Preprints
https://doi.org/10.5194/nhess-2022-163
https://doi.org/10.5194/nhess-2022-163
 
10 Jun 2022
10 Jun 2022
Status: this preprint is currently under review for the journal NHESS.

Deadly disasters in Southeastern South America: Flash floods and landslides of February 2022 in Petrópolis, Rio de Janeiro

Enner Alcântara1, José A. Marengo1,2, José Mantovani1, Luciana Londe1,2, Rachel Lau Yu San3, Edward Park3, Yunung Nina Lin4, Tatiana Mendes1,5, Ana Paula Cunha1,2, Luana Pampuch1,5, Marcelo Seluchi2, Silvio Simões1, Luz Adriana Cuartas1,2, Klécia Massi1,5, Regina Alvalá1,2, Osvaldo Moraes1,2, Carlos Souza Filho6, Rodolfo Mendes1,2, and Carlos Nobre1,7 Enner Alcântara et al.
  • 1Graduate Program in Natural Disasters, Unesp/Cemaden, São José dos Campos, Brazil
  • 2National Center for Monitoring and Early Warning of Natural Disasters (Cemaden), São José dos Campos, Brazil
  • 3National Institute of Education, Earth Observatory of Singapore and Asian School of the Environment, Nanyang Technological University (NTU), Singapore
  • 4Institute of Earth Sciences, Academia Sinica, Taiwan
  • 5Institute of Science and Technology, São Paulo State University (Unesp), Department of Environmental Engineering, São José dos Campos, Brazil
  • 6University of Campinas, Institute of Geosciences (IG/Unicamp), Brazil
  • 7Institute of Advanced Studies, University of São Paulo (IEA/USP), São Paulo, Brazil

Abstract. On February 15, 2022, the city of Petrópolis in Rio de Janeiro, Brazil, received an unusually high volume of rain within three hours (258 mm). It resulted in flash floods and subsequent landslides that caused 231 fatalities, the deadliest landslide disaster recorded in Petrópolis. In this paper, we analyzed the root cause and the key triggering factors of this landslide disaster by assessing the spatial relationship of landslide occurrence with various environmental factors. Rainfall data were retrieved from 1977 to 2022, while other remote sensing data from 1985 to 2020, were utilized to map the landslide scars, soil moisture, terrain attributes, line-of-sight displacement (land surface deformation), and urban sprawling .. to. The results showed that the average rainfall for February 2022 was 200 mm, the heaviest recorded in Petrópolis since 1932. From the rainfall spatial distribution, heavy rainfall was also recorded mostly in regions where the landslide occurred. As for terrain, 23 % of slopes between 45–60° had landslide occurrences and east-facing slopes appeared to be the most conducive for landslides as they recorded landslide occurrences of about 9 to 11 %. Regarding the soil moisture, higher variability was found in the lower altitude (842 m) where the residential area is concentrated. From our land deformation assessment, the area is geologically stable, and the landslide occurred only in the thin layer at the surface of the 1,700 buildings found in the region of interest, 1,021 are on the slope between 20 to 45° and about 60 houses were directly affected by the landslides. As such, we conclude that the heavy rainfall was not the only cause responsible for the catastrophic event of February 15, 2022; a combination of unplanned urban growth on slopes between 45–60°, removal of vegetation, and the absence of inspection were also significant elements of this natural disaster.

Enner Alcântara et al.

Status: open (until 22 Jul 2022)

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Enner Alcântara et al.

Enner Alcântara et al.

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Short summary
The municipality of Petrópolis (approximately 305,687 inhabitants) is nestled in the mountains 68 km outside the city of Rio de Janeiro. On February 15, 2022, the city of Petrópolis in Rio de Janeiro, Brazil, received an unusually high volume of rain within three hours (258 mm). It resulted in flash floods and subsequent landslides that caused 231 fatalities, the deadliest landslide disaster recorded in Petrópolis. This work showed how the disaster was triggered.
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