Floods August 2005 in Switzerland

Bern 2005

Armin PetrascheckFederal office for water and geology

Causes of the floods was heavy rainfall in central Switzerland

The rainfall caused extreme discharges in rivers of the densely populated regions

Damage Areas 2005

Vulnerability: Danger for lifeFlood Statistics of Switzerland

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Out of 64 causalities 23 inside the house 41 outside26 wrong behavior13 in the car9 camping

Aug. 2005 6 victimsAverage. 2 Victims/year

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Damage Cor. Inflation Sum Sum with inflation

Swiss Flood Damage StatisticAug. 20052500 Mio. CHF

Sept. 1868 (TI, GR, UR, VS)

Juni 1910 (Deutschschweiz)

Aug. 1987 (UR, TI, VS)

Sept. 1993 (Oberwallis)

Sept. 1993 (Tessin)

Aug 1997 (Sachseln)

Mai 1999 (Deutschschweiz

Okt. 2000 (Wallis)

Okt. 2000 (Tessin)

0 20 40 60 80 100 Schäden der öffentlichen Hand private Schäden

800480580

80200650

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2500August 2005

Comparison of damages

Private

Public

Type of ImpactStatic Flooding

Damage parameter: water depth

Large areas affected

Type of ImpactStatic Flooding

High damage potential because of numerous cases but low risk for live

Type of ImpactStatic Flooding

Related damages:Furniture, machineryWalls, especially if oil is involved

Type of ImpactStatic Flooding

Defence by emergency barriers

Type of ImpactDynamic FloodingDamage parameter:Velocity and depth

High danger for live

Type of ImpactDynamic Flooding

Wood, sand and stones are transported by the water

Type of ImpactDynamic Flooding

Damages are increased by the dynamic forces. The impact of floating debris or stones or the erosion of fundaments may damage the structure

Type of ImpactDynamic Flooding

Defence byLocating on high ground,Permanent barriers orPrepared solid mobile elements

During large flood events the river can start to meander.

22. August 2005

Type of ImpactRiver bank erosion

Type of ImpactRiver bank erosion

High damage: Leads to destruction

Defence: River training measuresDeep foundations

Type of ImpactSlides and mudflow

Damage parameter:Depth of slideVolume of movement

Type of ImpactSlides and mudflow

DamageIn many cases complete destruction of the house

Type of ImpactSlides and mudflow

DefenceFor deep slides stabilization measures for the slide must be applied

For mudflows a reinforced wall on the backside can give good protection. Sometimes even temporary walls can keep the mud away from the building.

Type of ImpactDebris Flow

Large mass movements with high velocitiesDamage parameter Hight of deposition

Type of ImpactDebris Flow

Damage

High dynamic impact can cause complete destruction

Keep space for the torrent

No reconstruction of destroyedbuildings

Type of ImpactDebris Flow

Defence

Strong retaining walls

Swiss strategy1. Knowledge of hazard

Hazard maps show degree and extend

Bsp. Steinibach NW

Swiss strategy

2. Space for the river

Space enables increase of discharge capacity and ecological improvement

HQ

embankmentriverbed-breadth

embankment margin. stripe

maintenance / bufferstripe

riverside

3m 1:2 3m1:2

Swiss strategy

3. Reducing damages

3.1 Maintenance of rivers and protection structures to keep present safety level

3.2 Spatial planning measures to avoid an increase of damage potential

• keep free high endangered areas (red)• adapted construction and local protection (permanent or mobile) in medium and low endangered areas (blue and yellow areas• restricted land use in areas necessary for retention and emergency measures

River space

Free space forextreme floods

Protection

Swiss strategy

3.3 Protection measures

Increase safety where required,Include all types of measures in your planning and consider extreme events

Emergencyplanning

Improving dikes

Swiss strategy

3.3 Protection measures

consider extreme events

Swiss strategy

4. Emergency Planning

Be prepared for the unexpected

5. InsuranceTo enable reconstruction if the damage occurs

FLOODS

If you do notfind the strongman, who stops the flood, …... You have to livewith floods