Heavy rains and hydrogeological disasters on February 18th–19th, 2023, in the city of São Sebastião, São Paulo, Brazil: from meteorological causes to early warnings

Abstract

This study provides a thorough analysis of the landslides that occurred in the city of São Sebastião, on the northern coast of São Paulo state, Brazil, in February 18th–19th, 2023. The meteorological condition during this event was characterized by a cold front crossing over a warmer-than-normal subtropical South Atlantic, off the coast of São Paulo. Combined with the orographic effect of the Serra do Mar Mountain, the front remained stationary over the northern coastal areas of the state of São Paulo, causing an extreme and historic heavy precipitation event. An unprecedented volume of rain, amounting to 683 mm in less than 15 h, triggered landslides that generated 65 casualties and damages. Although alerts were clearly issued in advance, response among the communities was minimal, indicating the ineffectiveness of current early warning system in place. This calls for improved public policies, communication and the possible adoption of multi-hazard early warning systems to reduce risk in vulnerable areas.