3a. the coastal zone.ppt

8/10/2019 3a. The Coastal Zone.ppt

http://slidepdf.com/reader/full/3a-the-coastal-zoneppt 1/140



There are two types of waves



Waves as strong as these only

occur in severe storms. Theycan cause terrific damage to

coastal settlements as well as

causing a lot of erosion.



Constructive waves lead to

the formation of beaches.

Beaches are the most

common feature of

deposition.



What processes shape

our coastline?



What

processes

shape thecoastal

zone?

Weathering

processes

Mass

movement

Coastal

processes



Weathering

processes

Weathering is the

disintegration of rocks in

their original place

Freeze-thaw is particularly

effective in the coastal zone

if the rock exposed is

porous and / or permeable.



The rocks are broken down ‘in situ’,

which means that no movement is

involved, unlike erosion which is caused

by the movement of water, wind and ice.



Rock fall - Beachy Head, East Sussex, 12/1/99

During an exceptionally wet

period the chalk rock became

saturated with water. Longperiods of frost weakened the

rock leading to several dramatic

rockfalls along the south coast of

England.



Mass Movement

Mass movement is the

downhill movement of

material under the

influence of gravity



Both mass movement and

weathering provide an input of

material to the coastal system.

Much of this material is carried by

the waves to be deposited

elsewhere along the coast.



Hydraulic Action

Abrasion

Solution

Attrition

When waves throw beach

material at the cliff

When eroded material is

broken down into smaller pieces

Pressure from air trapped in crackscauses rocks to break

Limestone & chalk react with the sea

which is a weak acid.



What processes are at work to create this landscape?

Abrasion

AttritionHydraulic action

Solution

Freeze-thawweathering

Solution Biological

weathering



Headlands

and Bays



Cliff d



Cliffs and wave

cut platforms



The waves attack the base of the cliff through the processes

of hydraulic action, abrasion, and solution.

Over time the cliff will be undercut and a wave-cut notch is

formed.

Eventually the cliff becomes unstable and collapses. Further

cliff retreat will leave a rocky wave-cut platform.

Wave-cut platform



Wave cut platform



Wave cut platform

cliffs



Caves, arches and stacks



Marsden Rock in 1984



Marsden Rock



Coastal Erosion



Europe’s fastest eroding coastline



Flamborough Head

Boulder clay

Hull

Spurn Point

Former

coastline

Europe s fastest eroding coastline

North Sea

R.Humber



HeadlandCliff

Arch

Wave cut platform

Stump



Crumbling

boulder

clay cliffs

Rotational

slump

Spurn Point



North Sea

River Humber

Spurn Point



C t l P TRANSPORTATION



This movement of sediment along thecoastline is called longshore drift.

Direction of movement

swash

backwash

Backwash is always at

r ight angles to the beach

Coastal Processes - TRANSPORTATION



Beaches Spits Bars

B h



Beaches

Beaches are accumulations

of sand and shingle foundwhere deposition occurs

along the coast.

Sandy beaches are often

found in sheltered bays,

where they are called

bay head beaches

Pebble beaches tend to form where



Pebble beaches tend to form where

cliffs are being eroded and where

there are high energy waves.

BERM



As constructive waves build up beaches, they often formridges in the beach known as BERMS. The berm highest up

the beach represents the extent to which the water has

reached during high tide.

BERM



Hull

R.Hu

The ormation of Spurn Point

Erosion of the coastline

north of Spurn Point

Eroded material transportedby sea currents

Material dropped

where coastline

changes direction

Spit grows out

from coast as

more material

builds up.

End of spit curved

by action of the

waves

Former coastline

HULL

RIVER

HUMBER

A bar



Occasionally, longshore drift may cause a spit to grow right

across a bay, trapping a freshwater lake or lagoon behind it.

This feature is called a BAR. E.g. at Slapton Ley in Devon



Example:

The East Coast of Yorkshire

- The Holderness Coast

C fMost cliff collapse occurs



Causes of

cliff collapse

The cliffs along the

Holderness coastline are

made of boulder clay.

Apart from wave erosion,

weathering processes also

contribute to cliff

collapse.

during or after prolonged

heavy rain when water

seeps into the land surface.

It saturates the clay and

makes it heavy. The added

weight causes the clay to

move.

This causes landslides and

slumping to take place

along a slide surface.

Case study: The Holderness Coast of East Yorkshire



Case study: The Holderness Coast of East Yorkshire

•

• •

•

•



Barmston

Mappleton



Mappleton

G F C d



Grange Farm, Cowden



Easington gas terminal



Easington gas terminal

Economic effects Social effects



Effects of the cliff

collapse along the

Holderness Coast

Environmental effects Political effects

Economic effects Social effects



Environmental effects Political effects

• Market value of properties

has fallen. Houses can’t be

sold.

• Properties can’t be insured.

• No compensation available so

people lose everything.

• Loss of land and crops = loss

of farmers income

• People lose homes, may have

to move into council houses.

•

Ill health is rising – erosionrelated stress, sleeplessness

and depression

• Loss of land

•

Unsightly collapsed buildings

• Debris from houses on the

beach.

• Decisions made about which

communities are worth

protecting.

• Cost of sea defences

• Protests from angry residents

Effects of the cliff

collapse along

the HoldernessCoast

Describe the costs and benefits of two Soft methods of coastal

management (4)



management. (4)

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________ _______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

Describe the costs and benefits of two Hard methods of coastal

management. (4)

_______________________________________________________________ _______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________



Managed



Managed

retreat

Hard

engineering

Soft

engineering

Costs and benefits of coastal management



Costs and benefits of coastal management



Sea Wall – very strong

but expensive

Curved wall to deflect

the energy of the waves

back out to sea.



