Water on the land
What you should know and links to revision material…
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CUE 1: You need to be able to identify and explain the processes of erosion –
hydraulic action, abrasion, attrition and solution.
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CUE 2: You must understand the processes of lateral and vertical erosion.
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CUE 3: You must identify and explain the processes of transportation –
traction, saltation, suspension and solution.
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CUE 4: You need to understand deposition and the reasons it takes place.
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CUE 5: You need to recognise the long profile of a river and the changes that
occur in the upper, middle and lower course of the river.
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CUE 6: You need to recognise and be able to sketch landforms resulting from
erosion – waterfalls and gorges.
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CUE 7: You need to recognise and be able to sketch landforms resulting from
erosion and deposition – meanders and oxbow lakes.
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CUE 8: You need to recognise and be able to sketch landforms resulting from
deposition – levees and floodplains.
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CUE 9: You need to describe and explain factors affecting river discharge (flow) amount and type of rainfall e.g. Monsoon / storm event, temperature, previous
weather conditions, relief (shape of the land and river profile), rock type
(permeable / impermeable) and land use.
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CUE 10: You need to describe, explain and categorise the causes of flooding.
Physical – prolonged rain, heavy rain, snowmelt and relief.
Human – deforestation, building construction.
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CUE 11: You must be able to describe the location of flood events in the UK in
the last 20 years and comment on the increased frequency of these events.
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CUE 12: You need to be able to name and describe a case study of flooding in
both a LDC and MDC and explain the responses to this event.
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CUE 13: You need to be able to describe flood management strategies.
Hard engineering – Dams, reservoirs and channel straightening.
Soft engineering – Flood warning, preparation, floodplain zoning, allowing
flooding and the costs and benefits of these solutions.
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CUE 14: You need to be able explain the UKs increasing demand for water and
the areas of the country with a deficit (lack of) and surplus. You should know
about schemes and the need to transfer water to and from these regions.
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CUE 15: You need to be able to describe a case study of a dam or reservoir and
successfully discuss the social, economic and environmental issues. These issues
should be linked to future sustainability of our water supply.
CUE 1: You need to be able to identify and explain the processes of erosion – hydraulic
action, abrasion, attrition and solution.
Hydraulic Action
This process involves the force of water against the bed and banks.
Abrasion
This is the process by which the bed and banks are worn down by the river’s
load. The river throws these particles against the bed and banks, sometimes at
high velocity.
Attrition
Material (the load) carried by the river bump into each other and so are smoothed
and broken down into smaller particles.
Solution
This is the chemical action of river water. The acids in the water slowly dissolve
the bed and the banks.
Practise Questions
1. Explain how a river erodes (3Mks) June 2011
2. Describe one process of river erosion (2Mks) June 2010
CUE 2: You must understand the processes of lateral and vertical erosion.
A rivers discharge is low in the upper course, giving the river only enough energy
to erode downward. This is called vertical erosion.
As the course of a river approaches its middle stages it flows over flatter land.
Lateral erosion dominates as the river swings in large bends known as
meanders. Meanders constantly change their shape and position.
Water is pushed to the outer bend. This reduces friction with the bed and
banks. So the river has more energy for transporting material which can erode
the outside bank via abrasion.
Vertical erosion
Lateral erosion
Practise Questions
1. Draw a cross section to show how the inside bend of a meander is different from the
outside of bend of a meander (4Mks) June 2011
(Tough one, see how you do. If you struggle attempt this after cue 7)
2. Produce a diagram to show the difference between vertical & lateral erosion (2
marks)
CUE 3: You must identify and explain the processes of transportation –
saltation, suspension and solution.
traction,
Traction
Boulders and pebbles are rolled along the river bed at times of high discharge.
Saltation
Sand sized particles are bounced along the river bed by the flow of water.
Suspension Fine clay and sand particles are carried along within the water even at low
discharges.
Solution
Some minerals dissolve in water such as calcium carbonate. This requires
very little energy.
Practise Questions
1. Describe how a river transports its load (3Mks) June 2012
2. Produce a labelled diagram to show how a river transports material (4 marks)
CUE 4: You need to understand deposition and the reasons it takes place.
