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Welcome to Year 11!

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Title: Welcome to Year 11!


1
Welcome to Year 11!
  • Plan of attack!!

2
As most of you are aware
  • We covered 2/3 of each unit last year (and in the
    case of Rivers, more than that).
  • So we still have 4 weeks each for most units
    (except Rivers which has 3).
  • As you will see, each unit as per the syllabus is
    divided into 3 broad questions, and in most cases
    (exc r) we have covered 2 of them.
  • So this is the general trend
  • Week 1 review section 1
  • Week 2 review section 2
  • Week 3/4 - complete section 3 and look at exam
    type questions

3
The next 3 weeks Rivers
  • Key question 1 The worlds water supply is
    contained within a closed system the
    hydrological cycle. Water is transferred between
    its various stores.
  • Key Question 2 Running water has a significant
    influence on the development of landforms
  • Key Question 3Water is vital to people, varies
    in availability and therefore needs careful
    management.

4
Rivers week 1
  • Key question 1 The worlds water supply is
    contained within a closed system the
    hydrological cycle. Water is transferred between
    its various stores.
  • Essential content
  • The hydrological cycle characteristics, stores
    and transfers.
  • Features of a drainage basin watershed, source,
    mouth, channel network.
  • The hydrograph (discharge, base flow, stormflow)
    and river regimes
  • factors affecting them (precipitation,
    temperature, water abstraction, dams).

5
Rivers- week 2
  • Key Question 2 Running water has a significant
    influence on the development of landforms
  • Essential content
  • Processes weathering and mass movement erosion
    and deposition.
  • Factors affecting these processes (stream
    velocity, slope, geology).
  • Formation of valleys, interlocking spurs,
    waterfalls, meanders, oxbow lakes, flood plains
    and levees.
  • Practical skills
  • Measuring channel features measurement
  • Annotated sketches based on photographs.

6
Rivers- week 3
  • Key Question 3Water is vital to people, varies
    in availability and therefore needs careful
    management.
  • Essential content
  • The uses of water agriculture, industry, human
    hygiene and leisure including the reasons for a
    rising demand resulting in areas of water surplus
    and water shortage.
  • Reasons for differences in water quality. Sources
    of pollution (sewage, industrial waste,
    agriculture). Managing the supply of clean water
    (dams and reservoirs pipelines treatment
    works).
  • Flooding causes (intensity of rainfall,
    snowmelt, steep slopes, impermeable surfaces,
    human activities) and control (construction of
    spillways, embankments).
  • Practical skills
  • Measuring water quality
  • Case Studies
  • Case study of the rising demand for water in one
    country.
  • A case study of a dam or reservoir project.
  • A case study of a flood defence scheme.

7
The hydrological cycle characteristics, stores
and transfers.
Recall, a cycle goes round and round, so there
are no inputs and no outputs
8
Features of a drainage basin watershed, source,
mouth, channel network.
This is one worth learning to draw
9
Features of a drainage basin watershed, source,
mouth, channel network.
  • The Tees is a river in Northern England. It rises
    on the eastern slope of Cross Fell in the
    Pennines, 750m above sea level, and flows
    eastwards for about 137 km to reach the North
    Sea. It drains an area of 1834 square km and has
    no important tributaries.

10
A variation on the hydrological cycle
It has items entering the system INPUTS
It has items leaving the system OUTPUTS
  • Can be called the hydrological system of a
    drainage basin or drainage basin system it is
    no longer a cycle, so

11
The hydrological system of a drainage basin
characteristics, stores and transfers.
Here it is with the different processes analysed
by function
12
The hydrograph (discharge, base flow, stormflow)
and river regimes
  • Recall that hydrographs measure the discharge of
    a river at particular point over time. The
    discharge is measured in cumecs, that is the
    number of cubic metres passes a particular point
    in a second this is an annual hydrograph and
    shows the river regime

Why does the discharge change in summer?
  • But there is another particular sort of
    hydrograph the storm hydrograph this combines
    the rainfall with discharge and is used to
    explore the impact of one on the other

What might you see if the river passes through an
cold area in winter?
13
The hydrograph (discharge, base flow, stormflow)
and river regimes
  • Please note that understanding and being able to
    use all these terms is essential

