The human factor

Flood event in Meissen, Germany 2005 (photo: U. Herrmann, GFZ).

The extent of the damage caused by a natural hazard and, in general, the question whether a natural event turns into a disaster strongly depends on how humans in affected regions react on it. Existing methods of estimating the risk of floods generally do not take this „human factor“ into account. An international team of scientists with participation of the GFZ section Hydrology now discusses this issue within a perspective article published in Nature Climate Change.

Flood events are the most expensive natural hazards of the past decades, resulting in global losses worth about 60 billion US Dollar in 2016 alone. Climate change, extreme rainfall events, and an increasing sea level may further intensify the negative effects of flood events in the future. In addition, according to a study from 2015, due to population and economic growth global exposure to floods is expected to grow by a factor of three by 2050. What is the role of human behavior?

Bruno Merz, head of the GFZ’s section Hydrology and co-author of the article: “Besides ‘hard facts’ like frequency or intensity of rainfall it is important to integrate individual perception of the risk by the inhabitants of vulnerable areas, to be able to assess the flood risk”. This perception is thought to directly impact the human behavior and thereby the extent of loss and damage. Earlier studies show that many households of endangered regions underestimate the risk because they lack personal experiences with earlier events or because they in general do not plan far into the future. Individual perception however directly effects how much money is spent on prevention and adaptation measures: with immediate effects on the dimension of loss and damage. Other important factors are individual education levels or level of income.

According to the authors the expert community only recently started to interpret „social vulnerability” as a key factor of risk assessment. This is to a large extent explained by the fact that it is especially challenging to integrate this factor within risk models. However, integrating human behavior is crucial for future disaster prevention in politics and research. (ak)

Original study: Aerts, J.C.J.H., Botzen, W.J., Clarke, K.C., Cutter, S.L., Hall, J.W., Merz, B., Michel-Kerjan, E., Mysiak, J., Surminski, S., Kunreuther, H., 2018. Integrating human behaviour dynamics into flood disaster risk assessment. Nature Climate Change 8. pp 193-199. DOI:

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