Minas Gerais is the Brazilian state with the largest urbanized area on steep slopes, that is, built on steep hills 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 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 that of 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 sloping 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 greater risk of landslides.
The capitals Rio de Janeiro, with 1,700 hectares, and São Paulo, with 1,500 hectares, lead the list.
Ever-Increasing 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 sloping 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 an 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 impact in a more dramatic way especially the most sensitive and vulnerable areas, whose occupation occurred at a faster pace than the general 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 sudden 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 state of Rio de Janeiro nearly doubled in 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 MapBiomas environmental engineer Edmilson Rodrigues, historically, cities were established close to bodies of water, but climate change increases the risk of this type of proximity.
“Given the increase in extreme events and the range of functions performed by floodplains and flood-prone areas, it is important to monitor the expansion of urbanized areas on river margins, aiming at environmental conservation and the quality of life of the population,” he concludes.
Source: Agência Brasil