Miami is torn between bewilderment, pain and disbelief.
The Champlain Towers South, a building of 100 beachside apartments collapsed early Thursday, sparking one of the largest salvage and rescue operations in Miami-Dade County’s recent history.
While relatives of more than a hundred people are still waiting for news of their loved ones and others mourning their losses, many also wonder how it is explained that the construction of 12 plants will collapse.
The authorities insist that it is too early to determine the causes and that it will take months to reach conclusions.
Most experts, without However, it points to a conjunction of factors, which could range from structural problems in the building (q who had just turned 40 years) to possible sinkholes up to constructions in the area or factors associated with climate change.
A report of an expert opinion carried out in 2018 and published on Friday night shows that since then an engineer had found “ major structural damage “, many of them associated with impact of saltpeter, humidity and corrosion due to the proximity of the sea.
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After the collapse, local media also echoed a study carried out on 2020 by Florida International University (FIU) in which the geologist Shimon Wdowinski detected a subsidence of up to 2 millimeters (mm) per year in the area where the Champlain Towers South is located.
According to Wdowinski, the building was the only place in the area where this phenomenon was detected between 1993 Y 1999, period on which the study was based.
However, The expert clarifies that this alone does not explain the tragedy of Thursday morning.
At BBC Mundo we spoke with Wdowinski to learn more about his study, what it may imply for other areas affected by subsidence and for the future of Miami.
Why did you study this area of the building What collapsed?
The study we did sought to determine the levels of subsidence as part of an investigation on the impact and costs of coastal flooding due to climate change.
We studied the entire island of Miami Beach over a six-year period (1993 – 1999) and we use it to detect movements in these communities that suffer the impact of the floods.
So the purpose was to see how much subsidence impacts, how they contribute to flooding and identify areas where they are more frequent.
What did you find in particular about the Champlain Towers Sout h?
The study did not focus on that particular building, but the Champlain It stood out as one of the places that showed the most sinking, approximately two millimeters a year.
This is not much, but we do not know what happened after 1999, to what level continued to sink, if it continued to sink, and how this may have affected its foundation and structure.
In some places like Mexico City, the Soil subsidence level is much higher than what you detected in that area. However, there are constructions, from colonial mansions to cathedrals, that are more than three centuries old and still stand. How then could this subsidence have contributed to the collapse?
It is not so common that buildings where there is a subsidence collapse. In fact, it is very unusual.
What we suggest with the study is that the movement of the building did not start just before the collapse.
There were some processes that they affected the structure for a long period of time. And maybe a point was reached where the structure couldn’t hold the load and collapsed. But this is a structural problem. They are not things that I study.
What we do know is that the building that collapsed in Miami was sinking for decades, but that alone does not explain the collapse.
After the collapse , and also knowing the results of their investigation into the sinking, many people who live in Miami wonder if other nearby buildings could also be in danger.
Looking at the map that we published in our research, there are other points that appear as risk of subsidence, but not in that place. That was a very localized point.
I also want to remember that with this investigation we are talking about something that happened 18 or 30 years. We do not have data to know what happened next.
However, I would say that what we saw here was a very peculiar movement in that building that we did not see in others.
Let’s talk a bit about the technologies you used, how can you detect that a building is sinking?
We have a technology called synthetic aperture interferometric radar (or InSAR) that is based on a radar that sends signals from space that are then compared with other observations that the satellite takes from it place in space.
Signals are sent that hit the ground, trees or buildings, any object on the surface and then some of the signals return to the satellite.
This way you can detect small movements of the order of centimeters and millimeters. This is how buildings that are experiencing subsidence can be identified and that in the future may be compromised.
But in what way could it be compromised by these small sinkholes? If we return to the example of Mexico, the level of collapse of the capital is several centimeters a year and we have only seen buildings like this fall during the earthquakes.
It is surprising that Mexico City is sinking at that rate and millions of people still live there.
Its engineers are used to that and are building buildings that respond to those circumstances. They must ensure that the building is not built on foundations strong enough that it can sink along with the surface.
However, it happens that some of the subway lines were built with a very solid foundation and that is becoming a problem. We have another study that is now under review on the metro system and how some of the Mexico City lines are in very critical condition due to subsidence.
From In fact, the line that collapsed last month was among one of the places we detected as the most dangerous in the city’s subway system. Unfortunately, it couldn’t be published before that crash happened.
However, the article where it warned about the collapse of the building of Surfside yes it was published before it collapsed. Was there any reaction from the authorities after your study? Was any action taken or and carried out another type of investigation to determine the impact or danger of the sinking detected?
The research we did dealt with the danger of coastal flooding. So the focus of that study was to understand how much land subsidence contributed to the flood.
This is how we presented it and how we discussed it in scientific forums.
It is now, after the accident, that the study has taken on that other dimension that was not the one we originally proposed.
But we do believe that the technology we use could be used to detect similar situations.
Miami Beach is one of the areas most affected by this problem , according to your study, why does that happen on an island that is one of the most expensive areas s in South Florida?
Miami Beach It is built on a barrier island that is natural land. The eastern part of the city, which is a higher elevation, is built on limestone rocks.
The western part of the city is built on reclaimed wetlands. That is, when the city expanded, they razed the mangrove swamp. They laid land and built other neighborhoods there.
So this part of the city does not sit on very strong rocks and that is why we have more and more subsidence and flooding in the western part of the city.
Also, there is the fact that that area where Surfside, Miami Beach and other communities are located is at a very low elevation and the limestone is very porous.
That means that we cannot use the model of the Netherlands, where they build dikes, because the water can come from below.
It is necessary to design other structures, such as barriers, pumping stations and drainage systems.
What could happen in the coming years with climate change, rising sea levels and the sinking situation in that area?
That is the reason why we did the study, because we are concerned about the city and other communities in Florida and along the Atlantic coast.
Now we face what is called the intermediate situation, in which the sea level is expected to rise at the current rate during the next 20 or 30 years.
In the long term, it depends on how quickly the level rises.
It all depends on how people respond to the call to reduce the amount of carbon emissions.
We have different scenarios on how climate change and the melting coming from the polar regions will impact, but almost all pose a very big threat to Miami Beach as well as to many other communities.
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