FAQs

What is EFAS?

The European Flood Awareness Systems (EFAS; www.efas.eu) of the Copernicus Emergency Management Service (CEMS; https://emergency.copernicus.eu/) is the first operational pan-European flood forecasting and monitoring system. EFAS provides a wide range of complementary early flood forecasting information based on models, satellite and in-situ data,  to support national and regional authorities with flood risk management duties in arranging preparatory measures before an event strikes. In addition, EFAS provides a unique overview across Europe and neighbouring countries on currently observed and forecasted flood events.

The Joint Research Centre is one of the main players in setting up systems to predict and monitor floods. What was the impetus to set this up and what is the origin story? Why and when was EFAS founded?

In 1999, the Joint Research Centre (JRC) of the European Commission started a research study for a European-scale flood forecasting system (EFFS) in collaboration with national authorities and experts from the different Member States.

The disastrous floods in Elbe and Danube rivers in 2002 confronted the European Commission with non-coherent flood warning information from different sources and of variable quality, complicating planning and organization of aid. The EFFS developed at the JRC provided successfully ad-hoc simulations of the ongoing floods and a forecast on how the flood waves could be expected to travel down the Danube River.

In response to this event and following a Communication of the Commission on the Elbe and Danube floods, the Joint Research Centre of the European Commission was assigned with the task to further develop EFFS into a fully operational, European-wide flood forecasting model. The first developments towards such a European Flood Awareness System (EFAS) were initiated in 2003, together with experts from Austria, the Czech Republic, Germany, Hungary, and Slovakia and using forecasts from the German weather service.

In 2004, a collaboration agreement with ECMWF was signed, allowing the JRC to incorporate also ECMWF ensemble prediction data and its higher resolution deterministic forecast into EFAS in real-time.

From 2005 to 2010 EFAS was tested in real-time mode, together with the newly established EFAS partner network, consisting of national and regional flood forecasting authorities, and later also with the European Civil Protection.

In 2011, EFAS became part of the Copernicus Emergency Management Service's initial operations and in support of European Civil Protection. The operational components have been outsourced to Member State organizations. EFAS is running fully operational since autumn 2012.

The EFAS system is the cornerstone for flood forecasting. On which kind of models, data, and satellite imagery is this based?

EFAS is based on the hydrological model LISFLOOD (open source and available under: https://ec-jrc.github.io/lisflood/). The model is updated daily with the most recent meteorological observations and is forced twice daily with updated probabilistic meteorological forecasts from the European Centre for Medium-Weather Forecasts (ECMWF), the German Weather Service and the COSMO consortium (http://www.cosmo-model.org/content/tasks/operational/leps/) to produce 6-hourly probabilistic hydrological predictions for entire Europe. Those are then analysed twice daily by trained hydrologists against standardized criteria to identify potentially upcoming floods.

An overview of the system can be found here: https://www.efas.eu/en/overview 

Furthermore, the CEMS-Floods wiki contains the entire technical documentation of EFAS and can be freely accessed under: https://confluence.ecmwf.int/display/CEMS/European+Flood+Awareness+System  

Can you give some more insights into the data sources - like the number and type of satellites involved, the frequency of data they send, and other kinds of data sources (automatic and manual).

EFAS relies on different data sources such as in-situ data (meteorological and hydrological observations), model data (weather predictions from different numerical weather prediction models) as well as satellite data (e.g. land use maps or digital elevation maps required by the hydrological model). Numerical weather prediction data, as well as in-situ data, are collected and processed in near-real-time. For example, EFAS is collecting meteorological and hydrological data from more than 50 different data providers in Europe (see here https://www.efas.eu/en/share-your-data-efas ).  

All data collected in real-time is processed automatically.  Other input data that does not require frequent updates (for example the digital elevation model or the land use maps) are typically updated during major system upgrades (I.e. improvements to the model).

What’s the technical backbone of the EFAS system? How are data processed and handled?

EFAS is executed by a number of service providers (see also here: https://www.efas.eu/en/european-flood-awareness-system-efas).

The European Center for Medium-Range Weather Forecast (ECMWF) runs the hydrological model and produces all forecast products on a daily basis.

Hydrological and Meteorological data for EFAS is collected by the German Weather Service, KISTERS AG, Soologic.

