How do you check the flood risk in Brussels?
Brussels Environment publishes a flood map (2025 version) with three probabilities: high (once in 25 years), medium (once in 100 years) and low (once in 1000 years). The map is for information and forbids nothing. A Brussels score like the Flemish P and G scores does not exist.
Four causes on one map
The 2025 map brings together what matters in a flood: heavy rain running off streets and gardens, a watercourse or the canal overflowing, sewers backing up and, for the first time, rising groundwater. Sewer backflow is only calculated for the high and medium probabilities, and not for every building.
Other things often matter on the same plot too, such as the Brussels soil certificate and crime figures by municipality. You can see how a report brings them together in the sample report.
The three probabilities
- high probability: on average once in 25 years;
- medium probability: on average once in 100 years;
- low probability: on average once in 1000 years.
Once in 100 years does not mean it stays dry for the next 99 years: it is a probability per year.
What the map is not
According to the terms of use of Brussels Environment, the map has no binding value and is for information only; on its own it has no consequences under the CoBAT or the insurance act. It shows a hazard, not a ban. Still, it tells you a lot: it shows where a cellar, a ground floor or a low garden can take in water.
What the seller declares
There is no Brussels information duty with a score, like the P and G scores in Flanders. In the notaries' model sale agreement for a property in Brussels, the seller does declare whether the property lies in a flood-prone area on the Brussels Environment map, and with which probability. Ask before you make an offer, and also ask whether the cellar has ever flooded: no map shows that.
What the Perceelscan says about it
The flood probability on the plot according to the 2025 map, whether groundwater is shallow there (less than about 2 m) and whether part of the plot lies in a no-build zone along a watercourse.
Must the seller disclose the flood risk in Brussels?
There is no Brussels rule like the Flemish information duty. The notaries' model sale agreement does have the seller declare whether the property lies in a flood-prone area on the Brussels Environment map.
In the other regions
- In Flanders: What do the P-score and the G-score mean?
- In Flanders: What is the water test (watertoets)?
- In Wallonia: What does the flood hazard map of Wallonia say?
Sources
- Brussels Environment: flooding
- Brussels Environment: terms of use of the flood map
- Notaris.be: the model sale agreement for a property in Brussels
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