Two reports highlighting the growing evidence for natural solutions and upstream thinking

Flooding alleviated by targeted tree planting and river restoration

A study by an international team of scientists, led by the Universities of Birmingham and Southampton, has shown that strategic planting of trees on floodplains could reduce the height of flooding in towns downstream by up to 20 per cent, according to research published in the journal Earth Surface Processes and Landforms.  Researchers studied a whole river catchment in the New Forest over an area of 100 square kilometres, upstream of the town of Brockenhurst. They wanted to understand how tree planting, river restoration and logjams might affect the ‘peak height’ of a flood in a downstream urban location. The research was funded by the Environment Agency who is interested in the potential for river restoration techniques to be incorporated into wider flood risk management programmes. Using a digital terrain model of the landscape and a hydrological model simulation the scientists found that planting trees on the floodplain and increasing the number of logjams, across 10-15 per cent of the total river length could reduce the peak height of a potential flood in the town by 6 per cent once the trees had grown for 25 years. They also found that for more extensive floodplain forest and river restoration, for example in 20 – 25 per cent of the total river length resulted in a reduction in flood peak height of up to 20 per cent. As the trees age and the forests become more mature and complex up to 100 years post planting there are larger reductions in flood peak height. Dr Simon Dixon, from the University of Birmingham’s Institute of Forest Research (BIFoR), lead author of the study, said: “As our research shows, targeted tree planting and restoration can contribute to reducing flood risk. We believe that tree planting can make a big contribution to reducing flood risk, and should be part of a wider flood risk management approach, including conventional flood defences. Tree planting would represent an extra element that helps to slow down the arrival of rain water to vulnerable locations.” Click here to read more.

‘Natural’ engineering offers solution against future flooding

Back-to-nature flood schemes which use the land’s natural defences to slow river flow and reduce flooding could be a cost-effective way of tackling one of the biggest problems facing the UK today.

The schemes – which include capturing flow upstream to prevent floods downstream where they are likely to have a greater impact on infrastructure and homes – have been trialled as part of a five-year research project by experts from Newcastle University in partnership with the Environment Agency.

Using Belford Burn in Northumberland as a demonstration, the team have shown that by changing and hindering the natural flow pathways within a small catchment system, it is possible to manage the amount of run-off from the land. This reduces the risk of flooding in low-lying areas and also cuts down on pollution by preventing phosphorous and nitrates from being washed off the land.

Published this month in the academic journal Science of the Total Environment, the findings were presented last week at the House of Commons Office of Science and Technology to inform the Government’s Environment White Paper. To read more click here.