Rivers need to be flowing to pick up and transport material (load). The faster the flow the
more energy they have and so can move more load. The opposite is also true. When a river
slows its loses energy and with it the potential to transport material. Heavier material will
be deposited first.
Practise Questions
1. When does a river deposit material? (2 marks)
CUE 5: You need to recognise the long profile of a river and the changes that occur in the
upper, middle and lower course of the river.
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The relief changes from steep to gently sloping.
The river valley changes from V shaped valley to floodplain.
The speed of the river goes from fast to slow.
The processes change from mostly erosion processes in the upper course to
deposition processes in the lower course.
The channel changes from shallow to deep.
The size of meanders increases as you move downstream through the profile.
Practise Questions
1. Describe how a river changes between its source and its mouth (3 marks)
2. Describe the long profile of a river and how it changes (3 marks)
CUE 6: You need to recognise and be able to sketch landforms resulting from erosion –
waterfalls and gorges. You need to be able to explain how a waterfall and recessional
gorge form.
In an area where hard rock is found above softer rock, the softer (less resistant rock) will
erode more quickly. Over time this will mean that the harder (more resistant rock) above
becomes undercut. This process of undercutting creates an overhang of resistant rock. The
process continues until the hard rock overhang is unsupported and eventually collapses.
The debris from the overhang will swirl around at the base of the waterfall, through the
processes of abrasion and hydraulic action an over deepened pool known as a plunge pool
is created. The debris will be broken up and then transported downstream. The process of
erosion continues and the cycle repeats. The cycle means that the waterfall moves
backwards (upstream), as the waterfall retreats upstream it leaves in front of it a steep
sided recessional gorge.
Practise Questions
1. Produce a labelled diagram to show the features of a waterfall. (4 marks)
2. Produce an annotated diagram to explain the formation of a waterfall and
recessional gorge (6 marks)
3. Explain the formation of a waterfall and recessional gorge (8 marks)
CUE 7: You need to recognise and be able to sketch landforms resulting from erosion and
deposition – meanders and oxbow lakes. You need to be able to explain how the features
of a river bend form and how an Ox-Bow lake forms.
Meanders:
A meander is a bend in a river.
On the outside of a river bend the channel is deep as the water is fast flowing and erosive.
The banks erode due to hydraulic action and abrasion. A feature known as a river cliff forms
on the outside of a river bend.
On the inside of a river bend the channel is shallow as the water has a slow flow and
therefore deposits material. A feature known as a river beach or a slip-off-slope is created.
Oxbow Lakes Lateral EROSION at two adjacent meanders will cause the channel to move
across the land over time. The space in between the two meanders reduced as the neck of
land is eroded.
Eventually the river breaks through the space between the meanders, perhaps during a
flood event. DEPOSITION will eventually create a build up of material that close the neck
once more, leaving behind an oxbow lake.
Practise Questions
1. Draw a cross section to show how the inside bend of a meander is different from the
outside of bend of a meander.(4Mks) June 2011
2. Produce an annotated diagram to explain the formation of the features found on a
river bend (6 marks)
3. Explain how the features found on a river bend are formed. (6 marks)
4. Produce a series of annotated diagrams to explain the formation of Ox-Bow lakes (6
marks)
CUE 8: You need to recognise and be able to sketch landforms resulting from deposition –
levees and floodplains.
Floodplains and leveés are formed by deposition in times of river flood. The river’s
load is composed of different sized particles. When a river floods it deposits the
heaviest of these particles first. The larger particles, often pebble-sized, form the
leveés. The sands, silts and clays are similarly sorted with the sands being
deposited next, then the silts and finally the lightest clays. Every time the river floods
deposition builds up the floodplain.
Practise Questions
1. Explain the formation of a floodplain (4Mks) June 2012
(Note there are NO command words to draw a diagram but you could include one)
CUE 9: You need to describe and explain factors affecting river discharge (flow) - amount
and type of rainfall e.g. Monsoon / storm event, temperature, previous weather
conditions, relief (shape of the land and river profile), rock type (permeable /
impermeable) and land use.
