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Avalanche risk assessment in populated areas Aurlie Talon & - - PowerPoint PPT Presentation

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Urban Habitat Constructions under Catastrophic Events FINAL CONFERENCE. Naples, 16 th - 18 th September 2010 Avalanche risk assessment in populated areas Aurlie Talon & Jean-Pierre Muzeau PolytechClermont -Ferrand (CUST) - LaMI Blaise

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Urban Habitat Constructions under Catastrophic Events

FINAL CONFERENCE. Naples, 16th - 18th September 2010

Aurélie Talon & Jean-Pierre Muzeau

Polytech’Clermont-Ferrand (CUST) - LaMI Blaise Pascal University Clermont-Ferrand - France

Avalanche risk assessment in populated areas

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Context

Avalanche Persons Structures Infrastructures Communications Environment Economy Damages on issues caused by an avalanche

Hazard Issue Risk

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Starting Process Impacts on issue How to identify and to characterize? How to quantify and to mitigate? How to identify the consequence scenarios?

Hazard Issue Risk

Approach of Risk Analysis

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Scale of avalanche risk analysis System analysis : massif scale and slope scale Risk scenarios : slope scale Quantification of avalanche hazard Quantification of avalanche consequences Mitigation techniques Snowy coat forming Snowy coat properties Avalanche classification Avalanche characteristics and actions

Content of the presentation

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Snowy coat forming Stratification of snowy coat

  • Wind deposit
  • 1 cm / 10 minutes

Comparison: Loess 1 cm / century

Stratification variability

  • Temporal variability: hourly, daily (day, night or morning/afternoon),

weekly, annually, hundred years old, millenary

  • Spatial variability:

vertical or lateral centimeter, meter or decimeter

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  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Snowy coat properties

Mechanical properties of snow

Unit weight

20 kg/m3 for fresh snow 500 kg/m3 for old snow

Cohesion

8 to 35 kPa = 300 to 460 kg/m3 0 to 20 kPa < 300 kg/m3

Compression resistance

t=58.3 ( / ice)2.65

for plane faces and beakers

t=79.7 ( / ice)2.39

for other kinds of snow

Young Modulus

E=2642

2.826

(in kN/m2)

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Snowy coat properties Snowy coat properties: grain types

Crystal of fresh snow Fine grains Beakers Round grains

Pictures: courtesy of Météo France

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Snowy coat properties Sintering phenomenon of snow

Glass bridge Increasing of the cohesion but failure propagation due to the snowy coat rigidity

Anena

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Avalanche classification Three types of avalanches

  • Powder snow avalanche

air Incorporation of snow Avalanche front Snowy coat

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Avalanche risk assessment In populated areas

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Avalanche classification Three types of avalanches

  • Powder snow avalanche
  • Plate avalanche
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Avalanche risk assessment In populated areas

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Avalanche classification Three types of avalanches

  • Powder snow avalanche
  • Plate avalanche
  • Wet snow avalanche
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  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Avalanche classification

Avalanche sequence

Starting zone Track Runout zone Debris Slope breaking up

Accumulation basin Gorge Bouting

  • ut cone

Upstream Downstream Departure area Flow area

  • FT: traction strength
  • FR: resistance strength

When FT>FR: departure of the avalanche

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Avalanche classification

Morphological classification of avalanches

Area Criterion Distinctive characters Departure Departure type

  • Spontaneous departure: internal causes of snowy coat (spontaneous

avalanche)

  • Provoked departure: external causes of snowy coat (provoked avalanche)
  • non human (cornice, serac, animal, etc.)

human

  • involuntary (accidental avalanche)

voluntary (artificial avalanche) Departure shape

  • Punctual departure: avalanche starting from a point (departure with a pear

shape or a cone)

  • Linear departure: avalanche starting from a line (plate avalanche)

Snow quality Potentiality

  • f liquid

water

  • Null: dry snow avalanche
  • Poor: humid snow avalanche
  • Important: wet snow avalanche

Cohesion

  • Poor: pulverulent snow avalanche
  • Poor to moderate: crumbly plate (stretch) avalanche
  • Important: snow avalanche of hard plate

Type of snow

  • New: - non windswept: fresh snow or recognizable particles
  • windswept: recognizable particles or fine grains
  • Evolved: fine grains, plane faces, recognizable particles or round grains

Position of the sliding plane

  • In the layer of the snowy coat (surface avalanche)
  • On the soil (bottom avalanche)
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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Avalanche classification

Morphological classification of avalanches

Area Criterion Distinctive characters Flow Land shape

  • Open slope (side avalanche)
  • Lane or gorge (gorge avalanche)

Dynamic (or flow type)

  • With a cloud of snow particles:
  • at the front level (aerosol avalanche)
  • behind the front (avalanche with a panache)
  • Without a cloud (streaming avalanche)

Corrected snow

  • With
  • Without

Presence of blocks and / or other elements

  • With (tabular blocks, ice, rocks, trees)
  • Without

Deposit Superficial roughness

  • Poor (fine deposit)
  • Important (bad deposit: blocks, bowls)

Snow quality

  • Wet (wet deposit)
  • Dry (dry deposit)

Visible soiling

  • With (soiling avalanche: earth, blocks, trees)
  • Without (clean avalanche)
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Avalanche risk assessment In populated areas

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Avalanche characteristics and actions

Powder snow avalanche

  • Lengthwise profile of an avalanche: depends on the

wind direction

  • Reference pressure: 10 kPa < Pd < 30 kPa
  • Application height of Pd: all the height of the exposed

walls

Avalanche height: currently 30 to 40 m but may be > 100 m

  • Application direction of Pd: wind direction
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Avalanche risk assessment In populated areas

