Hard and soft engineering

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Hard Engineering Techniques

  • build flood banks
  • straighteneing and deepening the river
  • dams and reservoirs
  • flood walls
  • storage areas
  • barriers
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Flood Banks

  • raise the banks of the river so it can hold more water
  • relatively cheap, one-off costs
  • looks unnatural, increases flood risk downstream (moves water quickly)
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straightened and deepening of the river

  • straightening - spped up flow of water
  • deepening - dredge river so it can hold more water
  • dredging needs to be done every year, lining with concrete is expensive, increases risk of flooding downstream
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dams and reservoirs

  • trap and store water, release it in a controlled way
  • can be multi-purpose - generate electricity
  • very expensive, huge changes to the ecosystem
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flood walls

  • built around settlements, industry and roads
  • effective if the flood isn't too extreme
  • expensive, looks unnatural
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Storage Areas

  • water is pumped out of the river and stored in temporary lakes, then pumped back when the water level in the river has dropped
  • effective
  • needs large areas of spare land
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  • barrier is raised when there is a high tide or flood
  • very expensive, new one may be needed in future
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Soft engineering

  • flood abatement
  • flood proofing
  • flood plain zoning
  • flood prediction and warning
  • washlands
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Flood abatement

  • change the land use upstream, eg by planting trees
  • slows down the flow of rainwater into rivers, eg by increasing interception
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Flood proofing

  • design new buildings or alter existing ones to reduce flood risk/effect
  • expensive to alter existing buildings
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flood plain zoning

  • different uses are allowed at different distances form the river
  • land close to the river might only be used for grazing
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flood prediction and warning

  • Environment agency monitor river level and rainfall, use info plus forecasts to predict flooding
  • issue warnings and produce flood maps
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  • parts of the floodplain that are allowed to flood
  • washlands can't bebuilt on, usually used for nature reserves or sports pitches
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