The European Flood Awareness System (EFAS) is one service of the Copernicus Emergency Management Service (CEMS). It is designed to support preparatory measures for flood events across Europe, particularly in large trans-national river basins. 

Information on upcoming flood events is provided through various products that are available on the EFAS Map Viewer and are produced by the computational centre. The following will provide you with an overview on not only the EFAS products, but even the underlying hydrological forecasting chain, and the Notifications which are based on the EFAS products. 

 

The EFAS hydrological forecasting chain

This are key elements in the EFAS production chain: the meteorological forcing and land surface data; the hydrological models; and the finally the EFAS forecasts and products.

 

EFAS chain

EFAS hydrological forecasting chain

  • The meteorological forcing and land surface data

    The meteorological forcing data are all the information necessary to produce hydrological simulations. Historical hydro-meteorological time series records are used to calibrate and validate the hydrological model, and to define the flood thresholds used to derive EFAS products. Real-time hydro-meteorological observations are necessary to define the starting points of the hydrological forecasts, also called initial conditions. They are collected from national agencies and quality checked by the MDCC and HDCC before being transferred to the EFAS Computation Centre (COMP). Meteorological forecasts are used to provide the future meteorological input to the hydrological models.

    The land surface data, including land surface information and model parameters, are all the information necessary to set-up and implement the hydrological models.

  • EFAS hydrological models

    EFAS hydrological models transform the meteorological forecasts into hydrological forecasts by mimicking the hydrological land processes by a set of equations. In EFAS, the hydrological model LISFLOOD is primarily used for medium- and seasonal-range forecasts, whilst conceptual hydrological algorithms are used for the flash flood indicators.

    LISFLOOD is a spatially distributed rainfall-runoff-routing model. It was first developed at the Joint Research Centre in 2000, and has been used for operational flood forecasting at the pan-European scale since the beginning of EFAS. Read more to learn about LISFLOOD in the EFAS Wiki and LISFLOOD OS page.

  • EFAS Forecasts and Products

    EFAS forecasts are produced by forcing the LISFLOOD hydrological model with a range of meteorological forecasts. They consist of daily and 6-hourly discharge time series for every grid cell of the river network, starting the day of the forecast and ending the last day of the meteorological forecast forcing.

    Different types of meteorological forecast forcings are used in EFAS: deterministic forcings (i.e. single realisation from a single model) and ensemble forcings (i.e. multiple realisations -also called ensemble members - from a single model). Probabilistic hydrological forecasts are issued based on the latter and give a quantifiable range of most probable future states. 

    ensemble forecasting flowchart

    Schematic of ensemble forecasting

    EFAS products are a set of maps and graphs that highlight possible future flood risk from the EFAS forecast simulations. They are produced by comparing the forecasts with reference flood thresholds, and categorised in different lead-time:

    These products can be viewed in the Map Viewer under categories ‘Flood summary’, 'Hydrological' and ‘Flash Flood’.

    To respect Member States authorities regarding flood warnings, some EFAS forecasts and products are only accessible to EFAS partners in real time. However, archived EFAS forecasts and products older than one month are freely accessible under specific terms and conditions. To learn more on EFAS data restrictions and terms and conditions, visit the EFAS conditions of access page.

    To respect Member States authorities regarding flood warnings, some EFAS forecasts and products are only accessible to EFAS partners in real time. However, archived EFAS forecasts and products older than one month are freely accessible under specific terms and conditions. To learn more on EFAS data restrictions and terms and conditions, visit the EFAS conditions of access page.

     

EFAS Versioning

The EFAS system undergoes constant changes and improvements, both in the modelling system and the products that are produced for the web and web services. To make it possible for the EFAS users to understand and adapt to changes that might affect their work, all changes are collected into official EFAS and are given an EFAS version number. The version number has two digits, the first marks a major release, and the second a minor. A major release consists of changes that will affect the EFAS operational centres or ERCC. Please see our EFAS Wiki for more information EFAS versions and planned releases.

 

EFAS Flood Notifications

EFAS Flood notifications are issued by the EFAS duty forecasters to highlight potential future flood event for the EFAS partners and ERCC. They are based on EFAS flash flood and medium range forecasts, and classified in three types of notifications: Formal notification, Informal notifications and Flash Flood notifications. All notifications are sent to EFAS partners and the ERCC once issued, and shown on the map viewer by activating the ‘Active Notifications’ layer.  EFAS notifications are the responsibility of CEMS Hydrological Forecast Centre - Analytics and Dissemination (DISS).