Risk management policies are still insufficient to limit the impact of extreme weather effects

The impacts of extreme weather events have grown in several countries, mainly due to global warming. Studies estimate that economic damage from floods could double worldwide and from droughts triple in Europe and China if the Earth’s average temperature increases by 2°C. As a result, risk management policies for environmental disasters have gained increasing importance.

A survey with the participation of 91 scientists from several countries, including Brazil, published in the journal Nature shed light on this discussion. The group analyzed a series of climatic events registered in the last decades in the world and showed that risk management reduces the effects of floods and droughts, but has limited scope to minimize the impacts of consecutive occurrences with even greater magnitudes.

According to the work, if the second event is more intense than the first, the impact tends to be greater for the population when risk management fails to project extreme cases, such as the overflow of rivers or the rupture of dikes and reservoirs. , and/or is based on previous episodes only.

“The management of environmental risks has to be revisited and seen as a niche of real opportunities. The path is challenging and full of opportunities, as in the case of Brazil”, says Eduardo Mario Mendiondo, professor at the Department of Hydraulics and Sanitation, to Agência Fapesp. from the School of Engineering of São Carlos, University of São Paulo (EESC-USP), and co-author of the article.

Mendiondo is a researcher at the National Institute of Science and Technology for Climate Change Phase 2 (INCT-MC2), which is supported by Fapesp. He is also a mentor at the Water-Adaptive Design & Innovation Lab (WADILab) and is part of two USP Research Support Centers (NAPs): Incline (Interdisciplinary Climate Investigation Center) and Ceped (Center for Studies and Research on Disasters in the State of Sao Paulo).

The study was led by researcher Heidi Kreibich, from the German Research Center for Geosciences (GFZ), located in Potsdam (Germany). She is coordinator of the Panta Rhei movement, of the International Association of Hydrological Sciences (IAHS), a scientific organization of hydrology that completed one hundred years in 2022. The movement has sought in the last decade to build regional and international alliances to give a more integrated, multidisciplinary and inclusive of the co-evolution of hydrological and social systems, as in decentralized water supply systems.

Coverage

In the global survey, data from 45 pairs of extreme floods or droughts events recorded in the same area with an average interval of 16 years between them were analyzed. There are 26 paired flood events and 19 drought events in different socioeconomic and hydroclimatic contexts on all continents, which occurred between 1947 and 2019. One of the objectives was to verify how factors involved in the risk changed between the first and second extreme episodes and their consequences. subsequent impacts.

In the case of Brazil, the EESC-USP researchers carried out studies on the water supply system of the São Paulo Metropolitan Region, including the Alto Tietê and the Cantareira System basin. “The São Paulo system, despite involving smaller rivers compared to other regions, such as the Amazon, has enormous relevance not only for the large number of residents served but also for the synergy involving various sectors. By bringing new perspectives, the study promotes participatory, decentralized and more lasting solutions”, explains Mendiondo.

In São Paulo, scientists point out that the construction of reservoirs to contain the effects of droughts is essential for water security. However, its success is conditioned to permanent campaigns to popularize science and educational policies that encourage the rational use and reuse of water.

“Scientific evidence proves that, if the reuse of rainwater had been planned in a safe and decentralized way in the Metropolitan Region of São Paulo in the last 40 years, it would be possible to live with the three great droughts of the 21st century without the need to build or expand large water reserve systems and without rationing in the neighborhoods. This shows that the influence is not only of the climate factor, but also of the type of planning that is prioritized. It depends on the cultural co-evolution between water and society: without cultural awareness and [o cultivo de] better habits, the construction of more reservoirs can even lead to a greater consumption of water, increasing the risks of water deficits in the future and increasing a dangerous circle of water insecurity. This is what happens in California today. [Estados Unidos] and in Shanghai [China]”, observes the teacher.

As an example, Mendiondo cites the result of another study published in February of this year comparing the droughts that hit the São Paulo Metropolitan Region in 1985-1986 and in 2013-2015 (more extreme than the first). The result showed that the delay in the implementation of public policies for the decentralized reuse of rainwater and the dependence of service areas on few reservoirs exposed the region to greater vulnerability. Among the authors of this research are doctoral student Felipe Arguello de Souza and former EESC-USP students Guilherme Mohor and Diego Guzmán, all co-authors of the article now published in Nature.

Success

Among the 45 events analyzed in the new study, only two stories were considered successful — one in Barcelona and one in Central Europe. Two common factors stand out: improved governance of risk management, with more integration into emergency management and early warning systems; and the implementation of a series of structural measures that required high investments, such as the construction of rainwater reservoirs and dikes.

Another point that scientists highlight as positive is the interdisciplinarity when dealing with these issues, including research, which can prevent science from being isolated or approached in “silos”, without open dialogue. An example of this interdisciplinary action is the encouragement of new risk transfer instruments, such as insurance indexed to climate change.

The researchers used risk concepts that consider impact as an outcome based on three factors—hazard, exposure, and vulnerability. All three can be exacerbated by management deficiencies. In the analysis, direct impacts (fatalities, monetary damages), indirect impacts (traffic interruption or tourism) and intangible impacts (impact on human health or cultural heritage) were evaluated.

Hazard reflects the intensity of an event, such as a flooded area or drought deficit, as measured by the standardized precipitation index. Exposure assesses the number of people and assets in the area affected by the event, that is, changes in this factor are influenced by changes in population density and socioeconomic developments.

Exposure and vulnerability can be further compounded by suboptimal implementation of non-structural measures such as risk-aware regional planning or early warning.

The article “The challenge of unprecedented floods and droughts in risk management” can be read here.