14
The hydrograph (discharge, base flow, stormflow)
and river regimes
  • A Hydrograph has a number of main
    characteristics
  • Precipitation shown as a bar graph
  • Base Flow flow supplied by groundwater. This
    is a slow movement therefore base flow rises
    slower and later.
  • Storm Flow flow supplied by overland flow and
    soil throughflow. This gives the peak flows.
  • Rising Limb is the angle of the rise towards peak
    discharge includes
  • (a) rainwater that fell into stream
  • (b) water flowing overland and into stream
    channels as the soil water becomes saturated.
  • (a) (b) lead to peak discharge.
  • Lag Time the time it takes from peak rainfall
    to peak discharge.

15
Factors affecting storm hydrographs
  • The shape of the rising limb depends on
  • The length of the rainstorm a long period of
    rainfall causes rise in the water table and
    increased overland flow.
  • The intensity of rainfall
  • If heavy considerable storm flow if the soil is
    incapable of soaking it in and storing it a steep
    rising limb.
  • If light less steep rise and flatter shape
    since rain is easier to store.
  • The condition of the soil If the soil is
    already saturated more water flows overland into
    streams and this leads to a higher and earlier
    peak.
  • Shape of the drainage basin - a long narrow basin
    with tributaries joining the main channel at
    regular intervals gives a less steep rise
  • A wide basin with tributaries more closely spaced
    gives a steep rise.

16
Factors affecting storm hydrographs
  • Lag Time the difference in time between peak
    rainfall and the peak discharge. Lag time
    depends on
  • The condition of the soil if the soil is fairly
    dry, the longer the lag time since rainfall can
    be stored at first before the excess flows to the
    channels.
  • Angle of slopes the more gentle the slope the
    longer the lag time compared to steep slopes.
  • Intensity of rainfall prolonged, steady
    rainfall has a longer lag time than intense
    rainfall.
  • Size of drainage basin small basins have a
    small lag time larger basins with more
    tributaries have a longer lag because the
    tributaries act as temporary storage before
    run-off increases rapidly.

17
Factors affecting storm hydrographs
  • Five other issues
  • 1. What effect do you think of having trees
    growing on the river banks as against grass or
    maybe soil or just rocks, on
  • the rising limb?
  • the lag time?
  • the peak flow?
  • 2. What effect do you think of having concrete
    and tarmac in a town as against parks and
    gardens, on these factors?
  • 3. What effect do you think permeable underlying
    rock will have when compared with impermeable
    underlying rock?
  • 4. Time of year what effect would a warm summer
    day have on the 3 variables? A period of heavy
    snow? A winter time with plenty of rain above
    freezing?
  • 5. What about human control building a dam for
    example? Or an industry extracting water for its
    processes, like steel manufacture?

18
Factors affecting storm hydrographs
  • Green or blue, because
  • Heavy rainstorm
  • All these form now on have several hours of
    steady rain
  • Tree-lined river banks
  • Small drainage basin
  • On impermeable rock
  • On saturated soil
  • On a river in which there is a reservoir upstream
    from the point of measuring
  • On steep sloping river course
  • On river running through ploughed land in autumn
  • On impermeable rock
  • River system A
  • A large drainage basin
  • On a river that is downstream from where
    extraction (for industrial purposes) takes place
  • River system B
  • On dry soil
  • On gently sloping river course
  • On a river through a town

19
Rivers- week 2
  • Key Question 2 Running water has a significant
    influence on the development of landforms
  • Essential content
  • Processes weathering and mass movement erosion
    and deposition.
  • Factors affecting these processes (stream
    velocity, slope, geology).
  • Formation of valleys, interlocking spurs,
    waterfalls, meanders, oxbow lakes, flood plains
    and levees.
  • Practical skills
  • Measuring channel features measurement
  • Annotated sketches based on photographs.

20
River Processes that change the landscape include
  • Weathering and mass movement
  • Erosion
  • Transportation and
  • Deposition.
  • The first one was never really covered last year,
    but the other 3 were in some depth.
  • Since I found some really good piccies of this
    first one I have borrowed it complete!

