Barriers against sea damage will be expanded on the coast of São Paulo

Anyone passing by the Santos Aquarium, closed for renovation since June 2025, may not realize that right next door, beneath the waters of the Ponta da Praia neighborhood, another project is quietly at work without interruption: submerged geotubes providing coastal protection. The initiative is set to be expanded to neighboring areas in the city on the São Paulo coastline.

These structures create a shallow stretch where waves break early and lose their force before reaching the sand. This is particularly useful during periods of rougher seas (storm surges), when water can overtop seawalls and flood the road surface.

"We used a high-resistance geofabric designed to withstand friction from the sea. It is a material that can handle significant stress," explains researcher Tiago Zenker Gireli, 41. "We fill these bags with sand from the beach itself. They end up looking like pillows. We arrange the elements side by side to form the barrier we need."

This "submerged laboratory" works against erosive processes in the sand at a time of increasingly intense and frequent weather events. "The beaches keep getting shorter and disappearing," the researcher said.

The pilot project, spanning just over 500 metres, was installed at Ponta da Praia (near channel 6 of the waterfront) following a contract signed in 2018 between Unicamp (University of Campinas), where Gireli is a professor, and the Santos City Hall.

The funding for this initial phase, around R$ 3 million, came from environmental compensation payments from the port of Santos and was also used to improve nautical signage.

The expansion to a 1.4-kilometre barrier, between channels 4 and 6, will be funded by APS (Santos Port Authority), a public company linked to the Ministry of Ports and Airports that manages the largest port in Latin America.

"Compared to similar initiatives we have researched, we believe this to be an unprecedented project in Brazil," says Gireli, coordinator of the pilot project and faculty member in the Department of Water Resources at Unicamp's School of Civil Engineering, Architecture and Urban Planning, where co-author Patrícia Dalsoglio Garcia also teaches.

According to Gireli, the new phase of the project "puts forward a definitive solution."

Regular beachgoers say they have already noticed a difference. "I can see that this project has been holding back the swell here, especially when storm surges come in," says retired Ponta da Praia regular Crisvaldo Lino, 55.

"I show my students the erosion on the rocks caused by wave action and they are amazed," says his wife, Rosemeire Ratzka Guedes, 60, a Hawaiian canoe instructor. "We have had storm surges bad enough to damage cars parked nearby, and seawater still floods the car parks."

Santos City Hall says it continues to support and monitor the development of each phase. "The L-shaped submerged barrier stretching more than 500 metres, between the Municipal Aquarium and the Edgard Perdigão Bridge, is part of this pioneering pilot project in the country to contain erosion and retain sand on site."

Next steps

The Santos Port Authority confirms that the intervention will now be funded and carried out by the agency itself, complementing the project undertaken by Unicamp and the city hall. The figures were not disclosed.

APS states that the new phase will include, in addition to reinforcement of the existing structure, modules in the neighbouring districts of Aparecida and Embaré to increase sediment retention capacity and reduce the incoming wave energy.

"The pilot project currently in operation has demonstrated positive technical results," states the APS. The agency notes that the planned expansion will use the same construction concept employed in the initial project.

The APS also highlights that the installation of geotubes (or "geobags") offers advantages when compared to traditional solutions. "The structures have less visual impact on the landscape and allow for future adaptations. By remaining submerged, they preserve the recreational use of the beaches and significantly reduce the visual impacts on the waterfront."

The implementation of the expansion project is in the environmental licensing study phase. Without citing any deadlines, Cetesb (the Environmental Company of the State of São Paulo) states that it is currently analyzing "the inquiry regarding the need for environmental licensing for the installation of new submerged breakwaters intended for coastal erosion control."