A region of influence approach for attributing fluvial climate change allowances

ABSTRACT

For practical purposes the current guidance for attributing fluvial climate change allowances (recommended peak-discharge adjustments) in England is based on percentage changes to the 50-year return level attributed homogeneously to geographical regions. This proof-of-concept study introduces an approach enabling the practitioner to derive allowances for the full distribution of extremes (as opposed to single return periods) and is based on catchment characteristics. A region of influence approach, adopted by the Flood Estimation Handbook (FEH), is applied to estimate changes to the parameters of statistical models of extreme flows, as opposed to flow peaks. The approach is distribution neutral and can be applied to any catchment for which an FEH analysis has been undertaken. Results for an example scenario (Representative Concentration Pathway (RCP)8.5 2080s) are compared to a geographically regional method and an example is provided for a single catchment estimating extremes with the FEH method and adjusting them for the RCP8.5 2080s scenario.

KEYWORDS:

• climate change
• rainfall runoff modelling
• flood frequency
• UKCP18
• Flood Estimation Handbook

Editor A. Castellarin Guest Editor E. Volpi

Editor A. Castellarin Guest Editor E. Volpi

Acknowledgements

The author thanks all those responsible for the availability of the National River Flow Archive, as well as those responsible for the production of the CAMEL dataset, and acknowledges the work of the UK climate projections project. Finally a thank you to Duncan Faulkner of JBA Consulting who provided an initial review of the paper before it was submitted.