From: Piers Blaikie, Terry Cannon,
IanDavis, and BenWisner
AT RISK:NATURAL HAZARDS, PEOPLE'S VULNERABILITY, AND DISASTERS.
Earthquakes, volcanos and landslides
Earthquakes, volcanic eruptions and landslides, for all their dramatic impact, do not
remotely match the scale of casualties that result from droughts, floods, and coastal
storms (Sapir and Lechat 1986). This century to the end of 1990 there have been an
estimated 1.52 million officially reported deaths from earthquakes. Almost half this total
have occurred in China, which also suffered the most devastating single event in the 1976
Tangshan earthquake which resulted in 242,000 deaths (Coburn and Spence 1992).
The seventeen most severe volcanic eruptions of this
century have resulted in 75,000 deaths, with the most catastrophic eruption occurring in
Mount Pelee in Martinique in 1902 when 29,000 were killed, and the second most severe
event being the eruption of Nevado del Ruiz in Colombia in 1985 with the loss of 23,000
lives. Thus the remaining fifteen volcanic eruptions averaged 1,582 deaths per event (Wood
1986; United Nations 1985).
In the case of landslides, 40 sudden impact landslides have been reported this century
causing 271,072 deaths. However this includes the most damaging landslide of this century,
which took place in Gansu province, China in 1920, when 200,000 were reported killed. In
50 percent of these disasters less than a hundred were killed (Alexander 1989). Thus it
can be seen that in global terms, landslides have relatively low casualty statistics
relative to other hazards. However, the data is misleading, since landslides often occur
as a secondary consequence of another type of hazard, such as flooding, a cyclonic storm,
or as a result of an earthquake. So landslide casualties are often added to the total of
deaths and injuries attributable to these broader events, and those specifically linked to
landslides are probably under-reported.
VULNERABILITY TO EARTHQUAKES
The effects and consequences of earthquakes are varied, but a key issue is the
relationship of earthquakes to unsafe structures (Cuny 1983; Coburn and Spence 1992). From
the evidence of past disasters, it is clear that many countries in seismic areas,
particularly in developing countries, possess many highly dangerous structures that may
collapse under extreme seismic forces (French 1989). In some instances they may be so
dangerous that they can even collapse on their own accord without the assistance of
Over ninety-five percent of all deaths in earthquakes
result from building failures (Alexander 1985). Seaman has commented as follows on the
relationship between mortality and buildings:
Variations in mortality among different countries are
primarily due to differences in building styles and density of settlements. The
overwhelming majority of people who die in earthquakes are killed by the collapse of
man?made structures, particularly domestic dwellings. (Seaman et al. 1984: 10-11).
Seaman then identifies four critical variables:
(a) the seismic and geologic features of an area, the building design and construction,
and specific aspects of building construction and the risks to the occupants; (b) the
location of the inhabitants (e.g. indoors or outdoors); (c) the age and sex of inhabitants
and those killed or injured; (d) the types of injury, severity and timing of presentation
It is possible to add a further item to this list that
relates to the timing of earthquakes. If they occur during the night (as the 1976
Guatemala earthquake), then casualties are always higher for two reasons. Firstly, people
are likely to sleep through the foreshocks which in day?time enable more to escape from
buildings. Secondly, when lying flat in bed the body is highly exposed to injury from
Since buildings are such a critical factors in seismic
risk, concerned officials simply need to look very hard at the elements that relate to
safety with specific consideration of the shape, siting and constructional details of
buildings to find answers to three vital questions. First, where are buildings likely to
fail? Secondly and perhaps even more significantly, what are the root causes of this
dangerous situation? Thirdly, what action can be taken to reduce this underlying pressure?
If the first question is tackled while the second is
ignored, then the lives and property of the population will remain at risk even though
certain individual buildings are made safe, since symptoms (unsafe building design) will
have been addressed rather than the root causes.
Cardona et al (1990: 22) have also examined the issue
of the vulnerability of communities to disasters with a specific focus on their health
status. They suggest that the following ten variables to consider:
Level of Schooling;
Location of the Workplace;
Spatial Distribution of the Population;
Urban Population Density;
Rural Population Density.
To investigate the root causes of vulnerability to earthquakes more carefully, we consider
two widely differing earthquake-related disasters in Central America: Guatemala in 1976
and Mexico City in 1985. Not only were the patterns of vulnerability quite different, but
also the recovery operations were of a very distinct character.
[Figure 8.1 - Distribution of building damage in the 1985 earthquake]
However the site of Tenochtitlan suffered from four natural hazards: volcanic eruptions,
earthquakes, drought and severe flooding. The historic centre of Mexico City now sits on a
lake bed, with an alluvial subsoil up to sixty metres deep. In the 1985 earthquake this
soil behaved like a liquid, with massive ground shaking causing damage almost exclusively
within the area of the original lake bed. This is the tragic legacy of a major city set on
an unstable site which has its roots in the power of Aztec kings and colonial rulers a
full four and a half centuries ago. In Figure 8.2 below, this preconditioning factor is
depicted as a `root cause' of vulnerability.
