Debris-flow hazards mitigation: mechanics, monitoring, modeling and assessment (book chapter)


Morphology characteristics of debris-flow deposits are a fundamental part of the filed study of the process. The deposits show aspects related to flow dynamics, which reflects its main mechanics and enables the correct identification of process. Occurrences of debris flows are quite common in Brazil, especially in the Serra do Mar region, located at the southern/southeastern coast of the country. Geologic al and geomorphological characteristics and high rainfall indexes contribute to high susceptibility of the process in the region. In one of those occurrences, in the summer of 1967, the city of Caraguatatuba was intensely affected by high rainfall far above the average, with maximum values in between the 17th and 18th of March (586mm/48h), which triggered landslides and debris flows that destroyed the city. In this way, the goal of this research was the morphological characterization and identification of debris-flow deposits from the 1967 event in Caraguatatuba, Serra do Mar/Brazil. To achieve this goal, the following steps were made: a) selection of watersheds hit by debris flows; b) mapping of the debris-flows deposits in field surveys; and c) identification of morphological characteristics of deposits, applying field records. The results showed that the deposits mapped present common characteristics described in literature as typical of debris flows, highlighting the presence of inverse grading, lateral levees and large boulders. The watershed showed differences related to morphology types of deposits, indicating the influence of its characteristics in deposition. Those results contribute to the study of debris flow, mostly to identification of susceptible areas but also to mitigation actions promoted by the government, aiming to improve land use planning, avoiding occupation of those areas by population.

DIAS, Vivian Cristina; MARTINS, Tiago Damas; GRAMANI, Marcelo Fischer; COELHO, Rebeca Durço; DIAS, Helen Cristina; VIEIRA, Bianca Carvalho. The morphology of debris-flow deposits from a 1967 event in Caraguatatuba, Serra do Mar, Brazil. In: KEAN, Jason W.; COE, Jeffrrey, SANTI, Paul M.; GUILLEN, Becca K. Debris-flow hazards mitigation: mechanics, monitoring, modeling and assessment. Colorado: Association of Environmental Engineering Geologists, 2019. p.645-652 (AEG Special Publication 28) (Trabalho apresentado no INTERNATIONAL CONFERENCE ON DRIVE-FLOW HAZARDS MITIGATION, 7., 2019, Golden, Colorado)  

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