Unit 1: Water on the Land

Check list

ü  Do you know the hydrological cycle?

ü  Do you know the processes of erosion, transportation, and deposition?

ü  Do you know how the long profile and cross profile of a river change?

ü  Do you know how the features of the upper course such as v-shaped valley, interlocking spurs and waterfalls are formed?

ü  Do you know how the features of the middle course such as meanders and oxbow lakes are formed?

ü  Do you know how features of the lower course such as floodplains, levees deltas and estuaries are formed?

ü  Do you know the advantages and disadvantages of different types of hard and soft management strategies?

ü  Do you know the causes, effects and responses are to the Boscastle and Bangladesh floods?

ü  Do you understand the way that water is managed in the UK?

The Hydrological Cycle

 

The hydrological cycle or the water cycle is the continuous movement of water above and below the earth’s surface.

 

BBC Class Clips

Rivers begin in upland areas and make their way to the see draining all the precipitation from that area. You can see an image of the drainage basin below. 

 

• Drainage basin - the area drained by one river


• Source - The beginning of the River


• Wartershed - An area of high land between two drainage basins 


• Confluence - Where two rivers meet 


• Tributary - A smaller river which runs into a larger river

Hydrographs

A hydrograph is a graph which shows how the water flows within a drainage basin. The line always shows the discharge in a river measured in cumecs, the bar graph shows the amount of precipitation in mm. 

 

The graph varies dependent on a number of factors including size, shape, precipitation event, geology and the use of the basin. These factors affect the lag time (time taken for the precipitation to enter the river) and how steep the rising and falling limbs are.

 

Size of the basin - the larger the basin is the longer it will take the water to reach the trunk and therefore the lag time will be longer.

 

Geology - if the basin is made from a permeable material which allows the water to infiltrate e.g. chalk then the lag time will increase and the rising limb will be more gentle as the water takes longer to move as throughflow. If the basin is made from an impermeable rock such as granite the hydrograph will be much more flashy as the water will move quickly as surface runoff into the river. 

Gradient - steep slopes will allow water to flow more quickly overland and water is less likely to infiltrate therefore it will have a shorter lag time than a gentle slope. 

Urbanised basin - before urbanisation there is vegetation across a basin, this means water can be intercepted by trees, can infiltrate the soil and either move towards the river by throughflow or be taken up by the trees. These basins tend not to have flashy hydrographs and have a long lag time. Once urbanised the area will be covered with concrete, this is impermeable, the water will therefore move overland straight into rivers. There are also drains within urban areas which move water to rivers very quickly. All of this gives urban areas a short lag time and a steep rising limb. 

Precipitation event - If the precipitation event is a snow event the lag time will be very long as we have to wait for the snow to melt. However, once the snow melts you generally will see a steep rising limb as the water suddenly melts and often cannot infiltrate as the ground below is still frozen. 

The following graphs show the variations in hydrographs: 

 

 

River Processes

Erosion is the break down and removal of rock.

• Hydraulic Action: - the water forces air into the cracks and weaknesses in rocks, this acts like mini explosions forcing the rocks apart. 


• Abrasion: - the river current picks up rocks and sand and rub them against the river banks and bed (like sandpaper)


• Attrition: - rocks that are carried by the river hit into each other breaking chunks off making the bedload rounder and smoother


• Solution: - the chemical properties of the river water make it more acidic, this dissolves some types of rock e.g. chalk

 
River Transportation
Rivers pick up and move material there 4 main processes: -  

Deposition 
When a river loses energy the material that the river carries is dropped, this is deposition. Deposition occurs when the water becomes shallower or the volume of water decreases. Deposition is common in the lower course of the river. 

River long profile
The river changes it's characteristics and landforms from source to mouth. This journey can be seen through the long profile of a river which is split into three sections, upper, middle and lower course. 



 
BBC Class Clips
BBC Class Clips 

Upper Course

 

The upper course of a river can be characterised by;

 

•  steep v-shaped valley


•  interlocking spurs


• waterfalls


•  small, narrow river channels


• low velocity


• high friction


• large angular bedload 


• vertical erosion

 

Upper Course Feature  - V-shaped valley formation

 

 

Upper Course Feature - Waterfall formation

 

 

Middle Course Features - Meander Cross-section

 

In the middle course of the river meanders form as erosion moves from vertical to lateral.

