National performance of flood forecasting models

Wells, S.C.; Moore, R.J.; Cole, S.J.. 2016 National performance of flood forecasting models. Bristol, UK, Environment Agency, 220pp. (Report SC130006/R3, CEH Project no. C04830) (Unpublished)

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A national assessment of the performance of flood forecasting models - operated in real-time by the Environment Agency, Natural Resources Wales and the national Flood Forecasting Centre - is crucial to their informed use for flood guidance across England & Wales. It is also essential to guide future strategic investment in flood incident management. This report provides a nationwide analysis of flood forecasting model performance across implementations by local centres of the National Flood Forecasting System (NFFS). It considers regional and model-type differences and presents an overview of the current forecasting capability of models in operational use. Previous forecast performance studies of local models were performed on a grouped-catchment or regional basis and not necessarily using a consistent assessment framework. Spatial analysis of flood forecasting model performance in this report is based on Wales and the English geographical regions that align to the old Environment Agency region names. The report also extends the forecast model performance information available for the Grid-to-Grid (G2G) model, a distributed grid-based hydrological model with rainfall-runoff and flow routing elements. G2G is implemented within the NFFS for the Flood Forecasting Centre as an area-wide national model across England & Wales. The G2G model forecasts are compared with those from the local models which span a variety of model-types: rainfall-runoff models of conceptual and transfer function form, and channel flow routing models of hydrological and hydrodynamic form. The approach taken to performance assessment has been to gather “raw” data (river flow observations, flow forecasts and historical simulation of flows) from previous local model performance studies. While there are significant regional differences in how these data were gathered and in the methodologies used to generate flood forecast model outputs, collation of the underlying “project” datasets has allowed standardisation of the methods of assessment used here. This report presents the background to a flood forecasting model “Performance Summary”, as a template for reporting performance at any site from a given model-type, including the underlying performance measures employed. The Performance Summary takes the form of one A4 page for each model at each site, and contains a variety of different performance measures and graphical displays. Just over 2,000 Performance Summary pages have been produced for those working in an operational setting or in strategic planning. The results contained in the Performance Summary for each site and model combination have been brought together and used as the basis of a national analysis and summary. This constitutes an extensive national evidence-base of model performance, stratified by model-type, model-group, geographical region and lead-time. Where there is a choice of model forecast, it also includes information on comparative performance. This report provides an update to the evidence-base contained in R&D Report SC130006/R2. It includes performance analysis of a further 245 local site models, with a total of 921 now analysed along with the 829 sites at which G2G is assessed. The R&D report should be consulted for further background of a strategic nature and omitted here as not of such immediate operational relevance.

Item Type: Publication - Report (UNSPECIFIED)
CEH Sections/Science Areas: Reynard
Funders/Sponsors: Environment Agency, Centre for Ecology & Hydrology
Additional Keywords: flood forecasting, model performance, rainfall-runoff, distributed, G2G
NORA Subject Terms: Meteorology and Climatology
Atmospheric Sciences
Date made live: 30 Jun 2016 14:54 +0 (UTC)

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