The consequences of debris flows in Brazil: a historical analysis based on recorded events in the last 100 years

Abstract

This study aims at providing an overview of the socioeconomic consequences that debris-flow events have caused in Brazil, positioning the country in the international scenario and identifying areas where targeted actions are necessary. The analysis is conducted by calculating the debris-flow mortality rate (MR) and by using the so-called F-N plots (frequency of events that have caused N or more fatalities vs. the number of fatalities), based on a compilation of debris-flow-related disasters from 1920 to 2021. In total, 45 debris-flow events were documented in the considered period, responsible for 5771 fatalities and more than 5.5 billion USD in economic losses. The Serra do Mar Mountain Range is the main site of reported debris-flow occurrences (64.5%), followed by Serra da Mantiqueira (13.3%), and Serra Geral (13.3%). Southeast Brazil (SEB) is the region most affected by debris-flow events, due to the highest population density and the development of several cities in hilly areas, such as Petrópolis (Rio de Janeiro state) and Cubatão (São Paulo state). The debris-flow MR of SEB is higher than any other region in Brazil, pushing the national debris-flow MR upwards, and the F-N curve of SEB consolidates the region as the one with the highest risk to the phenomenon, indicating a higher probability of fatal events. The F-N plots further show that debris-flow events in Brazil represent a higher societal risk than in countries such as China, Japan and Italy. While there are differences in country size and the scale effect should be considered, these results highlight the urgent need for investments in disaster prevention and preparedness programs.

Identificação de eventos extremos de precipitação e desastres deflagrados por chuvas no município de Petrópolis-RJ

“…This average was exceeded in 2005, 2013 and 2022, with 2022 DH corresponding to 40.64% of the total for the period (Table 2), coinciding with the periods of higher precipitation. According to Cabral et al (2023), the event that occurred in 2011 in the mountainous region of Rio (Petrópolis and Teresópolis) was the second-largest event in number of deaths caused by landslides in the history of Brazil. The monetary values of damage and losses (D&L) caused by flash floods in January 2011 represent 43% of the impact for Petrópolis in the period 2001 -2022.…”

“…In this context, Cabral et al (2023) state that the prospects for the municipality are not promising, considering the discontinuity of disaster prevention programs, such as the case of the alert program, which was not working during the 2022 rain.…”

Impact аssessment of the September 2022 disaster in the area of Karavelovo, Bogdan, and Slatina villages, Karlovo Municipality

“…Over the past few decades, severe rainstorms have caused numerous catastrophic events, such as landslides and debris flows, which have severely damaged local communities and infrastructure all over the world (e.g., Andres, Badoux, 2018;Cabral et al, 2023). These events have also caused a great deal of distress and have become urgent and critical issues for society.…”