 

The current flows faster on the outside of the bend  causing erosion forming a river cliff and slower on the inside where deposition takes place and a slip-off slope is formed.

 

Birds eye view of a meander

BBC Class Clips

 

Oxbow lake formation

Meanders get larger over time and in times of flood can form ox-bow lakes.

 

Lower Course Feature - Floodplain

 

The floodplain is the wide flat area at the valley floor. This area occasionally floods. When it does the energy of the water reduces and the river deposits alluvium which builds up the floodplain. As the rivers meander across the floodplain they make the floodplain wider.

 

 

Lower Course Feature - Levees

 

Levees are natural embankments along the river edge. They form in a similar way floodplains: -

 

 

Exam Question

1. Using a diagram describe the formation of a waterfall. (4 marks)


2. Describe the formation of an oxbow lake. (6 marks)


3. Describe the formation of a meander. (4 marks)


4. Describe the formation of a levee (4 marks)


5. Describe the formation of a floodplain. (4 marks)


6. Describe the processes of erosion. (3 marks)


7. Describe how the river transports its load. (3 marks)


8. Draw a labelled cross section to show the difference between the inside and outside of a river meander. (4 marks)


9. Explain the reasons for variations in hydrographs. (4marks)

 
 

 

Case Study: Boscastle

Location: Boscastle, N. Cornwall; Rivers Valency & Jordan

Date:  16 August 2004

Causes: immediate: 

a flash flood following fall of 50mm rain in one hour, 125mm in a few hours; this resulted from warm moist air moving onshore meeting air moving overland from the SW ~ air was forced to rise rapidly, forming thunder clouds 10 km high over Bodmin Moor – as air rose, it cooled, water vapour condensed into water droplets and huge amounts of intense - very heavy - rain fell.

 Causes:

o   A very wet August (2 times average rain) meant that the ground was already saturated; water couldn’t be absorbed so rapidly entered the rivers as surface run-off.

o   Impermeable rocks & thin soils increased surface run-off.

o   Steep slopes – rapid runoff

o   Narrow, steep sided valley – nowhere for water to overflow

o   Confluence of Rivers Valency & Jordan is just above the village, with a third tributary joining lower down – so water from all 3 poured through the village

o   A very high – ‘spring’ tide – made it difficult for water to flow out to sea

o   The short lag time until peak discharge and the rapid rise in river levels resulted in a flash flood with 100 x the normal river discharge flowing through Boscastle 20 mins after the storm began.

 

Effects: immediate:

o   a wall of water swept through the village destroying everything in its path

o   50+ cars, and caravans were swept out to sea

o   6 buildings were swept away eg Wellington Hotel, others were badly damaged eg  Witchcraft Museum

o   Many other houses, shops etc were flooded, with mud + sewage as well as water; possessions also ruined.

o   Bridges swept away

o   Roads under 2.75m of water

o   Damage to sewers/water/electricity supply

o   Boulders & trees swept through streets

o   People onto rooftops & trees to escape water

o   No deaths, few serious injuries

 

Effects: longer term:

o   90% of economy dependent on tourism – lost for rest of 2004 & probably to some extent in following year - 20 accommodation providers & tourist attractions/shops forced to shut

o   cost of building & infrastructure repairs, clean up, new river defence works

o   cost to insurance companies - & premiums probably rose

o   psychological effects

 

Response: immediate:

o   Emergency services – 6 helicopters, 2 lifeboats called out; fire, police & ambulance services also involved.  Included searching harbour & sunken cars

o   150 airlifted to safety; many others evacuated.

o   emergency centres opened  in nearby villages

o   sandbags

 

Response: longer term: 

o   clean-up operation began within a few days

o   repairs – aiming to be ready for tourist season 2005

o   new defences- £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 ( earlier suggestions included re-routing the river – but rivers tend to return to their ‘natural’ route, or putt5ing it through a conduit)

