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RESUMODeslizamentos são episódios de extrema importância, resultantes da atuação de processos geomorfológicos nas mais diversas escalas temporais causando, em geral, enormes prejuízos à sociedade. Dentre os diversos fatores condicionantes destacam-se os parâmetros morfológicos do terreno, os quais controlam diretamente o equilíbrio das forças e, indiretamente, a dinâmica hidrológica dos solos. Embora muitos estudos tenham voltado a atenção para a descrição de eventos e para o monitoramento de campo, pouco ainda se sabe sobre a previsão de ocorrência destes fenômenos. Acredita-se aqui que a combinação de mapeamentos e monitoramentos de campo, através de modelos matemáticos baseados em processos, tenha muito a contribuir nessa direção. Neste sentido, diversos estudos de campo vêm sendo realizados nas bacias dos rios Quitite e Papagaio no sentido de caracterizar o papel desempenhado pelos diversos parâmetros topográficos no condicionamento dos deslizamentos ali ocorridos em 1996. A partir do modelo digital de terreno das bacias, com uma resolução de 4m 2 , combinado com vários mapeamentos ali realizados, foi definido o potencial de deslizamento para as diversas classes de cada atributo topográfico. Paralelamente, foram realizados ensaios de campo com o permeâmetro de Guelph e simulações com o modelo matemático SHALSTAB, voltado para a previsão de áreas instáveis, de modo a englobar os mais diferentes cenários. Os resultados atestam o importante papel desempenhado pelos parâmetros topográficos forma da encosta e área de contribuição, geralmente desprezados pelas metodologias de previsão de áreas susceptíveis a deslizamentos.Palavras chave: deslizamentos, hidrologia das encostas, modelagem matemática, instrumentação dos solos. ABSTRACTLandslides are important geomorphological processes, acting along different temporal scales and generally causing huge problems to society. Between the different controlling factors an important role is played by the morphological parameters which directly affect the equilibrium between the forces and indirectly control hillslope hydrology. Although many studies have focused on the description of previous events and field monitoring, little is known about landslide prediction, defining where and when these processes will happen in the near future. It is believed that the combination of field mapping and monitoring with process-based mathematical models is an important tool to landslide investigation. A variety of studies have been carried out in Quitite and Papagaio river basins in order to investigate the role played by the topographic parameters in the landslides triggered by 1996 intense rainstorms. Based on the digital terrain model of the basins, with a 4m 2 resolution, together with the different maps obtained, a landslide potential index for the many classes of each topographic attribute was defined. At the same time, field experiments with the Guelph permeameter were carried out and a variety of scenarios were simulated with the SHALSTAB model, a mathematical model for the topog...

Abstract.Various methods are currently used in order to predict shallow landslides within the catchment scale. Among them, physically based models present advantages associated with the physical description of processes by means of mathematical equations. The main objective of this research is the prediction of shallow landslides using TRIGRS model, in a pilot catchment located at Serra do Mar mountain range, São Paulo State, southeastern Brazil. Susceptibility scenarios have been simulated taking into account different mechanical and hydrological values. These scenarios were analysed based on a landslide scars map from the January 1985 event, upon which two indexes were applied: Scars Concentration (SC -ratio between the number of cells with scars, in each class, and the total number of cells with scars within the catchment) and Landslide Potential (LP -ratio between the number of cells with scars, in each class, and the total number of cells in that same class). The results showed a significant agreement between the simulated scenarios and the scar's map. In unstable areas (SF≤1), the SC values exceeded 50% in all scenarios. Based on the results, the use of this model should be considered an important tool for shallow landslide prediction, especially in areas where mechanical and hydrological properties of the materials are not well known.

Abstract:Landslides are natural processes triggered by complex relationships between many conditioning factors. In Rio de Janeiro city, intense rainstorms combined with steep slopes, usually occupied by slums, create favourable conditions for landslide generation. In general, slope failures are related to high positive pore-pressures inside soil mantles, which are associated with topographic hollows and hydraulic discontinuities inside the deep weathered profile.This study aims to characterize the role played by spatial variations in saturated soil hydraulic conductivity K sat on landsliding in the Papagaio Basin (2Ð5 km 2 ), triggered by intense rainstorms (250 mm in less than 2 days) in February 1996. Field measurements, using the Guelph permeameter, were conducted along soil profiles (up to 5Ð0 m depth), around and inside landslide scars representing different geomorphological domains. Also, soil physical properties (grain size, total porosity, macroporosity, microporosity, etc.) were evaluated at the 87 sites where K sat was measured.Despite the many geological and pedological variations inside the basin, including changes in lithology, fracture density, vegetation type and succession stage, soil characteristics and weathering stage, and human activities, 94% of the K sat values varied by only two orders of magnitude 1Ð0 ð 10 6 -9Ð0 ð 10 5 m s 1 ). However, abrupt changes in K sat were observed along some of the soil profiles studied, e.g. an increase of two orders of magnitude in only 0Ð30 m. These hydraulic discontinuities may contribute locally to the development of high pore pressures during intense rainstorms, leading to landsliding. The results also suggest that different K sat variation patterns coexist inside the basin, which should be considered in mathematical models of landslide prediction.

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