28 Jul 2022
28 Jul 2022
Status: this preprint is currently under review for the journal HESS.

Widespread flooding dynamics changing under climate change: characterising floods using UKCP18

Adam Griffin1, Alison Kay1, Paul Sayers2, Victoria Bell1, Elizabeth Stewart1, and Sam Carr2 Adam Griffin et al.
  • 1UK Centre for Ecology & Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK
  • 2Sayers and Partners, Watlington, Oxfordshire, OX49 5PY, UK

Abstract. An event-based approach has been used to explore the potential effects of climate change on the spatial and temporal coherence of widespread flood events in Great Britain. Time series of daily mean river flow were generated using a gridded national-scale hydrological model (Grid-to-Grid) driven by the 12-member ensemble of regional climate projections from UKCP18. Gridded flow series were generated nationally for 30-year baseline (1980–2010) and future (2051–2080) time-slices from which sets of widespread extreme events were extracted. These events were defined as exceeding an at-site 99.5th percentile (equivalent to two days per year) simultaneously over an area of at least 20 km2, allowing events to last up to 14 days. This resulted in a set of 14,400 widespread events: approximately 20 events per year, per ensemble member, per time-slice. Overall, results have shown that events are more temporally concentrated in winter in the future time-slice compared to the baseline. Distributions of event area were similar in both time-slices, but the distribution of at-site return periods showed some heavier tails in the future time-slice. Results were consistent across ensemble members, with none showing significant difference in distribution.

Adam Griffin 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-2022-243', Rory Nathan, 16 Aug 2022
    • AC1: 'Reply on RC1', Adam Griffin, 03 Nov 2022
  • RC2: 'Comment on hess-2022-243', Lina Stein, 26 Sep 2022
    • AC2: 'Reply on RC2', Adam Griffin, 03 Nov 2022

Adam Griffin et al.

Data sets

Peak flow and probability of exceedance data for Grid-to-Grid modelled widespread flooding events across mainland GB from 1980-2010 and 2050-2080 Griffin, A.; Kay, A.; Bell, V.; Stewart, E. J.; Sayer, P.; Carr, S.

Adam Griffin et al.


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Short summary
Widespread flooding is a major problem in the UK, and is greatly affected by climate change and land-use change. To look at how widespread flooding changes in the future, climate model data (UKCP18) was used with a hydrological model (Grid-to-Grid) across the UK, and 14400 events were identified between two timeslices: 1980–2010 and 2050–2080. There was a strong increase in the number of winter events in the future timeslice, and in the peak return periods.