Skredfaresone (landslide hazard zone)
A skredfaresone is an area where there is a risk of landslides, meaning masses in motion: snow avalanches, soil slides, debris flows, rockfall or clay slides. The zones are grouped by probability into three safety classes, S1, S2 and S3, under TEK17 § 7-3. The legal basis lies in the Planning and Building Act and the regulation's requirement that development must not be placed where it is exposed to danger. The data comes from NVE, which manages landslide mapping in Norway.
The safety classes reflect both the potential for damage and the probability level the development must withstand. S1 covers buildings where few people spend time, such as garages, boathouses and outbuildings, with a requirement for protection against landslides with a 1/100 annual probability. S2 covers detached houses, smaller residential buildings, offices and commercial buildings, where several people are normally present, with a requirement for protection against 1/1000 per year. S3 covers hospitals, schools, kindergartens and other critical infrastructure, with a requirement for protection against 1/5000 per year. Development inside a zone without documented protection to the level of its class is rejected in the building application, and an expert assessment (geotechnical engineer, avalanche specialist) is required as documentation.
The landslide types have different dynamics and are mapped in different series. NVE's aktsomhetskart (susceptibility maps) cover large areas at coarse resolution and act as a first line of warning: if the plot point falls inside the zone, an expert assessment must clarify the actual risk before permission is granted. Detailed hazard zone maps exist for selected built-up areas and areas with a known landslide history, where the probability limits are set by modelling. For quick clay there are separate quick clay hazard zones, classified under NVE-veileder 1/2019 (low, moderate, high, very high hazard level), with a requirement for geotechnical surveys under NADAG when work is carried out.
Climate change increases landslide risk through more extreme rainfall and less stable snow conditions. NVE's climate allowance for landslides is of the same order of magnitude as for flooding, but the practical effects are seen above all in debris flows (soil masses in water-saturated flood conditions) in steep side valleys. Susceptibility maps are updated regularly, and municipal hazard zone maps are typically revised as part of updates to the land use element of the municipal master plan.
The consequences for developers and owners are concrete. Inside zones S1 to S3, you need documented protection or placement outside the zone before permission is granted. Protection structures can be physical (landslide barriers, catch fences, protective netting, terrain reshaping), limiting (moving the building, reduced volume) or land use based (only low-risk use on the exposed part of the plot). Existing buildings are not automatically subject to an upgrade requirement, but in serious cases the municipality can expropriate or use a hensynssone (zone requiring special consideration) in the zoning plan to prevent further development. Insurance follows the natural perils scheme through Norsk Naturskadepool, but repeated events without remedial work can reduce cover.
The difference from a flood zone is the type of hazard: flooding is water masses from watercourses or the sea, while a landslide is mass movement on sloping terrain. The difference from the building line along watercourses under section 1-8 of the Planning and Building Act is that the building line is a land use restriction independent of geohazards, while the landslide hazard zone is a geohazard assessment. An area can fall under several instruments at the same time.
In Placepoint, NVE's susceptibility maps for landslides, quick clay hazard zones and debris flows are shown as map layers. The example Climate risk and ground conditions shows the flow for assessing landslides together with NADAG data and matrikkel information at a plot point.
How the dataset appears on the map
The dataset is part of the map layer Geology as Landslides:
From Placepoint's dictionary: Skredfaresone
More information: NVE: Flom og skred, DiBK: TEK17 § 7-3
English: Landslide hazard zone.
Frequently asked questions
Which landslide types are mapped?
Snow avalanches, soil slides, debris flows, rockfall, rock avalanches and quick clay. NVE manages both susceptibility maps (coarse resolution) and detailed hazard zone maps (selected areas).
What are S1, S2 and S3?
Safety classes in TEK17 § 7-3. S1 covers buildings where few people spend time (probability 1/100), S2 covers homes and commercial buildings (1/1000), and S3 covers critical buildings such as hospitals and schools (1/5000).
Can I build in a landslide hazard zone?
Yes, but the building application must document protection to the level of the relevant safety class, either through physical protection structures or placement outside the zone. An expert assessment is required.
What is the difference between susceptibility maps and hazard zone maps?
Susceptibility maps cover large areas at coarse resolution and indicate that the risk must be assessed. Hazard zone maps are detailed calculations for selected areas with specific probability limits.
What about quick clay?
Quick clay hazard zones are a separate category, classified from low to very high hazard level. Work inside a zone requires geotechnical surveys under NADAG and an expert assessment.