rivers revision booklet

16
RIVERS RIVERS REVISION REVISION BOOKLET BOOKLET GCSE GCSE GEOGRAPHY GEOGRAPHY Content Revised? Rivers

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Booklet containing information for Rivers as required for GCSE Geography

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Page 1: Rivers revision booklet

RIVERSRIVERS REVISIONREVISION BOOKLETBOOKLET

GCSEGCSE GEOGRAPHYGEOGRAPHY

Page 2: Rivers revision booklet

The River System/ Water CycleThe River System/ Water Cycle

Content Revised?Rivers

The units and links in the hydrological cycle.

The storm hydrograph and how it responds to changes.

The river basin as a system of inputs, flows, stores and outputs.

Physical causes of river flooding.

The activities of people that can cause river flooding.

Use of GIS, new technologies, satellite images, aerial photographs and data in a variety of contexts to highlight flood management schemes and their effectiveness.

How weathering, erosion, transport and deposition operate in a river basin.

The formation of fluvial landforms, including meanders, interlocking spurs, floodplains, river cliffs, valleys, waterfalls with appropriate examples.

Case study Named exampleTheme 1 Rivers and Coasts

A MEDC case study to illustrate the causes, effects and management of river flooding. A LEDC case study to illustrate the causes, effects and management of river flooding. A case study of one river valley and its landforms.

Page 3: Rivers revision booklet

Drainage Basin TerminologyDrainage Basin Terminology

EXAM PRACTICE

Fill in the boxes using these words:

Air Condensation CloudsPrecipitation Transpiration PercolationGroundwater Ocean Run-off Evaporation

Page 4: Rivers revision booklet

1 Study the diagram which shows part of the hydrological cycle.

(a)(i) Name the processes labelled 1 and 2 in the diagram. (2 marks)

(ii) Describe the difference between processes A and B. (2 marks)

(b) Describe how the water vapour shown in the diagram becomes water on the land at the point labelled 4.

(3marks)

(c) Describe two stores of water in the hydrological cycle that are not labelled in the diagram. (4 marks)

(d)(i) Name the process labelled 6 in the diagram. (1 mark)

(ii) Suggest how the water moved by process 6 could end up in the sea. (4 marks)

Match Up these Definitions(use the diagram on the previous page to help you if necessary)

Page 5: Rivers revision booklet

Drainage basin a stream or smaller river which joins a larger stream or river

Catchment area the edge of highland surrounding a drainage basin.

It marks the boundary between two drainage basins

Watershed the area of land drained by a river

Source the point where the river comes to the end, usually

when entering a seaConfluence - The beginning or start of a

riverTributary the area within the drainage

basinMouth the point at which two rivers or

streams join

River ProfilesRiver Profiles

A river changes shape as it flows from its

source (where a river starts) to its mouth

(where a river flows into a sea or lake).

The shape

of both the

long profile

(a slice

through the

river from

source to

mouth) and the cross profile (a slice across the

river) changes.

Spot Test!Spot Test!

A slice through a river from source to mouth is called what?

Long profile

Cross profile

Page 6: Rivers revision booklet

Cross section

Steep profile

A typical cross profile in the upper course will be:

wide and deep.

narrow and shallow.

narrow and deep.

wide and shallow.

Erosion

Erosion involves the wearing away of rock and soil found along the river bed and banks. Erosion also

involves the breaking down of the rock particles being carried downstream by the river.

Match up the four main forms of river erosion

Hydraulic action rocks carried along by the river wear down the

river bed and banks

Abrasion soluble particles are dissolved into the river

Attrition rocks being carried by the river smash together

and break into smaller, smoother and rounder

particles

Solution the force of the river against the banks can

cause air to be trapped in cracks and crevices.

The pressure weakens the banks and gradually

wears it away

Match up the four different river transport processes (use diagram on following page

only if you NEED to).

Solution small pebbles and stones are bounced along the

river bed

Suspension fine light material is carried along in the water

Saltation large boulders and rocks are rolled along the

river bed

Traction minerals are dissolved in the water and carried

along in solution

TRANSPORTATAIONTRANSPORTATAION

Page 7: Rivers revision booklet

Rivers need energy to transport material, and levels of energy change as the river moves from source

to mouth.

When energy levels are very high, large rocks and boulders can be transported. Energy levels are

usually higher near a river's source, when its course is steep and its valley narrow. Energy levels

rise even higher in times of flood.

