Assessing the impacts of climate change on floods in England using a hydrological model at daily and hourly timesteps

Zha, Qianyu (2025) Assessing the impacts of climate change on floods in England using a hydrological model at daily and hourly timesteps. Doctoral thesis, University of East Anglia.

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Abstract

Climate change is expected to increase the frequency and intensity of extreme precipitation events, thereby increasing flood risks. In England, where fluvial flooding already poses significant challenges, these risks are expected to intensify further. This thesis assesses future climate impacts on fluvial flood hazards by applying bias-corrected UKCP18 climate model outputs to a gridded hydrological model. Firstly, biases in the UKCP18 Regional Climate Model (RCM) and Convection-Permitting Model (CPM) were evaluated and corrected using empirical quantile mapping. Bias correction substantially improved consistency with observations, ensuring more reliable input for hydrological modelling. Secondly, a 1 km resolution distributed hydrological model (HBV-TYN) was calibrated at both daily (DM) and hourly (HM) time steps for 311 catchments in England. HM outperforms the DM in capturing peak flows and short-duration variability, particularly in small, steep, and rapidly responding catchments, while both DM and HM achieved satisfactory performance (Nash-Sutcliffe efficiency ≥ 0.6) in the majority of catchments. The comparative analysis between DM and HM highlights the advantages of different temporal resolutions in flood simulation. Finally, future flow projections were analysed by driving the DM with bias-corrected RCM data and the HM with bias-corrected CPM data. There are clear differences between RCM- and CPM-driven flow projections. By the 2070s, CPM-projected winter flows could be up to four times greater than those projected by the RCM, while summer flow reductions could be 4-15% more. These results suggest that existing climate impact assessments may have considerably underestimated the changes, potentially leading to under-designed climate resilience policies. These pronounced changes underscore the need for high-resolution CPMs and hydrological models to generate more reliable projections, essential for preparing for future extreme weather challenges.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Nicola Veasy
Date Deposited:	24 Jun 2025 08:51
Last Modified:	24 Jun 2025 08:51
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99691
DOI:

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