06/22/2024 – 13:52
At a time when Brazilians are still following, almost in disbelief, the consequences caused by the storms of April and May in Rio Grande do Sul, Brazil received a visit from the Chinese architect and landscaper Kongjian Yu, creator of the sponge city concept, which uses nature itself to better resist the increasing occurrence of storms.
“I hope that Brazil can be a reference on how we should build the world”, says the professor from Peking University, who came to the country at the invitation of the National Bank for Economic and Social Development (BNDES).
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Last Tuesday (18), he participated in a seminar at the bank’s headquarters, in Rio de Janeiro, on national and international experiences in rebuilding cities devastated by environmental tragedies.
The meeting was motivated by the calamity that hit Rio Grande do Sul, classified by the governor of Rio Grande do Sul, Eduardo Leite, as the “biggest climate disaster in Brazil” in terms of territorial extension and economic impact. More than 170 deaths have been confirmed.
Kongjian Yu highlighted that he was impressed with the emphasis that BNDES has given to issues related to the search for a greener future. “I had never heard a financial institution talk so much about climate change, green solutions and determination for Brazil to become a reference in building a sustainable future,” he said.
“I’m proud to be here to share my experience of how the planet can be sustainable,” he added.
Peasant origin
Yu said he started thinking about the concept of a sponge city when he realized that the village he lived in, in Zhejiang, a province in eastern China, was being repeatedly affected by floods.
According to the professor, the problems worsened as what he calls “gray infrastructure” advanced, the increasing presence of concrete in cities, channeling rivers and waterproofing large areas.
In this way, he put into practice landscaping projects that privilege nature itself to deal with floods, prioritizing large floodable areas and the presence of native vegetation. Thus, parts of cities become a kind of sponge, with the capacity to receive flooding and give “time” for the water to drain, reducing damage to inhabited areas.
“The flood is no longer an enemy, in short.
The success of Yu’s project led to sponge city landscaping being used on a larger scale in more than 250 Chinese cities and also replicated outside the country.
In 2023, the pioneering spirit and scope of the concept earned Yu the Cornelia Hahn Oberlander International Landscape Architecture Award.
The concept developed by Yu is not limited to creating areas whose sole purpose is to be a floodable space. He works with the harmonization between buildings and nature. The most common examples are parks that, during dry seasons, are frequented by people. Many are a tangle of trails and walkways surrounded by small lakes and lots of greenery. “Safe and beautiful,” he describes.
Yu attributes this knowledge of dealing with the environment without drastic interventions – building retaining walls and channeling rivers – to the wisdom of ancestors.
“It’s nothing new for those who have lived in monsoon regions for thousands of years,” he said, referring to the season of winds that cause storms in Southeast Asia.
Against gray infrastructure
Kongjian Yu is critical of gray infrastructure.
“We spend billions of dollars canalizing rivers, building dams, dikes, trying to keep cities and villages from flooding.”
According to the architect, these interventions should be considered to resolve immediate issues in the short term only. “There is no always safe dam, which increases the potential danger of flooding,” he said.
“I hope Brazil can learn from this. Learn from what went wrong in China,” he warns, referring to the increasing use of engineering interventions.
He also mentions that cement production is an emitter of greenhouse gases. Therefore, reducing the presence of gray infrastructure directly contributes to reducing the level of pollutants released into the atmosphere.
The Chinese landscaper argues that the concept of a sponge city is a systematic solution for a trajectory of resilience, a philosophy opposed to gray infrastructure, and which consists of retaining water where it falls. “This is the idea of the sponge planet”, he points out.
The professor at Peking University explains that part of the rise in sea levels – a phenomenon that threatens islands and coastal countries – is due to rainwater runoff and, according to Yu, if this water is stored in the region where the rains occur , could be absorbed in the same area, reducing the volume taken to the oceans.
Brazil
Yu praised Brazilian biodiversity and was enthusiastic about the role that Brazil can play on the planet. “You are a hope, you are still a very young country.”
Despite his optimism, he criticized the way agriculture is cultivated. “I see kilometers and kilometers of soybeans. There is no room for water. You may be using the wrong techniques. A small, simple solution can change the situation dramatically: turn the earth into a sponge to capture more water,” he recommended.
The architect considers that one of the first steps towards creating sponge cities is the creation of a master plan, in which it is clear “which space to provide for water and where not to build”.
He recommends that floodable areas be filled with forests, parks and lakes. “Our solution is to remove the wall. Let the water in. The water irrigates the park.”
Retaining walls are, in the landscaper’s view, a threat. He explains that when overflows occur, concrete surfaces act as barriers that prevent water from returning to the riverbed.
Another negative factor is that channelized rivers – generally more straight and with fewer curves than natural routes – increase the speed of water flow, instead of slowing it down.
According to Yu, planning is needed so that channelized rivers are transformed into sponge rivers, with vegetation, small green islands that absorb part of the water. “We have to think big”, he encourages.
He understands that, instead of kilometers and kilometers of retaining walls, it is preferable to create a “beautiful wall that breathes, with native vegetation, a green corridor, right in the middle of the city”.
Kongjian Yu considers that individual initiatives can also help cities better perform their role as sponges. He gives the example of buildings and apartments that can absorb rainwater. “It is possible to collect it and take it to the balcony, irrigating vegetable gardens”, he details.
“We need to rethink the way we rebuild our cities. Look for a solution based on nature”, he concludes.
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