Hard engineering

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Flood management strategies- Hard engineering

  • banks can be modified to enable the river to carry a larger volume, this can include raised banks.
  • The removal of large boulders from the bed reduces roughness therefore increasing velocity
  • Dams and weirs can be built to regulate water flow.
  • Diversion channels can be constructed to dvert the river away from floodplains,
  • Dredging can be used to deepen channels
  • the height of the floodplain can be increased
  • retention basin and lakes can be constructed to take water at times of high discharge.
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Case study: Hard engineering- Three Gorges Dam, Ch

The Three Gorges dam in China is the largest hard engineering project ever undertaken on a river. It is located on the Yangtze River in China – this river has a long history of flooding. The dam will be used to generate electricity from hydroelectric power for central and eastern China. The includes the city of Shanghai which has a population of more than 13 million people. The dam will also reduce the flood risk for 15 million people and improve navigation along the river. A huge reservoir, some 660km long and 1km wide, has been created behind the dam. The dam itself, completed in 2006 is 2.3km long and more than 100m high. According to official figures it cost some where in the region of £25 billion.

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Case study: Hard engineering- Three Gorges Dam, Ch

Social

Many cultural monuments have been lost as a result of the flooding – including the Zhang Fei temple.

Environmental

There is an increased risk of landslides in the immediate area around the reservoir and many species, such as white flag dolphin, will have their habitats disrupted

Between 1998 and 2004 the amount of sediment transported by the river below the dam fell by over 50%, resulting in increased rates of erosion downstream – sediment will accumulate behind the dam and this will require dredging Economic The creation of the reservoir has forced the resettlement of 1.2 million people from several cities, 11 district centres and over 100 villages to newly built settlements. Afforestation is needed on the slopes in the drainage basin to reduce the amount of sediment washed into the river and the reservoir behind the dam.

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