The risks of extreme weather events have grown in several countries, mainly due to global warming. Studies estimate that economic damage from floods could double in the world and with droughts tripling in Europe and China if the earth's average temperature increases by 2°C.

A survey of 91 scientists from various countries, including Brazil, published in the journal Nature, shed a light on this discussion. The group analyzed a number of weather events recorded in recent decades around the world and also showed that risk management reduces the effects of floods and droughts. However, it has limited range to minimize impacts of occurrences followed with even greater magnitudes.

According to the paper, if the second event is more intense than the first, the impact tends to be greater for the population when risk management ceases to project extreme cases, such as overflowing rivers or breaking up dams and reservoirs, and/or is based only on previous episodes.

Environmental risk and impacts

"Environmental risk management 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", Eduardo Mario Mendiondo, professor in the Department of Hydraulics and Sanitation at 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 of the Water-Adaptive Design & Innovation Lab (WADILab) and is part of two Research Support Centers (NAPs) of USP: Incline (Interdisciplinary Climate Investigation Center) and Ceped (Center for Disaster Studies and Research in the State of São Paulo).

The study was led by researcher Heidi Kreibich of the German Center for Geosciences Research (GFZ), located in Potsdam (Germany). She is coordinator of the Panta Rhei movement of the International Association of Hydrological Sciences (IAHS), a scientific hydrology organization that turned 100 years old in 2022. The movement has sought in the last decade to build regional and international alliances to give a more integrated, multidisciplinary and inclusive view of the co-evolution of hydrological and social systems, such as in decentralized water supply systems.

Scope

In the global research, data from 45 pairs of extreme floods or droughtevents recorded in the same area with an average interval of 16 years between one and the other were analyzed. There are 26 events paired with floods and 19 droughts in different socioeconomic and hydroclimatic contexts of 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 subsequent impacts.

In the case of Brazil, researchers from EESC-USP developed studies in the water supply system of the Metropolitan Region of São Paulo, including the Alto Tietê and the Cantareira Basin basin. "The São Paulo system, despite involving smaller rivers when compared to other regions, such as the Amazon, has a huge 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 longer-lasting solutions," explains Mendiondo.

Scientific evidence

In São Paulo, scientists point out that the construction of reservoirs to contain drought effects is fundamental for water safety. However, its success is conditional on permanent campaigns of popularization of 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 major droughts of the 21st century without the need for construction or expansion of 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 [the cultivation of] better habits, the construction of more reservoirs can even induce greater water consumption, increasing risks of water deficits in the future and increasing a dangerous circle of water insecurity. That's what happens today in California [United States] and Shanghai [China]," he notes.

Above all, to exemplify, Mendiondo cites the result of another study published in February this year comparing the droughts that hit the Metropolitan Region of São Paulo 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 in few reservoirs exposed the region to greater vulnerability. Among the authors of this research are doctoral student Felipe Arguello de Souza and former students of EESC-USP Guilherme Mohor and Diego Guzmán, all co-authors of the article now published in the journal 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. However, two common factors stand out:

• Improving risk management governance, 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 interdisciplinarity when dealing with these issues, including research, which can prevent science from being isolated or addressed 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.

Risk issue

The researchers used risk concepts that consider impact as a result based on three factors:

• Danger;
• Exposure;
• Vulnerability.

All three can be exacerbated by management deficiencies. In the analysis, direct (fatalities, monetary, monetary), indirect (interruption of traffic or tourism) and intangible (impact on human health or cultural heritage) impacts were evaluated.

The danger reflects the intensity of an event, such as a flooded area or drought deficit, measured by the standardized precipitation index. The exhibition evaluates 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 still be aggravated by the suboptimal implementation of non-structural measures, such as risk-conscious regional planning or early warning.

Source: Canal Rural