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Removing Instream Weirs; evaluating the Benefits and Pitfalls for a Lowland Low E
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  • John Boardman,
  • Ian Foster,
  • Atish N. Vadher,
  • Ruth Copeland-Phillips,
  • Toby N. Tonkin
John Boardman
University of Oxford Environmental Change Institute

Corresponding Author:john.boardman@eci.ox.ac.uk

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Ian Foster
University of Northampton Faculty of Arts Science and Technology
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Atish N. Vadher
Loughborough University School of Science
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Ruth Copeland-Phillips
University of Northampton Faculty of Arts Science and Technology
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Toby N. Tonkin
University of Northampton Faculty of Arts Science and Technology
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Abstract

The removal of dams, weirs or barriers to river flow, is frequently a contentious issue. This is because of the competing demands of flood protection and the ecological, social, economic and cultural health of the river. Many of the barriers are old or obsolete and there is an international drive to create ‘free-flowing rivers’ with no or fewer barriers, thereby increasing longitudinal connectivity. This has been most noticeable in North America and continental Europe, and less apparent in the UK. We explore the issues around weir removal with a case study of a lowland southern English river, the River Rother, West Sussex, in a predominantly agricultural catchment where weirs have been constructed for a variety of purposes over the last ~1000 years. The river is dominated by inputs of sand-sized sediment with very low organic matter content that is frequently stored upstream of structures. The multiplicity of stakeholders and the strong interests of the fishing and farming communities render decision-making about structure removal or modification to improve fish passage difficult. There is also the demand for potable water abstraction by the local water company which would be affected by dam removal and the potential release of the fine (mostly < 2mm dia.) sediments stored immediately upstream of the weirs. This paper subsequently explores selected issues around weir removal under the requirement of the European Water Framework Directive to achieve Good Ecological Status and explores guidance on best practice; including the decision which weirs to remove and in which order.