Unprecedented April-May 2024 rainfall in South Brazil sets new record
Walter Collischonn, João Paulo Lyra Fialho Brêda, Sly Wongchuig, Anderson Ruhoff, Rodrigo Cauduro Dias de Paiva, Fernando Mainardi Fan, Rafael Cabeleira de Coronel Machado Filho, Nicole Ramalho
Abstract
ABSTRACT This technical note presents a comparative analysis between the heavy rainfall that occurred in Rio Grande do Sul, between April and May 2024, with the heaviest rainfall events ever observed in Brazil, between 1961 and 2022. The comparative analysis was performed using the Depth Area Duration technique, suitable for the analysis of heavy rainfall on a large spatial and temporal scale. We concluded that following our analysis, the rainfall that occurred in Rio Grande do Sul largely exceeded the most intense large-scale precipitation events historically observed in Brazil, from 1961 to 2022, at least for areas from 2,000 to 100,000 km2 and rainfall durations of 3 to 14 days. In some cases (3-day rainfall in 10,000 km2) the 2024 rainfall was 47% higher than the previous record rainfall. Considering that we cannot rule out that similar events occur in any other basin, at least in South Brazil, it may be necessary to review the original design and operation rules of high-risk hydraulic structures and flood defense systems throughout the Southern region of the country.