Impact of Human Activities on River Processes

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Impact of Human Activities on River Processes

• 5th year Geography
• Ms Carr

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Learning Intention

• Examine and discuss three examples of how human
  activities can impact on river processes.
• Hydroelectric Dams
• Canalisation
• Flood Control Measures
• Identify typical exam questions on the topic.
• Structure an essay style model answer on the
  topic.

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Hydro-Electric (HEP) Dams

• Built across rivers to control flow of water
• Reservoir- water storage area behind the dam
• Base of dam wall- water builds up
• Penstock- pipe inside the dam, gravity forces
  water through
• Force of moving water turns a turbine propellor
• Shaft connects the turbine to a generator
• Generator produces HEP
• HEP supplies power lines with electricity
• Textbook page113 114

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Hydro-Electric (HEP) Dams

• Positive
• Generation of electricity
• Supply of water
• Controlling the effects of flooding
• The reservoir can be used for recreational
  purposes and also for aquaculture

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Hydro-Electric (HEP) Dams

• NegativeRelocation of people
• Natural flooding does not occur down river- lack
  of alluvium
• Reduction in the number of species living in the
  river ecosystem

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Case Study

• Three Gorges Dam
• Yangtze River, China
• Largest HEP dam in the world
• Completed in 2011

Advantages Disadvantages
Electricity Reduces pollution (no coal) Reduces flooding/ erosion Tourism Relocation 1.3million people Flooding archaeological sites Increase risk of landslides
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Video Clips

• Impact of Yangtze River Floods.
• n 1998, floods caused 500m of damage in a small
  rural county. If the great cities along China's
  Yangtze Valley were to flood, the cost would be
  astronomical
• A dam at Three Gorges?
• Three Gorges Dam- Environment.
• The new dam on China's Yangtze River will change
  the river ecology. The nearby Gezhouba Dam gives
  some clues to the environmental impact it will
  have. The signs are not good

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Canalisation

• Canals Human-made, inland waterways.
• Positive
• Efficient water transport
• Irrigation purposes
• Negative
• No alluvium deposits
• High salt levels, kill fish
• Case Study
• Shrinking of the Aral Sea, Central Asia
• Textbook page 115

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Flood Control Measures

• Levees
• Deposited material on either side of river
  channel in old age stage
• Artificial Levees
• Built to help prevent flooding
• Limit flow of river
• River flows faster in narrow channel
• Deposition on river bed
• Building artificial levees may be seen as
  interfering with natural processes, but it can
  prevent flood damage in the surrounding areas.
• Case Study
• Mississippi, USA
• 15 metres high
• Flood control failure 2005 Hurricane Katrina, New
  Orleans
• Textbook page 116

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River Rhine Case Study

• One of the longest and most important rivers in
  Europe
• Length approximately 1,232 km (766 miles)
• Source in the Swiss Alps
• Flows through six countries Switzerland,
  Liechtenstein, Austria, Germany, France, the
  Netherlands
• Enters the North Sea at Rotterdam, the
  Netherlands
• Main tributaries are the Main, Necker and Moselle

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Features

• One of the main traffic arteries of Western
  Europe
• An important means of transporting and shipping
• Canal network developed around the river course
• Dykes constructed to prevent the likelihood of
  flooding
• Meanders bypassed by the construction of new
  canals and channels
• Resulted in a shorter, deeper and straighter
  river course

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Impact of Changes to River Course

• Dykes/ Articial Levees
• Land is utilised for agricultural purposes and
  buildings have also been constructed on the
  floodplain
• Dykes have been constructed and are regularly
  increased in size to protect the surrounding
  agricultural land and buildings
• Prevent the river flooding over its banks at dyke
  locations resulting in flooding being transferred
  further downriver
• River cannot deposit onto its floodplain and so
  deposits sediment onto the river bed
• Raises the level of the river
• Dykes must be regularly upgraded to match the new
  river height

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• Impact of changes to river course
• Shipping
• Areas of the River Rhine were narrowed to create
  a deeper river channel to allow larger ships to
  travel through
• Rhine travels through polders in the Netherlands
  between high embankments
• Embankments absorb water
• Embankments may eventually collapse resulting in
  the surrounding land being flooded

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• Impact of changes to river course
• HEP
• Thirteen hydroelectric power stations constructed
  along the river
• Contributed to increased flooding along the
  course of the river
• Power Project involved the construction of a new
  section of river running parallel to the old
  River Rhine course

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• Outcome of changes to river course
• Dams trap sediment, which reduce the rivers load
• Created a faster and deeper river
• Flooding frequency and water flood levels
  increased over the last 100 years
• Plan to tackle the problem by restoring 100
  artificial channels and 11,000 km of river bank

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Exam Question...2012
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Exam Question...2011
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Exam Question...2010
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