River management
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Hard engineering
- Hard engineering strategies involve the use of technology in order to control rivers
- A dam is a barrier across the river that prevents the flow of the river, causing water to fill the area behind it and create a reservoir, which can be released or held depending on circumstances such as current and expected rainfall
- Straightening meanders involve making the river follow a shorter and straighter route, causing it to flow faster so there is less change of it flooding
- Embankments are raised banks along a river, effectively making them deeper so they can hold more water before flooding
- Flood walls are build around settlements and important areas that stop the movement of water
- Storage areas are areas of land where water is pumped from the river to make a temporary lake before being pumped back in after river levels fall
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Soft engineering
- Soft engineering strategies seek to work with the natural river processes to reduce the effects of flooding
- Flood warnings and preparation involves identifying places at risk and issues warnings, giving people time to prepare by moving possessions upstairs; turning off gas, water and electricity; gathering important papers and taking basic precautions against flooding, or even evacuating
- Floodplain zoning involves assessing the flood risk across the floodplain and determining land use accordingly, so as the risk falls, the quality & value of the land rises, in the following order: pastures for grazing, playing fields, roads and car parks, industry and housing
- Washlands involves allowing part of the floodplain to be flooded, and are normally reserved for sports pitches
- Afforestation involves planting trees to increase interception and delay flooding
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Monitoring
- Doing nothing allows natural events to happen, even if this involves the risk of flooding and is a necessary approach in some poorer areas of the world
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Cost-benefit analysis
Strategy Advantages Disadvantages Dams Highly effective Expensive
Not natural-looking
Load & waste can build up in the reservoir
People may need to move to accommodate itStraightening the river Highly effective Expensive
Not natural-lookingEmbankments Highly effective Expensive
UnsustainableStorage areas Highly effective Needs a large area of unused land Warning systems Cheap People do not always receive or heed warnings Land-use zoning Important land less likely to be flooded Large areas of land are unutilised Afforestation Natural-looking Takes up a lot of land
Cannot prevent serious flooding