21
Weathering and Mass Wasting
  • Physical or mechanical Weathering
  • Chemical Weathering
  • Mass Wasting

22
Weathering and Mass Wasting
weathering is the combined action of physical
weathering, in which rocks are fractured and
broken, and chemical weathering, in which rock
minerals are transformed to softer or more
soluble forms
23
Physical Weathering
  • one of the most important physical weathering
    processes in cold climates is freeze-thaw , the
    repeated growth and melting of ice crystals in
    the pore spaces of soil and in rock fractures
  • when water freezes in bedrock joints and bedding
    planes, it expands and can split rocks apart

24
Physical Weathering
Exfoliation where there is a large diurnal
(daily) range of temperature, the rocks expand in
the daytime and contract at night. This causes
the rock surface to weaken, producing rounded
rock forms
  • Exfoliation of Granite

25
Chemical Weathering
  • Involves change in the composition of the rocks.
  • Water or slightly acid rain reacts with the
    chemicals in the rock, which is then dissolved
    away.
  • In the case in the picture, acid rain is reacting
    with limestone on exposed surfaces.

26
Chemical Weathering and its Landforms
Marble
Slate
27
What is mass wasting?
  • Once rock has been loosened by weathering, it may
    start to move down hill under gravity.
  • This means that the steeper the slope is, the
    faster it happens.
  • If it is slow, then you get soil creep.
  • Faster and you get more dangerous mudslides,
    often brought on by heavy rain.
  • When a greater volume of loose material is
    involved this can lead to land slides

28
Mass Wasting
Figure 14.13, p. 490
29
Mass Wasting Soil Creep
30
IG4e_14_opener
An example of mass wasting - mudslide
31
Mass Wasting Landslides
Las Colinas Landslide, El Salvador, Feb. 2003
32
Mass Wasting
  • And this is the damage at ground level

33
For those who were here before, I guess you might
remember these chaps
Deposition
Transportation
Erosion
  • I would guess you also recall that 2 of these can
    be accomplished by several means?
  • traction , suspension, solution, saltation,
    hydraulic action, corrosion, attrition, abrasion

34
Now you know about the processes that enable the
river to change
  • What does the river look like?

35
The River Tees
High Force
This is where it is
36
(No Transcript)
37
The source of Tees
  • He is Matthew could not find a picture without
    him! See the beginnings of the V-shaped valley
    and interlocking spurs. Its source area is high
    in the Pennines in the west and the river flows
    eastwards into the North Sea.
  • The source of the River Tees lies on Cross Fell
    in the Pennines, 893m above sea level, where
    rainfall is over 2000mm a year.

38
Notice the big angular rocks the bedload and
also the rapids (or miniwaterfalls)
Potholes Potholes are formed by corrasion.
Pebbles carried by the river are swirled around
on the riverbed. This action erodes the rock on
the riverbed forming potholes. Over time, they
may widen and join with other potholes to form
larger potholes, and the whole riverbed is
deepened.  There are some deep ones on the River
Tees  below High Force (see later)      
           
39
RAPIDS on the River Tees
  • Rapids form where there are alternating bands of
    hard and soft rock, as seen here above High Force
    on the Tees

40
This is one worth learning to draw
41
Example High Force on the River Tees
  • It has a deep plunge pool at its base with a
    striking gorge of recession that has been
    created over thousands of years.
  • It is the one of the highest waterfalls in
    England, at 21m it is certainly most impressive
    to look at.

42
How High Force was formed
43
(No Transcript)
44
Fast flowing water has more energy
River cliff forms
Slip-off slope
This is one worth learning to draw
45
Slow, shallow water and deposition on the inside
of the bend
Deep, fast water and erosion on the outside of
the bend
46
(No Transcript)
47
  • As the outer banks of a meander continue to be
    eroded through processes such as hydraulic action
    the neck of the meander becomes narrow and
    narrower.

48
Oxbow lakes
  • Eventually due to the narrowing of the neck, the
    two outer bends meet and the river cuts through
    the neck of the meander. The water now takes its
    shortest route rather than flowing around the
    bend.
  • Deposition gradually seals off the old meander
    bend forming a new straighter river channel.
  • Due to deposition the old meander bend is left
    isolated from the main channel as an ox-bow lake.
  • Over time this feature may fill up with sediment
    and may gradually dry up (except for periods of
    heavy rain). When the water dries up, the feature
    left behind is known as a meander scar.

