Environment Waikato Policy Series 1999/10
Volcanic Risk Mitigation Plan
Prepared by:
Adam Munro
David Parkin
For:
Environment Waikato
PO Box 4010
HAMILTON EAST
26 May 1999
ISSN: 1174-7234
Table of Contents
Table of Contents
i
Executive Summary
iii
Background and Explanation
v
1 Introduction
1
2 Pre-eruption: Mitigation Techniques for Non-crisis Periods
3
2.1
2.2
2.3
2.4
2.5
Geological Studies
Planning
Scientific Alert Levels and Science Alert Bulletins
Monitoring
Satellite Remote Sensing
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3 During an Eruption: A Description of Different Volcanic Hazards and Mitigation
Measures for those Hazards
3.1
Tephra Falls
3.1.1 People
3.1.2 Agriculture and Horticulture
3.1.3 Building Structures
3.1.4 Electricity
3.1.5 Water Supply
3.1.6 Wastewater Networks (Stormwater Drainage and Sanitary Sewers)
3.1.7 Sewage Treatment Plants
3.1.8 Gas
3.1.9 Transportation
3.1.10Communications
3.1.11Mechanical, Electrical and Electronic Equipment
3.2 Mitigation Measures for Tephra Fallout
3.2.1 People
3.2.2 Agriculture and Horticulture
3.2.3 Building Structures
3.2.4 Electricity
3.2.5 Water Supply
3.2.6 Wastewater Networks (Stormwater Drainage and Sanitary Sewers)
3.2.7 Sewage Treatment Plants
3.2.8 Transportation
3.2.9 Mechanical, electrical and electronic equipment
3.2.10Ash Disposal
3.2.11Detailed Mitigation Measures
3.3 Ballistic Fallout
3.3.1 Mitigation Measures for Ballistic Fallout
3.4 Lahars
3.4.1 Mitigation Measures for Lahars
3.5 Pyroclastic Flows
3.5.1 Mitigation Measures for Pyroclastic Flows
3.6 Pyroclastic Surges
3.6.1 Mitigation Measures for Pyroclastic Surges
3.7 Directed Volcanic Blasts
3.7.1 Mitigation Measures for Volcanic Blasts
3.8 Lava Flows
3.8.1 Mitigation Measures for Lava Flows
3.9 Debris Avalanches
3.9.1 Mitigation Measures for Debris Avalanches
3.10 Volcanic Gases
3.10.1Mitigation Measures for Volcanic Gases
3.11 Tsunamis and Seiches
3.11.1Mitigation Measures for Tsunamis and Seiches
3.12 Flooding
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3.13 Hydrothermal Eruptions
3.13.1Mitigation Measures for Hydrothermal Eruptions
3.14 Volcanic Earthquakes
3.14.1Mitigation Measures for Volcanic Earthquakes
3.15 Electrical Discharges
3.15.1Mitigation Measures for Electrical Discharges
3.16 Other Hazards
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References
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Appendix I: Scientific Alert Levels (Johnston, 1997a)
37
Appendix II: Detailed Mitigation Measures
38
Appendix III: 1995-1996 Ruapehu Eruptions Survey
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Table of Figures
Figure 1: Summary of volcanic hazards from a composite cone volcano
(after Myers et al., 1997)
1
Figure 2: Volcanic hazard management during non-crisis (pre-eruption) and
crisis (during an eruption) periods (after Johnston and Houghton, 1995).
2
Figure 3: Summary of the applications of remote sensing for volcanology (after
Oppenheimer, 1997).
8
Figure 4: Ash from Mount Ruapehu carried by southeasterly winds over Lake Taupo
during the 1995-1996 Ruapehu eruptions.
9
Figure 5: The interaction of volcanic gases during an eruption (after Johnston, 1997a).
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Figure 6: An eruption from Mount Ruapehu on 8 July 1996.
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Figure 7: Question 2 -What category do you class your business in?
54
Figure 8: Turnover of businesses that answered the Ruapehu survey (logarithmic scale).
56
Figure 9: The Arrangement of Zones around Mount Ruapehu
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Figure 10: Question 6 – Please indicate where your home or business is located.
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Figure 11: Series of graphs looking at the relationship between peoples’ location and
how likely they think they would be affected by a future eruption.
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Figure 12: Respondents’ knowledge of what to do during an eruption.
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Figure 13: How did you first learn that there was an eruption occurring from
Mount Ruapehu?
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Figure 14: Location of the respondent versus whether they were affected by the 1995-1996
Ruapehu eruptions.
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Figure 15: Question 19 – Did you suffer any economic loss related to the Ruapehu eruptions?69
Figure 16: Losses (NZ$) suffered by different types of business (Logarithmic Scale).
69
Figure 17: Types of stress suffered as a result of the Ruapehu eruptions.
70
Tables
Table 1: Educating the public about volcanic hazards (after Gregory 1995; Peterson, 1996;
Voight, 1996).
Table 2: Impacts on plants and soil from increasing ash thickness (after Folsom, 1986, and
Blong, 1984; in Neild et al., in prep).
Table 3: Periods of high crop risk from ash (after MAF, 1995; Neild et al.,1998).
Table 4: Mitigation measures for volcanic ash and the water supply
(after Johnston, 1997a, 1997b).
Table 5: Number of survey participants involved in each type of business.
Table 6 : How respondents solved or fixed problems caused by the Ruapehu eruptions.
Table 7: Common hints suggested by survey respondents.
Table 8: Lifestyle adaptations made in response to the Ruapehu eruptions.
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Table 9: Range of benefits from the Mount Ruapehu eruptions.
Table 10: Organisations that respondents turned to for advice or general
information during the 1995-1996 Ruapehu eruptions.
Table 11: Impact of a volcanic eruption from Mount Ruapehu in different seasons.
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Page iii
Executive Summary
The Volcanic Risk Mitigation Plan has been written:
a)
To achieve the natural hazards objectives of the Waikato Regional Policy
Statement. These are to define the management functions of Environment Waikato
and the district councils and to minimise the adverse effects associated with
natural hazards.
b)
In response to Environment Waikato ‘s volcanic risk management responsibilities
under the general provisions of the Resource Management Act 1991 and the Civil
Defence National Plan.
c)
To achieve Environment Waikato’s responsibilities under the Civil Defence Act
1983. The three aims of civil defence are to prevent loss of life, to help the injured,
and to relieve personal suffering and distress.
d)
To meet the International Decade for natural Disaster Reduction requirements.
These include the provision of mitigation plans involving long term prevention,
preparedness and community awareness.
e)
To integrate Environment Waikato’s activities with other organisations, and assist
them to achieve their organisation and professional responsibilities.
The plan confirms the principles accepted by Environment Waikato as the basis of the
Volcanic Risk Mitigation Plan. There is an emphasis on working in partnership with
district councils and communities to find acceptable solutions to volcanic issues.
The first section of the plan outlines the roles and responsibilities of district councils in
implementing volcanic risk mitigation measures, the second section outlines pre-event
techniques and the third section outlines techniques that could be used during an
eruption.
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Background and Explanation
The Waikato Region has more volcanic hazards than any other region in New Zealand,
because a large part of the Taupo Volcanic Zone (TVZ) lies within or adjacent to its
boundaries. There are three presently or potentially active volcanic centres located
within the Waikato Region, these being Tongariro, Taupo, and Maroa. Due to the
location of many urban areas (e.g. Turangi, Taupo, and Tokoroa) within the Taupo
Volcanic Zone, mitigation and contingency planning is an essential ingredient in
providing maximum protection to people living in these areas. Many of the North
Island’s vital Lifelines are also located in the Taupo Volcanic Zone - all of which could
be affected during a major eruption.
Five active volcanic centres are located outside the Regional boundary that pose just
as much risk to the residents of the Waikato Region than those volcanic centres
located within the Waikato Regional boundary. This contingency plan does not
specifically address these “other” areas. Information about these volcanic centres can
be found in the respective region’s volcanic mitigation and/or contingency plans.
Environment Waikato is responsible under statute to manage volcanic risk.
Environment Waikato and District Councils have responsibilities to avoid and lessen
natural hazards under the Resource Management Act (RMA) 1991. The emphasis for
Environment Waikato is on regional risk management. The emphasis for District
Councils is on the controlling the effects associated with the use of land. Both
Environment Waikato and District Councils have responsibilities for pre-event planning,
response, and recovery under the Civil Defence Act 1983.
The purpose of this plan is to outline suitable mitigation options that will minimise the
adverse effects of future volcanic activity on the Regional community and economy.
Principles
A number of principles have been used to develop Environment Waikato’s risk
mitigation plans. The principles used in previous plans are also applicable to the
volcanic risk mitigation plan. The general principles are:
a)
Recognise the Primacy of the Resource Management Act 1991
The Resource Management Act 1991 repealed and amended much of the
previous legislation relating to watercourses. The legislation that remains is
subject to the RMA. For example, Part 1 section 10A of the Soil Conservation
and Rivers Control Act 1941 states ‘nothing in this Act shall derogate from the
Resource Management Act 1991’.
Environment Waikato considers it vital in the development of mitigation policy to
recognise the primacy of the RMA, while promoting the integration of the various
Acts in policy development:
i)
ii)
iii)
iv)
v)
Resource Management Act 1991.
Soil Conservation and Rivers Control Act 1941.
Land Drainage Act 1908.
Local Government Act 1974.
Building Act 1991.
The advantages of integration are clarity, with responsibilities dealt with by the
most appropriate and legally bound agency, issues will not be passed from one
agency to another and administration will become more efficient. Integration will
be given overall authority through the Regional Policy Statement (RPS).
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Mitigation plans produced by Environment Waikato therefore reflect the
provisions of the Acts and is the approved policy of Environment Waikato
(Waikato Regional Council).
b)
Promote a Strategy of Avoidance then Mitigation
The RMA and the RPS give a strong lead for avoidance and mitigation through
the control of land use. Land known to be subject to natural hazards should be
subject to clear land use controls. New development, in particular, should be
analysed for potential exposure or risk from natural hazards. Volcanic
Contingency Plans, which complement mitigation plans, are written under the
requirements of the Civil Defence National Plan.
Mitigation is a tool which can be used to deal with situations where a combination
of the natural hazard and the vulnerability of the community create a risk.
Mitigation can be used for existing or proposed development to ensure an
acceptable level of risk is maintained.
c)
Information Readily Available
High quality information on hazards and potential risks and the widespread
dissemination of this information are vital for effective risk management and risk
reduction.
f)
Partnership with District Councils
Environment Waikato and district councils both have responsibilities for natural
hazard management. This Plan clearly defines the respective responsibilities
and promotes a partnership approach to management. The natural hazards
Section (3.8) of the Waikato Regional Policy Statement addresses the uncertainty
over the allocation of responsibilities of the regional and district councils. Section
3.8.3 Management of Natural Hazards, Policy One, acknowledges the role district
councils have historically undertaken for the control of the use of land.
h)
Community Safety
Environment Waikato recognises the value of community input in decision
making.
Environment Waikato and district councils have a responsibility to
enable communities to provide for their health and safety under the RMA.
Environment Waikato has responsibilities for community safety under the Civil
Defence Act 1983. The Waikato Region Civil Defence Plan 1996 states the three
aims of civil defence. These are:
vi) to prevent loss of life
vii) to help the injured
viii) to relieve personal suffering and distress.
Therefore when Environment Waikato assesses volcanic risk management
options, community safety has overriding importance.
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Related Documents:
This Mitigation Plan represents the final milestone in completing a comprehensive
study of the volcanic hazard and risk in the Waikato Region. Other related
reports/sources of information that this plan complements include:
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Regional Civil Defence Plan (and Standard Operating Procedures)
National Civil Defence Plan
National Volcanic Contingency Plan
Civil Defence Act 1983
Waikato Region Volcanic Hazard Assessment
Volcanic Risk Mitigation in the Waikato Region (University Thesis)
Crater Lake Instability Study
Lahar Hazard Assessment of the Tongariro River
Taupo District Council Volcanic Hazard Analysis
District Council’s Civil Defence Plans
District Council’s Volcanic Contingency Plans
IGNS Internet Site: www.gns.cri.nz
Ministry of Civil Defence Internet Site: www.mocd.govt.nz
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1
Introduction
As defined in the introduction, a volcanic hazard describes the physical characteristics
of an eruption (Blong, 1996). While a volcano is in eruption it will produce a variety of
hazards. Near-vent volcanic hazards tend to be very destructive, while distal hazards
may cause damage to structures or disrupt everyday life. Even when a volcano is not
in eruption, volcanic hazards such as debris avalanches or remobilised secondary
lahars can still occur. Figure 1 summarises some of the hazards that may be expected
from a typical composite cone volcano.
Mitigation of volcanic hazards can be undertaken during periods of crisis, while a
volcano is in eruption. Studies of recent eruptions have led to the identification of
mitigation measures that were used successfully while an eruption was in progress.
Extensive measures have been identified for the mitigation of problems caused by ash
fall. However, there are still a number of hazards that have few mitigation options
available. For example, pyroclastic flows and surges are so destructive that the only
really viable option is to evacuate the population at risk prior to the event.
The management and mitigation of volcanic hazards should not only occur during crisis
periods. It is also important that management of volcanic hazards is initiated and
undertaken in periods of non-crisis, prior to an eruption occurring. Pre-planning will
ensure that the mitigation measures employed in response to a crisis are successful.
Figure 2 illustrates the different aspects of volcanic hazard management under crisis
and non-crisis (pre-event) conditions.
Prevailing Wind
Eruption Cloud
Ash Fallout
Eruption Column
Ballistic
Fallout
Gas
Acid Rain
Lava Flow
Pyroclastic
Flow
Dome
Pyroclastic
Flow
Debris
Avalanche
Lahar
Figure 1: Summary of volcanic hazards from a composite cone volcano
(after Myers et al., 1997)
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Volcanic Hazard Management
Crisis
Non-crisis
Risk Reduction
- risk analysis
- land-use
planning
- mitigation
meaures
Preparedness
- volcano
surveillance
Crisis Management
- volcano
surveillance
- contingency
planning
- warnings
and public
information
- public
education
- emergency
response
- recovery
Figure 2: Volcanic hazard management during non-crisis (pre-eruption)
and crisis (during an eruption) periods (after Johnston and
Houghton, 1995).
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Pre-eruption: Mitigation Techniques for
Non-crisis Periods
2.1 Geological Studies
It is essential to carry out extensive geological investigations of potentially active
volcanoes during periods when those volcanoes are in repose. Studying a volcano’s
eruptive record enables scientists to reconstruct how each volcano has erupted in the
past. From this information, it is possible to ascertain the types and magnitude of
hazards posed by the volcano, and determine how frequently active the volcano is.
This information is fundamental, and is always the starting point when planning and
preparing for a future eruption.
2.2 Planning
During periods when volcanoes are not active, planning and preparation should be
undertaken to ensure the effects of a volcanic eruption are minimised. In the Mount St.
Helens eruption, the value of planning was one of the strongest lessons learnt by those
involved. Planning is important at national, regional, local and even individual levels
(Saarinen and Sell, 1985).
The following aspects should be considered when planning for a volcanic eruption.
•
Land use development and regulation to prevent development in zones that are of
high risk to volcanic hazards (Johnston and Houghton, 1995).
•
Where thick ash fall is likely to occur, building codes that require roofs to have
steeper pitches could be implemented (Spence et al., 1996; Johnston, 1997a).
This is especially important for critical buildings such as hospitals, fire stations,
police stations, public buildings and schools (Johnston, 1997a).
•
Plans must be established regarding procedures during a volcanic eruption. Plans
may need to detail procedures for notifying the public about the eruption,
procedures for shutting down operations and maintenance and clean up
procedures (Federal Emergency, Management Agency, 1984; Johnston, 1997a;
1997b). Recovery planning should also be considered within the contingency plan
(Johnston, 1997a).
•
Plans and procedures need to be flexible enough to adapt to what may be rapidly
changing conditions during a volcanic eruption (Peterson, 1996; Johnston 1997a).
•
Sample emergency ordinances should be prepared in advance (FEMA, 1984).
•
Johnston (1997a) suggests making a list of facilities that must be kept operative,
versus those that can be shut down during and after ash fall.
•
It is advisable to consider the need for stress counselling both for the general public
and emergency workers (Finnimore et al., 1995).
•
Pre-test the plan so that people know what roles they must fulfil (FEMA, 1984).
•
The 1996 Mount Ruapehu eruptions confirmed that the preparedness of a district is
based on past experiences. As a result of the 1995 eruption experience,
organisations were able to respond quickly and more effectively. It is important to
pass on information about lessons learnt from past eruption experiences to new
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staff in the organisations, so that they too can use that information effectively (Neild
et al., 1998).
• Evacuation
Evacuation may be necessary in the event of a volcanic eruption. Near to the source
of the eruption it may be advisable to evacuate the area prior to activity in order to save
lives. It is also important to note that heavy tephra falls may cut off transport routes
after the eruption, thus hindering any effort to evacuate people (Johnston and Nairn,
1993).
There is a need to plan for the transportation, sheltering, feeding, clothing and medical
and hygiene needs of any evacuees or those that are stranded by an eruption. In the
event of a volcanic eruption there may be a large number of displaced people that need
to be cared for, and pre-planning will mean that those people have places where they
can stay (FEMA, 1984; Johnston and Nairn, 1993; Finnimore et al., 1995).
Before an eruption, it is necessary to identify resources that can be used to assist in
the evacuation of large numbers of residents. For example this may include towing
firms, mechanical repair firms, emergency fuel supplies and bus companies. Other
issues that should be considered include the control of traffic, and animal transport and
welfare. The early identification of needs during a volcanic eruption will allow ready
arrangement of outside assistance when an eruption occurs (Environment BOP, in
prep).
• Spare Parts
Spare parts or critical equipment that may be needed during a volcanic eruption should
be stockpiled. This may include air filters, cleaning equipment, protective clothing, face
masks and extra fire hoses (Novak et al., 1981; FEMA, 1984; Johnston, 1997a). Extra
vehicles for emergency use by police and other personnel may also be required
(FEMA, 1984).
• Education
Education of the public about volcanic hazards and how to mitigate against the effects
of a volcanic eruption is important. Education will lessen the physiological and physical
impacts of an eruption on the public. Warnings can be better understood if the public
understands the nature of the hazard. Also, since communications may be disrupted
during and after an eruption, it is necessary to distribute information before an event so
people know what to expect and what to do (Johnston and Nairn, 1993).
The public can be educated through newspaper articles, television, radio, the Internet,
exhibits at museums, brochures, talks by scientists to clubs and organisations and
school classes. Education about volcanic hazards aimed at school children has the
added benefit that parents become informed too, through their children (Peterson,
1996).
Table 1 summaries what the public needs to know about volcanic hazards and outlines
some techniques in disseminating hazard information.
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Table 1: Educating the public about volcanic hazards (after Gregory 1995;
Peterson, 1996; Voight, 1996).
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What the public
needs to know
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Basic information about volcanoes in general, and the volcanoes in
their area. (This may include their shape, size, places from where
eruptions have issued and common types of eruption in the past. Also
it may be useful to provide some facts about particular eruptive events
such as size violence, volume of ejecta, areas affected and how often
eruptions have occurred).
Successive eruptions at the same volcano can have great variations in
style, size and violence.
Time intervals between eruptions can vary widely.
Neighbouring volcanoes may differ greatly from one another in their
eruptive habits and characteristics.
Science has capabilities, but it also has limits too.
Some volcanic unrest ends without an eruption.
People need to know the time frames that apply to different statements
about possible future activity.
Practical measures for personal protection and mitigation of volcanic
hazards.
The Volcanic Hazards Information Series published by IGNS is an example
of an education campaign that incorporates most of the features mentioned
above.
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Techniques for
relaying the
message
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Provide concrete personalised information (“personalise the risk”) so
that the public understand that volcanic risk applies to them (for
example, mention specific locations).
Information must come from, and be relayed by a credible source.
Accurate and clear information should be provided.
