Tom Wilson1; Carol Stewart1; Graham
Leonard2; Gustavo Villarosa3; Valeria
Outes3; Heather Bickerton1; Peter Baxter4
1:University of Canterbury, New Zealand
2: GNS Science, New Zealand
3: Universidad de Comahue, Argentina
4:University of Cambridge, United Kingdom
Overview
 Impacts from large silicic eruptions in Patagonia
(southern South America)
 Evacuations
 Infrastructure disruption
 Agricultural impacts
 Is it possible to identify vulnerability thresholds?
 Managing volcanic ash risk...some perspectives
Research Context – Ash Impact Research
•
•
•
Over the past 20 years our New Zealand research
group (and collaborators) have aimed to undertake a
sustained and systematic approach to volcanic impact
assessment
- critical infrastructure: electricity, water supplies,
wastewater, land and air transport,
telecommunications
- ash cleanup and disposal
- primary industries, e.g. agriculture
- social impacts
- emergency management
Reconnaissance trips to impacted areas to bring
lessons home
Followed by laboratory testing of critical infrastructure
components...VAT Lab
Recon Trips: by volcano & year visited
Redoubt 1996; 2010
Eldfell (Heimaey) 2008
Shinmoedake
2011
Etna
2003
Sakurajima
2001
Pacaya
2010
Pinatubo
2007
Merapi
2006
Tungurahua
2005; 2010
Lapevi
2003-05
Ruapehu
1995-96
Puyehue Cordon-Caulle
2012
Hudson
2008
Chaiten
2009
Reconnaissance Trips
1) How did impacts unfold in real situations,
 what were main problems,
 what was resilient/tolerant (equally important)
 what mitigation actions were effective,
 previous preparedness,
 lessons learned, adaptive behaviours, etc
2) Trips conducted at various time intervals afterwards
3) Trips range from small scale (1 person), to larger multi-
disciplinary teams
4) Emphasis on collaborating with local authorities,
scientists, and utility managers
5) Development of standardised impact assessment
procedures
What impacts does ash
fall have on urban and
rural environments?
 New Zealand and
Patagonia share similar:
 Latitude
 Volcanoes
 Climate (esp. west)
PUYEHUE
CORDON-CAULLE
CHAITEN
HUDSON
Jaccobacci
40°S
PCC
Villa La Angostura
Bariloche
CHAITEN
Chaiten
Futaleyufu
Esquel
Trevelin 2008 Chaiten Eruption
•
•
•
•
HUDSON
Puerto Ibanez
VEI 4
0.5-1.0 km3 bulk volume
150,000km2 affected
Rhyolite
1991 Hudson Eruption
• VEI 5
• 4.3 km3 bulk volume
• 100,000km2 affected
• Trachyandesite-rhyodacite
Chile Chico
Los Antiguos
References:
• PCC: Villarosa et al. unpub
data
Tres Cerros
• Chaiten: Watt et al. 2009;
Puerto San Julian
Alfano et al. 2011
• Hudson: Scasso et al. 1994
Perito Moreno
50°S
2011 Puyehue Cordon-Caulle
Eruption
• VEI 4
• ~4.5 km3 bulk volume
• 150,000km2 affected
• Rhyodacite
2008 Chaiten
Eruption
Late-April-2 May: seismic
activity
Late 2 May: Plinian
eruption began at Chaiten
volcano
20 km column height
Source: NASA
•
Initial Evacuation of isolated rural areas affected by ashfalls were evacuated
during the night of the 2-3 May.
•
Significant concerns that the eruption would continue to increase in intensity
(pyroclastic flow hazards)
•
Evidence of pyroclastic
flow and lahar deposits
under Chaiten town
(pop. 4,000)
Evacuation of Chaiten town
•
Over 5,000 people evacuated from the town and surrounding areas by boat
and vehicle between 3-4 May 2008. Usually with minimal possessions (speed
was key).
•
All available ships amassed at Chaiten harbour (24 hours).
•
Public + private resources used.
Evacuation management
• Evacuees were separated across several
different towns.
• Images of houses flooded/destroyed
and pets roaming the streets was very
distressing
- media management important
Exclusion Zone Management
• Some residents had a strong
desire to return to Chaiten...
• Initially the area was off-limits
to anyone – some exceptions
(e.g. Scientists)
• Police controlled the exclusion
zone - looting and safety
• Some organised trips for
residents to collect personal
possessions
Long term planning...what to
do with Chaiten?
1.
Reoccupy
2.
Abandon and relocate town
3.
Abandon and disperse population
Strong sense of community
Following two risk assessments, the
town was officially abandoned on 29
January 2009
But....decision ‘reversed’ and
reoccupation of Chaiten by 2012
Source: NASA
75 mm of ash fall induced infrastructure failure in
Futaleufu, Chile (2,000 residents - temporary
evacuation)
• Water supply compromised
• Power supply cut
• Roads disrupted by thick ashfalls
• Health concerns
Compounded effects
Tourism and agriculture severely impacted
Evacuation of >80% of town. Duration: 1-12 months
1991 Hudson eruption
 Several thousand people
evacuated within several days weeks (issue with returning)
 Reactive, mostly self- evacuation
from farms and small towns
 Evacuations driven by:
- Public health concerns of air and
water quality
- Fear of roof collapse (Ibanez Valley
where ash fall >250 mm)
- Livestock death due to feed
coverage and water contamination
- Disruption of essential services
(urban)
1993 – S. Weaver
Length of farm abandonment following eruption vs.
ashfall depth
Length of Abandonment following eruption (Year)
1991
1996
2001
2006
0
200
Ash Depth
400
600
30-60 km from vent
800
60-80 km from vent
1000
200-300 km from vent
1200
1400
1600
1800
2000
Wilson et al. 2011
Ash Impacts to Agriculture
(brief summary)
 Livestock: starvation, irritation, poisoning
 Pastures and crops: coverage, toxicity (rare),
UV reduction, acid damage, lodging, soil cycles
disrupted, soil fertility impacts, etc.
 Water Supplies: turbidity, toxicity (rare)
 Critical Services: disruption to electricity,
roads, etc.
 Variety of mitigation options
Wilson et al. 2011
Farmer Perception of Productivity Change between 1991-2008
40
20
0
-20
-40
-60
-80
-100
0
200
Ash Depth (mm)
400
600
30-60 km
800
60-90 km
1000
90-120 km
1200
300-400 km
1400
1600
1800
2000
•
•
Ashfalls >300 mm led to large productivity decline (most had been
abandoned for 5-16 years)
Ashfalls <300 mm lead to a range of productivity adjustments
Eruption
HUDSON 1991
PUYEHUE CORDONCAULLE 2011
CHAITEN 2008
Town Affected
Puerto
Ibanez
Chile Chico
Los
Antiguos
Perito
Moreno
Tres
Cerros
Distance from Vent
(km)
90
120
125
175
473
Puerto
Chaiten Futaleyufu Trevelin
San Julian
545
11
75
100
Esquel
110
Villa La
Bariloche Jaccobacci
Angostura
44
90
231
Thickness of
ash fall (mm)
Ground
common
20
100
80
20transportation:
40
5
20most30
15
10
150
40
35
Ash hazard Duration of
and often longest disruption.
character- main ash fall 4 days 4 days 4 days 4 days 2-4 days 2-4 days 3 days 6 days 4 days 2-3 days 5-6 days 5-6 days 5-6 days
istics
Roads (and properties) require clean up 
Remob of
5-10
5-10
0.5-4
6-18
6-18
6-12
6-12
>18
costly
and
ash
15 years 15 years 15
years 15
yearstime consuming
1-2 years
years
years
years
months months months months months
(duration)
Power
Water
Critical
Infrastructure
Ground
Transport
Waste-water
& Sewage
Telecom
Municipal
Cleanup
Undertaken
Duration
DURATION
Official Evac
Hour(s)
Evacuation Self evac –
of Day(s)
immediate
population Self evac long term
Month(s)
Year(s)
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes Yes Yes Yes Yes Yes
Electrical + Water: high
dependence  high disruptive
Yes
Yes
No
No
No
No
No
impact
SEVERETY
No
No
No
No
No
Few isolated issues
<50% <50% <30% <25% >75% <5% 100% >50% <5% <5% <20% <5% <20%
Widespread outages
design
<50% Yes
Yes
Yes >75% Yes >50% System
----key factor
???
--Total disruption
Yes
Can thresholds be established?
 Hypothesis of establishing a threshold
of ash hazard intensity for common
levels of disruption or evacuation
requirements is probably null
 Ash fall complexity

