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Soft soils and landfills cause areas of Rio de Janeiro to slowly sink, causing cracks and structural damage, especially in the West Zone.
In 2025, a survey published on June 28 in the academic journal Geo UERJ and technical analyses released on June 10 by Diário do Rio drew attention to a little-visible but structurally relevant problem in the city of Rio de Janeiro: parts of the urban soil are undergoing subsidence, a phenomenon also associated with ground settlement, with potential impact on streets, buildings, foundations, and infrastructure. In the West Zone, especially in areas like Rio das Pedras, the problem appears linked to the presence of very soft and highly compressible organic clays, which can lose volume over the years when subjected to the overload of houses, buildings, paved roads, and urban landfills.
These areas are associated with ancient coastal, lagoon, and mangrove environments, where the natural dynamics of the coast favored the deposition of fine sediments and organic matter. The result is a type of soil that does not react immediately to the weight of constructions: it slowly compresses, expels water from internal voids, and can cause gradual ground lowering, cracks, deformations, and differential settlements in structures.
In the case of Rio das Pedras, data cited in the report indicate that some areas recorded an average subsidence of up to 6.3 cm per year between 2014 and 2020, while experts warn that the process requires detailed geotechnical mapping and continuous monitoring to prevent the risk from silently advancing across the city.
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The problem does not arise abruptly, but manifests over time, with progressive deformations that can compromise entire structures.
Areas of Rio de Janeiro sinking: Ground settlement causes cracks, unevenness, and structural deformations
The central phenomenon observed in these regions is called settlement, which occurs when the soil undergoes compression under load. In areas with soft clays, this process is slow and continuous, potentially lasting years or even decades after construction.
In practice, this translates to:
- cracks in walls and floors
- irregular sinking of streets and sidewalks
- tilting of buildings
- deformation of drainage and sewage networks
In neighborhoods like Rio das Pedras and regions near Barra da Tijuca and Jacarepaguá, this type of behavior has already been documented in technical studies and field analyses.
The greater risk lies in differential settlement, when parts of the same structure sink at different speeds, generating internal stresses capable of compromising the stability of the construction.
West Zone concentrates most vulnerable areas due to geological history and urban expansion, and few know about the areas of Rio de Janeiro that are sinking
The West Zone of Rio de Janeiro brings together characteristics that increase its vulnerability to the problem. Historically, much of the region was composed of:
- marshy areas
- mangroves
- sedimentary coastal plains
With urban expansion in recent decades, these areas were landfilled and occupied by residential and commercial constructions and urban infrastructure.
This advance often occurred without the full use of adequate geotechnical solutions for highly compressible soils, which contributed to the intensification of current problems.
Clay consolidation process is slow and practically irreversible
The behavior of soft clays is well known in geotechnical engineering. When subjected to load, these layers undergo a process called primary consolidation, in which the water present in the soil pores is slowly expelled, reducing the total volume of the layer.
This process can take years, depending on the layer thickness and material characteristics. Once initiated, consolidation cannot be reversed, meaning that subsidence tends to continue until the soil reaches a new state of equilibrium.
Engineering solutions exist, but cost limits large-scale application
Civil engineering has consolidated techniques to deal with soft soils. Among the main solutions are:
- deep foundations with piles
- soil pre-loading before construction
- vertical drainage to accelerate consolidation
- soil improvement with stabilizing materials
These techniques allow for safe construction even on unfavorable terrain. However, all involve high costs and greater technical complexity.
In high-end projects, these solutions are frequently applied, but in areas of popular occupation or accelerated urban growth, they are often reduced or omitted.
Urban infrastructure also suffers from soil deformations
The impact of settlement is not limited to buildings. Urban infrastructure networks installed on these terrains also undergo deformations over time. Pipelines can rupture or lose alignment, drainage systems can be compromised, and paved roads begin to show undulations and depressions.
These problems generate continuous maintenance costs and reduce the lifespan of urban structures.
The city begins to live with a cycle of gradual degradation, where repairs are made without eliminating the structural cause of the problem.
Urban expansion over unstable areas amplifies the long-term challenge
The city’s growth towards areas originally unsuitable for urbanization intensifies the scenario. With increased construction density, the load on the soil grows, accelerating the consolidation process and amplifying the effects of settlement.
Furthermore, neighboring constructions can influence soil behavior, creating interactions that make problem control difficult.
The challenge ceases to be isolated and becomes urban, involving territorial planning, engineering, and public policies.
Phenomenon is not exclusive to Rio, but gains scale due to occupation patterns
Similar problems occur in various coastal cities around the world, especially in areas built on soft soils or landfills.
However, in the case of Rio de Janeiro, the combination of unfavorable geology and accelerated urban expansion makes the phenomenon more visible and relevant.
The way the city has grown over the last decades has contributed to increasing exposure to geotechnical risk.
Monitoring and planning are fundamental to reducing future impacts
Identifying and monitoring these areas are essential steps to reduce damage. Geotechnical surveys, risk mapping, and deformation monitoring can guide more effective interventions.
Furthermore, urban planning can prevent the occupation of more critical areas or require adequate technical solutions before construction. Without this type of approach, the problem tends to perpetuate and expand with the city’s growth.
Given this scenario, is Rio de Janeiro prepared to deal with the advance of urban subsidence?
The progressive subsidence of built areas on soft soils reveals a structural fragility that develops slowly, but with cumulative impact.
Streets that deform, structures that give way, and infrastructure that deteriorates are visible signs of a process that occurs underground.
The question that remains is direct: are urban planning and engineering applied today sufficient to contain this advance, or does the problem tend to grow as the city continues to expand over geologically unstable terrains?
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