Morphometric parameters and debris flow: susceptibility and magnitude index to watersheds in Serra do Mar

Author(s)

Vivian Cristina Dias

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH/SBD)
• Defense date: 2021-11-10

Examining board members

Bianca Carvalho Vieira; Maria Carolina Villaça Gomes; Fábio Augusto Gomes Vieira Reis; Claudinei Taborda da Silveira

• Advisor: Bianca Carvalho Vieira

Abstract

Debris flows are one of the most destructive types of mass movement due to the transport potential in long distances of large boulders and other materials. Several conditioning factors are related to the occurrence of debris flows, highlighting the watershed\'s dynamics and their morphometric characteristics. In Brazil, the studies about debris flow are important due to the recurrence of the process and the high number of deaths and homeless, and economic losses. As explained above, the main goal of this research was the evaluation and validation of the index of magnitude potential and susceptibility to the occurrence of debris flow in watersheds in Brazil. To achieve this goal, it was established and accomplished the following methodological steps: (a) the evaluation of debris-flows occurrence in different areas; (b) the evaluation of main fan morphology characteristics; and (c) the evaluation of the relation between morphometric characteristics and magnitude in the definition of the susceptibility of the watersheds to debris flows The research is based in the hypothesis that the index of magnitude potential and susceptibility to the occurrence of debris flow proposed from the evaluation of debris-flow occurrence in Caraguatatuba/SP can be applied in different areas all over the country and can be an accessible alternative to the governments and managers to the determination of susceptible areas. The results of the evaluation of the past occurrences indicated the entrainment process as a fundamental part of the production of sediments and in the total volume produced by a debris flow. Furthermore, fan morphology in the different areas was similar, which can indicate a pattern in the occurrence of debris flows in Brazil. The analysis of the morphometric characteristics indicated parameters that could have influenced in the differences observed between the watersheds with and without recent occurrences of debris flows, but also in the similarities related to the magnitude of the processes in the affected areas. Lastly, the magnitude and susceptibility index created from the Caraguatatuba results did not present a good classification of the watersheds. As a result. As a result, the index was recalibrated and modified considering the new results obtained in this research. This research contributes to a better understanding of the debris-flow dynamics related to the geomorphology and future prevention actions to natural hazards in the country. (AU)

• FAPESP's process: 18/08402-4 - Magnitude potential and susceptibility of watersheds to the occurrence of debris flow: evaluation of proposal of national index
• Grantee: Vivian Cristina Dias
• Support Opportunities: Scholarships in Brazil - Doctorate