1  

Canon Slade School

Geography Department

Unit 1 – Physical Geography

Q7. The Coastal Zone

 

  2  

Topic Summary A: Coastal processes and landforms

B: Coastal management  

   

 

Need for management coastal erosion and crumbling cliffs

threats from rising sea levels many coastal human activities

maintenance and improvement of sea defences

Hard engineering strategies sea walls groynes

rock armour

Soft engineering strategies beach nourishment dune regeneration

marsh creation

Do nothing leave to nature

allow sea to invade

Costs and benefits of these strategies Towards a more sustainable use of coastal areas

Processes at work changing the coastal zone

Weathering and mass movement

Breakdown of rocks by chemical and mechanical weathering

Mass movement of cliffs by sliding and

slumping

Deposition Factors favouring

deposition large load

sheltered water bend in coastline

Wave erosion Processes of erosion

hydraulic power abrasion attrition solution

Transportation Longshore drift Processes of transportation

traction saltation

suspension solution

Landforms of erosion appearance (description)

formation named example

Landforms of deposition appearance (description)

formation named example

How to recognise coastal landforms on OS maps

  3  

Checklist for revision Understan

d and know

Need more revision

Do not understand

I know the difference between wave erosion, weathering and mass movement.

I can state and explain the differences between destructive and constructive waves.

I can describe how sand and shingle are transported along the coast of the UK.

I can recognise and explain the formation of cliffs, wave cut platforms, headlands, bays, caves, arches and stacks.

I can recognise and explain the formation of spits and bars.

I understand where and why beaches form.

I can give examples of hard and soft methods of engineering for coastal protection and state the differences between them.

I can explain why thermal expansion and melting land based ice cause sea levels to rise.

I know what managed retreat of the coastline means, and I understand why it is becoming preferred government policy along rural sections of coast.

Case studies

A: Cliff collapse

I know the causes (physical and human) and can give the impacts on people.

B: Coastal flooding

I know the economic, social, political and environmental impacts of flooding.

C: Coastal management

I can explain why it is needed, describe the methods used and know the costs and benefits.

D: Coastal habitat

I can describe the natural environment and strategies for conservation, allowing sustainable uses by people.

  4  

Important coastal processes

Process Definition

Sub

aeri

al p

roce

sses

Mechanical weathering breakdown of rock without any change in its chemical composition; free–thaw is an example

Chemical weathering breakdown of rock in the place where it lies by chemical processes

Sliding (mass movement) large amounts of rock and soil move smoothly downslope

Slumping (mass movement) soil and vegetation move downslope in blocks, leaving curved scars where they have moved from

Eros

ion

proc

esse

s

Abrasion coastline eroded by waves bashing pebbles against cliffs

Hydraulic Power coastline eroded by the force of water hitting the coast

Attrition particles carried in the waves are reduced in size as they collide with one another and rock faces

Solution (erosion) chemical action on rocks by sea water dissolves rocks like chalk and limestone, making them easier to carry away

Tran

spor

t pr

oces

ses

Traction large boulders are rolled along the sea floor by the waves

Saltation small boulders are bounced along the sea floor by the waves

Suspension sand grains are carried along in the water Solution (transport) dissolved limestone rocks are carried away

in the water

Wav

es

Constructive waves (deposition) 6–9 per minute, small waves with a stronger swash

Destructive waves (erosion) 12–15 per minute, large waves with a strong backwash

Longshore drift movement of waves along the coast transporting sediment. Waves approach at an angle (swash) and retreat perpendicular to the beach (backwash).

Swash Waves moving up the beach Backwash Waves moving down the beach

  5  

Case Studies Case Study of cliff collapse: Holderness Coast, NE England Reasons why the cliffs are vulnerable: • The cliffs are made of boulder clay. Boulder clay crumbles when it is saturated. • There are naturally narrow beaches along the coast so there is little protection for

the cliffs from the sea. • The waves that erode the Holderness coast have travelled long distances so they can

be quite powerful. • People have built groynes near places such as Mappleton. This is slowed the transport

of sediment down the coast making beaches narrower. Impacts of cliff collapse on people’s lives at Holderness: • Homes near the cliffs (e.g. in Skipsea) are at risk of collapsing into the sea. • Businesses are at risk from erosion so people will lose their jobs e.g. Seaside Caravan Park at

Ulrome is losing an average of 10 pitches a year. • Local councils will have to raise taxes in order to pay for more coastal management strategies. • Property prices along the coast have fallen sharply for those houses at risk from erosion. • Accessibility to some settlements has been affected because roads near cliff tops are at risk

of collapsing into the sea e.g. Southfield Lane which runs between Skipsea and Ulrome has been closed.