Messages should be presented with confidence and conviction.
Repeat the message to provide consistent reinforcement (confirmation)
and to reach a broader population.
Use a range of communication channels including printed media,
electronic media and personally delivered messages.
• The Media
Most people rely on the media for receiving information. Surveys by Johnston et al.,
(1997) show that public knowledge and awareness of events during the Ruapehu
eruptions were derived almost entirely from the media.
Effective management of the media is required so that accurate information can be
conveyed to the public during a volcanic eruption. In a recent survey of organisations
by Paton et al. (1998), 43 percent of respondents reported that they had suffered
“media problems” during the 1995 Ruapehu eruption. These results highlight the need
for organisations to develop an effective media response, and to provide training for
media spokespersons. Paton et al. (1998) suggest addressing this problem by
including a media management component in training programs.
The increased public demand for information during a volcanic eruption may be
supplemented by distributing printed information (Johnston, 1997b).
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• Networks
The FEMA (1984) recommend that prior to a volcanic eruption, roles and
responsibilities of the different organisations should be defined, and a network of
authority under which individuals would work in an emergency should be established.
In the survey of organisations by Paton et al. (1998), it was found that many
respondents believed there was a “lack of clear responsibility for co-ordination” over
the duration of the 1995 Ruapehu eruptions. There is therefore a need to establish
inter-organisational networks among those organisations that may be involved in
dealing with a future volcanic eruption. Paton et al (1998) suggest that more
simulations and exercises would help identify and resolve co-ordination problems.
Another recommendation was for groups to work together in the planning stage to
develop their capability to work as an integrated team (Paton et al., 1998).
A volcanic eruption may cover more than one local authority, and a shift in wind
direction may even change the entire area of impact. Because volcanic eruptions
cover wide areas, a nationally co-ordinated effort could reduce duplication. Neild et al.
(in prep) suggest that this is particularly true for providing information to the public and
media. However, concerns have been expressed over how Emergency Management
Groups would function without local knowledge if co-ordination were controlled from an
outside centre (Neild et al., in prep).
2.3 Scientific Alert Levels and Science Alert Bulletins
The New Zealand Scientific Alert Levels (Appendix 1) are used to determine different
levels of volcanic unrest. The system is numbers based and ranges from zero
(volcano in a dormant state) to five (large hazardous eruption in progress). There are
two scales – one for frequently active volcanic cones, and one for re-awakening of
dormant volcanoes.
A dual system is necessary, as the different types of activity require different
responses. The Scientific Alert Levels are useful for organisations as they can pre-plan
for different responses depending on the level that a volcano has been assessed at
(Johnston, 1997a).
Science Alert Bulletins are issued by IGNS during volcanic eruptions, and provide
information on the status of a volcano. The Science Alert Bulletins are useful because
they contain information regarding the scale of the activity, highlight developing or
expected problems, and may contain predictions about activity. The information
contained in a Science Alert Bulletin may allow organisations to put response plans into
effect before being overwhelmed by a volcanic eruption (Johnston, 1997a).
2.4 Monitoring
Within New Zealand, monitoring of all our active volcanoes takes place. Volcano
surveillance enables scientists to note any changes to a volcano, and if possible
provide warning of an impending eruption. At this stage, appropriate steps can then
be taken by organisations to reduce the risk to lives and property (Scott et al., 1995).
Three main types of monitoring are undertaken in New Zealand. The first technique is
monitoring of volcanic earthquakes. There are five volcano seismic networks in
operation around New Zealand. There are networks situated at Tongariro, Taupo and
in the Bay of Plenty and these are monitored by IGNS. The other two networks are
located in Auckland and Taranaki and are monitored by the relevant regional council
(Scott et al., 1995).
Measurement of ground deformation is a second monitoring method used on New
Zealand volcanoes. Measurement of ground deformation can be done in a number of
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Measuring distances with electric distance measuring equipment (EDM).
Ground tilting measurements are made by precise levelling and using some of the
volcanic lakes as large scale, natural spirit levels (Scott et al., 1995; Scarpa and
Gasparini, 1996).
Horizontal control surveys using triangulation and trilateration techniques (Scott et
al., 1995).
Global Positioning Surveys (GPS) can be used to measure horizontal and vertical
earth shifts (Scott et al., 1995; Scarpa and Gasparini, 1996). Two GPS receivers
have recently been installed at Mount Ruapehu to try and detect ground
deformation. Previously, plotting land deformation on Mt Ruapehu has been
difficult, but if the GPS receivers prove to be successful more will be installed
further up the mountain, closer to the crater (Hurst, 1998).
Changes in gas chemistry, the rate of gas emission from craters and the chemistry of
crater lake and thermal spring waters can also be used to detect changes in a volcano.
Other evidence of unrest can also be detected from changes in groundwater, lake
levels, rate of stream flow and water temperature (Scott et al., 1995; Giggenbach,
1996).
2.5 Satellite Remote Sensing
Satellite remote sensing can be used successfully to detect changes in active
volcanoes before they erupt. Infrared detectors can detect changes in the temperature
of the volcano. As magma moves to the surface a volcano will get hotter. Crater lakes
will also heat up before an eruption. Both of these types of changes can be detected
using infrared remote sensing (Oppenheimer, 1993; Oppenheimer, 1997).
The
amount of swelling or deflation of a volcano can also be determined by looking at
changes in topography. This is done using a technique called SAR interfermometry
(Oppenheimer, 1997).
Satellite imagery can be used for mapping geology, and it can also be used to detect
morphological features in a fashion similar to air photography. Both of these
applications are useful in hazard assessment (Oppenheimer, 1997).
After a volcanic eruption has occurred, satellite data can be used to monitor the ash
cloud that is produced (Francis et al., 1996; Oppenheimer, 1997). Satellite remote
sensing was used to detect and track clouds from Mount Pinatubo in 1991 (Casadevall
et al., 1996). The eruption cloud can be tracked on successive satellite images, and
the horizontal spreading velocity of the plume can be established. From this
information it is possible to predict whether the ash cloud will reach populated areas,
and if so, when. The height of the eruption cloud can also be determined by using
satellite imagery. Determination of cloud height is important for aviation hazard
mitigation (Oppenheimer, 1997).
Mount Ruapehu eruption clouds were tracked using an Advanced Very High Resolution
Radiometer (AVHRR) during the 1995-1996 eruptions (White and Hockey, 1996).
Unfortunately several problems were encountered that limited the usefulness of the
images:-
The eruptions were short-lived and generally did not coincide with satellite
overpasses;
Many of the eruptions that occurred were obscured by cloud cover; and
AVHRR could not be used to measure the water temperature of Crater Lake as the
lake is too small.
As a result of these restrictions, the monitoring of Mount Ruapehu was mostly
dependent on field data and aircraft observations (White and Hockey, 1996).
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Ground based radar can also be used to track drifting volcanic clouds. Radar can
determine the height of the eruption cloud and the structure of the cloud. Portable
radar are useful as they can be moved around depending on where an eruption has
occurred. Doppler radar systems can sense particle size distribution in a volcanic
cloud (Rose and Kostinski, 1994).
Massive releases of sulphur dioxide from eruptions can be determined using the Total
Ozone Mapping Spectrometer (TOMS). Measurement of volcanic aerosols can also be
undertaken using remote sensing techniques (Francis et al., 1996; Oppenheimer,
1997). It is important to measure these as they are relevant to circulation, radiative
energy balance and chemical processes in the atmosphere. Volcanic aerosols can
have a climatic impact, and this was demonstrated after the Mount Pinatubo eruption in
1991 (Oppenheimer, 1997).
A summary of the applications of remote sensing to volcanology can be seen in
Figure 3.
AEROSOLS
- concentration /mass
- size distribution
VISIBLE
AIRBOURNE ASH
- cloud height / position
- ascent rate / tracking
- concentration / mass
VISIBLE, IR
SO2
- concentration / mass
UV, MICROWAVE
ACTIVE LAVA
- temperature
- heat flux
- morphology / texture
VISIBLE, IR,RADAR
TOPOGRAPHY
- static
- ground deformation
VISIBLE (STEREO), RADAR
POST-DISASTER
RECONNAISSANCE
- impact on society
VISIBLE, IR,RADAR
CRATER LAKES
- colour
- temperature
- heat flux
VISIBLE, IR
MAPPING
- lithology
- new ash / lava
- land cover
- morphology / texture
VISIBLE, IR, RADAR
Figure 3: Summary of the applications of remote sensing for volcanology
(after Oppenheimer, 1997).
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3
During an Eruption: A Description of
Different Volcanic Hazards and
Mitigation Measures for those Hazards
3.1 Tephra Falls
Ash has erupted volcanic material that is less than 2 mm in size. Ash particles are
small enough to be carried by the wind, and therefore the areas where ash is deposited
are determined by how high the ash is carried into the atmosphere, and the direction
and strength of the wind at the time (Figure 4). During a major eruption, very large
areas can be affected by tephra fallout (Blong, 1984). Pumice lapilli is erupted pumice
material that ranges from 2 to 64 mm. Pumice lapilli may also be spread over a
significant area during a pyroclastic eruption.
Figure 4: Ash from Mount Ruapehu carried by southeasterly winds over
Lake Taupo during the 1995-1996 Ruapehu eruptions.
Ash rarely causes direct damage, but instead accumulates and causes structures (for
example, buildings, tree branches, electricity lines and telephone lines) to collapse
(Blong, 1984; Houghton et al., 1988). Ash particles may carry a film of corrosive acid
and this causes corrosion on metallic surfaces (Houghton et al., 1988). Ash is
abrasive, and can be conductive especially when wet (Labadie, 1983).
Danger exists where large pumice lapilli have not reached thermal equilibrium before
impact. The impact temperatures of the lapilli may be high enough to ignite a variety of
materials at considerable distances (Blong, 1984).
The hazardousness of ash fall may be influenced by a number of other factors
including whether the ash is wet or not, and the grain size of the ash (Blong, 1984;
Houghton et al., 1988). When ash is wet, it is very heavy and causes buildings and
other structures to collapse sooner than those covered in dry ash. A finer grain size of
ash may represent a greater hazard than coarser grain sizes (Blong, 1984). Finer grain
sizes will penetrate machinery and other human structures more readily. Also, fine
grained ash becomes cohesive when wet, resulting in crusting of ash layers which
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Page 9
causes increased rain run-off (Blong, 1984). Toxic fluorine compounds are also
concentrated on fine grained particles (Thorarinsson, 1979; Blong, 1984).
3.1.1 People
Respiratory problems, eye irritations, skin irritations (“ash rash” or “acid rash”) and
stress reactions will be experienced by people in the event of ash fallout (Blong, 1984).
As well as experiencing minor respiratory problems, it is possible to encounter serious
respiratory problems as a result of breathing in falling ash. Chronic bronchitis,
pneumovolconiosis or silicosis can be contracted from breathing in ash. Silicosis is a
lung disease resulting from the inhalation of fine particles of free crystalline silica which
have toxic effects on the lungs causing fibrotic changes. For silicosis to develop the
victim must be exposed to crystalline quartz (quartz, cristobalite or tridymite) of a
respirable range (that is, less than 10 microns) (Blong, 1984).
During the Mount St. Helens eruptions of 1980 it was noted that while many people
developed medical problems that were directly related to the ash fallout, there was also
a rise in ash-related accidents. For example, motor vehicle accidents and falls from
rooftops increased during the period that ash was present (Blong, 1984).
3.1.2 Agriculture and Horticulture
A large area of New Zealand is utilised for agriculture and horticulture and is especially
vulnerable to the effects of volcanic activity. While heavy ash falls would be disastrous,
even light ash falls of less than 5mm would cause problems for livestock (Neild et al,
1998).
Ash that falls on pasture or in drinking troughs can affect the health of grazing animals
(Gregory and Neall, 1996). Food will be scarce where ash fall has been heavy, and
animals may require supplementary feed.
Volcanic ash poses a pneumoconiosis risk for animals, as it does for humans. In rare
cases, tephra can also cause asphyxiation during heavy ash falls with the formation of
an obstructing plug of ash and mucus in the upper respiratory tract (Gregory and Neall,
1996).
Where tephra falls have been light, ash is easily ingested by grazing animals. As
fluorine coats fine ash particles readily, animals at a distance from the erupting volcano
may ingest ash that is coated with fluorine and as a consequence contract fluorosis
(Thorarinsson, 1979). Signs of poisoning include lesions in the nose and mouth, and
hair falling out around the mouth (Thorarinsson, 1979; Gregory and Neall, 1996). In
extreme cases, especially where animals are “at risk” (for example, pregnant or
lactating), deaths may occur. If ash falls were thick and widespread, significant stock
losses could be expected.
Fluorine may also find its way into water courses. If fluorine covered tephra is rained
on, or if the tephra lands on wet ground, then the fluorine may be leached out (Gregory
and Neall, 1996).
Animals could also suffer complications, such as polioencephalomalacia in sheep or
the development of copper deficiency, from eating excessive amounts of sulphur
(Gregory and Neall, 1996).
If vegetation is destroyed by a volcanic eruption, fish may be killed as a result of the
increased water temperature in the river. Fish may also be killed by suspended
sediments, higher acidity and higher concentrations of fluorine in water bodies after an
eruption. Aquatic floral and faunal populations are also susceptible to ash suspended
in rivers or lakes (Neild et al., 1998).
If there are widespread ash falls, birds may die from a lack of food. Gases may also kill
birds near the vent area. Insects are particularly susceptible to ash, as the epicuticular
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wax layer is abraded by ash particles which causes rapid desiccation and death (Cook
et al., 1981; Neild et al., 1998).
Tephra falls from an eruption would have both physical and chemical effects on
horticulture (Neild et al. 1998). Table 2 shows the impacts on plants and soil from
increasing thicknesses of ash.
Table 2: Impacts on plants and soil from increasing ash thickness (after
Folsom, 1986, and Blong, 1984; in Neild et al., in prep).
Ash Thickness
Thin Burial
(< 5mm tephra)
Moderate Burial
(5-25 mm tephra)
Impact on Plants and Soil
-
Thick burial
(25-150 mm tephra)
-
Very thick burial
(>150 mm tephra)
-
No plant burial or breakage.
Ash is mechanically incorporated into the soil within one year.
Vegetation canopies recover within weeks.
Buried microphytes may survive and recover.
Larger grasses are damaged but not killed.
Tephra layer remains somewhat intact on the soil surface after one
year.
Soil underneath remains viable and is not so deprived of oxygen or
water that it ceases to act as a topsoil.
Vegetation canopies recover within next growing season.
Complete buries and eliminates the microphytes.
Small mosses and annual plants will only be present again in the local
ecosystem after recolonisation.
Generalised breakage and burial of grasses and other non-woody
plants.
Some macrophytes of plant cover do not recover from trauma.
Large proportion of plant cover is eliminated for more than one year.
Buried soil is revitalised when plants extend roots and decaying
organic matter from the surface of the tephra layer down to the top of
the buried topsoil and affect an integration of the tephra and buried A
horizon. Generally accomplished in four to five years.
Vegetation canopy recovery takes several decades.
all non-woody plants are buried.
Burial will sterilise soil profile by isolation from oxygen.
Soil burial is complete and there is no communication from the buried
soil to the new tephra surface.
Soil formation must begin from a new “time zero”.
Several hundred (to a few thousand years) may pass before new
equilibrium soil is established.
The time of year, or stage of plant growth, will also affect the impact of ash fall on
vegetation. For example, a thin layer of tephra deposited in the growth season may do
more harm than a thicker layer deposited in other seasons (Thorarinsson, 1979).
Volcanic dust may also affect pollination time. The dust may impede the transfer of
pollen to the receptive parts of the flower, resulting in fewer fruit set and smaller
deformed fruit (Neild et al., 1998). The following table (Table 3) shows the stage that
each crop is most at risk.
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Table 3: Periods of high crop risk from ash (after MAF, 1995; Neild et
al.,1998).
Crop
Pea
Squash
Tomatoes
Sweetcorn
Pipfruit
Stonefruit
Kiwifruit
Grapes
Grains
Evergreen
perennial crops
Maize
Period at Risk
From emergence until the end of flowering.
During the initial stages of growth and flowering.
During seed emergence and flowering stages.
During the early stages of growth.
Has three danger periods:- blossom where severely acidic ash (pH less than 3) could burn plant tissue
and result in poor pollination;
- 6 to 8 weeks after blossoming, when the skin of the
- fruit is particularly sensitive; and
- later stages of development when fruit is prone to cosmetic blemishing.
Stone fruit is also susceptible at the same times as pipfruit, except that the
early fruit development period is four to six weeks after blossoming, when
sensitive fruit skins could be damaged, and show russet or deformation in
severe cases.
Kiwifruit is also at risk at, and six to eight weeks after, blossom. There would
also be a problem at harvest time. As kiwifruit cannot be washed prior to
packing, the hairy nature of the fruit would make ash removal very difficult.
Grapes have three main periods when damage could occur:- flowering, when acidic ash could burn plant tissues, reduce pollination and
reduce bunch fill;
- fruit development, where ash deposits would block sunlight and reduce
quality; and
- harvest, where ash deposits would be a contaminant with the extra acidity
of the ash possibly having a significant impact on wine quality. Ash would
have to be removed prior to harvesting by washing and allowing bunches
to dry.
Ash showers near maturity will make harvesting difficult and reduce the quality
of the grain.
(For example, avocado and citrus) Susceptibility is more uniform throughout
the year due to their persistent foliage cover.
The critical period for maize yields is three weeks before tasselling to two
weeks after pollination. Even light falls over this period could result in barren
stalk and crop failure.
During the Mount St Helens eruption, it was found that ash that had fallen on apple
leaves reduced photosynthesis by up to 90 percent. Peaches and raspberries could
not be cleaned of volcanic ash easily and as a result a significant percentage of the
crop could not be sold. Near mature blueberries were damaged by the salts in wet
ash. Ash covered the leaves of strawberry plants and compressed the fruit to the soil
surface, where conditions for infection and decay were ideal. In many cases, while the
ash that fell did not cause disease, it contributed to creating an environment that
disease could thrive in (Cook et al., 1981).
A layer of ash on the ground surface will lower permeability to air, water and water
vapour. Ash may also abrade horticultural or agricultural machinery (Cook et al.,
1981). Plant survival may be influenced by the weight of ash on the leaves. For
example, plants such as lucerne or peas have delicate leaves and stems, and these
may be easily damaged by the weight of the fallen ash. As well as damaging leaves
and stems, volcanic ash cancause significant physical damage to fruit (Neild et al.,
1998).
Pest species are not as prone to volcanic dust as their predators, and therefore after a
volcanic eruption there may be an increase in pests (Cook et al., 1981; Neild et al.,
1998).
Ash suspended in the atmosphere may cause a reduction in temperatures, and affect
horticulture. Horticultural crops may be stunted or may fail completely. As a result of
volcanic dust in the atmosphere from the eruption of Mount Pinatubo in 1991, New
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Zealand temperatures were reduced by 1-2°C. This temperature reduction retarded
plant growth and productivity declined (Neild et al., 1998).
If an eruption were to occur near Taupo or Rotorua, then major forest fires in the pine
plantations could occur due to ignition by pyroclastic flows or hot falling tephra (Hawkes
Bay Civil Defence Organisation, 1994; Neild et al., 1998). Breakage of tree branches,
and burial of trees could also occur if eruption deposits were thick enough. Coping with
problems such as forest fires would be made even more difficult if the infrastructure
was also damaged (Neild et al., 1998).
3.1.3 Building Structures
When ash accumulates on the roofs of buildings, building collapse is dependent on the
slope of the roof (the lower the angle of the roof, the more likely roof collapse will
occur), the amount of ash accumulated on top and whether the ash is wet or dry (Blong
1981, Johnston, 1997a).
Roof collapse will occur when there has been an
accumulation of between 100 and 300 mm of dry ash. Only a small number of roofs
will collapse with an ash thickness of 100 mm, but as the thickness of ash increases,
the incidence of building collapse also increases. It has also been noted from past
eruptions that wide-span roofed buildings have a tendency to collapse more quickly
than short span domestic scale construction (Johnston, 1997a).
