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Scenario-neutral approach to climate change impact studies: application to flood risk

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journal contribution
posted on 16.04.2019 by Christel Prudhomme, Robert Wilby, Sue M. Crooks, Alison L. Kay, Nick S. Reynard
This paper presents a novel framework for undertaking climate change impact studies, which can be used for testing the robustness of precautionary climate change allowances used in engineering design. It is illustrated with respect to fluvial flood risk in the UK. The methodology departs from conventional scenario-led impact studies because it is based on sensitivity analyses of catchment responses to a plausible range of climate changes (rather than the time-varying outcome of individual scenarios), making it scenario-neutral. The method involves separating the climate change projections (the hazard) from the catchment responsiveness (the vulnerability) expressed as changes in peak flows. By combining current understanding of likelihood of the climate change hazard with knowledge of the sensitivity of a given catchment, it is possible to evaluate the fraction of climate model projections that would not be accommodated by specified safety margins. This enables rapid appraisal of existing or new precautionary allowances for a set of climate change projections, but also for any new set of climate change projections for example arising from a new generation of climate models as soon as they are available, or when focusing on a different planning time horizon, without the need for undertaking a new climate change impact analysis with the new scenarios. The approach is demonstrated via an assessment of the UK Government’s 20% allowance for climate change applied in two contrasting catchments. In these exemplars, the allowance defends against the majority of sampled climate projections for the 2080s from the IPCC-AR4 GCM and UKCP09 RCM runs but it is still possible to identify a sub-set of regional scenarios that would exceed the 20% threshold.


Environment Agency for England and Wales, the UK Department for Food and Rural Affairs (Defra) and the Natural Environment Research Council (NERC).



  • Social Sciences


  • Geography and Environment

Published in

Journal of Hydrology






198 - 209


PRUDHOMME, C. ... et al, 2010. Scenario-neutral approach to climate change impact studies: application to flood risk. Journal of Hydrology, 390 (3-4), pp.198-209.


© Elsevier


AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at:

Publication date



This paper was accepted for publication in the journal Journal of Hydrology and the definitive published version is available at






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