Equações de Intensidade-Duração-Frequência de chuvas intensas para Itabuna-BA e municípios limítrofes

Intensity-Duration-Frequency Equations of heavy rainfall for Itabuna and bordering municipalities, Brazil

Abstract

The aim of this study is to determine the parameters of the intensity-duration-frequency (IDF) equation of intense rains for the municipalities of Itabuna, São José da Vitória, Jussari, Itapé, Itajuípe, Ilhéus, Buerarema, and Barro Preto in Bahia, Brazil. The stations that had more than 20 years of coherent data and whose historical series had records from 1980 were chosen. For each station, the series of maximum precipitation of one day were obtained for the following return periods (TR): 5, 10, 15, 25, 50, and 100 years. Then, the precipitation of one day was disaggregated into smaller intervals of 5, 10, 15, 20, 25, 30, 60, 360, 480, 600, 720, and 1440 minutes. The adjustment of the IDF equation parameters is performed through nonlinear multiple regression, using the Generalized Reduced Gradient (GRG) iteration method. Twelve pluviometric stations were identified within the studied area, but three stations were discarded due to lack of data. Therefore, the data from nine pluviometric stations were adjusted, where the adjustment of the K, a, b, and c parameters of the Intensity-Duration-Frequency equation showed values above the coefficient of determination (R 2 ) of 0.997, demonstrating a very good fit to the observed data.