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Flood zones: what the map knows and the viewing does not

Spain has official flood mapping for almost every river and much of the coast. It says, parcel by parcel, how far the water reaches in the flood that comes every 10, 100 and 500 years. Insurers use it; banks use it; the buyer has almost never seen it.

The four zones

• T10: the 10-year return-period flood — what floods "often". Living inside it is living with the water.
• T100: the 100-year flood (1 % a year, which over a 30-year mortgage is 26 %). The reference for insurers and for use regulations.
• T500: the extraordinary one. Inside T500 but outside T100 the risk is low but not zero, and the 2024 Valencia DANA exceeded the T500 along several reaches.
• Preferential-flow zone (ZFP): where the water runs with force; the Hydraulic Public Domain regulation limits new buildings and vulnerable uses there.

The zones come from hydraulic models with data 5 to 15 years old; they do not include torrential rain over the city (pluvial flooding) except in some local maps.

Where to look

MITECO's SNCZI viewer covers all of Spain with the T10/T100/T500 extents and the ZFP; in the Basque Country, URA publishes its own mapping, more recent (2025) and more detailed; Catalonia (INUNCAT), the Valencia region (PATRICOVA, with the 2024 DANA map) and Andalusia (REDIAM) have their own viewers. Find the parcel, switch on the layers and measure the distance to the edge: 0 m is a finding, 40 m is attention.

What it implies

Inside T100: the insurer may raise the premium or exclude water damage (the Consorcio de Compensación de Seguros covers extraordinary flooding if you hold a policy, but not wear or exclusions); the bank may require a valuation with a note; an extension or change of use needs a report from the river-basin authority. Inside the ZFP: serious limits on building, basements, garages, new dwellings. Outside everything: the map says nothing — which is not the same as saying nothing happens.

What to ask

The seller: water claims in the last 10 years (the community of owners knows). The insurer: a quote with the exact address. The council, if you plan works: the basin authority's or URA's report. The garage: the water mark on the wall.

What the PropVer report does

It intersects the parcel outline with URA 2025 (Basque Country), the national SNCZI and the regional maps loaded, prints the distance to the edge of each zone and the source with its edition, and marks finding (inside), attention (within 50 m) or no findings in the layers consulted.

Updated 2026-10-23.