The institute identified a high risk in 161 homes in São Sebastião four years ago.
The amount of rain recorded this week was not expected.
Brazil Agency - A report presented in December 2018 by the Institute for Technological Research (IPT), linked to the Secretariat of Economic Development of the State of São Paulo, showed that there were 161 homes in São Sebastião in areas at high risk of landslides. The document also indicated that 2.043 homes were in areas of medium or low risk of landslides in the municipality.
The IPT document did not list any construction in the Barra do Sahy area, on the North coast, one of the places most affected by the storms that occurred last Sunday (19), in a situation of high or very high risk. This shows, according to the technical director of IPT, Fabrício Mirandola, that there may have been an expansion of irregular occupation since the publication of the report. He also highlights that, according to the residents' account, the victims were hit by the mud when they were leaving their homes.
“Some of the people who were affected were no longer inside their homes; they were in the streets and alleys, leaving, fleeing their homes. When we have this process of soil liquefaction, this material tends to follow the path of the streets, because the street normally follows the natural path of the water,” he said.
Most frequent events
The director further notes that the 2018 report was based on historical average rainfall data for the area and did not foresee the atypical rainfall that hit the region last Sunday. However, according to him, the recent event may indicate a new trend.
“And then, less than 10 years later, we end up having an event that is almost five times larger than this one [from 2014]. We are really seeing changes in the climate,” he highlighted. “This may indicate, we can't say for sure, but from what we've seen in the historical data, that extreme events like this will become more frequent, and we need to be prepared,” he added.
He explains that the report refers to a storm that occurred in the region in 2014, which accumulated about 180mm of rain. According to the model used in the document, the institute predicted that a new rainfall of that magnitude could only occur again in 60 years, a prediction technically called the return period.
natural process
According to Fábio Augusto Reis, a professor at the São Paulo State University (Unesp) in Rio Claro and director of the Brazilian Federation of Geologists, the event that occurred on the North coast is a natural process for the region and is expected to continue in the future.
“Other events have occurred before, not with this magnitude, but extreme events in the history of Brazil, in the Serra do Mar. This will continue to happen. Other extreme examples will occur; this is part of the natural process, and the Serra do Mar is a mountain range that has always had landslides and slippage processes, and will continue to have them,” he said.
He cites, as an example, the series of landslides that occurred in 1967 in the municipality of Caraguatatuba, also on the North coast, in which about 450 people died. “The 67 event was much worse. But at that time, there were 15 people living in Caraguatatuba. If that same event had occurred today, we would be talking about thousands of people dead.”
"So that's what we have to separate: the natural event will continue. Now, the big problem lies in the occupation, in the disorderly occupation that occurs in these cities," he added.
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