RIVERS
Revision
Booklet
AS LEVEL GEOGRAPHY
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2
Checklist:
I can…
No
Sort of
Yes
Draw and label a drainage basin
Explain what each of the flows and processes are (e.g.,
infiltration)
Describe and explain a water balance graph
Label a storm hydrograph
Explain physical and human characteristics that influence the
shape of a hydrograph
Describe the four types of fluvial erosion
Describe the four types of fluvial deposition
Explain the difference between capacity and competence
Explain what a Hjulstrom Curve shows
Name the features found along the long profile of a river. I also
can name a river case study which shows these features
Explain how a channel’s characteristics varies downstream
(e.g., hydraulic radius, wetted perimeter)
Draw and label the change in cross-profile of a channel and
valley along its long profile.
Explain the formation of waterfalls, potholes and rapids
Explain the formation of meanders, flood plains, levees and
ox-bow lakes
Explain the formation of deltas, braiding and distributaries
Explain the causes of river rejuvenation and its associated
landforms
Explain the physical and human causes of flooding and relate
this to a case study
Explain the social, environmental and economic impacts of
flooding and relate this to a case study
Can compare the causes and impacts of flooding between
LEDC and MEDC case studies
Explain how flood frequency can be calculated
Describe and give examples (case studies) of hard engineering
strategies
Describe and give examples (case studies) of soft engineering
strategies
Compare the relative merits of hard and soft engineering
strategies
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Quick facts:
A river drainage basin is ___________________________________________________________________
_______________________________________________________________________________________
The watershed is ________________________________________________________________________
_______________________________________________________________________________________
In the box above draw a typical drainage basin. Label on the following inputs, outputs, flows and storages:
precipitation, transpiration, surface run-off, interception, stemflow, infiltration, throughflow, water
table, percolation, groundwater storage, groundwater flow, channel storage, evaporation, condensation
Key Term
Meaning
Transpiration
Interception
Infiltration
Percolation
Throughflow
Surface run-off
Percolation
Evaporation
Condensation
Precipitation
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Label the following features on to your water
balance graph:
Precipitation (solid line)
Evaporation (dotted line)
Water surplus (too much water)
Water deficit (too little water)
Groundwater store recharge
Field capacity attained
The graph above is a typical water balance graph for the UK. Using the key words from the box above
describe how the water balance of the UK changes with the seasons.
1) In the winter months…
2) In the summer months…
3) At the end of the summer months…
Exam questions
1) Describe how water reaches a river channel in a drainage basin (4
marks)
2) Describe how the water balance of the UK changes with the seasons
(4 marks)
3) Explain how vegetation can reduce the amount of water reaching a
river channel (4 marks)
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B
A
The two hydrographs above show how the river discharge changes over time.
Describe the following features:
Peak discharge _____________________________________________________________________
Peak rainfall _______________________________________________________________________
Lag time __________________________________________________________________________
Rising limb ________________________________________________________________________
Falling limb ________________________________________________________________________
Describe the main differences between the two hydrographs:
1)
2)
3)
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River discharge (the volume of water in a river) is affected by: the amount of precipitation, the amount
of evaporation and the amount of abstraction (water removed from river, e.g., for industry).
It is also affected by a number of other physical and human characteristics. You will need to know the
meanings to each of the following factors and how they affect the lag time.
Use the key terms from page 3 to explain your answers.
Drainage basin characteristics (size; steep slopes, drainage density (number of streams in the basin)):
Amount of water already in drainage basin (antecedent moisture):
Rock type (permeable/impermeable):
Soil type:
Deforestation/Afforestation:
Urbanisation:
19:30
answer. (4 marks)
0
18:00
affect its storm hydrograph? Explain your
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16:30
5) How might deforestation of this drainage basin
10
15:00
river shown to the right (2 marks)
15
13:30
4) Give the lag time and peak discharge for the
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Boscastle hydrograph
120
100
80
60
40
20
0
12:00
Exam questions
7
Label the diagram above with the four types of fluvial erosion
Erosion type
C
Explanation
or A
H
A
C
or S
A
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The velocity of a river
provides the energy
needed for it to transport
the eroded material.
The eroded material is
called its load.
Which of the transport
types would require the
highest velocity?
Transport type
Explanation
Traction
Saltation
Suspension
Solution
Quick facts:
Competence ___________________________________________________________________________
_______________________________________________________________________________________
Capacity _______________________________________________________________________________
_______________________________________________________________________________________
Particle size _____________________________________________________________________________
_______________________________________________________________________________________
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Quick explanation of the
Hjulstrom Curve:
Particle size is along the
horizontal scale, from clay
to boulders.
The velocity of the river is
along the vertical scale. It is
a logarithmic scale.
The Hjulstrom curve shows
how erosion, transportation
and deposition vary with
different river velocities
Draw a line across at 100 cm/s.
At this velocity the river will transport small clay particles (less than 0.01mm) and small pebbles (1050mm) that have already been eroded. It will erode (and transport) silt (0.01-0.1mm), sand (0.1-1mm)
and gravel (1-10mm). It will deposit large pebbles (50-100mm), cobbles and boulders (above 100mm)
Your turn… what are the velocities required to deposit, transport and erode a sand particle (size
0.1mm).
