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This is revision notes for the Edexcel GCSE Geography course for River Landscapes. It involves case studies, types of erosion, diagrams, and formations of different features of a river.
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River Landscape Revision
Key words
Mouth – the point at which a river ends. This is when the river enters the sea.
Source – the point at which a river starts. It usually starts in a valley or mountain.
Tributary – a stream or river which flows into another river.
Confluence – it’s the meeting point of the tributary and the river.
Watershed – the line of high relief that separates the drainage basins.
River drainage basin
source – the point where
the river starts
watershed – the line of high relief
that separates the drainage basin.
confluence – it’s the meeting point of a
tributary and the river
mouth – the point where
the river enters the sea
river basin
tributary – a stream or river which flows into
another river. It doesn’t flow directly into the
sea.
river channel
Types of erosion
Types of erosion
Hydraulic actionWhen water causes air to be trapped in the cracks
of the river bed and banks. The trapped air
expands and causes the material to break off.
CorrasionWhen the material in the water rub together with
the river bed or bank and causes it to wear away.
It’s like a sandpaper action.
AttritionWhen the material in the
water bang into each other and causes the
material to break down into smaller particles.
CorrosionWhen soluble materials
dissolve in the water.
Types of weathering
Types of weathering
Physical weatheringWhen water in the cracks are frozen and due to the
low, freezing temperature, it will cause pressure around the rock
and may break off.
Chemical weatheringIf the rain water contains
acid (acid rain), it will break down certain rocks
such as limestone.
Biological weatheringSeeds that fall in the
cracks will grow and put force on the rock.
Animals that burrow in cracks will also put force
on the rock.
Types of mass movement
Types of mass
movement
Soil creepIt’s the slow downhill
movement of soil due to gravity. The moisture in the soil and gravity will
pull it down.
SlumpingIt’s the fast movement of
a large area of land moving down a slope. The soil gets saturated
with water and gets pulled down by gravity.
LongprofileofaRiver
Lower courseLow gradient (flat
land)
High discharge and high velocity due to the large amount of water in the river.
River channel is wide and deep as it moves towards the
sea.
Middle courseGradient decreases.
Discharge and velocity increases as the
amount of water in the river increases.
River channel gets wider and starts to
meander.
Upper courseSteep gradient as river
starts in an area of high relief.
Low discharge and velocity as there is not
much water.
River channel is narrow.
Formation of a Meander & Ox-bow Lake
All the water is directed towards the outside of the bend. This causes erosion of the outer bend and a river cliff will form. On the inside of the bend, deposition will occur and a slip-off slope will form. This happens in the middle course.
An ox-bow lake is formed when the neck of the meander grows narrower and narrower due to erosion. When the river floods, it breaks through the meander neck and takes an easier course. Deposition occurs along the edge of the new river course and the meander will cut off from the river. This happens in the middle course.
Formation of a Waterfall
The water will erode the soft
rock and leave the hard rock,
forming an overhang. As erosion
continues, it will form a plunge
pool. Eventually, the overhang
will collapse due to hydraulic
action and the water will
retreat. A gorge is formed. This
happens in the upper course of
the river.
Formation of a V-shaped valley/interlocking spurs
As the river flows, it cuts
downwards due to low river
discharge. This sis called vertical
erosion. The soil and rocks are then
attacked by weathering processes.
Eventually, it will slip down the slop
into the river. Weathering and
erosion continue to widen and
deepen the valley into the shape of
a V. As the river flows, it erodes the
soft rocks however winds its way
around the hard rocks.
Formation of a levee
When a river’s banks burst, the land besides the river will flood, this is a flood plain. The river will deposit material called alluvium. This consists of heavy material such as pebbles, medium weight material such as sand and lightweight material such as silts and clay. These materials create a levee. This happens in the lower course of the river.
Flood Risks
Human causes Physical causes
Deforestation - plants and trees lower
the amount of water that reaches the
river channel and slows down how
long it takes for the water to reach the
river channel. It increases the risk of
flooding.
