4.8 Flood Risk And Management

Question 1

Why is river flood risk increasing?

Answer 1

• more storms are happening possibly because of global climate change.
• more extreme storms so more intense rainfall leads to more flooding.
• more periods of wet weather so saturated soils so flooding more likely.
• more pressure to expand urbanised areas, more impermeable surfaces.
• removing vegetation and permeable surfaces.
• lots of development on floodplains.
• more people in danger of flooding by living on flood plains.

Question 2

Compare how soft and hard engineering schemes work.

Answer 2

Hard - man-made structures built to control the flow of the flow of rivers and reduce flooding.

Soft - schemes set up using knowledge of a river and its processes to reduce the effects of flooding.

Question 3

Explain what each hard and soft engineering schemes is, how they work and the pros/cons.

Answer 3

Hard -

• flood walls, high walls along river, increase river capacity. Fairly cheap. Increase flood risk downstream. Useful in city centres where space is limited.
• levees, like flood walls but further away from river so more capacity, up to £1m depending on material used. Increase flooding downstream. People can live near river without fear of flooding.
• dredging & flood relief channel. Removing sediment from river bed/creating a second channel. Dredging is around £50,000 and FRC can cost £14-30m depending on length. Dredging is cheap to maintain. Protects built up areas.

Soft -

• floodplain retention, lowered and vegetation planted. Costs £1.2m for 2km stretch. More water can be stored and flooding reduced.
• river channel restoration, meanders rebuilt. Costs £1.2m for 2km stretch. Improved ecology and more aesthetically pleasing.
• afforestation, planting trees in upper course so less run-off. Trees are quite expensive and saplings take a long time to grow. Natural way of reducing floods, more aesthetically pleasing, more wildlife, low maintenance.