Ash may infiltrate structures and cause damage to materials and equipment inside
buildings. Exterior surfaces on buildings, particularly those parts that remain unwashed
by normal rainfall, will also suffer damage from the effects of volcanic ash and acid
rain. Metallic surfaces are especially vulnerable and may corrode due to the acidity of
the ash and rain that falls (Johnston, 1997a).
3.1.4 Electricity
The most common effects of volcanic ash on electricity distribution systems include
insulator flashover, electricity outages, and line breakage (Stemler and Batiste, 1981;
Johnston, 1997a).
Insulator flashover can be caused by volcanic ash and will result in outages to the
electricity supply. Ash that is dry causes no immediate flashover problems. However,
ash particles that have a soluble coating and have also been moistened are highly
conductive and can cause insulator flashover. Ash is moistened either by falling rain,
or from water present in the eruption plume (Federal Emergency Management Agency
(FEMA), 1984; Johnston, 1997a).
As well as
flashover.
vulnerable
and water
the state of the ash, the size and dimension of an insulator may also affect
For example, lower voltage insulators with smaller weather sheds are more
to flashovers due to the fact that they are more prone to exposure from ash
(Sarkinen and Wiitala, 1981).
After ash fall has occurred, controlled electricity outages are necessary to clean ash
from affected parts of the electrical system. Another problem is line breakage, and this
occurs when the weight of ash collected on power lines becomes too great (Johnston,
1997a).
In addition, Johnston (1997a) also notes a number of other problems associated with
volcanic ash and the electricity supply. These are:Ash contamination on insulators and conductors increases corona activity which in turn
causes increase in audible noise (around 10-15 dB) and radio interference.
•
•
Volcanic ash will abrade and clog mechanically moving parts used in the electricity
system.
Saturated volcanic ash on ground surfaces has the potential to be hazardous due
to its conductivity.
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•
Tree limbs that are laden with wet ash may fall on electricity distribution lines.
3.1.5 Water Supply
Ash may affect the water supply by causing an increase in the turbidity and acidity of
the water (Johnston and Houghton, 1995; Johnston, 1997a). Small bodies of water,
such as roof water tanks and drinking troughs, may also be contaminated by ash
leachates, rendering them undrinkable (Johnston, 1997a). At water treatment plants,
ash may cause wear and tear on equipment, and may also short circuit electrical
equipment (FEMA, 1984). Another problem regarding ash and the water supply, is that
an increased demand for water resources may occur as water is used to clean up after
the volcanic eruption (FEMA, 1984, Johnston, 1997a).
3.1.6 Wastewater Networks (Stormwater Drainage and Sanitary
Sewers)
Ash, especially of a fine grain size, is easily washed into storm water systems by
rainfall or via the clean-up process. Because ash has a high density, it is not held in
suspension in the wastewater but instead accumulates easily causing pipe blockages
and local flooding. Very fine ash or pumice (which is low density) may be transported
to sewage treatment plants, and this will result in damage to the plant (Johnston,
1997a).
3.1.7 Sewage Treatment Plants
Johnston (1997a) cites a number of problems that may be experienced at sewage
treatment plants. These include:• Ash may cause damage to milliscreens, mechanical grit and sludge removal
systems, comminutors and other equipment.
• Ash falling into sedimentation tanks will add to the volume of material to be
removed.
• Ash entering oxidation ponds or biofilters will tend to halt the oxidation process until
the ash settles out or is removed.
• Ash may affect the acidity or toxicity level of effluent to such an extent that
beneficial bacterial growth may be damaged or lost.
3.1.8 Gas
Gas supplies are not significantly affected by ash falls as most pipes are located below
ground and are protected from the ash. Gas facilities above ground such as above
ground-pumping stations, pressure reduction facilities, pipeline bridge crossings and
gas meters, may suffer ash-related damage (Johnston, 1997a).
3.1.9 Transportation
• Motor Vehicles and Road Transport
Ash reduces visibility for road vehicles. Ash clouds are stirred up by moving traffic,
making it difficult for drivers to see (FEMA, 1984; Johnston, 1997b). When ash is wet
it causes problems to moving vehicles, as the surface becomes slippery to drive on
(FEMA, 1984; Johnston, 1997a). Ash can clog vehicle air filters, and can cause wear
to moving parts due to its abrasiveness (Hawkes Bay Civil Defence Organisation,
1994; Johnston and Houghton, 1995; Johnston, 1997a). Ash that fills roadside ditches
and culverts may prevent proper drainage and cause erosion on the shoulder of the
road (FEMA, 1984).
• Rail Transport
Decreased visibility due to stirred up ash is a problem for the rail system. Rail crews
may also suffer from breathing problems due to the suspended ash. Ash may cause
wear to moving parts of the train, and if the ash is wet it may lead to short-circuiting of
signal equipment (Johnston, 1997a).
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In the Mount St. Helens eruption it was found that rail transport fared better than
automobile or air transport. Only minor train slow-downs were required and some rail
equipment suffered ash-related problems (Schuster, 1981).
• Aircraft and Airline Travel
Aircraft and the airline industry are also prone to falling ash. On the ground, aircraft
and aerospace equipment may be contaminated by falling ash (Labadie, 1983). In the
air, temperatures of jet engines are hot enough to melt ash and thus effect the engine,
causing it to lose power. Ash cannot be detected by aircraft radar, so aircraft exclusion
from particular areas of potentially hazardous airspace is common. Even where ash
fall is minor, or there is simply the potential of ash fall, it may result in the closure of
airports (Labadie, 1994).
3.1.10 Communications
Ash fall may cause direct damage to communication systems, or have indirect effects
on them. For example, a particular communication system may not be operable
without electricity (Johnston, 1997a).
Interference to radio waves may occur due to large quantities of electrically charged
ash in the atmosphere. Telephone systems may also be affected by ash falls. Ash
entering telephone exchanges can cause abrasion, corrosion and conductivity damage
to electrical and mechanical systems. The switching gear at telephone exchanges
needs to be kept below critical temperatures, so exchanges with external airconditioning systems are vulnerable to overheating if these units fail due to ash
ingestion, or need to be switched off. Another problem that telephone systems may
experience is overloading, due to the increased demand by the public and emergency
services in response to an eruption (Johnston, 1997a).
3.1.11 Mechanical, Electrical and Electronic Equipment
Due to volcanic ash being abrasive, corrosive and conductive, it can cause problems
for mechanical, electrical and electronic equipment. Air-conditioning units can become
blocked and damaged by volcanic ash. Short-circuiting and fires can occur in electrical
equipment, and ash can cause wear on motors (FEMA, 1984). Computers are also
vulnerable to volcanic ash.
3.2 Mitigation Measures for Tephra Fallout
3.2.1 People
If possible, the best measure to guard against inhalation of ash particles is to stay
indoors. If it is necessary to leave the shelter of a building then the best protective
measure against suspended ash is to wear a face mask when out of doors (Blong,
1984, FEMA, 1984). If a face mask is not available then a wet cloth held over the face
will act as a makeshift mask. Those people that are likely to be heavily exposed to ash
(for example, outdoor workers) should ensure that they have adequate breathing
protection (Blong, 1984). To avoid eye irritations caused by ash particles, contact
lenses should not be worn (FEMA, 1984).
3.2.2 Agriculture and Horticulture
In the 1995-1996 eruptions from Ruapehu volcano there were some stock deaths from
fluorosis poisoning due to low levels of fluorine in ash deposits (Cronin et al., 1998).
Another cause of stock deaths was from stock ingesting ash when the ash covered
feed. Cronin et al., (1998) suggest mitigation measures to combat these problems. To
reduce stock losses from fluorosis poisoning, it was advised to supply supplementary
feed to at-risk pregnant or lactating animals following tephra fall. It was also suggested
to move stock or supply supplementary feed to stock to avoid the animals ingesting
ash.
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To avoid animals drinking contaminated water, water troughs should be emptied and
refilled with uncontaminated water.
In regards to horticulture, Neild et al. (1998) suggest that a “prompt determination of
the physical (e.g. particle size) and chemical (composition and reactivity) properties of
ash from an actual event will help to predict its effects and guide mitigation or
rehabilitation strategies”. Other mitigation suggestions include:
-
Relocate beehives to assist hive survival.
For cauliflower, break a leaf over on each plant to shelter the white curd.
Horticultural machinery will require maintenance.
Stock up on fungicide sprays and/or pest control sprays.
Remove ash from leaves.
Where ash falls have been around 5-25 mm, clear ash from the base of trees to
prevent plant disease or death from crown rots fostered by the contact of damp ash
with the trunk.
It may be possible to mix thinner layers of ash into the topsoil.
Under evergreen trees there may be less ash underneath the trees than in
surrounding areas. It may be worthwhile to thin out the ash by spreading some
underneath the trees.
Where plants have been partially defoliated, fruit should be thinned to better align
leaf resource to fruit numbers. Applying fertiliser will also promote the growth of
new leaves (Neild et al., 1998).
Nairn (1991) suggests that ventilation systems for crops grown indoors will need to
have filtering systems installed to reduce the amount of ash entering the structures.
3.2.3 Building Structures
Roofs of buildings should be cleared of ash immediately so that ventilation systems can
be reactivated, and streets can be cleaned without any risk of being re-contaminated
by ash reworked from roofs. Roof collapse is also a possibility if ash is left on the roof.
The best way to remove ash from a roof is to lightly dampen the ash with water and
then sweep the ash off (FEMA, 1984).
It is advisable not to sweep the ash off in a dry state as this will cause it to billow up
into a cloud. Wetting the ash completely is also not advisable, as this may induce roof
collapse due to additional weight.
When removing ash from roofs care should be taken not to wash the ash into drains,
downspouts and soak holes as it will clog pipes and seal up wells (FEMA, 1984).
Johnston (1997a) suggests that where communities are exposed to 100 mm or more of
ash fall, they would be evacuated before the climactic phase of the eruption. Those
people that are unable to be evacuated should take shelter in buildings with steep
pitched roofs, or at least avoid wide-span roof structures (Johnston, 1997a).
3.2.4 Electricity
To prevent widespread power outages it is necessary that all surfaces in the electrical
system be cleaned immediately after ash fall. Dry ash should be cleaned by airblasting
or brushing the affected surface (Stemler and Batiste, 1981; Labadie, 1983; Johnston,
1997a). Wet ash is more difficult to remove. It should be cleaned off either with water
at high pressure or by hand (Stemler and Batiste, 1981; FEMA, 1984). To decrease
the chance of insulator flashover insulators should be washed from the bottom upwards
to remove as much ash as possible (FEMA, 1984; Johnston, 1997a). Cleaning and
protection of the electricity system should be continuous until the threat of windblown
ash is over (FEMA, 1984).
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3.2.5 Water Supply
Johnston (1997a,b) suggests a number of mitigation measures regarding ash and
water supplies (Table 4).
Table 4: Mitigation measures for volcanic ash and the water supply (after
Johnston, 1997a, 1997b).
-
Mitigation measures for
the general water
supply
Mitigation measures
where the water comes
from a tank on a roof
Water supply intakes should be closed before turbidity and acidity
levels become excessive.
-
Vulnerable plant equipment and pumps should be covered when
ash fall is impending.
-
High turbidity levels may be able to be managed if water
treatment filters are cleaned regularly. It is necessary, however to
be aware that they may become blocked. People should be
advised to boil water when turbidity levels are high, as suspended
ash may decrease the effectiveness of any disinfection or
flocculation process.
-
As fine ash can remain in suspension for long periods (days to
weeks) a coagulation-flocculating agent may need to be added.
Alum is found to be the best agent.
-
Regular monitoring is necessary to determine when the normal
water supply can be resumed.
-
There is the need for a water management plan to handle
excessive demands for water after an eruption. Reservoirs may
require filling and public information messages regarding water
conservation may need to be broadcast.
-
Disconnect the downpipes leading to the tank.
-
Cover open tanks.
-
Where downpipes have not been disconnected, do not use the
water until tests have been done to ensure that it is not toxic.
-
Where the roof supply is found to be non-toxic, but the turbidity is
high, boil water before drinking.
If no tests can be done, the water tank should be drained, flushed and
refilled with uncontaminated water.
3.2.6 Wastewater Networks (Stormwater Drainage and Sanitary
Sewers)
It is important to reduce the input of ash into stormwater systems and sanitary sewers
(Johnston and Daly, 1997). When washing ash off streets avoid washing it down the
drains and manholes of stormwater drains and sanitary sewers. Use protective
measures such as sandbags around manholes and drains, or weirs in the manholes to
trap the ash (Markesino, 1981; FEMA, 1984). When cleaning areas served by free
discharging or dry well storm drainage systems, use dry methods of removing ash (for
example, hand sweep ash out from the gutters) prior to flush cleaning. To avoid ash
entering wastewater networks, it is important to educate residents on the acceptable
methods of disposing of ash (FEMA, 1984).
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3.2.7 Sewage Treatment Plants
The key to preventing ash from entering a sewage treatment plant is to limit ash
entering the stormwater and sanitary sewer system.
Based on the eruption of Mount St Helens in 1980, FEMA (1984) made the following
recommendations regarding wastewater treatment systems:• Temporarily cover all mechanical equipment that might be exposed to ash fall.
• Where possible, place sandbags or other devices at the entrance channel to the
plant to trap ash. (This procedure requires frequent attention due to normal
settleable solids present in sanitary waste).
• Consider removing or bypassing the comminutor during the initial heavy flows of ash
into the plant.
• Frequently check the primary clarifier to prevent (a) damage to the sludge collection
mechanism and/or the digester sludge pumps and (b) the transference of ash to the
digester. Depending on the type of mixing employed in the digester, further damage
may occur in the sludge transfer pumps.
• To clear ash from individual sections of the treatment facility, bypass individual units,
or in extreme instances, make a complete plant bypass to a holding pond or lagoon.
• The effects of ash on the pH value of influent or effluent are not clearly understood.
Toxicity may occur in the plant effluent to the extent that the bacterial growth is
damaged or lost. At the first signs of distress on a biofilter, check and adjust the pH
level of the influent to the biofilter (FEMA, 1984).
3.2.8 Transportation
• Road Network
Speed restrictions or road closure may be necessary to combat visibility problems and
slippery road conditions caused by ash falls (FEMA, 1984). After the 1980 Mount St
Helens eruption a number of dust retardants were used successfully to control the ash
before it was removed. “Coherex” (an emulsion of petroleum resins), lignin sulphate
and rock salt were among those used to stabilise the dust (FEMA, 1984; Labadie,
1983; Johnston, 1997a). However, these dust control methods did not control heavy
ash deposits for a long period of time, and they were also expensive (FEMA, 1984).
The best method of removing ash from roads is to sprinkle the ash with water and
blade it to the side or middle of the road. The ash can then be picked up by belt or
front-end loaders. A power broom can be used or water flushed over the road to
remove the remainder of the ash (Labadie, 1983; Johnston, 1997a). Conventional
snow removal methods should not be used to remove ash off roads. Snow removal
methods only stir the ash up and cause it to resettle on the roadway (FEMA, 1984).
Where roads are made of gravel, try to avoid removing too much of the gravel off the
surface during the clean-up process. Additional gravel may be required to replace any
that is lost, and may also assist in stabilising any dust that cannot be collected. FEMA
(1984) recommended adding graded material of 5/8 inch to 0 in size and crushed to
standard specification, for dust control (FEMA, 1984).
Ash deposits should be removed from any catch basins as soon as possible or ash will
form a crust making it difficult to remove later on (FEMA, 1984).
• Motor Vehicles
Regular checks and maintenance of car parts are essential to preventing damage to
motor vehicles from volcanic ash. Checks and maintenance should be carried out on
vehicles after every two and a half to three hours of exposure to volcanic ash. If ash
enters the air filter and electrical equipment, it should be cleaned off using compressed
air of 30 psi or less. The outside of the car, engine and radiator should also be cleaned
daily, if necessary using water to flush the ash. After volcanic ash has ceased to fall,
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then a thorough inspection should be undertaken and repairs carried out (FEMA, 1984;
Labadie, 1983).
• Rail Transport
Like motor vehicles, regular cleaning and maintenance of trains and rail equipment is
necessary during periods of ash fall (Labadie, 1983).
• Aircraft and Airline Travel
It is necessary to apply flight restrictions when ash is falling, or when there is a
possibility of it being in the atmosphere (FEMA, 1984). Aircraft that are grounded
should, if possible, be kept free of volcanic dust. If aircraft have been exposed to ash,
then careful cleaning procedures are required to avoid damage to the aircraft
(Labadie, 1983; Labadie, 1994).
Runways should be kept clean as volcanic ash is easily re-entrained by the wind,
aircraft take-off and ground vehicle movement. The ash should be wetted down,
bladed to the sides of the runway and then picked up by belt or front-end loaders. The
remaining residue of ash should then be flushed away with water, or swept away.
Landing aids, air traffic control systems and ground equipment will also require periodic
cleaning, maintenance and monitoring (Labadie, 1983; Labadie, 1994).
Volcanic Ash Advisory Centres (VAACs) have been established to keep track of
volcanic activity in different parts of the world. A VAAC is situated in Wellington, New
Zealand and covers the South West Pacific region. VAACs collate information about
volcanic clouds and provide this information to aircraft that are in flight or to those who
are planning flights (Metservice, 1997; Mayberry and Rose, 1998).
3.2.9 Mechanical, electrical and electronic equipment
To clean volcanic ash from electrical equipment, the equipment should first be switched
off and then blown clean with an air compressor at 30 psi or less (FEMA, 1984).
The best way to protect electronic equipment when there is ash falling is to discontinue
use of the equipment and protect it by covering it up or sealing it off. If the equipment
still needs to be used, then the next best option is to restrict access to the equipment
and ensure those that use it clean their clothing before entering the room in which it is
contained (FEMA, 1984). Continual protection and cleaning of computer systems
should ensure that they can continue to be used (Labadie, 1983).
Prior to, and while ash is falling, air-conditioning systems should be shut down. When
the ash has stopped falling, the air-conditioning intake and filters should be cleaned
before the system is reactivated (FEMA, 1984).
3.2.10 Ash Disposal
An important consideration after ash removal is the disposal of the unwanted ash. Ash
should be disposed of in areas where it does not constitute a hazard, and where it is
acceptable to the adjoining property owners. It is necessary that disposed ash is
stabilised so that it does not blow away from the disposal site. Ash can be stabilised by
covering dump sites with a blanket of heavy material such as gravel, growing
vegetation on the area or using straw and other mulching materials on the site (FEMA,
1984). Ash should not be disposed of in the garbage as it will cause damage to the
runners on the inside of garbage trucks (Johnston, 1997b).
3.2.11 Detailed Mitigation Measures
More detailed information on mitigation measures for ash fall is contained in Appendix
II.
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3.3 Ballistic Fallout
Ballistic fallout occurs when projectiles of rock (volcanic blocks, bombs and lapilli) are
thrown on parabolic trajectories from a volcanic vent in an eruption. Generally ballistic
fallout is confined to less than three kilometres radius from the vent, as the projectiles
are too big to be ejected any further (Houghton et al., 1988).
Ballistic projectiles are a significant proximal hazard. Damage to structures can be
great (Johnston, 1997a) and loss of life severe (Baxter, 1990) due to the size of the
blocks and bombs (> 64 mm) that are ejected. Ballistic fallout can be hot, causing
burns to humans if they are situated in the path of the fallout. The heat of the projectiles
may also start fires amongst vegetation or structures (Blong, 1984; Houghton et al.,
1988).
3.3.1 Mitigation Measures for Ballistic Fallout
When ballistic material is falling in a volcanic eruption, the best mitigation measure is to
relocate people or restrict them from entering the affected area (Blong, 1984).
Where it is not possible to leave the area then staying under cover in a sturdy building
is recommended. If it is necessary to go outside, then padding to protect the body
should be worn with special attention paid to covering the head. If outside, it is a good
idea to stay alert and watch for any incoming ballistic fallout so as to avoid being hit
(Blong, 1984).
