Manejo sustentável de águas pluviais em lote urbano para fins de reuso e controle de escoamento

Abstract

This research aims to evaluate the effect on surface runoff resulting from the application, in an urban residential lot, of compensatory measures for the purposes of water reuse and flood control. Real daily precipitation data and project rainfall with different durations and return times were used, as well as scenarios were proposed using an infiltration trench (scenario 2), microreservoir (scenario 3) and the combination of the rain barrel followed by trench (scenario 4). All of these scenarios were evaluated in comparison with the reference scenario, without the implementation of control devices (scenario 1). Using the Rippl Method, the rainwater storage system was specifically analyzed, having pre-defined a volume for the reservoir. Thus, the volume of rainwater used and the percentage of days in which certain levels of reservoir capacity were reached were obtained. Using the hydrological simulation in SWMM, the total volume and maximum flow rate of the runoff in the different scenarios were obtained. In addition, a cost estimate was made for each one and the economic efficiency index was calculated. The results indicate that the average annual reduction in the volume drained by storing rainwater in a 5 m³ reservoir was 40%. Regarding the reduction in peak flow, the microreservoir achieved an average efficiency of 23.6% with a standard deviation of 1.35%. The infiltration trench presented overlapping hydrographs in the rains with total precipitation starting at 67.42 mm, exceeding the hydrograph of the reference scenario in the most critical events (77.62 mm and 85.14 mm). In relation to the total volume drained, scenario 4, with the combination of techniques, reduced this volume by 49.9% to 30% in rainfall between 36.01 mm and 60.20 mm. However, it also presented overlapping hydrographs in the most critical events. The lowest cost estimate was obtained in scenario 3 and the highest estimate in scenario 2. Regarding cost-benefit, the lowest index was obtained in scenario 4 for the reduction of total volume. Therefore, it presents itself as the most efficient option, considering this variable. Furthermore, the microreservoir obtained the best performance in relation to the reduction of peak flow and the infiltration trench as the most unfavorable scenario. The duration of the rains had a greater influence on scenarios 2 and 4, both in reducing the total volume and in reducing the peak flow.