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

o   Environment Agency – flood warning system + information

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

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

Watch the case study video: -

 

Case Study: Bangladesh

Bangladesh - Fact File

• Is one of the world's most densely populated countries!
• has a population of 125m inhabitants
• is one of the poorest countries in the world with a GNP of $200 per head
• has three of the world's most powerful rivers passing through its country - The Ganges, the Meghna & the Brahmaputra
• contains virtually no raw materials or rock
• experiences floods and tropical storms every year

 

 

The Physical Causes of the Floods

·         Most of the country consists of a huge flood plain and delta

·         70% of the total area is less than 1 meter above sea level

·         10% of the land area is made up of Lakes and Rivers

·         Snowmelt from the Himalayas takes place in late spring & summer

·         Bangladesh experiences heavy monsoon rains, especially over the highlands

·         Tropical storms bring heavy rains and coastal flooding

The Human Causes of the Floods

- Deforestation in Nepal and the Himalayas increases run off and adds to deposition and flooding downstream

-   Urbanisation of the flood plain has increased magnitude & frequency of floods

- the building of dams in India has increased the problem of sedimentation in Bangladesh

-The main cause was the above average & long period of heavy rain which caused all 3 rivers to have their peak flow at the same time!!!

- Poorly maintained embankments (levees) leak & collapse in times of high discharge

- Global warming is blamed for sea level rise, increased snow melt & increased rainfall in the region 

 

The Effects of the 1998 Floods ·         Over 57% of the land area was flooded ·         Over 1300 people were killed ·         7 million homes were destroyed ·         25 million people were made homeless ·         There was a serious shortage of drinking water & dry food ·         Diseases spread such as bronchitus and cholera/diarrhoea ·         As the waters receded - it left fields of rotting crops, wrecked roads and bridges and destroyed villages ·         2 million tonnes of rice was destroyed ·         1/2 million cattle and poultry were lost ·         Overall the floods cost the country almost $1 billion

Flood Management in Bangladesh In 1989  the government of Bangladesh began working with a number of international agencies to produce a Flood Action Plan. This huge scheme contained 26 action points which it was hoped would provide a long term solution to the country's flooding problems.

Short Term Management

·         Boats to rescue people

·         Emergency supplies for food, water, tents and medicines, aid from other countries  

·         Fodder for livestock

·        Repair and rebuild houses, as well as services such as sewage etc.

 

Long Term Management

·         Reduce Deforestation in Nepal & Himalayas

·         Build 7 large dams in Bangladesh to store excess water $30-$40 million and 40 yrs to complete

·         Build 5000 flood shelters to accommodate all the population

·         Build 350km of embankment - 7 metres high at a cost of $6 billion to reduce flooding along the main river channels

·         Create flood water storage areas

Develop an effective Flood Warning Scheme

 

 

Flood Defences - Hard and soft engineering 

Hard	Advantages	Disadvantages
Embankments (levees) – these are high banks built on or near riverbanks.	They stop water from spreading into areas where it could cause problems, such as housing. They can be earth and grass banks which blend in with the environment.	Flood water may go over the top. They can burst under pressure, possibly causing even greater damage.
Channalisation – this involves deepening and or straightening the river.	This allows more water to run through the channel more quickly, taking it away from places at risk.	More water is taken further downstream, where another town or place is at risk might lie. They do not look natural.
Dams – these can be built upstream to regulate the flow of water.	Water is held back during times of heavy rain or snowmelt. They can also be used for water supply, recreation and HEP.	They can be an eyesore and are very expensive to build. If they burst the damage would be devastating.
Flood Relief Channels – extra channels can be built next to rivers or leading from them.	These channels can accommodate the surplus water from the river so that it won’t overflow its banks.	They can be unsightly and may not be needed very often. Costs can be high.

