Probabilistic Inundation Forecasting

Many existing operational hydrological ensemble forecasting systems only produce forecasts of river discharge. It is possible to convert discharge forecasts into inundation extents, in particular because there are well-established tools for the estimation of inundation hazard. The basic components of the modeling framework from which to produce inundation forecasts are: (1) meteorological forcing; (2) a hydrological model; (3) a hydraulic model; and; (4) a methodology to derive probabilistic inundation maps. We perform all those steps using the example of the 2013 River Elbe event. We validate the maps of flooding probability against the observations. We stress the importance of the spatial discretization of the digital elevation maps (DEM) and the influence of the resolution of the flood defense topographic features. This study shows that up to 80% of the flooded area along the Elbe in 2013 could have been forecasted to inundate 7 days in advance, using the probabilistic modeling framework proposed.