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Flooding can cause damage to homes, businesses, infrastructure and communications. The impact of flooding can be reduced in a variety of ways.

Hard engineering

Hard engineering involves building artificial structures which try to control rivers. They tend to be more expensive, and have a significant impact on the natural environment. Each hard engineering strategy has its advantages and disadvantages.

Dams and reservoirs

A 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 provide a water supply for nearby towns and cities.
• Reservoirs can attract tourists.

Disadvantages

• Very expensive.
• Spoil the look of the natural environment.
• 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 greenhouse gas.
• Settlements are lost leading to the displacement of people. In developing countries locals are not always consulted and can have little say in where they are relocated.

River straightening and dredging

Straightening the river speeds up the water so high volumes 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

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

Advantages

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

Disadvantages

• Look unnatural.
• Water speeds up and can increase flood risk downstream.

Flood relief channels

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

• Remove 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.