Application of the Shalstab model for mapping susceptible shallow landslides in Caraguatatuba, Serra do Mar (SP

Abstract

Although the prediction of shallow landslides in unstable areas is essential to reduce the social, economic and environmental damage this is not a simple task due to the complexity of the factors that control the slope stability. The mathematical model SHALSTAB calculates the susceptibility to shallow landslides considering topographic and soil parameters. Thus, the aim of this paper was to evaluate the susceptibility to shallow landslides in a watershed located in Caraguatatuba city, using the SHALSTAB mathematical model. A Digital Terrain Model (DTM) was produced with 5 m resolution and thegeotechnical data used by researches conducted in the same region. As a result, 131 scars (2.3% of the basin area) were mapped and these are distributed in all classes of instability. Tests with the model showed that the decrease of the internal friction angle and cohesion had increased significantly the unstable areas. About 55% of the scars were located on unstable classes: 16,2% (chronically unstable), 12,7% (log Q/T <-3,1), 11,7% (log Q/T -3,1 to -2,8) and 14,4 (log Q/T -2.8 to -2,5). For susceptibility maps to be produced in the future it is recommended using soil parameters spatially distributed (soil depth, cohesion and angle of internal friction) and can will be generated more accurate results.