Quick clay

Quick clay is a specific type of marine clay that loses its bearing capacity completely when disturbed or loaded, and is the single factor in Norwegian geotechnics that most often stops or adds cost to development projects. The dataset is managed by Norges vassdrags- og energidirektorat (NVE), the Norwegian water resources and energy directorate, and combines two layers that were previously delivered separately.

Quick clay zones with hazard class and risk class

The first layer shows mapped zones with a potential hazard of large quick clay landslides, identified through Quaternary geological mapping and geotechnical assessment of topography, hydrology and coarse surveys. The zones are classified into three hazard classes, three consequence classes and five risk classes, where risk classes 4 and 5 are considered unacceptable and require specific measures. The zones cover both release areas (terrain that can slide out) and runout areas (terrain that can be hit by landslide masses). The dataset is primarily intended as decision support at municipal master plan level and as a warning to municipalities, landowners, developers and contractors to avoid terrain works and activities that can trigger a landslide.

Awareness map for quick clay

The second layer is a professionally based awareness area that shows where marine deposits with quick clay properties may be found, based on terrain criteria (difference in elevation and slope) and mapped superficial deposits. If a planned measure lies within the awareness area, you must follow the procedure in NVE-veileder 1/2019 and often obtain geotechnical expertise. The awareness layer replaces the former "Aktsomhet marin leire" (marine clay awareness) layer and now also captures terrain exposed to risk. Local surveys may show that the hazard is not real after all: exposed bedrock or better depth data can rule out quick clay in an area that is otherwise flagged.

Use in Placepoint

For a developer or a development department, the quick clay layer is a mandatory check at the zoning stage. Sites within a mapped zone trigger a requirement for a geotechnical stability assessment and often mitigating measures under TEK17, and can in the worst case make new development economically unjustifiable. For an estate agent and a valuer, it is a mandatory warning element in the sales prospectus and the valuation. The dataset is used in Placepoint's map layer for risk, and is often read together with Landslides, superficial deposits, marine limit and possibility of marine clay for a complete picture of the ground conditions.

Update frequency: Real time.