• The gas terminal at Easington is at risk (its only 25m from the cliff edge). This terminal accounts for 25% of Britain’s gas supply.

Impacts of cliff collapse on the environment: • Some sites of special scientific interest (SSSIs) are threatened e.g. The Lagoons near

Easington are separated from the sea by a bar. If the bar was eroded away, the Lagoons would be destroyed.

• 80,000 m2 of farmland is lost each year. This has a huge effect on farmer’s livelihoods.

  6  

Hard and soft management at the coast Hard engineering – building artificial structures aimed at controlling natural processes. Strategy Description Financial

Cost Benefits Costs

Sea wall

Concrete or rock barrier placed at the foot of cliffs. Reflects the waves back into the sea.

Up to £6 million per km

Effective at stopping the sea, and often, the top can be a walkway or promenade.

Can be obtrusive and unnatural to look at. Very expensive and high maintenance costs.

Groynes Timber or rock structures that are built at right angles to the beach. They trap longshore drift and enlarge the beach.

£10,000 each (at 200m intervals).

Results in a bigger beach, which enhances tourist potential. Provides useful structures for people interested in fishing. Not too expensive.

Starves longshore drift downdrift which leads to erosion elsewhere. They are unnatural and can be obtrusive. Wood can rot too.

Rock armour

Piles of large boulders dumped at the foot of cliffs. They absorb the force of the waves.

Approx. £4,000 per metre

Relatively cheap, easy to maintain and provides interest to the coast (e.g. used for fishing)

Rocks are usually brought from other coastlines. Expensive to transport and they sometimes do not fit in with the local geology. Obtrusive.

Soft engineering – a sustainable approach to management without using artificial structures. Description Benefits Costs

Beach nourishment

Sand and shingle from elsewhere (e.g. offshore sea bed) is added to beaches

Provides wider beaches which slow waves. This gives greater protection from flooding and erosion.

Taking material from the sea bed can kills organisms like corals. It’s very expensive and it has to be repeated.

Marsh creation

Planting vegetation in mudflats/ salt marshes along the coast (usually because of managed retreat).

The vegetation stabilises the mudflats and helps reduce the speed of the waves, preventing flooding and erosion. It also creates new homes for organisms.

It isn’t useful where erosion rates are high because the marsh cannot establish itself.

Dune management

Creating or restoring sand dunes by either nourishment, or by planting vegetation to stabilise sand.

Sand dunes provide a barrier between the land and the sea. Wave energy is absorbed which prevents flooding and

The protection is limited to a small area. Very time consuming to

  7  

erosion. Stabilisation is cheap.

plant vegetation. Nourishment is very expensive.

Managed retreat

Allowing low-lying, low- value coastal areas to be flooded by the sea. This involves removing existing sea defences.

This is a cheap option compared with maintaining expensive sea defences. Creates much- needed habitat for wildlife.

Farmers or landowners have to be compensated. Land is lost as it is flooded by the sea. Debate as to what land to let flood.

Case Study of Coastal Management: Holderness Coast, NE England Holderness is a 61km stretch of coastline. So far, only 11.4km of coastline has been protected.

PLACE EXISTING COASTAL DEFENCES

Bridlington (pop. 31,000) Fishing port and holiday resort with bathing beaches of EU quality standard.

• Sheltered naturally by Flamborough Head

• Protected from erosion and flooding by a 4.7km long sea wall as well as groynes.

Hornsea (pop. 7,500) Holiday resort with bathing beach of EU quality standard.

• Wooden groynes, and concrete sea wall. Built in early 1900s and repaired in 1980s.

Mappleton (pop. 100) Small village (on the B1242 coast road) in a farming area.

• Two rock groynes built in 1991 at a cost of £2m.

Withernsea (pop. 6,300) Holiday resort with bathing beach of EU quality standard.

• Wooden Groynes built in late 19th century.

• New sea wall with rock armour built in 1980s and replaced in 1992.

Spurn Head Sand and shingle spit with a lifeboat station, the Humber Pilots base and a nature reserve. It has Heritage Coast status.

• Rock armour and wooden groynes (now derelict) on eastern side.

• This also protects the Humber estuary behind Spurn Head.

  8  

Case Study of Coastal Management: Managed Retreat at Wallasea Island, Essex. Wallasea Island is a low – lying coastal island formed at the confluence of the river Crouch and Roach in Essex. It was until recently used for growing wheat.