The daily analysis of EFAS forecasts and user support is provided by the Swedish Meteorological and Hydrological Institute, Rijkswaterstaat (Netherlands), and the Slovak Hydro-Meteorological Institute.

How is the data put together for effective and day-to-day mapping and tracking?

It is important to note that EFAS provides river flow predictions and does not model flood extent. The monitoring of flooded areas is provided by the CEMS rapid mapping component (https://emergency.copernicus.eu/mapping/list-of-activations-rapid).

Probabilistic medium-range flood forecasts (on which the EFAS notifications are based) for the next 10 days are computed twice daily based on running the hydrological model LISFLOOD with the incoming meteorological forecasts (so-called: ensemble meteorological predictions). Those forecasts are published on the EFAS map viewer (https://www.efas.eu/efas_frontend/#/home) twice a day as soon as they have been computed. They are visualized against thresholds that facilitate the analysis of the forecasts (done by trained hydrologists). Once a potentially upcoming flood has been identified (based on set standards) a notification is sent out to the relevant EFAS partner and the information is also included in a short summary which is provided to the Emergency Response Coordination Centre (ERCC - https://ec.europa.eu/echo/what/civil-protection/emergency-response-coordination-centre-ercc_en ) of the European Commission, to provide an overview of ongoing and upcoming floods at European wide level. The published FAQ on EFAS notifications provides more details on what information an EFAS notification contains and how they are used by national authorities (https://www.efas.eu/en/news/faq-efas-and-recent-flood-events)

What other services relevant for flood risk management are available under Copernicus Emergency Management Service

The rapid mapping component of the Copernicus Emergency Management Service (CEMS) provides mapping products based on satellite imagery and is usually activated for a certain area by an authorised user (typically a regional/national authority responsible for civil protection). For this event,_ the rapid mapping component of CEMS is providing critical flood maps and damage assessments since 13 July for the floods in Germany, Netherlands, Belgium, and Switzerland. An EFAS-based pre-tasking of the rapid mapping component was launched on 14th July for the Upper and Lower part of the Rhine Basin and on 15th July for the Meuse River basin in order to provide timely flood observations to the civil protection authorities. All mapping products can be found at this link: https://emergency.copernicus.eu/mapping/ems/copernicus-emergency-management-service-forecasts-notifies-and-monitors-devastating-floods

What is the cooperation with national meteorological services like?

Cooperation with national meteorological, hydrological, or other authorities responsible for flood forecasting in their region is fundamental for EFAS. On the one hand, many of those authorities provide the required in-situ data for EFAS and, on the other hand, EFAS aims to support those authorities with its complementary flood forecast information. To ensure good cooperation a partnership agreement is established between the authorities that are interested in EFAS (see here: https://www.efas.eu/en/collaborate). The JRC organises annual meetings with the EFAS partners to discuss the latest system updates or feedback from the national authorities on the EFAS forecasts. Furthermore, EFAS partners are encouraged to send regular feedback on EFAS notifications and EFAS forecasts in general.

What is the role of the European Centre for Medium-Range Weather Forecasts (ECMWF)?

The European Centre for Medium-Range Weather Forecasts (ECMWF), implements the Copernicus Atmosphere Monitoring Service (CAMS) and the Copernicus Climate Change Service (C3S), along with some components of the Copernicus Emergency Management Service (CEMS).
The European Flood Awareness System (EFAS), jointly developed by the European Commission and the European Centre for Medium-Range Weather Forecasts (ECMWF), is a hydrological forecast and monitoring system independent of administrative and political boundaries in the greater European domain. The aim of EFAS is to support preparatory measures before major flood events strike, particularly in the large trans-national river basins and throughout Europe in general. EFAS is the first operational European system monitoring and forecasting floods across Europe and is a component of the Copernicus Emergency Management Service, which is implemented by the Joint Research Centre (JRC). The role of the ECMWF is as Computational Centre (COMP) only.

There were reports that member states acted quite slowly on the early warnings? Who is the "client" to EFAS and how can they access data & warnings?

EFAS monitors the flood situation but does not monitor actions taken by national authorities based on EFAS flood forecast information or national warning system information, as such actions fall outside EU competence.

