New evidence on benefits of natural flood management

The Environment Agency has published a new Working with Natural Processes Evidence Directory, updating the first release 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.

Photo credit: Petr Ganaj

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.