  

Soft	Advantages	Disadvantages
Flood plain zoning –restrictions prevent building on parts of the flood plain that are likely to be affected	The risk of flooding is reduced as impermeable surfaces aren’t created.   The cost is reduced as buildings and homes aren’t damaged	Restricts the urban area limiting what can be done in certain areas.   It cannot be done in settlements which are already well developed.
Flood warnings – the Environment Agency warns people on TV and internet.	Gives people enough time to move valuables and them selves to safety reducing costs and deaths.	Does no stop the flood from happening.   People may not hear the warnings.
‘Do Nothing’‘	Natural   The river floods, eroded material are deposited creating fertile farmland.	A flood can cause a lot of damage,   Cheap

 

Case Study: Three Gorges Dam

 

The Three Gorges Dam is built on the Yangtze River in China. It is a huge structured designed to control the flow of water after the 1998 floods which caused wide spread devastation across southern China and the Yangtze River. It was estimated that the flooding cost $20 billion (US).  

 

Positives: -

• Controls flood water
• Provide jobs in the building and maintenance of the dam
• Provide HEP (China is very relent on coal) - this was a more realiable form of electricity which attracted industry.
• Put China on the "world stage". It showed they were able to build the structure

 

Negatives: -

• millions of people were displaced (forced from their homes)
• increase in landslides due to the pressure of the water on the slopes and deforestation higher up to make room for farming.
• an area the size of the Grand Canyon was  flooding destroying culturally important temples and artifacts and destroying habitats.
• It has made the river harder to navigate

Case Study: Darlington

River Skerne, County Durham

The Skerne demonstration site is located in the town of Darlington, County Durham and demonstrates what can be achieved in an urban environment. The Skerne has been straightened and enlarged to reduce flooding and to drain the surrounding urban area. Much of the floodplain has been raised by old industrial waste tipping, with gas and sewer pipes running alongside the river. As a result of these constraints, restoration opportunities were severely limited - typical of urban rivers elsewhere.

A 2km length of the river has been restored. Four new meanders have been formed in a remaining section of floodplain used as open parkland. The excess soil was used to landscape nearby steep slopes. Riverbanks have been strengthened with willow and reeds to prevent erosion. Thirteen ugly surface water outfalls have been replaced with underground inspection /collection chambers that firstly intercept pollution and then discharge the water into the river below water level.

Elsewhere, where the river could not be re-meandered, it has been enhanced by reshaping and narrowing the bed to vary the flow and to allow riverside plants to flourish. New footpaths and planting schemes complete the theme of "bringing the countryside into town", which locally has been greatly appreciated.  

 

Water Management in the UK

 

What is drought?

Most of us think of droughts as when there's no rain at all. But actually they can happen when there's less rain than people thought there would be.

It usually happens over months or even years, when an area, like East Africa, doesn't have a big enough water supply.

Unlike other natural disasters, droughts happen very slowly over time.

 

 

What are the effects of drought?

Droughts can be very dangerous for people in living in areas with not enough food or water. Deaths can happen from lack of food and water, and there are lots of health problems too.

When there's not enough water, crops fail, which means there isn't enough food to go around.

It also means that farmers lose money, and the area can become very poor.

When a region is very poor and doesn't have enough food or water, arguments can happen over who should be able to access the goods, which can escalate into wars.

 

 

National Scene

 

The UK is highly variable in terms of water supply and demand. A lot of the rainfall received by the UK falls in the North and West, whereas most people live in the South East. This means that the North and West of the British Isles are WATER SURPLUS areas, whilst the south east is a water shortage area.

The North and the West receive more rainfall because the bulk of our weather comes from the South West with our prevailing wind. This brings moist air because the air is warm and has travelled a long way over the Atlantic Ocean. The wet areas also coincide with our highland areas, as the wet incoming air is forced to rise over these hills, and as it does so it cools, condenses and forms clouds and then rain. These patterns are clearly visible on the maps below;

 

 

In the UK we use between 124 and 177 litres of water a day. It is expected that demand for water will increase due to an increase of households and populations in certain areas (population is expected to reach 66 million by 2031). A more affluent life style increases demand for water as we buy more time-saving goods. We also demand food stuff out of season, which contribute to an increase in overall use of water.

There is a need to ensure that demand can be met in a sustainable way. A focus on local schemes is one way of ensuring this, rather than large scale  transerfs of water. Encouraging conservation is a strategy: -

-       Houses are being designed with better water efficiency

-       Devices are fitted to toilet cisterns to reduce water use.

