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Asian Development Bank

Chapter 1.2 Introduction

Disasters explained

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Disasters result from a combination of factors: the nature of the particular hazard or hazards; the extent to which people and their possessions are exposed to them; the vulnerability of those people and assets; and their capacity to reduce or cope with the potential harm. Many different kinds of hazard can contribute to disasters. These may be natural (e.g. floods, earthquakes, landslides, windstorms), technological (e.g. industrial and transportation accidents) or otherwise created by humans (e.g. riots, terrorist incidents and conflict). They can act in combination, as well as individually: the 2011 tsunami in Japan, for instance, led to a crisis in a nuclear power plant,+For the Japan event, see F. Ranghieri and M. Ishiwatari (eds), Learning from Megadisasters: Lessons from the Great East Japan Earthquake (Washington DC: World Bank, 2014), while earthquakes and intense rainfall can both trigger landslides. Other threats facing human development include economic shocks, the effects of inequality, health risks and food insecurity.

Disasters take place in time as well as in space. They can be short- or long-term in their duration. They can be sudden events (or shocks), such as disease outbreaks, storms, earthquakes and conflict, but they can also arise from the accumulation of stresses, such as long-running drought, the degradation of natural resources, unplanned urbanisation, climate change, political instability and economic decline.

Disasters are generally seen as extreme events in their scale or impact, requiring some form of external assistance. However, small-scale, lower-intensity hazard events can also have significant impacts locally. These small, recurrent events are usually referred to as ‘extensive risks’. Poor people also often face high levels of everyday risk, for example from lack of clean water and sanitation, poor healthcare, pollution, occupational injuries, road accidents, domestic fires, violence and crime.

Vulnerability to hazards determines the impact of the disaster

Vulnerability to hazards determines the impact of the disaster. Video:

This book focuses on disasters in which natural hazards play a part, although it also addresses the interaction between such disasters and social crises and conflicts (see Chapter 15: DRR, social crisis and conflict), and the relationship between disaster impacts and prevailing social and economic conditions. The phrase ‘natural disaster’, which is commonly used, is misleading and often causes confusion. Strictly speaking, there is no such thing as a natural disaster: there are only natural hazards. The difference between a hazard and a disaster is an important one. A disaster takes place when a society or community is affected by a hazard (a disaster usually defined as an event that overwhelms society’s capacity to cope – see Box 1.1: Disaster terminology). In other words, the impact of the disaster is heavily influenced by the community’s vulnerability to the hazard. This vulnerability is not natural: it is the human dimension of disasters.

Box 1.1 Disaster terminology

The literature on hazards, vulnerability and disasters is full of technical terms. This book tries to sidestep the technical jargon as far as possible because many people working in aid and development find it off-putting (a related problem is that use of the emotive word ‘disaster’ automatically conjures up images of emergency relief and often leads to disaster reduction work being viewed solely as an aspect of humanitarian aid when it should also be a central component of development programmes). Nevertheless, certain terms are used regularly in writing and discussion about DRR. These can be defined and understood in slightly different ways and there has been considerable debate about their precise meanings. They are also often used quite loosely or flexibly by practitioners, which can cause confusion or even lead to disputes. Table 1.1 sets out some of the key terms as defined by two international and reputable bodies: the UN Office for Disaster Risk Reduction (UNISDR) and the Intergovernmental Panel on Climate Change’s Special Report on Extreme Events and Disasters. Everyone using DRR terminology should be clear about their own understanding of it, and communicate this to others with whom they work.

Vulnerability is the result of the whole range of economic, social, cultural, institutional and political factors that shape people’s lives and create the environments that they live and work in. Development processes play a key role in exposing people to hazards, as well as shaping their vulnerability to potential disasters. For example, the fact that large numbers of people live in flimsy houses in hazardous locations could result from a combination of several factors: poverty (itself a symptom of local, national and even global economic forces), population growth, displacement due to economic development (e.g. loss of smallholdings to commercial agriculture), migration to towns and cities (which has a variety of socio-economic causes, including livelihood opportunities), legal and political issues, such as lack of land rights, government macro-economic and other policies and other political features, including weak government and civil society institutions.

