Flood impact forecasts are especially important in the preparedness phase, to support the planning and allocation of rescue assets, and to get a first estimate of the forecasted flood event’s potential socio-economic consequences.
In GloFAS, the flood impact forecasts are based on three components: 1) medium-range flood forecasts, 2) event-based rapid flood mapping, and 3) impact assessment.
- Medium-range flood forecast: every time a flood event is forecasted in GloFAS , the magnitude of the forecasted peak discharge (based on the ECMWF-ENS GloFAS ensemble forecast median for the full forecasting period) is compared against the local flood protection levels from FLOPROS. River grid cells where the protection levels are exceeded are selected for the following steps of the procedure.
- Rapid flood mapping: for each GloFAS river section identified in step 1, flood prone areas are delineated, using a catalogue of flood hazard maps. The obtained event-based hazard map has a spatial resolution of 0.00833 by 0.00833 degrees (approximately 1 km by 1 km) and is shown on the “Rapid Flood Mapping” layer.
- Impact assessment: the event-based hazard maps are combined with exposure information to assess regional impacts (shown on the “Rapid Impact Assessment” layer). Considered exposure includes population, infrastructure and land cover. The impact is calculated by combining the flood severity and probability with the exposed population. The result is summarised on administration units sourced from NUTS in Europe and GADM in the rest of the world.
The GloFAS flood impact forecasts are provided to the users as a set of dedicated layers described.