61% of cities in Rio Grande do Sul were hit by climate events in the last 2 months, says study

Almost two-thirds of the municipalities in Rio Grande do Sul were affected, to a greater or lesser extent, by extreme events in the last two months, according to a technical note produced by MapBiomas.

The mapping of affected areas was prepared with the analysis of satellite images, obtained by optical and radar sensors, in a period before and after heavy rains, resulting in the observation of 61% of affected cities.

In total, the area affected by disasters — such as landslides, floods, floods and floods — in the last two months was equivalent to 5.6% (15,778 km²) of the state’s 281,748 km².

In total, 298 municipalities had at least 1% of areas affected by flooding. Of these, 73 had more than 10% and 34 had more than 20%.

The cities of Canoas and Nova Santa Rita had more than half of the territories affected: 50.1% and 52.5%, respectively.

According to the note, the areas that are used for agricultural production were the most affected, with more than one million hectares occupied by these activities in the state.

Urban areas

Of the 497 municipalities in Rio Grande do Sul, 234 had their urban areas affected. The most affected were:

• Eldorado do Sul (66%)
• Mampituba: (49.5%)
• Canoes (42.4%).

In total, 5% of urban areas in the state were affected.

Rains

According to the Mapbiomas technical note, weather events such as windstorms and intense rains are more frequent in Rio Grande do Sul during the spring and autumn seasons.

The state also suffers from the influence of the El Niño and La Ninã phenomena, which cause instability in the climate.

In La Ninã years, there may be a drop in rainfall and an increase in droughts.

During the El Niño season, rainfall tends to increase, with the equivalent of the monthly average being able to rain in a single day.

In addition to this year’s tragedy, the state has also experienced three severe storm events in 2023:

• June : In the Vale do Rio dos Sinos and the North Coast
• September : Taquari-Antas River Valley
• November : Vale do Taquari-Antas e Caí.

The National Institute of Meteorology (INMET) for the periods 1961-1990 and 1991-2020 confirm that practically all regions of the state have already shown changes, some of them with up to 300 mm increase in annual precipitation between the two periods.

The rains of the last two months were extreme in both volume and intensity. Records from the National Water Agency (ANA), National Center for Natural Disaster Monitoring and Alerts (CEMADEN) and the National Institute of Meteorology (INMET) indicate that they exceeded 500 mm, in two weeks, in a large part of the state. In some places, they totaled more than 1000 mm, which caused flooding and a rapid rise in river levels.

See the full study here.

*Under the supervision of Bruno Laforé