Abstract:
The widespread occurrence of Granite Massif landscapes in the Serra do Mar Range south-shoutheast Brazil, is also connected with high incidence of debris-flow events. In recent years, the debris-flowevents in Serra do Mar Rane have caudes many deaths and grest infraestructure losses. These events occur in high gradiente regohith. These rocks, quite abundant alog the mountain chain, are resistant to weathering, and present large vertical gradients. In addition, they generate porous and cohesive regoliths, which support infiltration to the rain water. When saturated, these regoliths can generate shallow landslides, which can liquety and flow along channels, depositing this material in colluvial fans in piedmont areas. From this point of view, we analysed two watersheds in a granitic terrain, both of similar size and that recently suffered catastrophic events of debris-flows I) the Guarda-Mão creek watershed in Itaoca region, which had an intense meteorological event in January 2014, 2) the Gicangete creek watershed, in Serra da Prata, which suffered an event with nucleation of debris-flows in March 2011. Both basins present themselves a thin regolith and rock outcrops in higher area, grading to thicker regoliths and colluvim deposits in the foothills, where the gravels are deposited in the colluvionar fan. Both basins have soil densites (ys) between 24 and 27 g/cm³, reflecting the presence of primary (quartz, feldspar) and secondary minerals (illite, kaolinite, montamonillonite and airon oxides). Both materials are porous (32% to 44%), with plasticity indices (PI) betwwe 1% and 17%. Most materials have low plasticy, although the Gigante creek watershed is even lower, between 1 and 5%. The analysed watershed are typical of granitoid terrains in Serra do Mar Range, and present great similarity. Further studies shoud consider the morphometric characteristics of these basins, the mechanisms of rupture and the regoliths liquefaction processes, besides modelling the deposition in fan areas. This understanding couk brimgimprovements to disaster risk management strategies throughout in the Serra do Mar region.
Reference:
PICANÇO, Jefferson; VIEIRA, Bianca Carvalho; MARTINS, Tiago Damas; GRAMANI, Marcelo Fischer; FACCURI, Gabriel; SILVA, Marcio. Debris-flow occurrence in granite landscape in south-southeast 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)
The widespread occurrence of Granite Massif landscapes in the Serra do Mar Range south-shoutheast Brazil, is also connected with high incidence of debris-flow events. In recent years, the debris-flowevents in Serra do Mar Rane have caudes many deaths and grest infraestructure losses. These events occur in high gradiente regohith. These rocks, quite abundant alog the mountain chain, are resistant to weathering, and present large vertical gradients. In addition, they generate porous and cohesive regoliths, which support infiltration to the rain water. When saturated, these regoliths can generate shallow landslides, which can liquety and flow along channels, depositing this material in colluvial fans in piedmont areas. From this point of view, we analysed two watersheds in a granitic terrain, both of similar size and that recently suffered catastrophic events of debris-flows I) the Guarda-Mão creek watershed in Itaoca region, which had an intense meteorological event in January 2014, 2) the Gicangete creek watershed, in Serra da Prata, which suffered an event with nucleation of debris-flows in March 2011. Both basins present themselves a thin regolith and rock outcrops in higher area, grading to thicker regoliths and colluvim deposits in the foothills, where the gravels are deposited in the colluvionar fan. Both basins have soil densites (ys) between 24 and 27 g/cm³, reflecting the presence of primary (quartz, feldspar) and secondary minerals (illite, kaolinite, montamonillonite and airon oxides). Both materials are porous (32% to 44%), with plasticity indices (PI) betwwe 1% and 17%. Most materials have low plasticy, although the Gigante creek watershed is even lower, between 1 and 5%. The analysed watershed are typical of granitoid terrains in Serra do Mar Range, and present great similarity. Further studies shoud consider the morphometric characteristics of these basins, the mechanisms of rupture and the regoliths liquefaction processes, besides modelling the deposition in fan areas. This understanding couk brimgimprovements to disaster risk management strategies throughout in the Serra do Mar region.
Reference:
PICANÇO, Jefferson; VIEIRA, Bianca Carvalho; MARTINS, Tiago Damas; GRAMANI, Marcelo Fischer; FACCURI, Gabriel; SILVA, Marcio. Debris-flow occurrence in granite landscape in south-southeast 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)
