This paper describes the geological–geotechnical study of the occurrence of a mass movement on a hillside in the municipality of Camaragibe, Pernambuco state, Brazil. Comprehensive onsite geotechnical investigation was performed involving borings, collection of deformed and undisturbed samples, moisture profiles, hydraulic conductivity tests (Guelph permeameter), and study of wastewater disposal. Laboratory tests were performed, including chemical, mineralogical and physical characterization, permeability (triflex), suction studies, oedometer, direct, suction-controlled, multiple reversal, and ring shear tests; instrumentation also involved the use of Casagrande and maximum piezometers, water level gauges, slope indicators, and a pluviometer. The data obtained in the laboratory and on site enabled characterization of the materials involved in the landslide (Barreiras Formation and granite residual soil) and understanding of the mechanism, its stability analysis at the failure stages, and reactivation. It is cited as having predisposing factors to instability, namely geology, anthropic action, and relief. Rainfall was indicated as the primary triggering factor. At the failure stage, the movement was classified as multiple rotational landslide. At the reactivation stage, the displacement occurs in blocks.

This article evaluates the unsaturated behaviour of fine-grained tropical soils for application in transport infrastructure. An extensive experimental campaign was conducted covering physical, chemical, mineralogical and mechanical tests. Simulations of a pavement structure were carried out applying the new Brazilian pavement design method (MeDiNa). The results showed highly weathered soils, with classification ranging from A-4 to A-7-6 (TRB), SC, SM, ML and CL (USCS), but of the same class MCT (LA’ – lateritic sandy soils), bimodal SWCC and excellent resilient modulus (394–680 MPa). The compaction directly influenced its unsaturated behaviour. The soils were proved to be suitable for use in the pavement with high traffic, thus enabiling the exploitation of the local materials and reducing costs with transport and acquiring scarce granular materials. Polynomial and linear regression equations were proposed to predict the MR as a function of confining and deviation stresses acting in the subgrade and sub-base layers.

. In the Metropolitan Region of Recife, Northeast Brazil, landslides caused a total of 214 deaths between 1984 and 2012. Efforts have been made, but there is still need to improve the risk area management by discovering the correlations between the rainfall and landslides and by implementing a disaster warning and prevention system in order to reduce the number of accidents and fatalities. The purpose of this study is to propose rainfall parameters likely to trigger mass movements, as a contribution to risk management in this region. It specifically addresses the study undertaken in three municipalities: Recife, Camaragibe and Jaboatão dos Guararapes, which have disorganized occupation in high and very high risk areas. In order to achieve the prime objective, rainfall and landslides were tracked during 2009 to obtain correlations between them. After the data was logged, the rainfall accumulation associated with landslides was checked. According to each area with civil defense action of the municipalities involved in the study, critical values of the cumulative rainfall in 72 h (I72 h), in the long term (Pac) and the parameter Rcrit resulting from the product of I72 h by Pac, are suggested herein to be recommended for operations of the Warning and Alert states. By achieving these critical values, they increase the probability of landslide events, and are important for taking decisions and instructions on Civil Defense actions.

DOI: http://dx.doi.org/10.21168/rbrh.v21n2.p377-390 ABSTRACT Studies focusing on urban vulnerabilities due to river floods need the construction of hazard maps and definition of potential flood areas. The objective of this article is to describe the development of a methodology for hazard mapping of river floods and to map areas susceptible to inundation on a municipal scale. The study area is the municipality of Ipojuca - Pernambuco State with area of 527.11 km2 and population of 80,637 inhabitants. The first methodology uses the hydrologic-hydraulic simulation for the lower course of the Ipojuca River using the HEC-HMS and HEC-RAS models. The streamflow calculated in the rainfall-runoff model is used as input for the hydraulic model, to simulate the water surface profile in the river. This makes it possible to calculate the water depth and flow velocity, the key elements for the definition of hazard indicators. The results of the hydraulic model were used to generate the hazard indicators: water depth, flow velocity, combination of depth and velocity, energy head, flow force and intensity (flow velocity x water depth). The other methodology seeks to identify areas with potential for inundation considering the entire territory of the municipality. Topographic index of the region and a distance cost matrix (which uses slope and drainage) are the auxiliary variables for determination of this map. Both variables use the digital terrain model. Analysis of risk is essential for planning and intervention in areas susceptible to inundation. Both characterizations of hazard and vulnerability are needed to evaluate risk. The results of the study in Ipojuca can be used for hazard characterization RESUMO Estudos envolvendo vulnerabilidade de cidades ? inunda??es necessitam do mapeamento de perigo e das ?reas com potencial para inunda??o. O objetivo do artigo ? desenvolver metodologia para mapeamento de indicadores de perigo e ?reas inund?veis na escala de munic?pio. A ?rea de estudo ? o munic?pio de Ipojuca no Estado de Pernambuco com ?rea de 527,11 km? e uma popula??o de 80.637 habitantes. A primeira metodologia consiste na simula??o hidrol?gica-hidr?ulica para o baixo curso do rio Ipojuca com uso dos modelos HEC-HMS e HEC-RAS. A vaz?o gerada no modelo hidrol?gico do tipo chuva-vaz?o ? utilizada como entrada do modelo hidr?ulico que simula o perfil da linha d-?gua no rio para a regi?o de interesse. Com o perfil da linha da ?gua, pode-se determinar a profundidade e a velocidade da ?gua, que s?o elementos chave para a defini??o de indicadores de perigo. Com os resultados do modelo hidr?ulico, geraram-se seis indicadores de perigo: profundidade da ?gua, velocidade do fluxo, combina??o profundidade e velocidade, carga de energia, for?a do escoamento e intensidade (velocidade x profundidade). A outra metodologia procura identificar as ?reas inund?veis de todo o territ?rio do munic?pio. Para isso, faz-se uso do ?ndice topogr?fico da regi?o e de uma matriz de custo de dist?ncia (que utiliza declividade e hidrografia), todos calculados com o modelo digital do terreno. A an?lise de risco ? essencial para o planejamento e interven??o em ?reas sujeitas a inunda??es. Para se avaliar risco, ? necess?ria a caracteriza??o do perigo e da vulnerabilidade. Os resultados do estudo em Ipojuca podem ser utilizados para a caracteriza??o do perigo principalmente.