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Floods

Flood is a condition in which areas that are normally dry are inundated by water.

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Zu Hochwasser (hoher Wasserstand von Gewässern) und Überschwemmungen (Gewässer treten über die Ufer) kommt es unter anderem, wenn Seen sowie Bäche und Flüsse viel Wasser führen, wenn nach starkem Niederschlag (Regen, Schnee) und / oder starker Schneeschmelze viel Wasser abfliesst oder wenn mehr Grundwasser als üblich an die Erdoberfläche stösst (z. B. Quellen).

Seehochwasser dauern meist lange an, haben in der Regel jedoch weniger direkte Zerstörungskraft als Bachaustritte. Diese weisen meist sehr hohe Fliessgeschwindigkeiten auf und können so in kürzester Zeit enormen Schaden anrichten.

Description of measured and forecast values

The discharge in the river is below an event occurring once every two years on average. This threshold value is based on both statistical data and experience of how the rivers behave.

Rivers below HQ2 (or adjusted threshold)

Lakes below MSA** 1/3 (FS* + MSA**)

* Flood stage

** Maximum seasonal average

Effects

Transport disruption and damage are not normally to be expected.

Behaviour

It is not dangerous to remain near rivers, but vigilance is required at all times.

Description of measured and forecast values

The discharge in the river is within the range of an event occurring once every 2 to 10 years on average (HQ2, HQ10). These threshold values are based on both statistical data and experience of how the rivers behave.

The lake level lies between the maximum seasonal average and the flood stage.

Rivers above HQ 2 (or adjusted threshold)

Lakes above MSA** +1/3 (FS* + MSA**)

* Flood stage

** Maximum seasonal average

Effects

At this discharge level, local occurrences of rivers bursting their banks and flooding are unlikely, but cannot be ruled out. In exceptional cases, local flooding of underpasses, underground car parks and basements is possible. Local occurrences of disruption on exposed transport routes and minor damage are unlikely, but cannot be ruled out.

Behaviour

It may be dangerous to remain near rivers. As a precaution, maintain a safe distance.

Monitor the situation and take initial precautions.

For further information go to General recommendations during a flood

Description of measured and forecast values

The discharge in the river is within the range of an event occurring once every 10 to 30 years on average (HQ10, HQ30). These threshold values are based on both statistical data and experience of how the rivers behave.

The lake level is below the flood stage.

Rivers above HQ10 (or adjusted threshold)

Lakes above MSA** +2/3 (FS* + MSA**)

* Flood stage

** Maximum seasonal average

Effects

At this discharge level rivers may burst their banks locally in exposed places and flooding may occur. Local flooding of underpasses, underground car parks and basements is possible. Local disruption may occur on exposed transport routes and minor local damage is to be expected.

Behaviour

It is dangerous to remain near rivers. Keep well away.

Monitor the situation and take the necessary precautions.

For further information go to General recommendations during a flood

Description of measured and forecast values

The discharge in the river is within the range of an event occurring once every 30 to 100 years on average (HQ30, HQ100). These threshold values are based on both statistical data and experience of how the rivers behave.

Rivers above HQ30 (or adjusted threshold)

Lakes above Flood stage

Effects

At this discharge level rivers are likely to burst their banks and flooding may occur. Buildings and infrastructure may be affected. Transport disruption is possible and damage is likely to occur.

Behaviour

It is extremely dangerous to remain near rivers. Keep well away.

Monitor the situation and take the necessary precautions.

For further information go to General recommendations during a flood

Description of measured and forecast values

The discharge in the river is within the range of an event occurring once every 100 years on average (HQ100). These threshold values areis not based solely on  statistical data, but may be adjusted based on experience of how the rivers behave.

Rivers above HQ100 (or adjusted threshold)

The lake level is above the range "Flood stage + 25 cm".

Lakes above FS* + 25 cm

* flood stage

Effects

At this discharge level rivers may burst their banks and flooding may occur in many places. Infrastructure of national importance, such as railways, villages and towns and industrial plants, may be significantly affected by floods. Significant transport disruption is likely in some cases. Some widespread major damage is to be expected.

Behaviour

It is extremely dangerous to remain near rivers. Keep well away.

Monitor the situation and take the necessary precautions.

For further information go to General recommendations for action during a flood

Explanations (german)