Imprimir Republish


Avoiding recurrent misfortunes

Study pinpoints the most vulnerable points in the Metropolitan Region of São Paulo and shows the need for a new model of occupancy and mobility

RICARDO NOGUEIRA/FOLHA IMAGEM/FOLHAPRESSDwellers isolated in the Jardim Romano neighborhood, on São Paulo’s east side. RICARDO NOGUEIRA/FOLHA IMAGEM/FOLHAPRESS

Short term extreme events, as for example the heavy rains that poured down on São Paulo, Rio de Janeiro, Angra dos Reis, and other Brazilian cities causing tragic consequences will intensify because of the climate change on course over the last few decades. These problems will continue in the coming years, as shown in an extensive study conducted by the Brazilian Research on Climate Changes Network (Rede Clima) and the National Science and Technology Institute for Climate Changes; The study, the topic of which is cities, is under the coordination of Carlos Nobre, from the Science of the Terrestrial System Center of the National Space Research Institute (Inpe). Until recently, the study was also being coordinated by Daniel Joseph Hogan, from the Center for Population Studies (Nepo) of the State University of Campinas. However, Daniel Joseph Hogan passed away on April 27 (see page 41). “These extreme climate events did not occur as frequently in the 1930’s, or even in the 19th century, as they do nowadays in São Paulo City,” says Carlos Nobre. “This is due to climate changes not necessarily provoked by global warming,” he points out. The most likely reason is that the source of most of these climate changes is the Metropolitan Region of São Paulo; more specifically, the source is an effect that climate experts refer to as “urban heat islands.” Urban overdevelopment, the lack of greenery, and poor ventilation because of the countless high-rise buildings standing close to each other are the reasons for the existence of heat concentration in these islands that exist in many cities. “The average yearly temperature in São Paulo is already 2.5 degrees Celsius higher than it was 70 years ago. In comparison with a warmer, cloudless spring day this number goes up 6 degrees,” says Carlos Nobre, who is also the coordinator of the FAPESP Research Program on Global Climate Change.

The first result of this study, which began a year and a half ago, referred to as the “identification of vulnerability to climate change in Brazilian mega cities” will soon be submitted to Gilberto Kassab, the Mayor of São Paulo. The objective is to identify the areas at risk of landslides and flooding in the current scenario and will include projections for 2030 if no action is taken in relation to the urban development model adopted so far for the Metropolitan Region of São Paulo (RMSP), which includes the occupancy of lands on the outskirts of the city. “The images provided by the Landsat satellite reveal that the urban sprawl of the Metropolitan Region of São Paulo stretches for more than 80 kilometers to the east and to the west and approximately 40 kilometers to the north and south. Twenty of the 39 surrounding towns that comprise this Metropolitan Region form a conurbation; in other words, this urban sprawl is a virtually impermeable conurbation that affects the Tiete River basin and the Pinheiros and Tamanduateí Rivers, the Tiete River’s main tributaries,” says Andréa Young, a researcher of population and environment-related issues from Nepo, and an architect specialized in geoprocessing, remote sensors and environmental management. In one of the maps, the researcher analyzed the extension of the urban sprawl by comparing the years 2001 and 2008. “The region where these changes were most significant, where the urban occupancy index is higher than 80%, corresponds to the region of the Tiete and Pinheiros River Basins,” says Andréa. She emphasizes that the urbanization process is disfiguring the remaining stretches of the river basin, is moving into the tributaries and occupying the river’s watersheds and headwaters.

016_meteorologia_171-01The existing risk scenarios were the basis for the preparation of an urban expansion model for the Metropolitan Region in 2030. “The simulation through the Peripheral Expansion Metric model shows us that the occupancy will intensify on the outskirts of the Metropolitan Region of São Paulo, if the current pattern persists, and will exert strong pressure on the existing natural resources,” adds Andréa. If this process actually materializes, new risk areas will appear and the vulnerability will increase in relation not only to the floods but also to the landslides, especially because the heavy rains will become more frequent due to local and global climate changes.

In the field of public health, a study conducted by the Medical School of the University of São Paulo (FMUSP) indicated that every 10 millimeters of rain increases the risk of leptospirosis by approximately 12% after two weeks. “When you add up climate changes, air pollution and increased humidity, it is possible to build a model that is able to predict 70% of the variability of infectious respiratory diseases,” says Paulo Saldiva, a professor at FMUSP. When cold weather and high humidity conditions result in the so-called damp cold, polluting gases such as sulfur dioxide (SO2) and carbon monoxide (CO) lead to an increase in the number of diseases that affect the upper respiratory tract. Damp cold, associated with ozone (O3) and inhaled particles whose diameter is smaller than 10 microns, is the cause of hospital stays for the treatment of lower respiratory tract diseases, such as asthma and bronchitis.

