In Gouveia, MG, gullies are one of the most striking features of the landscape. Their occurrence is restricted to the areas whose geological substract is formed of granit-gnaisses from crystalline basement and by schist, basic and metabasic rocks. These are also the only areas with the presence of soils to support agricultural activities. Where quartzite from Espinhaço Supergroup predominates, only arenosoils or very sandy lithosoils occur. Mapping of gully spatial distribution shows a close relationship with the pattern of some type of land use and management. From the 66 mapped gullies occurring in Tombador, Padre and Tamanduá basin, 73% are localised in hollows and amphitheatres in association with the presence of different types of fences; 18% are present in mining areas and 9% are close to roads or paths. There are three most frequent types of fences in Gouveia. There is an old wall constructed with stones, remainders of slave times, with no presence of gullies associated. A second type is the common wire and wood fence used until today. In order to minimise the costs the farmers use only two or three lines of wire constructing at the fence side a small levee-like structure. Beside it a long depression is opened to protect the levee against runoff. It concentrates the running water inducing gully processes to take place. A third type, also not very much used today, is a long trench opened to divide properties and, in some cases, to protect small agricultural areas from the invasion of cattle. Most of them were transformed into gullies through the action of surficial water concentration. The most effective mechanism of vertical incision is the direct effect of the concentrated runoff along the valley bed while lateral expansion occurs mainly through mass movements. Structural characteristics of the underlying rocks play an important role in defining lines of preferential lateral retreat. Preliminary results of geochemical analysis of the soils pointed out the influence of iron content in the occurrence of piping associated to the gully processes. Although the study confirms a close relationship between the occurrence of gullies and the type of land use, correlative deposits of a similar type of process dated with C¹⁴ (ð¹³), corresponding to the Laschamps subchron has been found in the area.
*This research was financially supported by FAPEMIG. Eixo: Gully Erosion.