The municipality of Maringá, situated in the north of Paraná, in spite of its clay soils, shows serious processes of erosion, generated by concentrated water drainage. The origin and evolution of some forms of erosion resulting from this situation are related to the use of the soil in urban and rural areas.

With the aim of determining the origin and the dynamics of the erosion in catchment areas, field surveys were carried out with measurements, along with description of the soil and collection of samples for sediment analysis.

The data obtained indicate that occupation of watersheds have been conditioned the concentration of pluvial drainage directed towards the headwaters, mainly in the urban area. Unsuitable urban drainage conditions have culminated in the formation of extensive gullies within the preservation areas of the original forest land (Interior Tropical Forest) in the city of Maringá. Both these areas and urban equipments are being seriously threatened by the progressive increase in the evolution of those gullies.