EFAS does also not send warnings but EFAS notifications that aim at providing complementary forecast information to the relevant national authorities. EFAS notifications are not aimed at warning the public as the notifications contain expert information that should be combined with the relevant available national and local information to provide the best possible basis for decision making. The relevant national authority may or may not use the provided EFAS forecast information, and is likely to also take into account other information in deciding on any measures to be taken.

EFAS partners have access to all EFAS forecast information. A full list of EFAS partners can be found here: https://www.efas.eu/en/partners-list-0

For additional information please also have a look at the Frequently Asked Questions on EFAS and the information EFAS provided during the flood events affecting the Rhine and Meuse river basins, which are published on the EFAS website under the following link: https://www.efas.eu/en/news/faq-efas-and-recent-flood-events

What kind of notifications do you send and how should authorities use them?

EFAS flood notifications contain an indication of the potentially affected larger region or river/tributary section and very short and basic information on the predicted probabilities to exceed a certain flood return period. Furthermore, there is an advisory message to follow a link to access the more detailed, regularly updated flood forecast information displayed in the EFAS web portal.

An overview of EFAS flood notifications is available in the monthly overview (https://www.efas.eu/en/notifications?field_month_value=05&field_year_value=2022). Furthermore, in the bi-monthly published bulletins an overview of all flood notifications indicating the river section or region, the lead time, the forecast date and the main affected country can be found in the Appendix.

EFAS notifications are not aimed at warning the public as the notifications contain expert information that should be combined with the relevant available national and local information to provide the best possible basis for decision-making.

For this reason and to respect the national mandate for warnings, EFAS Flood notifications and other related forecast information cannot be shared publicly unless the relevant national authority decides to share the information.

What are the usual next steps after EFAS has sent a flood notification?

Once an EFAS notification has been received, the relevant national authority is advised to connect to the EFAS map viewer for more detailed forecast information, and to analyse the situation together with the available national or local early warning information, to decide on the next actions.

Who receives EFAS flood notifications?

EFAS flood notifications are sent out to all the “EFAS partners” (see here for a list of EFAS partners: https://www.efas.eu/en/partners-list-0) in the potentially affected river basin and the European Response and Coordination Centre (ERCC), the heart of the EU Civil Protection Mechanism, in order to create early awareness on the high risk of flooding in the coming days. An ‘EFAS partner’ is any national, regional or local authority with a legal obligation to provide flood forecasting services or that has an institutional mandate in flood risk management within its territory.  In the case of transnational river basins, EFAS notifications are also shared with national authorities that might not be immediately affected by the forecasted flood (e.g. EFAS notifications for the German section of the Rhine are always also shared with the relevant Dutch and Belgian authorities). EFAS notifications related to flash floods are only sent to the relevant national or regional authority. 

Are EFAS flood notifications available to the public?

EFAS notifications are not aimed at warning the public as the notifications contain expert information that should be combined with the relevant available national and local information to provide the best possible basis for decision making.

To respect the national competence for warnings and the single-one-voice warning principle, EFAS Flood notifications and other related forecast information cannot be shared publicly unless the relevant national authority decides to share the information.

Archived EFAS forecast data including an overview of EFAS flood notifications (e.g. https://www.efas.eu/en/notifications?field_month_value=05&field_year_value=2021) and a list of all flood notifications indicating the river section or region, the lead time, the forecast date and the main affected country are publicly available after 30 days. (example: https://www.efas.eu/sites/default/files/efasBulletins/2021/EFAS_Bimonthly_Bulletin_Apr_May2021_0.pdf

Are EFAS Flood Notifications without any obligation?

Yes. EFAS notifications aim at providing complementary forecast information. The relevant national authority may or may not use the provided forecast information, and is likely to also take into account other information in deciding on any measures to be taken. 

Does EFAS monitor what is being done after the notification has been issued?

EFAS monitors the flood situation but does not monitor actions taken by national authorities based on EFAS flood forecast information or national warning system information, as such actions fall outside EU competence. 

Does EFAS request acknowledgement of receipt from the relevant authorities once a notification has been received?

Partners who receive an EFAS Flood notification are not requested to send an acknowledgement of receipt. In a flood situation, forecasting and emergency response authorities are extremely busy with processing and integrating all relevant information coming from a variety of sources and usually only reply to notifications if further questions arise. Regular feedback on EFAS flood notifications is requested in the aftermath of an event to continuously adapt and improve the system. 

