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Urban Habitat Constructions under Catastrophic EventsFINAL CONFERENCE. Naples, 16th - 18th September 2010
Aurélie Talon & Jean-Pierre Muzeau
Polytech’Clermont-Ferrand (CUST) - LaMI
Blaise Pascal University
Clermont-Ferrand - France
Avalanche risk assessmentin populated areas
Avalanche risk assessment In populated areasA. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010
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Context
Avalanche PersonsStructuresInfrastructuresCommunicationsEnvironmentEconomy
Damages on issues caused by an avalanche
Hazard
Issue Risk
Avalanche risk assessment In populated areasA. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010
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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
Avalanche risk assessment In populated areasA. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010
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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
Avalanche risk assessment In populated areasA. 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 minutesComparison: 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
Avalanche risk assessment In populated areasA. 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
resistancet=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 02.826 (in kN/m2)
Avalanche risk assessment In populated areasA. 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 snowFine grains
Beakers
Round grains
Pictures: courtesy of Météo France
Avalanche risk assessment In populated areasA. 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 snowGlass bridge
Increasing of the cohesion
but failure propagation due to the snowy coat rigidity
Anena
Avalanche risk assessment In populated areasA. 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
Avalanche risk assessment In populated areasA. 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
• Plate avalanche
Avalanche risk assessment In populated areasA. 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
• Plate avalanche
• Wet snow avalanche
Avalanche risk assessment In populated areasA. 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 out cone
Upstream
Downstream
Departure area
Flow area
• FT: traction strength
•FR: resistance strength
When FT>FR: departure of the avalanche
Avalanche risk assessment In populated areasA. 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 avalanchesArea 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
of 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)
Avalanche risk assessment In populated areasA. 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)
Avalanche risk assessment In populated areasA. 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
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
Avalanche risk assessment In populated areasA. 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
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
Avalanche risk assessment In populated areasA. 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 non submerged
buildings
Re
d z
on
e
Blue zone
Wh
ite
zo
ne
4
m
5 m
2
m
qhF
Avalanche risk assessment In populated areasA. 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
Re
d z
on
e
Blue zone
Wh
ite
zo
ne
4
m
6 m
qhF
qvF
qpF
Avalanche risk assessment In populated areasA. 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
• 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
Avalanche risk assessment In populated areasA. 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
Avalanche risk assessment In populated areasA. Talon & J.-P. Muzeau – B. Pascal Univ., France – COST C26 Final Conf., Naples, 16th - 18th September 2010
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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
Behavioralknowledge
Scale of avalanche risk analysis
Avalanche risk assessment In populated areasA. 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 viewMassif 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
Avalanche risk assessment In populated areasA. 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 viewSlope scale
Upstream
Starting zone
Flow area Downstream
Structural analysis: Accumulation basinGorgeBooting outcomeFauna and floraSkiers
Station personalHabitantsCommunication system
Ski lifts
Runout zone
Avalanche risk assessment In populated areasA. 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:
AvalancheSkier
seriously injured
Road cut
Evacuation of the skier at the stop area by station personal
Evacuation to the hospital impossible
Death of the skier
Avalanche risk assessment In populated areasA. 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
over the massif and the slopes:
Modeling of the spatial snow deposit
Avalanche risk assessment In populated areasA. 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
over the massif and the slopes:
Permanent investigationon avalanches (EPA)
Location map of avalanchephenomena (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
Avalanche risk assessment In populated areasA. 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
UnknownLocalised
Avalanche risk assessment In populated areasA. 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 accidentsby slope downgrade
Avalanche risk assessment In populated areasA. 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 preventionProtection against risks
Crisis management
RepairImprovement of the prevention and protection actions
Gravity
Probability
Inacceptable risk
Acceptable risk
Protection
Prevention
Mitigation techniques
Avalanche risk assessment In populated areasA. 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 constructionsOverall constructive disposals
– building grouping
Mutual protection, protection of circulations
On line
Rein
forc
ed
b
uild
ing
Avalanche
< 10 m < 10 m
On stem
Avalanche
Avalanche risk assessment In populated areasA. 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 constructionsParticular 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
Avalanche risk assessment In populated areasA. 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 balloonGenerate explosion of a balloon
blown up of Hydrogen & Oxygen Spherical blast wave
CatexWire bringing explosives
above the snowy coat
Rapin
GazexGas burst (mix of
propane & oxygen) Ancey
“Avalancheur”Pneumatic bowler of explosive arrows
Duveau
Davidof
Avalanche risk assessment In populated areasA. 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 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
Avalanche risk assessment In populated areasA. 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, RapinValla, RapinStem
Stopping dikeDeflectors
Urban Habitat Constructions under Catastrophic EventsFINAL CONFERENCE. Naples, 16th - 18th September 2010
Thank you for your attention
Avalanche risk assessmentin populated areas