23 February 2023
Vila Sahy, São Paulo: extreme rainfall in Brazil has triggered multiple fatal landslides
On 19 February 2023, heavy rainfall impacted São Paulo state in Brazil, triggering landslides and floods. At least 48 people have been killed with a further 38 people reported to be missing. The rainfall was centred on the São Sebastiao, in which 47 fatalities have been reported. The Brazil news agency G1 has a very good drone video of the impact of the landslides in Vila Sahy, collected by Andre Bastos – it is well worth a watch. G1 reports that 34 of the victims died at Vila Sahy, which appears to have been the worst affected location. This still is from that video:-
Meanwhile, Folha de Da São Paolo has this image (behind a paywall) of the site from a different angle:-
Vila Sahy is located at [-23.766, -45.690]. This is a Google Earth image of the site:-
The town has built up on an area of level ground that is probably formed primarily from colluvium from previous slope failures from the adjacent slopes. The houses push right up to the foot of the slopes, which (judging by the images above) appear to be formed from deeply weathered (residual) soils. Instability on these slopes is likely in exceptional rainfall events, so tragically these houses were extremely exposed to the hazard.
On Twitter, Raphael Rocha (@raphaeldeque), a Brazilian meteorologist, has an excellent thread highlighting the impacts of the rainfall:-
First assessment of @DisastersChart activation #803 on recent floods and landslides in Brazil. Events triggered by heavy rains above 600 mm in 24h on northern São Paulo coast.
46 fatalities, 49 missing, and 2500 displaced. Updates expected. pic.twitter.com/P1AMkGGfjG
— Raphael Rocha (@raphaeldeque) February 22, 2023
Raphael highlights that 600 mm of rainfall fell in just 12 hours, including peak rainfall intensities of 140 mmm per hours. This is an astonishing amount of rainfall.
Heavy rainfall is continuing to occur in Brazil at the time of writing, and there are warnings of further landslides. On 22 February 2023, a landslide was triggered in Rio Natal in São Bento do Sul, Santa Catarina, derailing a train. G1 has images of the aftermath:-
This recent set of events is causing a great deal of reflection about landslide risk in Brazil. Jornal Extra reports that there are 13,542 sites known to be at risk of landslides, flooding, runoff and erosion. About 4 million people are believed to live in these areas. As short duration rainfall intensities and totals continue to rise, driven at least in part by global heating, it is inevitable that I will be writing about tragedies such as these in Brazil in the future.