Application of slope stability analysis models in a GIS environment to predict landslides in the Serra do Mar region, SP

Abstract

The triggering of landslides by the reduction of suction (unsaturated condition) from the infiltration of rainwater is one of the main mechanisms of instability in tropical and subtropical areas in different countries, often causing significant social and economic damages. In Brazil, several researches were developed focusing on these processes and mainly studying colluvial soils and residual soils of crystalline rocks in mountainous regions of the Southeast of the country.Numerous models have been elaborated and applied in the prediction of areas susceptible to shallow landslides in extensive mapping works at different scales. The most recent and promising research line is based on the application of physical-based mathematical models combining deterministic stability analysis methods with hydrological models in applications developed for Geographic Information Systems (GIS) software.The general objective of the research is to investigate the efficiency of the slope stability analysis models for GIS in the prediction of areas susceptible to shallow landslides. Specifically, the SHALSTAB - Shallow Slope Stability, SINMAP - Stability Index Mapping and TRIGRS - Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Model models will be investigated in conjunction with the infinite slope method. The first three models are the most widespread in the specialized literature. The infinite slope method is characterized in Geotechnical Engineering as a deterministic method of slope stability analysis of the limit equilibrium type. This method serves as the basis for the mathematical formulation of the other three models investigated.Susceptibility maps will be produced from simulations of generalized landslides triggered on January 12 and 13, 2014 in Serra do Mar, on the border between the municipalities of Apiaí and Itaóca (SP). The inclusion of the infinite slope method and the spatial distribution of the precipitation values that trigger the landslides event used in the simulations are the main differential aspects of this research in relation to the previous works.The main expected result for the proposed research is the performance evaluation of the slope stability analysis models infinite slope, SHALSTAB, SINMAP and TRIGRS in the mapping of shallow landslides susceptibility, considering the mechanisms of deflagration (unsaturated and saturated conditions), the geological-geotechnical and climatic characteristics of the Serra do Mar region. The use of the infinite slope method in the simulations will provide an effective comparative basis for analyzing the influence, advantages and disadvantages of the input parameters of each model investigated.As complementary results, we highlight the inclusion in the stability analysis models of the spatial distribution of rainfall values associated with the generalized landslide event considered in the validation of the results and the improvement of the validation procedures based on the spatial distribution of the slide scars. (AU)