The impact of upland land management on flooding: results from an improved pasture hillslope

Authors

  • Miles R. Marshall,

    Corresponding author
    1. Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
    2. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
    • Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK.
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  • Oliver J. Francis,

    1. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
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  • Zoe L. Frogbrook,

    1. Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
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  • Bethanna M. Jackson,

    1. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
    2. School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
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  • Neil McIntyre,

    1. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
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  • Brian Reynolds,

    1. Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
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  • Imogen Solloway,

    1. Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
    2. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
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  • Howard S. Wheater,

    1. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
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  • Joanne Chell

    1. Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
    2. Atkins, Woodcote Grove, Ashley Road, Epsom, Surrey, KT18 5BW
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Abstract

In response to growing concern about impacts of upland agricultural land management on flood risk, an intensely instrumented experimental catchment has been established at Pontbren, a sheep-farmed headwater catchment of the River Severn, UK. Primary aims are to develop understanding of the processes governing flood generation and the associated impacts of land management practices, and to bridge the gap between process understanding and ability to predict effects on downstream flooding. To achieve this, the experiment is designed to operate at plot (∼100 m2), hillslope (∼0·1 km2) and small catchment scale (∼10 km2). Hillslope-scale data, from an under-drained, agriculturally ‘improved’ pasture, show that drain flow is a dominant runoff process. However, depending on antecedent moisture conditions, overland flow may exceed drain flow rates and can be an important contributor to peak flow runoff at the hillslope-scale. Flow, soil tension data and tracer tests confirm the importance of macropores and presence of perched water tables under ‘normal’ wet conditions. Comparisons of pasture runoff with that from within a 10 year-old tree shelterbelt show significantly reduced overland flow due to the presence of trees and/or absence of sheep. Comparisons of soil hydraulic properties show significant increases in hydraulic conductivity and saturated moisture content of soil under trees compared to adjacent improved pasture. Copyright © 2008 John Wiley & Sons, Ltd.

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