This is one worth learning to draw
49
Towards the mouth of the Tees, it meanders way
across the plain
Eventually the river will cut through what is
that called?
50
Levees (thanks to Mark Bailey)
51
What are they?
Often several metres higher than the rivers
floodplain, they are high natural embankments of
silt situated close to the river channel.
Where are they found?
They are most commonly found in the lower course
of a river where there is a floodplain, along
rivers that flood periodically, have a slow flow
and carry large amounts of load. The
Mississippi has the most notorious ones!
52
How are they formed?
The river before the flood at regular height. The
silt is carried as part of the load
The river whilst flooding - The silt is lifted
onto the bank
53
There is an increase in friction between the
water leaving the channel and the floodplain when
a river overflows. The water is shallower on the
river banks and valley floor This is why
deposition of load occurs just beyond the bank.
These banks increase in size with each flood.
The coarser material is deposited first, and is
positioned closer to the river.
After repeated flooding, the river bed and levees
are raised due to the constant process of the
deposition of silt. Over time, this eventually
causes the river to rise above level of flood
plain. This is called an aggraded bed.
54
The end of the river
  • Eventually the river flows into a lake or a sea
    or an ocean.
  • If the water it flows into has little current,
    any remaining silt is dropped as it enters and
    there is no current to remove it and a delta
    forms.

Mississippi Delta
55
But in the UK
  • There are plenty of currents to wash away any
    silt that is dropped and so our rivers have
    mouths instead.
  • I google-mapped this one. Where is it?

56
Practical skills
  • Measuring channel features measurement
  • Annotated sketches based on photographs.

57
Measuring river features
  • What can you measure?
  • Width
  • Depth
  • From this you can work out a rough cross-section
    area you do need to know how this can be done!
  • Rate of flow (oranges!!)
  • From these last 2 you can work out the discharge
  • Stone longitudinal length and angularity (Powers
    chart)

58
Measuring river features
59
Measuring water quality
  • What can you measure? Physical characteristics
  • Temperature algae and bacteria both do better
    in warm water, neither of which are good for
    water quality. There is less dissolved oxygen and
    more dissolved solids in warm water, neither of
    which are good for water quality
  • Turbidity high turbidity means cloudy highly
    turbid water is in general not good for water
    quality
  • Acidity water should be broadly neutral with a
    pH of around 7- neither stronger acid not
    stronger alkaline reading are good for water
    quality so acid water dues to sitting in a
    boggy area too long or due to cow/sheep poo is
    not good, nor are alkaline chemicals released
    from industrial processes good
  • Dissolved oxygen high dissolved oxygen is good
    for water quality. It means the plants are
    healthy and releasing oxygen. There is not too
    much decay going on. This is carried out by
    bacteria which are hungry users of oxygen. Also
    indicates low levels of dangerous bugs.

60
Measuring water quality
  • What else can be measured?
  • Nutrients nitrogen and phosphorous are not good
    for the plant and animal life. They find their
    way in from fertilizer running off the fields and
    urine and faeces from farm animals entering the
    water (see below)
  • Toxic substances many harmful things like
    metals, pesticides, and oil can be found in water
    and indicates that it should not be used for
    drinking water for example.
  • Bacteria certain types of bacteria, viruses and
    germs that can make you sick can be found in
    water. Often they come from faeces, both animal
    and human.
  • Biological sampling the health of waters can be
    found by taking samples of fish, plants and
    smaller invertebrates. Some of them love to live
    in water thats dirty, so if scientists find a
    lot of those in a sample, they know theres a
    problem. Other organisms can survive only in
    water thats very clean, so finding those means
    the water is probably healthy.

