Flooding in an LEDC – Bangladesh floods 2004 Effects€¦ · Flooding in an LEDC – Bangladesh...

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Flooding in an LEDC – Bangladesh floods 2004 Location Bangladesh is a low lying country that is incredibly vulnerable to flooding. It has 3 major rivers flowing through it (the Ganges, Brahmaputra and Meghna) and is vulnerable to coastal/river flooding as it is so low lying and flat. The 2004 floods lasted from July to September and covered 50% of the country at their peak. Causes Physical Tropical monsoon-type climate, a hot and rainy summer and a dry winter. Most places receive more than 1,525 mm of rain a year, and areas near the hills receive 5,080 mm. Most rains occur during the monsoon June-September. Average rainfall was 300 mm per day during the monsoon. Himalayan snow melt and receding glaciers meant that excessive volume of water had reached the Ganges, Brahmaputra and Meghna rivers. Soil saturation from rainfall meant that there was a lot of surface run-off. In late-June 2004, heavy monsoon rains swelled the waters of the Meghna River, which reached its peak level in early- July. The other rivers burst their banks in early-July, due to heavy rains in the north of the country, causing flash floods in the north and the west-central districts. Most of Bangladesh is below 10 metres above sea level. This means that the country is prone to a lot of flooding because of the height and also the annual monsoon rains. Human Increased urbanisation has meant more concrete and drains carry water very quickly to river channels which then burst. A dam at Tsatitsu Lake in the Himalayan kingdom of Bhutan had burst, spilling water into tributaries of the Brahmaputra causing more water to reach the lowlands and flood. Deforestation has meant that many that rainwater is not intercepted by the trees roots and leaves therefore soils are not held in place causing more surface run-off. Effects 750 deaths 30million people were homeless. 100,000 people alone in Dhaka suffered from diarrhoea from the flood waters. Bridges were destroyed and the airport and major roads were flooded. This hampered relief efforts. Damage to schools and hospitals was estimated at $7billion. Rural areas also suffered, the rice crop was devastated as were important cash crops such as jute and sugar. At the time of the July 2004 floods 40% of the capital, Dhaka was under water. Management and aid Food supplies, medicines, clothing and blankets were distributed. Local people began to rebuild their homes but disease from contaminated and often stagnant flood water remained a threat. The United Nations launched an appeal to raise $74million, but had received only 20% of this by September. Water Aid helped by bringing water purification tablets and education campaigns. In the long term a Flood Action Plan is in place in Bangladesh, but the embankments which are supposed to protect against flooding have not always been successful. Flood warnings and provision of food and shelter has had a more positive impact

Transcript of Flooding in an LEDC – Bangladesh floods 2004 Effects€¦ · Flooding in an LEDC – Bangladesh...

Page 1: Flooding in an LEDC – Bangladesh floods 2004 Effects€¦ · Flooding in an LEDC – Bangladesh floods 2004 Location Bangladesh is a low lying country that is incredibly vulnerable

Flooding in an LEDC – Bangladesh floods 2004

Location Bangladesh is a low lying country that is incredibly vulnerable to flooding. It has 3 major rivers flowing through it (the Ganges, Brahmaputra and Meghna) and is vulnerable to coastal/river flooding as it is so low lying and flat. The 2004 floods lasted from July to September and covered 50% of the country at their peak.

Causes Physical • Tropical monsoon-type climate, a hot and rainy summer and a

dry winter. Most places receive more than 1,525 mm of rain a year, and areas near the hills receive 5,080 mm. Most rains occur during the monsoon June-September.

• Average rainfall was 300 mm per day during the monsoon. • Himalayan snow melt and receding glaciers meant that

excessive volume of water had reached the Ganges, Brahmaputra and Meghna rivers.

• Soil saturation from rainfall meant that there was a lot of surface run-off.

• In late-June 2004, heavy monsoon rains swelled the waters of the Meghna River, which reached its peak level in early-July. The other rivers burst their banks in early-July, due to heavy rains in the north of the country, causing flash floods in the north and the west-central districts.

• Most of Bangladesh is below 10 metres above sea level. This means that the country is prone to a lot of flooding because of the height and also the annual monsoon rains.

Human • Increased urbanisation has meant more concrete and drains

carry water very quickly to river channels which then burst. • A dam at Tsatitsu Lake in the Himalayan kingdom of Bhutan

had burst, spilling water into tributaries of the Brahmaputra causing more water to reach the lowlands and flood.

• Deforestation has meant that many that rainwater is not intercepted by the trees roots and leaves therefore soils are not held in place causing more surface run-off.

Effects • 750 deaths • 30million people were homeless. • 100,000 people alone in Dhaka suffered from

diarrhoea from the flood waters. • Bridges were destroyed and the airport and

major roads were flooded. This hampered relief efforts.

• Damage to schools and hospitals was estimated at $7billion.

• Rural areas also suffered, the rice crop was devastated as were important cash crops such as jute and sugar.

• At the time of the July 2004 floods 40% of the capital, Dhaka was under water.

Management and aid Food supplies, medicines, clothing and blankets were distributed. Local people began to rebuild their homes but disease from contaminated and often stagnant flood water remained a threat. The United Nations launched an appeal to raise $74million, but had received only 20% of this by September. Water Aid helped by bringing water purification tablets and education campaigns. In the long term a Flood Action Plan is in place in Bangladesh, but the embankments which are supposed to protect against flooding have not always been successful. Flood warnings and provision of food and shelter has had a more positive impact

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Boscastle, Cornwall 16th August 2004 - MEDC Flood Location Boscastle is a small rural village, it is a popular tourist destination on the coast in North Cornwall, S.W England. It is approx. 80 miles from Plymouth. There is a confluence within the village between River Valency and River Jordan.

Physical causes Stormy weather before the flood, caused saturated ground causing surface run-off, reducing the lag time. In the hours before the flood; there was heavy rain 75mm in 2 hrs. Confluence of 2 rivers, the Jordan runs into the Valency, both overflowed causing a sudden rush of water, through the valley. The rock is granite, which is impermeable so water cannot infiltrate and so it is transported to the river by surface run-off. Steep V shaped valley – runoff occurs. Human causes Boscastle was built on a flood plain, increasing the risk of flooding. Bridges caused debris swept along by the river to become trapped behind the bridge acting like dams.

These rivers source from the Hills of Bodmin Moor.

Effects Physical - Trees were uprooted and washed downstream blocking roads making access difficult. Heavy soil erosion due to soil saturation. 20 tonnes of soil moved and deposited making the area dirty. It needed cleaning up. Built Damage to infrastructure some roads were completely impassable so people could not get food shopping or collect sandbags. 58 properties destroyed so many people became homeless and had to stay with friends/family. 84 cars wrecked meaning so people lost their ability to evacuate or move valuable personal property form being flooded. 4 footbridges washed away and major structural damage to road bridge so people found it hard to access their houses or businesses. 3 shops were destroyed so people have lost their income and livelihood. Car parks washed away meaning cars were turned upside down or permanently damaged. Sewers burst meaning that the streets started to smell and the threat of disease from human excretion. Human 60 people evacuated Insurance companies had to pay out thousands for the damage "Witchcraft Museum" was destroyed and led to loss of tourism Immediate responses/Management Helicopters from the RAF and Navy were used to evacuate the elderly and young. Buildings searched for people trapped by the fire service and mountain rescue. Trees removed to gain access to some building and businesses. Roads cleared so that emergency vehicles could reach Boscastle. Sandbags put in place to stop the rising river level from bursting. Long Term Responses/ Management £4.5 million flood defence scheme put in place with a deeper and wider river channel so that more volume of water can be transported. Drainage systems improved to make sure that water reaches the channel more efficiently. Banks of river reinforced with higher walls to protect Boscastle from further high river levels Car parks raised and impermeable surfaces used.

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Depositional Features spits, bars and beaches. Spits- Spurn Head, Holderness coast. Spurn Head is at the south of the Holderness coast. It is a sand and shingle spit 5.5km long, reaching across the mouth of the River Humber. Spurn Head is made up of the material which has been transported along the Holderness Coast by longshore drift. This includes sand, sediment and shingle. Spits are created by deposition. A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end. 1. Longshore drift moves material along the coastline. 2. A spit forms when the material is deposited. 3. Over time, the spit grows and develops a hook if wind direction changes further out. 4. Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats or salt marshes form.

Spurn Head SSSI Spurn head is a Site Special Scientific Interest SSSI. It has many important birds and plants. For example the rare birds such as merlin and peregrine (hunting birds) and the waders such as Shelduck and Brent geese. Lavender sea aster and sea rocket are flowering plants that are at risk.

Bars - Slapton Ley, South Devon, Southwest England. It is the largest natural freshwater lake/lagoon in South West England. It is 1.5 miles long and is made up of two parts (the Lower Ley and the Higher Ley). The site is a National Nature Reserve and a Site of Special Scientific Interest. It was formed over 3,000 years ago when this shingle ridge or bar created a natural dam across a river estuary. Formation The Bar has been formed by the process of longshore drift as thousands of tons of sand has been deposited over 1,000’s of years.

Marine Life in the lake The National Nature Reserve at Slapton Ley (the lake/lagoon behind the bar) is home to the Eel. During the autumn Eels start to migrate back to the sea to breed.

Beaches All beaches are formed through the process of longshore drift but also through constructive waves. Constructive waves have a strong swash but weaker backwash meaning that sand and pebbles are deposited. Storms often throw pebbles up the beach. Cliffs also provide eroded material for the beach as they may erode and cliffs collapse through processes of slipping or slumping. Beaches change daily depending on tides and wind speed which contribute to wave movement.

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Destructive

Destroys (takes beach away)

Strong backwash Weak swash

Constructive

Creates (put sand on the beach)

Strong swash Weak backwash

The size and energy of a wave is influenced by: how long the wind has been blowing the strength of the wind how far the wave has travelled (the fetch)

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These processes erode material at the coast and in a river.

Hydraulic action

The force of the water breaks rock particles away from the river

channel/cliff.

Corrasion/Abrasion

Eroded rocks rub against the

channel/thrown against the cliff wearing it away.

Attrition

Eroded rocks picked up by the river/waves

smash into each other.

Corrosion/Solution

River/sea dissolves some types of rock such as chalk and

limestone.

Coastal erosion is affected by: The point at which the wave breaks Steepness of the wave. Rock type and structure - (hard rock such as

granite is far more resistant to erosion than soft rocks, such as clay).

