The risks of the ground where Miami Beach was built, the area near the building that collapsed

(CNN Spanish) – Miami, with its idyllic turquoise waters attracting some 12 million visitors each year, is «the most vulnerable coastal city in the world»As far as climate change is concerned.

That was the stark warning from a study on the impacts of climate change in Florida, published by the nonpartisan think tank. Resources for the Future (RFF), in February 2020. In it he warns that “climate change is affecting Florida today, and those effects will become more significant in the years to come.”

And, due to climate change, Florida is in check “hundreds of billions of dollars in assets under attack from winds, storm surge, coastal flooding and rising sea levels,” the report says.

How was Miami Beach built?

Miami Beach, a city about 15 kilometers from Miami, is located on an island between Biscayne Bay and the Atlantic Ocean, east of the capital of Florida.

Until 1912, it was home to mangroves where avocado plantations were more successful than coconut plantations. according to the encyclopedia Brittanica. Construction of what is now known as a luxury vacation area began with real estate pioneers John S. Collins, Carl Fisher, and John and James Lummus, who began real estate development early in the last century and by 1915. it was known as Ocean Beach, to later change its name to Miami Beach.

Miami Beach, the area near the 12-story building that collapsed at dawn on June 24 – and that left at least eleven people dead and more than 150 missing – is a city of about 92,000 inhabitants. It is located largely on land less than a meter “above the high tide mark” and “could be permanently submerged by the end of the century,” the RFF report warns.

South Florida – where Miami and Miami Beach are – is built on porous limestone rock. And as the water level rises, the space between the ground and the water decreases, something that could cause flooding without even a drop of water falling.

“There are places where, in the past, we built levees and canals to keep the ocean out while the land sank,” Harold Wanless, a professor at the University of Miami, previously told CNN.

And that sinking could be a key to understanding what happened to the Florida Surfside condo tower that collapsed.

According to a study published last year, the collapsed building, unlike other buildings around it, had sunk at a rate of approximately 2 millimeters per year between 1993 and 1999. The research focused on the effects of sinking, sinking gradual or collapse of the land, on the dangers of coastal flooding. It did not track the condition of the building, so it is unclear whether the structure continued to sink at the rate described in the study.

Shimon Wdowinski, a co-author of the study and a professor at Florida International University’s Institute of the Environment, cautioned that his research did not provide irrefutable proof. He also assured that this is not something general in the buildings of the sector.

“Other buildings were not moved in that eastern part of the city,” Wdowinski told CNN. “If it’s a forerunner, it’s only unique to that building.”

When asked directly whether the subsidence could have been a contributing factor to the building’s collapse, Wdowinski said additional information was needed before rendering a judgment.

“If everything is moving down to the same level, then not that much,” but “if one part of the building is moving relative to the other, that could cause some tension and cracks,” he told CNN. “Maybe some sinking can start the process.”

Experts are still conducting investigations that could take months, if not years, into what happened in Surfside, Florida.

Miami and the sea

Miami is one of the cities most at risk of rising sea levels, above others such as Guangzhou, New York; Kolkata, Shanghai, Mumbai, Taijin and Tokyo, according to the RFF report.

And Wdowinski’s study establishes that the Atlantic Coast of the United States (where Miami is located) is one of the areas most vulnerable to rising sea levels due to “its low elevation, high concentration of populations and its economic importance.”

The mid-tide near Miami Beach, that small island municipality off the coast of the megacity of South Florida, has risen about 4 inches since 1996, reported CNN’s John D. Sutter previously. And there floods are common.

But Miami Beach is buying time with millionaire investments: the authorities promised an investment of US $ 400 million in recent years to try to mitigate the disaster, including installing water pumps and raising street levels.

But on the other hand there is the natural exposure of buildings to the sea, something that can also help in their degradation.

“It is inevitable that over the years the natural course of the elements will be a degradation and in the case of structures that carry steel this degradation is faster,” Federico Nuñez, director of the Master of Civil Engineering from the Javeriana University in Bogotá, Colombia. “Steel is made of iron, but iron comes into contact with a saline medium, so it causes the numbers of oxidation and corrosion to increase a lot faster.”

In addition to the structural problems and the “40 years of exposure to salt, water and salty air”, The collapse may have been influenced by vibrations from construction work, heavy equipment on the roof, and water damage from the building’s pool. , according to Mehrdad Sasani, professor of civil and environmental engineering at Northeastern University.

But, with the warnings of the climate change studies, Núñez does not believe that the solution is to stop building the coasts in the future, because precisely because they are facing the sea, coastal cities are built for economic reasons.

“So, even though the water level rises, one could not limit the structural development for tourism projects close to the coast. This is a matter of planning and rigor, ”said Núñez.

Studies advance to establish what happened in Surfside

A team of six federal officials from the National Institute of Standards and Technology (NIST) – comprised of scientists, structural engineers, and a geotechnical engineer – is conducting a preliminary investigation of the collapsed building’s materials, history, and applicable building codes. at the time the condo was built, the terrain surrounding the building and many other factors, according to an agency official.

As researchers converge on the scene, questions continue to arise about the building’s structural integrity. A 2018 report from an engineering company showed severe structural damage to the concrete slab below the pool deck and “cracks and chips” located in the parking lot.

Spalling is a term used to describe areas of concrete that have cracked or crumbled.

Donna DiMaggio Berger, an attorney for the condo’s board, told CNN’s Chris Cuomo on Monday that she didn’t think the building was in disrepair before its collapse.

“We have months and years to investigate what happened, and we will. The board is already in the process of hiring an engineer to also try to find out what happened, and they will be evaluating who is responsible.

The condo owners faced appraisals for $ 15 million in repairs to the building, and payments were scheduled to begin July 1.

The association approved the assessment in April to complete the repairs required under the county’s 40-year recertification process, according to documents obtained by CNN.

– With information from Kobi Karp, John D. Sutter, Gregory Krieg, Curt Devine from CNN and Natali Monterrosa and Uriel Blanco from CNN en Español.