Guaíba River overflows in Porto Alegre’s center in third-highest flood since 1941, Brazil

The Guaíba River in Porto Alegre, Brazil, reached a historic water level of 3.01 m (9.8 feet) on the morning of November 20, 2023. This marked the third-highest flood level since 1941, following heavy rainfall across its contributing basins. The rising waters led to the river overflowing its banks at the Central Wharf, a rare occurrence in the city’s recent history. The river is expected to continue rising as the peak flow from the Taquari and Caí rivers arrives.

• The flooding of the Guaíba River and other rivers in Rio Grande do Sul poses a significant challenge to the region. The historical levels of these rivers, combined with adverse weather conditions, suggest that the situation may worsen before it improves. Efforts are ongoing to monitor and manage the flood situation, with a focus on ensuring the safety and well-being of the affected communities.

On the morning of November 20, 2023, Porto Alegre witnessed a historic event as the Guaíba River overflowed at the Central Wharf, reaching a level of 3.01 m (9.8 feet). This significant rise in water level marked it as the third-highest flood since 1941, surpassed only by the floods of September 1967 and two in September 2023, which reached 3.13 m (10.2 feet) and 3.18 m (10.4 feet) respectively​​. The flooding in this area is a rare occurrence, considering that such high water levels at the Central Wharf have only been recorded a few times in the past 80 years.

The Guaíba began to overflow at the Central Wharf, adjacent to the heart of Porto Alegre, shortly before 07:00 LT today. The situation was further compounded as the floodgates of the city’s flood containment system remained open while the river approached the transbordation mark​​.

AGORA | Com mais de três metros, Guaíba segue colocando água para fora no Cais Mauá. 📷 @fernao_berthold pic.twitter.com/UG2bFgwfSa

— MetSul Meteorologia (@metsul) November 20, 2023

🔴 URGENTE | Guaíba sobe rapidamente e está muito perto da cota de transbordamento no Centro de Porto Alegre.

‼️Leia informe atualizado sobre o Guaíba ▶️ https://t.co/KDyHiIeSGn pic.twitter.com/UwcNiS41ou

— MetSul Meteorologia (@metsul) November 20, 2023

AGORA | Com mais de três metros, Guaíba segue colocando água para fora no Cais Mauá. 📷 @fernao_berthold pic.twitter.com/UG2bFgwfSa

— MetSul Meteorologia (@metsul) November 20, 2023

⚠️ Porto Alegre: Catamarã afunda no Guaíba. Rebocador realizando apoio. Não há relato de que estivesse com passageiros. pic.twitter.com/nZTU4m167a

— Fernando Oliveira (@fernao_berthold) November 20, 2023

Porto Alegre: situação dramática no Cais Mauá. pic.twitter.com/1ETmWtA4v6

— Fernando Oliveira (@fernao_berthold) November 20, 2023

The flood situation in Porto Alegre is part of a broader crisis in the state of Rio Grande do Sul, with several rivers experiencing high water levels.

Satellite images taken on November 19, 2023, revealed the extent of flooding across the state. Rivers such as the Caí and Taquari were at some of the highest levels recorded in history. The Taquari River reached 28.94 m (94.9 feet) at the Porto de Estrela, the fourth highest in 150 years and third highest in the last century. The Rio Caí also recorded significant levels, with 9.01 m (29.5 feet) in Montenegro, marking it as the second highest since 1940​​.

Other rivers such as the Jacuí, Sinos, and Gravataí are also facing floods, with the Jacuí expected to rise further between Cachoeira do Sul and Porto Alegre. The Sinos River is anticipated to experience one of its most severe floods in recent history​​. Additionally, the Rio Uruguai is forecasted to rise significantly, with major flooding expected in São Borja, Itaqui, and Uruguaiana. This could lead to one of the largest floods of the Rio Uruguai in western Rio Grande do Sul in decades​​.

The flooding in Porto Alegre and across Rio Grande do Sul is attributed to heavy rainfall in the basins feeding into the Guaíba. Accumulated rainfall in the last week in the Northern part of the state, where these river sources are located, has been substantial. For instance, Cambará do Sul recorded 333 mm (13.1 inches), Serafina Corrêa 328 mm (12.9 inches), and Porto Alegre 205 mm (8.07 inches)of rain​​.

Moreover, the Guaíba River level is expected to continue rising as the peak flow from the Taquari and Caí rivers arrives. An additional concern is the wind pattern, which could potentially exacerbate the situation. Between Wednesday and Saturday, moderate to strong south winds are expected, which could raise the Guaíba River level by an additional 30 to 50 cm (1 – 1.6 feet).

🔴 AGORA | Diretor-geral do @dmaepoa anuncia que comportas do sistema de contenção de cheias de Porto Alegre serão fechadas. Nível do Guaíba está em praticamente três metros, que é a cota de extravasamento no Cais Central. 📷 @fernao_berthold pic.twitter.com/rWgmC9qFZd

— MetSul Meteorologia (@metsul) November 20, 2023

Flooding and landslides caused by heavy rains have claimed at least six lives in recent days across Southern Brazil.

In the state of Santa Catarina, fatalities were reported due to last week’s heavy rains, prompting the governor to declare a state of emergency in 64 towns.

The region has been severely impacted by extreme weather events in recent months, including torrential rains and a cyclone in September that resulted in over 50 deaths.

The International Charter call from CENAD on behalf of the Geological Survey of Brazil has been confirmed, DG ECHO reported.

References:

¹ Guaíba transborda no Centro na terceira maior cheia desde 1941 – MetSul – November 20, 2023

² Satélites registram enchentes no Rio Grande do Sul; veja as imagens – MetSul – November 20, 2023

Featured image credit: NASA Aqua/MODIS, The Watchers. Acquired on November 19, 2023