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These processes move material at the coast and in a

river.

Small particles are carried along by the

water.

Large particles like boulders are pushed along the bottom of the river bed/sea by

the force of the water.

Soluble materials dissolve in water and

are carried along.

Pebble sized particles are bounced along the river bed/sea by the force of

the water.

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Waves approach the beach at a slight angle influenced by the

prevailing wind.

1

As the waves break the swash carried the material up the beach at

the same angle.

As the swash dies away the backwash and any material carried by it falls

straight back down the beach.

The means that material is moved along the beach in a zig-zag route.

2

3

4

Prevailing wind

Erosion Deposition

Swash

Backwash

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Weather weakens the top of the cliff.

The sea attacks the base of the cliff forming a wave cut notch.

The notch increases in size causing the cliff to collapse.

The backwash carries the rubble back to the sea forming a wave cut

platform.

The process repeats itself and the cliff continues to retreat.

1

2

3

4

5

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Hydraulic action creates cracks in the headland.

Overtime the hydraulic action causes the crack to become deeper.

This creates a cave. This may eventually break through.

This creates an arch. The arch will eventually become bigger and

collapse.

This leaves a stack. Forces of erosion turn the stack into a

stump.

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2

3

4

5

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The sea attacks an area of coast with alternating bands of hard and

soft rock.

The soft rock (sand or clay) are eroding more quickly.

This creates a bay.

The hard rock is more resistant and takes longer to erode.

This leaves a headland jutting out to sea.

1

2

3

4

5

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Constructive waves help to build up beaches.

The soft rock (sand or clay) are eroding more quickly.

This creates a bay.

The hard rock is more resistant and takes longer to erode.

1

2

3

4

Deposition occurs when the sea deposits material on the beach. This occurs because of a change in direction of the coastline, the waves lose energy,

erosion is happening rapidly along the coast or the waves are constructive.

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Longshore drift moves material along the coastline.

A spit forms when the material is deposited.

Over time, the spit grows and develops a hook if wind direction

changes further out.

Waves cannot get past a spit, which creates a sheltered area

where silt is deposited and mud flats or salt marshes form.

1

2

3

4

A bar forms when a spit joins to two headlands.

5

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Why?

Marine processes- the sea erodes by erosional processes

Sub-aerial processes such as weathering

Mechanical weathering- includes freeze thaw when water gets into cracks and

expands and contracts.

Chemical weathering- includes solution where water reacts with

calcium carbonate in rocks.

Sliding- this is when large chunks of rock slide down the slope quickly without any warning. This can make is dangerous

to walk along the beach.

Slumping- this is when the cliffs are made of clay. The clay becomes saturated

during heavy rainfall and oozes down towards the sea.

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Social impacts

• People loose their homes if they fall into the sea. • Homes close to the cliff go down in value.

• It is difficult and expensive to insure houses close to the cliff. • It is dangerous for people to walk along the coast as the cliff could

collapse on them. • Conflict arises when the local government are not doing anything.

Economic impacts

• Road and railways near the coast are under threat. • Tourists may not visit because of danger. This affects

local businesses such as hotels and cafes. • The local economic value of the area decreases.

Environmental impacts

• Cliff collapse makes the area look unattractive. • Cliff collapse causes wildlife habitats to be lost.

• Green land and farm land is lost.

Case study facts • Homes on the cliff have been valued at £1. • Residents such as Di Wrightson have lost their businesses (she owns a guest house) • The main road has been lost. • 24 homes have fallen into the sea. • By a rock for Happisburgh has been set up to raise money for sea defenses. • Agriculture and tourism contribute to the economy significantly. • The local government is pursuing a policy of managed retreat and so locals are having to

fight for compensation-most are loosing everything. • The village has a strong community with a light house, church and shops which will all

be lost

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Social impacts

• People will be forced to leave their homes and possibly become

environmental refugees in neighboring countries. The total population is 400, 000.

• The traditional way of life will be lost. • In Kandholhudhoo, a densely-populated island in the north of the

Maldives, 60% of residents have volunteered to evacuate over the next 15 years.

• Tidal surges flood the peoples homes every fortnight, and recently hammered a 3m (9.8ft) hole in their concrete flood defences.

Economic impacts

• Rising sea levels could put an end to the tourism industry. • As the coral reefs are affected by warming temperature so

will diving tourism. • The fishing industry will slowly disappear- the majority of

Maldivians rely on this for their income and farming is not possible.

Environmental impacts

• Coral reefs will die as they are bleached and the water gets deeper.

• The ecosystem associated with the reefs will be lost. • Fish numbers are lowering as the ecosystem is being

destroyed. • As the sea levels rise the islands become more

vulnerable to events such as tsunamis and coastal flooding.

Political impacts

• The whole country could disappear under water. • The government is looking to other countries for help- Japan paid 99% of the $63m bill

for a 3 m high wall to built around the capital Male. • Politically it puts the government under a lot of pressure to sort it out. This in Feb 2012

the president was removed in what some have called a coup.

The Maldives is a small country made up of a group of 1000 islands in the Indian Ocean. It is the lowest country in the world. Tourism is very important providing 30% of the country’s GDP. Global warming is blamed for the countries rising sea levels.

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Rip-rap

Breakwater

Groynes

Gabions

Sea wall

Revetment

Expensive Unattractive

Long-term Beaches

remain natural

Easily destroyed South beaches a

deprived of sediment

Build up the beach

Cheap

The boulders are good at absorbing wave energy

Prevents erosion.

Acts as a flood barrier

Expensive Need maintaining Creates a strong

backwash

Can easily be moved

They need to be replaced

Cheap Efficient

Cages rust Short

lifespan

Expensive Creates a strong backwash which erodes under the barrier.

They absorb the wave energy

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Beach replenishment

Creates wider beaches.

Protects from erosion and flooding

Looks natural

Taking material can kill organisms

It is very expensive It has to be repeated Could affect tourism

Managed retreat

Creates new marshland habitats

Fairly cheap Flooding is reduced

May cause conflict due to lost land.

Could affect peoples lives.

The purpose of soft engineering is to work with the natural processes

of the coast.

Beach replenishment Adding sand and sediment to the beach from the sea floor.

Managed retreat Allowing a section of land to flood in order for plants to grow and therefore become a natural wave and flood barrier.

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Social

Economic

Environmental

Deaths

Water supplies affected

Loss of housing

Loss of jobs Damage to infrastructure

Loss of tourism

Floods damage farm land

Businesses on the edge

House prices fall

SSIs are threatened by

erosion

Ecosystems are affected as sea water has high salt content

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Old Management (all 40 years old)

-Revetments – now damaged

(from a storm) and not effective -Groynes were placed to stop the rate of erosion, however they are not helping enough.

-Rock Armour – now little effectiveness

Increasing climate change and

sea level rise are impacting and increasing erosion

Conflict from managed retreat

-To repair revetment cost £5 million, not cost effective -Farmers lose land and livelihood

-Insurance companies won’t pay out -Increasing protest from locals to central government but g’ment has said no.

-Defences would cost more than the land and homes are worth. -Locals want compensation for the lack of management and for their homes collapsing

into the sea. -The historical lighthouse has had to be moved further back from the edge of the cliff.

-local campaign ‘buy a rock for Happisburgh’ to raise money for private defences.

-A small village with a pub , tea shop, lighthouse, church and homes -850 population

-Mainly farmland -No main roads

-Historic records indicate that over 250 m of land were lost between 1600 and 1850. -The cliffs are soft clay, so erode very quickly. Weathering increases the erosion rate. The location of

Happisburgh causes increasing problems with powerful waves from the North sea, which creates landslides from eroding the base of the cliff.

By 2055, loss of 20 more properties

Loss of caravan park and farmland

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Where? Studland Bay is located in Dorset and is very popular with

tourists. Up to 1.5 million people visit every year. Most tourists arrive by car.

Environmental characteristics o The nature reserve includes sand dunes and heath. o In this type of environment there is a unique ecosystem. o The area is internationally important and is a conservation area

managed by the National Trust.

Species that inhabit the area A special grass called marram grass grows on the sand and

holds the dunes together. This allows more vegetation to develop creating a natural heath.

The low shrubs and small trees allow butterflies, insects, small animals and sea bird to survive.

It is the richest 1000 hectares for wildflowers in the country. The area supports many rare bird such as the nightjar. The sand lizard is one of the native species.

Issues The nature reserve and sand dune are a vulnerable

environment. The vegetation takes many years to establish. If the habitat is destroyed the eco-system will break down. It is home to rare species of plants and birds and all 6 British

reptiles. The area attracts many tourists and gets very busy in the

summer. Visitors need somewhere to park and other facilities such as

paths and toilets Visitors bring problems such as litter.

Strategies to ensure environmental conservation but sustainable use.

o Vulnerable areas have been fenced off to limit access and

damage. o Bird-watching hides and guided walks help visitors to enjoy

the wildlife properly. o No driving on the beach and limited car parking spaces. o Specific paths have been created to keep visitors off the

dunes. o Jet ski’s are not allowed to be launched from the beach and

a 5mph speed limit to reduce the noise. o Dogs are not allowed on the beach in the Summer. o Tourists are focused into one area with the facilities such as

a shop and toilets. o Information boards to educate visitors about the wildlife

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The Holderness coastline – management of a zone of rapid erosion

Location The Holderness Coastline is in the North of England and runs between the Humber Estuary in the south and a headland at Flamborough head. It has the unenviable reputation as the number one place in Europe for coastal erosion, and in a stormy year waves from the North Sea can remove between 7 and 10m of coastline

Why is it eroding? The clay is an unconsolidated WEAK mass of clay particles and boulders it erodes more rapidly (forming a bay) than the more resistant rock of chalk in the north which forms the headland – Flamborough Head. In the chalk headland there are stumps and blowholes.

Indeed, today, farmland, tourist sites such as caravan parks and villages remain under threat. The weak clay, stormy nature of the North Sea, and rising sea levels of 4mm per year mean that the future is bleak for parts of this coastline. In addition to the clay being vulnerable to erosion, it is also prone to slumping. This is because water enters cracks and pore spaces in the rock, adding weight and making it slump.

