Hard and Soft Engineering

• What is hard engineering?

  • Involves builiding structures to control water flow and reduce flooding
  • dams and reservoirs, straightening, embankments, flood relief channels
• How do dams and reservoirs reduce flooding?

  • A large wall is built across the upper course of the river, the land behind the dam is then flooded to form a reservoir which can hold excess water
• What are the advantages and disadvantages of dams and reservoirs

  • Ad - Can hold a lot of excess water, greatly reduces risk of flooding, can generate electricity when water flows through (hydroelectric)
  • Dis - Areas of land are flooded which damages habitats and displaces people, costly, sediment is deposited in the reservoir which impacts the sediment deposit in the lower course for floodplains (decreases soil fertility)
• What is channel straightening?

  • Cuts out meanders to change the course of the river
  • (Advantage) - reduces flooding by having water flow straight which makes it flow quicker and more direct
• Disadvantages of channel straightening

  • Faster flow of water increases risk of flooding downstream
  • Faster flow of water increases erosion, meaning there is chances of meandering in the future
• What are embankments?


  • Building up the banks of the river
  • You could make levees or walls
  • (Advantages) - Protects buildings from flooding, increases capacity of river meaning less flooding
• Disadvantages of embankments 


  • Expensive
  • If the wall fails, the surrounding area will be instantly flooded
• What are flood relief channels?

  • Artificial channels to divert water around important locations
  • Advantages - River discharge is reduced - less flooding possibility
• What are disadvantages of flood relief channels?

  • Increased risk of flooding when the two rivers join back up together
• What is soft engineering?

  • work with the natural processes along the river to reduce the risk of flooding
• What are flood alerts and preperation?

  • The enviroment angency warns people about floods through Tv, radio and internet, newspapers
  • Advantages - The IMPACT of flooding is reduced as people have more time to prepare and evacuate
• What are disadvantages 


  • Warnings do not stop a flood event. Not all people will be aware of flood warnings.
• What is floodplain zoning?

  • Floodplain zoning involves putting building restrictions on floodplains at risk of flooding.
  • Advantages - Buildings are not constructed in areas at risk of flooding. Impermeable surfaces are not constructed on the floodplain, so the risk of flooding is not increased
• Disadvantages of floodplain zoning

  • Can restrict urban growth
  • Dosen't reduce risk of flooding
• How does planting trees reduce the risk of flooding?

  • Increases interception which reduces flooding
  • Advantages - Discharge in the river is reduced. The trees also reduce the risk of soil erosion, which can reduce the capacity of the river channel to carry water
• What are the disadvantages of tree planting?

  • Restricts what the land can be used for
• What is river restoration?

  • River restoration involves returning a river to its natural state. This can involve removing man-made levees or removing river straightening
  • Advantages - Biodiversity is maintained, little maintenance is required, discharge reduces
• Disadvantages of river restoration

  • Flood risks can increase if nothing is done along a river