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Disaster thresholds

If we consider the definition of disaster as an event where the functioning of a community or society is seriously disrupted and unable to function as normal (Oliver-Smith, 2005), should the number of people who are impacted matter?

There are various thresholds in terms of impacts on people used by those working within the disaster risk reduction and disaster management community which have to be surpassed before an event is classified as a disaster (Malilay et al. 2014; Weissman 2018). These thresholds are often defined as a basis for data collection (Malilay et al. 2014).

Both hazard and disaster data can help to shape future policies. Decision-makers at the national level are unlikely to be hazard or disaster experts and will need to see evidence of frequency and scale – deaths and economic losses, provided by using disaster data so that they can embed the results into policy for disaster risk reduction and development.

One such database is EM-DAT, which is a global database focused on disasters caused by natural or technological hazards. As stated on its website, its main objectives are:

[…] to assist humanitarian action at both national and international levels; to rationalise decision-making for disaster preparedness; and to provide an objective basis for vulnerability assessment and priority setting.

(EM-DAT 2009a)

For the purpose of their work, EM-DAT includes all disasters from 1900 until the present but only those which conform to at least one of the following criteria:

  • 10 or more people dead
  • 100 or more people affected
  • The declaration of a state of emergency
  • A call for international assistance

(EM-DAT 2009b)

There have been critiques that this excludes smaller disasters or emergency events which may not meet many of their criteria but will impact on a significant number of people (Richardson et al. 2018).

Some research has suggested that over 50% of disaster losses (both in terms of lives lost and economic input) are not recorded or acknowledged (GNDR 2015). These disasters often occur in regions with little connectivity or access to official response and as such, data is often not collected (Rentschler 2013).

Though more numerous, these events are often smaller and receive less attention, both domestically and internationally, than the high profile disasters that attract much more attention.

It should also be noted that the EM-DAT database does not record data relating to war and conflict.

Your task

Given the definitions of disaster that we have discussed, how do you think disasters should be classified?

Are the current thresholds used by EM-DAT sensible or should they be changed to reflect smaller events?

If you think the thresholds need to be changed, what would this mean for the often-difficult collection and analysis process within some countries?

Further reading

More information on the measurement of disasters is available in the following report from the United Nations Development Program:

UNDP (2014) Disaster Resilience Measurements: Stocktaking of Ongoing Efforts in Developing Systems for Measuring Resilience [online] available from https://www.preventionweb.net/files/37916_disasterresiliencemeasurementsundpt.pdf [05 December 2019]


EM-DAT (2009a) Frequently Asked Questions [online] available from https://www.emdat.be/frequently-asked-questions [18 October 2019]

EM-DAT (2009b) Classification [online] available from https://www.emdat.be/explanatory-notes [18 October 2019]

GNDR (2015) Everyday Disasters [online] available from https://www.gndr.org/programmes/item/960-everyday-disasters.html [18 October 2019]

Malilay, J., Heumann, M., Perrotta, D., Wolkin, A.F., Schnall, A.H., Podgornik, M.N., Cruz, M.A., Horney, J.A., Zane, D., Roisman, R. and Greenspan, J.R. (2014) ‘The role of applied epidemiology methods in the disaster management cycle’. American Journal of Public Health, 104 (11), 2092-2102

Oliver-Smith, A. (2005) ‘Global Changes and the Definition of Disaster. in What is a Disaster?. ed. by Quarantelli, E. London: Routledge, 197-216

Rentschler, J.E. (2013) Poverty and Disasters – Why Resilience Matters [online] 26 November. available from http://blogs.worldbank.org/developmenttalk/poverty-and-disasters-why-resilience-matters [18 October 2019]

Richardson, T., Hayward, G., Blanchard, K. and Murray, V. (2018) ‘An Evaluation of Global Hazard Communication with Ethical Considerations’. PLoS currents 1 (10)

Weissman, F. (2018) Mortality Emergency Threshold: A Case for Revision [online] 2 August. available from https://www.alnap.org/blogs/mortality-emergency-threshold-a-case-for-revision [18 October 2019]

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This article is from the free online course:

Disaster Risk Reduction: An Introduction

Coventry University