Relação entre o relevo e a rede de drenagem na análise da condição de equilíbrio no alto rio Piranga (MG)

Abstract

The relationship between landforms, slope processes and fluvial channels is a key point in many geomorphological theories, for the importance of adjustment between erosional processes, base level and environmental conditions under which this happens. The channel slope and hillside valleys define the potential energy for water flow to material transport on the fluvial system. Thus, it should be expected that in accordance with higher slopes the fluvial gradients would be higher too; the same way lower slopes should be associated with lower channel gradients. That is the prerogative checked here and considered by Strahler (1950; 1977) as representative condition of geomorphological equilibrium. It was tested by the analysis of eight river basins of 3rd order in the upper Piranga River at Minas Gerais – Brazil. This study was based on the verification of fluvial systemand its morphodynamical conditions by the way the equilibriumcondition of relief. It was checked: (i) the correlation between channelgradients and slope hillsides on these drainage basins; (ii) the mainchannels longitudinal profiles and (iii) Hack’s index (SL) to mainchannels and its segments of upper, medium and lower river. Theresults show lack of correlation between river gradients and averageslope of valleys, which reflects a misfiting between slope processes andchannel incision. This setting is supported by longitudinal profiles andHack’s index and confirms a recent reorganization of fluvial systemin the upper Piranga River drainage basin.