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The more vulnerable someone is to a hazard, the greater the impact will be. Video:

Extensive research all over the world has shown that in general it is the weaker groups in society that suffer worst from disasters, principally the poor, the very young and the very old, women, the disabled, migrants and displaced people and people marginalised by race, caste or other socio-economic or cultural characteristics (see Chapter 5: Inclusion). Those who are already at an economic or social disadvantage because of one or more of these characteristics tend to be more likely to suffer during disasters. Vulnerability is not just about poverty, but poverty is a fundamental factor. Disasters’ impact on society is uneven and unequal: poor and socially marginalised households tend to be much more vulnerable to losses than wealthier households; they are pushed deeper into poverty as a result; and they find it more difficult to recover.

This issue of vulnerabilities linked to socio-economic context (in particular inequalities in society) is very important in understanding the impact of disasters and making choices about how and where to intervene. Vulnerability is highly dynamic, changing in response to many different influences, yet most vulnerabilities remain persistent because they result from deep-rooted social marginalisation, the indifference or incapacity of political and official institutions and the inadequacy of public services.

Figure 1.1 The disaster risk–poverty nexus

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2009 Global Assessment Report on Disaster Risk Reduction: Risk and Poverty in a Changing Climate (Geneva: UNISDR, 2009),, p. 8.

Disasters affect rich as well as poor countries (see Case Study 1.1: Central European floods, 2013), but they have a particularly severe impact on low-income countries, which experience disproportionately higher mortality and suffer higher levels of economic loss in relation to the size of their GDP. Disaster events can sometimes set back years of economic and social development gains, generate political instability and cause long-lasting environmental damage. Like poor families, low-income countries often lack the resources and capacities to cope with disasters (see Table 1.2: DRR capacities in richer and poorer countries).

Case Study 1.1 Central European floods, 2013

Germany, Austria, Hungary and the Czech Republic were badly affected by flooding in June 2013. Flood protection and water storage structures, such as levees, water diversion channels, dams and lakes and restored floodplains (many of which had been created following devastating floods in Central Europe in 2002), generally proved effective in preventing flooding, especially in major towns and cities, but in some places they were overwhelmed by the exceptionally high water levels, or there were gaps in the defences that allowed floodwater through. Although the death toll was relatively low (25 people were killed), estimates of economic losses ranged from €11.9bn ($16.5bn) to €16bn ($22bn). In Germany alone, an estimated 52,500 people along the Danube and Elbe rivers were forced to leave their homes.

Zurich Insurance, Central European Floods 2013: A Retrospective (Zurich: Zurich Insurance Company, 2014),


Box 1.2 DRR capacities in richer and poorer countries

Richer countries Poorer countries
Have regulatory frameworks to minimise disaster risk which are enforced Regulatory frameworks are weak or absent, and/or the capacity to enforce them is lacking
Have effective early warning and information mechanisms in place to minimise loss of life Lack comprehensive information systems linked to pre-emptive response
Have highly developed emergency response and medical care systems Divert funds from development programmes to emergency assistance and recovery
Insurance schemes spread the burden of property losses Those affected bear the full burden of property losses and may lose livelihoods
P. White et al., Disaster Risk Reduction: A Development Concern (London: Department for International Development, 2004),, p. 9.

The multiple pressures and factors that combine to create and increase vulnerability can be tracked to identify a ‘progression’ of vulnerability (see Figure 1.2: The progression of vulnerability). These pressures can be released by taking measures to reduce vulnerability right along the causal chain – an indication of the wide range of interventions that are possible.

Figure 1.2 The progression of vulnerability

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B. Wisner et al., At Risk: Natural Hazards, People’s Vulnerability and Disasters (London: Routledge, 2004), p. 51.
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Programmes can have unintended negative knock on effects. Video:

Even well-intentioned development programmes can increase vulnerability. For example, building embankments for new roads and railway lines can block natural flood drainage channels, and the promotion of heavily irrigated rice agriculture can lead to increased incidence of malaria because mosquitoes breed where there is standing water.