Is the house in a landslide or flood hazard area?
You check it on ISPRA’s IdroGEO platform, which brings together the maps of the hydrogeological plans: for landslides the classes run from P4 (very high) to areas of attention, for floods the scenarios P3 (high probability), P2 (medium) and P1 (low). The maps with legal force are those of the district River Basin Authority.
The flood scenarios
| Scenario | What it means |
|---|---|
| P3 | frequent floods, return period of 20 to 50 years (high probability) |
| P2 | infrequent floods, return period of 100 to 200 years (medium probability) |
| P1 | low probability of floods or extreme event scenarios |
The scenarios are those of D.Lgs. 49/2010 (art. 6). ISPRA’s national flood mosaic is version 5.0 of 2020. The return period is a statistical measure: it does not mean that a flood happens only once in that period.
Other data often matter for the same property too, such as the municipality’s seismic zone and seismic zones by region. You can see how a dossier brings them together in the sample dossier.
Landslides
The landslide mosaic (version 5.0, 2024) distinguishes very high (P4), high (P3), medium (P2) and moderate (P1) hazard and areas of attention. Separately there is the landslide inventory (IFFI), which records landslides that occurred: on its own it does not establish which legal constraint applies.
These are not rare cases: in 2024, 23% of Italy’s territory had a landslide hazard class, and 94.5% of the municipalities are exposed to landslides, floods, avalanches or coastal erosion (ISPRA).
What they mean in law
ISPRA calls its mosaics a technical-scientific product. The rules that restrict building and works are in the River Basin Authority’s plans and the municipal plans: in some P3 and P4 areas the rules forbid new building or require opinions even for works on existing buildings.
What Dossier Immobile does
It queries IdroGEO for the selected location (indicative if estimated from neighbouring house numbers) and writes for each result what the map says, the general rules that may be relevant and which document has legal force; for the municipality, the municipality pages show the share of territory in each class.
Is a house in a P1 zone safe?
P1 means low probability, not no hazard. Where the house sits in the area and how it is built also matter.
The house is in no area: is it risk-free?
It means the current maps do not place it in a hazard area. The maps are updated, and the flood maps date from 2020.
Sources
- ISPRA, IdroGEO
- ISPRA, Hydrogeological instability in Italy, 2024 edition
- D.Lgs. 49/2010, art. 6
- IdroGEO: open data and licences
Dossier Immobile is a private service by SRI Group BV (VAT BE1037052239), not connected to any public authority: it brings together public data, with the source and date of every item.
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