Second Layer: Buildings at Risk
The next layer of vulnerability concerns the buildings set on this lake?bed subsoil. They
are particularly vulnerable to two types of risk. The first is of ground?shrinkage,
resulting in the subsidence of buildings on the alluvial soils. This is happening because
the water table drops and the clay dries out owing to excessive extraction of water for
the city's needs. This is a form of continual `creeping' or pervasive disaster that caused
extensive damage to property but no direct loss of life. The second more severe type of
risk is that of earthquake impact, likely to cause extensive casualties and damage to
In an assessment of building vulnerability to seismic
risk, a survey has been made of about 20,000 buildings in the historic centre. Seventeen
factors are being considered in the survey, which includes such matters as: levels of
maintenance, the shape of buildings, the `hammer effect' of one building knocking another
during an earthquake, building height, and type of construction (Aysan, Coburn et al.
One major factor that has still to be considered in
mapping seismic risk concerns the age of all reinforced concrete buildings. Those erected
between 1925?42 were built to very high standards of workmanship. Then from 1942?64 the
quality was very poor due to a building boom and a consequent lack of supervision. From
1964 to the present, seismic codes have applied, and the quality of workmanship has
improved (Ambraseys 1988).
However, the detailed analysis of earthquake damage
has revealed that the primary factors that caused damage to buildings related to their
siting and their height. It was found that on sites within the lake bed, rigid structures
(such as stone masonry buildings) generally performed better than flexible ones (such as
reinforced concrete structures).
Height was an even more significant factor in
vulnerability, where medium to high?rise buildings between six and twenty stories were
worst affected, with particularly severe damage to buildings between nine and eleven
stories high. The reasons for this phenomenon relates to the sensitivity of high?rise
buildings, with their lower natural frequencies of vibration than low?rise buildings. They
were prone to resonate with the low frequency seismic energy that emanated from the
epicentre 230 miles away (Degg 1989).
A very serious characteristic of the disaster was the
destruction and damage to public buildings and those with high levels of occupancy
combined with constant use such as hotels and hospitals. Five hospitals collapsed and 22
were seriously damaged which resulted in a 28 per cent loss of public hospital capacity at
the precise time when it was most needed. In the collapse of just six buildings 1,619
people lost their lives (Kreimer and Echeverria 1991).
In addition to the failure of large high?rise buildings there was another group of
buildings that suffered severe damage which was not as well publicised. These were smaller
structures, with high levels of occupancy, with mixed commercial and domestic use.
Analysis of casualty statistics clearly indicates the rather obvious fact that in the
event of an earthquake occurring during day?time, people manage to escape from low?rise
buildings more easily than from high?rise structures (Aysan, Coburn et al. 1989).
When looking at the building damage in Mexico City in
relation to the `pressure and release' model, it is clear that the cause and effect
process is not as straightforward as Guatemala. In the Mexico case, when considering the
damage to high?rise structures, there are no easily identified underlying causes other
than the lack of engineering knowledge. It is possible to see some relationship between
underlying causes and unsafe conditions in the older tenements, where there has been a
failure to maintain severely overcrowded buildings. In some instances there was evidence
of a failure to supervise building construction adequately. Such failures are often
practical or economic as well as an ethical matters.
The question of the level of building maintenance
relates to patterns of ownership and occupation as well as the role of the state in
enforcing maintenance standards. These issues provide a link with the next layer of the
study, that of human vulnerability.
[Figure 8.2 Pressures that result in disasters:
Mexico City 1985]
Third Layer: Society at Risk
Everything discussed in the previous layers are well established areas for the physical
mapping of hazards. The two layers that follow are fields of risk assessment still in
their infancy, and their precise linkage to physical hazards must be defined in specific
In contrast to physical hazard mapping, human
vulnerability analysis covers a bewildering diversity of topics that concern social
patterns and institutions (termed `structures of domination' in the access model),
society-wide and intra-household social relations, and economic activity (gender and age
relations are particularly important as noted earlier), and the psychology of risk.
Given the distribution in time and space of the
earthquake event (hazard) itself and the distribution just described of historically
remote `causes' and unsafe buildings, what specific mechanisms (dynamic translating
processes) were at work in 1985 that placed certain people in those unsafe buildings at
the critical moment? These include the density of population (a function of equitable
location factors as site of employment, land prices, rents); the ownership of buildings
relative to their maintenance; patterns of building use (seen in terms of both space and
time); the perception of risk of the local population; cultural values such as desire to
remain in one's natal neighbourhood; and the existence of local institutions that could
play a key role in post?disaster recovery.
Mention of the last `mechanism' that translates `cause' into vulnerability reminds us that
disasters relate to the long-term consequences for survivors as well as the immediate
impact. This was clear in the discussion of recovery between cyclones in Andhra Pradesh
(Chapter Seven). In the context of the Mexico City earthquake, critical questions about
recovery would have to cover such economic matters as the capacity of people working in
the high risk zone to regain their livelihoods at their pre?disaster condition following
another earthquake. Much of this data is concerned with potential economic losses which
are considered as a final layer of vulnerability.
