DEAMB - Departamento de Engenharia Ambiental

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Browsing DEAMB - Departamento de Engenharia Ambiental by Author "Barella, Cesar Falcão"

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    Análise da susceptibilidade a escorregamentos usando a abordagem estatística do fator de certeza no município de Moeda, Minas Gerais.
    (2015) Barella, Cesar Falcão; Sobreira, Frederico Garcia
    Nas últimas décadas vêm sendo observada uma intensificação dos processos geodinâmicos com consequências desastrosas, fruto da expansão irregular e desordenada dos centros urbanos. Para minimizar as implicações desses eventos, em 2012, foi instituída a Política Nacional de Proteção e Defesa Civil, que visa, entre outras premissas, estabelecer estudos de identificação e avaliação de áreas susceptíveis, ou seja, o mapeamento de susceptibilidade a eventos geológico-geotécnicos. Dentre as diferentes abordagens existentes, as técnicas estatísticas têm-se destacado por minimizar a subjetividade imposta pelo operador e permitir a validação do próprio modelo preditivo. Assim, com o foco nos escorregamentos, esse trabalho buscou testar a aplicabilidade da técnica do fator de certeza e avaliar sua acurácia por meio da taxa de sucesso e predição. Aplicado em uma área piloto, que se localiza no município de Moeda-MG, o modelo, integrado pela declividade, geologia, geomorfologia e perfil e orientação das vertentes foi considerado um instrumento promissor na elaboração do mapa de susceptibilidade. Os resultados foram agrupados em zonas de acordo com o número de escorregamentos previstos. A classe mais susceptível conseguiu evidenciar 70% dos deslizamentos, ocupando apenas 29% do território, alcançando, dessa forma, o objetivo de restringir uma elevada quantidade de futuros movimentos numa pequena porção do terreno.
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    Análise das diferentes abordagens empregadas na avaliação da vulnerabilidade a escorregamentos.
    (2018) Ferreira, Sabrina de Paula; Barella, Cesar Falcão; Corteletti, Rosyelle Cristina; Tavares, Vera Lúcia Silva; Xavier, Mateus Oliveira
    Este artigo apresenta as principais diretrizes atualmente utilizadas para análise de vulnerabilidade física a escorregamentos, bem como a exposição de incertezas que podem ocorrer nos métodos de cálculo recentemente aplicados, desde falhas inerentes ao próprio método, assim como possibilidades de erros de interpretação de resultados. Os principais pontos de discrepância encontrados se resumem nas diferentes variáveis consideradas na determinação da vulnerabilidade, assim como no grau de importância que cada variável recebe durante a análise, além do caráter qualitativo e quantitativo das avaliações. O estudo indica que, apesar de ainda não ser possível e aconselhável a utilização de um método universal de avaliação de vulnerabilidade aplicado em diferentes cenários, é necessário um modelo abrangente, que nos dê diretrizes para aplicação deste parâmetro na avaliação de risco em diferentes situações, assim como nos alerta para a responsabilidade de se utilizar um método não aplicável para determinado contexto geológico-geotécnico.
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    A comparative analysis of statistical landslide susceptibility mapping in the southeast region of Minas Gerais state, Brazil.
    (2018) Barella, Cesar Falcão; Sobreira, Frederico Garcia; Zêzere, José Luís
    Statistically based landslide susceptibility mapping has become an important research area in the last decades, and several bivariate and multivariate statistical approaches to landslide susceptibility assessments have been applied and compared in all regions of the world. The aim of this study was to compare different statistical approaches and to analyse the degree of spatial agreement between the landslide susceptibility maps produced. To this end, we selected seven statistical methods for comparison, namely, landslide density, likelihood ratio, information value, Bayesian model, weights of evidence, logistic regression and discriminant analysis, and then applied these to an inventory comprising 940 translational landslides, in the southeast region of Minas Gerais state in Brazil, at the western edge of the Quadrilátero Ferrífero (642.13 km2). In some statistical approaches, modifications were made to the input dependent variables. The landslides registered in the inventory map have been used in punctual and polygonal form. Six factors were considered as input landslide predisposing factors: slope angle, geomorphological units, slope curvature, lithological units, slope aspect and inverse wetness index. The combination order of the landslide predisposing factors was established based on a sensitivity analysis, which gave rise to five different cartographic combinations. In total, 58 statistical models of landslide susceptibility were produced, and the results were validated using success and prediction rate curves. The spatial agreement evaluation between the model results was carried out with kappa statistics. There were 214 comparisons of spatial agreement involving classified models at three relative degrees of susceptibility (high, medium and low landslide susceptibility classes). The results showed that all of the models so produced had satisfactory validation rates. The best landslide susceptibility models obtained areas under the curve of > 0.80 in the success and prediction rate curves, with emphasis on the weights of evidence, the information value and the likelihood ratio statistical methods. These statistical approaches were performed with the landslides mapped in the form of points. The landslide susceptibility classes of these models visually demonstrated a slightly more irregular spatial distribution when compared to the models performed with landslide polygons. The likelihood ratio model performed with landslide points presented one of the smallest areas for the high susceptibility class and the largest area for the low susceptibility class. The analysis of the spatial agreement showed that the models produced with a polygonal dependent variable tend to be more concordant, regardless of the statistical technique used. Moreover, we verified that spatial agreement tends to increase with increasing accuracy of the models. Despite the discrepancies found, most of the models compared showed a substantial or almost perfect degree of agreement.
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    Compensating deforestation with forest surplus : key regulatory issues within Brazil's atlantic forest.
