Landscapes Forest and Global Change - ESA - Escola Superior ...

V.D. de Campos & S M. Carvalho 2010. Risk areas to flooding in the Hidrographical Basin of Arroio dos Pereiras
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The flood occurred in 1993 that also had large proportions was considered atypical, not
by months of occurrence (in September) which is usually rainy, but by being accompanied by a
big hailstorm, which caused an average accumulation of 60 cm of ice, reaching especially the
city center and within the municipality. The material losses that occurred due to this
phenomenon were immense, reaching 100% in some cultures, hundreds of homes lost their
roofs, fall of gas stations covering, industrial sheds, among others (Folha de Irati Newspaper,
1993).
Due to the magnitude of the event (heavy rain with hail), there was still clogging of the
storm drainage network of rivers and the river bus by debris, trash, sediment and by the hail
itself, which, coupled with the subsequent melting of the ice, led to a great flood, increasing the
losses and the number of homeless. According to the local press (Folha de Irati Newspaper,
1993), which covered the event, residents said in the same day (September 29, St Michael's
Day), 30 years ago, the same event occurred.
Figure 2 - Risk areas to flooding of great magnitude
Org: Campos, 2006.
Since 1993, there were few events of flooding occurred and documented: 01/2000,
01/2002 and 05/2004 (local press). These were of lesser magnitude in the urban area and no
record in the Fire Department. The largest losses recorded from these events were concentrated
in the rural area, with losses in agricultural production, but that go beyond this study area.
Structural works undertaken by the City Hall are related to reduction of the flooding
frequency, although it is known the occurrence of a period of drier years, where the few
episodes of more concentrated rain did not represent major risks, because the level of the river
water was extremely low and the soil was very dry, with few points of flooding (Figure 3)
concentrated just after the outfall of the canalization points.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.