Many factors control the generation of shallow landslides in the tropical steep slopes of Rio de Janeiro (e.g., soil properties, inherited rock features, vegetation cover, hillslope morphology and subsurface hydrological conditions). During the last few decades, these relationships became even more complex due to the spreading of human occupation towards the hills. In order to characterize the role played by each one of these factors, it has become relevant to combine field monitoring and mapping with mathematical models based on physical laws.

This study aims to evaluate the relative influence of some controlling factors on the extensive shallow landsliding that took place in February 1996 along the Papagaio basin (RJ), combining field mapping with simulations using the SHALSTAB model, developed by Dietrich and Montgomery (1998). To carry out this investigation a small sub-basin was selected, where landslides took place on only one side of the valley. Landslide scars and vegetation cover were mapped from aerial photographs and field work while contribution area and slope maps were obtained from a high resolution DEM.

The results showed a good agreement between the predicted unstable areas and the location of landslide scars from 1996. The differences observed on the distribution of vegetation cover alone, degraded forest in the hillslope dipping south and grass in the one dipping north, do not justify the instability predicted by the model for this last one, because the simulations neglected cohesion, hence the direct effect of vegetation. The results attest the major role played by hillslope morphology, specially slope and contribution area of each cell in the basin. In order to accomplish a better understanding of these complex relationships, future research should include detailed field mapping of soil and rock properties together with new simulations for other possible scenarios.