    (2020) Cruz, Júlio César da; Barella, Cesar Falcão; Fonseca, Alberto de Freitas Castro
    Brazil has created a market mechanism for compensating past deforestation based on the acquisition of forest surplus from different properties. This mechanism, known in Brazil as the ‘CRA market’, could become the world's largest forest compensation program. The success of this market depends on the specifics of regulations that are yet to come. The objective of this article was to explore three relevant issues to the regulation of a future CRA market within the Atlantic Forest of Minas Gerais state: the balance between supply and demand; incentives for trade in priority areas; and potential policy overlaps between different compensation programs. Based on geospatial evaluations and content analysis of government documents, the study revealed a potential oversupply of CRAs in the Minas Gerais Atlantic Forest, as surplus areas were found to be 2.76 greater than deficit areas. Eventual incentives for trade in priority areas could lessen oversupply, but unfold into sensitive territorial tradeoffs. The potential overlap between the CRA market and the existing compensation program of the Atlantic Forest Act, while still unclear, is unlikely to be a very relevant one. Future avenues of research are suggested
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    Discriminant analysis as an efcient method for landslide susceptibility assessment in cities with the scarcity of predisposition data.
    (2021) Eiras, Cahio Guimarães Seabra; Souza, Juliana Ribeiro Gonçalves de; Freitas, Renata Delicio Andrade de; Barella, Cesar Falcão; Pereira, Tiago Martins
    The city of Ouro Preto, which is located in the state of Minas Gerais, Brazil, has a long history of mass movements infuenced by the regional geology, geomorphology, and anthropic activities, which have resulted in harmful consequences to the population. How- ever, most of the studies conducted in the region are qualitative and are directly dependent on the experience specialists. The aim of this study was to analyse the landslide suscepti- bility in the urban region of Ouro Preto quantitatively by using discriminant analysis. The landslide inventory was obtained by using unmanned aerial vehicle images and feldwork. ArcGIS 10.6 and R 3.5.1 software were used, and the following landslide predisposing fac- tors were considered: slope angle, slope aspect, profle curvature, and topographic wetness index (TWI). As geological and geotechnical data are still scarce in the interior of Brazil, we only used data derived from topography to determine the efectiveness of these factors for analysing landslide susceptibility. The slope angle proved to be the factor that most diferentiated unstable from stable terrain, followed by TWI. The other parameters were not as efective in diferentiating the stability conditions. The model efciency was 88.6%, the specifcity was 93.3%, and the sensitivity was 85.0%. Also, the prediction and success curve were used to evaluate the accuracy of the proposed landslides model, by using the area under the curve (AUC) criteria. It was shown that the AUC values 0.851 for testing and 0.838 for training indicate that the developed model provides an excellent prediction. The main contribution of this work is the demonstration of the efectiveness of using easily accessible data (derived from topography) for analysing landslide susceptibility with amultivariate statistical method. This method can contribute valuable information to urban planning eforts in cities without the need for robust data.
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    Landslide susceptibility mapping using the statistical method of information value : a study case in Ribeirão dos Macacos basin, Minas Gerais, Brazil.
    (2021) Rosa, Mateus Lima; Sobreira, Frederico Garcia; Barella, Cesar Falcão
    This research study was developed in the Ribeirão dos Macacos basin at the district of Nova Lima, Minas Gerais state, Brazil. The information value statistical method was applied in the construction of the landslide susceptibility map at the 1:25,000 scale. Different partitions of the inventory were tested, as well as different landslide predisposing factors. In the construction of the landslide inventory, the south, southeast and south-west slopes generally present a higher quality in aerial / orbital images due to the position of the sun (lighting direction), which emphasizes the surface structures and it may omit old landslides on slopes facing north, northeast, and northwest. This condition can generate misleading models when using the slope aspect. Another verifi cation was that the models with better Area Under the Curve index will not always restrict the high susceptibility class in smaller areas. This incongruence occurs due to the different curve conformations, since a smaller index curve can present more restrictive results than a larger index curve. The results showed that the model has a high capacity of adjustment to the input data and high landslide predictive capacity.
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    Modelagem da susceptibilidade de escorregamentos utilizando o método de pesos de evidência em uma região montanhosa de clima tropical.
    (2021) Araújo, João Paulo de Carvalho; Barella, Cesar Falcão; Fernandes, Nelson Ferreira
    Escorregamentos são fenômenos naturais que ocorrem em regiões montanhosas e podem causar grandes catástrofes socioeconômicas. A identificação das áreas susceptíveis a escorregamentos é uma etapa essencial da gestão de riscos e auxilia a implementação de projetos que visam mitigar, ou mesmo evitar os danos causados por estes eventos. Este trabalho avalia a susceptibilidade a escorregamentos translacionais pelo método estatístico bivariado de Pesos de Evidência, assim como o controle individual de oito fatores predisponentes em duas bacias piloto no maciço da Tijuca, na cidade do Rio de Janeiro (RJ). Cinco modelos de susceptibilidade foram produzidos pela combinação dos fatores predisponentes e tiveram sua capacidade preditiva testada pelo cálculo da área abaixo da curva (AAC). A maior parte dos escorregamentos mapeados ocorreram nas cabeceiras de drenagem das bacias piloto, nas encostas com ângulo entre 34° e 51°, sustentadas principalmente por intrusões graníticas e coberta por floresta preservada. O mapa final possui cinco classes de susceptibilidade e demonstrou ser eficaz na previsão dos escorregamentos. O método é robusto e evita subjetividades, ao mesmo tempo que é bastante versátil. Apesar de pouco utilizado no Brasil, o método é apropriado ao contexto de complexa geodiversidade e carência de dados geotécnicos, em escala regional e local.