How do you find out whether a place is at risk of river flooding?

Horizon is a free app that reads satellite data to show whether a location sits inside a mapped river floodplain, with a 10 day outlook for heavy rain and storms. It works anywhere in the world.

Video: Introducing Horizon: free river-flood risk from global satellite data on YouTube

Why this matters

Flood risk information has historically been national, and where the national service is thin, the people most exposed have the least to go on. A globally available floodplain map and a 10 day outlook will not replace an official warning and must not be treated as one, but it does let a programme learn which of its sites sit in a floodplain before the rain rather than after it.

How to do it

  1. Open Horizon and search for the place you care about.
  2. Check whether it falls inside a mapped river floodplain.
  3. Follow the 10 day outlook for heavy rainfall and storms.
  4. Add every place you want to watch, so they appear together in one view.
  5. Always follow official local warnings and authorities, since Horizon is guidance only.

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