Flood disaster in Germany

Image source: tagesschau.de

The 2021 Ahr flood in Germany on July 14 and 15 destroyed vast areas of land, costing more than 7 billion euros and resulting in the deaths of at least 133 people.

Research objective

In this case study we want to take a look at the level of destruction from a satellite’s perspective. The Sentinel-2 polar orbiter provides data in 12 spectral bands at a spatial resolution of up to 10 meters and has a revisit time of five days.

Here, we will work with two Sentinel-2 observations, one from the overpass on June 13 (before the flooding) and one from July 21 (after the flooding) respectively. The scenes were chosen due to their low cloud cover.

Below you can see the true colour composites of a small extract from both scenes:

Additionally, a Digital Elevation Model (DEM) is provided:

We want to find out which areas were affected by the flood. How do we proceed?


Develop a conceptual approach for this task and discuss it in your group. Create a flowchart of all the steps necessary to implement your approach.

Ask yourself:

  • Do you have all the information you need to start implementing a solution?

  • Which problems might occur and how could you address these?

  • How can you estimate the accuracy of your results?