Fourth Layer: The Local Economy at Risk
Effective disaster planning has to consider the likely effects on the local economy of
earthquake losses. This data, which did not exist before the Mexico City earthquake, can
be measured in three ways. Firstly there are direct losses (e.g. of a building or factory
in a future disaster); or secondary losses (e.g. fire damage ignited by the earthquake);
or through indirect losses (e.g. the loss of income as a result of the local population
not being able to purchase goods due to their temporary loss of income, or because of
interruptions to supplies).
The `layers' of Mexico City's vulnerability to earthquakes provides a convenient `access
model' for the examination of earthquake hazards. The disaster did not occur in a vacuum,
its impact was suffered within a `space?time' context that affected a particular section
of the city's building stock and population occupying specific structures at a specific
The effect of the earthquake can be considered in two
ways: the destruction of property and the impact on lives. In the Mexico City earthquake,
two distinct categories of buildings collapsed or were damaged; both were both constructed
on alluvial soils that formed the bed of a long-vanished lake. The first category involved
people who died or were injured in high?rise buildings, including a hotel and a number of
hospitals. These casualties came from all levels of Mexican society. In contrast, the
second group were the predominately low?income residents of 19th century low?rise
tenements. As we pointed out in Part I, we are concerned to define and to underscore the
relevance and practicability of vulnerability analysis by pointing out how it is
applicable beyond simple criteria such as income and status. The losses in the first
category included some victims who would not be considered vulnerable in terms of their
income. However, vulnerability is closely parallel to low-income status of residents of
The earthquake occurred at 7.00 hours on 17th
September 1985 when most people were on their way to work. For those on foot, the hazard
was falling masonry crashing onto pavements, but for the thousands inside metro trains, or
motor vehicles the immediate environment was highly protected.
The vast majority of those who died were inside medium
to high rise buildings, in the central area of the city. Some 12,700 buildings were
affected, 65 per cent of which were residential. The housing for 180,000 people was
damaged, and 50,000 needed temporary accommodation (Kreimer and Echeverria 1991). Since
the damage affected high-investment buildings, the financial losses were enormous,
estimated at $4,000 million (Kreimer and Echeverria 1991). The re?insurance industry has
assessed the earthquake as one of the three most disastrous of this century, the others
being the San Francisco and Tokyo earthquakes of 1906 and 1923 respectively
Such financial loss dwarfs the dollar value of
dislocated livelihoods. Yet for those who relied on work in the 1,200 small industrial
workshops destroyed, the cost was great. Once more it is clear that issues of recovery and
rehabilitation cannot be separated from the profile of vulnerability. Are those workers
still unemployed, or found an alternative? Did the earthquake begin a spiral into poverty
for those households?
The number of casualties varies in spatial terms,
since it relates to the horizontal location of victims (i.e. in a building set on the
alluvial soils), or vertically (at a certain height in a building). The timing of the
earthquake was even more critical in determining the number who die or are injured. Had an
earthquake with identical characteristics and intensity occurred just three hours earlier,
when people were asleep, there would have been a significant increase in casualties,
although property losses would not have changed.
[Figure 8.3 Release of Pressures to Reduce Disasters:
...recovery of Mexico City...]
Figure 8.3 is an attempt to identify the factors which could be adopted by the Mexican
authorities to release the pressures that have in the past created unsafe conditions in
Mexico City. (Coburn and Spence 1992: 130; Gomez 1991: 56-57, Echeverria 1991: 60-61). The
model addresses vulnerability indirectly and directly. Indirect measures include reducing
the size of Mexico City. Urbanisation is addressed by improving rural economic
opportunities, lessening the migration to the city, and by decentralising some of the
federal government's functions (hence employment opportunities) to other cities in Mexico.
In this way one of the most important dynamic pressures that translates global root causes
into unsafe conditions is relieved.
In addition, unsafe conditions are addressed directly
by improved aseismic building codes and their enforcement, strengthening existing
structures, and reducing the densities in certain weaker structures by changing patterns
of use. These steps, none of them unthinkable in contemporary Mexico, although some more
difficult politically and more expensive than others, complement a programme of improved
disaster preparedness planning. But already, less than ten years after this major
disaster, there is a decline in `political will' to protect the city from such disaster
impact. Seismic risks have been displaced by other more pressing political and
End of Box 8.2
Vulnerability To Hazard Warnings
Before leaving the subject of earthquakes, it is important to consider the issue of
prediction. Is this a developing science that will greatly reduce casualty patterns, as is
already beginning to happen in the case of cyclone deaths, or is it a false trail that may
be a contributor to new forms of vulnerability? The predictive processes available for
some other hazards are not yet sufficiently developed to forecast earthquakes. However,
there has been excellent progress in the monitoring of landslides and volcanic risks. Hong
Kong has sophisticated computer models are already in routine operation to monitor
rainfall levels and predict when a given slope is likely to collapse. Using the technique
the authorities have made a number of successful evacuations that have preceded major
landslides (Whitcomb 1990). Several successful evacuations of vulnerable communities have
taken place in recent years as a result of effective warnings of impending volcanic
eruptions (United Nations 1985). Examples of such successes include the eruptions of Mount
Pinatubo in the Philippines, Etna in Italy, and Mount St. Helens in the U.S.
