Flood, landslide, earthquake: checking an address in Austria for natural hazards

You can check before you buy whether an address is at risk from floods, debris flows, avalanches, landslides or earthquakes. Three things decide it: whether the address lies in a flood area (HQ30, HQ100 or HQ300), whether it lies in a red or yellow hazard zone, and whether landslides have been recorded nearby. Heavy rain, on the other hand, can flood a cellar almost anywhere.

Floods: what HQ30, HQ100 and HQ300 mean

Flood maps show which land is under water in a flood of a given size:

• HQ30: a flood that occurs statistically once in 30 years.
• HQ100: once in 100 years.
• HQ300: once in 300 years, a rare extreme event.

"Once in 100 years" sounds reassuring, but it isn't: the chance is 1 percent in every single year. Over the 30 years of a mortgage, an address in the HQ100 area has a chance of about 26 percent of seeing at least one such flood. The floods in Lower Austria in September 2024 showed how far the water can reach.

Hazard zones: red and yellow

Hazard zone plans cover torrents, avalanches and the larger rivers. They mainly distinguish two zones:

• Red zone: the danger is so great that permanent residential use is impossible or only possible at disproportionate cost. New building land is generally not zoned here.
• Yellow zone: the danger is lower. Building is allowed, with conditions such as raised entrances or reinforced walls.

On top of that come advisory areas, for example for rockfall and landslides. Hazard zone plans are held at the municipal office, and many federal states also show them in their map portals.

Landslides

Landslides happen mainly on slopes with clay-rich ground that reacts to water, such as the flysch zone of the Vienna Woods or the hills of Styria. After long rain, a slope can start to move and damage houses. Austria keeps a register of recorded landslides. If a house stands on a slope, look for cracks in the walls, leaning fences or retaining walls that tilt.

Earthquakes

Austria has a moderate earthquake hazard. Earthquakes people can feel happen every year; damage is rare. The most active areas are the Vienna Basin, the Mürz valley and the Inn valley. New buildings must follow standards that account for earthquake loads. In an old, unreinforced house in these regions, check the chimneys, gables and floors.

Heavy rain: the risk far from any river

Flood maps show rivers and streams. Heavy rain can flood cellars where there's no water for miles: when water runs off a slope or a road towards the house, or the sewer backs up. At a viewing, ask whether the cellar has ever been wet, whether there's a backflow valve, and which way the ground around the house slopes.

What it means for insurance and buying

• Insurance: household and home insurance usually covers floods only up to a capped amount. Ask for the exact figure. In high-risk locations, higher cover can be expensive or unavailable.
• Disaster fund: after a flood, the federal and state governments pay grants (Katastrophenfonds), but they cover only part of the damage.
• Buying: a location in the red zone or the HQ30 area affects the price, the insurance and the mortgage. Check it before you make an offer.

How to check an address

1. Look at the HQ30, HQ100 and HQ300 flood areas for the address.
2. Ask the municipality for the hazard zone plan.
3. If the house stands on a slope, check whether landslides are recorded nearby.
4. Ask the seller and the neighbours about past damage.

Wohnprobe shows all of it at once: the report on an address lists flood areas, hazard zones, landslides and earthquake hazard under "Safety & risk", each for the address itself.