duration, frequency, physical + chemical
properties, etc.
 Dependent on pre-existing state of
exposed communities/assets
Summary of ash fall impacts to critical infrastructure
 Disruptive rather than catastrophically damaging
 Most infrastructure systems will tolerate volcanic ash...up to a
point
 Loose relationship with ash thickness/load, but strongly
influenced by:
 system design
 level of planning
 adaptive capacity
 The complex characteristics of volcanic ash can create a range of
possible direct and indirect impacts
 Possibly leading to complex, cascading effects
 Individual case-by-case assessment approach probably most
appropriate
Evacuations
Anxiety of ash
contamination
of water
supplies
 Official evacuations used to
manage proximal hazards
 But self-evacuation very
common in areas exposed to
ash ash fall
 Duration of exposure to ashy
conditions will influence
evacuation decision and
duration of evacuation
 Primary air fall
 Remobilisation
 Few evacuation from fear of
roof collapse
 insufficient ash loads
Airborne ash =
anxiety of
respirable
hazard
Anxiety of ash
contamination
of food
supplies
Drivers of
evacuation
following ash
falls
(Fear of)
Roof
collapse
Critical
Infrastructure
disruption
(power, water,
etc.)
Loss of industry
(e.g. agriculture,
tourism, etc.)
Return of evacuees following ashfall
 What is there to return to?
 Speed and quality of system restoration
 Urban clean up  public health concerns
 Agriculture rehabilitation
 Restoration of essential services (critical
infrastructure)
 Agricultural regions >300mm ash fall will
struggle
 Significant reduction in productivity
 Tourism areas
 Disruption of attractions
 Negative perception
Some considerations for mitigating ash fall risk

Sustained preparedness activities are valuable. But specific continuity planning
for volcanic eruptions is rare




Poor awareness of hazard and likely impacts .
Strong adaptive capacities often exhibited + novel and unique approaches commonly
developed
Lack of preparation actions was costly (time of restoration, delayed key decisions)
Trial and error approach  Delays effective response, risks public relations ‘issues’

Access to specialised, sector-specific impact, preparedness and post-event
response/recovery information

Effective and timely warnings



Mutual support/continuity agreements




Assess public health and agricultural impacts
Essential for risk communication
Integration of scientific organisations within emergency management
framework



Mutual support agreements: access to greater resources
Clean up plan: critical routes, pre-identified ash dump sites
Standardised physical and chemical ash characterisation


Allow protective actions to be taken, e.g. seal buildings, shutdown vulnerable systems, etc.
Meaningfully tailored to end-user requirements (triggers for action)
Extends beyond volcanologists
Agriculturalists, engineers, social scientists, etc.
Timely, adaptable and consistent impact assessment
Thank you
Any questions?