Environmental denialism and the flooding of Porto Alegre

Porto Alegre airport flooded


Porto Alegre has the best flood protection system in Brazil. It is considered a “Dutch mini-system”. Why did this system fail in its function of preventing the city from being flooded?


To make my knowledge of the issues surrounding the tragedy we are experiencing in Rio Grande do Sul clear, I must inform you that I was Chief of Staff and Specialist Advisor to the Department of Storm Sewers (DEP), from 1993 to 1996, Director of Conservation and Director of the DEP in 1997, and later General Director of the Municipal Department of Water and Sewage (DMAE) from 2001 to 2004.

Before making any technical observation, it is necessary to note that we are going through an unprecedented disaster. Two factors contributed significantly to configuring this situation: (i) the warming of the Atlantic Ocean (which was on average four degrees above the historical average) and (ii) signs of loss of capacity of the Amazon forest to capture the flying rivers that fly over the region. This combination of factors was aggravated by the excessive warming of the central-west and southeast of the country.

When an Amazon current arrives in the region and clashes with cold southern currents, the flying rivers collapse. Again, it was in Rio Grande do Sul that the phenomenon occurred. And, as a result, almost 90% of its municipalities were affected (some of them were reduced to vestiges). The losses are incalculable and reconstruction will require an indefinite amount of time, as well as enormous resources. Some cities will probably not be rebuilt in the same location where they existed because two floods within eight months have already demonstrated the urban unviability of the respective sites.

But it is also necessary to note that Porto Alegre has the best flood protection system in Brazil, made up of Dikes, Pump Houses, the Mauá Wall, surface and gravity gates, and also the building structure of the gasometer plant. It is a complex that represents investments exceeding one billion dollars, built over several decades (since 1941). The system is robust and capable of protecting the city against flooding up to flood level 6 of the Guaíba (which, it should be noted, was not reached in the events). It is considered a “Dutch mini-system”.

Still, even with the flooding reaching levels never measured before, the system served to delay the arrival of the flood wave and provide time for evacuations – which allowed lives to be preserved. This did not happen in Canoas where, in the ICU of the municipal emergency room alone, nine people could not be rescued, without considering the dead and missing whose final number will only be known when the waters recede.


But it is worth asking: why did the Porto Alegre system – although it saved time for evacuations – fail in its function of preventing the city from being flooded (a fact that has and will generate gigantic health, social, urban and economic damage)? It is necessary to be clear and to highlight: the latest administrations of the municipality of Porto Alegre and the state of Rio Grande do Sul have provided sloppy treatment and the dismantling of public structures in general – the type of which public protective structures are a species.

The concept of the protection system is the same as in the Netherlands. The current collapse, however, happens because basic maintenance services were not carried out and then, as a result, at least two gates could not resist the water pressure and went down: the abandonment of their structures – rusty, stuck, without grease and unpainted – it got to the point that we saw the gate in the central region being activated by a backhoe.

At various times during our management, we carried out preventive maintenance on the gates – both surface and gravity gates – when they received treatments and repairs related to rust, painting, sealing, mobilization and others, to the point that they could be activated manually at any time. if necessary. The gravity gates are submerged in the wells of the pump houses (therefore not visible), and their function is to carry out drainage by gravity when the river level is lower than that of the city.

These gates are part of the structures of the flood protection system: when the river is above level 3 (higher than several areas of the city), they close with the pressure of the river and, then, the flow is made by raising the water. water by activating the pumping system. Its maintenance is expensive and is carried out by highly specialized diving services.

It is important to note that this problem had already appeared in the 2023 flood. However, Mayor Nelson Marchezan (2017-2020) decided to extinguish the DEP – the only Secretariat that is part of the first echelon in Brazil to take care of drainage and the flood protection service – of the administrative structure of the municipality and transformed it into a mere department of the DMAE, dividing its responsibilities between this reduced department and another secretariat of direct administration – a fact that generated disconnection and disarticulation between the tasks that the DEP performed in a unified manner.

Proof of the current leaders' denialism is, for example, in a video of Mayor Sebastião Melo stating on a TV program that the Mauá wall should no longer exist. It turns out, however, that the aforementioned wall is part of the city's protection system against Guaíba floods, it is a concrete curtain in the historic center of the city (2,6 km long) that connects the Avenida Castelo Branco dike to the Usina Gasometer (two structures that are also part of the flood protection system). The wall has surface metal floodgates (gates) which connect the city center to the old port pier.

These gates were built to be opened when necessary (for access to the port pier), as well as closed when the Guaíba flood threatens the city with flooding. Therefore, it is extremely essential that these gates receive permanent maintenance – protection against corrosion and checking of rails, bearings, sealing rubbers, screws and all other components necessary for the full and emergency operation of the equipment. Few of these maintenance routines, however, have been carried out in the last 20 years – and, as a result, at least two of these floodgates collapsed, which is why water invaded the city center and flooded it at the same level as the river.

Now, if the mayor declares that the wall “should no longer exist”, why spend resources on maintaining its complementary structure (dams and floodgates)? Why invest in maintenance and care in pump rooms and their electromechanical equipment? Why invest in repairs and desilting of channels and penstocks?

Mayor Sebastião Melo also propagates the idea that another solution is needed to protect the city. No wall or even pump room. But he doesn't know what that solution would be! What's more: if it existed, this new proposal had to be implemented before destroying the current one.

In the same line of speculation about the demolition of the Mauá wall, there is also a video recording of governor Eduardo Leite. And this management stance presented by Sebastião Melo and Eduardo Leite clearly reveals the nature of their preparation and concerns as public managers: it proves that they are unaware of the protection system for which they are directly or indirectly responsible, as well as their servile stance towards real estate speculation. and the market, the main sources of speculation about the collapse of part of the city's flood protection system.

*Carlos Atílio Todeschini He is an agronomist. He was Chief of Staff and Specialist Advisor to the DEP from 93 to 96, Engineer Advisor to the Mayor of Poa in 96, Director of Conservation and Director of the DEP in 97, and General Director of DMAE from 2001 to 2004.

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