Authorities told to learn harsh peril lessons to mitigate future threats

Risk management has reduced the vulnerability to floods and droughts around the world, but their impact is still increasing worldwide, according to a new study.

It found that the threat increases should there be a secondary event soon after the initial event.

“This intensification of the impact of natural phenomena is particularly noticeable when the second event, rain, floods or drought,  affecting the same region has a higher degree of hazard – more intensity and magnitude – than the first previously recorded event,” it added.

María del Carmen Llasat, professor of Atmospheric Physics at the Faculty of Physics and member of the Water Research Institute (IdRA) of the University of Barcelona, warned the issue remains that many efforts to enhance risk management of flood or drought events consistently looked to meet the level of the previous event and did not take into account the fact that the perils were becoming more extreme.

“This results from the fact that the improvement in management has been based on the parameters of previous episodes, but it has not been designed to cope with such extreme events. The difficulty observed in managing unprecedented events is alarming, especially if we consider that, as a result of the climate change, the hydrological events that are projected are becoming increasingly extreme,” Llasat added.

The study, led by the expert Heidi Kreibich, from the German Research Centre for Geosciences (GFZ), includes the participation of nearly a hundred experts from the International Association of Hydrological Sciences (IAHS).

The study analysed 29 pairs of flood episodes and 15 cases drought episodes in different areas of the world. It aimed to identified how these factors involved in risk have changed between the first and the second episode, generally occurring more than ten years apart, but in the same place.

In the case of Catalonia, the study compared pluvial floods in Barcelona that occurred on 21 September 1995 and on 6 September 2018, and the recorded droughts in the periods 1986-1989 and 2004-2008.

The research found only two success stories, Barcelona and Central Europe, in natural hazard management, out of the 29 pairs of flood events analysed worldwide. In these cases, the hazard of the second recorded event was higher than that of the first, but the recorded damage was lower.

In the case of Barcelona, following the 1996 floods, the city promoted a plan that culminated in the construction of 15 rainwater retention basins and the improvement of the entire flood prevention and management system.

“The improvements in Barcelona’s rainwater network over the last twenty years have been decisive in alleviating the effects of floods in the city. In fact, while in the Metropolitan Area of Barcelona there has been a slight increase in flooding since 1981, this trend is negative in Barcelona. However, this is not enough,” explained Llasat.

Efforts to promote more operational and effective responses to these extreme events face a number of obstacles. “Large investments such as those made in the city of Barcelona or in Central Europe are not possible for everyone. In fact, they would not be desirable either. Recent studies have shown that they can lead to a false sense of security (especially in the case of river flooding), as they increase the occupation of flood zones and thus the associated risk”.

“Despite structural improvements,” Llasat continued, “the United Nations consider that Barcelona is not doing enough to raise awareness of the risk of flooding among its inhabitants, nor among visiting people. This is a widespread problem.”

Improving governance, applying nature-based solutions and involving citizens are the global key actions for mitigating the effects of natural hazards worldwide, in a context of sustainable development Llasat concluded.