Sistemática para avaliação técnica e econômica de alternativas de intervenções em cursos de água urbanos

Abstract

The urbanization process and sprawl watershed has caused environmental impacts, such as the removal of vegetation - with river erosion and silting-, and impacts on the hydrological cycle, increasing the peak flows, the frequency and magnitude of floods. Interventions traditionally employed to solve these problems, in most cases, have got worse the impacts, since they usually involve stream rectification, changes in the shape of the cross section and its covering - increasing the flow velocity and peak flow downstream, but also destroying fauna and flora conditions-, among other impacts. Solutions that provide greater environmental integration in the watercourse, using natural elements, appear as an option in face of traditional techniques. However, choosing the most appropriate technique is complex, because of the large number of criteria involved, such as environmental, hydraulic, hydrologic, sanitary, economic, financial, social, legal and political. In this context, there is a great applicability of multicriteria methods, including the use of indicators. This study attempts to address this need, providing a systematic evaluation of design alternatives, based on an cost-performance assessment, including traditional techniques and environmentally integrated technique. Performance indicators have been established considering environmental, sanitary, hydraulic and hydrologic dimensions, and indicators of cost of maintenance and operation. The indicators weights were defined through experts consultation and the aggregation method used was TOPSIS. The methodology was evaluated through its application in a case study in Bonsucesso Stream, which is part of the Ribeirão Arrudas basin, in Belo Horizonte/MG. The results confirmed the methodology applicability, robustness and simplicity, allowing classification of the alternatives, in order to assist the analist in the choice of the most suitable option to the stream evaluated.