Risk Wise

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1. Our broad assessment suggests that it is inevitable that the Asia

Pacific will suffer one or more ‘mega-disasters’ in the 21st

Century that significantly impact millions of people. Previously

it has been argued that a million-fatality earthquake in the

Himalayan belt of south Asia is likely, and we would argue that

megacities (cities with more than 8 million people) in China,

Indonesia and the Philippines are also candidates for this type

of event (Case Study 1). As far as we are aware, the case for

volcanic disasters of this scale has not been argued, but our

analysis suggests that millions could be seriously affected by a

volcanic disaster in the Philippines or Indonesia (Case Study

2). Finally, the current population explosion in the mega-deltas

of Asia (e.g. Bangladesh, Burma), combined with increasing

vulnerability as a result of climate change, indicates that a flood

or cyclone event affecting tens of millions is also likely.

2. Of this study’s primary focus countries, Indonesia and the

Philippines stand out as having very large populations exposed

to multiple hazards, with a high potential for massive single-

event impacts.

3. Pacific countries have a high potential for catastrophic disasters

that may affect large proportions of their populations, over-

whelming their national capacity to respond.

4. The gaps in natural hazard information available for developing

countries are vast, especially when compared to developed

countries. These gaps are often large enough to preclude any

meaningful hazard/risk assessment.

Case study 1: Manila – a megacity with a

very high earthquake risk

The 18 million residents of Manila in the Philippines dwell in an

area particularly vulnerable to earthquakes, with the city sustaining

heavy damage from earthquakes at least six times in the last 400

years.

In part this results from movement on the Marikina Valley

fault system which cuts through the north-eastern part of the city.

Studies suggest that magnitude 6-7 earthquakes are generated on

this fault every 200-400 years.

A combination of rapid urbanization, its location on a floodplain

prone to amplified ground motion and liquefaction, and frequent large

earthquakes lead to a high potential for an earthquake to impact a

large proportion of Manila’s population. Indeed, our analysis suggests

that Manila is the Asia-Pacific megacity most at risk to earthquakes,

with magnitude 5 earthquakes occurring on average once every 37

years. A magnitude 5 earthquake centred near Manila is predicted to

significantly impact several hundreds of thousands of people, and a

larger earthquake striking at Manila’s centre may be catastrophic.

Across the Asia-Pacific region, the countries with the largest total

populations exposed to very high earthquake hazard are China, India,

Nepal, Philippines and Burma; while megacities with a particularly

high risk from earthquakes include Dhaka, Bangladesh and Beijing,

China. Countries with a high percentage of their populations exposed

to very high earthquake hazard are Vanuatu, Solomon Islands, Nepal,

Burma and Philippines.

Case study 2: The danger of dormant volcanoes in heavily

populated areas

“The most dangerous situation of all is that of a large, unexpected explo-

sive eruption from a long-dormant volcano in a densely populated area.”

Our analysis suggests that 180million people in the Asia-Pacific region

live within 50 kilometres of a volcano that has not been active in at least

the last 40 years; thus this ‘dangerous situation’ is prevalent

in the Asia-Pacific region.

To illustrate the potential impact of one of these long-

dormant volcanoes erupting in the densely populated

Asia-Pacific region we have created a simple simulation

of the impact of Indonesia’s Tambora eruption on today’s

population. The 1815 eruption of the Tambora volcano,

300 kilometres east of Bali, killed around 92,000 people.

With the 20th century population explosion, the impact

of the same eruption today would be catastrophic, as

illustrated by the following scenario.

Assuming that warning signs of an impending eruption

were recognized, and appropriate and timely action taken,

more than 200,000 people would require evacuation from

within 50 kilometres of the volcano. This evacuation would

provide protection from the most life-threatening of the

volcanic hazards. If wind patterns similar to those in 1815

prevailed, around 8 million people would receive at least

20 centimetres of ash during the eruption, potentially

collapsing around one-third of roofs. Roughly one-third of

Indonesia’s population would receive one centimetre of

ash. This relatively thin layer of ash may damage electrical

equipment, disrupt power supplies, contaminate water

sources, cause health problems and significantly interrupt

food production, industry and tourism. Finally, at least one

tsunami was triggered by the 1815 eruption, with a wave

height of four metres observed near the volcano and wave

heights of 1-2 metres in East Java

– such a tsunami today

could cause extensive coastal damage.

A similar eruption scenario could be played out in

many Asia-Pacific countries, with Indonesia and the

Philippines having the greatest populations exposed to

very high volcanic hazard. Our analysis suggests that

volcanic disasters seriously affecting more than 100,000

people can be expected around once a decade in

Indonesia and once every few decades in the Philippines.

Volcanic disasters impacting tens of thousands of people

in Papua New Guinea are expected around once a

century, and Vanuatu has the potential for a catastrophic

volcanic disaster at a rate of around twice a century.

Conclusions

Our preliminary assessment of natural hazard risk in the

Asia-Pacific region highlights the potential for this region

to experience a mega-disaster affecting millions of people

in the coming century. While the scale of such a disaster

may seem greater than what has been experienced histor-

ically, this conclusion is reached not only because the

Asia-Pacific is home to intense geological and meteoro-

logical activity, but also because of the 20th century

population explosion. The population has grown by more

than five-fold during the 20th century, and is increasingly

vulnerable as the result of rapid poorly regulated urban-

ization and the tendency of populations to concentrate

in areas especially prone to natural hazards. Because of

the threat that natural disasters pose to development

progress, natural hazard risk management will continue

to increase in importance in international development

policy in the Asia-Pacific region.