GSI Seminar: Hydrogeological disasters in the city of São Sebastião in the northern coast of the state of São Paulo in February 2023

Abstract

On February 18th-19th, 2023, heavy rainfall affected the municipality of São Sebastião, on the coastal region of the state of São Paulo in southeast Brazil. Extreme rainfall of about 680 mm in less than 24 hours triggered multiple fatal and flash floods landslides in the city. This is perhaps the highest rainfall measured in all of Brazil in modern history. Therefore, the water-saturated soil led to deadly floods, debris flow, and landslides resulting in 65 casualties and damages. The meteorological situation was associated with a cold front crossing over a warmer subtropical South Atlantic off the coast of São Paulo. This was in addition to the orographic effect the Serra do Mar Mountain, causing an extreme and historic heavy precipitation event. This front remained stationary over the northern coast of  areas of the State of São Paulo, and it rained continuously from around 19:00 on February 18th  to 11:00 hours on February 19th. CEMADEN identified high and very high hydrological and geological risks, and alerts for those risks were submitted to emergency services at the municipal level with few days in advance.  However, it looks like São Sebastião’s population either was not warned of the upcoming disaster or if warned the population did not take any action because did not believe in the possibility of a disaster.  This shows a need to improve perception of the imminence of a disaster. So, multi-hazard early warning systems are vital for adaptation and risk reduction in areas susceptible to disasters.  Public policies must be implemented so lives can be saved.

Biography

José Antonio Marengo Orsini is R&D Director at National Centre for Monitoring and Early Warning of Natural Disaster (CEMADEN) in Brazil and a professor at the Post-Graduate Program at the National Institute for Space Research (INPE) and São Paulo State University (UNESP). He is an internationally-recognised researcher in Climatology, climate modelling, climate change, hydrology and natural disasters and disaster risk reduction, with around 200 scientific publications. He has served as a Lead Author with the Intergovernmental Panel on Climate Change (IPCC) since the mid-1990s and is a Fellow of the World Academy of Sciences.

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