Landslides Susceptibility Analysis in Blumenau, Southern Brazil: a Probabilistic Approach

Abstract

The translational landslides result from the combination of favorable conditions when one assumes the existence of functional relations between the spatial distribution of determining factors and processes. Thus, it is possible calculating the probability of occurring these landslides, as well as generating organized maps of susceptibility classes based on the inventory of slip scars and on the variables able to influence their occurrence. Accordingly, the aim of the present study is to analyze the spatial relations between the occurred landslides and a set of potential determining factors, as well as to propose and test susceptibility models based on this analysis. The application of Bayes' theorem of conditional probability using the weights-ofevidence technique allowed analyzing the spatial relations between a set of potential determining factors (geological, geomorphological and soil use and cover factors) and 294 translational landslides in 2008 in the study area. Fifteen different integration schemes of the weighted values, able to reflect the spatial association of each factor in relation to the landslides, were elaborated. The adjustment concerning the spatial independence between the themes and the classification and prediction efficiency of each scheme were analyzed. Three models have met the conditional independence requirements. It was possible identifying that the high-to-very-high susceptibility conditions have varied from 15% (in the model integrating the values of themes such as slope, plan curvature and distance to lineament) to 28% (in the model integrating values of themes such as slope and profile curvature) in Blumenau County Santa Catarina State, based on the selected models.

Distribuição espacial e temporal das ocorrências de movimentos de massa na cidade de Blumenau

“…Ao norte do rio Itajaí-Açu há o predomínio de estrutura geológica mais estável, composta por rochas antigas e desgastadas do embasamento cristalino correspondente ao domínio do Cráton Luiz Alves (SCHEI-BE, 1986). Com relevo formado por encostas de valor intermediário de declividade onde predominam formas de relevo colinoso com vertentes convexas e topos arredondados geralmente em altitudes entre 70 e 300 metros (LANGE FILHO, 2016;POZZOBON, 2019). Nesta porção do território municipal ocorrem vales fluviais abertos permitindo o desenvolvimento de solo espessos em função da intensa atuação de processos pedogenéticos, o que se reflete no predomínio de movimentos de massa do tipo escorregamento rotacional.…”

“…A complexidade geológica combinada a acentuada declividade resulta em amplitude altimétrica de cerca de 980 m, com cotas mais elevadas situadas no extremo sul do município chegando perto dos 1000 m de elevação (Morro Loewsky). Caraterizada pela formação de vales em "V" profundos com rios encaixados em falhas e fraturas predominantemente na direção nordeste, a porção extremo sul do município apresenta intensa dinâmica geomorfológica que, combinada a elevada amplitude das vertentes, indica uma morfogênese muito ativa (SANTOS, 1996), o que impede a formação de solos profundos (POZZOBON, 2019). As diferenças entre as condições de relevo nas duas porções do território também podem ser visualizadas na Figura 2 e 3.…”

Study on the Prediction of Slope Failure and Early Warning Thresholds Based on Model Tests

“…Landslides triggered by rainfall occur globally and have significant impacts on lives, property, infrastructure, and the environment, for example, in North and South America [1,2], Europe [3,4], and Asia [5,6]. For this reason, early warning systems aim to mitigate the risk of landslides and are indeed garnering attention as a non-structural, cost-effective countermeasure to landslide disasters.…”