Floodplains : the forgotten and abused component of the fluvial system

Heritage, G; Entwistle, NS; Bentley, S

Abstract

River restoration is strongly focussed on in-channel initiatives driven by fisheries interests and a continued
desire for river stability. This contrasts greatly with the inherently mobile nature of watercourses. What is often
overlooked is the fact that many rivers have developed floodplain units that would naturally operate as integrated
functional systems, moderating the effects of extreme floods by distributing flow energy and sediment transport
capacity through out of bank flooding. Floodplain utilisation for farming activities and landowner intransigence when
it comes to acknowledging that the floodplain is part of the river system, has resulted in floodplains being the most
degraded fluvial morphologic unit, both in terms of loss of form and function and sheer levels of spatial impact. The
degradation has been facilitated by the failure of regulatory mechanisms to adequately acknowledge floodplain form
and function. This is testament to the ‘inward looking’ thinking behind national assessment strategies. This paper
reviews the state of floodplain systems drawing on quantitative data from England and Wales to argue for greater
consideration of the floodplain in relation to river management. The database is poor and must be improved, however
it does reveal significant loss of watercourse-floodplain connectivity linked to direct flood alleviation measures and
also to altered flood frequency as a result of river downcutting following river engineering. These latter effects have
persisted along many watercourses despite the historic nature of the engineering interventions and will continue to
exacerbate the risk of flooding to downstream communities. We also present several examples of the local and wider
values of reinstating floodplain form and function, demonstrating major ecological gains, improvement to
downstream flood reduction, elevation of water quality status and reductions in overall fine sediment loss from
farmland. A re-think is required regarding our approach to managing floodplains and funding floodplain restoration,
arguing for greater recognition of the natural role of the floodplain as a resource for upstream flood management and
as an agent for overall biotic improvement in line with restoration objectives.

Citation

Heritage, G., Entwistle, N., & Bentley, S. (2016). Floodplains : the forgotten and abused component of the fluvial system. https://doi.org/10.1051/e3sconf/20160713007

• Journal Article Type: Article
• Online Publication Date: Oct 20, 2016
• Publication Date: Oct 20, 2016
• Deposit Date: Nov 17, 2016
• Publicly Available Date: Nov 17, 2016
• Journal: E3S Web of Conferences (3rd European Conference on Flood Risk Management (FLOODrisk 2016))
• Publisher: EDP Sciences
• Volume: 7
• Issue: 13007
• DOI: https://doi.org/10.1051/e3sconf/20160713007
• Publisher URL: http://dx.doi.org/10.1051/e3sconf/20160713007