Strategies to reduce river flooding

• Dams and reservoirs

  Hard/Soft: Hard

  What is it: A concrete barrier across a channel: Dam

  Artificial lake: Reservoir

  Benefits: Hydroelectricity powers 11,000 homes, 200 jobs were created, New habitats for animals

  Costs: Expensive (167 million), 58 families displaced

  Example: Kielder dam and reservoir, Northumberland
• Channel straightening

  Hard/Soft: Hard

  What is it: Meanders are removed, making the river wider, straighter, and deeper, so discharge flows away quicker

  Benefits: Improved navigation, Can create new habitats

  Costs: Expensive (10 million management plan), Damages habitats

  Example: River Valency, Bostcastle, Cornwall
• Embankments

  Hard/Soft: Hard

  What is it: Artificially raises banks, deepens channel, and increases capacity

  Benefits: Foot and cycle paths, Cheaper to put in place

  Costs: Unattractive, High maintenance costs

  Example: York floodwall
• Flood relief channels

  Hard/Soft:  Hard

  What is it: divert discharge away from risk areas using artificial meanders

  Benefits: Controlled discharge release, contains new habitats

  Costs: Expensive (8 million), Unattractive, Takes up land

  Example: River Exe, Exeter
• Flood recurrence interval

  Probability a river will flood within a given time frame.
• Hard Vs Soft engineering

  Soft: Cheaper, Better for the environment, Easier to maintain

  BUT

  Less effective
• Flood plain zoning

  Hard/Soft: Soft

  What is it: Land used in a river valley is planned carefully to reduce the effects of flooding, by prioritising placing high value land e.g. housing, furthest away

  Benefits: Less impermeable surfaces, so rainwater enters river slower. If there are no properties near the channel, there will be less damage when floods occur and more green spaces.

  Costs: Many urban areas have already built on the "at risk" zone, so it is very expensive and less effective to change this, and doesn't help the housing crisis, and may put Greenfield sites at risk of development.
• Afforestation (planting trees)

  Hard/Soft: Soft

  What is it: Planting trees, which help intercept rainfall, undertake transpiration, and store water for photosynthesis, slowing down surface run off and risk of flooding.

  Benefits: Soil erosion is reduced as trees bind the soil, preventing soil being washed into the river, reducing its capacity. Increase in natural habitats.

  Costs: Less land available for agriculture or infrastructure, trees take a long time to grow, delaying that impact.

  Example: Pickering, North Yorkshire
• River Restoration

  Hard/Soft: Soft

  What is it: Restoring a river back to natural state, after previously using hard engineering, allowing the flood plain to flood naturally downstream, and natural processes to occur, which may have been obstructed by channel straightening.

  Benefits: Restored rivers require less maintenance, being more cost effective. New habitats, so increasing biodiversity.

  Costs: Restoring a river can be very expensive (1.1 mil), May be loss of land as the river naturally meanders.

  Example: River Quaggy, Greenwich
• Why do you want to manage a drainage basin?

  • Important to the people and wildlife as provide habitats, homes, and farmland
  • If they aren't managed, increases flood risk of a river, leading to damaged properties, farmers losing crops, animals downing, businesses flooding leading to unemployment (negative multiplier effect), impacting the community
• Sustainable management


  Sustainable means it will stop flooding in the future whilst protecting the current community