Análise de métodos para obtenção de chuvas intensas para a cidade de Maceió

Abstract

To design hydraulic structures, it is necessary to know and to use intense rainfall equations. In this context, and knowing that the city of Maceió has old curves, this study aims to establish na intensity-duration-frequency curve (IDF) for the city of Maceió through different methods: method of relations, Bell, Chen, Righetto, BLPRM model and isozonas. The methodology was divided in two ways: with hourly data of the automatic station of the Federal University of Alagoas, and the other with daily data of the rainfall station of this same locality. In the first case, an IDF curve was generated for durations over than 60 minutes, through the adjustment to the Gumbel distribution. Intensive rains obtained by the methods mentioned above were compared to the intense rains generated by the IDF using Student's t-test, Mean Relative Error, Determination Coefficient, Deviation Ratio and Mass Coefficient Residual. The best results were obtained with the method of Chen (1983). This method was then proposed for durations shorter than 60 minutes. Joining the data above and below the duration of 60 minutes, an IDF curve was obtained for all durations. This new equation was compared to Pfafstetter’s equation and to the equation of Denardin and Freitas. The results showed that, for durations shorter than 30 minutes, the precipitation intensities of the new equation were 53% higher than the first and 47% higher than the second. This is an indicator that the old equations should have their uses reviewed, especially for microdrainage.