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nearly half a century has been performed, concentrating on the impact of sand and
gravel mining and the recuperation of abandoned mining areas as well as on the
proceeding urbanisation. Fig. 4 shows the dynamic of the urbanisation of the alluvial
plains from 1977 until 1990. These analyses were accompanied by field observations
including geological, pedological and environmental aspects such as the state of the
recuperation of abandoned extraction areas as well as sedimentological structures. The
total area of 6,68 km² of the alluvium between the road MG 424 and the road MG 010,
have been subject to many drastic transformations during the last decades. Frequent
changes of the riverbed, erosion at its margins, siltation and the augmentation of
exposed soil in the alluvial plain could be observed.
Fig.4: Proceeding urbanisation of the alluvial plain of the Riberâo da Mata
between 1977 and 1990.
The peak of the sand mining activities was in the decades of 1970 to 1980, when the
city of Belo Horizonte was growing very rapidly and environment legislation was less
strict. Still, even today, active sand and clay mines can be found in the area, showing
the importance of these resources for the city. During the last decades, approximately
30% of the study area has been subject to mining (1.5 km² during the 1977 and only 0,5
km² in 1990). In some abandoned mining areas, industrial plants breaking carbonate
rocks for gravel substitution have been constructed, as the alluvium offers plain
construction sites. The gravel mining has stopped since, as the natural gravel resources
are scarce and deep seated. The natural recuperation of abandoned mining areas is
slow and exposed soil and active erosion carries away fertile soil and increases the
sediment load of the river. In the 1970s, 0,4 km² of the area could be classified as
exposed soil showing signs of erosion. The multi-temporal analysis of the land use in
this area together with a comparison with other source areas showed that certain georesources
like sand and gravel for construction purposes are heavily needed in close
distance to the growing city, but competing for space with other uses and with
environmental legislation.
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