ws 18 landslides theo van asch
DESCRIPTION
Dit is de powerpointpresentatie van Theo van Asch over landslides, uitgesproken op de KNAG Onderwijsdag 2009 op 6 november in Nijmegen.TRANSCRIPT
Contd… Laprak Landslide The Landslide problem
Theo van Asch: Faculty of Geosciences Utrecht in collaboration with Cees van Westen and Dinand Alkma
ITC Enschede
Landslide
Definition:
Landslide is defined as the movement of a mass of rock, debris or earth down the slope, when the driving (gravity) forces exceeds the frictional resistance of the material.
Landslide hazard analysis
Landslide risk analysis.
Landslide risk management
Risk governance
The Landslide problem
Landslide hazard and risk analyses
• Type?• Where?• How often?• How fast and intense?• How far?• Which elements at risk?• How vulnerable? • Costs?
Hazard assessment
Risk assessment
Landslide classification
The most important characteristics to classify landslides: Material: Rock, Soil Lithology, structure, Geotechnical
properties Landslide geometry: Depth, Length, Height etc. Type of movement: Fall, Slide, Flow etc Water: Dry, wet, saturated Speed of movement: Very slow, slow etc.
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Types of movement
Fall
Topple
Slide
Rotational
slide
Translational
slide
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Flow
Debris/Mud Flow
Debris avalanche
Velocity of mass movement related to water content and type Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Translational slide
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Rotational slide (Slump)
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Rotational slide (Slump)
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
debris flowType?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
debris flow
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Debris avalancheType?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Debris avalancheType?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Spatial probability of occurrence
Landslide susceptibility maps
Landslide susceptibility
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Landslide susceptibility
How to make a susceptibility map?– Make a landslide map– Determine causing /triggering factors– Make (statistical) correlation between
landslide occurrence and factors– Make a zonation map with probability of
occurrence of future landslides.
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Landslide maps
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Landslide maps Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Use of factor maps .
Slope classes
Landuse
Aspect classes
Soil depth
LithologyDistance from river
Weight mapsSusceptibility map Total weight
Statistical correlation techniques with landslide map
Elevation
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Susceptibility mapType?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
The landslide hazard map
Susceptibility map plus temporal frequency
Landslide hazard maps
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
1D formulation
The driving force and frictional resistance
t
u)h(ρS
x
hkcosαsinαρghc
x
uuc
t
uρh s
sfxxxx
forcenormalαcosghρ
cosα1cosα
ghρσ
force drivingαcossinαghρcosα
1sinα
ghρτ
1*ghρsliceweight
2flfl
flfl
fl
x
z
hi
1m
1/cos
hi-1hi+1
fl,,c,
x x
di-1
977)Cousssot(1uh
3ητ
2
3
ρgh
1'tanαcosS cx
2f
The role of deterministic models
Deterministic (physical ) models are useful to determine the temporal frequency of slope instability
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Driving forces
Resisting forces
Groundwater recharge
Precipitation /percolation
Safety factor<1
Slope triggered by rain
Coupled hydrological-slope stability models calculates over time:
Temporal frequency of instability
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Δt
uh
ρh
ρSfktanβ
s
1sinαcosαΔtgcuuu
s
Δtculaxu
uh
3ητ
2
3
ρgh
1'tanφαcosSf
nis
in
s1/2ni
ni
ni
ni
n1i
n1i
ni
ni
ni
1ni
1/2nin
icn
i
ni
21/2ni
Δt
uh
ρh
ρSfktanβ
s
1sinαcosαΔtgcuuu
s
Δtculaxu
uh
3ητ
2
3
ρgh
1'tanφαcosSf
nis
in
s1/2ni
ni
ni
ni
n1i
n1i
ni
ni
ni
1ni
1/2nin
icn
i
ni
21/2ni
Δt
uh
ρh
ρSfktanβ
s
1sinαcosαΔtgcuuu
s
Δtculaxu
uh
3ητ
2
3
ρgh
1'tanφαcosSf
nis
in
s1/2ni
ni
ni
ni
n1i
n1i
ni
ni
ni
1ni
1/2nin
icn
i
ni
21/2ni
Δt
uh
ρh
ρSfktanβ
s
1sinαcosαΔtgcuuu
s
Δtculaxu
uh
3ητ
2
3
ρgh
1'tanφαcosSf
nis
in
s1/2ni
ni
ni
ni
n1i
n1i
ni
ni
ni
1ni
1/2nin
icn
i
ni
21/2ni
The role of deterministic models
Deterministic (physical ) models are also useful to determine the speed extent and
impact of landslides
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Rapid gravitational debris/mudflowsSource area
Remaître 2006
Faucon creek French Alps 2003 event
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Rapid gravitational debris/mudflowsTransportation and deposition area
