Hard engineering

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

Hard engineering 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

A man-made reservoir
A man-made reservoir

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 greenhouse gas.
  • 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
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

The Moskva River embankment, Moscow
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

The Morganza spillway on the Mississippi river is a flood relief channel
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.