Engineering strategies

• Hard engineering


  Man made structure to control flow and reduce flooding
• soft engineering


  schemes using knowledge of river and its processes to reduce effects
• h- dams and reservoirs


  -barriers built across rivers

  —reservoir (artificial lake) forms behind

  +reservoirs store water, control flow, and prevent floods downstream

  +can generate hydroelectric power

  -expensive

  —reservoir can flood existing settlements

  -material deposited so farmland less fertile
• h- channel straightening


  -meanders removed by building artificial channels

  + water leaves area faster

  -flooding downstream, fast moving water may cause erosion
• h- embankments


  -raised walls built along river banks

  +river holds more water

  -expensive and risk of severe flooding if break or rise above
• h- flood relief channels


  -divert water around built up areas or if level gets too high

  +gates control water

  -increased discharge where channel joins river, could cause flooding
• s- flood warnings and preparation


  environment agency issues flood warnings through media allowing

  .buildings to be modified to minimise damge

  .prepare sandbags and flood boards

  +time to move possessions/ evacuate

  -don't prevent floods, some cant access warnings

  -can be expensive

  -gives false sense of security
• s- flood plain zoning


  restrictions prevent building on certain parts of plain

  + impact reduced, less to damage

  -expansion of urban areas limited

  -cant help existing areas
• s- planting trees


  increases interception of water and lag time

  +discharge and flood risk decrease

  + reduces soil erosion and provides habitats

  -less land for farming
• s- river restoration


  making river more natural so plain can flood naturally

  +discharge reduced, less risk of flooding downstream

  + little maintenance needed and better habitats

  -local flood risk can increase