rain rain

Pico do Corcovado (1.160 m), Serra do Mar State Park, Ubatuba (SP). Photo: Heraldo Campos
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By HERALDO CAMPOS*

The tragedy of São Sebastião and necessary actions to prevent new ones from happening

Exceptional rainfall occurs throughout Earth's geological time. Geological risk is a situation of danger, loss or damage to man and his properties, due to the occurrence of an induced geological process or not. To stay only in São Sebastião, a municipality located on the north coast of São Paulo, which during the 18th and 19th of February 2023 suffered from landslides due to extreme precipitation (more than 600 mm of rainwater in 12 hours) received in its territory, occupied in a disorderly way on the slopes of the Serra do Mar hills and victimizing dozens of people.

What happened in São Sebastião, due to the volume of material involved in the widespread landslides, is roughly reminiscent of what happened in Caraguatatuba in 1967, when on March 17th and 18th of that year it rained more than 500 mm of rain, killing more than 500 people, for a municipality with just over 15 inhabitants at the time.

Deforestation for the implementation of allotments, the waterproofing of the urban plot of streets and pavements, often end up not allowing the infiltration of rainwater into its natural environment, ending up soaking the land and enhancing mass movement, with landslides, blocks of rock and even dragging part of the vegetation by the action of gravity.

The real estate speculation that led to the occupation of land by high-income people in the “nobler parts of the seafront” ended up expelling the low-income population to the slopes, which join the tops to the bottoms of the valleys, more subject to erosion processes, mainly in areas with high slopes that allow an increase in surface runoff. It should be noted that these are the most vulnerable areas, where the significant contingent of people who built most of the high-end condominiums on the coast of São Paulo live. These are the people who continue to support the many “general services” in the region with labor, as well as in bars, snack bars, supermarkets, hotels, inns, among others.

Due to a series of landslides on the slopes of the hills that occurred in the summer of 1989/1990, along the coast of São Paulo, State Decree No. on the slopes of Serra do Mar in the State of São Paulo.

According to an excerpt from that Decree, “The Specific Civil Defense Preventive Plan for Landslides on the Slopes of Serra do Mar has as its main objective to provide the Civil Defenses with instruments of action in order to, in risk situations, reduce the loss of human lives and property materials resulting from landslides and related processes.

The Plan is based on the possibility of becoming measures in advance of the outbreak of landslides, based on the monitoring of the following parameters: (a) rainfall, b) meteorological forecast, (c) field surveys”.[1]

In the same direction as the 1989 Decree, as warned in the 1996 booklet of the Preventive Plan for Civil Defense (PPDC) of the Municipality of Santos “The hills give some signs that the terrain is moving and that landslides may occur. Observe carefully and report any changes to Regional Administration. You could be helping to save many lives” and went on to point out some signs that residents of high-risk areas on hills may notice, such as: “cracks or cracks in the ground; trees, walls and leaning posts; steps or lowering of the ground; new cracks or cracks in the house; muddy waters than usual; cracks or cracks in stones; walls and stuffed walls”.[2]

This important document went on to say “Checking any of these signs, do the following: leave the house immediately with the whole family; go to the nearest school or polyclinic; immediately communicate with the Regional Administration”

These are necessary measures in this type of scenario, which should be associated with warnings to residents with the sounding of sirens by the Civil Defense, anticipating landslides predictable by meteorological models. Another point to be taken forward by the government is the relocation of houses to more stable and safer areas, with due support from urban infrastructure such as, for example, garbage collection, sewage treatment and distribution of treated water. It should also be remembered that under these unstable lands in the municipality of São Sebastião there is a Petrobrás oil pipeline that deserves special attention due to the instability of the land.

To conclude, in this presented context, it can be said that one of the verses of the romantic song “Chove Chuva” by Jorge Ben from the 1960s “Please, bad rain / Don't get wet anymore / My love like that”, does not deal with this “rain”. bad” for the population of São Sebastião, in one of the saddest moments of its history in the region.

* Heraldo Campos, a geologist, is a postdoctoral fellow at the Department of Hydraulics and Sanitation at the School of Engineering of São Carlos-USP.

Notes


[1] State Decree No. 30.860 of 04/12/1989.

[2] Booklet on Integrated Policy for Risk Prevention and Improvement of Quality of Life in Morros de Santos. Published under the coordination of the Morros Regional Administration. City Hall of Santos. 1996.

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