3.4 Lahars
A lahar is defined by Houghton et al (1988) as “a rapidly flowing mixture of water and
volcanic rock fragments of all sizes, particularly with fine ash which may combine with
the water to form a slurry capable of transporting larger rock fragments”.
Lahars can be produced in many ways:- Snow or ice may be melted by erupted ash or lava.
- An eruption through a crater lake or emptying of the crater lake to cause water and
mud to flow down the side of a volcano.
- Heavy rain falling on to unconsolidated ash.
- Movement of a pyroclastic flow or debris avalanche into a river or lake (Houghton
et al., 1988; Gregory and Neall; 1996).
Lahars follow valleys, travel great distances and travel at high speeds (Blong, 1984;
Houghton et al., 1988). Lahars may continue to occur for months to years after a
volcanic eruption with the subsequent mobilisation of secondary lahars (Blong, 1984;
Rodolfo et al., 1996).
Lahars are capable of destroying everything in their path including buildings, bridges,
other structures and vegetation. People and animals are at risk from crush injuries,
drowning or asphyxiation (Baxter, 1990; Johnston and Houghton, 1995).
3.4.1 Mitigation Measures for Lahars
Because of their speed there is a potential for great loss of life from a lahar. However,
detection systems for lahars can be put in place to provide early warning of an
approaching lahar. Sensors can also be used to detect a sudden drop in the level of a
crater lake (Pierson, 1989).
Currently there are already a number of lahar early warning gauges in places on
mountains and rivers in New Zealand. Cronin et al. (1997a, 1997b) suggests that there
should be more of these gauges on New Zealand rivers. A new “Eruption Detection
System” has been installed at Ruapehu in light of the failure of the Lahar Warning
System (LWS) during the 1995 lahars (Bryan, 1997).
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Another mitigation measure for lahars is hazard mapping. Because most lahars flow
down valleys, areas likely to be at risk can be predicted fairly readily and mapped
(Blong, 1984).
If one is caught in or near the path of an approaching lahar, then moving to higher
ground away from any valley should afford protection from the lahar (Blong, 1984). If it
is not possible to move to higher ground in time then it may be possible to avoid the
lahar by climbing on to the roof of a building. If the lahar is not travelling at too great a
velocity then the building may remain intact while the lahar passes around it (Johnston,
1997a).
In the 1995-1996 Ruapehu eruptions, the Rangipo Dam and Power Station was
affected by lahars travelling down the Tongariro River. Lahars have continued to affect
the power station as volcanic deposits in the catchment of Rangipo continue to be
remobilised (Malcolm et al., 1997).
Volcanic material suspended in the lahars caused excessive wear on the turbines of
Rangipo power station and the replacement of parts was necessary. To mitigate
against the effect of the abrasive ash, improvements were made to the replacement
parts so that it would take three times longer for them to be damaged by volcanic ash
(Malcolm et al., 1997).
Other mitigation options considered by Rangipo power station to avoid damage to
turbines included:- Shutting down power generation when the amount of suspended volcanic ash in
Tongariro River causes an excessive wear rate in the turbine.
- Retaining the ash near source using sediment traps or retention dams.
- Diversion of the water sources carrying suspended volcanic material.
- Separation of the ash at Rangipo Dam.
- A sediment trap in the Waihaha pipe bridge (Malcolm et al., 1997).
The eruptions of Mount Ruapehu in 1995-1996 resulted in a deposit of ash blocking the
outlet of Ruapehu Crater Lake. When the lake refills, it is anticipated that this tephra
dam may collapse and produce a dangerous lahar down the Whangaehu River. A
study by the Department of Conservation (1998) has been carried out to look at
mitigation options for this hazard. Some of the more feasible options for mitigation
include:Option 1:
The development of a warning/response system and revised hazard
planning in lahar run-out zones. For example, an acoustic based realtime warning system should be designed and installed.
Option 2:
Engineering works in lahar run-out zones. Construction of dams and
bunds at strategic locations along the Whangaehu River seems the
most practical method of achieving this.
Option 4:
Excavation of a trench through, or partly down into the 1995-96 tephra
deposits at the former outlet of Crater Lake. Engineering works using
machinery (for example, a bulldozer) would be most effective, although
manual digging of a shallow trench is also possible.
Much consultation is still required before a decision can be made on which mitigation
measures will provide adequate protection and account for cultural, philosophical and
other values (Department of Conservation, 1998).
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3.5 Pyroclastic Flows
Pyroclastic flows occur from the collapse of an eruption column or the generation of
laterally directed blasts. The pyroclastic flow, which is made up of gas and volcanic
particles, sweeps away from the volcanic vent at a very rapid speed (up to 100 to
200km/hr) (Nairn, 1991; Froggatt, 1997). Small pyroclastic flows are strongly
controlled by the topography, and will affect an area close to the source of the flow.
Large pyroclastic flows travel radially outwards, traversing valleys and climbing
obstacles (Blong, 1984). Pyroclastic flows are hot and move at such high velocities
that they envelop and destroy everything in their paths. The resulting ignimbrite
deposit varies in thickness laterally and even where little evidence of the flow is left,
human casualties and destruction are likely (Blong, 1984).
The heat of a pyroclastic flow may cause the ignition of fires in vegetation and
structures (Blong, 1984). Pyroclastic flows may also trigger major secondary hazards
such as lahars and flooding (Houghton et al, 1988).
3.5.1 Mitigation Measures for Pyroclastic Flows
As pyroclastic flows are so destructive, the best protection for human lives is to
evacuate hazardous areas prior to any event (Johnston, 1997a). If a small, valley
hugging, pyroclastic flow were likely to occur, then some protection may be afforded by
moving to a higher elevation. However, if there was the possibility of a large
pyroclastic flow occurring, then the only mitigation option would be to distance the
population from the hazardous area, as the flow would be capable of travelling over
topographic highs (Blong, 1984).
Most deaths that occur from pyroclastic flows can be attributed to asphyxia, burns to
the body and blows from hurling rocks. At the edges of the pyroclastic flow, some
measures may prove useful in mitigating against the heat produced by the flow. Face
masks may slow down the onset of asphyxiation by a few minutes. Structures such as
large diameter concrete pipes walled in at the end may offer some protection from low
volume pyroclastic flows. Also, protective clothing may decrease the likelihood of
burns and scalds (Blong, 1984).
3.6 Pyroclastic Surges
Like pyroclastic flows, pyroclastic surges are very fast moving and contain a mixture of
gas and particles. However, unlike pyroclastic flows, surges contain more gas and less
particles, travel at high velocities and are more turbulent (Houghton et al., 1988;
Houghton et al., 1994). While pyroclastic surges travel faster than pyroclastic flows,
they cover less distance making them a more proximal hazard. Pyroclastic surges do
not follow valleys, but deposit thin layers of volcanic material in both depressions and
on topographic highs (Houghton et al., 1994). Because of this ability to surmount the
topography, pyroclastic surges constitute a high volcanic risk (Johnston, 1997a).
Pyroclastic surges can be made up of either hot and dry volcanic particles or they can
be made up of wet volcanic particles. The hot and dry surges are very destructive and
are deadly close to source. Humans and animals are killed by the heat of the surge
and by asphyxiation. Wet (phreatomagmatic or phreatic) surges may also be very
destructive, although they tend to decelerate more quickly than dry surges (Houghton
et al., 1988).
3.6.1 Mitigation Measures for Pyroclastic Surges
The best mitigation measure for pyroclastic surges is prior evacuation of the area at
risk, as surges can surmount topography.
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3.7 Directed Volcanic Blasts
Where an explosive blast is directed across the land surface rather than vertically
upwards, a gas and particle cloud of high velocity and high temperature is produced. A
blast will override ridges and hills near the source, but will begin to become more
influenced by topography as it slows down and moves away (Houghton et al., 1988).
Commonly, large blasts are associated with composite volcanoes of andesite or dacite
composition. They can also occur from lava domes, but this is less common. Basaltic
phreatomagmatic eruptions may produce smaller destructive blasts (Houghton et al.,
1988).
3.7.1 Mitigation Measures for Volcanic Blasts
As there are few immediate precursors to an event of this type, it is necessary to be
located outside the zone of the blast in order to survive (Houghton et al., 1988). The
lateral blast from Mount St. Helens in 1980 created total destruction within a 13 km
radius of the crater (Schuster, 1981). There may be a chance of surviving a blast only
if the person is located at the edge of the blast and in an airtight building (Johnston,
1997a).
3.8 Lava Flows
The behaviour of a lava flow is dependent on the viscosity of the magma, output rates,
volume erupted, steepness of the slope, topography, and obstructions in the flow path.
Viscosity is the most important control on lava flow behaviour and depends mostly on
the composition of the lava. Basaltic lavas are the least viscous and thus are likely to
flow for longer distances. At the other end of the scale, rhyolite lavas have a very high
viscosity which means that they are more likely to form short thick flows or domes (Cas
and Wright, 1987).
Lava flows move relatively slowly and cover limited areas, so the risk to life from lava is
not high (Blong, 1984; Johnston and Houghton, 1995). Lava flows may reach speeds
of up to 50km/hr, but in general they flow at speeds of less than 10km/hr (Johnston,
1997a). Lava flows will cover and destroy structures that cannot be moved away from
the path of the flow, and can start destructive urban and forest fires (Thorarinsson,
1979). Avalanches of lava blocks from steep, high, hot flow fronts represent an
additional hazard (Blong, 1984).
The risk from the growth of an actual lava dome is not high, although destructive block
and ash flows can occur if the dome becomes unstable (Houghton et al., 1988).
3.8.1 Mitigation Measures for Lava Flows
Only a low number of deaths have been attributed to lava flows, and many of these
deaths were considered avoidable. Most deaths resulted from people approaching
lava flows too close (for example, burns from the lava after falling through a lava crust)
rather than the danger afforded by the hazard itself (Blong, 1984). To mitigate against
injuries inflicted by curiosity, it is advisable to restrict onlookers from the site of the lava
flow.
Attempts have been made to divert lava flows away from areas with varying success.
The successful diversion of a lava flow away from a harbour was carried out in
Heimaey, Iceland in 1973. This was achieved by chilling the lava with large volumes of
water (Thorarinsson, 1979). Successful cooling has also been carried out in Hawaii. In
1992 at Mt Etna, Italy, several unsuccessful attempts were made to divert a lava flow
before it was finally diverted using channels and explosives (Barberi et al., 1993).
Earth banks can also be used to divert lava flows. (Thorarinsson, 1979). It is possible
to use already standing structures such as houses to divert lava, although the high
temperatures of the flow would increase the danger of ignition of these objects (Blong,
1984).
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3.9 Debris Avalanches
A debris avalanche is the sudden catastrophic collapse from an unstable side of a
volcano. Many volcanic cones are steep sided and unstable due to rapid growth of the
cone (Houghton et al., 1988). Rising magma, earthquakes, weakening due to
hydrothermal alteration and heavy rain can trigger a debris avalanche of this unstable
material (Houghton et al., 1988; Johnston, 1997a). Avalanched material follows valleys
as it moves down the side of the volcano under the force of gravity (Houghton et al.,
1988). Debris avalanches can be wet, dry or both, and if wet, an avalanche may
evolve and continue to flow further down slope as a lahar (Johnston, 1997a).
3.9.1 Mitigation Measures for Debris Avalanches
As debris avalanches are very destructive, travel a considerable distance at great
speed, and occur with little or no warning, evacuation of areas that could potentially be
affected by debris avalanches is the best mitigation measure (Johnston and Houghton,
1995; Johnston, 1997a).
3.10 Volcanic Gases
The main gases present during an eruption include water vapour, and carbon dioxide
with smaller amounts of other gases such as sulphur gases (SO2 and H2S), and
chlorine and fluorine (Houghton et al., 1994).
During an eruption volcanic gases spread in three main ways from the volcanic vent:- as acid aerosols;
- as compounds absorbed on tephra particles; and
- as salt particles (Thorarinsson, 1979).
Close to the volcano (within a few kilometres) volcanic gases can be sufficiently
concentrated so that they are harmful, but further away the concentrations of gases
dilute, posing little risk to communities (Johnston, 1997a). Direct contact with volcanic
gases can cause eye and breathing irritations, and where heavier-than-air gases (for
example, carbon dioxide) collect in depressions around the volcano, suffocation can
occur (Thorarinsson, 1979; Houghton et al., 1988; Johnston, 1997a).
Some of the gases (for example, sulphur dioxide and hydrogen fluoride) mix with water
droplets in the eruption plume and atmosphere to form acid rain (Figure 5) (Froggatt,
1997). As the dispersion of volcanic gas decreases with distance from the vent, then
the acid rain hazard also decreases downwind (Blong, 1984). When acid rain falls, it
causes damage to metal surfaces, skin, clothing and vegetation, and contaminates
water supplies (Houghton et al., 1988; Froggatt, 1997).
The release of gas with only a minor amount of ash during an eruption can produce
‘vog’ or ‘volcanic smog’. Vog was seen in late October 1995 and late July 1996 during
the Ruapehu eruptions. Vog results from chemical reactions between SO2 and oxygen,
water and sunlight. These create tiny droplets of acidic water and tiny particles of
sulphate minerals which interfere with light rays from the sun, producing haze and
smog (Houghton et al., 1996).
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Halide salts absorbed
into H2SO4 + HCl
aerosol droplets and
adhere to ash particles
Aerosol droplets
adhere to ash
particle surfaces
SO2 converted
to H2SO4
SO2
H2O
Ash
CO2
HCl
.
.
HF
.
.
Acid
Rain
.
Ash, aerosol droplets and
gas erupted from the vent
.
.
.
. .
.
.
.
.
.
.
Leachates flushed
from ash deposits
.
.
.
. .
.
Ash falls to ground
.
.
.
.
.
. .
.
.
.
.
.
.
Rain
.
. .
.
.
.
Mixing with
surface waters
Figure 5: The interaction of volcanic gases during an eruption (after
Johnston, 1997a).
3.10.1 Mitigation Measures for Volcanic Gases
Face masks need to be designed for toxic gases as well as respirable volcanic dusts,
so that people can be protected from the volcanic gas hazard (Blong, 1984).
It may be necessary to evacuate populations where there is the potential for
suffocation, or toxic levels of gases are present. Evacuations were carried out during
the 1973 Eldfield eruption in Iceland, when carbon dioxide levels exceeded acceptable
limits at night time (Thorarinsson, 1979).
3.11 Tsunamis and Seiches
Tsunamis are seismic sea waves of long period caused by disturbances on the sea
floor (Allaby and Allaby, 1990). Tsunamis can be produced by a submarine
earthquakes, by debris avalanches and by underwater volcanic eruptions
(Thorarinsson, 1979). A number of waves may be produced and they may travel long
distances to far-off shores (Blong, 1996). The height of a tsunami varies and may be
affected by the bathymetry, resonance effects and other factors (Harbitz, 1991;
Kowalik and Murty, 1992; Pelinovsky and Mazova, 1992; in Siebert, 1996). In
exceptional circumstances, waves may be produced up to 30 metres high (Blong,
1996).
Tsunamis have produced the second highest toll of deaths during eruptions (Gregory
and Neall, 1996; Blong, 1996). While the initial tsunami causes many of the deaths,
there are also deaths from the health hazards that result following flooding by the wave
(Gregory and Neall, 1996).
Large earthquakes before or during a volcanic eruption from a vent in a lake, may
generate seiches on the lake (Froggatt, 1997). The mass entry of volcanic debris into
a lake from an eruption itself may also create seiches (Froggatt, 1997; Environment
BOP, in prep.). Low-lying land on the edge of a lake would be flooded by a seiche.
Seiches may also travel down rivers that flow from the lake (Froggatt, 1997).
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3.11.1 Mitigation Measures for Tsunamis and Seiches
Tsunamis and seiches affect structures and life situated along coastlines or lake edges.
In the event of an approaching wave, evacuation from those areas is essential
(Froggatt, 1997).
Hazard maps can be used to identify areas of potential risk from tsunami. Modelling of
tsunami paths using detailed bathymetry can be used to construct hazard maps
showing predicted tsunami arrival times (Aida, 1975; Kienle et al., 1987; in Siebert,
1996).
3.12 Flooding
Following a volcanic eruption, the deposition of volcanic sediment in valleys may
disrupt normal stream or river flows. Channel aggradation, and the increased lateral
migration of channels and bank erosion may occur. These conditions can cause
damage to structures and worsen normal seasonal flooding (Pierson, 1989).
Volcanic material will cause stream blockages and pond temporary lakes (Blong,
1996). After the 26,500 yr B.P. Oruanui eruption, and again after the 181 A.D. Taupo
eruption, temporary lakes were created when volcanic material blocked the normal flow
of the Waikato River. The largest of these lakes was situated in the Reporoa Basin
(Tilly, 1987; Manville, in press; Manville, in prep; Manville et al., in prep.).
Erupted volcanic material will sometimes also block an outlet to an existing lake or river
causing a body of water to build up behind the “dam”. When this “dam” collapses due
to erosion or is overtopped, large scale catastrophic flooding can occur. Following the
Tarawera eruption, a tephra bank was created at the outlet to the Tarawera River, and
the lake rose 12 m behind the bank. Following heavy rainfall, the tephra bank was
“washed away” and a breakout flood occurred down the river. The flood was
accompanied by the silting up of the Tarawera River in the following years, as the flood
waters eroded the countryside that they flowed over (Nairn, 1991; White et al., 1997).
A similar situation occurred after the 181 A.D. Taupo eruption when Lake Taupo’s
outlet became choked with volcanic material from the eruption. The result of the
blockage was that the level of Lake Taupo rose to a mean height of 34 m above its
normal level. As the lake overtopped the ignimbrite barrier blocking the lake outlet, it
began to erode the barrier away. Catastrophic collapse occurred, creating a breakout
flood down the Waikato River (Tilly, 1987; Manville, in prep.; Manville et al., in prep.).
3.13 Hydrothermal Eruptions
Tectonic or volcanic movement can trigger a decrease in fluid pressure, thus inducing
instability and boiling in the shallow portions of hydrothermal systems, and causing
explosions to occur. However, there are some hydrothermal eruptions in New Zealand
that have not been linked to volcanic or tectonic events. For example, it is thought that
underground steam generation at Wairakei and Tauhara geothermal fields have
caused eruptions there (Nairn et al., 1997).
Hydrothermal eruptions are generally limited in extent (a few hundred metres from the
vent), cause damage only to the immediate area around the eruption, and do not
produce significant ash clouds (Nairn, 1991; Nairn et al., 1997).
3.13.1 Mitigation Measures for Hydrothermal Eruptions
Recognition of the conditions and processes that lead to hydrothermal eruptions can
help in the mitigation of hydrothermal eruption hazards. Vigorously steaming ground
and a shallow aquifer at boiling temperatures may indicate the potential for a
hydrothermal eruption.
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For effective mitigation, Bromley and Mongillo (1994) consider it necessary to
investigate areas prone to hydrothermal eruptions, and carry out monitoring of those
areas. They also suggest that the consequences of any human impacts on these
areas, such as excavation, sealing, flooding, draining or drilling, must be carefully
considered before the activity is undertaken.
3.14 Volcanic Earthquakes
Volcanic earthquakes are earthquakes that are related to the rise of magma beneath a
volcano. Generally these earthquakes are shallow and of low magnitude, so therefore
only pose a limited risk to life (Thorarinsson, 1979). It is possible, however, that
volcanic shocks can cause some damage to structures close to source (Thorarinsson,
1979; Blong, 1984).
3.14.1 Mitigation Measures for Volcanic Earthquakes
Volcanic earthquakes are a precursor to volcanic activity, and therefore provide a
useful warning of the approaching volcanic eruption, and a chance to put avoidance
plans into effect (Blong, 1984).
For information on mitigative action against volcanic earthquakes, it is necessary to
refer to mitigation measures developed for earthquakes in general (Malcolm and
Parkin, 1997).
