Porto Alegre in Brazil: A Flood Disaster is Waiting to Happen - Latest Global News

Porto Alegre in Brazil: A Flood Disaster is Waiting to Happen

Porto Alegre, the Brazilian metropolis that was flooded after torrential rains, was lulled into a “false sense of security” by a vast but outdated flood defense system, a city drainage engineer told AFP.

Leomar Teichmann said a network of dikes, levees and a massive wall was intended to protect about 40 percent of the state capital of Rio Grande do Sul in southern Brazil, where 150 people died and hundreds of thousands were forced from their homes.

Teichmann is an engineering consultant and former deputy director of water and wastewater services in Porto Alegre, a city of 1.4 million people on the banks of the Guaiba Estuary.

He told AFP he had already warned in 2019 that the city was in danger.

– What does the system consist of? –

“The system was designed after floods in 1967 and built in the 1970s. It includes about 65 kilometers (40 miles) of dikes and a 2.67-kilometer-long concrete wall, as well as 14 flood gates and 22 stormwater pumping stations.

“It was a simple system that seemed functional as it guaranteed the protection of the urbanized part of Porto Alegre.

“However, it was not tested in practice until November 2023, because only on that occasion did the level of the Jacui River exceed three meters (10 feet), equivalent to the level of the Maua Wall,” causing flooding, he explained .

“In other words, the system stood for 51 years without the water from the Jacui River ever touching the wall.”

– Why did it fail in the recent floods? –

“Gate number 14 gave way under the great pressure of the water and began leaking with great volume and speed.

“The volume of water was so great that the nearby pumping stations were quickly flooded and the pumps were switched off.

“The flooding caused by the gate failure was so rapid that the entire region was inundated within a few hours.

“This flooding eventually led to a power outage in the flooded areas and as a result, all pumping stations north of the gasometer plant ceased operations,” he said, referring to an out-of-operation power plant.

“There were several failures one after the other. Within about 24 hours, the water levels on both sides of the system were exactly the same.”

– What were the consequences of these failures? –

“Already in 2019, I explained that the protection system installed in Porto Alegre gives the population a false sense of protection and security, since there is no way to contain the water in the event of a failure of any of the elements that make up this system .”

“It is an outdated system that is prone to failure in many places and requires high investments in operation and maintenance.

“Much is said about Porto Alegre, but the same type of flood protection system was built in Canoas, Sao Leopoldo and Novo Hamburgo (other municipalities in the state), where the system was also overwhelmed by water levels.

“In all of these cities, water very quickly entered areas that should have been protected and caused greater tragedies than if the system had not existed.”

Teichmann explained that the water flowing over the dikes was moving much faster than the rise in river levels.

“I’m not saying levees are useless, but in a flood of this magnitude, once the water overcame the levees, the speed at which the water flowed to the other side was much higher than if the levees were not in place.” exist.”

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