Protection There are a number of settlements along the Holderness coast. Bridlington, at the northern end is the only large resort – most of the others are small. They include Withernsea and villages such as Barmston and Mappleton. There is also a North Sea Gas terminal at Easington that is coming under increased threat from erosion. Some defences have been attempted. • Mapleton and the road running through it, the B1242 links towns along the

coastline and would have been lost to coastal erosion if protection measures were not put into place. It was decided that the cost of coastal defence for a village of only 100 people was less than the cost of building a new road. So, blocks of granite were brought in and placed along the cliff base and 2 rock groynes were put into place to trap sediment moving because of longshore drift. Estimated cost 17 million. A wide beach has developed due to longshore drift. However erosion rates to the south have increased and Great Cowden Farm (1km away) is having to be abandoned as erosion has reached some of its buildings due to sediment not building up the beach anymore.

• Withernsea, for example, has a modern sea wall with rock armour in front

of it (costs up to £10,000 per metre!) to take the force out of large storm waves. There are groynes (cost about £5,000 each) along the beach to trap sand and widen the beach.

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Kielder Water fact file Located in Northumberland it is the

biggest man-made reservoir in northern Europe.

It is 2km and 52m deep. It cost £167 million and was completed

in 1982. It was built to meet the increasing

water demand from north-east England which was to be caused by the increasing population and growth of steal and chemical industries (which have actually declined).

It is a water transfer scheme (water moved from one area to another).

The water from the reservoir is released into nearby rivers such as the Tees when they are low.

The water is also released for extra household and industrial use.

It can provide up to 909 million litres of water a day.

Social impacts o The north-east now has the most reliable water

supply in England. o Reduced risk of droughts and therefore the

measures that come with this. o Only a few families had to be moved and re-

housed when the reservoir was built.

Economic impacts o Kielder Water has become a major

tourist attraction. This has created jobs and the local economy.

o Forest park around Kielder Water is harvested for timber and employs about 200 people.

o The reservoir and dam requires maintenance which costs money.

Environmental impacts o If pollution occurs downstream then

clean water can be released to dilute and flush it out to sea.

o The water is used to generate hydroelectric power at the Kielder Dam.

o The release of fresh clean water into the the River Tyne has encouraged salmon and sea trout to breed.

o The creation of the reservoir disturbed wildlife.

Sustainable supplies The environment agency thinks our water can be made more sustainable by: a) Consider the needs of the environment,

wildlife, fisheries and recreation when allocating water supplies.

b) Share water resources where there is a surplus.

c) Make appliances that are more water efficient.

d) Reduce water leakage from pipes and reservoirs.

e) Make new homes more water efficient. f) Increase the use of rainwater harvesting and

grey water recycling for agriculture, industry and commercial use.

g) Charge more for water to encourage people to use only what they need.

h) Install water meters in all homes so people are charged for what they use.

Kielder water – a water transfer scheme in the UK

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UK Physical Landscapes -Coasts

Unit 1

Coastal Processes

Waves are formed by wind blowing over the sea. The size of wave is determined by the strength of the wind, the duration of the wind and

the distance the wind blows over (fetch).

Constructive waves are low with long wavelengths. The swash is stronger than the backwash. They build beaches

Destructive waves are higher with shorter wavelengths. The backwash is stronger than the swash eroding the coast.

Weathering

Weathering is the decomposition or disintegration of rock in its original place (erosion involves moving rock)

Chemical Mechanical

• Carbonation. Carbon dioxide dissolved in rainwater forms a weak acid. Reacts with limestone and chalk to form a solution

• Hydrolysis – acidic rainwater reacts with minerals in granite

• Oxidation – oxygen in rain reacts with iron

• Freeze thaw.

• Salt weathering – salt in sea water expands to form cracks.

Landforms of erosion

Wave cut platforms Caves, arches and stacks

Mass Movement

Mass movement is the movement of material downslope under the influence of gravity. It is the falling, sliding or flowing of rock, sediment or soil most often along a slip plane (line of weakness). Different types of mass movement can include rockfall, landslides and rotational slumping.

Rockfall Landslide Slumping

Individual fragments of rock fall off cliff usually due to freeze thaw

Rocks fall in a linear fashion along fault lines

Occurs on a curved surface lubricated by water

Coastal Erosion

Erosion is the removal of material and sculpting of landforms

Deposition: Sediment dropped by the waves. Creates beach. The beach is made of material transported by longshore drift.

Coastal Transportation

The shape of the coast is determined by geology. Hard rocks (chalk, granite) erode slowly. Clay and sandstone are softer and erode faster

Hard rocks will form headlands and erode slowly.Soft rocks will form bays and erode quickly

Landforms of deposition

Sand dunes

Spits

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Coastal Management Strategies

Hard Engineering

Strategy Benefits Costs

Sea wall – concrete structure at top of beach acts as a barrier to sea

• V effective• Can develop top for walking,

stalls etc

• £5000 - £10000 / metre• V expensive• Ugly

Rock Armour – large boulders at foot of cliff to reduce force of waves

• Relatively effective at reducing force of waves

• Relatively cheap

• £2000 000 / 100 metres• Ugly• Can be dangerous to public

Gabions – wire cages filled with rocks. Permeable so improve cliff drainage

• Flexible• Cheaper £50 000 / 100 metres• Quick to construct

• Not attractive• Cages can break• Need replacing every 10 years

Groynes – wooden or stone fences built at right angles to coast to stop longshore drift

• Create wider beaches• Cheap

• Starve beaches further down the coast making them narrower and so more likely to erode

• Need some maintenance

Soft Engineering

Beach nourishment / reprofiling. Adding sand to a beach or changing its shape eghigh ridges

• Looks natural• Creates amenity for tourism• Cheap

• £50 000 / 100 metres but can vary

• Needs constant maintenance• Less effective than hard

engineering

Dune Regeneration • Considered natural• Creates area for picnics etc• May increase biodiversity

• £2000 per 100 metres. Time consuming to plant and maintain

• Easily damaged by storms• Not particularly effective.

Managed Retreat

Doing nothing. Allow sea to move into area

• Long term solution with low maintenance

• A natural buffer• New ecosystem created• Biodiversity improves, eg bird

watching• More attractive

• Low value land is lost to sea

• Local people have to move so need to be compensated

• Some ecosystems may be lost

Coastal Management example - Holderness

Mali is an LIC. It has used agroforestry as a sustainable farming technique

Maize is grown under tress and nitrogen fixing plants. The plants add nitrogen so no need for fertiliser. Shade helps plants grow. Soil erosion is reduced as roots stabilise soil. Leaf fall adds nutrients to soil. Trees provide protection from wind and help draw moisture up for the maize.

What is the problem?

• Erosion is causing cliffs to collapse. Cliffs are made of soft, easily eroded boulder clay

• Prevailing winds mean material is moved south through LSD• About 1.8m of land is lost each year. Farms and businesses are

threatened• Over 11km of coast is managed suing hard engineering to protect the

towns of Hornsea, Withernsea and Mappleton as well as roads and the gas terminal at Easington that supplies 25% of the UIK’s gas and is right on the cliff.

Management strategies Problems

• Rock armour used. 450 m of coast line protected by 61 000 tonnes of rocks at a coast of £2million.

• Rocks absorb the power of the waves

• 2 rock groynes trap sand and create a beach to protect the cliffs

• Hornsea has a sea wall and some groynes and at Withernsea there is a sea wall, groynes and rock armour

• Mappleton is protected but groynes prevent sediment moving south leading to increased erosion south of Mappleton

• Farms and a caravan park have been lost south of Mappleton

• The Lifeguard station at Great Cowden is under threat as the spit does not get sediment

• Spurn Head spit is being washed away

• Protecting the gas terminal at Easington cost £6.6 million

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Rivers and river valleys

Fluvial Processes

Erosion

Term Definition

Hydraulic action Flowing water erodes the bed and banks. Found at waterfalls and meanders

Abrasion Scraping of rivers bed by particles of rock –like sandpaper

Attrition Rounding and smoothing of rock as they rub against each other

Solution Dissolving of soluble chemicals esp. limestone

Vertical erosion Downwards erosion – common in upper course

Horizontal erosion Sideways erosion – common in middle and lower course

Transportation

Traction Rolling of large rocks

Saltation Bouncing of small rocks

Suspension Particles suspended in water

Solution Chemicals dissolved in river

River Landforms

Upper course (erosion)

Interlocking spurs water flows around fingers of harder rock. Vertical erosion deepens the valley

Waterfalls –a step in the long profile, usually over a fault. Water flows over hard rock. A plunge pool forms at the bottom due to hydraulic erosion.

Gorges – as a waterfall retreats the cap rock collapses and the process starts again forming a steep sided gorge

Middle Course (erosion and deposition)

Meanders – bends in the river. Where water flows fastest erosion happens on the outside curve. On the inside curve, water is slower so deposition occurs forming a slip off slope

Oxbow Lakes Where the neck of the meander is breached during flood leaving the old meander curve as a lake

UK Physical Landscapes -Rivers

Unit 1

Lower course (deposition)

Levees – Raised banks formed after a river floods

Floodplains – wide areas of flat land – often good form farming

Estuaries – Where the river meets the salt water of the sea. Salt marshes are common.

Factors affecting flooding

Physical Human

• Precipitation• Geology• Relief

• Farming• Urbanisation• Deforestation

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River Management Strategies

Hard Engineering

Strategy Benefits Costs

Dams & Reservoirs– Concrete dams control river flow by creating artificial reservoir

• Can be used for HEP or tourism• Creates new wetland habitats• Creates source of drinking

water• V effective

• V expensive (Kielder dam cost £167 million)

• Social costs of displacement• Reservoirs silt up• Can lead to conflict over water

rights eg Nile

Channel Straightening – water flows out of area faster

• Insurance premiums may fall• Effective• Navigation improved

• Lead to flooding downstream• High maintenance• unattractive

Embankments – artificially raised using concrete to deepen channel

• Increased capacity for carrying water

• Creates walkways (eg London)• New river bank habitats

• Expensive• Looks artificial• More serious flooding if

embankment fails (New Orleans)

Flood Relief Channels – new channels to by pass towns

• Opportunities for recreation (fishing and walking)

• New aquatic habitats creates• Insurance premiums reduced

• V expensive – Jubilee River cost £110 million)

• Regular maintenance needed• Habitats disturbed

Soft Engineering

Flood Warnings. - monitoring rivers to allow floods to be predicted

• Sustainable• Low cost• Focus on helping people

• People may not respond• Need for monitoring

equipment

Floodplain Zoning – not building in flood areas

• Low cost• Conserves water meadows for

recreation and wildlife

• Restricts economic development

• Housing shortage• Hard to implement

retrospectively

Planting trees – Trees increase interception and slow flooding

• Crates habitats• Natural• Low cost

• Loss of farmland• Loss of economic use of land• Not totally effective

UK River example - Clyde

Th • The River Clyde is in Scotland• It is 160 km long• Its source is in the Southern

Uplands• Its mouth is near Glasgow

Key Features

SourceInterlocking spursWaterfalls

Gorge

Meanders

Flood Plain

Estuary

• Near Crawford• North of Crawford• Falls of Clyde near Lanark (27 m

high)• Where waterfalls are retreating

steel river cliffs• Between Motherwell and

Glasgow• Glasgow is on flood plain. Used

for shipbuilding in past• 34km west of Glasgow.

