The UKCEH Flood Event Data Suite

Flood event analysis, using both rainfall and river flow data, enables understanding of how river catchments respond to different rainfall events under varying antecedent conditions, initial conditions, and rainfall event characteristics. (e.g. mean and peak rainfall intensity, initial flow rate, antecedent rainfall total). Large datasets of flood events, collected across many river catchments, can enhance our understanding of how catchment properties influence catchment response, and how changes in catchment and climate characteristics cause changes in rainfall-runoff relationships during flood events. These datasets can support the development of flood risk and flood response models, and increase resilience to extreme events.

The UKCEH Flood Event Data Suite consists of a procedure to identify paired rainfall-runoff events from paired time-series, the dataset of events identified when applied to open-access UK precipitation and flow data, and a database of rainfall statistics and runoff signatures derived from those events.

The procedure identifies paired rainfall-runoff events by starting at peak flow and extending forwards and backwards to common start and end times that encapsulate both complete rainfall and complete runoff events. Using open-access data, the procedure is intended to be re-run periodically as the input data sources are updated, with the resulting dataset versions made available through an interactive public portal hosted by the UK National River Flow Archive, and static “snapshots” released periodically through the UK Environmental Information Data Centre.

The dataset in its most recent form includes approximately 175,000 paired rainfall-runoff events extracted from 1200 gauged catchments over a long monitoring period (1990-2016 inclusive), for approximately 5.4 events per station per year, at a high time resolution consistent across all events (15 minutes for flow, 60 minutes for rainfall). Other key features include a high station density (approximately 1 per 200 km²), a wide range of catchment properties, including area (< 1 to approximately 10,000 km²), mean annual rainfall (approximately 500 to 3500 mm/year), baseflow index (approximately 0.2 to 1) and urbanization (0% to approximately 70%), long flow recessions captured, publicly available catchment shapefiles, allowing users to extract information from other spatial datasets using consistent catchment outlines, a single peer-reviewed source for all rainfall data, and (planned) wide availability through an open access repository and portal.

Analysis of a high-quality subset of the derived database of rainfall statistics and runoff signatures (677 catchments, ~7500 events) has identified that different catchment descriptors influence peak flow, total volume and rate-of-rise, changing with event rarity, correlations between peak flow and total volume increase with catchment size, and summer events typically have high rates-of-rise and volumes relative to baseflow, while spring events typically have the opposite.