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By clicking on specific catchments, users are able to see a pop-out window showing the forecasted impact level on the impact matrix (Figure 1). There is also some additional information on the number of people, education, health and energy generation facilities forecasted to be affected.
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Figure 1: Example of the Radar-based river flash flood impact catchment summary layer for 0-6 hours on the 31st August 2022 at 00:00 UTC near Strasbourg, France (left). River catchments where flash flood impacts are possible are shaded according to their classification on an impact matrix (shown on the left side of the figure), which can be displayed when a catchment is clicked. Additional exposure information is given in a table at the bottom of the pop out window (shown in the bottom left of the figure). On the right is the impact matrix which is used to assign the river flash flood impact category.
Methodology
There are three main steps in the generation of these four river flash flood impact catchments summary layers: 1) river flash flood hazard forecasting using blended radar and NWP precipitation, 2) river flash flood impact prediction, 3) summarising river flash flood impacts at the catchment scale (Figure 2).
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A probabilistic forecast of river flash flood hazard is generated firstly by blending hourly nowcasts of precipitation derived from radar observations with NWP precipitation forecast from the ECMWF ensemble. More details about how the two datasets are blended can be found on this page: TAMIR Radar-based Total Precipitation 80th Percentile - copy. Radar data are not available in all areas covered in the EFAS spatial domain, a map of radar coverage can be found in the Radar Coverage layer. The resulting blended 51-member ensemble precipitation forecasts have a spatial resolution of 2 km, and 1-hour time steps for the first 12 hours lead time which increases to 6-hours thereafter for a maximum lead time of 120-hours (5 days).
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