When energy levels are low, only small particles can be transported (if any). Energy levels are

lowest when velocity drops as a river enters a lake or sea (at the mouth).

River Processes Test - Underline the correct answerRiver Processes Test - Underline the correct answer

1. Which of the following is NOT a type of river erosion?

Solution or corrosion Abrasion Percolation Hydraulic action Attrition

2. When rocks and pebbles being carried by the river knock together and are broken

down to form smaller particles this is called:

Corrosion Abrasion Percolation Hydraulic action Attrition

3. When the force of the water being carried by the river wears away the bed and

banks this is called:

solution or corrosionabrasion percolation hydraulic action attrition

4. Which of the following statements about deposition is NOT correct?

Page 8: Rivers revision booklet

Deposition is more common at the source of the river.

Deposition occurs when a river loses energy.

Deposition may occur when the river is shallow.

Deposition may occur when the volume of water decreases.

5. Erosion is vertical or downwards:

at the source of a river

at the mouth of a river

6. A wide river channel is formed:

at the source of a river

at the mouth of a river

River LandformsRiver LandformsUpper-courseUpper-course river features include steep-sided V-shaped valleys, interlocking spurs, rapids,

waterfalls and gorges.

Middle-courseMiddle-course river features include wider, shallower valleys, meanders, and oxbow lakes.

Lower-courseLower-course river features include wide flat-bottomed valleys, floodplains and deltas.

Upper Course FeaturesUpper Course Features

As the river moves through the upper course it cuts

downwards. The gradient here is steep and the river

channel is narrow. Vertical erosion in this highland part of

the river helps to create steep-sided V-shaped valleys,

interlocking spurs, rapids, waterfalls and gorges.

As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard

rock. This creates interlocking spurs, which look a bit

like the interlocking parts of a zip.

When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form

Middle course features

Meanders

In the middle course the river has more energy and a high

volume of water. The gradient here is gentle and lateral

(sideways) erosion has widened the river channel. The river

Page 9: Rivers revision booklet

channel has also deepened. A larger river channel means there is less friction, so the water flows

faster:

As the river erodes laterally, to the right side then the left side, it forms large bends, and then

horseshoe-like loops called meanders.

The formation of meanders is due to both deposition and erosion and meanders gradually migrate

downstream.

The force of the water erodes and undercuts the river bank on the outside of the bend where water

flow has most energy due to decreased friction.

On the inside of the bend, where the river flow is slower, material is deposited, as there is more

friction.

Over time the horseshoe become tighter, until the ends become very close together. As the river

breaks through, eg during a flood when the river has a higher discharge and more energy, and the ends

join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.

Lower course features

In the lower course, the river has a high volume and a large discharge. The river channel is now deep

and wide and the landscape around it is flat. However, as a river reaches the end of its journey, energy

levels are low and deposition takes place.

Floodplains

The river now has a wide floodplain. A floodplain is the area around a river that is covered in

times of flood. A floodplain is a very fertile area due to the rich alluvium deposited by

floodwaters. This makes floodplains a good place for agriculture. A build up of alluvium on the

banks of a river can create levees, which raise the river bank.

Deltas

Deltas are found at the mouth of large rivers - for example, the Mississippi. A delta is formed

when the river deposits its material faster than the sea can remove it. There are three main

types of delta, named after the shape they create:

HyrdrographsHyrdrographs

3

Dis

charg

e

(m3/s

)

Basin lag time Peak

flow

Page 10: Rivers revision booklet

Case Study – MEDC Case Study to illustrate the causes, effectsCase Study – MEDC Case Study to illustrate the causes, effects and management of river floodingand management of river flooding

BOSCASTLE - The Boscastle Flood (Cornwall) on 16th August 2004 

Why the flood risk?

Human Factors A bridge caused a blocking point until it gave way.

Physical Factors

Page 11: Rivers revision booklet

The cause was torrential rain, as over 1 months worth fell in just 3 hours. Warm moist air had moved in from the Atlantic and condensed into thunder clouds. The catchment area of Bodmin Moor was already saturated through earlier rainfall, so run-off

was immediate. 3 tributaries all converge above the village, and the steep slopes created a raging torrent.

ImpactsSocial

Whilst no people died, the flood caused serious problems in the small town. Bridges were washed away and over 80 cars were swept along, many of them were tourist’s

cars who were parked at the head of the village.Economic

The unique witchcraft museum was totally lost. As many locals ran bed and breakfast businesses, their summer was ruined as it was over a year

before they could re-open. Some had no insurance and never re-opened. The emergency services were over stretched and subsequently, the local council have had to

spend huge sums of money introducing flood prevention schemes such as channel straightening and building holding dams (also called check dams).

