Evacuations and other impacts from large ash producing eruptions: perspectives from Patagonia

Tom Wilson1; Carol Stewart1; Graham Leonard2; Gustavo

Villarosa3; Valeria Outes3; Heather Bickerton1; Peter Baxter4

1:University of Canterbury, New Zealand2: GNS Science, New Zealand

3: Universidad de Comahue, Argentina4:University of Cambridge, United Kingdom

Workshop on Strategy of Volcanic Disaster Mitigation 27 November 2013

OverviewImpacts from large silicic eruptions in

Patagonia (southern South America)EvacuationsInfrastructure disruptionAgricultural 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 visitedEldfell (Heimaey) 2008Redoubt 1996; 2010

Pinatubo2007

Merapi 2006

Sakurajima2001

Shinmoedake2011

Ruapehu1995-96

Lapevi2003-05

Hudson2008

Chaiten2009

Puyehue Cordon-Caulle2012

Etna2003

Tungurahua2005; 2010

Pacaya2010

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

Reconnaissance Trips

What impacts does ash fall have on urban and rural environments?

New Zealand and Patagonia share similar:LatitudeVolcanoesClimate (esp. west) CHAITEN

HUDSON

PUYEHUE CORDON-CAULLE

References:• PCC: Villarosa et al.

unpub data• Chaiten: Watt et al.

2009; Alfano et al. 2011• Hudson: Scasso et al.

1994

40°S

50°S

Puerto Ibanez

Chile Chico

Los Antiguos

Tres Cerros

Puerto San Julian

Perito Moreno

Chaiten

FutaleyufuEsquel

Trevelin

Villa La Angostura

Bariloche

CHAITEN

HUDSON

PCC

Jaccobacci

1991 Hudson Eruption• VEI 5• 4.3 km3 bulk volume• 100,000km2 affected• Trachyandesite-

rhyodacite

2008 Chaiten Eruption• VEI 4• 0.5-1.0 km3 bulk volume• 150,000km2 affected• Rhyolite

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

1991 1996 2001 20060

200

400

600

800

1000

1200

1400

1600

1800

2000

30-60 km from vent60-80 km from vent200-300 km from vent

Length of Abandonment following eruption (Year)

Ash

Dep

th

Length of farm abandonment following eruption vs. ashfall depth

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

-100-80-60-40-20020400

50

100

150

200

250

300

30-60 km60-90 km90-120 km300-400 km

Farmer Perception of Productivity Change between 1991-2008

Ash

Dep

th (

mm

)

• 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

Wilson et al. 2011

Eruption HUDSON 1991 CHAITEN 2008 PUYEHUE CORDON-CAULLE 2011

Town Affected Puerto Ibanez Chile Chico Los

AntiguosPerito

MorenoTres

CerrosPuerto

San Julian Chaiten Futaleyufu Trevelin Esquel Villa La Angostura Bariloche Jaccobacci

Distance from Vent (km) 90 120 125 175 473 545 11 75 100 110 44 90 231

Ash hazard character-

istics

Thickness of ash fall (mm)

20 100 80 20 40 5 20 30 15 10 150 40 35

Duration of 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

Remob of ash

(duration)15 years 15 years 15 years 15 years 5-10

years5-10 years

0.5-4 years 1-2 years 6-18

months6-18

months6-12

months6-12

months>18

months

Critical Infra-

structure

Power

Water

Ground Transport

Waste-water & Sewage

Telecom

Municipal Cleanup

Undertaken Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes YesDuration

Evacuation of

population

Official Evac Yes No No No No No Yes Yes No No No No NoSelf evac – immediate <50% <50% <30% <25% >75% <5% 100% >50% <5% <5% <20% <5% <20%Self evac - long term <50% Yes Yes Yes >75% Yes >50% -- -- -- ??? -- --

DURATION

Hour(s)

Day(s)

Month(s)

Year(s)

SEVERETY

Few isolated issues

Widespread outages

Total disruption

Electrical + Water: high dependence high disruptive impact

System design key factor

Ground transportation: most common and often longest disruption. Roads (and properties) require clean up costly and time consuming

Can thresholds be established?

Hypothesis of establishing a threshold of ash hazard intensity for common levels of disruption or evacuation requirements is probably nullAsh fall complexity

duration, frequency, physical + chemical properties, etc.

Dependent on pre-existing state of exposed communities/assets

Summary of ash fall impacts to critical infrastructureDisruptive 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 impactsPossibly leading to complex, cascading effectsIndividual case-by-case assessment approach probably most

appropriate

Drivers of evacuation

following ash falls

Airborne ash = anxiety of

respirable hazard

Anxiety of ash contamination of

food supplies

Anxiety of ash contamination of water supplies

Critical Infrastructure

disruption(power, water,

etc.)

(Fear of) Roof collapse

Loss of industry (e.g. agriculture,

tourism, etc.)

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

Evacuations

Return of evacuees following ashfallWhat 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 Allow protective actions to be taken, e.g. seal buildings, shutdown vulnerable

systems, etc. Meaningfully tailored to end-user requirements (triggers for action)

Mutual support/continuity agreements Mutual support agreements: access to greater resources Clean up plan: critical routes, pre-identified ash dump sites

Standardised physical and chemical ash characterisation Assess public health and agricultural impacts Essential for risk communication

Integration of scientific organisations within emergency management framework

Extends beyond volcanologists Agriculturalists, engineers, social scientists, etc.

Timely, adaptable and consistent impact assessment

Thank you

Any questions?