Mudflats exposed at high tide

Boscastle, Cornwall Flood August 2004

Flash flood caused millions of pounds of damage and disrupted tourism. In response the old bridge was replaced by a taller one to allow debris to pass under, the river channel was deepened and widened, the embankment was strengthened, a flood wall was built, dead trees and vegetation were removed, the car park was raised and a gauge was installed to monitor water levels

Social Issues Economic Issues Environmental issues

• Residents lives disrupted during building of new defences• Many residents think new bridge is ugly and not in

keeping with village• Safer• Will protect against a 1 in 75 year flood only

• Homes and businesses less at risk of flooding• Scheme cost over £4 million. Some idea

rejected on basis of cost

• Vegetation in river habitats monitored and biodiversity improved

• New channel has been engineered to look natural

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Social impacts • People will be forced to leave their homes and possibly become environmental refugees in neighboring

countries. The total population is 400, 000. • The traditional way of life will be lost. • In Kandholhudhoo, a densely-populated island in the north of the Maldives, 60% of residents have

volunteered to evacuate over the next 15 years. • Tidal surges flood the peoples homes every fortnight, and recently hammered a 3m (9.8ft) hole in their

concrete flood defences.

Economic impacts • Rising sea levels could put an end to the tourism industry. • As the coral reefs are affected by warming temperature so will diving tourism. • The fishing industry will slowly disappear- the majority of Maldivians rely on this for their income and

farming is not possible.

Environmental impacts • Coral reefs will die as they are bleached and the water gets deeper. • The ecosystem associated with the reefs will be lost. • Fish numbers are lowering as the ecosystem is being destroyed. • As the sea levels rise the islands become more vulnerable to events such as tsunamis and coastal

flooding.

Political impacts • The whole country could disappear under water. • The government is looking to other countries for help- Japan paid 99% of the $63m bill for a 3 m high wall to built around the capital Male. • Politically it puts the government under a lot of pressure to sort it out. This in Feb 2012 the president was removed in what some have called a

coup.

Location and facts The Maldives is a small country made up of a group of 1000 islands in the Indian Ocean. It is the lowest country in the world. Tourism is very important providing 30% of the country’s GDP. Global warming is blamed for the countries rising sea levels.

The Maldives -Rising sea levels

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Hard and Soft engineering: which is the better option? Hard engineering strategies involve the use of technology in order to control rivers. Hard engineering approaches tend to give immediate results and the river but are expensive. However, in the future, they may make problems worse or create unforeseen ones. Soft engineering, adopts a less intrusive form of management, seeking to work alongside natural processes. Soft engineering is much cheaper and offers a more sustainable option as it does not interfere directly with the river’s flow.

Give 3 examples of each

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A case study of a flood management scheme in the UK - The Morpeth Floods

After a flood in 1963, a flood defence scheme was established. Flood walls were built on the north bank to protect the main business district. Housing properties at Middle Greens on the south bank were also protected by flood walls. These defences were exceed by the river on the 6th and 7th September 2008 and a new flood defence scheme put in place as a result. Causes of the 2008 Floods The flood of 2008 was estimated to have been a 1 in 115 year event. It was caused by; 1. Prolonged rainfall - 150 millimetres of precipitation fell in the drainage basin between Friday 5 and Saturday 6 September. 2. The River Wansbeck Valley is narrow and steep causing huge amounts of surface runoff. 3. The soil was already saturated due to the wet summer causing surface runoff. 4. Increased urbanisation since the 1960s in Morpeth resulting in water being drained directly into the river. 5. The lag time was only 8 hours. Water falling in the catchment area would have been rapidly converted into channel flow by surface runoff and to a lesser extent by throughflow. All of these factors resulted in a peak water level of 3.99 metres recorded in the river channel, the biggest flow ever.

Social Impacts 400 residents were evacuated. Shelter was provided in the Town Hall, King Edward VI High School and County Hall. An error made by the Environment Agency's warning system meant that 198 properties in the Middle Greens area of the town did not receive a flood warning. Many residents had to be forced from their homes, and lived in caravans or with relatives as rebuilding took place. Responses - Fire fighters, ambulance crews, the RAF, the RNLI and the British Red Cross were among the emergency services involved in rescue and recovery operations over the weekend. Economic 995 properties in Morpeth town centre were directly affected. Estimated cost of damage >£10 , the Journal Newspaper claimed it was £40 million. The library suffered severe structural damage due to the heavy debris transported by the river. Structural engineers were required to test its safety. Responses On Sunday 7 September, Morpeth Lions Club and the Red Cross launched the Morpeth Flood Disaster Fund and by Wednesday 10 September had raised over £20,000. Environmental Morpeth High Street (Bridge Street) was under 60 centimetres (2.0 ft) of water. Houses were full of mud and sewage. NEW plans: 1. A system of higher flood walls along weak spots in the town – walls were raised by 30cm in the most vulnerable areas 2. Poles were placed in the River Wansbeck to catch debris upstream, to stop debris clogging up the bridges in the town which caused some of the flooding. 3. Culverts were cleared that drain water in Morpeth so that areas were well drained 4. Construct a huge upstream reservoir - which would hold over one million cubic metres of water- would only allow through a volume of water manageable by the town centre defences. 5. Build new flood walls in areas that had none 6. Add an earthen embankment to protect the housing estate of High Stanners The social, economic and environmental issues involved with the flood management scheme. Economic. Overall, the scheme cost £26 million pounds, a massive sum of money to protect residents in a small town in the North of England. Social -The flood walls were also raised to a height of 1.8m, which obscures the view of the river for many residents and which intrudes in the natural landscape but the reservoir and the scheme will reduce the flood risk significantly. Environmental- The walls are also a barrier to some forms of wildlife. The culvert clearance is a good thing, as this provides areas with faster flowing drains for some fish and birds.

Location Morpeth is an ancient market in NE England. It lies in a meander loop of the river Wansbeck. It’s 15 miles north of Newcastle upon Tyne and 12 miles west from the North Sea.

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Physical landscapes in the UK: Urban issues and challenges (Paper 1: Section C)

Relief is the term used to describe the physical features of the landscape this included height above sea level;, steepness of slopes shapes of

landscape features. Relief is determined by geology, the rocks that form the landscape.

The UK have an extensive river system. Most rivers have their source in the mountain ranges

or hills and flow to the sea.

The UK’s upland areas tend to be in the north and west of the UK. Examples include Snowdonia, which is a glaciated upland, it has steep mountains and glaciated valleys. Grampian Mountains: Part of the Highlands and home to Ben Nevis. They are steep, rocky and sparsely populated.

The UK’s lowland areas tend to be in the south and east of the UK. Most cities are in lowland areas and often on the UK’s main rivers such as London on the River Thames, Liverpool on the River Mersey, and Cardiff on the River Severn.

UK Physical Landscapes

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Coastal Landscapes in the UK: The coast is shaped by a number of physical processes.

1.Waves: What are waves?• Waves are formed by wind blowing over the sea• Friction with the surface of the water causes ripples to form and these develop into waves. • The distance the wind blows across the water is called fetch. • The longer the fetch, the more powerful / larger the wave (The south west prevailing wind causes long fetch, this is why there are large waves for surfing

the south west)

What happens to waves when they reach the coast?• In the open sea, the energy within a wave moves in a circular motion. • As a wave moves towards shallow, coastal waters, the base of the wave is in is in contact with the seabed, causing friction• This slows down the base of the wave down, reducing the distance between waves down (wavelength) and this increases wave height• The wave breaks because the top of the wave is moving faster than the base

What happens to waves when they reach the coast?• In the open sea, the energy within a wave moves in a circular motion. • As a wave moves towards shallow, coastal waters, the base of the wave is in is in contact with the seabed, causing friction• This slows down the base of the wave down, reducing the distance between waves down (wavelength) and this increases wave height• The wave breaks because the top of the wave is moving faster than the base

What happens when waves break?• Breaking waves force water and beach sediment up the beach as swash• When all the energy from the breaking wave has been used gravity takes the water back down the beach as backwash

SWASH –movement of waves up the beachBACKWASH –movement of water down the beach (gravity)

Coasts are constantly change and being shaped by 1.Wave types, 2.Coastal processes: weathering processes , mass movement, erosion ,transportation , deposition

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Coastal Landscapes in the UK: The coast is shaped by a number of physical processes.

As a result of swash and backwash, waves are the most important force in shaping the coast. There are two types of wave

Characteristic Constructive wave Destructive Wave

Wave Height Low High

Wave length Far apart Closely spaced

Type of wave break

Spilling Wave is high and steep before plunging down onto the beach

Strength of swash Powerful swash, pushing sand and pebbles up the beach

Weak – little swash as little movement forward

Strength pf backwash

Not as strong as swash Powerful

How it shapes the coast

Build up beaches by depositing sediment

Removes sand and pebbles and gradually destroys the beach. These waves are the waves that carry out erosion procession.

Constructive wave

Destructive wave

Waves and interaction with coastline:Material is transported along coasts by a process of long shore drift:1. Waves follow the direction of the prevailing wind, the

movement of water and sediment up a beach is known as the swash, and is the direction of swash is largely determined by the prevailing wind.

2. Whereas the movement of water back down the beach is known as backwash, and its direction is determined by the slope of the beach, and the water will move back at right angles to this slope. These 2 wave actions interact to give us LONGSHORE DRIFT,

3. This moves sediment in one general direction along the coastline in a zig-zag fashion, governed by the prevailing wind.

