Incorporating sedimentological data in UK flood frequency estimation

<p>This study presents a new analytical framework for combining historical flood data derivedfrom sedimentological records with instrumental river flow data to increase the reliability offlood risk assessments. Historical flood records were established for two catchments throughre-analysis of sedimentological records; the Nant Cwm-du, a small, steep upland catchment inthe 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 estimationmethods in combination with a Generalised Logistic distribution; this enables thesedimentological data to be combined effectively with existing instrumental river flow data.The results from this study are compared to results obtained using existing industry standardmethods based solely on instrumental data. The comparison shows that inclusion ofsedimentological data can have an important impact on flood risk estimates, and that themethods are sensitive to assumptions made in the conversion of the sedimentological recordsinto flood flow data. As current industry standard methods for flood risk analysis are known tobe highly uncertain, the ability to include additional evidence of past flood events derived fromsedimentological records as demonstrated in this study can have a significant impact on floodrisk assessments.</p>