The evacuation that preceded the main eruption of
Pinatubo was a result of timely action by the authorities and the pressure of events.
Pinatubo was regarded as extinct, so there was understandably minimal planning for a
possible eruption (International Federation of Red Cross, 1993: 62; Office of Foreign
Disaster Assistance 1992; Newhall 1993; Baxter 1993; Tayag, n.d.). Volcanic activity began
on 2 April 1991, and the residents on the mountain slopes within the likely affected area
were encouraged to evacuate with an incentive offer of relief supplies in the emergency
evacuation centres. Initially the response was slow, with about 25,000 leaving their
homes, but this changed after 9 June when the first major eruption occurred. The
government and the Philippine National Red Cross created 276 evacuation centres that
ultimately housed 130,944 people. On 15 June the area suffered a second disaster as a
typhoon devastated the region.
There is no doubt that the volcanologists gave wise
advice to the National Disaster Co-ordinating Council (NDCC) who ordered the evacuation,
but it was probably the further eruptions that persuaded most people to evacuate. As a
result casualties of 321 deaths and 275 injured were very low (these figures include
casualties from subsequent mudslides). However there were also serious negative effects of
the evacuation that should be considered. Many sick people and elderly died in the
evacuation areas. Communal living in camp conditions, with cyclonic rainfall to compound
volcanic ashfalls, was a very unhealthy living environment (Newhall 1993; Baxter 1993).
This problem was probably unavoidable then, though more attention needs to be given to
Hazard mapping will reveal the location and probable
severity of earthquakes and landslides. Long-term predictions, based on a `gap-theory'
about the anticipated general location of a forthcoming earthquake may also be useful. But
the current state of knowledge gives no precise warning of their timing. It would appear
that this lack of earthquake warning is a significant factor in maintaining the
vulnerability of people.
Early warning of drought, cyclone and flood is already
reducing the vulnerability of communities previously at risk and significantly reducing
deaths and injuries. But an earthquake prediction can result in other problems, such as
panic in evacuation, or the more mundane issue of blighted property and falling values in
areas thought to be targets. The risk of legal action over such issues can actually make
prediction politically unacceptable. In 1986, following small tremors, the population of
56,000 in the towns of Lucca and Modena in Tuscany (Italy) were evacuated. 13,000 hospital
beds were made available, and railway carriages brought in to accommodate the evacuees.
Widespread traffic jams and petrol shortages followed, and shops and businesses closed for
two days. However no earthquake occurred and recriminations from angry businessmen
eventually caused the resignation of the Mayor and Administration (Coburn and Spence,
Many commentators have suggested that a total
evacuation from a major city would constitute a disaster in its own right, perhaps of far
greater impact that any impending earthquake. They have surmised that there would be
traffic problems and accidents on a herculean scale (particularly if there was widespread
panic), crime and looting, economic losses beyond belief and the acute difficulty in
maintaining public services for the metropolitan region and perhaps for an entire nation.
Additionally there would be public health risks to the displaced population, depending
where, how, and for what duration they were accommodated. These would include epidemics
due to inadequate sanitation, psychiatric stress of uncertainty, anxiety and possible
separation from loved ones. These issues will probably weigh most heavily with governments
facing political instability.
While governments may tremble at the prospect of a
major evacuation, the prospects are even more devastating when seen at the `micro level'
of poor families with very limited resources. Wisner (1985: 16) describes how they are
... hurt when they have to miss a few days or weeks of
work, often the price of temporary relocation or evacuation. These people are not
`stupid'. The mental arithmetic itself is cruel: evacuation on a `false alarm' could make
the difference between life on the poverty line with some hope and years of absolute
poverty below it, because of property theft by looters, loss of work, or damage to the
Such critique of evacuation options may be regarded as
decidedly `doom-laden', but there is mounting evidence of the problems that mass
evacuations pose for authorities. An epic example was the management of several million
Kurdish refugees from Iraq in the spring of 1991 or speculation by the authorities of what
would happen if the entire length of Miami Beach Island had to be evacuated in the event
of a major impending hurricane.
Tremendous social and economic problems have resulted
when entire regions have been evacuated due to volcanic risk. A classic case is in the
Caribbean island of Guadeloupe in the Lesser Antilles, where 73,000 people were evacuated
in 1976 from the high-risk zone for three and a half months, resulting in huge economic
losses and great social strain on the population and their government. The volcano never
erupted and there was only minor volcanic activity (Blong 1984).
Landslides involve the movement of material that may vary considerably in its character,
including rock, debris, mud, soil, or several of these in combination (Alexander 1989:
157). Alexander includes landslides that are generated by a wide variety of `agents': the
failure of coal-mining waste in Wales (Aberfan); a dam burst in Italy (Vajont); a volcanic
eruption in Colombia (Nevado del Ruiz); an earthquake in Peru (Mt. Huascaran) and flooding
in Brazil (Rio de Janeiro).