3.15 Electrical Discharges
Lightning displays occur during volcanic eruptions where an abundance of fine debris is
produced together with strong gaseous expansion. The lightning discharges result
from friction between tephra particles, steam and other gases (Blong, 1984).
Lightning creates a hazard to communication systems where discharges take place
from cloud to cloud or from eruption column to eruption centre (Blong, 1984; Froggatt,
1997). Commonly, lightning also discharges to the earth around the volcano, and this
poses a hazard to life and property (Thorarinsson, 1979; Blong, 1984).
3.15.1 Mitigation Measures for Electrical Discharges
To avoid being hit by lightning stay indoors during the discharges in a sturdy, earthed
building. If outside, shelter in a depression away from isolated trees, metallic objects
and water (Blong, 1984).
3.16 Other Hazards
Sounds produced by volcanic explosions constitute a minor hazard to humans and
animals. Victims in the past have complained of earache or deafness after an
explosion has been heard. Atmospheric shock waves are of more significance as they
may cause physical damage to buildings (Blong, 1984).
Following volcanic activity, starvation and disease have both caused human and
animal fatalities. Supplies of fresh cereals, vegetables and pasture may be destroyed
or cut off by a volcanic eruption, resulting in famine. Famine may also occur when a
decrease in temperature due to ash in the atmosphere causes crops to fail (Blong,
1984; Gregory and Neall, 1996).
There are still many aspects of eruption dynamics that are, as yet, unstudied.
Therefore, there is still only a limited understanding about some of the hazards that
may occur during an eruption. For example, Talbot et al., (1994) studied dilute gravity
currents and rain flushed deposits in the 1.8 ka Hatepe Plinian deposit from Taupo
volcano. They believe that hazards from dilute gravity currents are considerable but
often overlooked, and suggest that the recognition of further gravity current deposits
will contribute to more thorough volcanic hazard assessments.
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Page 27
Wilson and Hildreth (1998) studied hybrid fall deposits in the Bishop Tuff, California.
These deposits display features common to both classic fall and surge deposits.
Wilson and Hildreth (1998) suggest that these deposits formed when tephra fall
material that had been already deposited, was re-entrained by strong winds generated
during a pyroclastic flow, and then redeposited. They state that the “ recognition of fall
deposits is important in interpreting the dynamics of explosive eruptions and correctly
assessing volcanic hazards”.
The continued study of deposits and processes that are not extensively understood will
aid in hazard assessment, and mitigation of those hazards can then be undertaken.
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Appendix I: Scientific Alert Levels (Johnston, 1997a)
Frequently active cone volcanoes
White Island, Tongariro-Ngauruhoe, Ruapehu
Reawakening volcanoes
Scientific Alert
Volcano Status
Indicative Phenomena
Level
Usual dormant or
quiescent state.
Typical background surface
activity; seismicity,
deformation and heat flow at
low levels.
0
Signs of volcano unrest.
Departure from typical
background surface activity.
1
Minor eruptive activity.
Onset of eruptive activity,
accompanied by changes to
monitored indicators.
Increased vigour of ongoing
activity and monitored
indicators. Significant effects
on volcano, possible effects
beyond.
Significant change to ongoing
activity and monitoring
indicators. Effects beyond
volcano.
Destruction with major
damage beyond volcano.
Significant risk over wider
areas.
Significant local eruption
in progress.
Hazardous local eruption
in progress.
Large hazardous
eruption in progress.
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2
3
4
5
Kermadecs, Northland, Auckland, Mayor Island, Rotorua,
Okataina, Taupo, Taranaki
Indicative Phenomena
Volcano Status
Typical background surface
Usual, dormant or quiescent
activity; deformation,
state.
seismicity, and heat flow at low
levels.
Apparent seismic, geodetic,
thermal or other unrest
indicators.
Increase in number or intensity
of unrest indicators (seismicity,
deformation, heat flow etc).
Minor steam eruptions. High
increasing trends of unrest
indicators, significant effects
on volcano, possible beyond.
Initial signs of possible volcano
unrest. No eruption threat.
Eruption of new magma.
Sustained high levels of unrest
indicators, significant effects
beyond volcano.
Destruction with major
damage beyond active
volcano. Significant risk over
wider areas.
Hazardous local eruption in
progress. Large scale
eruption now possible.
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Confirmation of volcano
unrest. Eruption threat.
Minor eruptions commenced.
Real possibility of hazardous
eruptions.
Large hazardous volcanic
eruption in progress.
Appendix II: Detailed Mitigation
Measures
Volcanic Dust Mitigation Techniques (From Labadie, 1983)
Techniques for reducing the effects of volcanic dust can be grouped into three broad
categories - keeping the dust out, controlling what gets in and disposing of the dust.
Reduce Exposure
•
•
Avoid exposure - evacuate, re-route.
Reduce operations - Shut down unused equipment, aircraft/vehicles in hanger.
Reduce Severity
•
•
•
•
•
•
Filtration - install, increase.
Sealing - windows, doors, ports, hatches, ducts.
Multi-level protection - “room within a room”.
Positive pressure - buildings and vehicles.
Access control - “clean room” procedures.
Humidification.
Decontaminate
•
•
•
•
Wash.
Brush/wipe.
High pressure air.
Vacuum.
Reduce Effects
•
•
•
•
•
Accelerate maintenance/cleaning.
Change operational procedure.
Replace contaminated parts.
Re-design equipment - add filters, change air flow pattern.
Reduce performance requirements.
Dispose and Control
•
•
•
•
•
•
Wet down/flush surface.
Load when wet.
Vacuum residue.
Apply binder on roads.
Plow under.
Stabilise dust.
Sewage Treatment Plants and Ash (from FEMA, 1984)
Equipment such as mechanically cleaned screens, mechanical grit removal
mechanisms, and comminutors are likely to be damaged from ash as will any
equipment with mechanical moving parts that come into contact with the substance.
Recommendations
• Temporarily cover all mechanical equipment that might be exposed to ash fall.
• Where possible, place sandbags or other devices at the entrance channel to the
plant to trap ash. (This procedure requires frequent attention due to normal
settleable solids present in sanitary waste).
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• Consider removing or bypassing the comminutor during the initial heavy flows of ash
into the plant.
• Frequently check the primary clarifier to prevent (a) damage to the sludge collection
mechanism and/or the digester sludge pumps and (b) the transference of ash to the
digester. Depending on the type of mixing employed in the digester, further damage
may occur in the sludge transfer pumps.
• To clear ash from individual sections of then treatment facility, bypass individual
units, or in extreme instances, make a complete plat bypass to a holding pond or
lagoon.
• The effects of ash on the pH value of influent or effluent are not clearly understood.
Toxicity may occur in the plant effluent to the extent that the bacterial growth is
damaged or lost. At the first signs of distress on a biofilter, check and adjust the pH
level of the influent to the biofilter.
Drainage and Irrigation Systems (from FEMA, 1984)
Ash carried into a canal by rain or drainage water running off the ground above the
irrigation system can plug canal pipelines, abrade and short out pump stations,
electrical equipment, and hydroelectric generators. A disrupted irrigation system,
particularly during the irrigation season can result in economic losses.
Recommendations
• Repair or replace damaged culverts and flumes.
• Before/ during ash falls seal all buildings and shut down electrical equipment. Cover
pump/generation facilities.
• After ash falls, conduct field surveys of the main canal and headworks. If necessary
close the canal and correct deficiencies.
• Inspect intersecting natural channels, gullies and canyons for debris jam conditions.
• Check conditions of watershed above canal for ash accumulations to prevent future
clogging.
Outdoor Public Areas (from FEMA, 1984)
Cleaning these areas is not practical - the dust will lessen with the passage of time.
Recommendations
• Water/sprinkle lawns to consolidate ash in the turf. (moistened ash is easier on
cutting mechanisms).
• Do not wash shrubs and trees in large park areas - ash accumulation will abate with
the action of wind, rain, and snow.
• Clear golf course greens by sweeping, followed by vacuuming.
• Sweep/hose grave markers, picnic tables, seats, playground equipment, etc.
• Clear grassed athletic field using the recommendations for other grassed areas.
Sweep/vacuum athletic fields with artificial surfaces.
• Clear ash from pools using normal pool maintenance clearing procedures.
• Do not attempt to clear ash from picnic/camp sites with natural ground cover. To
temporarily improve the situation cover ground with wood chips.
• Do not clear ash from parking lots that have gravel surfaces - the removal process
will result in gravel loss. Place a thin lift of gravel on surfaces that have moderate to
light ash.
Roads and Streets (from FEMA, 1984)
• Vehicles moving over even a thin coating of ash can raise ash clouds creating
visibility problems. To combat this speed restrictions or road closure may be
necessary.
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• Extremely wet ash creates very slippery and hazardous road conditions.
• Ash filling roadside ditches and culverts can prevent proper drainage and cause
shoulder erosion and road damage.
Don’ts
• Conventional snow removal methods do not work on dry ash - they only stir it up
and cause it to resettle on the roadway. When ash is pushed to the side of the
paved travelled lanes, wind and vehicle movement cause it to billow.
• After the Mount St. Helens eruption various types of dust palliatives on thin layers of
ash were used with some success. However these palliatives did not satisfactorily
control heavy deposits for any appreciable length of time and proved to be an
expensive method of control. The palliatives included some commercial retardants
and lignin solutions from the paper pulping process.
Recommendations for Paved Roads and Urban Streets (from FEMA, 1984)
• Notify bordering property owners to move ash from roofs.
• For a thorough cleaning of paved roads with storm sewers, use power brooms on
the dampened residue.
• To remove remaining ash on paved roads without storm sewers, flush road with
water.
• As soon after the street cleanup as possible, remove ash deposits from catch basin
inlets with vacuum trucks or machines with jet rodding and vacuum systems. If the
cleanup is delayed ash will crust making it harder to remove. Further, the ash
density impairs the self-cleaning function of the sewers grade, creating the potential
for plugging the sewer.
Recommendations for Paved or Oiled Roads that have No Curbs or
Sewers (from FEMA, 1984)
• Sprinkle ash with water, blade it onto the shoulders or into the ditches. Remove
residue by sweeping or flushing it, if necessary. Where there are gravel shoulders,
replace the lost gravel.
Recommendations for Ash on Gravel Roads (from FEMA, 1984)
• Blade the ash into roadside ditches being careful to avoid unnecessary loss of
surface materials.
• If the existing right-of-way is wide enough spread the ash along the back slopes
outside the ditch. Much of the ash may become integrated into roadside vegetation,
however the ash in these areas will blow for some time afterwards.
• Remove ash blocking the drainage in ditches and culverts, and transport it to a
disposal site. A considerable amount of ash will remain on the road surfacing
creating traffic visibility problems. It cannot be eliminated totally and will decrease
with time.
• On the road bed, place a thin lift of rock consisting of graded material 5/8 inch to 0 in
size and crushed to a standard specification. This layer can be added and
processed into the existing surface to achieve the bonding effect that will stabilise
the surface under traffic. (It will not provide total dust control, but will achieve
visibility levels so that traffic operations can be resumed.
In determining the thickness of a gravel blanket the following factors should be
considered:
• prevailing depth of ash deposit.
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• functional classification of the road-its importance as a service arterial; acceptable
speed restrictions.
• traffic characteristics-average daily traffic; variation in volumes, operation of
intersections; turning conflicts.
• condition of existing surface - undulations, washboards and ruts affecting loss of
material if ash is bladed to shoulders.
• existing surface material - depth, quality and gradation as determinants for
integrating the ash by scarification, mixing, blading and processing existing material.
• Consult with other disaster coordinators about the best methods of handling the
problems of traffic movement, ash removal and final cleanup.
Motor Vehicles and Engines (from FEMA, 1984)
Ash damages filter systems and engines.
Preventing unnecessary damage to vehicles is essential to protect their ability to assist
in emergency operations and clean-up procedures.
Recommendations
• Prepare contingency plans to provide public service with heavy duty air filtration
units for emergency use where dust is a hazard.
• Before choosing an air filter unit consult manufacturers’ recommendations.
• After installation, inspect the air filter frequently. In heavy ash falls (visibility less
than 50 ft) check the filter every 100 miles. Where ash fall is lighter, check the filter
less frequently but at least every 1,000 miles. Check for holes, cracks or damage to
the seal. Clean using compressed air, not to exceed 30psi. Set filter housing
covers very tightly. Do not wrap filter with cheese cloth or silk stocking.
• Change oil and oil filter often. Lubricate all chassis components at each oil change.
• Cover passenger compartment air intake vent with loosely woven felt-type material
or keep air conditioning/air blowers closed. Disconnect automatic blowers.
• Use air pressure (30 psi or less) to blow dust from open electrical equipment
(alternator, starter, wiper motor) every 1,000 miles or less.
• Clean brake assemblies every 100 miles or less with compressed air.
• Clean car, including engine, radiator, etc daily, if necessary using water to flush the
ash.
• Rebuild engines at shops outside the ash fall zone.
Recommendations for Rail Systems (from Labadie, 1983)
•
•
•
•
•
•
•
Accelerate filter change.
Wash locomotives inside and out.
Seal cab and compartments with duct tape, etc.
Pressurise compartments with compressed air line from engine.
Accelerate cleaning, maintenance of signals, gears, etc.; wash with high pressure
water, re-lube.
- Wet dust can cause leakage/grounding in signal system.
- Increase line voltages.
- Accelerate cleaning and maintenance.
Develop alternate signal procedure.
Microwave co-axial cable is pressurised; will keep dust out.
Roof Tops (from FEMA, 1984)
Removing ash from roofs is a top priority.
1. A prerequisite to reactivating ventilation and air-handling systems.
2. Clean the roofs and then ground level to prevent ash falling on to the clean streets.
3. Enhances morale when people can observe the rapid clean-up.
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4.
Rapid removal may prevent roof collapse.
Recommendations
• Notify building owners to remove ash to prevent streets from having to be recleaned.
• Inform public of effective methods to (1) remove ash from roofs and preparing it for
pickup, and (2) organise neighbourhood volunteer cleanup activities.
• Caution residents against flushing into sewers.
• Remove ash dry before the first rain. Dampen with light spray of water to reduce
billowing.
• Ash cleanup supervised by knowledgeable building maintenance personnel to
prevent roof damage.
• Use protective measures when removing ash from roofs (e.g. Fire hoses may
damage roof).
• Do not flush ash into drains and downspouts - it can clog the pipes. Ash flushed into
dry wells can seal then, rendering them inoperative.
• Remove all ash near intakes of ventilation systems.
• To protect sewer lines disconnect down drains at ground level until cleanup is
complete.
• Clean roof surfaces accordingly to reduce the accelerated deterioration of roof
coatings caused by the mildly acidic ash. Most susceptible are older galvanised
roofs which are pitted and low gage galvanised roofs.
• On flat roofs, hand sweep ash into windrows and transport by wheelbarrow to an
edge dump. Use proper protection to prevent impact and abrasion damage.
Hoppers with a funnel pipe suspended above a loading truck can be used to collect
the ash.. To remove final dry residue/thin layers of ash, use air pressure carefully.
Small vacuum equipment is not practical due to ash abrasiveness.
• On steep shingle roofs place dams in the troughs to prevent the ash from reaching
the down-drains. Then hose down the ash and clear it from the eave troughs. Take
care to avoid deforming the gutters.
• On low slope bitumastic mopped roofs with a thin ash layer, flush the ash with water.
• To avoid clogging the inlets to roof drains, encircle the roof inlet with a specially
fabricated ring made from heavy sheet metal about four inches wide and 2 feet in
diameter. This serves as a dam allowing water to spill over the top, while the ash
settles in the surrounding roof depression. Later, when dry, the ash can be removed
manually.
Public Buildings – Recommendations for Clean-Up (from FEMA, 1984)
• See section on roofs.
• Sills, ledges, parapets, and wall surfaces do not warrant extra cleanup efforts if the
primary functioning of the building is not impaired.
• Shut down Air-handling/air conditioning mechanisms prior to or during the onslaught
of the ash fall. Check windows are closed, air conditioners are off, and that all
unnecessary outside openings are closed and sealed.
• To restart air handling systems:
1. Clean the roof mounted intakes and roof area adjacent to the intakes
2. Clean or replace filters
3. Inspect, clean or lubricate moving portions of the mechanism following
prescribed routine maintenance.
• In buildings where air quality is critical (eg hospitals) actions must be taken under
the advice of qualified personnel.
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Recommendations for Electrical Distribution and Switching Facilities
(from FEMA, 1984)
• Immediately after ash fall dust, sweep and blow ash from the electrical equipment at
substations.
• Shut down electrical systems before any attempt is made to clean or service them.
Throw the main circuit breakers, not just the nearest switches.
• Remove dry dust immediately from the most sensitive systems by blowing it off
using air pressure 30 psi or less. Avoid rubbing or brushing equipment. Be careful
not to blow the dust into other places that should be kept clean. Vacuum where
possible.
• Clean electrical components such as small motor and light bulbs as they will
generate excess heat when blanketed with dust which may cause fires. Vacuum or
blow off dust.
• Avoid saturating electrical components when hosing dust off.
• Check for trees heavily loaded with ash near power lines - limbs may fall on power
lines.
• Check and keep insulators clean. A moderate wind on dry ash will clean most
insulators on outdoor distribution lines and equipment. Light rain which does not
wash the ash away is harmful and can cause flashovers and short circuits. Ash that
has hardened may require special cleaning methods such as hand cleaning or water
jetting.
• Protect back-up and auxiliary units to avoid starting problems when they are
activated.
• Maintain protection and cleaning programs continuously until the threat of
windblown ash is over.
Recommendations for Electric Motors (from FEMA, 1984)
• Turn off electric motors and machinery (motor switch and main circuit breakers)
before cleaning them.
• Clean electrical equipment using 30 psi or less. Vacuum where possible and
change filter bags often. Avoid damaging surfaces by rubbing or brushing them. Do
not blow dust into places that should be kept clean. Follow manufacturers
recommendations for cleaning equipment under dusty conditions.
Increase
maintenance servicing.
• Watch for electric shocks when operating dusty equipment. Be aware that
overheating and fires may be possible.
Recommendations for Electronic Equipment (from FEMA, 1984)
• Discontinue operation of the equipment during the ash fall and cleanup period.
• Place protective covers on electronic equipment. Follow manufacturer’s instructions
on dust protection and maintenance.
• Close areas occupied by the equipment.
Shut and seal off air-handling
components. Stop entry of outside air.
• Immediately attend to expensive electronic equipment such as computers.
• Restrict access to computer facilities and electronic equipment. Only essential
personnel allowed, and vacuum their clothing before entry.
Computer Services - Mitigation techniques (from Labadie, 1983)
•
•
•
Most advised tactic - shutdown all computer and electronic systems until the dust
had been completely removed from the area and equipment.
Continual cleaning and aggressive protection of computer systems should allow
continued operation in all but the heaviest fallout.
Prevention - Clean and condition surrounding air to keep out dust.
Doc # 498257
Page 43
•
•
•
•
•
•
•
•
•
•
•
•
•
Cotton mat filters (used in clean rooms) were found best for filtering particles, but
they reduce air flow. Solution is to use larger fans to maintain required air flow.
Use fluted filters as a compromise; increases surface area but reduces air flow by
only about 20%.
Digital integrated units can vary 5-10% in performance (depending on type of
circuit) and still be acceptable. It is difficult to generalise about other equipment.
Humidifying ambient air (e.g. wet carpets) will help to control dust re-entrainment.
Dust on equipment can be blown out with compressed air. If the air is too dry,
static discharge could damage sensitive components. If the air is too damp, the
dust will stick. Relative humidity of 25-30% is best for compressed air.
Cleaning with a pressurised water-detergent mix and a hot water rinse is quite
effective. However, this process requires at least partial disassembly.
Dust on digital circuits wont cause much of a problem because of the low voltages
involved. High voltage or high-impedance circuits are very vulnerable to leakage
caused by semi-conductive dust. Dust that is acidic is conductive as well as
corrosive.
