ABSTRACT

The project of the Canal do Sertão (Alagoas Aqueduct) is an important step toward social and economic development in the semiarid region of Alagoas State in Brazil. Therefore, a hydrodynamic assessment in the canal is necessary due to a complex drainage system under parameters that were not considered during the project design and execution, mainly along the reach km 67, where it is located a convergent confluence and an overchute structure. The analysis conducted in this study addressed three main aspects: i) verify possible risks to the water quality of the canal, pumped from São Francisco River; ii) evaluate scenarios with risks to the canal structure due a convergent confluence between Riacho Seco and the stream of the tributary basins, which flows over a drainage structure crossing the canal at km 67.28; and iii) analyze the water level elevation into the overchute structure, submerged during flood events, and the water level elevation in the upstream reach of the confluence of the Riacho Seco, with a length of 620 m parallel to the canal and separate by a distance of 80 m from each other, where the level may rise reaching the left levee of the canal. Thus, were assessed the potential effect of the Riacho Seco confluence with the flow discharge of the tributary basins on the overchute structure at km 67.28 of the Canal do Sertão. The analysis of the water elevation and its possible risks to the water quality and the canal structure for different flood scenarios were performed by using the hydrodynamics models HEC-HAS. It was noticed that there is an elevation of the water surface of the tributary streams in the upstream reaches of the convergent confluence and that the drainage structure over the canal do Sertão fails for flow discharge with a return period of 50 years or more, overflowing the water from the drainage system into the channel.

Keywords:
Canal do Sertão; Confluences; Convergent junction; Flood; Hydrodynamic model