-       Collecting rainwater

-       Bathwater can be recycled

-       More people take showers than baths

-       Use water meters

Key Terms

Water stress: this occurs when the amount of water available does not meet that required. This may be due to an inadequate supply at a particular time or it may relate to water quality.

 

Areas of deficit: The locations where the rain that falls does not provide enough water on a permanent basis. Shortages may occur under certain conditions e.g. long periods without rain.

 

Areas of surplus: areas that have more water than is needed – often such areas receive a high rainfall total, but have a relatively small population.

Case Study: Water Management - Kielder Water

The North East of England is highly variable in how much precipitation it receives. The main cities (Newcastle, Sunderland etc) and towns (Middlesbrough) are on the East coast, one of the driest places in the British Isles. To combat this Northuimbria water, the company responsible for water supply in the North East, have constructed Kielder Water. Kielder water is a management scheme designed to store water for the North East of England. It is run by Northumbrian Water, a large company supplying Northumberland, County Durham and parts of North Yorkshire and Cumbria.

The Kielder Water reservoir is in the North west of the region, so is in a high precipitation zone, and water is then piped and run through rivers to the cities that have a shortage of water in the East. The differences in water received are clearly marked on the graph below, and the area in which Kielder is in receives 1700mm of rain a year, whilst Newcastle receives only 644mm!

The main conurbations served by the reservoir are Tyneside, Wearside and Teesside. The reservoir is linked to the exit point of the Derwent Reservoir in County Durham, with a pipeline fed from the North Tyne river below the Kielder dam. The Derwent Reservoir remains the primary source of water for Tyne and Wear, so water from Kielder can be used to supplement the flow of the River Derwent when the reservoir above is at low levels, and also to provide water into the Derwent Reservoir's distribution system. The Kielder pipeline cannot be used to supplement the water supply to the Derwent Reservoir itself.

 

The decline of traditional heavy industry, together with more water-efficient industrial processes and better control of water supply leakage, served to undermine the original reasons for the reservoir and many came to criticise the government-funded project as a white elephant.

In recent years, however, Kielder Water has come into its own, with underground springs ensuring that it always remains at high levels, regardless of the prevailing climate condition. This means that while the south of England is often forced to implement drought strategies and hosepipe bans, north east England enjoys plentiful water supplies

 

Why was the reservoir built?

·    planned in the late 1960s to satisfy an expected rise in demand for water to support the increasing industrial economy

 

 

Which areas benefit from the scheme?

·     Tyneside and Cleveland

·     major cities: e.g. Newcastle, Sunderland, Durham, Darlington, Middlesborough

 

How is the water transferred to these areas?

·     by aqueduct - Airy Holm, Frosterly, and Eggleston

·     Airy Holm transfers water 39km to Frosterly

·     Frosterly outlet - water is released into the Wear

Eggleston Outlet - watter is released into the Tees

 

 

What were the effects of the reservoir being built?

Benefits:

-    created an income through tourism

-    provides a reliable water source

-    provides hydro-electric power (HEP)

-    the river downstream of the dam is not likely to flood towns

-    new habitats created

Problems:

-   scheme involved conservation areas

-   habitats ruined or destroyed

-   people had to be relocated to new homes

-   road network affected for local villages

 

The scheme was multipurpose from the beginning: HEP, water supply, leisure, conservation

Did the water transfer scheme prove to be successful?

·     YES

·     in 1995 droughts, reservoir at Kielder Water provided above major cities with a constant supply of water

·     the north-east receives the amount of water it needs due to Kielder Water while the southeast still suffers under hosepipe bans

 

Watch the summary video of Kielder Water: -

 

 

 

Exam Questions

 

1. Using a case study describe the responses to a flood. (6 marks)
2. Using a case study describe the effects of a flood. (8 marks)
3. Compare the responses between a flood in an developed country and a developing country. (8 marks)
4. Describe the advantages and disadvantages of soft engineering as a means of controlling flooding. (8 marks)
5. Explain how the demand for water is met within the UK. (8 marks)