05/24/2024 – 21:54
Porto Alegre’s flood protection system is considered “robust, efficient and easy to operate and maintain”, but failed because it did not receive the necessary permanent maintenance from the city hall, through the Municipal Department of Water and Sewage (DMAE). This is the assessment of a group of 42 engineers, architects and geologists, who released a manifesto, last Thursday (23), in which they explain what happened for the city to be taken over by water from the Guaíba, in the biggest flood in history. of the capital of Rio Grande do Sul.
Designed in the 1970s by German engineers, inspired by Dutch models, the Porto Alegre system is made up of around 60 kilometers (km) of dikes and dams, from north to south of the capital of Rio Grande do Sul. Important avenues, such as Castelo Branco, Beira-Rio and Diário de Notícias, in addition to the Freeway highway, are dams built to prevent the overflow of water from the Guaíba into urban areas.
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There is also a protective wall, the Muro da Mauá, which functions as a dike for the central area of the city, from the height of the bus station to the Gasometer plant. Along this entire length, there are 14 floodgates, which allow water to enter and exit, and 23 hydraulic pump houses, which also have their own gates, and function as water drainage points, to return, in an eventual flood, to the lake.
The streams that run through the city, such as Arroio Dilúvio, on Avenida Ipiranga, complement the system of internal dikes. The system’s flood level is 6 meters, the height of which in the flood at the beginning of the month did not exceed 5.30 meters.
“The dikes and walls don’t leak. Leaks are present in most of the unmaintained floodgates. Last year, when the system was activated, during the floods that began in Vale do Taquari and which also flooded the metropolitan region, the deficiencies in the floodgates became visible. Easy to fix, but they weren’t. The pump houses themselves, as well as the Raw Water Pumping Stations (EBABs) are flooded”, says the manifesto.
What the engineers say
“The most urgent thing that had to be done was to unbend [comportas], changing the rubbers, was not done. We wouldn’t need to have even 10% of the flooding we had”, argued engineer Vicente Rauber, former director of the former Department of Storm Sewers (DEP), who in the 1990s had already launched a publication on how to prevent flooding in the city, which had following a tragic incident in 1941.
“As emergency measures, [o DMAE] should go there and close the holes, the leaks [das comportas]. A sanitation company works permanently with divers, they are needed to carry out any activity, any repair underwater. Repair the holes and try to reconnect the pump houses, making cofferdams, removing the water inside them. We are in a vicious circle, the pump houses don’t work because they have been flooded, and the water doesn’t come out because there is no pump [funcionando]”, he added during a press conference to launch the Letter.
“We have a dam, which prevents water from entering. The wall and dikes are dams. And, when the dam does not prevent water from entering, there is a system that catches and throws water to the other side of the dam. Very simple, traditional, classic and efficient, it’s easy to do. Just keep the pump houses working, and it will take the water from inside the city and throw it out”, pointed out Augusto Damiani, civil engineer, former general director of DEP and DMAE, hydrologist and master in Water Resources and Environmental Sanitation by the Hydraulic Research Institute of the Federal University of Rio Grande do Sul (UFRGS).
City Hall denies lack of maintenance
When contacted, DMAE reported that, currently, 11 of the 23 pumps are in operation. At the height of the flood, 19 stopped due to flooding or electrical problems. They are being repaired, the agency assured.
Meanwhile, residents of the central and northern regions of the city, where the pumps are not working or are partially operational, suffer from the reoccurrence of floodswhich almost collapsed the city 20 days ago.
“We are working to reconnect the other pump houses. Yesterday [23], during the storm, none were out of operation. We are working on EBAPS [Estações de Bombeamento de Água Pluvial] that are missing. We took the engines out of some of them to dry, while others still haven’t been able to get in due to the flooding. Our teams are working tirelessly to put the entire system into operation as soon as possible,” said DMAE.
In an interview with National Radiolast Wednesday (22), the mayor of Porto Alegre, Sebastião Melo, denied a lack of maintenance in the system and attributed the failure to the system’s design.
“In 1968, 1969, I am the thirteenth mayor of this wave [da década] from 1970 to now. This system was designed one way and it has never been modified. And he had tested it a few times in smaller centers and had responded well. Well, but it had never been tested with the phenomenon of the size that happened,” he stated.
“This phenomenon that happened, the climate, could have happened in any Brazilian city and perhaps it would be no different, because we don’t have cities adapted to this new normal, none. None, especially big cities. So, this tragedy that happened here could happen in São Paulo, Rio de Janeiro, anywhere else. I think Brazil has to think about the new normal”, Melo insisted.
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