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Avalanche characteristics and actions Powder snow avalanche

  • Effects to be taken into account:
  • direction of Pd: wind direction

Pd ( +10 kPa)

  • 0.2 to -0.5 Pd
  • 0.3 to -0.8 Pd
  • 0.2 to -0.5 Pd

Avalanche Avalanche

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Avalanche characteristics and actions Wet snow avalanche

  • Lengthwise profile of an avalanche: 3 zones (accumulation,

flow, deposit)

  • Reference pressure: 30 kPa
  • Application height of Pd: case of non submerged

buildings

Red zone Blue zone White zone 4 m 5 m 2 m

qhF

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Avalanche characteristics and actions Wet snow avalanche

  • Lengthwise profile of an avalanche: 3 zones (accumulation,

flow, deposit)

  • Reference pressure: 30 kPa
  • Application height of Pd: case of submerged buildings

Red zone Blue zone White zone 4 m 6 m

qhF qvF qpF

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Avalanche characteristics and actions Wet snow avalanche

  • Application direction of Pd: direction of the more

down graded slope

  • Effects to take into account:
  • normal stress:

= c Pd

  • tangential stress:

= c Pd

c: shape coefficient that describes the interaction between the work and the snow flow: c = 2 sin2 : coefficient of static friction: 0,2 0,4

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Avalanche characteristics and actions Wet snow avalanche with carried items

  • This impact is to be added to the avalanche stresses
  • Punctual stress of 25 cm of diameter:
  • 100 kN for an avalanche of 30 kPa
  • 66 kN for an avalanche of 20 kPa
  • 33 kN for an avalanche of 10 kPa
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Avalanche risk assessment In populated areas

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Risk analysis results depend on analysis scale

Mountain Massif Slope Snowy coat Global environmental impacts Local environmental impacts Economical, sociological impacts Behavioral knowledge

Scale of avalanche risk analysis

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  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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System analysis : massif scale and slope scale

With a civil engineering point of view

Massif scale Structural analysis: Functional analysis: Workable massifs Unworkable massifs To be sure for humans To be beneficial To do not make damage on workable massifs

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Avalanche risk assessment In populated areas

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System analysis : massif scale and slope scale

With a civil engineering point of view

Slope scale

Upstream Starting zone Flow area Downstream

Structural analysis:

Accumulation basin Gorge Booting outcome Fauna and flora Skiers Station personal Habitants Communication system Ski lifts

Runout zone

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Risk scenarios : slope scale Searching of all chaining of events that can lead to:

– injured, dead – economical losses – material damages – environmental losses

Simplified example of a risk scenario:

Avalanche Skier seriously injured Road cut Evacuation of the skier at the stop area by station personal Evacuation to the hospital impossible Death

  • f the

skier

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Quantification of avalanche hazard To collect knowledge on snowy coat all

  • ver the massif and the slopes:

Modeling of the spatial snow deposit

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Quantification of avalanche hazard To collect knowledge on snowy coat all

  • ver the massif and the slopes:

Permanent investigation

  • n avalanches (EPA)

Location map of avalanche phenomena (CLPA)

In France, it is provided and managed by: Office National des Forêts (ONF): collection on the ground CEMAGREF: centralization of the information and map making

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Quantification of avalanche hazard Listing of the avalanche consequences by the ANENA:

October 2007 – September 2008 Repartition of the average number of fatal accidents and the number of deaths by avalanche type

Plate Unknown Localised

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Quantification of avalanche hazard Listing of the avalanche consequences by the SLF:

2007 – 2008 period Repartition of avalanche accidents by slope downgrade

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Time Avalanche event Risk prevention Protection against risks Crisis management Repair Improvement of the prevention and protection actions Gravity Probability Inacceptable risk Acceptable risk Protection Prevention

Mitigation techniques

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Mitigation techniques Prevention - Actions on constructions

Overall constructive disposals – building grouping

Mutual protection, protection of circulations On line

Reinforced building

Avalanche

< 10 m < 10 m

On stem

Avalanche

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Mitigation techniques Prevention - Actions on constructions

Particular constructive disposals

  • Foresee and access and an entrance on the non exposed

facades

  • Design facades without hold-in corner when there are face to

the avalanche

Marc Givry

Bad solution

Need of reinforcement

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Mitigation techniques Prevention - Actions on the snowy coat

Preventive releasing of avalanches Avalhex balloon

Generate explosion of a balloon blown up of Hydrogen & Oxygen Spherical blast wave

Catex

Wire bringing explosives above the snowy coat

Rapin

Gazex

Gas burst (mix of propane & oxygen)

Ancey

“Avalancheur”

Pneumatic bowler of explosive arrows

Duveau Davidof

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Avalanche risk assessment In populated areas

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Mitigation techniques Prevention - Actions on persons

  • Information provided at the department level
  • Information provided at the level of the ski

station

  • Signalling of the avalanche risk

Yellow flag for poor or limited risks Flag with black and yellow checked board important and marked risks Black flag for very important risks

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Avalanche risk assessment In populated areas

  • A. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010

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Mitigation techniques Protection

  • Permanent active protection: reforestation, wind & snow

barriers, buzzard roof, tire racks, fillets…

  • Permanent passive protection:

Valla, Rapin Valla, Rapin Valla, Rapin

Stem Stopping dike Deflectors

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Urban Habitat Constructions under Catastrophic Events

FINAL CONFERENCE. Naples, 16th - 18th September 2010

Thank you for your attention

Avalanche risk assessment in populated areas