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Faucon creek French Alps: 2003 eventFaucon creek French Alps: 2003 event
Rapid gravitational debris/mudflowsSource area
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Faucon creek French Alps: Faucon creek French Alps: 2003 event2003 event
Rapid gravitational debris/mudflowsScouring in transportation area
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Rapid gravitational debris/mudflowsDeposition area
Faucon creek French Alps: 2003 eventFaucon creek French Alps: 2003 event
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Coh = 1 kPa, K = 5.0E-2 m kPa.s-1
Average velocity: 6 m s-1
Model simulation in deposition area Faucon Barcelonette
Faucon creek French Alps: 2003 eventFaucon creek French Alps: 2003 event
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Wartschenbach 1997 (Austria)Wartschenbach 1997 (Austria)
Rapid gravitational debris/mudflowsDeposition area
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Simulation of an earthflowType?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
• All objects, persons, animals, activities and processes that may be adversely affected by hazardous phenomena, in a particular area, either directly or indirectly.
What are elements at risk?
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Different elements at risk
Physical elements HousingInfrastructure (roads, railways.airport etc )Critical facilities (schools hospitals police..etc )Utilities (Power supply ,transport services,governmental services..etc)
Economic elements Buseness and trade activities, access to work,agricultural land, work force,
Societal elements Moving people, vulnerable age categories,Low income groups,homeless people, disabled ,gender
Environmental elements Resources: like air, water, fauna, flora ,biodiversity,
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
• Buildings are one of the most important groups of elements at risk.
• They house the population. The behavior of a building under a hazard event, determines whether the people in the building might be injured or killed.
Important elements:buildings
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Important element:population
• Static characteristics: – Relate to number of inhabitants, the densities of the
population and the age compositions;
Dynamic characteristics: – Relate to the activity patterns of the people, and the
distribution of the population in space and time. – One of the most important socio-cultural vulnerability
indicators is the time-distribution of the population.
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Rockfall on school:
1400 deaths
Landslide on neighborhood:
800 deaths
Flood caused by a landslide dam
Debris flow on 14/9 destroying the remains of Old Beichuan
City of Beichuan, deserted after the earthquake on 12 MayType?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Types of vulnerability
• Physical Vulnerability:
• Economic vulnerability: • Social vulnerability• Environmental vulnerability
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Types of vulnerability
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
• Vulnerability curves:
– Are constructed on the basis of the relation between hazard intensities and damage data
– Relative curves: they show in the degree of damage (between 0 and 1) of a property
How to express physical vulnerability?
Low vulnerability
curve
High vulnerability curve
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Landslide vulnerability assessment is still in its infant stages
• There is a wide variety of processes • Lack of historical damage databases
Vulnerability assessment for mass movements
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Damages due to various landslides.
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Damages due to various landslides.
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Quantitative risk assessment
Risk = Hazard * Vulnerability * Amount
= Temporal frequency (H)
* Degree of loss to elements at risk (V)
*Cost quantification of elements at risk (A)
Quantitative Risk
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
A=US $ 50.000
V = 0.1
RP = 10 yearsH=0.1
A=US $ 200.000
V = 0.5
V = 1
A=US $ 100.000
Specific quantitative risk
Specific Risk =0.1 * ((0.1 *50.000)+(0.5*200.000)+(1*100.000))
Landslide
Quantitative specific Risk = H*V*A
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Landslide risk map of the Arno river basin over a period of 30 years. The risk is expressed as economic losses due to landslides for each terrain unit (from Catani et al. 2005)
Type?Where?How often?How fast and intense?How far?Which elements at risk?How vulnerable? Costs?
Risk map Arno river basin Italy