Desempenho de dispositivos de baixo impacto em sistemas de drenagem urbana em bacias tropicais

Abstract

Occasional urban drainage systems cannot keep up with rapid and uncontrolled urbanization, becoming inefficient in collecting and discharging runoff produced by intense rainfall events, causing floods to occur. Furthermore, intense rainfall will likely interfere with climate change in the long term, so there is a need to review design criteria for urban drainage systems according to expected climate scenarios. In order to mitigate failures in conventional drainage devices and ensure greater resilience of urban change in the face of climate change, a decentralized design of urban drainage infrastructure has been employed: low impact urban devices (Low Impact Development – LID) as green roofs, permeable pavements, infiltration trenches and micro-reservoirs, which objectively simulate the natural hydrological behavior of the basin to control peak flows in surface runoff. Although the hydrological benefits of LIDs have been widely documented, the potential impacts of climate change on the performance of these devices remain unknown in modeling, generating partial and isolated conclusions about the future of urban drainage devices. Therefore, this work aims to evaluate the performance of the association of LIDs with occasional drainage systems in mitigating floods in tropical urban basins. Therefore, the objective of this work is to evaluate the efficiency of low-impact devices within urban drainage systems in a tropical basin. The study was developed using hydraulic models of a tropical urban drainage basin in which the insertion of low-impact devices (rain barrels, infiltration trenches and permeable pavement) will be considered. Based on simulations carried out with the PCSWMM (Personal Computer Storm Water Management Model), it was evaluated, in comparative terms, their efficiency in reducing the total volumes and the maximum peak of runoff generated by three extreme storm events, in two locations of implementation (public and private areas) within the basin. The results obtained show that the implantation area and the way the device operates (surface or volumetric aspects) directly influence the hydrological efficiency of the devices. In this way, surface measures such as permeable pavement are more effective when implemented in larger area ratios, in addition, their responses occur in the face of more intense events. Volumetric measures, in turn, as in the case of rain barrels and infiltration trenches, are prioritized when it is unfeasible to use large areas covering the basin; In this type of device, lower performance is noticed in relation to intense events, since in this type of event the device quickly reaches its maximum capacity and begins to overflow, losing its retention capacity and directing all the water that passes through it to the return system, resulting in non-amortization of the flood. Furthermore, it was certified that the particularity of typologies within public spaces has similar efficiency to the application of a single element within private spaces, this occurs in the possible areas of implementation.