PIPING IN AREA OF GULLY EROSION, NORTHWEST REGION OF MINAS GERAIS

Tubular voids formed through piping are well studied as features of sub-superficial erosion encountered in several climatic zones. Literature indicates piping as a process associated with gully erosion. This article discusses four (4) different types of pipes observed in the study area in Gouveia, state of Minas Gerais, in a sub-humid tropical region of the brazilian cerrado (savanna) with predominance of latosols, some times related to [of which show close relation with] the presence of gullies. Gullies occur on convex as well as concave slopes developed predominantly on granite-gneiss, basic and metabasic rocks, [which] forming an undulating landscape with long slopes varying from gentle to moderately gentle (5 to 120) inclination. Tops are long and relatively flat, maintaining massive types of hill interrupted by no developed hollows and large spurs. Piping was identified in different situations during field works, through the occurrence of pipes, collapsed or not. They differ [one from another] not only in size but also in terms of their location on the slope, soil type and [even] in relation to their position along the gully walls. In this paper the pipes are described and classified on the basis of the existence or not of the tunnel collapse and [regarding] their association with the evolution of the gullies. The collapse generates the occurrence of a superficial channel and enhances the development of gullies. Two situations were detected regarding channels without collapsed: tubular voids found during the opening of soil profile that shows no correlation with the presence of gullies, and tubular voids detected through the use of geo-radar (GPR), what made it possible to establish the association between piping and gullies. Fields evidence permitsto assume that in some circunstances there is a close relationship between piping and gully, showing that piping should be taken into account as an important process involved with the initiation and development of gullies.