Automotive vehicles account for 40% of particle emissions and 31% of the SO2 emissions, while industries account for 10% of particle emissions and 67% of the SO2 emissions in the atmosphere, according to data in the report. More than 30.5 million trips take place every day in the Metropolitan Region of São Paulo; approximately 12 million of these trips are made by public transportation and 8.1 million trips are made by private transportation. “As land is negotiated as if it were merchandise, some regions become very expensive and the low-income population is pushed out to the outskirts,” says Saldiva. This means that people have to commute long distances to and from their homes and places of work, which results in high energy consumption by vehicles and excessive air pollution.

The maps that evaluate the risks of floods and landslides in the Metropolitan Region of São Paulo – an area of 8,051 square kilometers inhabited by more than 19 million people, according to the estimates of the State Data Analysis System Foundation (Seade) for the year 2008 – were prepared by using an innovative computer model to map land. This model shows in detail the lowlands that lie next to rivers and streams, at different heights in the relief, such lowlands are subject to floods. This model also shows the slopes subject to landslides. Named HAND (the acronym in English for Height Above the Nearest Drainage), the model, created by researcher Antonio Donato Nobre, from the National Institute for Research on the Amazon Region (Inpa), and his team at Inpa’s Center for Earth Science, levels all waterways on the land to zero level and re-maps all the other points of the topography according to the vertical distance compared to the level where the closest surface water lies. The image is that of a digital map of the landscape following the course of the water running down the street according to the topography of that specific portion of the land, until the point where the water flows into the river. This model was originally developed to evaluate the land and hydrologic system of the land in the Amazon Region. Later on, this model was extended to other applications.

“The HAND model shows the contrasts in the land in physiographic terms very accurately, emphasizing the differences in the physical environment,” says researcher Agostinho Ogura, from the Risk and Natural Disasters Management department at the Technological Research Institute (IPT), who took part in the project to calibrate the downward slopes for the Metropolitan Region of São Paulo. The model uses three classification categories to show when the decline of a slope, in association with degrees, makes the condition critical for landslides; from 15 to 30 degrees, the land is highly susceptible to landslides; from 5 to 15 degrees, the susceptibility in relation to instability is lower. “The destabilization of slopes prone to landslides is correlated to episodes of heavy rains, generally caused by rainfall with total volumes higher than 100 millimeters,” says Ogura. “Such heavy rains and high volumes had not occurred in the last 100 years. They are beginning to occur now and will occur more frequently in the future, because of climate change,” says Carlos Nobre.


The areas susceptible to flooding, identified quantitatively for the first time through the application of the HAND method, were overlapped onto the urban sprawl, making it possible to visualize the more vulnerable areas of occupancy. Excess water outflow caused by the lack of natural vegetation coverage tends to gather on plains and valley bottoms in the water catchment area. By using the HAND method, the local government’s Emergency Management Center (CGE) was able to clearly identify more than 400 sites susceptible to flooding, which leads to chaos in São Paulo City during heavy rainstorms. Some points are predictable, because they are located in the regions that were once part of the lowlands lying along the Pinheiros and Tietê Rivers. Originally, these lowlands were sinuous; later on, they were rectified to open up beltways and construction sites.

The Megacidades [Megacities] project, funded by the United Kingdom’s Global Opportunities Fund Climate Change and Energy Programme, by the Rede Clima network and by the National Science and Technology Institute for Climate Changes, with the support of the FAPESP Research Program on Climate Changes, encompasses an extensive survey on the climate, pollution, land relief, hydrography, land use and occupancy, health, social-demographic characteristics of the population, and other information. The program includes future scenario projections for Brazil’s two biggest urban complexes with a population of over ten million people; namely, the Metropolitan Regions of São Paulo and Rio de Janeiro. “The objective of our research is to produce a summary of the work conducted by many experts who deal with these issues on a daily basis,” says Hogan. “We want a product that is accessible not only to researchers, but also to the authorities responsible for public policies and to the population in general.”

