Implications for Peak Flows of the Marrecas River Basin Due to Changes in the Brazilian Forest Code

Abstract

Changes in the Brazilian Forest Code (BFC) have soften the criteria for recovery and conservation of permanent preservation areas (PPAs), enhancing processes related to surface runoff. The aim of this study is to understand the effects of changes in PPA classification criteria established by BFC of 2012 to the detriment of BFC from 1965 considering the surface runoff response in the basin draining the upper Marrecas River valley in the flow peaks. The HEC-HMS model was used to simulate flow peaks considering three land-use scenarios, representative of the current use, adapting it to PPAs fitted to the BFC of 1965 and 2012 and seven precipitation return periods. In the proposed scenarios, the use of BFC of 2012, to the detriment of that from 1965, would imply a PPA reduction from 44.5% to 13.7%, resulting in a 22.1% increase in the average flow peaks, not representing, however, a significant reduction in the flow peaks when compared to the scenario representing the current land use. Therefore, when compared to BFC of 1965, in the Brazilian new Forest Code PPAs were reduced by 69.2%, increasing peak flows by up to 30.7%, thus minimizing the legal possibilities of flood mitigation to the urban perimeter of Francisco Beltrão, Paraná State, Brazil.

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