Operational use of a grid-based model for flood forecasting

Following the summer 2007 floods in England and Wales, a new context for flood forecasting emerged through the recommendations set out in the Pitt review. This paper presents the operational challenges being addressed by the Flood Forecasting Centre (FFC) – a joint venture between the Environment Agency (EA) and the Met Office (MO) – to deliver forecasts of flood risk across England and Wales with longer lead times (out to 5 days ahead) and, on a shorter timescale, for rapid response catchments. These are both key recommendations of the Pitt review. As a joint venture, the FFC is uniquely placed to meet these objectives and, as a first step, has implemented a distributed hydrological model, grid-to-grid (G2G), calibrated across England and Wales, on the EA's national flood forecasting system. Also fundamental to successfully meeting these objectives is the FFC's ability to utilise the latest MO advances in high-resolution numerical weather prediction and nowcasting of rainfall, including forecasts in probabilistic form. Early results from applying the model to the Cumbria floods of November 2009 demonstrate that this is an effective approach for generating longer lead-time flood forecasts. The results also illustrate that this methodology is best used in combination with current regionally based flood forecasting tools.