Efeito do método de obtenção da precipitação no hidrograma de projeto: estudo em municípios cearenses

Abstract

The design flow is an essential parameter for sizing hydraulic works. However, the number of river gauge stations is small in the state of Ceará, consequently, there is little flow data. In view of this, it is necessary to use rainfall-flow transformation models to obtain these flow data from rainfall or pluviographic data. For rainfall data, there is a need to use daily rainfall disaggregation methods to transform long-term rainfall into shorter durations. durations. Therefore, this research sought to answer the following question: What are the differences in the maximum flows of the project hydrographs resulting from the application of different methods of obtaining precipitation? Therefore, this work sought to compare the project hydrographs resulting from the use of IDF equations obtained from rainfall and rainfall data for the municipalities of Quixeramobim and Fortaleza. Analytical equations and equations obtained by the daily rainfall disaggregation methods for the municipalities were searched in the literature. Through them and with the methods of alternating blocks and the SCS (Soil Conservation Service) unitary hydrograph, they were obtained, with the aid of Excel software. and HEC-HMS, the design hyetographs and the design hydrographs, for different return times. The results demonstrated, for Quixeramobim, that the analytical equation generated peak flows, in general, higher than the other methods, this difference was between 14 to -22.1%, -27.1 to -59.6% and -31 .4% to -50.1% for the Bell methods, the relationships between durations and the isozones, between return times. For Fortaleza, the methods obtained from rainfall data had peak flows higher than those of the analytical equation, with the difference being between 60.1 to 57.5%, 11.7 to 10.2%, 24.5 to 1.7% for Bell's methods, of relations between durations and of isozones, between return times. Thus, it was found that the Bell method outperformed the flows among the daily rainfall disaggregation methods, while the methods of relationships between durations and isozones had values closer to the equation using rainfall data, but presented, in some cases, significant differences.