61
A picture from Nathan can you sketch and
annotate this?
What does annotation mean?
62
A picture from Nant Gwynllyn can you sketch and
annotate this?
63
Rivers- week 3
  • Key Question 3Water is vital to people, varies
    in availability and therefore needs careful
    management.
  • Essential content
  • The uses of water agriculture, industry, human
    hygiene and leisure including the reasons for a
    rising demand resulting in areas of water surplus
    and water shortage.
  • Reasons for differences in water quality. Sources
    of pollution (sewage, industrial waste,
    agriculture). Managing the supply of clean water
    (dams and reservoirs pipelines treatment
    works).
  • Flooding causes (intensity of rainfall,
    snowmelt, steep slopes, impermeable surfaces,
    human activities) and control construction of
    spillways, embankments).
  • Practical skills Measuring water quality
    aready covered
  • Case study of the rising demand for water in one
    country.
  • A case study of a dam or reservoir project.
  • A case study of a flood defence scheme.

64
First stage
  • The uses of water agriculture, industry, human
    hygiene and leisure including the reasons for a
    rising demand resulting in areas of water surplus
    and water shortage.
  • Case study of the rising demand for water in one
    country.

65
Uses of water
  • The uses are fairly obvious
  • agriculture,
  • industry,
  • human hygiene and
  • leisure
  • Which do you think is most common use of water?
    Surprising?
  • But do remember this is the average.
  • As a country develops, more water will be needed
    domestically ( washing machines, dishwashers) and
    also for recreation golf courses and swimming
    pools

66
(No Transcript)
67
Map showing water scarcity worldwide
Which colours indicate the a country does not
have enough water available?
What is the difference between yellow and red?
68
Here is the general picture
69
India is similar to other low/middle income
countries
  • Why do you think India still uses so much water
    in agriculture?
  • As India becomes more industrialized, industries
    needs will rise

70
Industrial use in India
What industries use most of the water at the
moment?
And as India industrializes more, more water will
be needed
71
Indian Industry
  • Thermal power
  • that is it burns things
  • engineering
  • textiles
  • paper
  • All use a lot of water and soon more will be
    needed
  • According to the World Bank, the water demand for
    industrial uses and energy production will grow
    at a rate of 4.2 per cent per year, rising from
    67 billion cubic meter in 1999 to 228 billion
    cubic meter by 2025.

What is the main thing that is burnt to make
electricitygt
Why is so much water needed?
72
Not only industry will need more
  • What are 2 issues shown here that say that India
    will need more water in future?

73
So we have a neat little case study here
  • Example of growing water usage in a country
  • Place India
  • How do they use their water at present?
  • Domestic ? Industrial? Agriculture?
  • Why will it rise?
  • Industrial use ?
  • (think which industries use most? Which will
    increase? By how much will it increase?)
  • Domestic use?
  • (Population what is happening to it figures.
    Potable water mention that have done well but
    still need?)

74
Ways to improve things
  • In rural areas, dig wells which you then line and
    cover to prevent them becoming contaminated.
  • On a large scale, build dams to collect water
    that can then be distributed to irrigate
    agricultural land and take fresh water to the
    cities
  • On a smaller scale, build infrastructure (long
    word for pipes and taps) in the poorer parts of
    cities.
  • Waste less!

75
Second stage
  • Reasons for differences in water quality. Sources
    of pollution (sewage, industrial waste,
    agriculture). Managing the supply of clean water
    (dams and reservoirs pipelines treatment
    works).
  • A case study of a dam or reservoir project.

76
Reasons for differences in water quality.
77
Managing the supply of clean water (dams and
reservoirs pipelines treatment works)
  • What does managing mean? Making sure that
  • There is clean water available for everyone by
  • Having the correct infra structure pipes and
    taps
  • There is a reliable source well, clean surface
    water, reservoir storage
  • Ensuring the sewage system is in place to keep
    the fresh water safe
  • Clean up the used water before it is released
    into a river/sea.
  • Water treatment before you use it or after you
    have finished with it is fairly similar check
    out the diagrams on http//ih-igcse-geography.wiki
    spaces.com/1.8CleanWater

78
A case study of a dam or reservoir project
Three Gorges Dam
79
Yangtze River and the Three Gorges
  • The Yangtze is Chinas largest river stretching
    5,600 kms from its source in Tibet to where it
    enters the Yellow Sea near Shanghai.
  • Midway through its course the river flows through
    a 190km section known as the Three Gorges.
  • The river valley narrows here and there are steep
    limestone cliffs on either side.
  • The river is fast flowing and hidden rocks make
    it dangerous for ships.