Deposition:
Transport:
Eroson:
The critical erosion velocity curve shows the minimum velocity needed to erode material.
It takes a higher velocity to erode material than to transport it.
The mean settling velocity curve shows the velocity at which particles are deposited. This is the
equivalent to the competence of the river.
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Describe:
The pattern of the mean settling velocity curve (this is the boundary between the velocities at
which particles are deposited and transported).
The pattern of the critical erosion velocity curve (this is the boundary between the velocities at
which particles are transported and eroded). Explain why it takes higher velocities to erode silts
and clays.
Disadvantages of the Hjulstrom curve:
1) Velocity – where?...
2) Shape of load…
3) Density of load…
Exam questions
6) Outline the four ways a river can transport its load (4 marks)
7) Outline the four main ways a river can erode material (4 marks)
8) Describe briefly why a river a river drops its load (2 marks)
9) What is meant by the competence of a river?
10)
Outline how the critical erosion curve on a Hjulstrom graph varies
with particle size (6 marks)
11)
Comment on the usefulness of the Hjulstrom curve as a way of
determining the main processes in a river channel (6 marks)
11
Label on the diagram where the following features would be found:
Waterfall
Meander
Rapids
Potholes
Delta
Ox-bow lake
V-shaped valley
Estuary
Gorge
Distributary
Flood plain
Levee
Key facts:
The long profile shows the gradient of the river channel from source to mouth. The base level is
the lowest point of the river (usually at the sea).
Total erosion = Total deposition along the river profile. The rate of erosion/deposition can
change.
The river will try to smooth out any unevenness in its profile. This is called the graded profile.



Upper course: High potential energy as it is so high above sea level.
Middle course: High kinetic energy as the river gains velocity
Lower course: Little potential energy, but lots of kinetic energy.
Case study: River Tees
Upper course: Source at Cross Fell (720m); Waterfall at High Force
Middle Course: Tributaries at Barnard Castle (River Balder); Meanders between Barnard
Castle and Darlington; Ox-bow lakes near Yarm
Lower Course: Mouth at Middlesborough
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Quick facts:
Velocity _______________________________________________________________________________
Efficiency_______________________________________________________________________________
_______________________________________________________________________________________
Wetted perimeter________________________________________________________________________
_______________________________________________________________________________________
Hydraulic radius _________________________________________________________________________
_______________________________________________________________________________________
Channel roughness _______________________________________________________________________
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River A - Calculate the:
2m
wetted perimeter:
cross-sectional area:
hydraulic radius:
River B - Calculate the:
12m
wetted perimeter:
cross-sectional area:
RIVER A
hydraulic radius:
4m
RIVER B
6m
Use the words in the ‘Quick Facts’ box to describe the efficiency of a river in:
Its upper course:
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15
For each of the ‘courses’ comment on
the shape, and whether there
is mainly
Upper
Course
erosion, transport or deposition.
Middle Course
Lower Course
Upper Course
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Middle Course
Lower Course
Exam questions
12)
What does the long profile of a river show (3 marks)
13)
What does the hydraulic radius tell you about a river, and how is it
calculated? (3 marks)
14)
Outline how the processes of erosion, transportation and
deposition change along a river’s long profile (6 marks)
15)
Explain how and why a river’s efficiency changes along it’s long
profile (10 marks
Waterfalls
Give a 7 mark account of waterfall formation:
17
:
even bed,
Rapids
Give a 5 mark account of why rapids form:
State where rapids are formed, include hard/soft rock,
cataract (series of rapids), resistant, erosion.
Case study: River Tees
Upper course: Waterfall = High Force. Also associated with
High Force are rapids and potholes.
Meanders
Meanders are formed by erosion and
deposition. Give an account of their
formation (7 marks).
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ver cliff,
Ox bow lakes
Explain the formation of ox-bow lakes using the four diagrams
1)
2)
3)
4)
Use the key terms of erosion and deposition, alluvium, flooding, river
channel, fastest flow, neck of meander in your answer.
Meanders and Ox-bow lakes. An examiner will be expecting you to explain the
formation of these features in detail. Make sure you explain the vertical and lateral
profiles of meanders as they develop.
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Levees and flood plains
These features are formed due to flooding of the river
and deposition of material.
Levee
Flood plain
Description
Explanation of
formation
Braiding
Braiding happens when rivers are carrying a lot of
_________material.
If the river’s ________ drops, or the sediment
_________ becomes too great for the river to
carry it can be ____________ into the channel.
Case study: River Tees
Meanders between Barnard Castle and
Darlington; ox bow lakes near Yarm
Case study: Mississippi River
Levees, flood plains and braiding are a
common feature along the middle course of
the Mississippi River
This causes the river to ________ into many small
__________ channels that eventually rejoin to
form a ___________ channel.
Include the following words:
Single; velocity; load; divide; deposited; winding;
eroded;
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Deltas
You need to be able to describe the formation of
deltas including the following key terms:
Distributary, bottomset beds, foreset beds, topset
beds, mouth, deposition, braiding, alluvium, low
energy.