Applying vulnerability analysis to the case of
landslides, we need to move beyond the physical hazard to inquire about human activities
that might act as `triggers' for the physical event (e.g. location of a dam) as well as
the sort of `mechanism' that translate exposure to the risk differently for various
categories of people. Differential ability to recover after a landslide is also important
since it can cause people to be more exposed to future risks, as we have seen in previous
Consider four typical examples of landslides that took
place between 1985 and 1988:
(a) Mameyes, near to Ponce in Puerto Rica, 8 October 1985, killing 180, 260 homes
destroyed (Wisner 1985; Doerner 1985);
(b) Rio de Janeiro, Brazil, February 1988, where 277 were killed, 735 injured and more
than 22,000 displaced in shanty towns (Allen 1994; Byrne 1988; Margolis 1988; Michaels
1988; Munasinghe 1991: 28-31);
(c) Catak, Turkey, on June 23 1988, killing approximately 75 (Gurdilek 1988);
(d) Hat Yai, Thailand in November 1988, killing 400 (The Economist 1989; Nuguid 1990; and
The analysis of the likely causes (or `general
predisposing factors' in terms of the PAR model) of these landslides shows a number of
The first commonly-cited cause is deforestation. There
was an outcry against logging in Thailand following the landslides. West (1989: 18) notes
that this protest did not come from bearded ecologists and trendy `green' politicians, but
from the local farmers and townspeople, those in fact, who had suffered. The anger comes
from below, and is aimed especially at the greedy loggers, frequently Chinese businessmen
in partnership with senior officials in the police and army.
The Prime Minister of Thailand visited the site of the
disaster and announced that logging operations would be banned. Forty years ago, 70
percent of the country was covered by forests, but in 1989 this percentage had dropped to
just twelve percent (The Economist 1989).
In Rio, the authorities were criticised for not taking
effective action to tackle the problems of the denuded hills where all the favelas
(squatter settlements) had been constructed. These housed a million people out of the
eight million in the city. There had been extensive deforestation in these areas to make
way for dwellings as well as providing fuel-wood. Socio-economic factors are an obvious
`pressure' that both forces squatters to inhabit unsafe locations and forces them to cut
vegetation for fuel or building material since alternatives are too expensive (Allen
Poorly located road building is also commonly
mentioned as a cause. Turkish authorities commented that the roads in Catak should have
been cut into the contours, rather than running parallel with them. Frequently, roads are
cut into steep slopes with minimal understanding of the geomorphology of the setting, and
can interrupt drainage patterns. The actual `cut and fill technique' of road building on
steep slopes can contribute to landslide risk (Smith 1992: 165).
Environmental damage to sub-soil stability is also
frequently cited as a cause. Changes in the water table can occur due to leaking tube
wells, stand pipes and septic tanks, and appear to have been a contributory cause to the
landslides in Puerto Rico and Rio de Janeiro. Unsafe, unauthorised building on
dangerously-steep slopes is very often cited as a cause of landslide disasters. The
location of squatter settlements themselves may have been a contributory cause to the
landslides in Puerto Rica and in Rio de Janeiro.
Warning systems for predicting water flow and
arranging the evacuation of communities at risk are often lacking in urban areas. This
appears to have contributed to the landslide disasters in Puerto Rica and Rio de Janeiro.
There had been extensive rain for a number of days prior to the mudslides, but no
monitoring or advance planning for such contingencies.
VOLCANOS AND RELATED HAZARDS
Volcanos are vents in the crust of the earth through which molten rock is extruded as lava
or ejected as ash or coarser debris, sometimes accompanied be steam, hot and often
poisonous gases (Davis and Gupta 1991: 29). Associated hazards include earthquakes, and
mud and rock slides. Volcanos are like some epidemics (discussed in Chapter Five) in that
they represent a limit to the use of vulnerability analysis. Volcanic eruptions endanger
any person living within the high-risk zone whether rich or poor, landowner or landless
farm labourer, man or woman, old or young, member of ethnic minority or majority. Tomblin
Eruptions differ from most other major causes of
disaster such as earthquakes, hurricanes and floods, in that they cause virtually total
destruction of life and property within relatively small areas which can be easily
delineated. (Tomblin 1987: 17).
Poisonous gas emissions do not differentiate between
social groups. But even where these are not the main threat, income levels, the quality of
house construction and the type of occupation all seem to have little bearing on people's
differential capacity to resist the volcanic arsenal of hot gas emissions, blast impact,
lava flows, projectiles, volcanic mud-slides (lahars), and the deposit of ash.
It may be argued that wealthy people have more access
to knowledge, which can include an awareness of volcanic risk, and therefore they are
better able to respond to warnings to evacuate in the event of a likely eruption. But
there is growing evidence that poor people living near active volcanos are aware of the
risks. Once they observe signs of volcanic activity they are just are as likely to follow
evacuation orders as their rich neighbours (Kuester and Forsyth 1985; Tayag n.d.; Zarco
1985). This was apparent in the Pinatubo evacuation described below.
The term `hazard' is not strictly accurate since in many cases they bring major benefits
as well as havoc: irrigation and fertile silt from flooding, or the rainfall over
drought-prone land from tropical cyclones. This process is probably better seen in the
case of volcanos than any other geological hazard, since there are no obvious benefits
from landslides and earthquakes.