Groyne – a timber barrier

at right angles to the beach.

It traps sediment carried by

longshore drift.

Disadvantage –

wooden groynes will

eventually rot.



Rock armour or Rip rap

– boulders placed

at the base of a cliff.

Relatively cheap and easy

to construct



Timber Revetments – slatted

wooden barrier which allows

waves to pass through andtrap beach material behind .

No access to the beach and

they may rot.

Gabions – wire cages filled

with stones. Cheap but ugly.



Beach nourishment



The addition of sand to an existing beach to make

it higher or broader. Attractive, but will wash away

again. Need groynes to keep it there.

Dune regeneration



g

Marram grassis planted to

stabilise sand

dunes and help

them develop.

Walkways protectdunes from damage

by trampling

Marsh creation



Marsh creation

This involves

allowing low lying

areas to become

flooded by the sea to

become salt

marshes



Allowing controlled

flooding in low-lying

coastal areas

OR

Allowing cliff collapse

where the value of theland and property is

low.



Mappleton



Sue Earle’s

farm,Cowden

Withernsea

Location 1 - MAPPLETON



1. Why were the sea defences necessary?

2. What type of defences were built?

3. Were they successful? How do you know?

Examples of HARD ENGINEERING Rock armour



Rock groyneRock armour

Rock armour



Location 2 - Grange Farm, Cowden

(Sue Earle’s farm!)

Location 2 - Sue Earle’s farm, Cowden



How did the sea defences at Mappleton affect this farm?

Why was the farm considered not worth saving?



Location 3



. WITHERNSEA – a small seasideresort



Curved sea wall

Rock armour

Groynes



Groynes

Why did the

il d t



council adopt a

different strategy

at each of theselocations?



CASE STUDY :

STUDLAND

Coastal areas provide a unique environment and habitat



Plant succession on sand dunes



Marram grass



Marram grass is the main

colonising species on sand

dunes It is adapted to survive



dunes. It is adapted to survive

in environments that offer

little water. The roots of these

pioneer plants stabilise thesand, making it possible for

other species to move onto

the dunes.

Eventually the dunes are

covered in a dense growth of

marram grass. The extensive

root system that the grass

produces holds the dune in

place, and organic matter from

the grass's decaying roots andstems increases the fertility of

the soil. This makes the

environment more favourable

for the growth of other plant

species.



SandMarram grassHeath



Salt marsh



Dunes under pressure from trampling

A large blowout



Massive heath fire in Studland thought to be arson



Wednesday 14th April 2010

ARSONISTS are thought to

be behind a fire whichdevastated 10 hectares of

protected heathland at

Studland.

The precious habitat –

home to a number ofendangered species – could

take up to 20 years to

recover.



The information centre and information boards help to educate the

public about the delicate environment, where to go and what is

acceptable.



There is parking provision for 2,500 cars. The design prevents

direct access to the beach.



Guidance for visitors spreads the pressure. Sandy soil is easily

worn down by trampling.

The main



The main

paths near

the carparking are

strongly

managed.



Paths exposed to

th f ll f f



the full force of

onshore winds are

kept as narrow aspossible.



An old path to the beach is regenerating behind the fence.

Visitors get a clearly signed alternative



Fire beaters are positioned within thedune area in case of fire.



Rising sea level will have important consequences

for people living in the coastal zone



Why do sea levels

rise?



As average global

temperatures continue to



rise……

• the polar ice sheets and mountain glaciers

around the world are melting leading to morewater in the sea.

• as the water in the sea getswarmer it expands

The Maldives is a

small country made

up of over 1000



up of over 1000

islands in the Indian

Ocean.

It is the lowest country

in the world. It’s

highest point is only

2.4m above seal level.



Malé – the capital of The

Maldives is surrounded

by a 3.5metre sea wall

Why are The Maldives and other small islandsparticularly vulnerable to rising sea levels?



• small size and low lying land make them vulnerable to storm

surges, tsunamis and hurricanes.

• they are isolated and a long way from help.

• they are poor, with limited natural resources and rising populations.

80% of the Maldives 1,200 islands

are no more than 1m above sea

level.

Within 100 years they could be

uninhabitable.

What are the options for the future?

IMMEDIATE MEDIUM TERM



IMMEDIATE MEDIUM TERM

LONG TERM

Develop improved higher coastal

defences.

Restore mangrove swamps

which trap sediment and build up

natural defences against the sea.

Build houses on stilts.

Create artificial islands to house

people from the outer islands

Evacuate to places which are

socially and culturally

compatible with the Maldivianpeople such as Southern India or

Sri lanka.

Possible

impacts of

sea level

Economic impacts Social impacts



sea level

rise in The

Maldives

Environmental impacts Political impacts

Possible

impacts of

sea level

Economic impacts Social impacts

Cost of sea defences e.g. the 3m

wall surrounding Mali.Eventual loss of homes and relocation

will be necessary.



sea level

rise in The

Maldives

Environmental impacts Political impacts

Cost of repairs as the islands are

more susceptible to damage by

flooding e.g. the tsunami of 2004

Loss of productive farmland as salt

water contaminates the land.

Loss of income from upmarket

tourism after tsunami floods

y

People worried by possible disasters

such as tsunamis and hurricanes,which may bring loss of life.

Communities broken up as people are

relocated.

Increased rate of erosion likely.

Loss of land and habitats.

Damage to coral reefs and

Finance decisions e.g. how to pay for

flood defences.

Negotiations with other

governments over relocation of

l ti t l hi h

3a. the coastal zone.ppt

Documents