Minas Gerais is the Brazilian state with the largest urbanized area on high slopes, that is, built on steep slopes that pose risks to residents. The data was released on Wednesday (4) by MapBiomas, in the Annual Mapping of Urbanized Areas in Brazil.
In the state, where heavy rains left 72 people dead and one missing last week, there are nearly 14,500 hectares of area with people living in risk locations.
Each hectare corresponds to 10,000 square meters, an area larger than a professional soccer field, which has a little more than 7,000 square meters.
The states of Rio de Janeiro, São Paulo, and Santa Catarina also have large urbanized areas on sloped terrain, with more than 8,500 ha; 8,100 ha, and 3,700 ha, respectively.
The municipality most affected by the rains in the Zona da Mata region of Minas Gerais, with 65 deaths, Juiz de Fora is the third Brazilian city with the largest urbanized area on slopes. In 2024, the city had 1,256 hectares built where the slope represents a higher risk of landslides.
The capitals Rio de Janeiro, with 1,700 hectares, and São Paulo, with 1,500 hectares, top the list.
Ever Greater Risk
With data on city occupation over the last 40 years, the study also reveals that the occupation of risk areas grew at a faster pace than urbanization in general.
While urban areas in Brazil grew 2.5 times, the increase in constructions on sloped terrain more than tripled in the same period.
Between 1985 and 2024, the urbanized area in the country grew from 1.8 million hectares (ha) to 4.5 million hectares. This means annual growth equivalent to 70,000 hectares, or the size of a medium-sized city.
Meanwhile, areas built in regions with steep slopes and higher risk of erosion and landslides increased from 14,000 hectares in 1985 to 43,400 ha in 2024.
According to the study coordinator, Mayumi Hirye, the context of climate change and the risks caused by extreme events are factors to be considered in city expansion.
“They affect everyone, but especially impact more dramatically the more sensitive and vulnerable areas, whose occupation has occurred at a faster pace than the overall urbanization rate,” she emphasizes.
Drainage
Proximity to rivers and streams, where the natural drainage of cities occurs, is also considered a factor of greater exposure to flash floods.
In 2024, researchers identified that 1.2 million hectares of urban areas in Brazil present a higher risk of flooding due to this characteristic.
Among the states with the largest urban territory at risk due to proximity to natural drainage areas, Rio de Janeiro led in 2024, with 108,200 hectares in this situation.
The occupation of areas with this characteristic in the Fluminense territory nearly doubled over 40 years.
In Rondônia, construction in areas close to natural drainage more than doubled. In 1985, there were 7,300 hectares of urbanized area with this characteristic, and in 2024, the total reached 18,800 hectares.
According to the MapBiomas environmental engineer, Edmilson Rodrigues, historically, cities were established next to bodies of water, but climate change increases the risk of this type of proximity.
“Given the increase in the number of extreme events and the set of functions performed by floodplain and flood-prone plain areas, it is important to monitor the expansion of urbanized areas on riverbanks, seeking to conserve the environment and the quality of life of the population,” he concludes.
Source: Agência Brasil