The products of volcanos can be highly beneficial to
any society, and include extremely fertile soils resulting from the weathering of volcanic
ashes and pyroclastic materials. Farmers often obtain bumper harvests as a result of a
mild sprinkling of volcanic ash on their fields (Wood 1986: 130). In April 1992 Cerro
Negro erupted near Leon in Nicaragua. A thick layer of volcanic ash was deposited, with
gloomy forecasts that the agricultural economy would be interrupted for years. However,
within ten months farmers were already enjoying good crops from the fertile soils
intermingled with volcanic ash (Baxter 1993).
Such volcanic blessings undoubtedly constitute an
extremely powerful social and economic magnet. It is often suggested that people
inhabiting high risk zones are gamblers by nature, who take big risks to achieve uncertain
benefits. But the odds are very uneven since it would not appear to take families very
long to decide to face the risk of an eruption with a return period of perhaps 45 years
for the pay-off is significantly enhanced economic opportunities that will apply every
day. Paradoxically, effective disaster preparedness with its expectations of good warning
and evacuation by the authorities only adds to the power of the magnet drawing people into
high risk zones.
Case Study: Pre-Disaster Planning, Taal Volcano, The Philippines
An example of these conflicting demands of prosperity versus safety and how they relate to
public policy can be seen in a case study of Taal volcano in the Philippines. This is one
of the world's lowest and deadliest volcanos, on an island in lake Taal, about 60 km south
of Manila. Taal has had 33 recorded eruptions since its earliest recorded outburst of
1572. The 1911 eruption resulted in 1,334 deaths and covered an area of 2000 sq. km with
ash and volcanic debris which fell as far away as Manila. Further volcanic activity
occurred in 1965, 1966, 1967, 1968, 1970, 1976 and 1977 (Arante and Daag, n.d.;
Philippines Institute of Volcanology and Seismology [undated b]).
The main eruption of 1965 was completely unexpected, with no official warning being
issued. Chaos ensued, as Arante and Daag describe:
... panic gripped the beleaguered inhabitants as they
scrambled for the few available boats. Many died while fleeing the island as boats
capsized due to the combined effects of overloading, falling ejectamenta, (ash, and
volcanic rock projectiles) and base surge (a lateral explosion of hot gasses that travels
at hurricane speed).
The present population of the island is 3,628 people
in about 600 households. They enjoy a relatively prosperous economy based on fishing, fish
farming, agriculture, mining for scoria and using their boats to bring tourists to the
island. The location of settlements on the island closely relates to particularly rich
fertile soils suitable for sweet potato and corn. Perhaps as a direct result of the
island's attractions, the population is currently growing at the rate of 9.6 per cent per
year, more than three times the national average. However the the island only has 215
boats which can accommodate 1,900 people. Thus in the event of a very sudden eruption with
minimal warning time, only about half of the population would be able to escape.
Any future eruption similar in intensity to that of
1911 or 1965 would also affect ten settlements that surround the lake with a combined
population of 76,000 (See Figure 8.4). During a Disaster Management Training Workshop in
1988 arranged by the Government of The Philippines, participants visited the island to
discuss vulnerability and safety with the residents and with local public officials from
the government who lived on the mainland.
[Figure 8.4 - Hazard risk map of Taal volcano Philippines]
The group found that there was very little anxiety on the part of the population over the
risks they faced, even amongst those who had survived the 1965 eruption. The lack of
escape boats was also of minimal concern, since residents referred to the building that
had been set up on the island by the Philippine Institute of Volcanology, and they clearly
thought that this was some form of `volcanic eruption insurance policy', assuming that
this agency would be able to look after them in the event of a disaster. They also felt
that the very presence of this warning station proved that it was actually safe for them
to live on the island. It is doubtful if the symbolic effect of the structure on the local
community entered into official thinking when it was conceived.
Community leaders who were interviewed were much more
concerned at the failure of the government to build medical facilities or a school on the
island, which resulted in their children having no education or travelling each week to
the mainland where they lived with relatives during the week while attending local
Government officials responded to the criticism by
stating that the island was a designated centre of special scientific and environmental
importance. People were not allowed to live on the island on account of the severe
volcanic dangers. Therefore, land-use planning controls required the government not to
spent any public money on such facilities as schools and dispensaries. Provision of such
services would only result in more people coming to live on the island, with a consequent
expansion in risk.
The workshop participants, mainly government
employees, then responded forcefully that since the residents of Taal island paid taxes to
the government, their acceptance by the government was a tacit admission that the
settlement was legal. Consequently in their view, the government was obliged to provide
basic services to the community. They went further and suggested that these services
should include disaster preparedness for the island community which should comprise
additional emergency evacuation boats (DSWD n.d.).
The Taal example supports the view that vulnerability
to volcanos is not confined to poor households, or those who in some other way are
marginal. In fact, the Development Academy of the Philippines is situated on the
spectacular Tagaytay Ridge overlooking Taal Lake, near some expensive houses owned by
wealthy Filippino families. Nearby is also a summer palace that President Marcos
half-built before his fall from power. This property, including the Development Academy
for the training of senior civil-servants is adjacent to the Taal `High Risk' zone. The
records indicate that many people died in precisely this area during the 1911 eruption.
