning directly back. These form wide beaches

with an even shoreline. Ridges tend to form on beaches such as these called berms. Example: Chesil Beach, Dorset. Drift aligned beaches form when waves approach the beach at an angle resulting in a swash moving diagonally up the beach and the backwash returning through gravity. These movements create longshore drift (diagram on the previous page). These beaches have an uneven profile- especially when groynes have been used to slow the longshore drift. Example: West Wittering, West Sussex.

In terms of the shapes of the beach, the types of wave that have hit the beach will determine their profile. Look at

the start of this revision guide to see the different profiles. Sand beaches tend to be shallower than pebble beaches.

An example you

could use is

Durdle Door in

Dorset for an

arch

SPITS - Deposition also creates SPITS (East Head

Spit!!)

Spits are beaches joined to the coast at one end.

At their seaward end shingle ridges form a series of recurves or hooks.

Spits often develop across river mouths or where the direction of the coastline changes abruptly.

Spits form by a process called LONGSHORE DRIFT (referred to earlier)

Tucked away behind spits are quiet backwaters

that waves cannot reach, where tidal currents deposit fine silt and build up MUDFLATS and SALT MARSHES.

BARS - Deposition also creates BARS. Bars take spits one stage further

and actually extends further and join up to another headland. This is

able to happen due to the lack of a strong river current that would

wash the sediment away like in the tidal race of a spit. A good example

of this is Loe Bar in Cornwall or Slapton Sands in Devon (pictures left).

If a spit extends and joins up with an island then this is called a

TOMBOLO. The best example of this is Chesil Bach joining to the Isle of

Portland in Dorset.

PART C: RISING SEA LEVEL WILL HAVE IMPORTANT

CONSEQUENCES FOR PEOPLE LIVING IN THE COASTAL

ZONE

11. Why are sea levels rising?

The belief is that global warming is causing sea levels to

rise. The heat is causing the ice caps to melt, which is

releasing water into the oceans. In addition, the extra

heat can cause thermal expansion of the sea too,

making it higher. Estimates suggest that levels could rise

between 30 - 140cm by the end of this century.

12. What case study of a location at risk of sea level

rise could be used?

The Maldives, shown on the map on the right, is a

collection of very low-lying islands. The highest point is

only 2.4 metres above sea level. The beautiful landscape

and white sandy beaches has resulted in 30% of the

country’s GDP being created by tourism.

The table on the next page shows the various

consequences of coastal flooding on the Maldives.

Economic Social Environmental Political

Rising sea

levels could

end the tourist

industry

Traditional way of

life lost

Homes flooded

and land lost

‘Environmental

refugees’

Coral reefs will die as

the water gets deeper

The ecosystems

associated with reefs

will be lost

The whole country could

disappear!

Political tension between the

polluters and the Maldives – the

Maldives are suffering, but they

are not to blame for global

warming

PART D: COASTAL EROSION CAN LEAD TO CLIFF COLLAPSES. THIS CAUSES

PROBLEMS FOR PEOPLE AND THE ENVIRONMENT

13. What are the differences between ‘hard’ and ‘soft’ coastlines?

A hard coastline is one made from solid rock - e.g. chalk, limestone or granite.

These are resistant to erosion and produce steep vertical cliffs like those found

around Swanage, Lulworth Cove and Durdle Door (Isle of Purbeck). Soft rock

coastlines consist of clays, sands and gravels and therefore far less resistant to

erosion. Crucially, these are also affected by weathering processes and slope

processes. Sock rock coasts become unstable when wet as their structure is not

strong- slumping often results.

Hard rock cliffs will have a slow rate of recession and will tend to maintain a

vertical profile due to their strength. A wave cut notch can form at the base and

eventually, the rock above will fall, but the cliff will stay vertical.

Soft rock cliffs have a fast rate of recession as they are weak and are attacked

by the waves, but also by sub-aerial (weathering) processes.

At Barton-on-Sea in Hampshire, rates of cliff recession are about 1 metre a

year! Alomng the East coast of England, some places are losing 8-10 metres a

year.