River discharge is the volume of water passing a certain point in the river. The discharge is
affected by a number of factors, some human and some natural…
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Monsoon weather is prolonged seasonal rainfall. Land becomes saturated
and river levels steadily rise. Lowland areas such as the flood plain are prone
to flooding during the monsoon season.
Storm events can create flash floods. This is where the shear volume of
water entering the channel is too high for the river to effectively drain away.
Temperature can impact on the discharge of a river. In sub-zero conditions
water is effectively locked in the soil and its journey to the river is slowed or
stopped. Conversely, if frozen land or lying snow thaws quickly it can create a
huge input to the river system. This again can trigger the water level to rise or
for flooding to occur.
Previous weather can impact the effects of heavy rainfall on the channel.
Drought can bake the land so dry that surface run-off is increased, increasing
the volume of water entering the river channel. Prolonged rain in previous
days can soak the surrounding land to saturation point. This also increases
surface run-off and flood risk.
The shape of the surrounding land (Relief) impacts on flood risk. Refer
back to the long profile diagram. V shaped valleys contain water whilst
floodplains allow water to travel great distances once it has overtopped its
channel. Relief affects the rates of surface run-off and the rivers speed and
ability to drain water away effectively.
Permeable / impermeable rock type is a factor in flooding because it
impacts on the surrounding landscapes ability to sold and store water.
Permeable rock allows percolation to occur and can slow waters progress to
the river as some water travels vertically. Impermeable rock does not allow
vertical movement and increases through flow in the soil above. The soil will
reach saturation point quicker and surface run-off will occur.
Practise Questions
1. Explain the factors affecting river discharge (6Mks) June 2011
2. Explain how snowmelt can cause a river to flood (3Mks) June 2011 (F)
CUE 10: You need to describe, explain and categorise the causes of flooding.
Physical – prolonged rain, heavy rain, snowmelt and relief.
Human – deforestation, building construction.
For this LDC example below: Bangladesh
1) Write a title
2) Draw a table
3) List human factors
4) List physical factors (Take the details from the diagram below)
Bangladesh Effects
-Floods covered half of Bangladesh as the
country is low flat land.
-Millions were made homeless. (8.5 in 2004)
- 760 killed (in 2004)
- Food supply disrupted. Rice contaminated
with silt and fishing boats damaged.
- Infrastructure damaged making travel
difficult.
Bangladesh Responses
- Emergency International Aid to support the
country (Food, clean water, shelter,
medicines). Refer to a charity such as the
Red Cross and an MEDC government
pledging support such as the UK.
- Longer Term Responses involved the
development of a dam network supported
by the World Bank, however this scheme
remains only partially completed. (This
would not be the case in an MEDC)
- Longer term soft management strategies
are afforestation and the education of local
people on the importance of sustainably
managing woodland.
Flooding in more developed countries can happen for a variety of reasons, such as…
1) Overgrazed uplands
2) Building on flood plain
3) Urban areas (concrete)
4) Roads and drains
5) Relief
6)
Mississippi Case Study…
The Mississippi Drainage basin is a huge river network running north to south in the USA.
The natural flow of the river would see it meandering and flooding huge areas of land. To
make the river more useful and a transport and trade link people have interfered with an
managed the river course. The river has been straightened, shorted and walled in. However
this has created other problems.
Causes
A period of prolonged heavy rainfall saturated the river basin, additional
surface runoff to the channel meant that the river reached bank full and
then levee full. The water level was the same height as the walls created
by humans to hold the river in.
Effects
Primary
-43 people were killed in the flood.
-Fields flooded & crops lost.
-Houses destroyed.
-Forests and habitats destroyed
Secondary
-Stagnant water led to mosquito populations increasing.
-Transport & Communication disrupted.
-Economic damage totalling £12 billion, meant the economy and business
could not operate as normal.
-Certain crops being destroyed influence local and global prices in trade.
Responses
Short-term
-50,000 were evacuated.
-Sandbags distributed
-Warning’s issued via the media and the levee districts (people
responsible for flood management).
Medium-term
-Clean-Up
-Aid & Shelter
Long-term
-Re-building.
-Afforestation.