Dust should be blown or brushed away from power supplies and CRTs (especially
high voltage leads, capacitors).
Dust may have high static charge and be hard to dislodge; requires brushing to
dislodge.
Accelerate filter change; use prefilters.
Change to absolute filters; will keep particles out to 1 micron.
Keep computer power on to operate filtration, but don’t run (especially disk drives).
Maintain “room within a room” configuration; restrict access; re-circulate air;
accelerate cleaning of area.
Communications Systems – Mitigation Techniques (from Labadie, 1983)
•
•
•
•
•
•
•
•
•
Dust adheres to teflon insulators on communication antennas. Replace with
ceramic insulators.
Plastic switches and pushbuttons abrade quickly. Necessary to replace.
Seal up repeater stations and other installations; shut air intakes; internal air
circulation and leakage should be sufficient for cooling.
Blow out or vacuum out radio equipment; brush off.
Seal equipment that is not already watertight. Smaller units have low power
consumption and do not generate much heat.
Magnetic particles that stick to relay cores should be blown off.
Keep moisture out of equipment.
Clean equipment daily; increase use of filter paper.
Clean out microwave dishes, feed horns, wave guides. In stall covers; plastic tarp
will do in an emergency.
Heating/Cooling Systems (from Labadie, 1983)
•
•
•
•
•
•
•
•
•
•
Mitigation tactics focus on stopping the dust before it enters the cooling air stream
and then on to protecting the air handling system itself.
Close external air intakes; use internal circulation only; this will create positive
pressure inside building.
Control access; seal doors.
Establish decontamination rooms for entering personnel; provide vacuum cleaners,
shoe covers, disposable caps.
Stockpile cleaning supplies, duct tape, disposal containers.
Use extra (and heavier) filters for external air intakes.
Clean dust away from external intakes; restrict vehicle and foot traffic near intakes.
Install intake hoods that extend farther above ground.
Install pre-filters.
Add sand filters to cooling towers.
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Doc # 498257
•
•
•
•
•
•
•
•
•
Cover cooling towers.
Clean coils, radiators, etc. with compressed air and/or water.
Add cooling coils to uninterruptable power supply to reduce temperature of
incoming air by 10º (increases cooling capacity).
Add back-flushed filters to cooler sumps.
Install alarm circuit to warn of excessive pressure differential across filters; filters
that get too clogged can break open.
Change from open, drip-proof type motors to totally enclosed, fan-type motors.
Reduce staff to minimum required.
Close and seal unused rooms; turn off unused equipment.
Shut down air handling system to prevent damage to chillers, fans, pumps, etc.
Recommendations for People Exposed to Ash (from FEMA, 1983)
People subject to heavy exposures should observe the following precautions:• Wear light face or surgical masks to prevent inhalation of large particles which may
contribute to throat and eye irritation.
• Advise patients with chronic bronchitis, emphysema, and asthma to stay inside and
avoid unnecessary exposure to ash.
• Handle dust in open well ventilated areas, and wet dust where possible to prevent
movement.
• Wear protective clothing and high efficiency dust masks. These should be available
and easily accessible in preparation for volcano related emergencies.
• In fine dust environments wear goggles or corrective eye-glasses instead of contact
lenses.
• Personnel not essential to the emergency should be kept inside and made to strictly
observe all safety precautions during a cleanup.
• Keep doors closed where there is a heavy dust accumulation.
• Give sight distance the proper attention to avoid vehicle and industrial accidents.
• Training in first aid and emergency procedures is essential to disaster relief work
and self-protection.
Recommendations for Fire Hoses and Equipment (from FEMA, 1984)
• Make certain fire fighters are present to ensure proper protection of hoses and
hydrants.
• Avoid distribution of fire hoses to citizen groups and other non-fire employees unless
they are supervised and instructed in their use and the use of hydrants.
• Use hoses designed only for outdoor use
• Do not drag hoses over pavement any more than is absolutely necessary.
Aircraft Systems and Ash (from Labadie, 1983)
•
•
•
•
•
•
•
Avoid exposure to dust - shut down for the duration of the problem, aircraft in
hangars or evacuated, re-route air traffic.
Seal seams, ports, vents, etc with duct tape to keep out dust. This will take 4 to 5
hours. Very hard to seal up an aircraft completely; too many ports, vents, seams,
joints.
Maintaining positive pressure within aircraft components would help keep dust out,
but very difficult to not cause damage to ground equipment.
Blow or vacuum dust off before washing (otherwise dust tends to flow into ports,
vents, control surfaces).
Flush or wash off residue. Do not scrub or broom.
Wash down gear, underside, air-conditioning intakes, engines.
Check pH of aircraft/engine surfaces for acidity. Extra care is needed if dust is
acidic.
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Page 45
•
•
Neutralise sulphuric acid by adding petroleum based solvent to wash water. Dust
buildup in or around hatch seals could cause problems with pressurisation after
launch.
Fuel tank vents must be open during loading, unloading, and transfer of fuel. If
vents are plugged with dust, or if sealed and seal not removed, tank could collapse.
Airborne Systems Support - Runway Coverage(from Labadie, 1983)
If operations not suspended, runways must be cleaned continually. There is
disagreement on the proper use of water in cleaning runways. Some felt that the water
turns the dust to sludge (or causes it to harden); others found it impossible to control
the dust without wetting it down first.
Basic removal techniques
•
•
•
•
•
Wet dust down into water trucks
Blade into windrows
Pick up with belt loaders or front-end loaders
Haul to dump areas
Sweep and flush residue
Supporting technique
•
•
•
•
•
•
Sweep/vacuum dust first, then flush with water (best for ramps, etc)
Push dust to runway edge; plough under or cover with binder (Coherex or liquid
lignin)
Install sprinkler along edges of runway to control re-entrainment of dust from
aircraft engine blast or wingtip vortices
Keep residue on taxiways and ramps wet.
Sandbag around catch-basins; water level builds up and then runs over bags as
dust precipitates. Catch basin remain clear and dust can be vacuumed or loaded
as above.
Open graded (“popcorn” surface) runways are to some extent self cleaning; engine
blast on take-off will blow dust out of crevices.
Operational Considerations
•
•
Techniques require extensive mobilisation of personnel and equipment on a
continual basis.
Extensive use of removal equipment would draw down POL supplies; equipment
would also require increased maintenance due to dust damage.
Airborne Systems Support - Landing aids and air traffic control (from
Labadie, 1983)
•
•
•
•
Protection requires periodic cleaning, maintenance and monitoring.
Turning off unnecessary equipment will reduce exposure.
Exposed light and indicator systems, radar antennas, and any equipment that
requires cooling air are especially vulnerable to dust contamination
Back-up generators may be required due to disruption to power supplies and these
too may be vulnerable to dust damage.
Mitigation Techniques
•
•
Replace antennas which have Teflon insulators (dust hard to clean off and will
cause shorting; ceramic insulators should be used).
Seal relay boxes, remote indicator units, light systems to prevent dust entry.
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Doc # 498257
•
•
•
•
•
•
•
•
•
Increase cleaning and maintenance of systems that can’t be sealed or that require
cooling air.
Vacuum out or blow out dust; clean relays, etc. with contact cleaner.
Use high pressure water wash on exposed antenna rotor bearings; re-lubricate.
Cover exposed joints, seams, bearings.
Seal building, control access; vacuum shoes, clothes.
Reduce operating levels; shut down unused equipment; reduce broadband displays
to minimum; reduce cooling and power consumption.
Change procedures; combine sectors for reduced coverage.
Transfer responsibility to other control centres if “planned shutdown” required.
Accelerate installation of solid state equipment - power and cooling requirements
lower.
Airborne Systems Support - Aerospace Ground Equipment (from Labadie,
1983)
Mitigation Techniques
•
•
•
•
•
•
Don’t use gas turbines (for engine start and electrical power), air compressors and
air conditioners. This equipment operates on the ingestion of a large volume of air
and has only coarse filtration. Extra filtration cannot be added without affecting
operation. Using air conditioners to pressurise aircraft compartments would only
blow dust into the aircraft and ruin the air-conditioners in the process.
Constant cleaning and maintenance
Don’t wash equipment. Water turns dust to sludge and washes it into the
equipment.
Vacuum dust off equipment.
Change oil and filters more often.
Change design to include better filtration.
Operational Considerations
•
•
•
Dust damage is cumulative, and equipment can withstand a certain level of
contamination. A limited number of launch/recovery cycles could be carried out,
but extended operations would become more difficult.
Supply of oil, filters, spare parts may be limited.
Problem of maintenance and repair in a dust contaminated environment.
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Appendix III: 1995-1996 Ruapehu
Eruptions Survey
Introduction
In 1995 through the months of September and October, a series of ash-producing
eruptions occurred from Mt Ruapehu (Figure 6). Activity recommenced in June and
July of 1996 with a further series of eruptions. Lahars accompanied the eruptions with
36 generated in the Whangaehu Valley alone by 14 August 1996 (Houghton et al.,
1996).
The ash produced by the activity closed airports, caused damage to hydroelectric
power facilities, and closed State Highway 1 (Houghton et al., 1996). There were
animal deaths, mainly from ash ingestion and fluorosis poisoning (Shanks, 1997), and
fish in local rivers were affected by lahars. The ski seasons in 1995 and 1996 were
disrupted by the eruptions causing losses for ski operators. General tourist numbers
were also down. Ash was a nuisance, and had to be cleaned up by both home and
business owners (Keys, 1996b).
The 1995-1996 Ruapehu eruptions had some positive side effects. A new form of
tourism emerged, with the chance to observe an active volcano. The ash also acted as
a fertiliser for pasture because it contained useful amounts of sulphur, minor amounts
of selenium, and in some areas potassium and magnesium (Cronin, 1996; Cronin et
al., 1996b; Cronin et al., 1998). Another positive side effect was that the Ruapehu
eruptions provided some experience in the management of small volcanic eruptions
(Keys, 1996b).
The 1995-1996 Ruapehu eruptions also provided an excellent opportunity to study the
effect of a series of small volcanic eruptions on contemporary New Zealand
communities. From looking at how New Zealanders dealt with the problems associated
with this volcanic eruption, it was possible to determine which mitigation measures
were most effective, and thus which measures can be successfully employed when the
next eruption occurs.
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Doc # 498257
Figure 6: An eruption from Mount Ruapehu on July 8, 1996.
Nature of the Survey
A questionnaire was produced to look at how communities dealt with the Ruapehu
eruptions. The objectives of the survey were:1. To gain a perspective on people’s perception about volcanic hazards;
2. To find out which mitigation measures were employed by people during the 1995
and 1996 Ruapehu eruptions; and
3. To look at the impact of the eruption on communities.
The questionnaire consisted of a set of 27 questions designed to meet the three aims
above. The first section of the survey (questions 1 to 11) included questions that were
designed to find out some general details about the survey participants and to look at
their perception of various volcanic hazards. The next two sections were entitled “The
1995 and 1996 Mt. Ruapehu Eruptions” and “Effects of the Eruptions”. The questions
in these sections were designed to look at the effect that Mount Ruapehu had on
communities, and the actions that people had undertaken to counter the effects of the
eruptions. The “General Lifestyle and Health”, “Benefits Arising from the 1995/96
Ruapehu Eruptions” and “Information and Assistance from other Organisations”
sections were also designed to look at the impact of the eruptions on communities.
The final section in the survey was titled “Change of Circumstances” and looked at
whether different seasons would produce different impacts for various industries. A
section was also included at the end of the survey for respondents to provide
comments on issues regarding the eruption that they thought were important. A copy
of the survey/questionnaire is included in Appendix III.
A press release was issued to encourage those interested in filling out a questionnaire
to make contact. Those people who responded to the press release were sent survey
forms. To gain more participants it was decided to target communities that were likely
to have been affected by the 1995 or 1996 Ruapehu eruptions. The survey was sent
to a number of communities located in the central North Island. The main communities
that were targeted included Whakapapa Village, National Park, Turangi, Tokaanu,
Taupo, Rotorua, the Tauranga and Mt Maunganui area and Hamilton. The survey was
also sent to a variety of other scattered rural and urban locations.
Those who received the survey were given two weeks to reply, and were supplied with
a return envelope to send the questionnaire back in. To gain a reasonable response
rate a second press release was issued after the two weeks had passed, reminding
participants to send in their survey forms. A total of 208 respondents completed the
questionnaire. The response rate for the survey was 42.5%.
Questionnaire Results
General Details
Question 1 - Do you own a business or are you answering this survey on behalf
of a business?
For this study, it was decided to concentrate on sending the questionnaire to people
who owned businesses to determine the effects that the Ruapehu eruptions had on
them. The effects of the eruptions on small businesses in particular had not been
extensively studied after the Ruapehu eruptions. Through the survey it was possible to
determine the amounts of money lost by some businesses, as well as gather
information on the physical effects of the eruptions.
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The results indicate that 96% of respondents answered the questionnaire on behalf of
a business. The other 4% answered the questions in the survey with regard to their
home location.
Question 2 - What category do you class your business in?
The two most common categories that survey respondents classed their business in
were tourism (27%) and the service industry (26%) (Figure 7). There were four other
significant business categories, which included the retail industry (15%), transport
industry (9%), farming (6%) and professional (6%). Business categories that were
selected by the least number of people included horticulture, trades-persons,
education, communication, research, industrial/manufacturing and the health industry
(3% or less for each category).
Retail
Farming
Service
Health
Tourism
Transport
Indust/Manufacturing
Professional
Tradesperson
Horticulture
Education
Communication
Research
Figure 7: Question 2 -What category do you class your business in?
The abundance of responses from fields related to travel, tourism and the service
industry reflects the predominance of this industry in the Ruapehu area and how
intensely people involved in those fields were affected by the Ruapehu eruption.
Businesses that were involved in work related to tourism were affected by inaccurate
and sensational media reports. Media reports both in New Zealand and overseas
affected tourism by deferring potential tourists from visiting the area. This loss of
business caused a great deal of concern for those who were affected.
After nominating which category participants considered their business belonged to,
they were also asked to write a few words underneath to explain what their business
was concerned with. From the responses to this request, more detailed business
categories were formed. The aim of this was to gain a more detailed insight into
exactly what type of business the participant was involved with. This could then be
compared with financial losses to find out exactly what types of business suffered
financially as a result of the 1995-1996 eruptions.
Table 5 displays the categories that the businesses were grouped into. Business
categories that had the highest numbers included the farm industry, ski industry,
accommodation, motor vehicle services, the transport industry and retail.
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Doc # 498257
Question 3 - Is your business public or privately owned?
In response to the question “Is your business public or privately owned?” 86% said that
the business was privately owned, 13% said that the business was publicly owned and
1% said that it was a trust.
Question 4 - How many staff members are employed at this business?
The number of staff employed varied from business to business. In general, however,
most were small businesses and had between one and 10 staff members.
Table 5: Number of survey participants involved in each type of business.
Categories of Business
(manual selection)
Accommodation
Farm industry
Motor vehicle services
Transport
Ski industry
Retail
Flight services
Water sports
Service industry
Tourism
Horticulture
Air-conditioning/refrigeration
Professional
Information/communication
Rentals
Education/research
Food industry
Forestry
Roading
Veterinary services
Electricity
Trades person
Health
Adventure tourism
Hardware
Panel Beating
Plumbing/spouting
Security services
Industrial/manufacturing
Number of
Survey
Participants
26
15
15
14
13
11
10
9
8
7
6
6
6
6
5
5
4
4
4
3
3
3
3
3
2
2
2
2
2
Question 5 - What is the average annual turnover of the business?
Figure 8 shows the range of annual turnover for each type of business that answered
the Mount Ruapehu questionnaire.
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Page 55
1,000,000,000
100,000,000
10,000,000
1,000,000
Turnover ($NZ)
100,000
10,000
1,000
100
4
2
5
3
6
26
27
28
Tourism
25
29
Industrial
24
Service Industry
23
Advent. Tourism
22
Security Services
21
Plumbing
20
Education
19
Health
18
Rentals
17
Roading
16
Water Sports
15
Trades person
14
Information
13
Panel Beating
12
Forestry
11
Retail
10
Electricity
9
Transport
8
Professional
7
Flight Services
6
Motor Vehicle Services
1
5
Air-conditioning
Number of Respondents
4
Hardware
Accommodation
3
Veterinary
2
Farming
1
Horticulture
0
Food Industry
1
Ski Industry
10
Category of Business
Figure 8: Turnover of businesses that answered the Ruapehu survey
(logarithmic scale).
Question 6 - Please place a cross on the map to show where your
business or home is located.
People were asked to place a cross on the map supplied with the survey to indicate
where their business or home was located. The map was then divided into circular
zones, with each zone representing a particular radius around Mount Ruapehu. The
first zone was from 0 to 20 kilometres around the mountain. The zones following zone
1 (zones 2 through to 8) were drawn at intervals of 30 kilometres. Figure 9 shows the
arrangement of zones around Mount Ruapehu.
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Doc # 498257
30
Wairoa
Waiouru
Raetihi
National Park
Zone 1 1
Zone 2
Rangipo
Turangi
Tokaanu
Eltham
Stratford
Waitara
New
Plymouth
Figure 4.4 The arrangement of zones around Mount Ruapehu.
Zone 5
Zone 4
Lake
Waikaremoana
N
Awakino
Whakapapa Village
Te Kuiti
Otorohanga
4
Taumarunui
Lake
Taupo
Taupo
Kinloch
Tihoi
Mangakino
Putaruru
3
Te Awamutu
Raglan
Zone 3
Reporoa
Atiamuri
1
Rotorua
Tokoroa
Ngongotaha
Kawerau
Edgecumbe
Murapara
15
Zone 6
Scale (km)
0
15
30
Zone 7
Zone 8
Opotiki
Whakatane
Cambridge
Paeroa
5
Tauranga
Matamata
Te Puke
2
Mount Maunganui
Katikati
Waihi
Whangamata
Thames
2
r
Hamilton
ive
Huntly
iR
Ngaruawahia
g
an
u
1
ta
Port
Waikato
W
an
ga
r
Auckland
Ra
n
ve
iver
Ri
to R
ik
i
ika
Wa
Figure 9: The Arrangement of Zones around Mount Ruapehu
The greatest number of responses to the survey came from the zones closest to the
mountain (Figure 10). Zone 1 accounted for 8% of the total responses, zone 2
accounted for 31% of the total responses and zone 3 accounted for 13% of the total
responses. Zone 5 also had an excellent number of responses (26%) and most of
these responses came from an area northwest to northeast of the mountain area. In
zone 7 the responses tended to be split between the two areas of Hamilton and
Tauranga/Mt Maunganui. Zones 4, 6 and 8 only had limited responses to the survey
and so the results obtained for the perception section for these areas may not be
representative of the population.
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12%
3% 8%
5%
31%
26%
2%
0-20 km (zone 1)
21-50 km (zone 2)
51-80 km (zone 3)
81-110 km (zone 4)
111-140 km (zone 5)
141-170 km (zone 6)
171-200 km (zone 7)
200 km + (zone 8)
13%
Figure 10: Question 6 – Please indicate where your home or business is
located.
Perception of Volcanic Hazards
Question 7 - How likely do you think that an eruption from any volcano in
the North Island would affect your town or community?
Over 50% of participants responded that they considered it was “extremely likely” that
an eruption from any volcano in the North Island would affect them. This high figure is
representative of the fact that 81% of people that responded to the survey had been
affected by Mount Ruapehu. It is likely that the perception of the respondents had
been influenced by the recent Mt Ruapehu eruptions.
Perhaps a more appropriate way of analysing people’s responses is to look at where
the respondents were located, versus how likely they thought it would be that an
eruption would affect them. The following graphs (Figure 11) display this. In the first
graph (“Not Likely versus Location”) we see that there is a positive correlation. The
further away from Mount Ruapehu the location is, then the more people believed that
they were not likely to be affected from a volcanic eruption anywhere in the North
Island. Graph 4 has a negative correlation. In other words, the closer to Mount
Ruapehu the location is, then the more likely the respondents were to choose
“Extremely likely”. If we look at Graphs 2 (“somewhat likely) and 3 (moderately likely)
there is no significant trend. However, when you draw a best fit line through them and
compare them with graphs 1 and 4, then it is possible to see a transition from Graph 1
through to Graph 4, reflecting the change in belief the further away you go from the
mountain.