Does EFAS forecast floods only for large rivers?

EFAS aims at predicting floods for large rivers and their tributaries but provides as well flash flood predictions for smaller-scale rivers. In the case of the Meuse and Rhine river flood events both, predictions for the large-scale river sections of the Rhine and Meuse as well as the flash flood predictions for many of the small-scale tributaries of these river basins indicated a high probability of flooding or flash flooding, respectively. 

Are EFAS forecasts precise and reliable?

EFAS does not make any claims as to the completeness of the information provided. On the contrary, EFAS forecasts are complementary to national warning and information systems, and it is the competence of national or regional/local competent authorities to draw the necessary conclusions from all available information.

EFAS is a European-scale forecasting system that aims to provide additional forecast information at a larger scale (river basin-wide, European scale) including flash floods and with longer forecast horizons than most national systems to raise early awareness about the risk of flooding. The reliability of EFAS forecasts is assessed using a number of different technical skill scores that are published and available on the website and the map viewer.

Who is responsible for preventing, preparing and responding to natural and man-made disasters in EU Member States?

Art. 8 (c) of Regulation 2021/836 amending Decision No 1313/2013/EU on a Union Civil Protection Mechanism (UCPM) has attributed a mandate to the European Commission in the field of EWS to complement and support the work of the Member States developing, e.g. transnational detection and early warning systems, such as the European Flood Awareness System, mainly for transboundary floods.

What does a 3°C world mean for flood catastrophes – like in Germany in 2021? Were you surprised by the severity of that?

Catastrophic floods like those that occurred in Western Europe are rare. In some areas, the magnitude of the rainfall and river flows recorded occur once every 100 years or even less frequently (https://en.wikipedia.org/wiki/2021_European_floods ). In the days before, both European- and national-scale weather forecast systems were predicting heavy rainfall over the Rhine and Meuse River basins, so severe flood waves were expected (https://www.efas.eu/en/news/faq-efas-and-recent-flood-events ). Yet, predicting the actual consequences of a flood event is more complex, because they depend on various factors.

Our study dated 2018 (https://www.nature.com/articles/s41558-018-0257-z ) focused on evaluating average flood impacts over long periods (30 years), rather than the impact of single events, but the possibility of catastrophic floods is taken into account to a certain extent.

What is the most important message to get when considering flood risks in a 3°C world for Western Europe/the rest of the world?

According to our study dated 2018 (https://www.nature.com/articles/s41558-018-0257-z and other studies too), a 3°C world will likely see large increases in flood risks in most global regions and especially in sub-Saharan Africa and Asia, driven by climate change and socio-economic growth.

Western Europe is one of the regions where flood risk could increase more: future economic losses and population exposed to floods could become more than three times bigger than present values. To reduce these impacts, societies will have to adapt to future flood conditions, for instance, by reducing flood peaks through the restoration of river floodplains and limiting development in flood-prone areas (https://ec.europa.eu/jrc/en/peseta-iv/river-floods )

How do the climate crisis and a 3°C world influence flooding in Western Europe and/or other regions?

For Western Europe, research studies predict more frequent and intense heavy rainfall events (https://doi.org/10.1002/2016EF000485), because under a three-degree warmer world this region could be hit more frequently by large storms resembling tropical cyclones. This will cause an increase in the frequency of both riverine floods and flash floods, meaning that rare, catastrophic events are likely to happen more often.

What are the components of large-scale catastrophic floods like those we saw in 2021?

Large-scale catastrophic floods are often a mixture of riverine and flash flooding (As seen during the recent floods in Western Europe), and therefore flood impacts in the future can be even more severe in some areas than was predicted by research studies. Flash floods are sudden flood waves occurring in small steep rivers after heavy rainfalls. Also, hazards such as landslides and heavy erosion of river banks can often increase the damage potential of flash floods were not examined.

On the map, I saw that there is a relative increase of 300% for the population exposed to floods in Western Europe. However, I could not see how that translates in absolute terms. Can you tell me more about that?

According to a recent study focused on Europe (https://ec.europa.eu/jrc/en/peseta-iv/river-floods), the population annually exposed to floods in Germany could grow from around 30 000 people as of today, to more than 90 000 by the end of the century. The same study estimates that almost 500 000 people could be exposed to river flooding every year in the European Union and the UK in 2100, almost three times the present values (170,000 people).