4. This action is important, as it moves or erodes sediment from an up current area and moves it down current, changing the shape and sizes of beaches.

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Coastal Landscapes in the UK: The coast is shaped by a number of physical processes.

2a. Coastal Processes: Weathering • Weathering is the breakdown of rocks where they are. There are two types of weathering: chemical and mechanical• Whereas erosion is when the rocks are broken down and carried away by something like a wave

Type Mechanical Chemical

Description

Is the breakdown of rock without changing its chemical composition. The type of mechanical weathering that affects coasts is freeze thaw

Is the breakdown of rock by changing its chemical composition. Carbonation weathering is a types of chemical weathering that happens in warm and wet conditions.

Process Freeze Thaw1) It happens when the temperatures alternates above and below 0 degrees C (freezing

point of water)2) Water gets in to cracks in the rock3) When the water freezes it expands, which puts pressure on the rock, When the water

thaw it contracts, which releases the pressure on the rock4) Repeated freezing and thawing widens the cracks and causes the rock to breakup

Carbonation weathering1. Rainwater has carbon dioxide dissolved in it, which makes it a weak

carbonic acid2. Carbonic acid reacts with rock that contains calcium carbonate e.g

carboniferous limestone, so the rocks are dissolved by the rainwater

2b. Coastal Processes: Mass Movement • Mass movement is the downhill movement of weathered material under

the force of gravity. • The speed can vary considerably. • It is basically when material falls down a slope. • Mass movement causes coasts to retreat rapidly• It is more likely to happen when material is full of water it acts as a

lubricant and makes it heavier• There are three types of mass movement: Slides, Slumps and Rockfalls

Slides Slumps Rockfalls

Slumping: where the section of cliff drops down along a line of weakness, Sliding – or landslides are where a mass of unconsolidated material moves down a slope often a period of rainfall, Rock fall – where material falls from a cliff face and lands at the base of a cliff. This is often seen on chalk cliffs

2c. Coastal Processes: Erosion• Erosion is when the rocks are broken down and carried away by something like a wave. There are three types

Name Description

Abrasion Erodes sediment in the water scrape and rub against the rock, removing small pieces

Hydraulicpower

Waves crash against rock and compress the air in the cracks. This puts pressure on the rock. Repeated compression widens the crack and makes bits of rock break off

Attrition Eroded sediment in the water smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together

2d. Coastal Processes: Deposition. Deposition is when material being transported by the sea is dropped It occurs when the flow of water slows down. Waves lose energy in sheltered bays, or where there spits and bars. Sediment is no longer carried but deposited. This is why beaches are found in bays, where wave energy is reduced. Waves that deposit more material than they erode are constructive waves

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Characteristics and formation of landforms resulting from erosion – headlands and bays, cliffs and wave cut platforms,

caves, arches and stacks.What is a Landform? Landform is a feature of the landscape which has been formed by erosion, transportation and deposition. Erosion by waves form many coastal landforms over a long period of time

What factors influence coastal landforms? Type of geology: rock type has a significant influence on coastal landforms. Rocks that are stronger and more resistant such as chalk and limestone erode more slowly and produce cliff and headland (a narrow piece of land extending out into the seas). Less resistant rock like clays and sands are more easily eroded to form bays and low lying stretches of coastline.Geological structure: if there are faults (cracks in the rocks) or how the layers of rock are folded

Headlands and bays1. Soft rock or rocks with lots of faults have low resistance to erosion. Hard

rock with a solid structure have a high resistance to erosion2. Headland and bays form where there are alternating banks of resistant

and less resistant rock along a coast3. The less resistant rock e.g clay is eroded quickly and forms a bay which

have a gentle slope4. The resistant rock e.g chalk is eroded slowly and it left jutting out,

forming a headland – headlands have steep side

Caves, Arches and stacks1.Headlands have lines of weakness (faults) that are venerable to

erosion. Waves wear away the rock along a line of weakness through abrasion and hydraulic action which widen the fault to form a cave

2.Waves make the cave larger until it cuts through the headland to make an arch

3.Arch is eroded and the roof of the arch becomes too heavy and collapses, this leaves a tall stack

4.The stack is eroded to form a stump

Cliffs and wave cut platforms1. Most erosion happens at the foot of the

cliff, this forms a wave cut notch, which is enlarged as erosion continues

2. The rock above the notch becomes unstable and eventually collapse

3. The collapsed material is washed away and a new wave cut notch starts to form

4. Repeated collapsing results in cliff retreating. As wave cut platform is the platform left behind as the cliff retreats.

4.Stump

3. Stack

2. Arch1. Cave

Fault in resistant rock

Roof of Arch too heavy collapses

Headland

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Characteristics and formation of landforms resulting from deposition – beaches, sand dunes, spits and bars.

Beaches1. Beaches are found on coast between the high water mark (the highest point on the land the sea level gets to) and the low water mark (the lowest point

on the land the sea level gets to)2. They are formed by constructive waves, depositing material like sand and shingle. Sand and shingle beaches have different characteristics 3. Sand beaches - are flat and wide and are found in sheltered bays. The waves are constructive waves and have a strong swash and build up the beach.

Sand particles are small and the weak backwash can move them back down the beach creating a long gentle slope. Berms mark the high and low tide4. Single beaches – or pebble beaches are steep and narrow. Shingle sediment are large and the weak backwash cant move them back open the beach.

Sans dunes 1. Sand dunes are formed when san deposited by longshore drift is picked up by strong winds and blown from the

beach inland. 2. Obstacles (e.g driftwood) cause wind speed to decrease so sand is posited.3. The sand is taken over by plants and grasses, which are held together by long rooted grasses such as marram. The

vegetation stabilises the sand and encourages more sand to accumulate there, forming small dunes called embryo dunes.

4. When vegetation dies, it decomposes fertilising the dunes, will allow a great range of vegetation to grown here and stabilise the dunes further. Embroyo dunes will eventually form mature dunes.

Bars1.A bar is formed when a spit

joins two headlands together2.The bar cuts off the bays

between the headlands from the sea

3.This means a lagoons can form behind the bar

Spits1. Spits are a sharp bend in the coastline e.g at a river mouth, they are ridges of sand and

shingle that has been transported along the coast by longshore drift.2. When there is a change in the shape of the coastline or direction, sediment continues

to be transported in the same direction of the original coastline , eventually being deposited to form a ridge of sediment sticking out into the sea,

3. Strong winds and waves can curve the end of the spit forming a recurved end4. The sheltered area behind the spit is protected from waves, lots of material

accumulates in this area like silt and md which means plants grow here. Over time, the sheltered area can become a salt marsh (an area of coastal grassland regularly flooded by sea water)or mud flats (a stretch of muddy land which is uncovered at low tide)

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An example of a section of coastline in the UK to identify its major landforms of erosion and deposition.

The Dorset Coast is an example of coastal landforms, specifically Swanage.• Swanage is a seaside town in Dorset in the south coast of the UK• It is located in a sheltered bay and has a broad sandy beach.• Dorset coast is made from bands of hard rock (limestone and chalk) and soft rock like (clay). These rocks have eroded at different rates giving headlands

and bays• The alternating bands of hard and soft rock have resulted in bays and headlands.

Formations by erosion: Swanage Bay and Studland bay, areas of soft rock (clay and sandstone). In between is the headland Ballard point, made from a band of harder rock (chalk). The end of the headland has been eroded to a stack called Old Harry and a stump called Old Harry’s wife.

Formations by deposition : North of Swanage is Poole Harbour one of the UK largest natural harbour. A great deal of deposition has taken place in this large sheltered bay and you can see two spits. At Studland bay there are lagoons, saltmarshes and sand dunes.

Key word for formationsArch - A wave-eroded passage through a small headland. This begins as a cave formed in the headland, which is gradually widened and deepened until it cuts through. Cave - A large hole in the cliff caused by waves forcing their way into cracks in the cliff face. Cliff - A steep high rock face formed by weathering and erosion along the coastline. Headlands and bays - A rocky coastal promontory made of rock that is resistant to erosion; headlands lie between bays of less resistant rock where the land has been eroded back by the sea. Stack - An isolated pillar of rock left when the top of an arch has collapsed; over time further erosion reduces the stack to a smaller, lower stump.

Wave cut platform - A rocky, level shelf at or around sea level representing the base of old, retreated cliffs.

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Defence What is it Benefits Costs

A wall made out of a hard material like concrete that reflects waves back to sea

It prevents erosion of the coast. It also acts as a barrier to prevent flooding

It creates strong backwash which erodes under the wall. Sea walls are very expensive to builtand maintain

A wall of wire cages filled with rocks usually built at the foot of cliffs

The gabions absorb wave energy and so reduce erosion. They’re cheap and easy to build.

They’re ugly to look at and the wire cages can corrode over time

Boulders that are piled up along the coast (sometimes called rip rap)

The boulders absorb wave energy and so reduce erosion and flooding and its fairly cheap

Boulders can be moved around by strong waves and so need replacing.

Wooden or stone fences that are built at right angels to the coast. The trap material transported by longshore drift and preserve the beach

They create wider beaches which slow the waves. This give great protection from flooding and erosion. It is fairly cheap defence

They starve beaches further down the coats of sand, making them narrower. Narrower beaches don’t protect the coast as well leading to great erosion and floods

Different management strategies can be used to protect coastlines from the effects of physical processes.

• The aim of coastal management is to protect people and the environment from the impacts of erosion and flooding• This is done because coastal areas are both a place for industrial development and places to live, this means that a growing number of people are at risk

from coastal erosion and flooding• There has not always been a need to protect vulnerable coastal areas, however it is likely to increase in the future due to climate change • There are three methods to protect coastlines1. Hard Engineering 2. Soft Engineering 3. Managed Retreat

Defence What is it Benefits Costs

Sand and shingle from elsewhere (sea bed) or from lower down the beaches is added to the upper part of beaches

It creates wider beach which slow the waves. This gives greater protection from flooding and erosion

Taking material from the sea bed can kill organisms like sponges and corals. It is very expensive defence and has to be repeated.

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

Sand dunes provide a barrier between the land and the sea. Wave energy is absorbed which preventsflooding and erosion. Stabilisation using vegetation is cheap.

The protection is limited to a small area. Nourismnet is very expensive.

Hard Engineering – Man Made structures built to control the flow of the sea and reduce flooding and erosion

Soft Engineering – Schemes set up to work with the natural environment to reduce the effects of flooding and erosion

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Different management strategies can be used to protect coastlines from the effects of physical processes.

