Determinação do parâmetro CN (curva número) para diferentes tipos de telhados verdes extensivos

Abstract

In the urbanization process, permeable areas are being replaced by impermeable surfaces, causing changes in the natural hydrological cycle. Impervious surfaces generate an increase in surface runoff, responsible for floonds. Among the alternatives to mitigate this problem, the role of green roofs stands out. The literature lists several benefits of the implementation of these structures, such as: aesthetic improvement, reduction of heat islands, filtering of pollutants, reduction in energy consumption in buildings and, mainly, retention capacity in rainwater runoff. Understanding the behavior of green roofs in reducing runoff is an important element for their large-scale implementation. Its ability to act in quantitative control can be translated in terms of the parameter CN (Curve Number), this parameter correlates runoff and precipitation. In the present work, data obtained from 4 different studies were gathered that evaluated different constructive systems of green roofs in the retention and flow process. For each type, retention, flow coefficient and CN parameter were evaluated. Based on the investigations, an average CN for the galocha system was found to be 84.6 for the hexagonal system, CN=85.3 and for the McDrain system, CN=88.7. As for the flow coefficient and retention, it was evaluated that the galocha system and the hexagonal system presented similar values and more efficient of CE and retention with 0.52 and 48%, and 0.51 and 49%, respectively. On the other hand, in the McDrain system, less efficient results were found with an CE of 0.57 and retention of 43% was found. The results provide parameters to support the implementation of these structures incorporated into rainwater management projects for green roofs.