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According to NVE, 60,000 people in Norway live in fast clay areas.
Clay rapid landslides are a type of area landslide, which is a collective term for landslides in soils with so-called brittle fracture properties.
A new house collapses here
* Rapid clay is basically solid and can withstand large vertical pressure, but if the clay is exposed to overload, the structure may collapse and the clay particles will float on the water – rapid clay landslides.
* Soil types with brittle fracture properties are mainly found in areas with marine deposits, land that was a seabed in the past. Loosely stored sand, silt masses in delta and river deposits can also exhibit brittle fracture behavior.
* Landslides generally start with a relatively small event, but develop into landslides that cover a large area.
There are two main causes: Natural causes such as excavation of streams and rivers (erosion) or human impact, such as excavation or mass movement.
– Like a bad horror movie.
* The 1978 landslide is one of the most famous clay rapid landslides. It was triggered when masses that had been excavated to make room for an extension were placed as a landfill in the beach area of Lake Botnen. The landfill caused a local overload, and this initial landslide spread to the sides and back and became a landslide in the area.
* Other known clay rapid landslides are Verdalsskredet in 1893, the Kattmarka landslide in 2009, Lyngen in 2010, and Byneset in Trondheim in 2011.
* Statistically, there will be several other types of landslides in case of more frequent and heavier rainfall, such as those related to snowmelt and spring thaw.
* There is no clear connection between increased rainfall and the danger of rapid clay slides, because rapid clay forms over a long period of time, hundreds to thousands of years. However, heavy rains can indirectly cause more landslides.
NVE has produced a map showing the fast clay areas in Norway. You can zoom in here.
