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Lookup NU author(s): David Archer, Professor Hayley Fowler
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025 David R. Archer et al.Extremely rapid rates of rise in river level and discharge are a subset of flash floods ("abrupt wave front floods", AWFs) and are separate hazards from peak river level. They pose a danger to life to river users and occur mainly in the summer. Using level and discharge records from 260 Scottish gauged catchments, we present the spatial distribution of annual maximum 15 min rises in river level and discharge, along with derived metrics to assess the severity of AWF events. These include normalised and proportional measures of flow change, as well as ratios that characterise the intensity of AWF events. We estimate wave celerity by analysing the time difference in wave onset recorded by successive gauging stations along a river channel. This approach is applied to several AWF events on the river Findhorn in northeast Scotland, allowing for detailed examination of their dynamics. Our findings suggest that flood forecasting models with outputs of peak discharge and river level may not adequately represent the risk posed by rapidly rising flows, especially at national scales where hydroclimatic and geomorphological variability trigger different AWF metrics. We show that AWFs may intensify downstream, with wave fronts steepening as they travel through lowland river reaches, as observed in multiple events on the river Findhorn, showing a necessity of more accurate and frequent river measurements. We conclude that AWFs need better monitoring forecasting and warning, particularly as extreme downpours are becoming more frequent with global warming.
Author(s): Archer DR, Fileni F, Watkiss SA, Fowler HJ
Publication type: Article
Publication status: Published
Journal: Hydrology and Earth System Sciences
Year: 2025
Volume: 29
Issue: 20
Pages: 5777-5789
Online publication date: 28/10/2025
Acceptance date: 14/08/2025
Date deposited: 10/11/2025
ISSN (print): 1027-5606
ISSN (electronic): 1607-7938
Publisher: Copernicus Publications
URL: https://doi.org/10.5194/hess-29-5777-2025
DOI: 10.5194/hess-29-5777-2025
Data Access Statement: The 15 min flow and level data used in this study are available at the SEPA Time Series Data Service (API) (https://timeseriesdoc.sepa.org.uk/, last access: 11 October 2025). The code and rates of rise data extracted from the time series may be accessed by other researchers at https://doi.org/10.5281/zenodo.14771542 (Fileni, 2025) or via the GitHub repository (https://github.com/felipef93/ror_scotland, last access: 15 October 2025) for the latest version.
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