The EFAS medium-range flood forecasts provide an overview of flood probability over the coming 10 days. They are created by comparing the EFAS forecast simulations with EFAS flood threshold levels. These flood threshold levels are calculated for every grid cell, based on a discharge time series simulated by the operational LISFLOOD from observed meteorological data.

EFAS medium-range flood forecast products are displayed as colour coded overview maps and time series information at reporting points that can be viewed under the ‘Flood Summary’ layer of the mapviewer. They are organised in four categories:

  • Reporting points: points in the river network highlighted because their flood forecast probability meets reporting criteria. Two threshold levels are used: 2-year return period (2yr RP) and 5-year return period (5yr RP)
  • Threshold Level Exceedance: reporting points showing the maximum flood threshold level expected to be exceeded the day of the forecast date (ongoing); within the next 1-2 days (1-2 days); within next 3-5 days (3-5 days); beyond day 6 (>5 days).
  • Flood probability: model cells of the river network where there’s probability of exceeding the 5-yr return period threshold level within (< 48h) or after (>48h) the next 48 hours. The probability is calculated based on the ECMWF-ENS EFAS forecast.
  • Real-time Hydrographs: for selected points where near real-time river discharge is available to EFAS, level of probability exceeding an average yearly maximum discharge within the next 10 days. The probability is calculated based on post-processing of the ECMWF-ENS EFAS forecast and observed discharge

Extra local information associated with each flood forecast product is available from the map viewer as pop-up plots, except for the ‘Flood Probability’ product. They include flood hydrographs, persistence diagrams and summary diagrams of catchment meteorological forcings.

EFAS medium-range flood forecasts produced at least 30 days earlier are freely available to view. Real-time EFAS medium-range flood forecasts are only available under certain conditions. Visit the EFAS data access pages to learn more on data restrictions.