Volcanoes - Ministry of Civil Defence and Emergency Management

approaches can be used:
• Policy and management measures that reduce the
likelihood of damage and/or failure.
• Engineering design measures that reduce vulnerability.
• Preparedness and response planning to deal with
consequences of the event.
Mitigation options should be evaluated in terms
of risk reduction and the benefits or opportunities
created. In selecting any appropriate option or options
the cost of implementation must be balanced against
the benefits derived from it. Limitation on the building
of permanent structures in high-risk areas is a low-cost
mitigation measure.
Pre-planning can reduce the severity of ash
impacts. Mitigation, planning and preparation measures
should include the following activities:
• Conduct a vulnerability analysis of equipment and
facilities to determine which would be the most
affected and which are adequately protected.
• Identify appropriate methods of protecting
vulnerable equipment and facilities.
• Develop a priority list of facilities that must be kept
operative versus those that can be shut-down during
and after ashfalls.
• Identify effective and efficient ash-removal methods
for equipment and facilities.
• Establish plans to implement ash mitigation
measures containing procedures for: warning and
notifying of potential ashfalls, reducing or shutting
down operations, accelerated maintenance and ashclean-up
operations.
• Develop robust and tested connection of response
and mitigation plans to early warning systems
(GeoNet) in an integrated warning system model.
MITIGATION MEASURES DURING A CRISIS
Near-vent hazards including lava flows, ballistic
block impacts, pyroclastic flows and surges, lahars and
lightning strikes from ash clouds present a high risk to
life and damage to facilities in near-vent areas, but the
extent of these hazards is mostly limited to within a few
kilometres of the vent except for lahars which present
a more extensive hazard. Apart from the evacuation of
people and removal of transportable assets (if possible),
there are few or no mitigation options available to preexisting
facilities to counteract many of these hazards.
Past eruptions illustrate the vulnerability of
urban areas receiving only a few mm or cm of ash,
usually distant to the eruption vent. This thickness is
still sufficient to cause disruption of transportation,
electricity, water, sewage and stormwater systems.
However, most systems, if affected only by thin ashfall
(