Estimativa da precipitação máxima diária anual e equação de chuvas intensas para seis municípios da região sul do Brasil

Abstract

Hydrology plays an important role in studying the hydrological events used in the design of engineering works. For locations where information on rainfall behavior is not available, it is often necessary to extrapolate from data available in nearby localities, following the methodologies defined in the bibliographies and specific standards. The present work had as objective to study the behavior of different estimators of parameters of the generalized extreme value distribution of probability (GEV) against the Gumbel distribution, more commonly used. In addition, the present difference in the application of daily rainfall breakdown coefficients proposed by CETESB (1986) and the coefficients recently presented by Basso et al. (2016). For the estimation of probability quantiles using the aforementioned estimating methodologies, the annual maximum daily rainfall series of 6 cities located in the Southern Region of Brazil were used. As a result, significant differences in estimates for recurrence times of up to 100 years were not identified in stations with more than 65 years of rainfall records. As a result of the application of different coefficients of disaggregation, it was verified that the coefficients proposed by Basso et al. (2016) generate higher rainfall intensities than CETESB (1986). With the exception of Irai, all other municipalities, applying both methodologies of disaggregation, presented intensities higher than those defined by NBR 10844 for times of return equal or superior to 5 years. In addition, it has been observed that dividing the IDF equation into two parts results in smaller estimation errors for the fraction valid for rains over 60 minutes in duration.