80
The Scheme
  • The dam, now nearly completed, is the biggest in
    the world, 2kms wide and 185 metres high.
  • It will create a reservoir 600kms long behind it.
  • It was started in 1993 and has just about been
    finished in 2009.
  • The cost will be at least 20 billion and the
    hydro-electric plant will generated 18,000
    megawatts of electricity, making it the biggest
    HEP station in the world, providing 10 of
    Chinas electricity

81
Advantages of the Scheme
  • During the 20th Century there were 3 catastrophic
    floods, plus many smaller ones. Over 300,000
    people have been drowned. The dam will prevent
    flooding, thereby saving thousands of lives.
  • The dam will provide 10 of Chinas present
    electricity requirements. It will be a clean
    fuel, reducing Chinas SO2 emissions and helping
    to reduce global warming gases.
  • All year round navigation will be possible by
    ocean going vessels as far as Chongqing at the
    far end of the reservoir.
  • Over 20,000 medium term jobs have been provided
    in the construction industry. This will create a
    positive multiplier effect to the local economy

Multiplier effect?
82
Disadvantages of the Scheme
  • 1.2 million people will be relocated. This will
    include 13 cities, 140 towns, and 4500 villages.
    In addition 1600 industrial enterprises will have
    to be relocated.
  • 23,000 hectares of fertile farmland and 7000
    hectares of forest will be drowned.
  • Prior to the dam, spring floods were a regular
    feature. They brought fertile silt downstream to
    the farms on the banks of the river, which
    reduced the need for artificial fertilizer.
  • This fertile soil will be lost to farms
    downstream from the dam. This is likely to lead
    to an increase in the use of chemical fertilisers.

83
Disadvantages of the Scheme
  • Sediment will build up behind the dam over time
    leading to a squeezing out of the reservoir.
  • Pollution in the form of sewage and toxic metals
    from industry will collect and build up the
    reservoir.
  • The reservoir will create much deeper, colder
    water thereby changing the environment including
    types and numbers of fish.
  • The dam lies near an earthquake fault line.
  • Although the government says they have taken this
    into account, any major earthquake could create a
    disaster on an unprecedented world scale, with a
    death toll of several million.

84
What do you notice about the visibility?
85
Issues over large dam projects have led to changes
  • Up until the mid 1990s, the World bank funded
    many large dam projects.
  • According to the Manibeli Declaration these large
    dams have had "extensive negative environmental
    impacts, destroying forests, wetlands, fisheries,
    habitat for threatened and endangered species,
    and increasing the spread of waterborne
    diseases." In addition the World Bank has
    "tolerated and thus contributed to gross
    violations of human rights by governments in the
    process of implementing Bank-funded large dams,
    including arbitrary arrests, beatings, rapes, and
    shootings of peaceful demonstrators.
  • As a result of this and other criticisms, they
    stopped.

In simple terms, why were large dams seen as a
bad idea?
86
Third stage
  • Flooding causes (intensity of rainfall,
    snowmelt, steep slopes, impermeable surfaces,
    human activities) and control (construction of
    spillways, embankments).
  • A case study of a flood defence scheme

87
Causes of Flooding
  • Intensity of rainfall,
  • Snowmelt,
  • Steep slopes,
  • Impermeable surfaces,
  • Human activities like what?
  • We have already covered these when looking at
    storm hydrographs.
  • Can you remember why these particular features
    cause floods?

88
Controlling floods
  • They talk of spillaway and embankments in the
    syllabus, but there are many others.
  • There are 2 groups of techniques, hard and soft
    engineering.
  • Hard' options tend to be more expensive and have
    a greater impact on the river and the surrounding
    landscape.
  • 'Soft' options are more ecologically sensitive.