14. What other factors can influence rates of cliff recession other than the physical factors?

People build in inappropriate places! They disregard the geology and build on soft rock cliffs. Often, people would

want to build as near to the cliff edge as possible to gain spectacular views. However, the extra pressure of building

such a large and heavy structure on the cliffs (especially if made from sands and clays) can increase the chances of

cliff collapse.

15. What case study can be used for cliff collapse?

Christchurch Bay – see

map on the left.

Look at the map and

work out why Barton-

on-Sea is susceptible to

coastal erosion.

Christchurch Bay is 16km long and parts are exposed to waves with a fetch of 3000km for the Atlantic. The area is

densely populated with a number of towns situated along it. Tourism is important to this area, so collapsing cliffs are

a major issue.

Why are the cliffs collapsing?

Marine processes: The base of the cliffs are being attacked by the

waves (hydraulic action and abrasion). The large fetch results in

powerful, destructive waves.

Sub-aerial processes: Weathering is weakening the rock and then

mass movements (slumping and rock fall) is leading to collapse

Geology: Permeable sand lies on top of impermeable clay. During

heavy rain the water collects above the impermeable clay and the

sand becomes too heavy and collapses. The diagram on the right

explains this.

Human activity: Extensive building along the cliff top has

resulted in too much weight on the soft cliffs and this has

promoted collapse.

On the previous page I have circled a large groyne that was built

in 1938 to protect Hengistbury Head. Unfortunately, this has

prevented sediment from reaching the beaches along

Christchurch Bay, which has promoted further erosion.

What are the impacts of cliff collapse at Barton-on-Sea?

Social Economic Environmental

Loss of homes

House values go down –

people can’t move

House insurance very

expensive

Dangerous to walk on the

cliff tops

Roads under threat

Tourists may not visit

(coastal protection works

look ugly?) Dangerous? This

impacts on local businesses

(taxis, cafes, hotels etc.)

Cliff collapse looks unattractive

Cliff collapse exposes different rocks and

fossils – interesting to scientific

community. For example, the cliffs at

Naish Farm holiday village are being

allowed to erode for this reason as they are

a Site of Special Scientific Interest (SSI)

They have managed the cliffs at Barton-on-Sea, but they still continue to recede.

PART E: THERE IS DISCUSSION ABOUT HOW THE COAST SHOULD BE MANAGED. THERE IS DEBATE ABOUT THE

COSTS AND BENEFITS OF ‘HARD’ AND ‘SOFT’ ENGINEERING

16. Who manages the coast?

DEFRA (Department for Environment, Food and Rural Affairs) is the government department responsible for coastal

defence. The Environment Agency and local councils decide on how best to spend the money and protect the

coastline.

17. How is the coastline actually managed?

I don’t mean the actually methods employed like sea wall etc. What I mean is the general decisions about where to

protect (or not) and roughly what types of measures should be employed. As was discussed in Q16 above, local

councils and government work together and they formulate a plan

called a ‘Shoreline Management Plan’ or ‘SMP’.

Each SMP (an example is shown on the right) may propose

management of the sub-cell in a number of ways:

Hold the line - maintain the existing coastline by building

defences

Advance the line - build new defences seaward of the

existing defences

Managed retreat - allow the land to flood, and construct a

new line of defences landward of the existing coastline

Do nothing - allow natural processes to shape the land

18. How are coastlines actually protected?

Planners can use ‘hard’ strategies or ‘soft’

strategies.

Hard management: physical structures

constructed to stop erosion by the waves.

Soft management: working with nature

rather than against it. For example, beach

nourishment – no physical structures built.

19. What hard management strategies are used?

The diagrams below show the main options

employed. You need to know about sea walls,

groynes and rock armour.

20. How do these strategies work?

The table on the next page summarises the

information about the various hard strategies.

21. Hard strategies are very effective; surely everyone is in favour of them?

Not so! Examine the table below.

In favour Not in favour

Local people with homes in

danger

Local tourist businesses with

caravans and hotels at risk (but if

the structures are ugly will that

not scare tourists away?!)