Heavy rain - This means there will be
lots of water in the drainage basin and
the water table will be high. It
increases the risk of flooding.
Building a dam - This allows you to
control the amount of water entering
the river. If there is a lot of rain you
can reduce the amount of water you
let in the river channel. It decreases
the risk of flooding.
Permeable rock - If the water soaks
through the rock, it takes longer to get
to the river channel. This slow
response lowers the risk of a flood.
Urban Development - Building on the
floodplain will mean all surfaces are
impermeable. This means when it
rains, water will flow into the river
channel quickly. This increases the risk
of flooding
Hot, sunny weather - This means there
will be ore evaporation, therefore
lowering the overall water level. It
decreases the risk of flooding.
Building roads - This increases the
amount of impermeable surface and
the roads can quickly carry the water
to the river. This increases the risk of
flooding.
Lots of tributaries - This will mean the
rain water reaches the river channel
quickly. This is because the water
travels quickly to the main river
through streams and smaller rivers.
This increases the risk of a flood.
Case study: Boscastle Flood of 2004
Boscastle is located in Cornwall which is in the south west of England.
Human causes of flood Physical causes of flood
• Deforestation on drainage basin• Built buildings and roads, making
the surface impermeable
• 20mm of rain throughout the afternoon (heavy rain)
• The River Valancy and Jordan meet, doubling the volume of water
• The river bursts its banks
Effects of the flood• Many cars were washed away• Local shops and buildings were damaged• Up to 60% of income was lost because they rely on tourism
during the summer• Sections of South West Coast Path had to be closed• A car park had to be rebuilt• Trees were washed away
Responses to flood• Residents were airlifted by helicopters• Sections of South West Coast Path had
to be closed• Infrastructure had to be rebuilt
River defencesHard Engineering Technique Description Advantages Disadvantages
Embankments Raised banks along the river To make it more difficult to flood due to the high relief. It’s natural.
Unsafe for children. Takes up space. Sometimes not high enough.
Channelisation Channel may be widened, deepened or straightened to carry more water
Reduces risk of flooding. Can lead to greater flooding downstream.
Flood relief channels Channel may be altered to divert water away from settlements
Water is diverted, protecting residents. Requires large amount of land. Expensive.
Dams Controls amount of water in river Water stored in reservoir behind dam. Can generate hydroelectricity.
Expensive. Erosion downstream.
Flood walls Vertical barrier made from concrete Can be used where space is limited. Has to be assembled well.
Storage areas Will fill with water if river floods – areas next to river
Natural looking. Doesn’t damage environment.
Only comes into use when river is flooded.
Soft Engineering Technique Description Advantages Disadvantages
Floodplain zoning Controlling development next to rivers Cheap. Reduces impact of flooding. Can’t build on that land. No one is able to live there.
Washlands River allowed to flood naturally in wasteland areas
Nothing is built. Provides wetland for birds and plants. Agricultural land.
Can’t be built on. Marshlands are formed.
Warning systems Sirens which give people early warnings of flood events
Cheap. Not enough time for residents to prepare.
Afforestation Plant trees to slow down rainfall reaching river
Increases fire risk.
Case study: River Nene in Northampton, UKHeavy rain on the 9th of April, 1998, caused the river to overflow. 2 people died as a result.
Management Technique 1A clay flood embankment raised the land by 6.8m in 2002. It cost £2 million. It’s a hard engineering technique.
Management Technique 2The warning system was upgraded by the environment agency, providing 2 hours notice. It’s a soft engineering technique.
Management Technique 3A flood retention reservoir to control water. It’s a hard engineering technique.
Management Technique 4A washland was created in 2007 to divert the water and reduce flooding. It cost £8 million. It’s a soft engineering technique.
Management Technique 54m floodwalls were installed near Northampton Railway Station. Gabion boxes protect the banks from erosion. It’s a hard engineering technique.
The managements have allowed a new housing estate to be built on the flood plain.