-Strengthen Levees.
-Louisiana Spillway opened.
Practise Questions
1. Using the figure above, give one physical cause and one human cause of flooding
(2Mks) June 2011 (F) (Note this is a short question with NO command to explain)
2. Describe the effects of a flood you have studied. (6 marks)
3. Describe the responses to a flood you have studied (6 marks)
4. Explain how the effects of flooding differ between countries of differing levels of
development. (8 marks)
CUE 11: You must be able to describe the location of flood events in the UK in the last 20
years and comment on the increased frequency of these events.
MEDC case study: causes and effects of flooding in Boscastle, UK (2004)
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Causes
Over 60 mm of rainfall (typically a month's rainfall) fell in two hours.
The ground was already saturated due to the previous two weeks of above average
rainfall.
The drainage basin has many steep slopes, and has areas of impermeableslate
causing rapid surface run-off.
Boscastle is at the confluence (where tributaries meet) of three rivers - Valency,
Jordan, and Paradise. A large quantity of water all arrived within a short space of
time causing the rivers to overflow.
The flooding coincided with a high tide, making the impact worse.
Effects
Homes, businesses and cars belonging to more than 1,000 people were swept
away.
Income from tourism was lost. This had an impact on livelihoods and the local
economy.
There were vast numbers of subsequent insurance claims.
No lives were lost, partly due to the rapid response of the emergency services.
Practise Questions Describe the effects of flooding in an MDC you have studied (4Mks)
 CUE 13: You need to be able to describe flood management strategies.
June 2010
Hard engineering – Dams, reservoirs and channel straightening.
Soft engineering – Flood warning, preparation, floodplain zoning, allowing flooding
and the costs and benefits of these solutions.
Soft Engineering does not involve construction and can be cheaper. This can make soft
engineering economically achievable for LDCs and their impact on the environment is
often reduced. Methods range from managed flooding, allowing rivers to flood certain
areas, avoiding inappropriate development in flood risk areas or simply planning and
predicting combined with a warning system. Soft engineering approaches make use of
natural processes such as deforestation increases interception and water storage.
Practise Questions
1. Hard and soft engineering strategies are used to manage flooding. Choose either hard
engineering or soft engineering and explain why it is the better strategy (8Mks) June
2011
(Tip – try SEE categories and refer to LDC/MDC) (This is tough but if you want to wait until
Cue 15 you could use the information provided you will still need to show your
understanding of soft engineering techniques)
CUE 14: You need to be able explain the UKs increasing demand for water and the areas of
the country with a deficit (lack of) and surplus. You should know about schemes and the
need to transfer water to and from these regions.
The choropleth map on the left shows rain fall. The map on the right show the
population. The main population centres are in southern England. The rainfall map
shows there is clearly a surplus (Excess) of rainfall in western Scotland. This area
however is sparsely populated and demand is low. Where demand is high there is a
deficit as there a lack of rainfall.
(You would quote figures, use compass direction, and regions).
CUE 15: You need to be able to describe a case study of a dam or reservoir and
successfully discuss the social, economic and environmental issues. These issues should be
linked to future sustainability of our water supply.
Kielder Water, Northumberland. North East England.
A dam was constructed and the the Keilder valley was
flooded.
Water is a large artificial reservoir in
Northumberland in North East England. It is the largest
artificial lake in the United Kingdom by capacity and it is
surrounded by Kielder Forest, the largest man-made woodland in Europe.
Built 1975-1981 – First flooded 1982
Social
Improved water supply for
the area for both domestic
& industrial use.
Environmental
The old land was only poor
quality farmland.
Economic
Jobs would be created as
part of the building process;
From tourism & recreation.
Social
Some people had to move,
but only a few people had
to be moved as the area
had a low population.
Environmental
Some habitats and wildlife
lost, though this was limited
as land was mainly rough
grazing.
Economic
Expensive, but a sustainable
solution and is reliable.
Practise Questions
1. Discuss the issues which result from building dams and reservoirs. (8 marks)
2. Explain how the UK manages to create a reliable water supply (6 marks)
3. Explain why the South of England have more hose pipe bans than the North. (6
marks)