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2.5
2
1.5
1
0.5
0
Graph 2 - Number of respondents who chose "somewhat
likely" for Question 7 versus where respondent is located
Line of best
fit
0
2
4
6
8
10
Number of
respondents who
chose "somewhat
likely"
Number of
respondents who
chose "not likely"
Graph 1 - Number of respondents who chose "not likely" for
Question 7 versus where respondent is located
10
8
6
4
2
0
Line of best
fit
0
2
4
Location (zones)
8
10
Location (zones)
Graph 3 - Number of respondents who chose "moderately
likely" for Question 7 versus where respondent is located
Graph 4 - Number of respondents who chose "extremely
likely” for Question 7 versus where respondent is located
25
50
20
15
10
5
Line of best
fit
0
0
2
4
6
8
10
Location (zones)
Number of
respondents who
chose "extremely
likely"
Number of respondents
who chose "moderately
likely"
6
40
30
20
Line of best
fit
10
0
0
2
4
6
8
10
Location (zones)
Figure 11: Series of graphs looking at the relationship between peoples’
location and how likely they think they would be affected by a
future eruption.
Question 8, Question 9 and Question 10
If there was an eruption from a basaltic volcano in the North Island, which volcanic
materials do you think could potentially reach your community? (Basaltic eruptions
tend to be less explosive. Examples of basaltic eruptions include Mt. Tarawera 1886,
and the volcanoes of the Auckland Volcanic Field).
If there was an eruption from an andesitic volcano in the North Island, which volcanic
materials do you think could potentially reach your community? (Andesitic volcanoes
are moderately explosive. An example of an andesitic eruption is Ruapehu 1995/1996.
Other volcanoes that produce andesitic eruptions include White Island, Tongariro and
Ngauruhoe).
If there was an eruption from a rhyolitic volcano in the North Island, which volcanic
materials do you think could potentially reach your community? (Rhyolitic eruptions can
be very violent. Active rhyolitic volcanoes include the Taupo Volcanic Centre (Lake
Taupo), the Maroa Volcanic Centre, Okataina Volcanic Centre, and Mayor Island).
For each of these questions, a list of possible volcanic materials that could be erupted
by each type of volcano was supplied. A short definition of each volcanic material or
hazard was written alongside. Respondents could choose any number of materials on
the list as long as they thought it would reach their community in a future eruption. In
general the more familiar volcanic materials or hazards, such as ash falls and lahars,
were chosen more often than unfamiliar hazards. What follows is a summary of
participant’s responses to each of the different materials and whether or not they
thought that the material or hazard could affect their community in a future eruption.
• Don’t Know
In communities further away from Mount Ruapehu, it was more common for people not
to know whether volcanic materials would reach them or not. Respondents living close
to Mount Ruapehu felt they were more certain of which volcanic materials would reach
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them in an eruption. A number of people were unsure of what volcanic materials they
might receive in a rhyolitic eruption or basaltic eruption, but many knew what they
would be likely to receive in the event of an andesitic eruption.
• No materials
For a basaltic eruption, a small proportion of people thought that no materials would
reach their community. However for both andesitic and rhyolitic style eruptions, every
person who answered these questions thought that some type of volcanic material
would reach their community.
• Ash fall
Ash fall was the most common volcanic material selected by participants as likely to
reach their community if an eruption was to occur from a basalt, andesite or rhyolite
volcano. The widespread ash falls experienced during 1995-1996 Ruapehu eruptions
have most likely contributed to an awareness of this hazard.
• Volcanic Gases
Volcanic gas was the second most common hazard that respondents thought would
reach their location in a future eruption. In the Ruapehu eruptions, people could smell
volcanic gases adhered to the ash that fell. In this form, the gases were not at toxic
levels. The questionnaire did not differentiate between different levels of toxicity or
explain the different forms of volcanic gas. Therefore it is likely that the majority of
survey respondents only understood volcanic gases from their experience of the
Ruapehu eruptions, and did not consider them at toxic levels.
• Ballistic Fallout
A large number of respondents thought that they would receive ballistic fallout in the
event of an eruption. Out of those that responded, many did not live close to a
volcano, and it is therefore improbable that they would receive fallout. The fact that
large numbers of people selected ballistic fallout as an option is clearly attributable to a
lack of understanding of the hazard.
• Lava Flows
Despite lava flows being relatively unlikely to cover a widespread area and reach many
locations, a number of respondents still believed that it was possible that a lava flow
from a basaltic or andesitic eruption could reach their community.
• Lahars
Those living in zones close to the andesitic volcanoes Tongariro, Ngauruhoe and
Ruapehu, showed a heightened awareness of lahars, and believed that one could
reach their location. This is due to the fact that many lahars have occurred in historic
times, and thus the lahar hazard has a high profile. However, further away from the
high profile mountain area, fewer people selected lahars from an andesitic source as
realistic hazard.
• Floods and lahars down the Waikato River
A number of people recognised that floods and lahars down the Waikato River from a
rhyolitic source, would be likely to affect their community. The number of people that
selected this hazard as likely to affect them, was similar to the proportion that thought
they would be affected by andesitic lahars.
• Debris Avalanche
Respondents who lived closer to the cone shaped, andesitic mountains thought that
debris avalanches could affect their community. The majority of respondents living
further away from the mountains did not believe that debris avalanches were likely to
affect them.
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• Tsunamis
A high number of respondents who lived in zones near lakes, recognised that tsunamis
could affect their community if a volcanic eruption was to occur from a vent in the lake.
Examples of these zones include zone 3, which includes Lake Taupo, and zone 5,
which includes Lake Rotorua and a number of other lakes. In other zones that don’t
have lakes, very few people thought that they would be affected by a tsunami.
Question 11 – People’s knowledge of what to do during an eruption
Would you know what to do if:-
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Ash fell on the roads
Pyroclastic flow/surge occurred
A lava flow reached your
location
You were in the path of a lahar
Ash was falling & wanted to
drive car
Ballistic fallout reached your
location
Ash fell on the roof/in
downpipes
Ash fell on pasture
Ash fell on machinery
Ash fell on electrical equipment
Ash fell on crops/grass
no
yes
Ash was falling through the air
Percentage of Respondents
People are familiar with what to do when ash is falling through the air, when ash has
fallen on the roof and in the downpipes, and when ash has fallen on the roads (Figure
12). Areas of knowledge that are distinctly lacking include knowledge of what to do
when ash falls on crops or grass, what to do about ballistic fallout, what to do if a lava
flow reaches your location and what to do if a pyroclastic surge or flow occurred.
Type of Hazard
Figure 12: Respondents’ knowledge of what to do during an eruption.
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The results from question 11 indicate that for hazards that are unfamiliar (e.g. lava
flows and pyroclastic flows) people are unsure of the impacts and how to respond.
People are also unfamiliar about hazards that don’t concern them. For example, most
of the businesses that responded to this survey work in the tourism and service
industries. It is unlikely that people running these types of business will know what to
do if ash were to fall on crops because this issue does not concern them. However, if
someone involved in horticulture did not know how to deal with the problem of ash on
crops, then the results could be disastrous. It is essential that people are familiar with
how to deal with the specific problems associated with hazards that affect them
directly.
Because problems associated with ash fallout were common during the 1995 and 1996
Ruapehu eruptions, many New Zealanders who were caught in the fallout are now
familiar with how to cope with ash related problems. However, to fill the knowledge gap
about other hazards, education is required. There is a possibility in the future that
people may be faced with volcanic hazards that they have not directly encountered
before, and if they are previously informed about these hazards it will enable them to
take the appropriate mitigative action.
Volcanic Hazard Perception Results from other Surveys
Johnston (1997a; et al., in prep.) undertook two surveys, one before and one after the
1995 Ruapehu eruption. The surveys were concerned with two town’s (Hastings and
Whakatane) perceptions of volcanic hazards and how they had altered after the 1995
eruption. It was found that the 1995 Ruapehu eruption had served to both improve and
reduce community preparedness for future eruptions. Respondents that had been
affected by the eruption had gained a heightened awareness. In contrast, those that
lived close to Mount Ruapehu but had not been affected by the eruption, may have
gained the impression that in a future eruption from Ruapehu they would once again
escape any negative impacts.
The 1995–1996 Ruapehu Eruptions
Question 12 - How did you first learn that there was an eruption occurring
from Mt Ruapehu?
Most respondents said they first knew there was an eruption occurring from Mt
Ruapehu when they saw, heard or experienced the eruption first hand (Figure 13). Out
of these people, most said they saw the ash cloud approaching.
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Internet
Brochures
Magazine
Loss of signal from Crater Lake
Scientific Alert Bulletin
Television
Newspaper
Radio
W ord of mouth
Saw, heard, experienced the eruption first hand
0
20
40
60
80
100
Number of respondents
120
140
Figure 13: How did you first learn that there was an eruption occurring
from Mount Ruapehu?
The second and third most common methods of finding out that an eruption had
occurred was via the radio, and then by word of mouth.
Many participants also
pointed out that after they saw the ash cloud they turned on the radio to find out more
information.
Short of seeing an ash cloud approaching, the radio will be one of the first sources to
disseminate information in regards to a future volcanic eruption. It will continue to be a
major source of information for people as the eruption continues. It is essential
therefore that information broadcast from a radio station is up-to-date, accurate and is
not contradictory.
Effects of the 1995-1996 Ruapehu Eruptions
Question 13 – Were you affected by the Ruapehu eruptions in any way?
Because the survey was sent to areas where people were more likely to have
experienced problems from Mt Ruapehu, the number of respondents who were
affected by the Ruapehu eruptions was high (81%). Only 19% of people who
responded to the questionnaire were not affected by the Ruapehu eruptions in any
way.
Figure 14 is a graph that displays location of the respondent versus whether the
respondent was affected by Mount Ruapehu. The trend in the graph shows the further
away from Mount Ruapehu, then the less people were directly affected by the 1995
and 1996 eruptions.
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Percentage of people affected
120
100
80
Line of best
fit
60
40
20
0
0
2
4
6
8
10
Location (zones)
Figure 14: Location of the respondent versus whether they were affected
by the 1995-1996 Ruapehu eruptions.
Question 14 – Did you suffer any damage,
inconvenience in relation to any of the following:-
disruption or any
Most of the damage or disruption that occurred could be attributed to problems that
arose due to the falling ash.
• Horticulture
Over half of the people that experienced damage in relation to horticulture said that
their plants and vegetables in gardens at home had suffered from the ash fall. Some
respondents noted that plants coated with ash had to be washed down. Other
respondents noted that some plants were burned by the ash and then had proceeded
to either die or experience poor growth in the following seasons.
• Livestock
Livestock were affected when they ingested ash that had fallen on pasture. Some
farmers found that their stock suffered some slight ill effects from the ash such as
weight loss, but there were no reports of stock deaths from survey respondents.
Household pets, such as dogs and cats, were also found to suffer problems from ash
adhering to their feet and coats. Other animals and insects that were affected due to
the ash fallout included fish and bees.
• Buildings/structures
The majority of survey participants that were affected by the Ruapehu eruptions
experienced problems with ash falling on structures. Eighty people noted that ash had
fallen on the roofs of buildings, and 41 people reported that ash had fallen in the
downpipes and guttering. Roof guttering that had collected large amounts of ash was
at risk of, or in some cases did, collapse. Those people whose downpipes fed water
tanks were at risk of polluting their supply of water if the ash was not removed from the
guttering prior to the next rainfall. The ash also created corrosion problems with iron
guttering and roofs. Many of these problems have been reported in other studies (for
example, Johnston et al., 1996; Johnston, 1997a; Treblico, 1997).
Eighteen people had to deal with ash that had collected on concrete paths and paved
areas, and four people noted that ash fell into their swimming pool. Ten people found
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that ash managed to infiltrate buildings. Other complaints involved ash on verandahs,
glasshouses and in drains.
• Machinery
Again the problems that questionnaire participants had with machinery were directly
related to ash fallout. The abrasiveness of the ash was prone to causing wear to
motors and to general pieces of machinery. Machinery and tools were at risk of
corrosion if they came into contact with the ash. One person noted that they had
problems with ash falling on electronic gear. Air-conditioning systems were severely
impacted by the ash in the atmosphere. Respondents noted that air-conditioning units
as far away as Tauranga and Hamilton experienced problems with the ingestion of ash
into the filter system.
• Road vehicles
A substantial number of respondents (39) stated that ash fell on their motor vehicle. A
further 17 respondents elaborated on this saying that the acidity of the ash caused
corrosion on the motor vehicle. Fifteen participants noted that ash clogged up the air
filters in the vehicles, and three said that ash had blocked the radiator vents.
• Roading
Six respondents found that ash falls on the roads were stirred up by moving traffic and
caused a dust problem. This reduced visibility for drivers. One respondent noted that
when the ash became wet, then roads became slippery to drive on. Ash falls were so
thick in some areas that the road markings were no longer visible on the road. A few
respondents (7) were inconvenienced by road closures and detours that occurred as a
result of the ash falls.
• Water supply
Sixteen respondent’s water supplies were affected by volcanic ash. Ash fallout from
the eruptions fell into guttering, and from there made its way into personal water tanks.
As a precaution people were advised not to drink their water or to boil it before doing
so. Another water-related ash problem was with respect to animals’ drinking water.
Four respondents reported that water troughs were contaminated with ash. In
response, farmers covered their water troughs.
• Electricity
There were only a few responses related to problems with electricity. Some of the
problems noted by survey participants were:- the electricity system suffered corrosion due to the acidity of the ash;
- insulators shorted out, causing a power cut;
- a power line fell down due to the weight of the ash on the line; and
- power surges occurred in some parts of Auckland.
• Sewerage/ Stormwater drainage
Only one respondent noted that they suffered any damage or disruption with regards to
the drainage system.
They said that a stormwater drain was blocked and
malfunctioning.
• Telecommunications
In regards to the telecommunication network, people were inconvenienced when
phones were overloaded due to the high usage. Ash that had fallen on the telephone
wires were said to have caused “crackling” that could be heard when having a
conversation on the telephone. Two people also noted that radio communications
were disrupted and the signal was lost as the ash fell.
• Aircraft and Air Travel
Ash falling on aircraft (and the associated corrosion) was a problem cited by only a few
respondents. Airline travel was disrupted, as aircraft could not fly while ash was falling.
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This caused 20 respondents to be either delayed in their travel, have to make
alternative arrangements, or have to take a detour.
• Other
There were a variety of other structures and services that were affected by ash fall from
the Ruapehu eruptions. Falling ash directly affected boating and fishing, staff who had
to work outside and the ski industry.
Question 15 – Was the damage or disruption long term or short term?
‘Long term’ and ‘short term’ were not defined in the original questionnaire but were left
up to respondents to decide whether they felt the eruption was a mere inconvenience
or whether it had more far-reaching effects. For three-quarters of the respondents, the
damage or disruption was long term.
A number of people felt that the long term effects of the eruptions would last for years.
One respondent commented that, “This will take at least three to five years to correct.
We need to rebuild goodwill back to our 1992-93 credibility”. Another survey
respondent thought a recovery time of four to five years was more realistic than a
previous estimate of three years. It is possible that the warm weather and the lack of
snow experienced during 1998 winter may have delayed this recovery even further.
Question 16 - How did you solve or fix the problem/s?
Most respondents said that they solved any problem that they had by themselves. Of
those that did need to turn to others for help, a list of those people is shown in Table 6.
There was no particular organisation or person that was asked most often. Instead of
turning to one general information provider, those that asked for assistance tended to
turn to whoever could solve the particular problems that respondents faced. For
example, if a respondent’s guttering and downpipes needed attention, then the local
plumber (the expert on fixing that particular problem) was asked for assistance.
Table 6 : How respondents solved or fixed problems caused by the
Ruapehu eruptions.
How did you solve or fix the problem/s?
By yourself
Did not solve or fix the problem
Had help from others (did not identify who)
Engineering workshop
With help from community volunteers
Advice from the local radio station
Water blasting contractor
Veterinarian
Local networks
Department of Conservation staff
Local plumber
District Council
An advertising campaign helped recovery
Army (held information that it had received from other sources)
Used information given in the scientific alert bulletins (IGNS)
Volcanologists
Had to generate summer business to solve financial problems
Rang an airline in USA that had experienced an eruption before
Information from the television
Farm advisers
Bank manager
Staff at own business
Earthquake Commission (EQC)
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No of People
112
26
9
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
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Service station (car washing)
Sought expert advice in remedial measures
Paint specialists (for protective coating from corrosion)
Plant engineer for air-conditioning from a hotel
Handy-man
1
1
1
1
1
Question 17 - Was any equipment that you needed to use in response to
the eruption readily available?
Fewer than 60% of participants didn’t need to use any equipment in response to the
eruption. Of the 41% that did need equipment, about a quarter had difficulty in locating
or getting hold of the equipment that they needed to use. Most of those that had
difficulty in procuring equipment said that they were looking for dust masks but couldn’t
obtain them easily. After dust masks, water-blasters were the next most sought after
piece of equipment that were difficult to procure. Other items that were mentioned as
difficult to get hold of included a high pressure pump, rain wear, polythene sheets,
containers to store fresh water in, a hose and sweeper unit and a spouting scoop.
Question 18 - Did you discover any useful hints in coping with the
problems that you faced?
Just under 50% of respondents said that they did have a useful hint that they could
share. Table 7 summarises the set of useful hints that participants shared. Most of the
hints related to problems with ash falling on objects, or problems with ash causing
corrosion.
Table 7: Common hints suggested by survey respondents.
Category
Common Hints Suggested by Survey Respondents
Animals
-
Plants, shrubs
-
Ash on roof
Ash in downpipes
-
Machinery
-
Airconditioning
-
Road Vehicles
-
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Move stock from ash affected area.
Cover water troughs so ash does not fall in.
Keep pets free of ash. If they have been contaminated, clean them (bath
or brush) .
Wash ash off leaves with water and detergent before ash consolidates.
Some people used pressure sprays to remove the ash.
10 people hosed or water blasted the roof clear of ash (one person
ensured the downpipe wasn’t clogged while doing this).
One person noted that the “water made the ash like concrete” and
suggested shovelling ash from the roof instead.
Remove or block downpipes as soon as there is ash fall or before
washing or removing ash from the roof.
Remove ash from the gutters manually, don’t wash down the downpipes.
To avoid the ash staining the PVC downpipes, mix water and baking soda
and scrub.
Ash is likely to block soak-holes if it receives wash-down water. Remove
the bottom section of the downpipes and disperse water elsewhere.
Protect machinery by covering it, storing it, keeping doors closed or
keeping machinery clean.
Air vents need to be cleaned or replaced.
Turn off air conditioning during ash fallout.
Needed additional filters to the major air intakes, therefore purchased a
roll of agricultural “frost cloth” to use as a filter.
Additional covers for vents/doors of the air-conditioning system consisted
of canvas sewn together.
Asked radio station to broadcast advice to turn off air-conditioning
equipment.
Wash ash off car thoroughly (two people recommended to do so with
detergent).
Don’t use windscreen wipers and windscreen washer with ash on the
windshield as it will scratch the windscreen.
Keep car under cover and limit vehicle use until ash falls are over.
Blow as much ash off car first, then wash with water.
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Water
People
-
Ash problems in
general
-
Service vehicles and equipment regularly (For example change the air
filter).
Don’t unwind car windows during an ash fall – the ash gets caught inside.
Cover open water tanks during ash fall.
Shut down water supply during ash fall.
Provide spare containers for drinking water.
Boil drinking water that has been contaminated by ash.
Block stormwater drains while washing ash away.
Keep indoors during ash fall, otherwise wear a dust mask outside.
If working outside and ash begins to fall, stop working until the conditions
change.
