Relação intensidade-duração-frequência de chuvas extremas na região Nordeste do Brasil

Abstract

The intensity-duration-frequency relations (IDF) allow the determination of project rainfall, important for dimensioning hydraulic constructions in urban and rural areas. The scarcity of pluviographic stations has led to the development of methodologies that allow the estimation of the IDF relation by means of rainfall disaggregation techniques using rainfall data. In this context, the generation of thematic maps adjusted to IDF relations, for 2,042 pluviometric stations, located in the Northeastern regions of Brazil, was sought after. Pluviometric stations that presented historic series of, a minimum of, 15 years if uninterrupted daily observations were selected. The rainfall of 1 day was disaggregated, thus allowing the generation of the rainfall series with durations o 5, 10, 15, 20, 25, 30, 60, 360, 480, 600, 720 and 1440 minutes. The Gumbel probability model was employed for distribution analysis of frequency and for the estimation of intense rainfall for the return periods of 5, 10, 25, 50 and 100 years. The Chi-Square test was used to verify the adherence of the estimated frequencies to those observed, and the Willmott performance coefficient was used to verify the quality of the adjustment of the IDF relation parameters. For all stations employed in this study, the Willmott performance coefficient presented values above 0.85, conferring a perfect adjustment of the IDF relations with coefficients of determination close to 1.0. The ascertainment of special dependents of the IDF relation parameters by means of the coefficient of variation allowed the use of the kriging technique for regionalizing for values, generating thematic maps, which give information for locations deprived of monitoring. The quality of the predicted surface was evaluated by means of analyzing the errors generated by the validation, which followed normal distribution, basic premise desired in geostatistics.