How might climate change affect river flows across the Thames Basin?: an area-wide analysis using the UKCP09 Regional Climate Model ensemble

Bell, V.A.; Kay, A.L.; Cole, S.J.; Jones, R.G.; Moore, R.J.; Reynard, N.S.. 2012 How might climate change affect river flows across the Thames Basin?: an area-wide analysis using the UKCP09 Regional Climate Model ensemble. Journal of Hydrology, 442-443. 89-104.

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The Thames Basin drains an area of over 10,000km2 through London to the North Sea. It encompasses both rural and heavily urbanised areas overlying a spatially-varied and complex geology. Historically, the lower Thames has proved resilient to climate variability, and careful river management in recent years has helped protect the region from flooding. However, recent climate projections for the region indicate that over the next century winter rainfall might increase by 10-15%, potentially leading to higher flows than the Thames can accommodate. This study uses a distributed hydrological model, the Grid-to-Grid (G2G), to assess future changes in peak river flows for a range of catchments across the Thames Basin. The G2G model has used as input an ensemble from the UK Climate Projections (UKCP09) Regional Climate Model (RCM), under the A1B emissions scenario, to analyse changes in flood frequency between two 30-year time-slices (Oct 1960-Sep 1990 and Oct 2069-Sep 2099). The RCM ensemble uses a perturbed-parameter approach to address uncertainty in climate projections. Results indicate considerable spatial variation in projected changes in peak flows. Towards the downstream end of the fluvial Thames, the average estimated change in modelled 20-year return period flood peaks by the 2080s is 36% with a range of -11% to +68%, which is broadly in line with recent government guidance for the Thames Basin. A key question that arises is whether these estimated changes fall within the range of natural variability and would therefore be indistinguishable from the effects of typical weather patterns in the current climate. Comparison of the modelled changes in flood frequency with an RCM-based estimate of current natural variability shows that, whilst for some rivers (or parts of rivers) there are few changes outside the range of current natural variability, for other rivers there are more changes outside of this range. The latter locations could be considered as sites where further monitoring/modelling may provide early warning of statistically significant changes in observed flows, due to climate change.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Water > WA Topic 1 - Variability and Change in Water Systems > WA - 1.3 - Model, attribute and predict impacts of climate and land cover change on hydrological and freshwater systems
CEH Topics & Objectives 2009 - 2012 > Water
UKCEH and CEH Sections/Science Areas: Boorman (to September 2014)
ISSN: 0022-1694
Additional Information. Not used in RCUK Gateway to Research.: NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Hydrology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Hydrology, 442-443. 89-104. 10.1016/j.jhydrol.2012.04.001
Additional Keywords: rainfall-runoff, flood frequency, climate change, RCM ensemble, UK Climate Projections
NORA Subject Terms: Hydrology
Date made live: 24 Apr 2012 08:49 +0 (UTC)

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