Representing the spatial variability of rainfall for input to the G2G distributed flood forecasting model: operational experience from the Flood Forecasting Centre

Over the year 2010 the Flood Forecasting Centre (FFC) calibrated and implemented a distributed flood forecasting model to support the FFC’s remit to provide flood risk forecasts across England and Wales, UK. The distributed nature of the model, designed to run at 15-min time-steps on a 1 km2 grid, enables the spatial variability of rainfall measurements and forecasts, rather than lumped catchment averages, to be captured. Such a distributed model should therefore benefit greatly from the spatial and temporal resolution afforded by radar observations. Initial results have highlighted the importance of the quality of the gridded rainfall fields and in a number of cases erroneous radar rainfall data have been shown to contribute to poor model performance. It is suggested that gridded datasets of sufficient quality will be best provided by capturing the spatial variability inherent in radar data together with raingauge data in a merged product.