Analysis the susceptibility and the risk degree to shallow landslides in Aricanduva upper basin, São Paulo Metropolitan Region (SP)

Author(s)

Fabrizio de Luiz Rosito Listo

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH/SBD)
• Defense date: 2011-04-14

Examining board members

Bianca Carvalho Vieira; Kátia Canil; Emerson Galvani

• Advisor: Bianca Carvalho Vieira

Abstract

In the city of São Paulo, landslides occur frequently, causing the destruction of houses and economic damage with fatalities and the number of areas threatened by landslides has been increasing each year. The general objective of this research is to analyze the probability of risk and susceptibility to shallow landslides in the Limoeiro River basin, which is located at the head of the Aricanduva River basin, one of the main in the city of São Paulo. Specifically, the objective is to identify and analyze major anthropogenic interventions (land use classes) in 1973 to 2007 period, identify scale zoning and characterize spatially the risk areas, characterize and analyze the role of topographic parameters and assess the correlation between the risk areas and susceptibility maps. To map risk areas, we created a cadastral survey form to evaluate landslide risk in the field into four levels: R1 (low risk), R2 (average risk), R3 (high risk), and R4 (very high risk). To land use evolutionary analyses, was made the aerial photographs interpretation. From a Digital Elevation Model were generated slope angle, aspect, curvature and contributing area maps and calculated the Frequency Distribution (FD), that subsequently, these maps were correlated with the risk map, generating two indexes: Risk Concentration (RC) and Risk Potential (RP). To analyze susceptibility to landslides, we used the SHALSTAB (Shallow Landsliding Stability) mathematical model and calculated the FD, RC and RP. The last step was a joint analysis of the risk areas and of the susceptibility maps, which was verified the agreement or disagreement on each risk sector. From the land use evolutionary analysis, there was a 36% reduction of plant cover and increase of 23% in urban areas in the period 1973-2007. We mapped 16 risk sectors containing approximately 1872 at-risk homes, with 6 sectors with very high risk degree (R4). Topographically, the most susceptible areas those located at slope angles above 16,8°, oriented southwest quadrant, with concave forms with the largest contributing area. In the susceptibility map, 41% of the area was classified as stable and 20% as unconditionally unstable. Although the latter category accounted a smaller proportion of the total area, it contained a RC of 40% with a RP of 12%. We found that the locations of areas predicted to be unstable coincided with the risk areas mapped and this combination of methods can be applied to evaluate the landslides risk in urban areas and can assist public managers in defining areas that are unstable for occupation. (AU)

• FAPESP's process: 08/08878-7 - Analysis the susceptibility and the risk degree to shallow landslides in Aricanduva upper basin, São Paulo Metropolitan Region (SP)
• Grantee: Fabrizio de Luiz Rosito Listo
• Support Opportunities: Scholarships in Brazil - Master