Módulo 5 4: Deslizamientos, flujos de escombro (huaycos), aluviones

Módulo 5
4: Deslizamientos, flujos de escombro
(huaycos), aluviones
Repeatedly and severely affected by
landslides, hundreds of people killed in
the past
Most recent disasters in 2006 & 2009
2006
Villa Restrepo, Depto del Tolima, Colombia
2009
• Zona de iniciación
before
Tajhaz Project/Schneider
after
Tajhaz Project/Schneider
Guttannen, Alpes Suizos, 2005
Kt. Bern/Hählen
Kt. Bern/Hählen
Abancay
Predes
Cordillera Blanca, Perú
Aluvión
Palcacocha 1941
1939
Glaciar Belvedere, Monte Rosa, Italia, Laguna Efímera
What is a landslide?
U.S. Geological Survey
AGUA
Río
Transporte
de material
fino/grueso
en el río
MATERIAL
FINO
Deslizamiento
modificado según Haeberli y Naef, 1988
Caída
de roca
ROCA
Stricker, 2011
• Zona de transporte
Arrival of a
debris flow
front (video)
From the Illgraben
observation station,
Susten (VS)
Depth: 2m
Velocity: 5 m/s
Density: 2000 kg/m3
Total volume:
30’000 m3
Slope stability considerations:
Factor of safety
Flujos de escombro (debris flow)
Modelo Coulomb
shear
stress/
tensión
cortante
shear resistance
c = cohesion
σ = normal stress
ϕ = internal friction
μ = dynamic viscosity
v = velocity, y = depth
según Coussot and Meunier, 1996,
y Schatzmann, 2005
Un flujo de escombro
Stolz, 2006
Formación de Levée
Stolz, 2006
Stop abrupto del flujo
Unchannelized debris flow
Recent example of a very large event from Seoul, Korea
Unchannelized debris flow
Recent example of a very large event from Seoul, Korea
Monitoreo de flujos de escombro
3 rain gauges
Geophones
Force plate
Depth sensors
Laser, ultrasonic, radar
B. McArdell
100
Cumulative distribution
90
80
70
60
50
40
30
20
10
0
0.1
1
10
100
1000
10000
Flow depth [m], front velocity [m/s],
front discharge [m3/s], event volume [m3]
B. McArdell
100000
100
Cumulative
percent
Cumulative
distribution
Cumulative
percent
Cumulative
distribution
100
75
50
25
50
25
0
0
1000
75
1500
2000
2500
Mass density of flow [kg/m3]
3000
0
0.25
0.5
0.75
Volume fraction of water
B. McArdell
1
Stricker, 2011
Huila/Páez
Abril 2007
Crecientes vs. Lahares/debris flows
Pierson, 1995
Röthlisberger 1970
Röthlisberger 1970
Röthlisberger 1970
Smithson et al., 2002
Erosion is related to:
• Surface slope
• Flow velocity
• Maximum discharge
• Shear stress
• Granular temperature
Erosion is mainly concentrated at the front of the debris flow
Glacier lake failures and outburst floods (aluviones)
Nevado Hualcán
Laguna 513
Pampa de Shonquil
Río Chucchún
W. Haeberli
Potentially inundated areas by GLOF
Reynolds et al. (1998)
• October 1988: 1 syphon: 190 l/s
• Christmas 1988: 1 million m3 drained but lake level remains the
same
• January 1989: another syphon, total drainage capacity 500 l/s
• March 1989: lake level lowered by 2 m
• June 1989: two more meters down
• June 1990: a total of 5 m lake lowering
• 1991: important ice avalanche causes impact wave, overtopping dam
but no one killed
• May 1993: Start of tunnel construction
Fundamental questions to consider:
• How likely is a glacier lake outburst flood?
• How large will the flood be?
• How far will the flow reach?
Estimate of probability of dam failure
Indicator
Attribute
Qualitative probability
Dam type
Ice
Moraine
Bedrock
High
Medium to high
Low
Freeboard to dam height ratio
Low
Medium
High
High
Medium
Low
Dam width to height ratio
Small, 0.1 - 0.2
Medium, 0.2 - 0.5
Large, > 0.5
High
Medium
Low
Impact waves by ice/rock falls
reaching the lake
Frequent / large volume
Sporadic / medium volume
Unlikely / small volume
High
Medium
Low
Extreme meteorological events
(high temperature/ precipitation)
Frequent
Sporadic
Unlikely
High
Medium
Low
from Huggel et al., 2004
Estimate of maximum discharge for different outburst mechanisms
from Walder and Costa, 1996
Estimate of maximum discharge for moraine-dammed lakes
from Huggel et al., 2002
Type of lake and dam failures
Type of lake and dam failures
from Huggel et al., 2002
from Huggel et al., 2002
www.gletschersee.ch
Hydrograph of lake outburst in May 2008
Bauliche Massnahmen Abflussstollen
Estimate of maximum runout (reach)
Estimate of maximum runout (reach)
from Huggel et al., 2002
from Huggel et al., 2002
Huggel, Paul
Process interactions and chains
S. Zgraggen
Unterer Grindelwald Glacier, Switzerland
Städelin, 2008
Structural prevention measures
Structural mitigation measures
Structural mitigation measures
La construcción de túneles a través de la roca para bajar el nivel de la Laguna 513
Reynolds, Dolecki, Portocarrero
Reynolds et al. (1998)
Palcacocha
Patzelt 2004
Kinzl 1932
Typical moraine from the
Little Ice Age (~1850),
Up to 36° steep, with ~100m
sediment thickness,
freeboard of only 1-2m
before 2001 GLOF
Crealp
Structural construction at the lake
Philippe Teysseire
Täschalp, dam mitigation structures
Bauliche Massnahmen Schutz/Ablenkungsdamm Täschalp
Täsch, sediment retention
reservoir