Case Study of Coastal Flooding: How will sea level rise affect the Maldives? Facts about the Maldives

The Maldives are a group of over 1000 islands made from coral (limestone) in the Indian Ocean. About 300,000 people live in the Maldives. The Maldives are the world’s lowest country. On average, each island is 1.5m above sea level. 80% of the land is below 1m. Because of rising sea levels, scientists think that the islands will be completely submerged by 2100. Social Impacts

The whole population

may have to abandon the

islands by 2100.

The sea rises up through

the permeable limestone.

This results in people’s

homes being eroded

away.

Political Impacts

The government has had

to build sea walls so that

the capital Male is

protected from flooding.

Money has been

borrowed from Japan to

pay for this.

The Maldives are

campaigning for other

countries to become

Environmental Impacts

Rising sea levels create

more destructive waves

resulting in more erosion

of the islands.

Seawater will

contaminate the

freshwater in the soil

which means that plants

will not be able to grow.

Economic Impacts

The main airport in Male

will be flooded. This will

reduce tourism in the

islands.

Coastal flooding may

damage fish processing

plants. This will affect

the Maldives main

industry.

Main features: • Cost of £7.5 million • Main aim is to replace bird habitats lost to

development. • Will also improve flood defences on the

island and reduce risk in areas such as Burnham-on- Crouch.

• New leisure opportunities will be created. • Mainly achieved through allowing the old sea

wall to be breached in July 2006. • This will allow the area to revert to a salt

marsh, providing a much needed habitat for birds.

  9  

carbon neutral so that

the amount of carbon

dioxide emitted into the

atmosphere is reduced.

Rising sea levels mean

that there is little land

for future development

so the government is

thinking about buying

land in India and

Australia and moving

people there.

Land is being reclaimed

from the sea so that

more homes can be built.

This involves dredging

sand from the seabed

which can affect corals

and other ecosystems.

There will be less

freshwater for people so

the government will have

to build desalinisation

tanks which are

expensive.

Case Study of a coastal habitat: Keyhaven Salt Marshes, Hampshire. Vegetation Succession along Keyhaven Marshes

• Keyhaven Marsh is an area of salt marsh located behind (the lee side of) Hurst Castle Spit in

Hampshire (the south of England). • Salt marshes are areas of periodically flooded low-lying coastal wetlands that usually form in

the sheltered areas (lee) behind spits. • They are usually rich in plants, birds and animals and are very important coastal habitats.

Tidal

inlet (mudflat)

Low Marsh High Marsh Marsh uplands

  10  

Environmental characteristics of Keyhaven Marshes • Tidal Flat - this area is mainly flooded by the sea. There is lots of deposition here of fine silt

and mud so there area is mainly a mudflat. There is very little vegetation that can grow here. However, the oystercatcher feeds here.

• Low Marsh – here, the area is flooded by the high tide. The area is periodically flooded so the

only vegetation that can grow here is cordgrass which is salt tolerant and has long roots to stabilise itself in the soil/ mud. This is a pioneer species (the first plant in the succession). The wold spider clings for hours on the cordgrass by clinging on and holding its breath for 4 – 6 hours.

• High Marsh – the soil in this area is more fertile so plants such sea lavender and sea asters

grow here. Butterflies (such as the blue butterfly) are attracted to these plants (which help pollenate other plants) and the ringed plover nests here before feeding intertidally on the mud flats. There is less salinity here in the soil due to less seawater flooding.

• Marsh Uplands – here, the soil is very fertile due to rainwater washing out excess salt and

decaying vegetation adding many nutrients to the soil. Lots of vegetation is able to grow here such as oak trees and shrubs.

Threats to the marshes: • Tourists trample the grass and disturb wildlife habitats • Decline in the number of bird species like wading birds • Dropping litter, dropping cigarettes which can cause small fires • Tourists trample the grass which can also cause erosion to the mudflats • Hurst Castle spit was breached in 1989, exposing 50-80m of the marsh to the sea.

Management Strategies and why they are sustainable

• Build boardwalks - These are raised walkways guide people across the marsh so the grass can grow below them and be protected and not get damaged.

• Fence off some of the vegetation and plant species of grass (e.g. cordgrass or marram grass) - This gives the vegetation chance to recover and the grass will stabilise the mudflats

• Information signs put up to inform visitors that Keyhaven Marshes is an important habitat - Educates tourists: shows them how to manage their waste responsibly and tourists can learn about the species and habitats, which shows them why the marsh is important.

• £5 million of Rock armour and beach nourishment in 1996 - This increased the height and

the width of the spit and has not been breached since. • Made into a SSSI (Site of Special Scientific Interest) and part of it is also a National

Nature Reserve managed by Hampshire county council - This means the species are fully monitored and managed to maintain a rich biodiversity.