Proactive risk management needed to limit impacts of extreme floods and droughts

Just because it never happened before doesn't mean it will never happen

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Floods and droughts are increasing in many parts of the world and causing serious damage. A new study shows that tailoring risk management measures to the worst flood or drought to date is not enough to mitigate the effects of unprecedented events. Dr. Michelle van Vliet participated in this study, which is published today in Nature.

It is very difficult to minimize the impact of extreme events when no such natural disaster has ever occurred in the same area before, according to the research led by the German Research Center for Geosciences (GFZ). First, current infrastructure including dams and reservoirs are designed for a maximum limit, and once that threshold is exceeded, they become ineffective. Second, risk management is mostly reactively implemented or modified after major floods and droughts, while proactive, anticipatory strategies are still rare. This is partly due to a cognitive bias related to the previous rarity of such extreme events, as well as to the nature of human risk perception.

The study was a large-scale international collaboration by researchers from the International Association of Hydrological Sciences (IAHS). Michelle van Vliet, physical geographer and associate professor at Utrecht University, analyzed and compared the effects of droughts on the water quality of the Meuse and Rhine rivers, which is included as a case study in this Nature study. A unique dataset of two consecutive extreme flood or drought events in the same area was created from the study. Regions with large differences in population density, socio-economic, climatic and hydrological conditions on all continents were studied. The analyses confirmed the assumption that adequate risk management generally helps to reduce damage.

Two success stories were also examined, where damage was less despite a higher risk in the second event. Three success factors were identified: effective management of risks and emergencies, high investment in structural and non-structural measures, and improved early warning and real-time monitoring systems.