Incorporating sedimentological data in UK flood frequency estimation

Abstract

This study presents a new analytical framework for combining historical flood data derived from sedimentological records with instrumental river flow data to increase the reliability of flood risk assessments. Historical flood records were established for two catchments through re‐analysis of sedimentological records; the Nant Cwm‐du, a small, steep upland catchment in the Cambrian Mountains of Wales, and a piedmont reach of the River Severn in mid Wales. The proposed framework is based on maximum likelihood and least‐square estimation methods in combination with a Generalised Logistic distribution; this enables the sedimentological data to be combined effectively with existing instrumental river flow data. The results from this study are compared to results obtained using existing industry standard methods based solely on instrumental data. The comparison shows that inclusion of sedimentological data can have an important impact on flood risk estimates, and that the methods are sensitive to assumptions made in the conversion of the sedimentological records into flood flow data. As current industry standard methods for flood risk analysis are known to be highly uncertain, the ability to include additional evidence of past flood events derived from sedimentological records as demonstrated in this study can have a significant impact on flood risk assessments.

A sub-centennial-scale optically stimulated luminescence chronostratigraphy and late Holocene flood history from a temperate river confluence

“…Additionally, in clastic-dominated alluvial sequences, suitable organic material is only occasionally encountered, and, where it is, its reliability for dating is also questionable. These factors have made it difficult to relate the sedimentary record to documentary or instrumental flood histories, which in Europe rarely go back further than 100-250 yr (Macdonald and Sangster, 2017;Longfield et al, 2018). In this paper, we show how the confluence of the Rivers Severn and Teme (United Kingdom) has evolved over the past two millennia.…”

A 439-year simulated daily discharge dataset (1861–2299) for the upper Yangtze River, China

“…The most severe flood that can be tracked in the upper Yangtze River occurred in 1870, with a flood peak of approximately 100 500 m 3 s −1 at the Yichang station located downstream of the Cuntan station (Changjiang Water Resources Commission, 2002). The peak flows reached 63 600 m 3 s −1 and 64 600 m 3 s −1 at the Cuntan station and the Yichang station, respectively, during the 1931 flood and 52 200 and 66 800 m 3 s −1 , respectively, during the 1954 flood (Hu and Luo, 1992;Luo and Le, 1996). During the strongest flood of the 20th century in the Yangtze River, the peak flow at the Cuntan station reached 68 500 m 3 s −1 in 1998 (Changjiang Water Resources Commission, 2002).…”

Reconstructing the peak flow of historical flood events using a hydraulic model: The city of Bath, United Kingdom

“…There is a certain urgency implied as the type of information required may be considered of little or no importance to current management, and therefore not deemed a priority for preservation efforts. However, as demonstrated above (and by other researchers) the inclusion of historical flood data can have a dramatic effect on the outcome of a flood frequency analysis (e.g., Engeland, Aano, Steffensen, Støren, & Paasche, 2020; Longfield et al, 2019; Macdonald et al, 2013; Prosdocimi, 2018; Wilhelm et al, 2019).…”