On the other hand, many people in the Taal area have
good memories of the Mayon eruption of 1984, when there were enormous economic losses but
no casualties in the affected area (which had a population of 90,000) due to a very
effective evacuation of 73,400 people (Tayag n.d.; Zarco 1985).
The farmers and Marcos took a broad (and private)
view, in which Taal volcano was just one of many ingredients (or perceived risks) that
influenced their decision on where to build a house. In contrast, the volcanologists, who
sought to ban the occupation of an island, took a narrow (and public) view of risk and
vulnerability that was confined to the values of their professional background linked with
the values of officialdom, and failed to acknowledge the island full of useful resources.
Each group represents an entirely legitimate and logical response to the same hazard, yet
their views vary because their respective needs, priorities, perceptions, and values are
very different from each other.
BOX 8.3 ENDS
Case Study: Post-Disaster Response following the Nevado del Ruiz Volcanic Eruption, 13
November 1985, Colombia
A second example concerns the effects of an eruption of Nevado del Ruiz, on the town of
Armero in Colombia on 13 November 1985. Unlike Taal this volcano was relatively inactive
since its last eruption in 1845.
The eruption occurred at 3.15 p.m. and two hours later the residents of the town of Armero
(population 29,000) noticed that fine dust was falling. At 5.30 p.m., the National Geology
and Mining Institute is reported to have advised that the entire area at risk should be
evacuated. By 7.30 p.m. the Red Cross attempted to carry out such an evacuation, but
perhaps on account of very heavy rainfall from a thunderstorm or the lack of previous
evacuation drills, few agreed to leave their homes. At 9.05 p.m. a strong tremor occurred
on the volcano which was followed by a rain of hot pumice and ash. As a result, part of
the ice cap of the 5,400 meter volcano melted and caused the river Guali to overflow. This
in turn caused a natural dam to burst, releasing a torrent that travelled at speeds of
about 70 kms per hour, and a massive mudflow to envelop the town of Armero (United Nations
1985; Siegel 1990).
Within the town one of the few survivors, Rosa Maria Henoa, described how at about 11.35
[f]irst there were earth tremors, the air suddenly smelt of sulphur, then there was a
horrible rumbling that seemed to come from deep inside the earth. Then the avalanche
rolled into town with a moaning sound like some kind of monster ... [H]ouses below us
started cracking under the advance of the river of mud.' (Quoted in UNDRO 1985: 5).
What transpired in those minutes is a horrific story
of people attempting to drive away from the wall of roasting mud, stones and water. Some
died in the chaos as terrified people tried to climb aboard the moving vehicles (Sigurdson
and Carey 1986; Davis 1988; Parker 1989; Siegel and Witham 1991).
In the early months of 1988 a group of lawyers inserted a notice in the local press of the
city of Manizales, and in the small towns of Guayabal and Lerida. These are close to
Armero, and housed some of the three thousand survivors. There was little point in pinning
any notices in Armero since the town had become a vast deserted `cemetery' where as many
as 22,000 people are buried. The lawyers invited anyone who had suffered injury, the loss
of relatives or property in these volcanic mudslides to contact them if they wanted to sue
the government of Colombia for gross negligence in not warning or evacuating them in time
to avoid injury or property losses.
In response to these advertisements no fewer than 750 claims were filed amounting to a
total claim of 20,000 million Colombian pesos (approximately £40 million sterling). The
claim against the government hinges on their alleged negligence in failing to develop
effective preparedness planning (including evacuation procedures) to enable the population
to escape falling debris and mud?slides. These are known hazards that have occurred after
previous volcanic eruptions in the region.
It was anticipated that the government lawyers would argue that the residents were aware
of the risks in choosing to occupy a hazardous, yet like Taal island a highly fertile
area. By the time the case reached the court in Tolima, the number of claimants had risen
to about a thousand. They sued the Ministry of Mines and Energy of the Colombian
Government, since the geological service, with scientific responsibility for the issuing
of volcanic warnings was attached to this ministry. The claimants alleged that the
Government had failed to protect its citizens by not enforcing an evacuation of the
citizens of Armero and other affected villages.
The government lawyers argued that the `ordering of evacuations' was not one of the
designated functions of the Ministry of Mines and Energy. But, as proof of governmental
concern they produced evidence that Civil Defence had conducted a `door to door' campaign
to warn people to evacuate during the early stages of the eruption. Three expert
volcanologists were questioned as to whether the scale, location and timing of the
mud-flow could have been accurately forecast. They gave a negative answer, and on this
basis the government was cleared of responsibility (Wilches-Chaux 1992b).
The Nevada del Ruiz disaster was a catalyst that had a dramatic impact on the development
of disaster protection in Colombia. An effective Governmental Preparedness System at
central and provincial level was created, which includes detailed warning and evacuation
systems. However, whilst preparedness-planning exists on paper, maintained by governmental
legislation, economic priorities can easily dominate safety considerations in practice.