Managed Retreat – Involves removing current defences and allowing the sea to flood the land behind it

By removing the current defences and allowing the land to flood behind. Over time the land will become marshland, which then protects the land behind

from flooding and erosion. It is cheap and easy strategy and it not does need maintaining. The marshland can also create new habitat for plants and animals.

Because the land is lost to the sea, choosing areas to flood can cause conflicts e.g. flooding farmland would affect the livelihood of farmer. The saltwater can

also have a negative effect on existing ecosystems

Coastal Management Example – Lyme Regis Dorset

• Small coastal town in the south coast of the UK

• In the World Heritage site know as the Jurassic Coast, it is popular for tourist in the summer where the population of the town goes from 4000 to 15000

• Much of the town has been built on unstable cliffs, the coastline is eroding more rapidly than any in Europe due to the powerful waves from the south

west

• Many properties have been destroyed or damaged and there has been considerable erosion of the shore

• The sea wall have been breached many times

How has it been managed Timeline Benefits Costs

• Lyme Regis Environmental Improvement Scheme set up in 1990s

• Aims were to provide long term coastal protection and reduce the threat of land slips.

• The was completed in 2015

1990+ – new sea wall, £1.4 million emergency project to stabilise cliffs. Nails were used to hold rocks together as well as improving drainage and re profiling the slope of the beach2005-7 – Improvements to sea front coasting £22 million included – new sea wall and promenades, creation of a wide sand and shingle beach to absorb wave energy and increase use of the shore: shingle was dredged from the English Channel and sand imported from France2013-2015 – Focus on the east coast of the town and coast £20million involved – constructing a new 390m seal wall in front of the exiting wall to provide extra protection, extensive nailing, piling and drainage to provide cliff stabilisation to protect 480 homes

• The new beaches have increase the number of visitors and seafront businesses are thriving

• New defences have stood up to recent stormy winters

• The harbour is now better protected,benefiting boat owners and fishermen

• Increase visitor numbers has led to issues with traffic and litter - conflict

• Some people think that new defences have spoilt the natural coastal landscape - -conflict

• New sea wall may interfere with coastal processes and affected neighbouring stretches of coastline, causing conflict elsewhere

• Stabilising cliffs will prevent landslips that may reveal important fossils - conflict

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Fluvial processes: Erosion , Transportation and Deposition

ErosionErosion involves the wearing away of rock and soil

TransportationRivers pick up and carry material as they flow

downstream.

DepositionWhen a river loses energy, it will

drop or deposit some of the material it is carrying.

Hydraulic Action – the force of the water breaking rock rock away from the river channel

Solution - minerals are dissolved in the water and carried along in solution.

Deposition happens when1. Volume of water decreases2. River slows down3. River becomes shallower e.g

inside bend of a meander4. River reaches the mouth

Abrasion – Large bedload rubs against the river channel wear down the river bed and banks.

Suspension - fine light material is carried along in the water.

Attrition – Eroded rocks bump and smash into each other making the bedload rounder and smaller

Saltation - small pebbles and stones are bounced along the river bed.

Solution – River water dissolves some types of rock e.g chalk, limestone Traction - large boulders and rocks are rolled along the river bed.

Vertical Erosion - This deepens the river valley and channel making it v shaped. Mainly happen in the upper course

Lateral Erosion - This widens the river the river valley and channel . Mainly happen in the lower and middle courses.

River Basics• Rivers have three courses• Rivers flow in channels• Banks are the sides of the river

channel• Bed is the bottom of the river

channel• The shape of the valley and

channel changes along the river course; depending on erosion or deposition has taken place,

• Long Profile - shows how the gradient changes from source to mouth

• Cross Profile - shows what a cross section of the river looks like

Upper course

Middle course

Lower course

Mouth

Source

Physical landscapes in the UK: River landscapes in the UK (Paper 1: Section C)

Course Channelshape

Valley shape Cross Profile

Upper Narrow, shallow

V shaped, steep gradient, narrow valley, river takes up valley floor

Middle Wider deeper channel

U shaped, gentle sloping valley sides, valley is wider

Lower Very wide and deep channel

Open U shaped, almost flat, river only takes up a small proportion of the channel

The shape of river valleys changes as rivers flow downstream.

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An example of a river valley in the UK to identify its major landforms of erosion and deposition

The River Tees: A river in north east of England . Its source is in the Pennie Hills near Cross Fell, it flows 128lm to the North Sea at Middlesbrough.

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Upper Middle Lower

Waterfall , Gorge, Interlocking Spurs Landform: Meander and Oxbow lake Landform: Flood Plains and Levee

Waterfall and Gorge1. The river flows over hard rock, under the

hard rock is soft rock. 2. The river erodes the soft rock under the

hard rock, forming a plunge pool. The river erodes through abrasion and hydraulic action.

3. An overhang forms of hard rock. This eventually collapses and the waterfall retreats upstream.

4. Over time the waterfall retreats more and more and this forms a gorge. This repeats, a narrow, steep-sided valley is left where the waterfall used to be.

Meander1. Helical Flow – energy to the outer bend2. Outer Bend – Fast Current –Undercuts –

Erodes – forms River Cliff3. Helical Flow transports sediment to the inner bend,4. Inner Bend – Slower Current – Deposits – forms slip of slope

Oxbow Lake1.Continued erosion of the outer bendnarrows the neck of the meander2.Neck of the meander eventually gets cut through3.River creates new channel (now an old and new channel)4.Deposition happens, separating the new channel

and old channel, Old Meander becomes an Oxbow lake

Flood Plains is a wide valley floor on either side of the river which occasionally gets flooded1. Rivers flood on a regular basis, when rivers flood velocity is slowed

down and deposition of the eroded material that it’s transporting2. This deposition leaves a layer of sediment across the whole

floodplain. (makes it higher)OR 1. Meanders migrate across the flood plain, making it wider and

flattening out the valley floor2. When they reach the edge of the floodplain they erode the valley

side (bluff)Levees1. When a river floods velocity is slowed down and deposition of the

eroded material that it’s transporting2. The largest rocks and most deposition occurs on the banks of the

river channel. 3. This leaves a ridge of higher material next to the river channel on

both banks of the river4. These are known as a levee

Estuaries are found at the month of a river. 1. The land is close to sea level and the river valley is at its widest. The

water here is tidal – the river level rises and falls every day. They are transitional zones between river and coastal and are so affected by wave action and river processes

2. During high tide water is unable to be discharged into the sea, the river velocity falls and sediment is deposited

3. At low tide the wide muddy banks are exposed. 4. At low tide this deposited sediment form mudflats

Interlocking Spurs1.In the upper course the river erodes

vertically. This creates steep sided V shaped valleys.

2.The river is not powerful enough to erode laterally, so they have to wind around the land it cannot erode

3. The hillside that interlock with each other as the river winds around they are called interlocking spurs

Characteristics and formation of landforms formed by rivers

1 2

3 4

Cross sectional diagram of a meander

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Key Terms• Discharge – The amount of water

in the river channel per second. Measured in cubic meters per second

• Precipitation – Rain, sleet, snow and hail

• Infiltration – When water goes into the soil

• Percolation – When water goes into the rocks below the soil

• Surface run off – When water flows across the surface of the land

• Interception – When vegetation (trees) slows down precipitation getting to the soil

• Land Use – What the land is used for. This can increase or decrease flood risk

How physical and human factors affect the flood risk

High Discharge (more surface run off) Low Discharge (little surface run off)

High discharge usually means more surface run off Low discharge usually means little/no surface run off)

High volume of precipitationSnow MeltSteep slopes – if the relief is steep more surface run offSoil Saturation- more surface run offUrban Areas - concrete no less infiltration, more surface run off, Drains take water straight to river.Impermeable soil e.g. clay no infiltration and more surface run off Low/ Prolonged High temperatures, frozen/dry soil, no infiltration more surface run offDeforestation – no interception more surface runoffLand Use – Urban area, impermeable ground like concreteAll - more discharge (more water in the river channel)

Little precipitationFlat land or gentle gradient, if the relief is flat more infiltration less surface run offRural areas – no buildings, no concrete, just soil and vegetation - water infiltrates through soil reducing surface run offVegetation – lots of trees, so interception – less surface run offPermeable soil, more infiltration i.e. sand, less surface run offLand Use – Rural area, treesAll = less discharge (more water in the river channel)

Storm Hydrographs - Graphs that show rainfall and the amount of discharge in a river channel

Storm hydrographs look different depending on the area

This storm hydrography has–Long Lag time, Lower peak discharge, longer rising limbThis is because of - it is likely to be in an area which has one of the following1. Rural area (vegetation/interception) 2. Flat Land3. Permeable soils (sand)4. Porus rock Because less surface run off and less discharge

This storm hydrography has–Short Lag time, Higher peak discharge flow, steeper rising limbThis is because of - it is likely to be in an area which has one of the following1. Urban Area (concrete, drains) 2. Steep gradient3. Non Permeable soils (clay)4. Deforestation 5. Saturated soils 6. Non porus rockBecause more surface run off and more discharge

Key TermsRising limb = The rising flood water in the river

Falling limb = The flood water falling

Lag time = The time difference between the peak rainfall and the peak discharge

Peak Discharge =Maximum discharge in the river Peak Rainfall = Highest amount of rainfall

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The costs and benefits of the following management strategies: hard engineering

Flooding is when a river bursts its banks. This can be down to physical causes such as: prolonged rain, heavy rain, snowmelt, steep gradient, all which cause more surface run off and more discharge. Human causes can be building on flood plains and deforestation.