Local taxpayers who don’t live next to the coast (why should they pay?!)

Environmentalists – fear that habitats and natural beauty will be

affected

People living downdrift of the defences could be starved of sediment

(like the people at Barton when the 1938 groyne was built at

Hengistbury Head) and lose their beach

22. What soft management strategies

are used?

Soft management has become more

popular over the years and many

people now feel that this approach is

more sustainable and a more effective

way of managing the coast.

Soft management tends to be less

expensive, will last longer and is more

environmentally friendly than hard

management methods.

The table on the right discusses these

approaches further.

A CASE STUDY OF HARD AND SOFT

MANAGEMENT IS WEST WITTERING BEACH AND EAST HEAD SPIT – THIS CAN BE USED FOR THIS PART OF THE

SPECIFICATION, BUT ALSO THE FINAL PART DISCUSSED ON THE NEXT PAGE. THE MEDMERRY MANAGED RETREAT

SCHEME SHOULD ALSO BE REVISED TOO.

PART F: COASTAL AREAS PROVIDE A UNIQUE ENVIRONMENT AND HABITAT. THERE IS NEED FOR CONSERVATION

AND THIS LEADS TO CONFLICT WITH OTHER LAND USES

23. A case study of a coastal habitat (also use for hard and soft management!!)

East Head

Sea defences have interrupted the

natural coastal processes in the area

for the last 200 years

In the 1960s and 1970s the narrow

beach at the Hinge was breached

during high tides/ severe storms and

this was again threatened in 2004.

This was deemed to be unacceptable as

this would change currents at the

entrance of Chichester Harbour. The

cost of which would be hard to imagine

as the sailing industry in the area is

worth millions of pounds

In 2005 a rock berm was placed at the

Hinge. Gabion cages and wooden

groynes have also been employed.

There are even the remains of a wave

revetment at ‘The Hinge’ of the spit.

(HARD MANAGEMENT)

In 2005 and again in 2009, huge

amounts of sand (15,000 cubic metres)

was taken from the northern end of

the spit and placed at the narrow point

of the spit. (SOFT MANAGEMENT)

Marram grass was planted to stabilise

the feature. Psychological barriers were

also constructed to encourage people

not to go on the newly created sand

dunes. (SOFT MANAGEMENT)

Similar barriers were also used to rope

off the breeding area for the Ringed

Plovers and also the Silver Spiny Digger

Wasp. (SOFT MANAGEMENT)

Conflict at East Head

The sand dunes are fragile and don’t react well to humans!

Too many tourists can bring litter and fire hazards

East Head is a habitat for many rare species – i.e. The Digger

Wasps and Ringed Plover

The beach can become very crowded

Visitors need somewhere to park, plus other facilities like

toilets and paths

Coastal erosion

Solutions at East Head

Marram grass planted

Dunes fenced off to prevent trampling

Shop and café placed far away from the spit and bins provided

Boardwalks used on the spit to prevent trampling

Information signs educate people about the environment

Area roped off for the Digger Wasps

Area roped off for the Ringed Plover

Car parking charges helped fund the protection of the beach

and spit

Groynes

Gabions

Toilets provided

Beach recycling (2005 and 2008)

Rock armour/ rip rap (2004)

ALL THESE THINGS ARE DESIGNED TO MAKE USE OF EAST

HEAD SUSTAINABLE

You probably have an annotated

map in your books with this

information?

24. An example of managed retreat – Medmerry

Scheme, West Sussex.

East Head is just to the NW of Medmerry.

Medmerry Managed Retreat near Selsey

Low land near Selsey under constant threat. Low value farmland – why bother protecting this?

Decision made to punch a hole in the defences and build an earth wall inland. The sea flooded the land and a salt marsh has been created. Great for wildlife!

Increased flood protection for 300 homes, the sewage treatment works and the main road into Selsey.

Finished November 2013

10km of paths created

£28 million cost

Other useful sites:

http://www.s-cool.co.uk/gcse/geography/coasts

http://www.bbc.co.uk/schools/gcsebitesize/geography/coasts/