The Coastal Zone

There are two types of waves

Waves as strong as these onlyoccur in severe storms. They can cause terrific damage to coastal settlements as well as causing a lot of erosion.

The amount of erosion which takes place depends upon:

The strength of the waves

The strength of the rock

Constructive waves lead to the formation of beaches.

Beaches are the most common feature of deposition.

What processes shape our coastline?

What processes shape the

coastal 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. Long periods 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

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

Flamborough Head

Boulder clay

Hull

Spurn Point

Former coastline

Europe’s fastest eroding coastline

North Sea

R.Humber

HeadlandCliff

Arch

Wave cut platform

Stump

Crumblingboulder clay cliffs

Rotational slump

North Sea

River Humber

Spurn Point

This movement of sediment along the coastline is called longshore drift.

Direction of movement

swash

backwash

Backwash is always at right angles to the beach

Coastal Processes - TRANSPORTATION

Beaches Spits Bars

Beaches

Beaches are accumulations of sand and shingle found where 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 cliffs are being eroded and where there are high energy waves.

As constructive waves build up beaches, they often form ridges 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

A spit

A spit is a long narrow finger of sand or shingle jutting out into the sea from the land

Spits only develop in places where:

Longshore drift moves large amounts of material along the coast.

There is a sudden change in the direction of the coastline.

The sea is relatively shallow and becomes progressively more sheltered.

Hull

R.Hu

The Formation of Spurn Point

Erosion of the coastlinenorth of Spurn Point

Eroded material transported by 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

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.

Most cliff collapse occurs 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

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• •

• •

Barmston

Mappleton

Grange Farm, Cowden

Withernsea

Easington gas terminal

Effects of the cliff collapse along the Holderness Coast

Economic effects Social effects

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 – erosion related 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 Holderness

Coast

Describe the costs and benefits of two Soft methods of coastal management. (4)

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Describe the costs and benefits of two Hard methods of coastal management. (4)

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Shoreline Management Plans are being produced around the whole coastline of England and Wales to enable coastal engineers to identify long term, sustainable policies for coastal defense.

Shoreline Management Plans identify the places that are affected or threatened by flooding or erosion. They state the likely cost of protection work for such areas and test this against the economic value of the land or property.

Managed retreat

Hard engineering

Soft engineering

Costs and benefits of coastal management

- building artificial structures aimed at controlling natural processes.

Sea Wall – very strongbut expensive

Curved wall to deflectthe energy of the wavesback out to sea.

Groyne – a timber barrierat right angles to the beach.It traps sediment carried bylongshore drift.

Disadvantage – wooden groynes will eventually rot.

Rock armour or Rip rap– boulders placedat the base of a cliff. Relatively cheap and easy to construct

Timber Revetments – slatted wooden barrier which allowswaves to pass through and trap beach material behind .No access to the beach andthey may rot.

Gabions – wire cages filledwith stones. Cheap but ugly.

- a sustainable approach to managing the coast without using artificial structures.

Beach nourishment

The addition of sand to an existing beach to make it higher or broader. Attractive, but will wash awayagain. Need groynes to keep it there.

Dune regeneration

Marram grass is planted to stabilise sand dunes and help them develop.

Walkways protect dunes from damage by trampling

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 the land 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 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?

. WITHERNSEA – a small seaside resort

Location 3

Curved sea wall

Rock armour

Groynes

Why did the council adopt a different strategy at each of these locations?

CASE STUDY :

STUDLAND

Coastal areas provide a unique environment and habitat

Plant succession on sand dunesMarram grass

PLANT SUCCESSION

Marram grass is the main colonising species on sand dunes. It is adapted to survive in environments that offer little water. The roots of these pioneer plants stabilise the sand, 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 and stems increases the fertility of the soil. This makes the environment more favourable for the growth of other plant species.

SandMarram grass

Heath

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 which devastated 10 hectares of protected heathland at Studland.

The precious habitat – home to a number of endangered 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 paths near the car parking are strongly managed.

Near the car park - boardwalks

Paths exposed to the full force of onshore winds are kept as narrow as possible.

An old path to the beach is regenerating behind the fence. Visitors get a clearly signed alternative

Fire beaters are positioned within the dune 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 more water in the sea.

• as the water in the sea gets warmer it expands

The Maldives is a small country made 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 islands particularly 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

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 Maldivian people such as Southern India or Sri lanka.

Possible impacts of sea level

rise in The Maldives

Economic impacts Social impacts

Environmental impacts Political impacts

Possible impacts of sea level

rise in The Maldives

Economic impacts Social impacts

Environmental impacts Political impacts

Cost of sea defences e.g. the 3m wall surrounding Mali.

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

Eventual loss of homes and relocation will be necessary.

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 mangroves.

Finance decisions e.g. how to pay for flood defences.

Negotiations with other governments over relocation of population to places which are socially and culturally compatible e.g. India or Sri Lanka.