Planting productive woodland in specific areas of the UK could play a role in reducing the risk of flooding, according to a landmark report. The study by Forest Research and trade body Confor highlights the role productive woodland can play in lessening the likelihood of floods.
In managing flood risks, The Role of Productive Woodlands in Water Management report notes, “Forests and woodlands have long been associated with an ability to reduce flood flows compared to other land uses in various ways”. The report highlights four main ways that woodland can help:
- the greater water use of trees reduces the volume of flood water at source;
- the higher infiltration rates of woodland soils reduces rapid surface runoff and flood generation;
- the greater hydraulic roughness exerted by trees, shrubs and large woody debris (LWD) along streamsides and within floodplains acts as a drag on flood waters, slowing down flood flows and enhancing flood storage; and
- the ability of trees to protect the soil from erosion and interrupt the delivery of sediment via runoff to watercourses helps to maintain the capacity of river channels to convey flood waters downstream and reduces the need for dredging.
It also highlights how productive woodland can deliver specific benefits, including:
- Water use tends to be highest for productive conifer woodland
- Drier soils under productive woodland may make them better able to receive and store rainfall
- In general, larger areas of planting offer greater water benefits – and productive woodlands tend to be on a larger scale because they are more economical and attractive to landowners.
- Reducing pollutants in the water
The study also found soil infiltration rates to be up to 60 times higher within woodland shelter belts compared to grazed pasture.
The report concludes, “There is a strong case for further investment in well-targeted woodland creation to help meet a wide range of environmental and social goals“, including the Floods Directive, Water Framework Directive, Biodiversity 2020, greenhouse gas reduction, climate change adaptation and rural economic growth.
Dr Tom Nisbet, of Forest Research, the author of the report, said: “There is growing recognition that we need to develop a more sustainable approach to flood management involving a greater use of natural processes. Productive woodlands can be very good at reducing and slowing down flood flows, as well as helping to reduce the amount of soil and other pollutants entering our rivers.”
In response to the report, Forestry minister Dan Rogerson said: “The report is a timely reminder to us all that our woodlands are far more than just something attractive to look at.”
He also went on to add “These national assets generate considerable economic and environmental benefits through their unique ability to deliver a wide range of ecosystem services, such as timber, woodfuel, carbon storage, enhanced water quality, water and soil regulation and, of course, valuable habitats for wildlife.”
Since April 2012, the English Woodland Grant Scheme has included an enhanced grant rate to encourage woodland planting where it could help reduce flood risk for affected communities, including in downstream towns and cities, and improve the freshwater environment. This had delivered around 1,800 ha of new woodland across the country by December 2013.
Forest Research has developed what it calls opportunity mapping to identify, map and target areas where productive woodland could have the most positive impact.
The report, titled “Role of Productive Woodlands in Water Management”, is available for download from the Confor website. Find out more about Flood Risk Assessment by visiting our FRA page.