Electronic Material Properties - und Geowissenschaften ...

Geology, land use change and erosion in the northern
periphery of Belo Horizonte, Brazil
Monika Hofmann 1 , Andreas Hoppe 1 , Allan Buchi², Joachim Karfunkel 2,
Ricardo Pagung 2
1 Institut für Angewandte Geowissenschaften, TU-Darmstadt, Germany;
2 Instituto de Geociências, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Belo Horizonte, the capital of the state Minas Gerais (Brazil), has been considered by
the UNO as one of the cities of South America that will be a megacity with more than
ten million inhabitants by the middle of this century. As the city already does not support
its growth to the south because of restricted access and accentuated relief, the future
tendency will be to expand towards the north. The newly built highway between the
international airport Confins 40 km north of Belo Horizonte and the city itself is
accelerating the urbanization of the neighbouring municipalities, especially as tax
reductions for industrial plants and easy access are favouring rapid development of the
region. The urbanized area, including the area in process of urbanization (periurban
area / bare soil), increased from 13% in 1987 to 20 % in 2002. In the same time, the
forested area decreased from 45 to 36%. The analysis of geo-resources and geohazards
is essential for the sustainable growth of every city, even more so if the city is
growing very fast into a fragile environment as is the case in Belo Horizonte.
Lagoa Santa, a city of 45000 inhabitants lying at the triangular lake north of Belo
Horizonte, is the biggest city affected by the trend towards urbanisation due to the new
highway. The prices for real estates in its municipal area are rising even before the
highway is finished. Still, Lagoa Santa is situated on highly erodible siltite hills and
severe erosion with has formed many gullies is already threatening the infrastructure.
Also in the neighbouring valley of the Riberão da Mata whose alluvial plain serves both
as sand, clay and gravel resource and as one of the very few plain building sites,
concentrated overland flow resulting from sealed areas increase the risk of inundations.
Fig. 1: Belo Horizonte and the study site in its northern periphery.
In the whole northern periphery of Belo Horizonte which includes the municipality of
Lagoa Santa, a general erosion index has been calculated, regarding the erodibility of
soils as well as topography: The erodibility of soils has been estimated on behalf of the
lithology in the area and whether laterite crusts exist or not. While the Archean
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