Hard and Soft EngineeringWe can prevent flood or limit the amount of flooding through Hard and Soft Engineering . Each have there own benefits (+) and cost(-)

Hard Engineering – man made structures built to control the flow of rivers and reduce floodingExamples Dam and reservoir construction - Dams are often built along the course of a river in order to control the amount of discharge. Water is held back by the dam and released in a controlled way. This controls flooding (+). Water is usually stored in a reservoir behind the dam. This water can then be used to generate hydroelectric power (+) or for recreation purposes which creates jobs (+) and encourages tourism (+).Building a dam can be very expensive (-). Sediment is often trapped behind the wall of the dam (-), Settlements and agricultural land may be lost when the river valley is flooded to form a reservoir (-), it an change ecosystems (-). River engineering - The river channel may be widened or deepened allowing it to carry more water this is called River Dredging. A river channel may be straightened, this is called Channel straightening so that water can travel faster along the course. This also means it is harder for rivers to burst its banks (+) Altering the river channel may lead to a greater risk of flooding downstream, as the water is carried there faster (-). It is also very expensive and needs to be re engineering every few years (-)Embankments – Raised walls build along the river bank. The river can hold more discharge so it will flood less protecting the buildings on the flood plain (+. But, it is expensive and if there is severe flooding there will still be damage (-)Flood relief channels – Channels are build that divert the water around important areas or take it elsewhere if the water level gets too high. This prevents river discharge becoming too high and a flood from occurring (+), also gates on the flood relief channels mean the release of water can be controlled. However, there will be increased discharge where the relief channel re-joins the river (or joins another river) which could cause flooding in that area. Also id the water levels get too high in the relief channels, they could also flood.

Soft Engineering - Management that tries to work with the natural river system, e.g avoiding building on flood plains and planting trees to increase lag time..Examples Afforestation Trees are planted near to the river. This means greater interception of rainwater and lower river discharge., reducing flooding (+) This is a relatively low cost option (+), which enhances the environmental quality of the drainage basin (+).Flood Plain Zoning (Planning) control urban development close to or on the floodplain. This reduces the chance of flooding and the risk of damage to property. This is good for a new settlement but there can be resistance to development restrictions in areas where there is a shortage of housing (-). Flood Warning – The Environment Agency warns people about the possible flooding through tv, radio, newspapers of the internet. The impact of flooding is therefore reduced (+), as warnings give people time to move possessions upstairs, put sandbags in position and evacuate so they are not going to get harmed (+).However, warnings do not stop the flood from happening, so damage will still occur (-). Also some people may not hear or have access to warnings (-)/.Preparation – Buildings are modified to reduce the amount of damage a flood would cause. People make plans like an evacuation route, having torches, blankets or sand bags handy. The impact of flooding is reduced as buildings are less damaged and people know what to do (+) also people are less likely to worry (+). However, preparation doesn’t ensure safety and can give people a sale sense of security. Also it is an expensive investment for homes and business to be modified for possible floods. River Restoration – Making a river more natural e.g. so that the floodplain can flood naturally. This is good being less risk of flooding downstream and little maintenance needed (+) it is also good for wildlife (+). However, local flood risk can increase (-)

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An example of a flood management scheme in the UK to show: why the scheme was required, the management strategy, the social, economic and environmental issues

Flood Defence in Cumbria

As you know from your extreme weather example of Cumbria Flood 2009, the towns of Cockermouth and Workington were devastated. The area needed flood management, this was called Cumbria Flood Action Plan. Split into categories: Strengthening defences, Upstream Management, Maintenance and preparing the local people. In total 72million invested in the entire area - Funding from Government and local contributorsThis area of the Derwent catchment (River Derwent.) has been managed by a mixture of soft and hard engineering• £4.6 million spent• River dredged more regularly to deepen the channel - Remove 70,000 tonnes of gravel and debris from local rivers in communities such as Kendal.• Maintain the existing flood walls & flood gate – without these a further 119 properties would be at risk. In total, the Derwent has over 49km of flood walls. New flood

walls raise the channel height to reduce the likelihood of extra floods• New floodgates at the back of houses in Waterloo street• Created 7 new flood warning areas • Restore rivers and flood plains through Flood Plain Zoning• Planting trees

The management of the Derwent has had social, economic and environmental issuesDifferent views on the flood management scheme:

Social Environmental Economic

• People are now more prepared for future flooding• Residents lives have been disrupted by the building

projects• The river has not flooded since, so you can argue

that the flood defence scheme has been a success. Other rivers have flooded in Cumbria

• Some worry the defences will put tourists off the area

• Cumbrian Wildlife Trust: regular dredging destroys has resulted in a reduction in salmon numbers.

• Expensive – some people complain that this money is needed in health care and education in this area. River Dredging has to be done often

• Local business owner: Happy and feels secure that in the future his business will not be disrupted by future flooding. Prevent the loss of income

• Local farmer: Very happy as his fields are now protected from future flooding

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Use a case study to illustrate how rising sea levels will have important social and political consequences for people living in the coastal zone. [8 marks]

Use a case study of a coastal habitat to describe how it has been conserved and discuss how this has led to conflict with other land uses. [8 marks]

With the help of Figure 17, discuss the costs and benefits of using hard engineering to reduce the risk of cliff collapse. [8 marks]

Figure 17

Key

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Buildings Cliffs Road

Cliff line before 1996 Remaining revetments and groynes

Rock armour 2002

Possible extent of erosion by 2105 if nothing is done

N

0 0.5 km

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Location Studland Bay is located in Dorset and is

very popular with tourists. Up to 1.5 million people visit every year. Most tourists arrive by car.

Environmental characteristics o The nature reserve includes sand dunes

and heath. o In this type of environment there is a

unique ecosystem. o The area is internationally important and

is a conservation area managed by the National Trust.

Species that inhabit the area A special grass called marram grass

grows on the sand and holds the dunes together. This allows more vegetation to develop creating a natural heath.

The low shrubs and small trees allow butterflies, insects, small animals and sea bird to survive.

It is the richest 1000 hectares for wildflowers in the country.

The area supports many rare bird such as the nightjar.

The sand lizard is one of the native species.

Issues The nature reserve and sand dune are a

vulnerable environment. The vegetation takes many years to establish.

If the habitat is destroyed the eco-system will break down.

It is home to rare species of plants and birds and all 6 British reptiles.

The area attracts many tourists and gets very busy in the summer.

Visitors need somewhere to park and other facilities such as paths and toilets

Visitors bring problems such as litter.

Strategies to ensure environmental conservation and sustainable use. o Vulnerable areas have been

fenced off to limit access and damage.

o Bird-watching hides and guided walks help visitors to enjoy the wildlife properly.

o No driving on the beach and limited car parking spaces.

o Specific paths have been created to keep visitors off the dunes.

o Jet ski’s are not allowed to be launched from the beach and a 5mph speed limit to reduce the noise.

o Dogs are not allowed on the beach in the Summer.

o Tourists are focused into one area with the facilities such as a shop and toilets.

o Information boards to educate visitors about the wildlife

Coastal habitats – Studland By Nature Reserve

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The UK - Impacts of sea level rise on the coastline The current situation • Sea levels are rising globally. In last 15 years

they have risen on average by 3mm a year. The Intergovernmental Panel on Climate Change (IPCC) predicts a global rise in sea levels of 28 - 43cm by the end of the century.

• Sea levels have changed over millions of years. In the past Britain was actually part of Europe and the North Sea did not exist!

Natural causes of sea level change a) changes in temperature or b) the adding of weight to the Earth's crust. If global temperatures go up = ice melts = oceans expand (thermal expansion) = sea level rise. If global temperatures fall = ice builds up on the land and sea, = oceans contract (thermal contraction), = sea level falls. In the last ice age N. Britain was covered in ice whilst S. Britain was ice free. The north (under ice) was pushed down in to the Earth's mantle slowly because of the weight of the ice causing local sea levels to rise . When the ice melted the weight was lifted off N. Britain causing land to REBOUND upwards and sea level to FALL relative to the rising land. Today in N. Scotland sea levels are falling and in S. Britain they are rising (where population density is highest). Human causes of sea level change Humans release more and more Carbon Dioxide, Nitrous Oxide and Methane into the atmosphere we accelerate Global Warming.

Areas under threat In the UK The South East and East. Here land is flat and at low altitudes. Most people live here. The Norfolk Broads are a large tourist destination (they bring in £5million a year!) and farming area, rising sea level would destroy the area and habitats. London is currently protected by the Thames Barrier, but it is predicted that this barrier will need to be replaced to deal with rising sea levels costing over £80 billion! Valuable agricultural land will be lost . Coastal erosion e.g. Holderness will increase as seas become stormier and waves reach further up beaches and cliff faces. Mudflats such as Keyhaven salt marshes will also be under threat. Settlements such as King’s Lynn will be under threat from sea level rise. Valuable agricultural land such as the Fens is at risk from flooding. Low lying mudflats in Essex would be under threat.

Effects Social – Cliff erosion and coastal flooding will increase in the east causing stress for farmers and homeowners . E.g. The Norfolk Broads, Keyhaven, Holderness. Damage to roads means drivers may loose jobs causing tension within families. Hotel and B and B may have to retrain to can get another career/job. Environmental – Mudflats and Keyhaven salt marshes/Spurn Head will be damaged and in SSSI’s (Sites of Special Scientific Interest) many plants and animals will be at risk. E.g. at Spurn Head birds like the merlin and peregrine. Political- Should government use more hard engineering, and or develop a new Thames barrier ? Economic- The costs financially to families and businesses on the coast if flooding occurs, the cost of a new Thames Barrier, the loss of agricultural land to the farmers and the money the land would generate.

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Page 51: Flooding in an LEDC – Bangladesh floods 2004 Effects€¦ · Flooding in an LEDC – Bangladesh floods 2004 Location Bangladesh is a low lying country that is incredibly vulnerable

Flows- Water moving.

Stores- Water stored.

Inputs- Water coming in.

Outputs- Water leaving.

Interception

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The area of land a river gets its water from. It is defined by the watershed.

An imaginary line marking

out the drainage basin.

The point where two rivers join.

Where the river ends and flows into a sea/lake.

Small rivers which join the

main river.

Where the river starts, usually in an upland

area.

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These processes erode material at the coast and in a river.

Hydraulic action

The force of the water breaks rock particles away from the river

channel/cliff.

Corrasion/Abrasion

Eroded rocks rub against the

channel/thrown against the cliff wearing it away.

Attrition

Eroded rocks picked up by the river/waves

smash into each other.

Corrosion/Solution

River/sea dissolves some types of rock such as chalk and

limestone.

River erosion is affected by: The

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These processes move material at the coast and in a

river.

Small particles are carried along by the

water.

Large particles like boulders are pushed along the bottom of the river bed/sea by

the force of the water.

Soluble materials dissolve in water and

are carried along.

Pebble sized particles are bounced along the river bed/sea by the force of

the water.

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Valley: steep sides, narrow bottom Channel:

Valley: flood plain begins, sides still quite steep Channel:

Valley: wide, flat floodplain with gentle sides Channel:

Upper Middle Lower

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Created when the river flows over an area of hard rock followed by soft rock.