Over 20 houses were badly damage, with many being beyond repair.

Managing the flood risks1. Channel modification – River Valency – widened and deepened so it can carry higher flows of

water. Lower river bed by an average 0.75m. Widen river channel next to the Riverside Hotel; move back the patio and replace and extend the footbridge.

2. Removal of large bridge that acted as a block for debris and the fast flowing water3. Encourage landowners to maintain vegetation cover on valley sides and remove any dead trees4. Form wide river channel upstream of the car park to create an area of slower flow where larger

sediment will deposit and the river can spread out

Case Study – LEDC Case Study to illustrate the causes, effectsCase Study – LEDC Case Study to illustrate the causes, effects and management of river floodingand management of river flooding

Bangladesh is a low lying country most of which lies on the delta of Ganges, Brahmaputra and Meghna.

Why the flood risk?

Physical factors:

Sources of rivers are in Himalayas so snowmelt adds to the discharge during spring.

S Asia has a monsoon climate and experiences a wet season between May and September when low

pressure and winds blowing from SW across Bay of Bengal bring heavy rain to coastal regions.

Page 12: Rivers revision booklet

Bangladesh also suffers from cyclones that bring high winds, heavy rainfall and storm surges.

Human Factors:

Urbanisation - the capital city Dhaka now has a population of more than 1 million people

Rapid deforestation in Himalayas has had a negative effect on rates of interception and

evapotranspiration resulting in more water reaching the rivers.

River management is difficult to implement in LEDCs. Average GDP per capita is around $300.

Population rely on subsistence agriculture to survive growing rice on rented plots of land so there is

little income from taxation for Government and Bangladesh relies heavily on foreign aid to finance

large scale development project which might help prevent floods.

In 2004 the monsoon season brought more rainfall than usual.

Impacts

Social impacts:

36 million people were made homeless

By mid September the death toll had risen to 800. People died as a result of disease because they had

no access to clean water.

Landless labourers and small farmers were the most severely affected in rural areas and in the urban

areas it was typically the slum dwellers squatting on poorly drained land who suffered the most.

Economic impacts:

Flood also caused serious damage to infrastructure – roads, bridges, embankments, railway lines,

irrigation systems

All domestic and internal flights had to be suspended during July

Road and rail links into Dhaka were severely affected

Value of damage was assessed as being in region of $2.2 billion of 4% of total GDP for 2004

Environmental impacts:

During July and August approximately 38% of the total land area was flooded including 800,000 ha of

agricultural land and Dhaka

Floods caused river bank erosion especially on embankment areas close to the main channels, soil

erosion, water-logging, water contamination

Page 13: Rivers revision booklet

Responses

Short term responses

The government working with non-governmental organisations provided emergency relief: rice,

clothing, medicines, blankets and towels

In July the United Nations activated a disaster management team to coordinate the activities of the

various UN agencies. They supplied critical emergency supplies and conducted a ‘damage and needs

assessment’ in affected areas.

Bilateral aid from individual countries was directed to the UN team.

Self help schemes – local people worked together to rebuild their properties and communities.

Long – term responses

Long term responses to major floods are largely dependent on foreign aid from both official and

unofficial sources. Previous river management schemes implemented by foreigners and funded by aid

have proved to be inadequate. These schemes paid little attention to knowledge of rivers and many

attempts at river management failed

Recent small scale community based projects have resulted in lives being saved. Food shelters and

early warning systems have been successfully put in place.

Following the 2004 floods additional financial aid was granted for a period of 5 years. This was mainly

in the form of a loan from the World Bank to pay for repairs to infrastructure, water resource

management and education.

And the future?

Disaster preparedness is a key priority for the future. This includes flood management and improved

water resources. It is also planned that flood-resistant designs should be used in all social and

economic infrastructure projects

Why are the effects of river flooding usually greater in an LEDC than in an Why are the effects of river flooding usually greater in an LEDC than in an MEDC?MEDC?

1. Less money to spend on tackling problems so less flood protection measures to prevent the

same effects happening again.

2. Difficult to get to affected area due to lack of transport links which would require plenty of

money to improve road networks and other transport links

3. People are attracted to living on fertile flood plains in LEDCs because farming is an important

part of their economy and the alluvium (silt) deposited on the floodplain during floods is a very

good and cheap fertiliser for crops.