In Santa Catarina State (Brazil), Rio dos Cedros is one of the cities that suffered from natural disasters triggered by very intense rainfall in November 2008. According to the Municipal Civil Defense, this event caused economic losses of US$2.1 million and 96 homeless, directly affecting 90% of the municipal population. The principal phenomenon responsible for these disasters was the debris flow. In this context, field surveys were conducted throughout the city in order to investigate the possibility for houses to be affected by landslides and debris flows. After the preliminary evaluation, two cases of debris flow whose extensions were over 1 km were chosen for a more detailed survey. The objective of the present study was to analyze the meteorological and geomorphic aspects of these cases. The total rainfall in Rio dos Cedros in November 2008 and the entire year of 2008 were 644 mm and 2509 mm, respectively. An analysis of the daily rainfall during October and November 2008 and the debris flow occurrence time indicates that the factor triggering debris flows in Rio dos Cedros in 2008 was the accumulated rainfall, not its intensity. Two debris flows analyzed in the present study had different geomorphic conditions, one being confined in the channel and showing ordinal debris flow (Debris A), and the other unconfined, presenting the debris avalanche feature (Debris B). The larger density of clastic blocks was observed at the depositional area of Debris B. Both the localities are characterized with migmatite. Topographic analysis showed that the volume of the mass movement is related with topographic parameters (elevation difference and travel distance). This relationship implies that the two cases of Rio dos Cedros had similar behavior to other cases reported in temperate and cold regions. It is, therefore, concluded that there is geomorphic control on
Os escorregamentos são processos naturais que podem trazer diversos impactos ambientais, sociais e econômicos.A identificação e mapeamento de áreas suscetíveis a escorregamentos são procedimentos importantes no gerenciamento de bacias hidrográficas. O uso de modelos de estabilidade de encostas auxilia na gestão da problemática envolvendo os escorregamentos, mas frequentemente negligenciam o efeito da vegetação. Este trabalho apresenta uma metodologia para analisar o efeito da vegetação em modelos de estabilidade de encostas. Em primeiro lugar, parâmetros relacionados a vegetação foram inseridos no equacionamento do Fator de Segurança (FS). A partir de análise de sensibilidade, verificou-se quais parâmetros possuem maior influência na estabilidade. Posteriormente, o modelo SHALSTAB foi modificado, inserindo os parâmetros mais relevantes, e aplicado na Bacia do rio Cunha. Os efeitos mecânicos, gerados pela presença da vegetação, inseridos na equação do FS são: coesão das raízes (cr); sobrecarga gerada pelo peso da vegetação (Sw); tensão cisalhante oriunda da ação do vento nas copas das árvores (Ve). Observou-se que cratua no sentido de aumentar a estabilidade da encosta e sua influência é a mais significativa dentre os parâmetros analisados e é maior em solos rasos, diminuindo com o aumento da profundidade. O parâmetro Sw atua na redução da estabilidade da encosta e exerce maior influência em solos
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.