GCSE Geography | River Management: Soft Engineering (River Landscapes 11)

Many rivers are protected by soft engineering - this is using strategies that work with nature. They are cheaper than hard engineering solutions, look more attractive, but are usually less effective at reducing the risk of flooding.

Flood plain zoning

This is where land is used to minimise flood impact by categorising land into flood risk zones and issuing flood risk maps, which are then used to guide planning decisions regarding new development applications. For example, land closer to the river might be used for amenity land, such as playing fields, whereas land further away would be used for more permanent structures, such as housing development. This means that the land with the lowest economic value has the highest flood risk, but if flooding does occur there, the impact will be low.

Advantages:

• Stops development on flood plains so there is less land covered in impermeable surface, which increase run-off
• Cheap as the only costs are administrative (e.g. drawing up the specific zones)
• Protects habitats such as water meadows that may have been destroyed - these can then be used for grazing so are still economically valuable
• Development cannot take place on the flood plain so urban green spaces are protected

Disadvantages:

• This approach is too late in many urban areas where development has already taken place on flood plains
• Homeowners living on flood plains might find it hard to get planning permission for extensions or re-builds
• There is already a massive housing shortage in the UK - this is made worse by zoning areas as 'no development'
• Other green spaces might be developed on instead, destroying habitats

Flood warnings

The Environment Agency monitors river levels continually, and uses weather data from the UK Meteorological Office to check for the risk of flooding - this means that it can provide up-to-date flood alert information. The Environment Agency has a flood map website, and provides a three-day flood forecast and personalised warnings for different locations.

Once a river has been identified as being at risk of flooding warnings will be given out and action plans can be implemented. Flood action plans are likely to involve other groups, such as emergency services, the armed forces (who often help evacuate or rescue people) and voluntary organisations, such as the Royal National Lifeboat Institution (RNLI).

Flood warning information is publicised online through news and weather websites and social media channels, as well as on TV weather forecasts. Occasionally sirens and loudhailers may be used to ensure that everyone knows a flood event is coming.

Advantages:

• Cheap as it is done mainly via internet-based communication
• Early warnings mean that people can protect their valuables and evacuate if needed
• Makes people feel safe without the need for expensive hard engineering strategies

Disadvantages:

• Totally dependent on people listening to warnings and then taking action - many people ignore them!
• Not everyone has access to, or uses, the media or the internet
• It doesn't actually reduce the risk of flooding - so there will still be a long clean up process, and people still may have to move to temporary housing
• Areas with frequent flood warnings will have high home insurance premiums, and may be hard to sell in the future

Afforestation

Planting trees reduces the risk of flooding by leaf interception and root uptake, meaning that less water reaches the ground, and the water that does reach the ground is absorbed by the roots of trees and plants, so there is less surface run-off. Afforestation projects are also good for wildlife habitats.

Advantages:

• Interception and root uptake reduce surface run-off
• Absorbs carbon dioxide and other particulates, so air quality is improved
• Increases biodiversity through new habitats

Disadvantages:

• Can change the natural landscape - for example, replacing wildflower meadows with artificial woodland, which will impact biodiversity
• Loss of grazing land - impact on farming
  

River restoration

River restoration involves removing hard engineering strategies and restoring the river channel back to its natural state, for example closing off underground drains that the channel had been re-routed through. This can involve lowering floodplains to create natural water storage areas, and usually also involves afforestation projects and planting of wild flower meadows which absorb water and reduce run-off.

Advantages:

• Increased biodiversity through new wetland habitats
• Increased water storage reduces the risk of flooding downstream
• Improves the look of the area - ugly hard engineering methods replaced with nature

Disadvantages:

• Potential impact on agricultural land close to the river
• Can be expensive - particularly removing the old hard engineering strategies
• Much less effective than other strategies