Development and assessment of an erosion and landslide predictive model for the coastal region of the State of São Paulo, Brazil

Abstract

The study area is a Water Resources Management Unit #11 (WRMU-11), with steep slopes and very dissected and undulated relief, located in last continuous remaining parts of the Atlantic Forest in the State of São Paulo (Brazil). This paper presents a new predictive model for the identification of susceptible areas to erosion and landslides in the WRMU-11 region by combin­ing geotechnical tools and field work. In order to evaluate the methodology, multi-criteria analysis was performed using the IDRISI Andes software. The areas that are more susceptible to erosion are located in Apiaí, Barra do Chapéu, Barra do Turvo, Cajati, Eldorado, Itaóca, Itapirapuã Paulista and Ribeira. 128 landslide occurrences observed in field surveys in the Ribeira de Iguape River Valley were plotted on the landslide susceptibility map. Ten occurrences were situated in areas classified as low susceptibility to landslides; fifty-six occurrences in areas of moderate susceptibil­ity, fifty-five in areas of high susceptibility, and seven in areas were situated in areas of very high susceptibility to landslides. Field data showed that the Erosion and Landslide Susceptibility Maps, in 1:250,000 scale, provide reliable predictions.