Avaliação do sistema de macrodrenagem do trecho norte do canal Santa Maria em Aracaju-SE para urbanização futura

Abstract

Brazil has a relatively recent urbanization process with major changes dating from the 1970s. Such growth, when it occurs without parameters, or with improper parameters, leads to a disorderly development that does not necessarily brings improvements in the quality of life. Given this, the impermeabilizaton of new urban areas proves to be almost inevitable and it has consequences due to alterations on the hydrological cycle, bringing new effects; which are often disastrous. One of the cities that experiences those consequences due to the lack of proper public policies aimed at urban planning is Aracaju (capital of the state of Sergipe, Brazil), where the Santa Maria channel is located, dividing the neighborhoods Santa Maria and 17 de Março. This channel has undergone changes in its use and shape since its construction until the present day. The present study aimed at assessing the performance of the stormwater system in that neighborhood, considering the land occupation at initial and future urbanization stages, adopting the maximum occupancy rate in the region according to the current municipal laws. The dredging of the channel in 2015 was taken into account when sorting four scenarios: Scenario 1 for initial urbanization degree along with the natural channel; scenario 2 for initial urbanization degree along with the dredged channel; scenario 3 for the maximum consolidated urbanization degree along with the dredged channel, and, lastly, scenario 4 for the maximum consolidated urbanization degree including the impermeabilization of a lagoon nearby together with the dredged channel. The study was developed using the SWMM software as well as GIS and it had the analyzed length of the channel divided into eight conduits. When determining the rain duration, different types of hyetographs were elaborated adopting a 30-year return period. The results showed an impermeabilization rate of 18.00% of the studied region in the initial urbanization scenarios against 52.21% for scenario 3 and 57.02% for scenario 4. The sub-basins that had low impermeabilization rates in scenarios 1 and 2 showed the greatest variations of runoff. The sub-basin SUB-10, which had 0.93% of impermeable area in the initial urbanization, had a runoff increase of about 5.3 times after the it had been impermeabilized at its maximum. The urbanization of the lagoon region also showed a greater runoff. For scenario 2, the dredging of the channel proved to be effective while for scenario 3, the insufficiency of the dredging of the channel was clearly verified. Having the lagoon region impermeable made the whole scenario response to the precipitation more severe since it showed an increase in the maximum y/D ratio in all conduits as well as overflow was observed in the conduits 5 and 6.