Hard engineering strategies

Flooding can cause damage to homes, businesses, infrastructure and communications.

involves building artificial structures which try to control rivers. They tend to be more expensive. Each hard engineering strategy has its advantages and disadvantages.

Dams and reservoirs

The dam traps water, which builds up behind it, forming a reservoir. Water can be released in a controlled way.

Advantages

Can be used to produce electricity by passing the water through a turbine within the dam.
Reservoirs can attract tourists.

Disadvantages

Very expensive.
Dams trap sediment which means the reservoir can hold less water.
Habitats are flooded often leading to rotting vegetation. This releases methane which is a .
Settlements are lost leading to the displacement of people. In developing countries locals are not always consulted and have little say in where they are relocated.

River straightening and dredging

A dredger working to deepen the channel of the River Maas, Port of Rotterdam, Netherlands — Figure caption,
A river dredger in the Netherlands

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.

Advantages

More water can be held in the channel.
It can be used to reduce flood risk in built-up areas.

Disadvantages

Dredging needs to be done frequently.
Speeding up the river increases flood risk downstream.

Embankments

Figure caption,
The Moskva River embankment, Moscow

Raising the banks of a river means that it can hold more water.

Advantages

Cheap with a one-off cost
Allows for flood water to be contained within the river.

Disadvantages

Looks unnatural.
Water speeds up and can increase flood risk downstream.

Flood relief channels

Figure caption,
The Morganza spillway on the Mississippi river is a flood relief channel

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.

Advantages

Removes excess water from the river channel to reduce flooding.

Disadvantages

Expensive to build.
If water levels continue to rise, the relief channel may also flood.

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River management - AQAHard engineering strategies