Comparação de métodos para determinar o volume de armazenamento em pequenas bacias de contenção: um estudo de caso em Francisco Beltrão - PR

Abstract

The development of conventional urban drainage systems is based on the concept of draining precipitated water as quickly as possible. Projects based on this concept had, as an immediate consequence, an increase in flooding downstream, due to the canalization reducing the water concentration time. A potential solution measure, in this scenario, is the adoption of containment basins to control floods. Retention basins are reservoirs designed to intercept and temporarily retain a volume of rainwater and release it in such a way that peak flows are reduced, preventing the occurrence of floods. The present work aims to compare two methods for sizing a containment basin, starting from the hydrograph obtained by the Soil Conservation Service method and then calculating the Simplified Triangular Hydrograph method comparing it to that obtained by mathematical modeling with the HEC-HMS software. Considering that the simplified HTS method is indicated for small river basins. Three different scenarios were adopted with recurrence times of 25, 50 and 100 years. The SCS method was used to develop the project hydrographs and determine the reservoir's influent flows. While effluent flows were estimated according to the collection structure already implemented at the study site. The study was applied in the Marrecas neighborhood, located in the city of Francisco Beltrão, which is marked by the process of flooding that occurs over time. When comparing the results assumed as reference values, the volumes obtained in the damping performed by HEC-HMS, as it is a method with a greater range of factors considered in its model, bringing the simulation closer to reality. Thus, the volumes obtained by the HTS method were around 28% smaller than those from the modeling, presenting an average difference of 4,740 m³ between the methods in the three scenarios. This suggests that although the HTS method is simpler, faster and less expensive, it may underestimate the volume required for containment basins compared to more complex spatial modeling. However, despite this limitation, the HTS method can still be useful in situations where absolute accuracy is not critical, or where the resources to perform full spatial modeling are not available. In conclusion, this study hopes to contribute to choosing the appropriate method for different application conditions. It should be noted that there is currently a significant gap in studies in the area of urban drainage, therefore, carrying out research in this vital area is strongly encouraged.