Have a go…
Deltas
Make sure you research different types of delta: bird’s foot; arcuate, cuspate and estuarine
Case study: Nile delta
This is one of the best examples of a delta as material is deposited into the Mediterranean Sea.
Exam questions
16)
Describe how waterfalls form (7 marks)
17)
Describe and explain the formation of features
formed in the middle course of a river (15 marks)
18)
Describe the formation of levees (4 marks)
19)
Describe the different types of delta and factors
leading to their shape
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River rejuvenation
This occurs if the base level (page 11)
falls. This can happen if there is a fall
in sea level or crustal uplift (land
rises).
The fall in base level means the river
has more potential energy and more
potential to erode vertically.
Distinctive landforms associated with river rejuvenation are:
River terraces; incised and entrenched meanders; knickpoints (e.g., waterfalls and rapids).
For each draw and annotate a diagram to show their formation.
River terraces
Incised meanders,
Knickpoints
Entrenched meanders
Case study: River Rheidol
West Wales, capturing the River Teifi – lots more potential energy in the River Rheidol. Created
waterfalls (Devil’s Bridge) and entrenched meanders.
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You should be able to come up with some obvious causes of flooding. To achieve the highest
marks it is the way you explain your answers as much as your knowledge. Make sure you refer to
the key terms on page 4 in your explanations and link to lag time and discharge.
Use the factors that can cause flooding on page 7 to annotate the following photograph showing
reasons why there could be flooding of this river. Include physical and human factors.
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You should always split impacts into social (affecting people – deaths, disease, homelessness);
economic (affecting businesses/money) and environmental (habitats/natural environment).
Social impacts
Economic impacts
Environmental impacts
You should also be able to split your impacts into short and long term (primary and secondary
effects). Short term/primary effects include damage caused immediately (or very soon afterwards)
and long term/secondary effects include damage to the area over a longer period time
(months/years).
For a case study of your choice describe the impacts of flooding. Be specific!
Exam questions
20)
Outline the physical characteristics of a drainage basin that would
have a high flooding risk (6 marks)
21)
Explain two ways in which urbanisation increases the risk of
flooding (5 marks)
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You will be expected to distinguish between the causes, impacts and responses of floods in LEDC
and MEDC. Choose from one of the case studies we have studied. If you have more information
from past GCSE case studies, you are welcome to use/include this.
Bullet point your answers to make it easier to revise – key facts (e.g., 100,000 people homeless).
Causes
MEDC: Boscastle, UK (2004) or
Carlisle, UK (2005)
or
LEDC: Pakistan (2010) or
Mozambique (2000)
or
1)
1)
2)
2)
3)
3)
4)
4)
Impacts
Social:
Economic:
Environmental:
Responses
(e.g.,
management;
rescuing people;
refugee camps
Exam questions
22)
Using two named examples, compare the impacts of
flooding in poorer and wealthier countries (15 marks)
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Quick facts:
Flood frequency _________________________________________________________________________
_______________________________________________________________________________________
Flood magnitude ________________________________________________________________________
_______________________________________________________________________________________
Recurrence interval______________________________________________________________________
_______________________________________________________________________________________
It is important to know the recurrence rate (how often a flood of a certain magnitude will occur) of
a flood for management purposes.
There is not much point spending millions of pounds to protect a 1 in 1000 year event!
This graph explained:
Floods with higher discharges (e.g., 60
m3/s-1) occur the least often (about
every 15 years)
Note, the scales are logarithmic to
make the relationship between
discharge and recurrence interval easy
to see
Exam questions
23)
Using the figure to the
right, suggest how flood
recurrence could influence
land use planning and
building regulations in flood
plain areas (6 marks)
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Annotate the following pictures to show how they reduce flooding and the advantages and
disadvantages for each.
Case study: Hard engineering – Three Gorges Dam
Yangtze River, China. Seasonal flooding common, however 5 major floods between 1931 and
1998. The 1954 flood killed 33,000 people; the 1998 killed 3000 people.
Work began on the Three Gorges Dam (one of 46 dams along river) to control the flow. Use the
table below to bullet point the positive and negative impacts of this development. Think SEE!
Positive effects
1)
Negative effects
1)
2)
2)
3)
3)
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Annotate the following pictures to show how they reduce flooding and the advantages and
disadvantages for each. Clockwise order: flood plain zoning; afforestation; change in urban
surfaces; wetland conservation (managed retreat).
Case study: Soft engineering – Mozambique (2010 floods)
Flooding of Limpopo River in Mozambique (refer to page 22) due to prolonged rainfall in southern
Africa and Cyclone Eline. Country to poor for typical hard engineering strategies and want periodic
flooding to create fertile flood plains for farming.
Instead: weather prediction, solar-powered radios, nominated leaders in times of flooding,
practice flooding drills, map of local community and safe places.
Exam questions
24)
With reference to named examples, discuss the success of
different engineering approaches to flood prevention (15 marks)
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Key Term
Definition
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Use this space to make notes – perhaps things you need to focus on for your revision.
You could also attempt some of the exam questions in this space…
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