The soft rock is eroded more quickly creating a step.

As the water goes over the step it eroded more and more of the softer rock.

A steep drop is created which is called a waterfall.

1

2

3

4

The hard rock is undercut by the erosion and collapses.

The collapsed rock is swilled around and helps to erode the softer rock in the plunge pool.

Overtime more collapses occur and the waterfall retreats

creating a gorge.

5

6

7

The river eroded vertically downwards creating V-shaped valleys. The rivers are not powerful enough to erode laterally as they have to wind around the hillsides.

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The current if faster on the outside of the bend because the channel is deeper.

Therefore more erosion takes place on the river bend forming a river cliff.

The current is slower on the inside of the bend because the channel is shallower.

So eroded material is deposited on the inside forming a slip-off slope.

1

2

3

4

Erosion causes the outside bends to become closer and the river breaks

through. Deposition cuts off the meander forming an ox-bow lake.

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Levees are natural embankments. During a flood eroded material is

deposited over the flood plain.

The heaviest material is deposited nearest the river channel.

Overtime the deposited material builds up creating levees along the channel edge.

River are forced to slow down when they meet the sea or a lake.

If the sea does not wash away the material it builds up and the channel gets blocked

and is forced to split up.

Eventually the material builds up so much that low lying areas called deltas are

formed. There are three types.

When a river floods onto the flood plain the water slows down and deposits the

eroded material. This builds it up.

Meanders migrate across the flood plain making it wider.

The deposition that happens on the slip off slopes of meanders also helps to build

up the flood plain.

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Upper Course -Source high in the Pennines (893m

above sea level) -High run off as steep V shaped valleys of

impermeable rock -High rainfall – good water supply

-Many tributaries -Famous high fall waterfall – tallest in

England 21 metres high -Gorges, rapids and potholes at Low

force

Middle Course -Clear widening and meandering

-Meanders cut off in the 19th century

-Sides become less steep -Lateral erosion

Lower Course -Very urbanised and large populations. Eg Yarn

-Important wildlife seals & migratory birds also SSSI

-Ox bow lakes -Large oil, gas and petrochemical industries (as flat land)

-Natural Levees formed due to silt build up -Mouth is in the North sea

-Wide Mudflat estuary (tidal) -Huge water sports complex Tees Barrage

River Management -Long history of flash flooding

-Cow green reservoir, controls water supply for industries along the river

-Straighten the river for easier navigation during the industrial revolution

Flood protection schemes in Yarn

85 miles in length

It drains an area of 710

square miles

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Urbanisation

Urban areas have lots of impermeable surfaces such as tarmac. This means the water runs off the surface quickly and to the river.

Deforestation Trees intercept the rainwater. They also take up water. Cutting down the trees increases surface-runoff and therefore the volume of water in the

river.

Geology

If the rock is impermeable water cannot infiltrate and goes to the river.

Relief If the valley is steep the rain just not have a chance to infiltrate and it runs off quickly.

Heavy rainfall Heavy rainfall means that there is a lot of runoff This increases the volume of

water in the river.

Prolonged rainfall After a period of long rainfall the soil becomes saturated, it can’t allow any

more infiltration.

Snow melt

When a lot of snow or ice melts it means a lot of water goes into the river in a short space of time.

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A flood hydrograph shows whether a river has flooded. The lag time shows how quickly the

water reached the river.

When the river has reached its capacity.

When the river flow decreases.

When the river flow increases.

The time it takes for the water to reach the river.

When the rainfall is at its highest.

The normal flow of the river.

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Dams and reservoirs

Very expensive

Flooding downstream

Store water Hydroelectric

power Flow control

Channel straightening

Man-made levees

Flood warnings

Preparation

Flood plain zoning

Flooding may happen downstream as water gets there faster

Water moves more quickly

Catastrophic flooding if levees break

River can hold more water

Don’t stop the flood

LEDC lack of access to radio etc

Urban expansion is limited

No help in places already built on

Does not mean safety

Expensive to modify buildings

Risk of flooding reduced

Impermeable surfaces not created

Impact of flood reduced

People know what to do

Impact of flooding reduced

Evacuation

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• River flooding in the UK seems to be happening

more often. • Some rivers in the UK

have been flooding more frequently over the last

20 years. • Example: the River Ouse

in Yorkshire reached a high level 29 times

between 1966 and 1986. But between 1987 and

2007 it reached the same level 80 times!

Year Rivers Places affected

1988 Kenwyn Cornwall

1990 Severn Gloustershire

1994 Lavant, Clyde West Sussex, Glasgow

1998 Severn, Trent Wye The Midlands, Mid and South Wales

2000 Ouse, Alyn Yorkshire, North Wales

2004 Valency (Boscastle) Cornwall

2005 Eden Cumbria and North Yorkshire

2007 Many Many parts of the UK

2008 Severn South Midlands

Locations and dates of the big floods in the UK

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Reasons for the flooding

PHYSICAL -A very wet August (2 times average

rain) SO the ground was already saturated

-Impermeable rocks & thin soils -Steep slopes – rapid runoff

-Confluence of Rivers Valency & Jordan is just above the village

-A very high tide – made it difficult for water to flow out to sea

HUMAN

-Bridges were low so acted a a dam - debris such as tree trunks caught on

them water piled up until it burst through in a great wave

-Many buildings & roads were positioned close to the river so more

property damage

Primary Impacts -50+ cars, and caravans were

swept out to sea -a wall of water swept through

the village destroying everything in its path

-6 buildings were swept away -Many other houses, shops etc

were flooded, with mud + sewage as well as water; possessions also ruined

-Roads under 2.75m of water -No deaths, few serious injuries

Secondary Impacts -90% of economy dependent on tourism > lost money >20 accommodation providers & tourist

attractions/shops forced to shut -Insurance companies pay out £20 million

New Management & defence -£4.6m scheme includes: raise car park to safer level; move & raise bridge; widen & lower the river bed to

increase the amount of water it can hold -Removing of dead vegetation to stop blocking of the

river -‘At risk’ properties – encouraged to use more flood resistant material, raise height of electrical wiring etc

-Environment Agency – flood warning system + information

-Council runs special advice days, encouraging people to have an emergency evacuation

pack & to take out insurance. Council has an emergency action plan.

Since 2004 – flooding again, still damage but not as

damaging as this event

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Characteristics of Bangladesh

-Lays mainly on floodplains, so flat land Most of the land lies 6metres below sea -3 main rivers- The Ganges, Brahmaputra and Meghna. -Monsoon season evey year – high concentrated rainfall in a few months (June to September). -1,800mm and 2,600mm rain a year. -Poverty is a huge issue in Bangladesh-low literacy rate -Flooding occurs naturally in Bangladesh -Snow from the Himalayas melts each year and increase river discharge -Sediment blocks up the river and causes flooding -Deforestation in the forest increases run off and reduces lag time -Cyclones occur in the Bay of Benegal and causes coastal flooding -Densely populated areas meaning increase in deaths

Social impacts -36 million people were made

homeless -People died as a result of

disease because they had no access to clean water.

-Impacted on rural farmers and urban slum dwellers the

most. -Over 800 died with many

more from disease

Economic impacts -serious damage to infrastructure – roads,

bridges, embankments, railway lines, irrigation systems

-All domestic and internal flights had to be suspended during July

-Value of damage was assessed as being in region of $2.2 billion of 4% of total GDP for

2004

Environmental impacts During July and August

approximately 38% of the total land area was flooded including 800,000 ha of agricultural land

and Dhaka Floods caused river bank

erosion especially on embankment areas close to the

main channels, soil erosion, water-logging, water

contamination

Response and management -Reliance on Ngo support – financial and

emergency supplies –UN disaster management support

-Self help schemes promoted -local community early warning system

implemented, plus shelters -Increasing use of levees to protect field and

villages -Increasing monitoring to reduce the impact

as happens every year.

-encourage farmers to build homes on stilts.

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Enough water? o In England and Wales there is only 1334 cubic meters

of water available per person per year- half the amount hotter countries such as Spain have.

o In the Thames Valley there is only 266 cubic meters per person.

Why is there water stress? Water stress= amount of water available is not enough to meet demand. o The UK is a crowded island and we are not evenly

spread out. o Rainfall does not fall evenly. o Population and rainfall issues cause areas of deficit

(not enough) and surplus (too much). o The UK’s population is growing and more people =

more housing = more demand for water o By 2020 the demand for water could be 5% higher

than today.= 800 liters of water a day. o As the temperature rises because of global warming

drought could become more frequent.

Example

West wales has a low population density but high rainfall so they have a water surplus.

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Kielder Water fact file Located in Northumberland it is the biggest

man-made reservoir in northern Europe. It is 2km and 52m deep. It cost £167 million and was completed in

1982. It was built to meet the increasing water

demand from north-east England which was to be caused by the increasing population and growth of steal and chemical industries (which have actually declined).

It is a water transfer scheme (water moved from one area to another).

The water from the reservoir is released into nearby rivers such as the Tees when they are low.

The water is also released for extra household and industrial use.

It can provide up to 909 million litres of water a day.

Social impacts

o The north-east now has the most reliable water supply in England.

o Reduced risk of droughts and therefore the measures that come with this.

o Only a few families had to be moved and re-housed when the reservoir was built.

Economic impacts

o Kielder Water has become a major tourist attraction. This has created jobs and the local economy.

o Forest park around Kielder Water is harvested for timber and employs about 200 people.

o The reservoir and dam requires maintenance which costs money.

Environmental impacts

o If pollution occurs downstream then clean water can be released to dilute and flush it out to sea.

o The water is used to generate hydroelectric power at the Kielder Dam.

o The release of fresh clean water into the the River Tyne has encouraged salmon and sea trout to breed.

o The creation of the reservoir disturbed wildlife.

Sustainable supplies The environment agency thinks our water can be made more sustainable by: a) Consider the needs of the environment,

wildlife, fisheries and recreation when allocating water supplies.

b) Share water resources where there is a surplus.

c) Make appliances that are more water efficient.

d) Reduce water leakage from pipes and reservoirs.

e) Make new homes more water efficient. f) Increase the use of rainwater harvesting and

grey water recycling for agriculture, industry and commercial use.

g) Charge more for water to encourage people to use only what they need.

h) Install water meters in all homes so people are charged for what they use.