89
Hard engineering
  • Dams and reservoirs can be use to control the
    amount of water downstream and therefore prevent
    floods of towns or other essential installations,
    e.g. Cow Green reservoir on the R Tees
  • Building embankments (or artificial levees), e.g.
    Mississippi at New Orleans
  • Flood Walls stronger versions of levees
  • Revetments - floodwalls built at a low angle to
    reduce erosion by the flood water
  • Gabions cheaper versions to reduce erosion
    metal baskets filled with large stones
  • Channelizing (straightening) and dredging rivers
    to increase the speed which the water passes
    through and so reducing flood risk
  • Diversion channels and diversion basins
    (spillaways) which take the water away from towns
    etc
  • Culverts passing a river through a pipe.

90
Soft engineering
  • Afforestation
  • Managed flooding (or ecological flooding)
  • Planning (or land use zoning)
  • Monitoring and warning systems

91
River Tees Management the issues
  • The River Tees has a long history of flooding.
  • The first documented flood was at Croft on the
    lower Tees in 1356.
  • Many of the previous floods were precipitated by
    snow melt. However, the Environment Agency
    suggest that this will be less of a problem in
    the futures.
  • But, intense rainfall is more likely to be a
    problem so flash floods will become more
    frequent, especially as more of it has become
    concreted over
  • The Tees valley is also home to a large
    population and many industries, all requiring a
    reliable water supply.
  • The river is managed to provide a water supply
    and to control flooding.
  • In recent years there have also been developments
    to increase its potential for recreation and
    tourism.

92
River Tees - Management
  • Cow Green reservoir was built in 1970 to provide
    water for the growing industries on Teesside.
  • It is a regulating reservoir, storing water in
    times of plenty and releasing enough for the
    needs of industry in times of low flow.
  • In times of severe summer droughts water can be
    added to the River Tees via a tunnel which
    connects it to the River Tyne and Kielder
    reservoir.
  • Dredging
  • The lower stretches of the Tees estuary are
    dredged (sediment is extracted) periodically to
    improve navigation by maintaining a deep-water
    channel.
  • There has also been some dredging in the upper
    parts of the estuary to reduce the flood risk -
    it increased the capacity of the channel.

93
Lower Tees Valley- Management
  • The Tees Barrage (a man made barrier across a
    river)
  • The aim of the Tees Barrage was to improve the
    water quality and recreational value of 22km of
    the lower Tees.
  • The barrage was completed in 1995 and cost 54
    million.
  • The 22km stretch of river between Yarm and
    Stockton is now kept permanently at high tide.
  • The water is fresher and cleaner as it does not
    mix with the tidal salt water in the lower
    estuary.
  • The barrage also reduces the risk of flooding at
    very high tides or during a storm surge.
  • The barrage has acted as a catalyst for 500
    million of investment in offices, housing,
    educational, leisure and shopping facilities.

94
Lower Tees Valley- Management
  • Cutting of meanders - channelizing
  • In 1810, the Tees Navigation Company cut across
    the neck of the Mandale Loop, a large meander
    near Stockton.
  • The new route shortened the river by 4km. Other
    stretches of the river have been artificially
    straightened.
  • This allows the water to move faster along the
    channel (less energy lost with the river banks),
    reducing the flood risk.

95
Yarm from the air
96
Lower Tees Valley- Yarm
  • Yarm's flood defence scheme Yarm, a historic
    market town and once an inland port, is located
    on the inside bend of a large meander.
  • Yarm is particularly prone to flooding.
  • The most recent serious flood was in January
    1995.
  • Since then a new flood defence scheme costing
    2.1 million has been built which
  • reinforced concrete walls with flood gates for
    access by people and vehicles.
  • earth embankments artificial levees to contain
    the river.
  • gabions (baskets filled with stones) to protect
    the walls and embankments from erosion.

97
Lower Tees Valley- Yarm
  • The scheme also incorporates features designed to
    reduce the visual impact of the walls and to
    enhance the environment.
  • There are fishing platforms, new street lighting
    and a comprehensive planting scheme.
  • English Heritage approved all building materials
    used so that they were in keeping with the
    existing architecture of the town.

98
Lower Tees Valley- Yarm
  • Improved flood warning systems.
  • These have better liaison with the Meteorological
    Office, police and other emergency services.
  • Finally, new development discouraged building on
    low-lying and flood-prone land - an example of
    land-use zonation - land is used for activities
    not damaged by inundation (long word meaning
    severe flooding) e.g. playing fields, parks,
    urban forests/walks etc
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