Use case: cities and regions

Mapping flood risk and early warning

Satellites help before and during a flood. Before, archived flood extents and maps of sealed ground can add to the flood hazard and risk maps that EU member states must keep. During an event, radar satellites map the water through cloud, day and night, and the European Flood Awareness System gives authorities flood forecasts up to ten days ahead.

Reference
UC-02
Technologies
  • Earth observation
Industry
Challenge
Flooding and natural hazards
Updated
Published by
LETO SPACE

01Technology

How it works

Satellite data supports three tasks that use different services: mapping the risk before a flood, forecasting a flood, and mapping the water while it is there.

Risk maps before a flood

EU member states keep flood hazard and flood risk maps for scenarios of low, medium and, where appropriate, high probability, showing the flood extent and the water depth or level, and review them every six years Source: European Union, EUR-Lex, 23 October 2007European Union, EUR-LexDirective 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks23 October 2007Open source (opens eur-lex.europa.eu). Satellite data can add to these maps. Flood extents from the Sentinel-1 archive reach back to 2015 Source: IEEE JSTARS, Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930, 2023Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930Estimating Ensemble Likelihoods for the Sentinel-1-Based Global Flood Monitoring Product of the Copernicus Emergency Management Service2023Open source (opens doi.org), and maps of sealed ground show where rainwater can no longer soak away Source: Copernicus, land.copernicus.eu, accessed 4 October 2026land.copernicus.euCopernicus Land Monitoring Service: High Resolution Layer Imperviousnessaccessed 4 October 2026Open source (opens land.copernicus.eu). Combined with digital terrain models, flood maps become more accurate and allow water depths to be estimated Source: UN-SPIDER (United Nations Office for Outer Space Affairs), accessed 6 October 2026UN-SPIDER (United Nations Office for Outer Space Affairs)Recommended Practice: Flood Mapping with Sentinel-1 and Sentinel-2 Imagery and Digital Terrain Modelsaccessed 6 October 2026Open source (opens un-spider.org).

Forecasts and early warning

The European Flood Awareness System (EFAS), part of the Copernicus Emergency Management Service, combines satellite data, weather and hydrological models and historical records. It gives probabilistic flood forecasts with lead times of up to ten days and notifies its partners, which include national, regional and local authorities. EFAS complements national and regional forecasting systems; it does not replace them Source: EU Space Programme (Copernicus Observer), 29 January 2025EU Space Programme (Copernicus Observer)Observer: How the EU Space Programme supports flood preparedness, the role of the European Flood Awareness System (EFAS)29 January 2025Open source (opens eu-space.europa.eu).

Mapping the water during a flood

Radar satellites such as Sentinel-1 deliver images in all weather, by day and night Source: European Space Agency (ESA), accessed 6 October 2026European Space Agency (ESA)Sentinel-1accessed 6 October 2026Open source (opens esa.int), so cloud does not block the view. The Global Flood Monitoring product maps the flood extent automatically from each new Sentinel-1 image Source: IEEE JSTARS, Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930, 2023Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930Estimating Ensemble Likelihoods for the Sentinel-1-Based Global Flood Monitoring Product of the Copernicus Emergency Management Service2023Open source (opens doi.org). For detailed maps of a specific event, authorised users can request the on-demand mapping of the Copernicus Emergency Management Service, free of charge Source: Copernicus EMS, Copernicus Emergency Management Service, accessed 7 October 2026Copernicus Emergency Management ServiceAbout the Copernicus EMS On-Demand Mapping serviceaccessed 7 October 2026Open source (opens mapping.emergency.copernicus.eu).

  • L1 Base mapTerrain, river and parcels
  • L2 FloodingAreas at risk along the river
Illustrative map, not real data. Areas at risk of flooding along the river, as a risk map would show them.

02Deliverables

What you get

Flood data supports planning, preparation and response, each at its own pace.

