Water Use this PowerPoint to complete the brainstorm on the topic of

‘Water’

Processes

• What three main process operate on a river?

Video - http://www.bbc.co.uk/schools/gcsebitesize/geography/water_rivers/river_processes_video.shtml

Video - http://www.bbc.co.uk/schools/gcsebitesize/geography/water_rivers/river_processes_video.shtml

Erosion (4 types) Hydraulic Action•This process involves the force of water against the bed and banks. Abrasion (Corrasion)•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. Corrosion•This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks.

Can you remember the Kung Fu moves?(these will help you to remember the meaning of each word)

Do you know your processes of erosion?

Transportation (4 types)

Material floats in the water and are carried by the flowing water

Some materials dissolve in water (e.g. Limestone and are carried by the

flowing water

Material is rolled along the river bed by the flowing water

Material bounces along the river bed by the flow of the water

How is material transported downstream?

The Drainage Basin

Source

Mouth

Tributary

Confluence

Watershed

Landforms • Landforms found along the course of a river can be created

by either erosion, deposition or a combination of both. • Video -

http://www.bbc.co.uk/schools/gcsebitesize/geography/water_rivers/river_landforms_video.shtml

• Waterfalls • Delta• Meanders• Levees• V-shaped valleys

Only learn two landforms in detail

Waterfalls

• A waterfall is usually found in the upper course of a river• It occurs when a layer of hard rock overlies a layers of softer rock• The hard rock is less easily eroded creating a steep slope and rapids.• Eventually a drop develops over which the water falls

Waterfall formation

Waterfalls

Delta

• A delta is found at the mouth of a river. • When a river enters the sea, it loses energy

and can no longer carry as much material. Its load it deposited. If this happens at a fasters rate than at which the sea can remove the material, a delta is formed

• Deltas can provide rich farm lands but often suffer flooding e.g. Bangladesh

Delta

Distributaries

Meanders and oxbow lakes

• A meander is a bend in a river formed by lateral erosion (sideways)

• Meanders are found in the lower course of a river

• Created through erosion and deposition

A cross section through a meander

Outside bend – Fastest Flow (erosion)Inside bend - slowest flow (deposition)

This causes the bend to migrate (lateral erosion)

Oxbow lakes

V-shaped valleyVertical erosion

Interlocking spurs

V-shaped valley

Floodplains and Levees

• These are found in the lower course of a river close to the mouth

• As a river nears the mouth it has a large discharge and the river channel is deep and wide. The valley is also wide with an extensive flood plain.

• Each time the river floods, silt is deposited on the floodplain. Creating fertile soils.

• Natural levees are raised banks of deposited material found either side of the river channel.

Floodplains

Flooding

Flooding is an important issue relating to rivers. •You will need to understand how water moves through a drainage basin. •You will also need to be able to explain how humans change the flow of water in a drainage basin and therefore can increase the risk of flooding

Videos 1.http://www.bbc.co.uk/schools/gcsebitesize/geography/water_rivers/river_flooding_management_video.shtml2.http://www.bbc.co.uk/learningzone/clips/river-flooding-in-britain-causes-and-effects/5865.html

Videos 1.http://www.bbc.co.uk/schools/gcsebitesize/geography/water_rivers/river_flooding_management_video.shtml2.http://www.bbc.co.uk/learningzone/clips/river-flooding-in-britain-causes-and-effects/5865.html

Movement of water in the drainage basin

river

evapotranspiration

precipitation

throughflow

surface runoff

groundwater flowwater table

interception

percolation

infiltration

Key words - explainedInfiltration – down ward movement of water through the soil Percolation – downward movement through the ground (rocks)Surface runoff – when water flows over the surface of the soil Through flow – when water flows through the soil Ground water flow – when water flows through the ground (rocks) Saturation – this happens to the soil when no more water can infiltrate the soil (leads to surface runoff)Interception – trees and vegetation intercept water by catching rain in their leaves Transpiration – trees breathing out water as a gas Evapotranspiration – water that evaporates off the surface of tree leaves

Causes of flooding Human causes Deforestation Reduces water stored, water lost to the atmosphere in transportation and evapotranspirationRemoving trees increases infiltration into the soil and increases discharge in rivers Building on the floodplain Surfaces like tarmac can decreases infiltration and increases surface runoff. Resulting in more water getting into a river faster increasing the risk of flooding.Climate change Global warming has resulted in sea level rise and more incidents of extreme weather making flooding more likely and more sever in the future

Physical causes Heavy rainfall Increase the amount of discharge in a river. Steep valley sidesWater travels at a faster velocity (speed) in the drainage basin and gets into the river channel faster causing river levels to rise fasterRock type Some rocks do not absorb water and therefore less water will be stored into the rocks. Resulting in increased water in the river channel Number of tributariesLess tributaries means that the river has less capacity to hold water and therefore more likely to flood.

Rising limb

Falling limb

Peak discharge

Peak rainfall

Write a definition of lagtime.Calculate the lagtime shown on this hydrograph.

storm flow

normal (base) flow

Hydrographs

I = Lagtime

Hydrographs

What affects the shape of a hydrograph?

Land use

Type and amount of precipitation

Geology and soil Gradient of the valley sides

Drainage density

Flood management

• Flooding can be managed in a variety of ways, these can be divided into hard engineering and soft engineering approaches

Remember in the exam to give examples of where these things have been done.

See Boscastle casestudy

Hard Engineering

Soft Engineering

For flood management • Some people argue flooding should be

managed. This is because: - – Flooding can result in thousands of pounds worth of

damage– It can threaten peoples lives – Business and peoples livelihood can be damaged. Local

economy will lose money. – Floods can affect large numbers of people in urban areas– Flooding can last weeks and the effects can last months even

years– Disruption to schools, roads, and businesses

Against flood management • Some people argue flooding should not be

managed. This is because: - – Flood defences are expensive and can result in

council tax being increased. This might mean someone who is not affected by flooding having to pay for flood defences.

– Flood defences are only put on one small part of a river channel (too expensive to put all along a river)

– Some flood defences can result in greater risk of flooding further downstream.

How do the rivers affect people lives?

Learn two casesudies for this question. 1.Tourism – Niagara Falls 2.Flooding – Boscastle

Tourism – Niagara FallsBenefits Tourism

• Jobs created • Boosted local economy • Local facilities improved

Costs Tourism

• Congestion on roads• Littering• Crime rate increases (pick

pockets)• River pollution (boats)

Flooding – Boscastle

Video - http://www.bbc.co.uk/learningzone/clips/why-did-boscastle-flood/14072.html

Video - http://www.bbc.co.uk/learningzone/clips/why-did-boscastle-flood/14072.html

What factors increased the risk of flood in Boscastle ?

What factors increased the flood risk?

Effects of the Boscastle flood

Management of flooding in Boscastle

• Low bridges where raised • The river channel was made deeper • The river was straightened in parts • Small amounts of afforestation in Boscastle

and surrounding area

How do the rivers affect people lives? - The floodplain

• Provide ideal land for farming. The soil tends to be very fertile so crops can be grown Or if flooding is frequent the land can be used for pastoral animals.

• Provide flat land that can easily be built on. Many homes in the UK are built on the floodplain of rivers.