Nature can play a major role in improving the nation’s resilience to flooding and coastal erosion, updated research from the Environment Agency appears to underline.
The EA has published a new Working with Natural Processes Evidence Directory, updating the internationally recognised product first released in 2017.
Informed by significant scientific research including more than 700 papers, the directory summarises the latest evidence for 17 natural flood management (NFM) measures relating to river and floodplain, woodland, run-off, and coast and estuary management.
NFM protects, restores and emulates the natural functions of rivers, floodplains, catchments and the coast to reduce flooding and coastal erosion. It takes many different forms and can be implemented in urban and rural areas, on rivers, and on estuaries and coasts.
The directory shows the wide variety in the benefits of the different measures.
Among the findings, catchment woodland is shown not only to help reduce flood risk but also to provide benefits for soil, biodiversity and water quality, alongside access to nature.
The review showed catchment woodland can reduce the height of flood water, with the greatest reductions during smaller events. One study in Cumbria suggested the flow of flood water was slowed by 14-50% in woodland compared to pasture.
The latest science also showcases the significant wider benefits of saltmarsh and mudflat restoration, including their ability to store large amounts of carbon, helping to mitigate climate change. They can also filter sediments and nutrients, improving water quality.
Managed realignment at Steart Marshes in Somerset created 250 hectares of saltmarsh. A recent study showed the marsh was storing 36.6 tonnes of carbon per hectare per year following restoration, a number which compares favourably with woodland.
For the first time, the updated directory includes emerging evidence for three new measures, highlighting the potential flood risk reduction and wider benefits of coastal reefs, submerged aquatic vegetation, and beavers. There is still more to learn about these measures, including understanding what the best depth for oysters to grow and develop while also effectively reducing wave energy is.
The new Working with Natural Processes directory demonstrates that the evidence for NFM has grown significantly, building confidence in the flood risk reduction and wider benefits.
The directory provides a new evidence baseline for NFM, helping to inform future investment decisions and support the selection of measures on the ground.
Julie Foley, Environment Agency Director of Flood Risk Strategy and National Adaptation, said:
“With climate change increasing the threats of flooding and coastal erosion, we must work together with nature to boost resilience across the country.
“That’s why the Environment Agency is mainstreaming the use of natural flood management alongside the use of traditional engineered defences.
“Our £25 million Natural Flood Management Programme was shaped by the Working with Natural Processes Evidence Directory. Through this fund we are testing our approaches to future investment and the delivery of natural flood management.”
New evidence also demonstrates the benefits of combining multiple NFM measures. The five-year Littlestock Brook trial on the River Evenlode in Oxfordshire tested several measures at the same time, including putting in woody dams, creating 230m of new water courses, and planting 14.4 hectares of new woodland. Results from the trial show reductions in the height of flood waters of up to 55.2% across all the storms analysed.
Research suggests the Evenlode project will help remove 8,199 tonnes net of carbon dioxide to the atmosphere, attributed to creating the woodland and agroforestry.
The Salmons Brook NFM project in Enfield, north London, combined planting 200 hectares of woodland with reducing the width of the channel by 75% and installing 46 bunds in a rural catchment. Modelling found that, during a once-in-a-25-year storm, the combination could reduce flood flows by half and peak water levels by 10-30cm in the urban areas downstream, with the effectiveness expected to increase with the woodland’s maturity.
Kathryn Brown, The Wildlife Trusts Director of Climate Change and Evidence, said:
“Getting the best evidence to support our collective efforts to build resilience is critically important.
“I’m delighted to see the latest science on natural flood management coming together in one place through the Environment Agency’s Evidence Directory, with a focus on co-benefits – and to see new recognition of the role beavers can play in natural flood management.
“This well-used directory has been pivotal in supporting NFM work across the country, including through The Wildlife Trusts.”
The findings of the original report are widely referenced in the International Guidelines on Natural and Nature-Based Features for Flood Risk Management, an international guide produced by the US Army Corps of Engineers.
Publishing the new Working with Natural Processes evidence directory meets the Environment Agency’s commitment in its Flood and Coastal Erosion Risk Management Strategy Roadmap to update the report by 2026.