  • Flood extent maps for past events and for an ongoing flood, as layers for your GIS.
  • A flood history of your area from the Sentinel-1 archive, to check where water has actually stood.
  • Sealing maps that show where heavy rain cannot soak away, as an input for drainage and heavy-rain planning.
  • Forecast information through EFAS for the authorities that are its partners.
  • Rapid damage maps after an event, when an authorised user activates the Copernicus Emergency Management Service for your area.

03Limits

Limits

EFAS forecasts and notifications go to its partner authorities first and become public only after a 30-day embargo Source: EU Space Programme (Copernicus Observer), 29 January 2025EU Space Programme (Copernicus Observer)Observer: How the EU Space Programme supports flood preparedness, the role of the European Flood Awareness System (EFAS)29 January 2025Open source (opens eu-space.europa.eu).

04Use cases

05Next steps

Find providers and get started

Beyond the free Copernicus services, providers offer flood models, risk maps and monitoring services. The Spacegraph marketplace has a category for flood mapping and modelling.

Whether you add a commercial service to the free ones depends on the detail, the speed and the format you need. We help you write those requirements so that providers can answer them, and compare the offers you receive.

Requirements and procurement

Frequently asked questions

Q1Which satellite data is used for flood mapping, and how quickly is it available?

Radar data from Sentinel-1 is well suited, because the radar sees through cloud by day and night Source: European Space Agency (ESA), accessed 6 October 2026European Space Agency (ESA)Sentinel-1accessed 6 October 2026Open source (opens esa.int). The Global Flood Monitoring product of the Copernicus Emergency Management Service derives a flood extent map from each new Sentinel-1 image automatically, in near real time, and holds flood information back to 2015 Source: IEEE JSTARS, Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930, 2023Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930Estimating Ensemble Likelihoods for the Sentinel-1-Based Global Flood Monitoring Product of the Copernicus Emergency Management Service2023Open source (opens doi.org). A new image exists only when a satellite passes over the area.

Q2Can a city request satellite maps during a flood?

Only through an authorised user. The on-demand mapping of the Copernicus Emergency Management Service is free of charge and can be activated only by designated authorised users Source: Copernicus EMS, Copernicus Emergency Management Service, accessed 7 October 2026Copernicus Emergency Management ServiceAbout the Copernicus EMS On-Demand Mapping serviceaccessed 7 October 2026Open source (opens mapping.emergency.copernicus.eu). Who they are and how a request works are explained in the use case on rapid damage mapping.

Q3How do we start a pilot for flood risk mapping?

Start with the decision the map should support: an emergency plan, land use planning, the protection of a specific asset or heavy-rain planning. Collect what already exists, such as the official hazard maps, local terrain data and records of past events, and test which satellite products add information to it.

Sources (7)

  1. European Union, EUR-Lex, 23 October 2007Directive 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks (opens eur-lex.europa.eu)
  2. EU Space Programme (Copernicus Observer), 29 January 2025Observer: How the EU Space Programme supports flood preparedness, the role of the European Flood Awareness System (EFAS) (opens eu-space.europa.eu)
  3. European Space Agency (ESA), accessed 6 October 2026Sentinel-1 (opens esa.int)
  4. Krullikowski et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 6917-6930, 2023Estimating Ensemble Likelihoods for the Sentinel-1-Based Global Flood Monitoring Product of the Copernicus Emergency Management Service (opens doi.org)
  5. Copernicus Emergency Management Service, accessed 7 October 2026About the Copernicus EMS On-Demand Mapping service (opens mapping.emergency.copernicus.eu)
  6. UN-SPIDER (United Nations Office for Outer Space Affairs), accessed 6 October 2026Recommended Practice: Flood Mapping with Sentinel-1 and Sentinel-2 Imagery and Digital Terrain Models (opens un-spider.org)
  7. land.copernicus.eu, accessed 4 October 2026Copernicus Land Monitoring Service: High Resolution Layer Imperviousness (opens land.copernicus.eu)

Contact

Which areas do you need to check for flood risk, and for which decision?

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