RIVERS Revision Booklet

AS LEVEL GEOGRAPHY

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Checklist:

I can… No Sort of YesDraw 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 hydrographDescribe 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 featuresExplain 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 landformsExplain the physical and human causes of flooding and relate this to a case studyExplain the social, environmental and economic impacts of flooding and relate this to a case studyCan compare the causes and impacts of flooding between LEDC and MEDC case studiesExplain 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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Key Term MeaningTranspirationInterceptionInfiltrationPercolationThroughflowSurface run-offPercolationEvaporationCondensationPrecipitation

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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

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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 questions1) 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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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)

A B

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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:

Exam questions4) Give the lag time and peak discharge for the river

shown to the right (2 marks)5) How might deforestation of this drainage basin

affect its storm hydrograph? Explain your answer. (4 marks)

Erosion type Explanation

C or A

H A

C or S

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12:0

013

:00

14:0

015

:00

16:0

017

:00

18:0

019

:00

20:0

0

020406080

100120

0

5

10

15

20Boscastle hydrograph

Label the diagram above with the four types of fluvial erosion

A

Transport type Explanation

Traction

Saltation

Suspension

Solution

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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?

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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 (10-50mm) 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.

Exam questions6) 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)

Disadvantages of the Hjulstrom curve:

1) Velocity – where?...

2) Shape of load…

3) Density of load…

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Label on the diagram where the following features would be found:

Waterfall Delta GorgeMeander Ox-bow lake DistributaryRapids V-shaped valley Flood plainPotholes Estuary 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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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

Quick facts:

Velocity _______________________________________________________________________________

Efficiency_______________________________________________________________________________

_______________________________________________________________________________________

Wetted perimeter________________________________________________________________________

_______________________________________________________________________________________

Hydraulic radius

2m

4m

12m

6m

RIVER ARIVER B

River A - Calculate the:

wetted perimeter:

cross-sectional area:

hydraulic radius:

River B - Calculate the:

wetted perimeter:

cross-sectional area:

hydraulic radius:

Use the words in the ‘Quick Facts’ box to describe the efficiency of a river in:

Its upper course:

Its middle course:

Its lower course:

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Upper Course Middle

CourseLower Course

Upper Course

Middle Course Lower Course

Exam questions12) 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

For each of the ‘courses’ comment on the shape, and whether there is mainly erosion, transport or deposition.

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Waterfalls

Give a 7 mark account of waterfall formation:

Be sure to include and explain abrasion, hydraulic action, not just the word ‘erosion’.

Case study: River Tees

Upper course: Waterfall = High Force. Also associated with High Force are rapids and potholes.

Give a 5 mark account of pothole formation:

Include terms such as corrosion, drilling, uneven

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.

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Meanders

Meanders are formed by erosion and deposition. Give an account of their formation (7 marks).

Cross-profile of a meander. Include slip off slope, river cliff, fastest flow, erosion and deposition

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.

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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.

Levees and flood plains

These features are formed due to flooding of the river and deposition of material.

Levee Flood plainDescription

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.

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;

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

Deltas

You need to be able to describe the formation of deltas including the following key terms:

Distributary, bottomset beds, foreset beds,

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Case study: Nile delta

This is one of the best examples of a delta as material is deposited into the Mediterranean Sea.

Exam questions16) 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

Deltas

You need to be able to describe the formation of deltas including the following key terms:

Distributary, bottomset beds, foreset beds,

Deltas

Make sure you research different types of delta: bird’s foot; arcuate, cuspate and estuarine

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).

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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).

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.

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

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Social impacts Economic impacts

Environmental impacts

For a case study of your choice describe the impacts of flooding. Be specific!

Exam questions20) 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)

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).

MEDC: Boscastle, UK (2004) or Carlisle, UK (2005)or

LEDC: Pakistan (2010) or Mozambique (2000)or

Causes 1)

2)

3)

4)

1)

2)

3)

4)

ImpactsSocial:

Economic:

Environmental:

Responses(e.g., management; rescuing people; refugee camps

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Quick facts:

Flood frequency _________________________________________________________________________

_______________________________________________________________________________________

Flood magnitude ________________________________________________________________________

______________________________________________________________________________________

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Quick facts:

Flood frequency _________________________________________________________________________

_______________________________________________________________________________________

Flood magnitude ________________________________________________________________________

______________________________________________________________________________________

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 questions23) Using the figure to the

right, suggest how flood recurrence could influence land use planning and building regulations in flood plain areas (6 marks)

Annotate the following pictures to show how they reduce flooding and the advantages and disadvantages for each.

Positive effects Negative effects1)

2)

3)

1)

2)

3)

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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!

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).

Key Term Definition

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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 questions24) With reference to named examples, discuss the success of

different engineering approaches to flood prevention (15 marks)

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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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