Hard v Soft Engineering You decide???

Hard v Soft Building a structure (often concrete and steel) to control the river. Essentially, dealing with the rising water Using natural methods which may involve allowing the river to flood Or stopping the river from flooding in the first place so never having to deal with rising water Often more sustainable

Build a Dam Aim is to reduce discharge downstream by holding water behind the dam wall E.g 3-Gorges – China Aswan Dam - Egypt

Dam or No Dam? Positives and Negatives? Creates a lake that may provide income from tourism or fishing (Lake Mead behind Hoover Dam) Is very effective at reducing flood risk downstream (3-Gorges reduced flood risk on the lower Yangtze from 1 in 10 years to 1 in 100 years) Can be combined with turbines to create HEP (3-Gorges Dam China) Produces jobs in construction and maintenance

Dam or No Dam? Positives and Negatives? Very expensive (3-Gorges Dam over $26 BN) Floods a large area behind the dam. This may result in people beind re-located (3-Gorges) or ancient sites being lost (Aswan Dam) Reduced flow downstream may cause silting and increase flood risk long term The reservoirs begin to silt up so the capacity is reduced greatly over time Stopping the flooding downstream can devastate farmers who reply on floods to fertilize their fields (Nile Delta)

River Engineering Involves physically altering the course, or size of the channel Reducing length and speeding up flow by cutting off meanders to take water away form the area in danger Canalisation – concrete banks to speed flow and reduce erosion (Seine Near Paris)

Cheaper than building a dam May cause flooding elsewhere

Levees or Embankments Levees (Raised Banks)

SOFT

Flood Warnings – Environment Agency

Preperation

Evacuation plan Stock up with supplies Stocking sandbags Move goods upstairs Tune into local TV/Radio Choose tiled floors instead of carpets

Afforestation Planting trees in the basin… Increased the amount of evapotranspiration Increased infiltration Increased interception All of which result in less water making it to the river Binds soil to reduce eroison

Flood Zoning Allows the river to flood the least valuable land by the river Involves long term planning. Houses (most expensive) located high up The roads and arable farm land Then cattle by the river (which can be moved) One example is Bloomington USA Q. Explain why this method is ‘sustainable’?

Do Nothing Nature is too powerful, we should let it flood. Besides, flooding is good for fertile land (Nile Delta)