Management of flooding (WJEC Eduqas GCSE Geography B): Revision Note

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The notes on this page cover part 2.2. 2 of the WJEC Eduqas GCSE B Geography.

2.2.2 Why do rivers flood and what are the consequences of flooding?

• The costs and benefits of soft and hard engineering flood management options.

• Management options to include dam construction, river engineering, afforestation, managed flooding and land use zoning for flood plains.

• The impact of river management on hydrographs.

River management – hard engineering

• The key cause of flooding is the amount and duration of precipitation; this cannot be altered

• There are a number of methods of managing floods and reducing their severity and/or impact

• The two main categories of flood management are hard and soft engineering

  • Hard engineering involves building structures or changing the river channel

• Examples of hard engineering include:

  • Dam construction

  • Channel straightening

  • Embankments and levées

  • Flood relief channels

Dams and reservoirs

• Construction of a dam across the river valley to form a barrier with a reservoir behind

Embankments and levées

• Construction of banks at the sides of the river

Channel straightening

• Removes the meanders from the river, creating a straight channel

Flood walls

Flood relief channels

Dredging

• This increases the capacity of the river, reducing the flood risk

River management - soft engineering

• Soft engineering works with natural processes of the river and surrounding environment

  • Soft engineering is increasingly popular because it has less impact on the environment

  • Soft engineering is an example of mitigation where schemes aim to minimise damage rather than trying to prevent flooding 

• Examples of soft engineering include:

  • River restoration

  • Afforestation

  • Land use zoning

River restoration

Afforestation

Land use zoning

The impact of flood management on hydrographs

• The aim of flood management is to reduce the impact of floods or to prevent water reaching areas of high value

• Both hard and soft engineering impact hydrographs by altering their shape

• Some hard engineering strategies, such as channel straightening, lead to shorter lag times and higher peak discharge because they speed up water flow

• Dams store large volumes of water, which reduces the discharge downstream and leads to a longer lag time

• Other hard engineering methods such as embankments, levees and dredging can increase the peak discharge downstream because they prevent the water from leaving the channel

• Soft engineering such as afforestation and river restoration leads to longer lag times and lower peak discharge