For example, the Galeras Volcano erupted in January 1993. The nearby town of Pasto is at
risk of major eruption from this very active volcano. In 1992 and 1993 the government
Disaster Preparedness Agency wanted to issue warnings to the public, but the local
authorities have refused to authorise them. Their refusal stems from the economic
consequences of an earlier warning several years ago, which provoked an immediate
financial crisis in the locality when credits and loans were closed (Wilches-Chaux 1993).
BOX 8.4 ENDS
POLICY RESPONSE AND MITIGATION
In concluding this chapter on a positive note, four approaches to risk reduction in the
face of geological hazards are suggested (we go into these in more detail in Chapter Ten).
First, earthquake, landslide and volcanic disasters can be used to change unjust
structures. Popular development organizations can capitalise on a disaster event to
challenge and possibly change vulnerable, unjust political, social and economic
structures. Holloway (1989: 220) has suggested that [d]isasters will often set up a
dynamic in which social structures can be overturned, and relief and rehabilitation
judiciously applied can help change the status quo; while projects will be the models in
microcosm that can be used to demonstrate to government the possibilities of a variety of
ways of working.
Thus in the aftermath of the Mexico City earthquake, neighbourhood organizations were
strengthened and increased their demands for government services (Robinson et al. 1985;
Annis 1988). There is not a direct relationship between the strength of local
organisations and reduction of vulnerability to disaster, but certainly the converse is
true: in the absence of grassroots and neighbourhood organisation, vulnerability
Second, and following from the first, local institutions can be strengthened and the
capability of families to reduce their own vulnerability can be improved. This is Anderson
and Woodrow's notion of `rising from the ashes' (1989). However, to achieve this end
energy and resources need to be focused on strengthening the self-reliance of the most
vulnerable households and their local institutions. We return to the difficult question of
identifying and aiding `the most vulnerable' in Chapter Nine.
Dudley assisted local Ecuadorian artisan builders to rebuild their homes in a safe manner
after the earthquake of March 1987. He reflected on the experience:
We have learnt that with outside support, but not external control, and with limited
technical objectives the people can achieve great things ... [T]rue development, disaster
or no disaster, will only take place through the strengthening of indigenous
infrastructures directly accountable to local people. (Dudley 1988: 120).
Accountability builds trust, and trust allows access to the inner workings of local coping
mechanisms. When these are translated into architectural form, there is the possibility of
designing low-cost, safer shelter together with local people as partners (Maskrey 1989;
Aysan and Davis 1992).
Dudley then reinforced the outlook emphasised in this chapter that disaster risk reduction
... is just as much a product of socio-economic factors as technical ones. The best hope
for a community's recovery in a disaster is to have a history of strong organization; it
is to this end that local institutions must direct their efforts. (Dudley 1988: 121).
Maskrey (1989) has compiled many such cases where appropriate technology and localized
institution building have reduced future vulnerability to geological hazards, especially
earthquakes in Latin America.
Third, the disaster provides an opportunity to develop effective risk assessment with good
cost-benefit arguments for protective measures. An example is encouragement offered to
local authorities by a World Bank team that has been working in La Paz, the capital city
of Bolivia, which faces numerous hazards. In a report on the lessons they had gathered
from the project the team concluded that risks could be evaluated, quantified, programmed
and addressed with measures that were affordable to the city, even with all its pressing
demands on the budget:
[W]e calculated that disaster prevention and preparedness would cost US $500,000 in 1987
and total about US $2.5 million, or US $2.50 per capita ... [T]his amount is far exceeded
by annual losses from natural disasters estimated at $8 per capita. With this minimal
level of funding, disaster mitigation could be affordable, cost-effective and within the
realm of La Paz's needs (Plessis-Fraissard 1989: 135).
Finally, disasters provide an opportunity to educate political leaders and decision makers
about the true nature of vulnerability to disaster risk. Authorities may be ignorant, or
they may deliberately avoid recognising their own role in increasing risks. However, they
may respond to messages such as that of the financial calculation noted above, that action
in developing protective measures will be to their benefit later. Quarantelli has
emphasized the vulnerability component in disasters and, a fortiori, the potential impact
of often reasonably low-cost policy initiatives. He notes that
[a]llowing high density population concentrations in flood plains, having poor or
unenforced earthquake building codes for structures, delaying evacuation from volcanic
slopes, providing inadequate warnings about tsunamis, for example, are far more important
than the disaster agent itself in creating the casualties, property and economic losses,
psychological stresses, and disruptions of everyday routines that are the essence of
disasters. (Quarantelli 1990: 18).
In particular, the impact of earthquakes, landslides and volcanic eruptions will only be
reduced when decision-makers become more aware that there can never be a natural disaster;
at most, there is a conjuncture of certain physical happenings and certain social
happenings (Quarantelli 1990: 18).
To conclude, the four verbs that introduced these final suggestions imply the opposite of
any passive acceptance of the inevitability of geological disaster losses: to `change', to
`strengthen', to `develop' and to `educate'.
Notes to Chapter Eight
By kind permission of Routledge
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