For food hygiene, staff needed to change overalls 2 to 3 times daily
during ash falls, instead of once.
Use advertising to regain customer confidence.
Be conscious that ash is abrasive, and don’t wipe off surfaces.
Ensure ash is contained, stabilised or removed as soon as possible.
A variety of less common hints were suggested regarding swimming pools, boats,
aircraft and management issues. These can be viewed in Appendix III.
One problem regarding the useful hints is that many people had different ideas on how
to cope with the same problem. For example, for the problem of ash getting into the
down pipes people had different suggestions on what to do. Some simply said to hose
the downpipes out, some said to disconnect the down pipes immediately after an ash
fall, some said to hose from the top of the downpipes and collect the ash at the bottom
and some said to remove as much ash as possible before hosing down. Some of
these responses were correct, while some were only partially correct. It seems that the
appropriate information on how to deal with ash in the downpipes only partially reached
some of the respondents. They used what information they had retained to solve their
problem. However, while the solutions they devised worked for them, it may not have
been the totally correct method. For example, hosing out the downpipes without
collecting the ash at the bottom may have worked in the short term, but it may have
caused problems further down the line for wastewater systems.
Another problem that the Ruapehu eruptions may have inadvertently contributed to, is
what is acceptable to do in a small eruption, may not necessarily be appropriate for a
larger eruption. An example of this is the problem of ash falling on a roof. Because the
Ruapehu eruptions only produced a light ash fall on roof tops, many people dealt with
the problem by washing the ash off the roof with water. In a heavier ash fall, this
practice should be discouraged as water causes the weight of the ash to increase
substantially. The increased weight of the ash could cause roofs to collapse.
Many hints that people provided were similar to those suggested from the experiences
of past eruptions overseas, and reinforces the fact that those mitigation practices are
successful. Some of the hints provided are useful for New Zealand conditions. For
example many people in New Zealand still rely on uncovered water tanks for their
water supply and they found it was necessary to cover these when ash was falling.
Also, many New Zealanders own boats and found they had to take mitigative actions to
protect their boats from corrosion and damage to boat machinery. Management issues
regarding volcanic hazards and volcanic eruptions were also revised as a result of
Mount Ruapehu erupting. It is possible to learn from overseas experiences about
management during a volcanic eruption, but it is also necessary to develop a system
that works for New Zealanders in New Zealand conditions.
Question 19 - Did you suffer any economic loss that was related to the
Ruapehu eruptions of 1995 and 1996?
Figure 15 shows the amounts of money (NZ$) lost by survey respondents as a result of
the Ruapehu eruptions. The most common amount of money lost was in the vicinity of
NZ$10,000.
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Figure 15: Question 19 – Did you suffer any economic loss related to the
Ruapehu eruptions?
It is also possible to separate out the different businesses who answered the survey,
and look at the range of loss for each (Figure 16). Six types of business did not suffer
any economic loss. Those businesses were veterinary services, forestry, panel
beating, information services, roading and plumbing. In fact, many of the businesses
involved in the service industry, such as panel beaters, plumbers and veterinary
practices, experienced an increased turnover. Their services were in demand to deal
with the effects of the eruption. Major losses were experienced by the ski industry,
tourist industry, accommodation services, retail and those involved in water sports.
Respondents that ran businesses involved with the ski industry quoted losses of
between NZ$50,000 and NZ$6,000,000. Tourist operators claimed that they had
experienced losses ranging from hundreds of dollars to NZ$3,000,000. Those
respondents that ran businesses to do with accommodation, retail or water sports said
that they suffered losses ranging from hundreds of dollars to NZ$1,000,000.
10,000,000
Loss (NZ$)
1,000,000
100,000
10,000
1
3
2
4
25
26
27
28
Tourism
24
29
30
Industrial
23
Service Industry
22
Advent. Tourism
Security Services
21
Plumbing
20
Education
19
Health
18
Rentals
17
Roading
16
Trades person
15
Information
14
Water Sports
13
Forestry
12
Panel Beating
11
Retail
Electricity
10
Transport
9
Professional
8
Motor Vehicle Services
7
Flight Services
Ski Industry
Number of
Respondents
6
Air-conditioning
5
Hardware
4
Accommodation
3
Veterinary Services
2
Farming
1
Food Industry
0
Horticulture
or less
Category of Business
Figure 16: Losses (NZ$) suffered by different types of business
(Logarithmic Scale).
Two other business categories (electricity and education) also suffered major losses.
However, there were limited replies from businesses of these types and therefore an
accurate range of loss can not be determined for either. Most of the other business
categories that suffered loss, generally had losses of below NZ$100,000.
It is not possible to calculate a total loss for the Ruapehu eruptions from the losses
reported by survey respondents. The sample size of the survey is too small, and the
coverage of businesses in the survey is not comprehensive.
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Page 69
An estimate of losses as a result of the Ruapehu eruptions has been calculated by D.
Johnston (pers. comm., 1999). He estimates that just under NZ$130,000,000 was lost
as a result of the eruptions. This figure accounts for losses to tourism, electricity
production, central government, aviation, regional and district councils, agriculture and
insurance companies. This estimate in itself is not comprehensive, and can only
represent a minimum loss as opposed to a total loss.
Question 20 - Did you or your family make any lifestyle adaptations in
response to the Mount Ruapehu eruptions?
In response to the Mount Ruapehu eruptions, 33% of participants said that they did
make some lifestyle adaptations while 67% said they did not make any adaptations. Of
those that did make lifestyle adaptations, there were a wide range of changes. Some
people made not only one, but two or three different adaptations. Some of the more
common adaptations included having to wear face masks, making an effort to store
essential emergency items such as food, water and batteries, tightening expenditure,
keeping indoors as much as possible and having to stop skiing for a number of months.
Table 8 displays the range of responses for question 20.
Question 21 - Did you or your family experience any physical health
problems caused directly from the products of the volcano?
A small percentage of respondents (17%) did experience physical health problems
caused directly from the products of the volcano. The two main health problems that
were cited were eye irritations and breathing problems due to airborne ash. As a
subset of breathing difficulties, a number of people also specified that they had either
developed asthma or suffered an increase in severity and occurrence of asthma. While
these respondents felt that they had suffered from asthma as a result of the eruptions,
more detailed studies have in fact shown that there was not any overall significant
increase in asthma symptoms among asthmatics (Bradshaw et al., 1997).
Other health problems caused by the ash included skin rashes, development of
coughs, sore throats and nausea.
Table 8: Lifestyle adaptations made in response to the Ruapehu
eruptions.
Category
Lifestyle adaptations
Frequency
Storage of essential items eg. food, water, wood, first aid kit,
batteries.
Carried mask in car/where you went.
Obtained or wore face protectors/masks.
Packed (or ready to) clothes/treasures for evacuation.
Kept a torch handy.
9
Financial
Expenditure tightened.
6
Lifestyle
Kept indoors as much as possible.
Carried own water.
Kept in touch with neighbours/family.
Had to adapt to the condition of the day.
Windows closed.
Care and cleaning.
No longer put loo blue in the cistern.
Avoided drying washing when there was ash fallout.
Family evacuated village.
4
1
1
1
1
1
1
1
1
Work
Looked for other/extra work.
Let employees go, ran business on own for a while.
3
2
Essential items
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5
3
3
1
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Did extra work at home.
No work for a period of time.
Changed work patterns/worked where ash wasn't.
On duty all hours.
Updated/improved emergency response procedures.
Redirected marketing efforts to differing sources.
1
1
1
1
1
1
Recreation
Not able to ski for a couple of months.
Travelled to South Island for skiing.
Made extra time available for volcano viewing.
No fishing in river for a year.
7
2
3
1
Vehicles
Ensured vehicles always full of fuel.
Kept car in garage.
Did not drive unless essential.
Finally put up carport - car protection.
Awareness of living next to a volcano.
More prepared for next one.
Read about eruptions and precautions.
1
1
1
1
1
1
1
Lobbied parliament for recognition and compensation.
1
Awareness
Other
Question 22 - Did you feel that the eruption caused you or your family
members to suffer any stress related problems?
tu
re
in
g
ur
s
fu
an
ty
of
cle
in
ce
rta
ef
e/
tim
un
fo
rt
i
n
wo
rk
of
e
e
dg
w
le
kn
o
lo
ng
ru
p
lp
he
of
k
of
ck
la
ho
ti o
ns
c)
(e
q
ss
tre
cia
ls
la
c
ap
th
"w
ha
ba
d
fi n
an
pe
ns
fo
rm
ne
at
io
n
xt
?"
50
45
40
35
30
25
20
15
10
5
0
in
Percentage of respondents
In answer to question 22, 45% of participants felt that they or their families had suffered
stress as a result of the 1995 to 1996 Mount Ruapehu eruptions. The most common
causes of stress were due to being uncertain what was going to happen next, financial
pressures, and a general lack of knowledge about volcanic eruptions. Other causes of
stress were “bad information” that had been given to respondents, lack of assistance in
regards to insurance assessors, longer work hours, the time and effort involved in
cleaning up and an uncertainty of the future (Figure 17).
Type of stress
Figure 17: Types of stress suffered as a result of the Ruapehu eruptions.
Question 23 - Did you encounter or do you perceive any benefits from the
eruptions?
The majority of respondents (62%) said that they did not perceive any benefits from the
1995 and 1996 Ruapehu eruptions, while 38% said that they did see some benefits.
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The range of benefits experienced is listed in Table 9. The benefit that was most often
quoted by respondents was an increase in plant and grass growth as a result of the
ash fall from Mount Ruapehu.
Table 9: Range of benefits from the Mount Ruapehu eruptions.
Category
Environment
Benefits
Increased grass and plant growth.
Improved fishing, trout bigger.
Less weed growth in waterways.
Lake Taupo supposedly cleaner (filtered).
More Business
Increased income from sightseeing flights.
Increased income, more air-conditioning service work.
Increased sales on specific hardware products – for
example, water-blasters.
More business, groups stay in motels at Taupo longer.
Provided cleaning services to the council and businesses.
More work repainting cars, more tourists - more dings.
Car air filter sales up.
Sold more hardware, dust masks, etc.
Made money from helping others with home maintenance.
Increase in plumbing and drain laying.
Increased income from equipment rented to the media.
Opened up another business.
Extra staff time and revenue for period of time.
Tourism
Tourism potential of an active volcano.
Public relations that the area received will benefit for years
to come.
Awareness
and Gained improved understanding of hazards from Mt
understanding
Ruapehu and of successful mitigation measures.
The volcanic eruption increased awareness about volcanic
hazards in general.
Learning curve about eruptions.
Realised it can happen to me.
Advice given out regrading affects of ash on livestock.
Study undertaken on the effects of ash.
Community
Community came together to help each other.
support
Risk management Company related risk management policies in order.
Others
Financial assistance was gained through television
advertising.
Flight was detoured - got to see another part of world for
free.
Now have memories that will never be forgotten.
A lesson to not put all your eggs in one basket.
No of People
19
2
1
1
5
1
1
1
1
1
1
1
1
1
1
1
1
8
2
1
1
1
1
1
1
2
2
1
1
1
1
Question 24 - Did you turn to any of the following organisations to ask for
any advice or general information during the Mount Ruapehu eruptions?
The local radio station was where most people turned to receive information (Table
10). While the question is worded “to ask for advice”, many people acknowledged that
they did not actually ask the radio station for advice, but instead listened to the
presenters to gain information on the eruptions of 1995 and 1996.
The Institute of Geological and Nuclear Sciences, the District Councils, and the
Department of Conservation all fielded a number of inquiries from people who wanted
information about Mount Ruapehu.
A variety of other organisations were contacted for advice. The type of organisation
contacted depended on the respondent’s need, so consequently a whole range of
organisations were called on.
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Table 10: Organisations that respondents turned to for advice or general
information during the 1995-1996 Ruapehu eruptions.
f
96
35
18
17
15
14
11
8
5
5
5
3
3
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
Organisation
Did not turn to any organisation for information
The local radio station
Institute of Geological and Nuclear Science
District Council
Department of Conservation
Civil Defence
Insurance Companies (other than the EQC)
Regional Council
The New Zealand Police
NIWA (National Institute of Water and Atmospheric
Research)
Television news
City Council
Earthquake Commission (EQC)
Newspapers
Civil Aviation Authority
The New Zealand Army
SPCA
Farm adviser
Information hotline phone number
Parliament
Ski/snow reports from mountain ski fields
Metservice
Airways Corporation of New Zealand
Massey University soil science department
Animal health laboratory
Veterinarian
Volcano cam – updated pictures of Mt Ruapehu on the
Internet
Soil conservation
Botanical gardens
Hotel Engineer
Local hospital
Question 25 - Were you able to locate and contact these people with
ease? If yes, please list how you already knew of, or how you found out
where to contact these people.
There were 7 respondents who said that they had difficulty in contacting organisations
that they wanted to talk to. Phone overloads appeared to be a contributing factor to
this.
If they were looking for information, most people contacted organisations that they had
made contact with on a previous occasion. For those that had not made previous
contact, the most common way of locating an organisation was to do so using the
telephone book. Other common ways of getting in touch were through meetings that
were arranged, by using information broadcast on the radio or television, or through
standard procedures.
Some respondents knew the physical location of the
organisation and travelled there themselves to make contact.
Instead of approaching an organisation, two survey participants were actually
contacted by particular organisations. The organisations required accommodation
while they were staying in the area close to Mount Ruapehu, and assistance in
cleaning up ash.
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Question 26 - If you sought advice from more than one organisation, who,
in your opinion, was the most helpful?
The results of the survey indicate that no organisation in particular was better than any
other. Most respondents noted that different organisations provided different services
and therefore could not be judged as “better” or “worse”. Most had praise for the
different organisations they contacted, stating that the quality of the information
provided was high and that the organisation shared their concerns.
A number of comments were provided regarding the radio stations and insurance
companies. It was felt that at times, the information provided from these places was
less than helpful.
Question 27 – How would a future eruption from Mount Ruapehu affect
you if your home, business or organisation was in the path of falling ash
and the season was…
Question 27 was asked in order to look at the impact that a small volcanic eruption
would have on businesses in different seasons. Table 11 summarises these impacts.
Table 11: Impact of a volcanic eruption from Mount Ruapehu in different
seasons.
Season
Impact of the eruption
Winter
-
Spring
-
Summer
-
Autumn
-
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Great to extreme impact for the ski season.
Less of an impact for general tourism, as it is the off-season.
Quiet time for horticulture, many plants are dormant.
Quiet time for farming, so slight to great impact.
Great impact for fishing.
The cold, wet and long hours of darkness during winter complicates
matters.
Great impact on the ski season.
Great impact on tourism as the weather warms up and tourists
increase in numbers.
Great to extreme impact on farming (new animals are born, grass
growing time, milking, general stock grazing problems due to ash
fall).
Great impact on horticulture (planting, crops flowering, setting fruit,
pollination of plants, demand in plant sales).
Great impact on fishing, boating and other outdoor activities.
Busiest period for tourism, so a great to extreme impact if an
eruption were to occur.
Slight to extreme impact on the ski industry (Knocks confidence for
the up and coming ski season, general period of summer
maintenance).
Great impact on fishing, boating, jet-skiing and other outdoor
activities.
Great to extreme impact on farming (animals still being born at this
time, hay season, dairying, animals drinking greater amounts of
water, ash fall may prevent grazing).
Great impact for horticulture (fruit ready for harvest, retail of flower
and vegetable plants).
Aerial applications to farms at a peak.
An eruption during summer would have less of an impact because
there would be fewer hours of darkness.
Great impact to air conditioners - higher use of air conditioning
during summer would be problematic if ash fall occurred.
Slight to extreme impact on farming as it is a quieter time of year.
Slight to great impact on tourism (end of the main summer tourism
season).
Slight to great impact for fishing, hunting, waterskiing, kayaking and
other outdoor pursuits.
Great to extreme impact on the ski industry (continuation of
maintenance program, would knock confidence for the coming ski
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season).
Great impact for horticulture (some cultivation, harvesting).
Comments
The last page of the Ruapehu survey was devoted to comments provided by the survey
participants. There were many interesting comments, and a summary of some of these
is presented in this section. The full list of comments can be found in Appendix III.
• The Media
There were a great number of complaints concerning the media. Many thought that the
media were negative, sensationalist and provided inaccurate information.
Respondents thought that this type of reporting discouraged visitors from coming to the
affected area. The overseas media also blew the event out of proportion, and this
served to dissuade overseas tourists from visiting the area. Survey participants felt
that the negative publicity has had a long-term impact on visitor numbers.
• Volcanic Hazards
One respondent located at a distance from the erupting Mount Ruapehu, said that they
used the live “Volcanocam” on the Internet, to predict if there would be any problems
from Mount Ruapehu. If there were pictures of an erupting Mount Ruapehu broadcast
over the Internet, then there was a possibility of ash reaching their location if the wind
was blowing in the correct direction.
• Corrosion from Acidic Ash Particles
A number of comments were made by respondents stating that where ash had fallen
on metal surfaces and had not been removed, then the corrosion problems were long
lasting. Survey participants said that they had suffered long term corrosion effects with
metal objects such as guttering, roofs and nails in the roof.
• Soak Pits
A few respondents noted that they had problems with ash collecting in their soak pits.
One respondent wrote, “It is my view that there exists now a problem on many
properties where soak holes have become less efficient due to the build up of ash
covering over the normally permeable layer of more open material into which rainwater
normally discharges, usually about 5.5 to 7.5 metres below natural ground level.”
• Management Issues
Some of the comments that respondents provided regarding management of the
Ruapehu eruptions are summarised as follows.
- Some people thought that authorities were caught short and out of their depth.
- There was some discussion of Civil Defence’s perceived inadequate management
of the situation, and the lack of information available from them.
- Respondents stressed the need for continual, up-to-date information on the state of
the roads, water supply, etc.
- There was a feeling that more resources were needed for scientists monitoring the
volcanoes.
- One respondent suggested that where an impending eruption can be predicted,
people should be forewarned so that businesses can prepare (for example, cut
down on spending) before the event.
- It was suggested that the purchase of a mobile doppler radar would be useful for
monitoring ash plumes.
- Another suggestion by one respondent was to put an extra page in the telephone
directory stating what to do, and who to contact in a volcanic eruption.
Conclusions and Recommendations for Businesses
The perceptions of people who answered the survey were largely constructed from the
recent experience of the Ruapehu eruptions. Most respondents had a heightened
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awareness of a number of andesitic volcanic hazards, but knew less about unfamiliar
hazards from rhyolitic or basaltic volcanoes.
Mitigation measures used by respondents to counter the effects of ash were similar to
those determined from past eruptions overseas, although in some cases the
techniques used were not entirely correct. This may be due to incorrect information
being given to the public or to respondents’ misinterpretation of the information. To
ensure that the mitigation measures employed by the public in a future eruption are
correct, it is essential that accurate and clear information is given to the public. This
will assist in eliminating as much error as possible.
Results and comments from the 1995-1996 Ruapehu survey indicate that many
businesses were unprepared for a volcanic eruption. It is recommended that
businesses take responsibility for preparing their own plan to deal with the effects of a
future eruption. Some suggestions for planning for disaster include:- Establish a communication network made up of people both in and out of the
workplace.
- Be prepared for disasters of many kinds. Know what you are covered for under
insurance.
- Protect critical records. Keep backups of computer files, and keep a copy of critical
records in a secure place off-site.
- Consider employee safety.
- Identify an alternative business site that can be used following a disaster.
- Consider management succession.
- A disaster may strand employees at work. Ensure there are supplies at work and
know how to turn off workplace utilities in a disaster.
- Depending on the type of business, there may be even an increased demand for
goods or services after a disaster (Klimas, 1993; Arvizu, 1995; Barrier, 1998; Offer,
1998).
This document was approved for issue by Environment Waikato on (26 May 1999). It
is intended to review the document in 2003/2004. Note that the Civil Defence Act 1983
has now been replaced by the Civil Defence and Emergency Management Act 2002.
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