Soil structural indicators of hillslope destabilization in the Serra do Mar mountain range (Rio de Janeiro State, Brazil)

Mass movements are amongst the main problems related to natural disasters in Rio de Janeiro State. The cities which suffer most due to these events remain on alert during each rainy season. Many surveys have been conducted to map hazard risk areas. Many authors associate these phenomena with geological characteristics, and some recognize the role of soil properties. This paper outlines the soil indicators which contribute to hillslope destabilization in the Serra do Mar mountain range. A hillslope was selected and soil samples collected from six trenches, along the slope. Soil micromorphological and physico-chemical analyses were conducted to assess mass movement hazard. The presence of gibbsite on the upper third of the slope is one of the factors that can decrease horizon permeability and therefore destabilize slopes. On the lower third of the slope, structures demonstrate that part of this soil is formed by material originating from the upper slope.