How to tell if a house in Italy is in a flood zone

You look up the address on the flood maps that Italy's river basin authorities draw for rivers, streams and the sea, and that ISPRA (the Italian Institute for Environmental Protection and Research) combines for the whole country on its IdroGEO platform. If the house falls inside a flood-prone area, the map also says how often water can be expected. Only the plan of the river basin district authority, together with the rules of the Comune (the local council), gives an answer with legal value.

Frequent, less frequent and rare floods

The maps follow the three scenarios of the EU Floods Directive of 2007. In areas with frequent floods (P3) water arrives on average once every 20 to 50 years. In areas with less frequent floods (P2) the average rises to once every 100 to 200 years, while areas with rare floods (P1) need extreme events. In the report the same levels become high, medium and low flood risk, with the code alongside.

The three areas sit one inside the other, because a rare flood covers more ground than a frequent one. A house in a P3 area is almost always in P2 and P1 as well; a house "only in P1" is outside the two most exposed areas. And the frequency is still an average: a P2 area has no fixed turn, it can flood twice in a few years and then stay dry for a long time.

The national map also has some gaps. In the Marche region the 2020 version does not contain the P3 areas of the former regional basin authority, so there the absence of a frequent-flood area does not mean the hazard is absent. The table of levels and the differences between the maps are in the article Flood zones P1, P2 and P3 in Italy: what they mean.

Hazard and risk are not the same thing

The P level measures how likely it is that water reaches that spot: it is the flood hazard (pericolosità idraulica), and it describes the land. The river basin authorities' plans show risk separately, with levels R1 to R4, which also takes into account what is there: homes, roads, businesses, people.

For a buyer the difference is practical. In the same block of flats in a P3 area, a third-floor flat and a basement room below street level share the same hazard and face very different damage. The report works on the parcel and the building, never on a single flat: it tells you how exposed the location is, while the floor, the cellars and the height of the entrance need to be checked on site.

If the house is in a flood-prone area

Many lowland neighbourhoods and a good number of historic centres are in P2 areas, and that alone is no reason to rule them out. What changes are the questions to ask before making an offer.

Start at the bottom of the building. Cellars, garages, basement rooms and plant rooms are the first to take in water, together with boilers and electrical panels when they sit below street level. The height of the entrance above the pavement matters too: a few steps make a difference.

Then find out what has already happened. Ask the seller whether the flat, the cellar or the garage has ever flooded and how the damage was repaired, and ask the building manager whether the condominium has made claims for water damage. Neighbours often remember better than anyone, and local news from recent years tells you whether the street has already seen a flood.

Insurance is the third point: whether the condominium is insured, whether the cover includes floods and flooding, and with what excesses. Not every condominium policy does. Mortgages, home insurance and tax relief have their own guide: Buying a house in a flood zone in Italy: mortgage, insurance and questions to ask.

Last come the works done to keep water out, such as pumps that empty the basements, non-return valves that stop the sewers backing up and flood barriers fitted at the entrances. It is worth knowing who maintains them and whether they worked the last time it rained hard.

What the report tells you: the Rimini example

Type in the address: straight away and free of charge you see the liveability index of the area, which also takes landslides, flooding and earthquakes into account. With a critical natural risk the index does not go above 60 out of 100, however good the services and green spaces are.

In the full report flooding has its own section. It says whether the building's cadastral parcel falls in a P3, P2 or P1 area, how much of the parcel is affected and what lies in the surrounding 100 metres, with a map one kilometre across showing the flood-prone areas nearby. Another section works out what floods and earthquakes cost on average, in euros a year (how we calculate it), and a further one looks at landslides (How to tell if a house in Italy is at risk of landslides). At the end, the buying guide turns these data into questions for the seller, the building manager, the surveyor and the Comune.

A real case: a residential building in Via Castagnevizza, in Rimini, about 410 metres from the sea. The parcel is entirely in an area with frequent floods (P3) on ISPRA's national map, and the flooding section is critical. For a 100 square metre home the average damage ranges from 640 to 2,020 euros a year, almost all of it from water; the European river model has no water depth for that spot, so the calculation works between 20 centimetres and one metre. On landslides the same report is favourable: no hazard zone within the parcel or the 100 metres around it, and no recorded landslide within 500 metres. A summary of every topic is in the sample report.

Which maps are binding

The official flood areas are in two plans of the river basin district authority: the flood risk management plan (PGRA), updated every six years, and the hydrogeological plan (PAI), which also contains the rules on what can be built. The Comune adopts them in its planning documents and can add its own limits, for example on turning basement rooms into living space. In Lombardy, Veneto, the province of Bolzano and the metropolitan city of Turin the report also says what the municipal plan provides for the parcel (What can be built on a plot).

The report uses ISPRA's national combined map (mosaicatura), which brings the district maps together with a common method. It covers the whole of Italy, but it has no legal value and the flood version dates from 2020: after some recent events the river basin authorities have already updated their plans. When the report finds a flood-prone area on or near the parcel, the next step is to check the district plan or ask the technical office of the Comune.

There is also a practical limit. Flood areas describe water coming out of rivers, streams and the sea; in a violent storm a cellar can flood well away from these areas when the drains cannot cope. The question about past flooding is worth asking anyway.

The flood hazard levels quoted on this page come from ISPRA, Mosaicatura delle aree a pericolosità idraulica (v. 5.0 - 2020), IdroGEO, licensed under CC BY-SA 4.0: the Rimini figure derived from it is distributed under the same licence. How we use these maps: Landslides and flooding.

Frequently asked questions

Is flood insurance compulsory for a house in Italy?

For a household, as a rule, no. The obligation introduced by the 2024 budget law (legge 213/2023) applies to businesses entered in the companies register. People who want to protect their home usually add natural disaster cover to their fire policy, and 19% of the premium can be deducted from income tax: the details are in the guide on mortgages and insurance.

Should I worry if the house is only in a P1 area?

A P1 area floods in rare or extreme events, and a house only in P1 is outside the P2 and P3 areas. In this case the report asks the seller whether cellars, garages or nearby streets have ever flooded in heavy rain.

Does the report say whether the building has flooded before?

No. The maps show how likely water is at a location, not what has happened to a building. That is why, when the house is in a P3 or P2 area, the questions for the seller include past flooding and how the damage was repaired.

Is the national map enough to buy?

It is enough to know where to look. For an official check the binding sources are the river basin district authority's plan and the technical office of the Comune, which also know about updates made after 2020.