Rivers Revision
-We will revise the main topic areas
of Water on the Land
Knowledge Checklist
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Know the processes of erosion
Know the processes of transportation
Know how waterfalls and gorges are formed
Know how meanders and ox-bow lakes are formed
Know how flood plains and levees are formed
Know the factors that affect river discharge
Know the physical and human causes of flooding
Know a case study of a rich and poor country flood
Know how hard and soft engineering can be used in flood
management
• Know how water is used in the UK with areas of surplus and
deficit
• Know a case study of a reservoir in the UK
The Profile of a River
Key Idea: The shape of river valleys changes as rivers flow downstream
due to the dominance of different processes.
Processes of erosion – hydraulic action, abrasion, attrition, solution;
vertical and lateral erosion.
Processes of transportation – traction, saltation, suspension and
solution.
Deposition and reasons for it.
Long profile and changing cross profile.
The Water Cycle
It is the main input to the drainage basin
The long profile and the drainage
basin
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The long profile of a river is a
cross section from its source to
its mouth. This whole area is
known as the drainage basin.
They are divided into three
sections:
– Upper course
– Middle course
– Lower course
River gradient decreases
gradually as the river flows
downstream (ie. It becomes less
steep)
Drainage Basin Key words
• A river basin is the area of land drained by a
river and its tributaries
• Watershed – an area of higher land
separating two drainage basins
• Source – the place where a river begins
• Tributary – a smaller river joining a larger one
• Confluence – the place where two rivers join
• Mouth – the place where a river enters a lake
or the sea
Processes of Erosion
Transportation
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Material is carried in the river in four ways:
Traction: large stones are rolled along the river bed
Saltation: smaller stones ‘bounce’ along the river bed
Suspension: small particles of silt and clay float through the
water
Solution: minerals are dissolved in the river
Deposition
Deposition is the dumping of material and happens when the river loses its
energy. This may be during a dry spell, on the inside of a river bend, or
when the river reaches the sea (read
on for more on this).
The Long Profile of a River
L.Ob: to describe how a river changes from source to mouth
Think about
the 2 pictures of rivers:
why are they so different?
Features at the 3 stages of a river
Why?
UPPER COURSE
SOURCE
MIDDLE COURSE
Lateral &
vertical erosion,
transportation,
deposition
LOWER COURSE
Transportation &
deposition
Vertical erosion
& transportation
MOUTH
V-shaped valley
Waterfalls
Rapids
Interlocking spurs
Meanders
Ox-bow lakes
Levees
Flood plain
SEA
River Severn – Source to Mouth Video
Upper Course
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Vertical erosion is the main process.
Valleys are v-shaped, interlocking spurs.
Waterfalls are formed.
Rapids are smaller scale feature formed
where finer bands of varying resistance of
rocks are found.
Foundation Question
Higher Question
Upper Course – V-Shaped
Valleys and Interlocking Spurs
Upper Section Landforms
Waterfalls
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A waterfall is a place on a river where the water flows vertically
They tend to occur in the upper course of a river
Softer rock erodes quickly, undercutting harder rock
Harder rock erodes more slowly, forming overhang
Overhang eventually collapses – the waterfall moves upstream
Steep sided valley (gorge) is formed
Plunge pool erodes under waterfall
Landforms in Middle and Lower
Sections: Meanders
Formation of Meanders
Slow flow = loss of energy. Fast flow = lots of energy.
Low energy = deposition. High energy=erosion
Foundation and Higher Question
Meanders and Ox-Bow Lakes
Meandering stream
flowing from
top of screen
to bottom
Maximum
deposition
Maximum
erosion
Meander scars
Oxbow Lake
Oxbow
cuttoff
Foundation Question
Higher Question
A Delta
Some rivers reach the sea in deltas, which form
where river mouths become choked with
sediment, causing the main river channel to split
into hundreds of smaller channels or
distributaries
Deltas only form under certain conditions
• The river must be transporting a large amount
of sediment
• The sea must have a small tidal range and
weak currents
• The sea must be shallow at the river mouth
Famous deltas consist of the Mississippi delta,
The Ganges and Brahmaputra delta
(Bangladesh) and of course the Nile delta.
Flood Plains and Levees
When a river continually
floods, it spreads silt
across the flood plain.
Often this material piles
up to form levees.
Sometimes, humans
make artificial levees to
mimimise the impact of
flooding.
Peak Rainfall
Peak Discharge
Flood
Hydrograph
RAINFALL mm
DISCHARGE (cumecs)
LAG TIME
time
River DISCHARGE
• Discharge is the volume rate of water flow,
which is transported through the river
channel.
• Measured in cumecs (cubic metres per
second)
The Flood Hydrograph –
A = floods quickly (flash flood)
B = slower rate of discharge, less likely to flood
WHAT FACTORS AFFECT THE DISCHARGE LINE?
Factors Affecting Water in a River
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Amount and type of rainfall
Previous weather conditions
Land use
Temperature
Rock type
Relief
Describe 5 factors that might affect the lag time (time
it takes river to flood)
Describe 5 factors that might affect the lag time (time
it takes river to flood)
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1 = Deforestation
2 = Urbanisation
3 = Relief of land
4 = Dam Building
5 = Industry/Agriculture
Contrast the
hydrographs (3)
Explain why the two
hydrographs are
different (4)
Foundation
Higher
Flooding
Physical Factors
Human Factors
Prolonged Rainfall
Deforestation
Snowmelt
Impermeable materials
Heavy Rainfall
Relief
Frequency of Flooding
Flooding in the UK appears to be happening more often!
Case Studies
• You need to know too flood case studies!
– Rich Country (Worcestershire, England)
– Poor Country (Bangladesh)
MEDC: UK Floods 2007
Write a quick case study….
What caused the floods? What were the
main effects? What are the solutions?
FLOODING IN AN LEDC – Bangladesh Case Study
IMPORTANT DATES and DEVELOPMENT INDICATORS for Bangladesh
CAUSES of the flood:
MANAGEMENT RESPONSES – can they reduce the
impact?:
EFFECTS of the flood on People and Environment:
Remember SHORT and LONG TERM
Hard Vs Soft Engineering
Page 92 of book
Raise levees
Dredge river beds
Straighten rivers
Hard Vs Soft Engineering
Zone off some
areas
Better warning
systems
Model answers and mark scheme
For more past papers and info visit the OCR ‘A’ Geography website
http://www.ocr.org.uk/qualifications/gcse/geography_a/documents.html
Managing Water in the UK
• What causes the
water stress?
• How can we be more
efficient with water?
(6)
Reservoir Case Study
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You need to know one case study of a reservoir that provides water to people in
the UK
Kielder Reservoir is in book
- Biggests man-made reservoir in Europe.
- Was poor farmland, large valley with steep sides.
- Lots of rainfall and low population.
- Wild habitats were limited so little environmental damage.
- Supplies NE of England wit water.
- Lots of leisure industry there. Good for economy.
Past Paper Questions
Click for examiners
mark scheme
Model answers and mark scheme
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Model answers and mark scheme
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