Is EFAS data suitable to assess which areas have been flooded after a flooding event took place?

EFAS is providing the flood forecast for the next 10 days including the estimate of the possible flood extent. Monitoring of the flood extent during and after the event, including the damage assessment, is provided by Copernicus Rapid Mapping Service.

What is the methodology to detect flooded areas and create maps?

Copernicus Rapid Mapping uses satellite imagery and other geospatial data to produce a set of standardized mapping products (https://emergency.copernicus.eu/mapping/ems/rapid-mapping-portfolio) including the flood delineation in the early hours after the event.

The flood delineation product is directly derived from satellite images acquired as soon as possible after the emergency event and consists of an observed water extent.

Depending on the complexity of the situation and the extent of the event, the analysis is made using computer-assisted visual interpretation or using semi-automatic extraction methods (supervised classification).

Can you estimate the error bars - the divergence between EFAS results and actually flooded area?

All Copernicus Rapid Mapping products are passing quality control measures described in detail here: https://emergency.copernicus.eu/mapping/ems/quality-control. The accuracy of the flood extent estimation is NOT being made readily available to a generic user.

EFAS performance is regularly evaluated and summarized in the EFAS verification pages https://www.efas.eu/en/forecast-skill

But for clarification, EFAS is an Early Warning system and provides an estimate of the possible flood extent based on the latest forecast data.

This estimate is not accounting for local flow control structures and flood protection measures.

The production of the observed flood extent maps is handled by the Rapid Mapping component of the On-demand mapping service: https://emergency.copernicus.eu/mapping/ems/service-overview

This service is based on the acquisition, processing, and analysis, in rapid mode, of satellite imagery and other geospatial raster and vector data sources, in order to provide information within 24h of a request. It supports emergency response in the immediate aftermath of a disaster.

Is EFAS data suitable to assess which areas have been flooded after a flooding event took place?

EFAS provides the flood forecast for the next 10 days, including the estimate of the possible flood extent.

Monitoring of the flood extent during and after the event, including the damage assessment, is provided by Copernicus Rapid Mapping Service.

Detailed information about both EFAS and Rapid Mapping information produced for the flood events in Germany and Belgium can be found here: https://emergency.copernicus.eu/mapping/ems/copernicus-emergency-management-service-forecasts-notifies-and-monitors-devastating-floods

Rapid Mapping activation for the Meuse River in BE, DE, NL was done at a very early stage of the flooding following a Rapid Mapping pre-tasking request issued to Belgium Authorities based on EFAS forecasts.

Why are my requests in a 'running' or 'pending' state for a long time?

The Climate Data Store is used daily by thousands of users requesting and processing data. It is possible that sometimes the system goes under stress.

CEMS-flood datasets are archived in MARS (Meteorological Archival and Retrieval System). Every Wednesday there is a MARS system session, that can affect request queuing time.

More information in CDS - Best Practices.

How do I spatially subset the dataset?

You can subset/ crop EFAS data when using the 'Download data' form on the CDS. See CDS - How to Download for details.

You can also use the CDS API to retrieve the entire EFAS domain of data and perform the cropping operation locally. See Extract subset of CEMS-Flood Data for details.

How do I spatially subset the dataset?

Why are latitude and longitude coordinates multiples of 0.05?

In the GRIB format, the data field is represented by a grid of points. 

GloFAS datasets have a spatial resolution of 0.1x0.1 degrees.

The points coordinates, multiple of 0.05 and spaced by 0.1 degrees, represent the centre of a cell of 0.1x0.1 degrees.

Why does the GRIB format have longitude ranges between 180 and 540?

The GRIB format does not allow negative values for the specification of the longitude coordinates. Up to GloFAS 3.X versions, this issue is solved by adding 360 to the longitude range (e.g. 180 = -180 + 360, and 540 = 180 + 360). As this definition of the coordinates does not adhere to the GRIB standard (i.e. longitude values cannot be above 360), the longitude ranges are updated with 180.025 to 179.975 for GloFAS versions 4.0 and above.

In either case, when reading GRIB messages with the Python Xarray/CFGRIB converter or when decoding the messages using eccodes, the tools automatically convert the range back to -180 to 180.