The dam traps water, which builds up behind it, forming a reservoir. Water can be released in a controlled way.
can be used to generate electricity
can attract tourists
Habitats are flooded often leading to rotting vegetation, releasing methane which is a greenhouse gas.
Settlements are lost leading to the displacement of people.
Clywedog reservoir was built in the 1960s to help prevent the flooding of the River Severn
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River straightening and dredging
hard engineering strategy
Straightening the river speeds up the water so high volumes of water can pass through an area quickly. Dredging makes the river deeper so it can hold more water.
reduces flood risk in built-up areas
dredging needs to be done frequently
increases flood risk downstream
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Embankments
hard engineering strategy
Raising the banks of a river means that it can hold more water.
cheap with a one-off cost
looks unnatural (concrete/stone walls)
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Flood relief channels
hard engineering strategy
The floodwater flows into the relief channel and is taken either to an area where it can be absorbed, or re-enters the river further down its course.
Removes excess water from the river channel to reduce flooding.
Expensive to build.
If water levels continue to rise, the relief channel may also flood.
Jubilee River is an 11km long flood relief channel built to reduce the flood risk on the Thames
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Afforestation
soft engineering strategy
planting trees
trees obstruct the flow of wter and slow down its transfer to the river channel
water is taken up by trees and evaporated from leaves and branches
relatively cheap
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Wetlands and flood storage areas
soft engineering strategy
wetlands are deliberately allowed to flood, forming storage areas
reduces risk of flooding downstream
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Floodplain zoning
soft engineering strategy
restricts diffferent land uses to certain zones on the floodplain
More expensive buildings and land uses are further away from the river, so have a reduced flood risk.
Less damage is caused, leading to fewer insurance claims.
Not always possible to change existing land uses.
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River restoration
soft engineering strategy
when a river's course has been changed artificially, it can be restored to its original course
uses the natural processes and features of a river, e.g. meanders and wetlands to slow down flow and reduce the likelihood of flooding downstream
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Flood warnings and preparation
The environmental agency monitors rivers and issues warnings via newspapers, TV, radio and the internet when they are likely to flood so people can prepare.
People have time to protect their properties, eg with sandbags.
Many possessions can be saved, resulting in fewer insurance claims.
Some people may not be able to access the warnings.
Flash floods may happen too quickly for a warning to be effective.
They do not stop land from flooding - they just warn people that a flood is likely.
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