Preprints
https://doi.org/10.5194/hess-2021-321
https://doi.org/10.5194/hess-2021-321

  29 Jun 2021

29 Jun 2021

Review status: a revised version of this preprint is currently under review for the journal HESS.

A large-sample investigation into uncertain climate change impacts on high flows across Great Britain

Rosanna Lane1,a, Gemma Coxon1,2, Jim Freer1,2,3, Jan Seibert4, and Thorsten Wagener2,5,6 Rosanna Lane et al.
  • 1School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
  • 2Cabot Institute, University of Bristol, Bristol, BS8 1UJ, UK
  • 3University of Saskatchewan, Centre for Hydrology, Canmore, Alberta, T1W 3G1, CANADA
  • 4Department of Geography, University of Zurich, Zurich, Switzerland
  • 5Department of Civil Engineering, University of Bristol, Bristol, BS8 1TR, UK
  • 6Institue of Environmental Science and Geography, University of Potsdam, 14476 Potsdam, Germany
  • acurrently at: UK Centre for Ecology & Hydrology, Wallingford, OX10 8BB, UK

Abstract. Climate change may significantly increase flood risk across Great Britain (GB), but there are large uncertainties in both future climatic changes and how these propagate into changing river flows. Here, the impact of climate change on the magnitude and frequency of high flows is modelled for 346 larger (> 144 km2) catchments across GB using the latest UK Climate Projections (UKCP18) and the DECIPHeR hydrological modelling framework. This study provides the first spatially consistent GB projections including both climate ensembles and hydrological model parameter uncertainties.

Generally, results indicated an increase in the magnitude and frequency of high flows (Q10, Q1 and annual maximum) along the west coast of GB in the future (2050–2075), with increases in annual maximum flows of up to 65 % for west Scotland. In contrast, median flows (Q50) were projected to decrease across GB. All flow projections contained large uncertainties, and while the RCMs were the largest source of uncertainty overall, hydrological modelling uncertainties were considerable in east and south-east England. Regional variation in flow projections were found to relate to i) differences in climatic change and ii) catchment conditions during the baseline period as characterised by the runoff coefficient (mean discharge divided by mean precipitation). Importantly, increased heavy-precipitation events (defined by an increase in 99th percentile precipitation) did not always result in increased flood flows for catchments with low runoff coefficients, highlighting the varying factors leading to changes in high flows.

These results provide a national overview of climate change impacts on high flows across GB, which will inform climate change adaptation, while also highlighting the need to account for uncertainty sources when modelling climate change impact on high flows.

Rosanna Lane et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-321', Anonymous Referee #1, 22 Jul 2021
    • AC1: 'Reply on RC1', Rosanna Lane, 22 Nov 2021
  • RC2: 'Comment on hess-2021-321', Anonymous Referee #2, 30 Jul 2021
    • AC2: 'Reply on RC2', Rosanna Lane, 22 Nov 2021
  • RC3: 'Comment on hess-2021-321', Anonymous Referee #3, 13 Sep 2021
    • AC3: 'Reply on RC3', Rosanna Lane, 22 Nov 2021

Rosanna Lane et al.

Rosanna Lane et al.

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Short summary
This study modelled the impact of climate change on river high flows across Great Britain (GB). Generally, results indicated an increase in the magnitude and frequency of high flows along the west coast of GB by 2050–2075. In contrast, average flows decreased across GB. All flow projections contained large uncertainties; the climate projections were the largest source of uncertainty overall but hydrological modelling uncertainties were considerable in some regions.