Assessment of landslide occurrences in Serra do Mar mountain range using kinematic analyses

Abstract

Due to its meteorological, geological and geomorphological settings, Brazilian’s Atlantic coast have suffered severe landslide phenomena, particularly along the cost of São Paulo, Rio de Janeiro, and Santa Catarina states. Studies have shown that these processes are complex and triggered by several factors. However, within the study area, many landslide locations are placed on gneiss migmatitic terrain with pronounced geological discontinuities. The objective of this paper is to assess landslide occurrences in Serra do Mar (Caraguatatuba, SP) and investigate, by means of kinematic analysis, how they correlate with foliation and fractures present on the rocks. Kinematic analysis is used to investigate which discontinuities are more favorable to landslides occurrence and their relationship with slope directions. Structural information and kinematic data models are used to evaluate cause–effect relationship of landslide processes. Results show that dip slopes, with NE–SW direction, have greatest potential for the occurrence of planar landslides. On the other hand, anti-dip and cross-dip slopes have a greater potential to develop wedge landslides. Rock weathering and fluid flux along foliation planes can intensify mass movement. Such effect is also seen in residual soil, since they are able to preserve relict structures of the rock. This study contributes to a better understanding of how geological structures, preserved in tropical residual soils, influence shallow landslides.