Modelagem hidrológica e análise da eficiência de reservatórios de detenção como medida de controle em bacia urbana

Abstract

This study approaches the impact of the urbanization on the water resources in an urban catchment, aiming at understanding the hydrological processes in there, and pointing for solutions against flood damages. Flooding is one of the main ambient problems caused by urban occupation, and the drainage system implemented in the catchment must contain the risk of occurrence of this phenomena. Hydrological modeling is a very useful tool to analyze different scenarios in the catchment, assisting environmental managers in the stormwater management decisions. This research proposes to bring up results that collaborate in the stormwater management study, besides the appointment of solutions to the catchment study area, simulating the operation of detention reservoirs as a stormwater management facility. The study was realized in the urban area of the Cancela Basin, to the areas covered by the CACISM fluviographic station, with 2,7 km², and the Cancela fluviographic station, with 4,95km². The SWMHYMO model was used as tool for the calibration of 40 events for the CACISM station, and 11 events for the Cancela station, using a discretization of 1 minute for both stations. Besides the events calibration, the continuous calibration of a 1 year time period of data, with a discretization of 5 minutes, was performed to the CACISM station. The model, however, showed a limitation in drowned situation for the culvert simulation, and to simulate this situations, the methodology present in Gaia (2014) was adopted, in this study, the author analyzed the historical, classic and actual approach of the culvert equations. The average Nash- Stucliffe efficiency index (CNS) got in the event calibration for the CACISM station was 0.75, decreasing to 0.50 in the validation, values that increased to 0.77 and 0.66 in the calibration and the validation, respectively, when the events with anomalous values were excluded. For the Cancela station, the average CNS index got was 0.85 for the calibration and 0.46 for the validation, increasing to 0.76 with the exclusion of an anomalous event. In the continuous modeling, the CNS index got for the calibration was 0.74, and 0.79 for the validation. With the model parameters calibrated, the critical points of inundation in extreme events could be identified in the basin, and the reservoir routing could be simulated as a stormwater management facility. The critical event of the data series, that reached a recurrent interval of about 64 years, 8 months and 11 days was used to evaluate the volume of the reservoirs, concluding that two reservoirs would be necessary, with 31,665.00 m³ and 24,595.00 m³ in the on-line situation, decreasing to 24,470.00 m³ and 20,600.00 m³ in the off-line situation, representing a decrease of 57.94% in the peak flow. Besides, the efficiency index got with the model points for it positive applicability to the catchment, validating the results, and concluding so that the research collaborates for the hydrological modeling, and stormwater management study in urban areas.