Awareness level for flood and landslide forecasting and warning

Red awareness level (4)

 

Extreme situation that occurs very rarely, requires immediate attention and may cause severe damages.

Flood: Return period of more than 50 years.

• Expected many landslide events, several with considerable consequences.
• Extensive flooding, erosional damage and flood damage to buildings and infrastructure.


 

Orange awareness level (3)

 

 

Severe situation that occurs rarely, requires contingency preparedness and may cause severe damages.

Flood: Return period of more than 5 years

• Expected many landslide events, some with considerable consequences.
• Extensive flooding, erosional damage and flood damage to certain prone areas.


 

Yellow awareness level (2)

 

 

Situation that requires vigilance and may cause local damages.

• Expected some landslide events, certain large events may occur.
• Local flooding and/or erosional damage due to rapid increase of discharge in streams/ small rivers, ice drift, ice in streams/rivers and frozen soil.
• High flow/water level in comparison to normal seasonal variations.
• Discharge close to orange level.


 

Green awareness level (1)

 

Generally safe conditions.

 


 

N.B.: The extent of damage relates to a combination of the vulnerability (i.e., infrastructure and other potential damage) in the warning area and the awareness level – not solely to the awareness level.

Actions and advice

  • Stay informed on the development of the weather and hydrological situation by following the weather forecast and weather radar, as well as updates on varsom.no.
  • Secure and/or move assets away from vulnerable areas (car, caravan along rivers/streams) and exposed areas (basements).
  • Keep waterways clear of snow and ice, sediments, garbage, twigs and leaves.
  • Keep away from rivers/streams with high flow and steep slopes.
  • Municipalities, Counties and other emergency operators should continuously evaluate the need for preparedness and prevention measures. Contingency response should be attentive that buildings, and infrastructure in general, may be exposed to severe damage both at orange and red awareness level; in some cases also at yellow awareness level.

 

Consequences

A flood warning indicates risk of flooding of rivers and lakes:

  • Flooding along lakes and rivers in relatively flat terrain / landscape.
  • Erosional damage along rivers, which may cause subversion and lead to rivers taking new courses

A landslide warning indicates risk of debris avalanches, debris floods and/or slush slides:  

  • Debris avalanches/shallow slides: Soil slides and rapid movement of saturated soil in steep terrain.

  • Debris flows: A flood of water, soil and rocks in steep creeks. Surface runoff in steep terrain can cause streams to change regular flow patterns.
  • Slush slides: A stream of waterlogged snow. These landslides can start in relatively flat terrain and seek towards streams and steep slopes.

  • In the case of issued landslide warnings, there is typically also an increased risk of water triggered rock falls.

Quick clay landslides and some mudslides are caused by processes that have very slow effective response or human activity, and are not included in landslide early warning.

A forecast for heavy rain (torrential rains) from the Meteorological Institute, developed in cooperation with NVE, indicates local and momentary risk of:

Surface runoff, storm water in urban areas, local flooding, local flash floods with erosional damage, debris flows and debris floods where the rainfall occurs.

In the case of issued both flood and landslide warnings, please note:

• The warnings can be valid for different areas even though they are issued for the same period.
• The warnings may have different durations even though they are issued for the same area.