A second map, with details on the Metropolitan Region of Rio de Janeiro, is being prepared by the same research team, in collaboration with researchers from the Federal University of Rio de Janeiro (UFRJ). This map is scheduled to be concluded in July. In the case of São Paulo, several steps were concluded before the final report was ready. An international panel discussion with specialists was held with the objective of conducting a preliminary diagnosis on each Metropolitan Region. The panel discussion was based on existing knowledge on climate changes and on crucial issues related to dealing with such changes. The panel discussion was held in two stages in July 2009. The first panel discussion was held in Rio de Janeiro’s Jardim Botânico botanical gardens, while the second panel discussion was held at the FAPESP auditorium in São Paulo. Researchers from Brazil, the United States, the United Kingdom, and Argentina presented papers and talked about projects developed in New York, London and Buenos Aires.

The emphasis on vulnerability and on actions to adapt to climate change is the core of the report and reflects the work of the panels. “It is necessary to start from a historical, geographical and social understanding of the urban environment in local and regional terms to understand how specific impacts and hazards will affect specific localities,” says Carlos Nobre. In this context, the adaptation involves a set of actions that cities and institutions will have to meet in the search for solutions to the impacts and hazards they will suffer.

RAFAEL ANDRADE/FOLHA IMAGEM/FOLHAPRESSHeavy rains caused landslide behind the Contemporary Art Museum/MAC in the city of Niterói (State of Rio de Janeiro)RAFAEL ANDRADE/FOLHA IMAGEM/FOLHAPRESS

The document proposes that the necessary policies and strategies to take global climate changes into account should be complementary, with focus on clean development, toxic residue removal, and environmental restoration mechanisms. “It is necessary to consider another kind of urban model, based on planning and control of the use of the land,” says Ogura. The City of São Paulo’s land use policy is the result of an agreement with the Public Prosecutor’s Office to develop housing projects in hazardous areas. The inhabitants of the former Favela do Gato, shantytown, for example, located on the Tietê beltway across from the Anhembi complex, used to live in flimsy shacks in an area subject to flooding, because it was located on the banks of the Tamanduateí River. Nowadays, they live in an urban housing development located next to the former site.

“The process to improve housing quality conditions for people living in risk-prone areas will have to continue, because our studies indicate that heavy rainfall will become increasingly more frequent and severe on account of climate changes,” says Ogura. If no measures are taken in this respect, deforesting will continue taking place on lands still covered with vegetation, because the low-income population, displaced by property development pressures, is pushed farther and farther away from central regions. This will lead the urban heat island effect to worsen. “The increase in the number of poverty-ridden areas surrounding the cities will be concentrated on the outskirts, bringing on diseases associated with vulnerability. The quality of the water will get worse, outbreaks of diarrhea and dengue fever will increase, as will urban violence,” Saldiva points out.

One of the proposals of the report is to quantify the benefits resulting from measures to adapt to climate changes, to subsidize the decision-making process. To exemplify, the researchers refer to an experience conducted by the State of São Paulo’s Water and Electric Power Department (Daee), which quantified the benefits resulting from the implementation of urban drainage works.

016_meteorologia_171-02Costs related to traffic interruption or delays caused by flooding were taken into consideration in areas with constantly busy traffic. Due to the drop in average cruising speed, the standard costs related to the operating of vehicles increases threefold. In the case of cars, the values range from R$ 0.26 to R$ 0.78 per kilometer. In the case of trucks, they range from R$ 1.50 to R$ 3.00 per kilometer. The average time wasted during traffic flow interruptions caused by flooding can come to three hours; estimates are that this waste of time corresponds to R$ 6.00 per hour per passenger, in the case of cars, and R$ 2.00 per hour per passengers riding or driving buses and trucks.

“For example, it is possible to show the cost of recovering an area subject to landslides by removing the shanties, implementing urban housing projects and recovery of blighted areas,” says Ogura. In addition, it is also possible to take preventive action, such as removing dwellers from risky situations, by resorting to monitoring and information systems in real time that allow the tracking of rainfall and adverse meteorological conditions; this can be combined with fine-tuned mapping of the more vulnerable areas.

The document includes the principles that should guide discussions on land use policies, the re-occupancy of space and mobility. The document also proposes partnerships. “Science cannot be the only factor for the formulation of public policies,” says Saldiva. Furthermore, he adds, unless political actions are implemented, the growth of the urban sprawl will put even more pressure on water reservoirs. The experience acquired from the studies on the cities of São Paulo and Rio de Janeiro can be replicated for other big cities in Brazil. A new study, focused on the cities of Belém, Recife, Belo Horizonte and Curitiba, financed by the Ministry of the Environment, is scheduled to begin in the second half of the year. “In a couple of years, we will have the first map showing the vulnerability in Brazil’s main cities to climate changes. This information will help guide public policies focused on reducing such vulnerability,” says Carlos Nobre.