On January 25th, during São Paulo’s anniversary, the artist Rodolpho Tamanini Netto, 73, was found dead at his house after a catastrophic flood hit the city.
According to the police, the main suspicion is that the man drowned after the rainwater invaded his residence, located at a famous alley called “Beco do Batman”, in the west side of the city. The storm was classified as the most severe recorded in the capital in the last 64 years.
WHY FLOODS ARE HAPPENING IN SÃO PAULO?
Events of this magnitude – flooded houses and establishments, impassable streets and marooned people – have become increasingly common as a result of the thunderous inundations that are occurring in the state of São Paulo. In the past few months, the city has seen a sudden increase in the number of floods, which has led the authorities to declare a state of alert in all risk areas. But what explains the growth of inundation during rainfall in the capital? Some factors may help to understand the phenomenon.
- Poor city planning
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Before urbanization, São Paulo was full of natural rivers and streams, which naturally overflowed during heavy rains. Over time, the city expanded and, consequently, the need for space grew as well. As a result, rivers such as the Tietê and Pinheiros were channelized and transformed into avenues, modifying the water cycle. Now, when it rains, the water continues to flow normally, but without the floodplains that were transformed into asphalt, it accumulates more easily, therefore contributing to flooding.
- Uncontrolled growth
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Another factor that increases the potential for inundation is related to the disorganized growth of the capital city. Due to the intensification of industrial development and urban expansion, São Paulo experienced a very strong demand for housing and urban infrastructure.
Thus, with no more space, buildings started being constructed in high-risk areas, such as riverbanks and hillsides, obstructing water runoff and amplifying the vulnerability of these regions. Furthermore, without any kind of supervision, it becomes more susceptible to flooding, exposing citizens to potential danger.
- Deficit of green areas and waterproofing
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As the city developed, new demands emerged to facilitate access and improve urban life. What was once land and vegetation, gradually gave way to pavement and asphalt, making the soil impermeable. Although important in many cases, excessive waterproofing in the city of São Paulo increasingly contributes to flooding.
This happens because when rainwater falls, it needs to run off somewhere. However, without the green areas that once absorbed the water and with impermeable soil, it has nowhere to go, accumulating and causing floods. Also, the manholes that are supposed to help with drainage are often blocked by improperly discarded garbage, worsening the flooding situation.
- Climate change
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According to research conducted at the IAG-USP Meteorological Station, over the past 90 years, rainfall in São Paulo has increased by approximately 5.5 mm per year. It’s true that the capital is known as the “land of drizzle”, due to the frequent showers common in tropical climates. However, the trend from now on is for these showers to become stronger and more persistent, as a result of climate change.
But what does this have to do with floods? The climate crisis directly affects the regularity of rainfall. The concentration of greenhouse gases in the atmosphere causes more heat to be absorbed, raising the city’s temperature. As a result, the humidity in the air increases, leading to heavier and more frequent rainfalls. Following that, as mentioned earlier, São Paulo lacks the necessary infrastructure to manage such large volumes of water, making floods increasingly common.
WHAT CAN BE DONE TO ADDRESS THE ISSUE?
Finding solutions to the problem of flooding in São Paulo is a complex and challenging process; as it involves various social, economic and environmental issues. Despite these challenges, experts unanimously agree on one crucial point: preserving the environment and promoting sustainable practices are essential to reversing the path that the capital is taking, increasing floods and their associated damage.
To address these issues, some suggestions debated by experts may be effective in preserving the environment and reducing flooding in the capital.
- Linear park
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Combining leisure, environmental preservation, and natural drainage, linear parks stand out as a key solution for mitigating flooding. Designed parallel to rivers and streams, they enhance the region’s drainage system by creating permeable areas that absorb rainwater, preventing it from running over the asphalt and leading to floods.
When heavy rains occur, the excess water from rivers is redirected into these parks, where it´s gradually absorbed by the vegetation instead of overwhelming city streets. Additionally, since linear parks are predominately established in floodplain areas, they also serve as a barrier against irregular occupation in these high-risk zones.
- Rain garden
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A rain garden is a green space designed to build up soil permeability, acting as an urban sponge in the areas where they are set up. Unlike linear parks, which are extensive and provide recreational benefits, rain gardens are typically smaller, often implemented on private properties or in specific urban areas prone to water accumulation.
In these gardens, rainwater penetrates into the soil through an underground drainage system composed of three distinct layers: an infiltration pit about one meter deep; a structure made of gravel, soil, and organic compost; and then, plants and flowers.
Their primary function is to reduce surface runoff, which happens when rainwater cannot be sponge up due to the impermeability of asphalted streets and sidewalks. By filtering the water, rain gardens help prevent flooding, decrease the amount of pollution in water bodies, and improve overall water quality.
- Permeable sidewalk
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A permeable sidewalk is basically a surface that allows water to pass through, helping to manage drainage and reduce surface runoff in urban areas. This kind of pavement is very similar to the convencional one, but the main difference between both is that the permeable has gaps in its structure, which are essential for the passage of water.
The permeable sidewalk is composed of several layers: the top layer consists of porous materials, such as blocks or specialized concrete; lower down, there is a layer of gravel or crushed stone that directs the water for the other layer; and at the bottom, a layer of sand or other filtering materials that absorb and stock water before it reaches the ground.
This type of pavement helps retain water for longer, reducing flow in watercourses and preventing flooding by draining a significant amount of rainwater.
- Reservoir
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Reservoir is an artificial area designed to store excess rainwater, helping to reduce flooding. Usually built underground, reservoirs help control the flow of water, preventing the drainage system from being overloaded and, consequently, flooding.
An example of a reservoir in São Paulo is the one of Pacaembu, located under the Charles Muller Square, in the west of the capital. It’s the city’s first covered reservoir, which was created to contain the floods that used to occur over there. It’s worth pointing out that this type of project requires a high level of conservation and monitoring, in order to avoid problems such as the accumulation of garbage, the spread of disease and other problems.
NOW THAT WE KNOW WHAT TO DO; WHAT ARE THE NEXT STEPS?
Considering all the damage that floods have caused to the city of São Paulo and its population, it’s crucial to bring together all the solutions in order to reverse the situation immediately. The implementation of projects focused on preserving, protecting and restoring green areas is fundamental to reducing the impact of flooding.
It’s impossible to discuss environmental disasters without addressing climate change. From now on, the trend is for these events to become more frequent, and for the consequences of global warming to become even clearer.
For this reason, in addition to everyone doing their part through daily actions, it’s indispensable that citizens pressure the government to adopt effective measures against the climate crisis, demanding changes in the city’s public policies. Only with concrete efforts will it be possible to repair the damage already caused and prevent the population from future impacts.
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The article above was edited by Maria Clara Polcan.
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