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    Our World View: The role of trees in managing flood risk

    Posted 21 February 2014

    Mike Townsend

    A monthly comment from a member of staff at Harper Adams University

    Mike Townsend, Principal Advisor, Woodland Trust

    “Flooding has highlighted the importance of land use in managing flood risk. The extent to which water is held in the upper catchment and the speed with which it moves down the catchment both have an impact of the risk and severity of flooding. 

    A review of water and farming has provided evidence for the role of trees in managing water quality and flood risk. Forest Research has also undertaken research looking at the role of trees in delivering better water quality and the impacts of increased tree cover on flood risk.

    Often however, the arguments have become polarised with calls to remove sheep and reforest the hills. These arguments often fail to recognise the importance of farming, economically and culturally, to large parts of the country. They start from the false assumption that flooding is an inevitable consequence of sheep farming.

    Lessons from Pontbren

    The Pontbren farmers in mid-Wales show not only that flooding is not an inevitable consequence, but that sustainable management of sheep can contribute to flood mitigation.

    During the last 10 or so years, the group of farmers managing more than 1000 ha of the Pontbren catchment have restored hedgerows, planted new hedges and shelter belts and invested in the management of their woodland. This has provided vital shelter to allow a switch to outdoor lambing and less need for housing. It has also provided the opportunity to exclude sheep from steep areas and from wet areas prone to foot rot and liver fluke.

    New hedges and shelter belts, particularly those across the slope, have increased water infiltration into the soil and reduced erosion and the loss of valuable topsoil and nutrients. Planting tree belts across the slopes led to increased water infiltration into the soil more than 60 times that of neighbouring pasture.  When this effect was modelled across the catchment the result was a potential reduction in peak stream flows of as much as 40%.

    This farmer led initiative shows that an intimate knowledge of the land is vital in designing tree belts. The farmers knew where shelter was needed, where runoff was a problem and areas prone to erosion. They have managed simultaneously to improve the resilience and sustainability of their farms whilst delivering improved water quality and flood mitigation.”

    Jim Waterson, Crop and Environment Sciences, Harper Adams University

    Thoughtful use of woodland

    “At the beginning of the process, the farms had just 1.5% tree cover; now 5% is trees. This has been achieved without loss of productivity. Not a wholesale transformation of the uplands, but a sensible change in practice with trees integrated into the farming.

    There are undoubtedly opportunities in the uplands for more extensive areas of new woodland, but the answer is not removing farming. In Wales, 80% of farmland is classed as upland.  These are generally small family farms central to the survival of communities and an essential element of Welsh culture and language.

    Strategically located woodland can be important in reducing flood risk, improving water quality, contributing to biodiversity conservation, storing carbon and helping support sustainable farming practices. It is these multiple benefits which make it such a compelling option. Thoughtfully integrated into farming systems trees can have direct benefits to the farm whilst also delivering flood mitigation.”

    A special thanks to Mike Townsend for his contribution to this piece.

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