Abstract
Intensity-duration-frequency (IDF) equations have important applications in several engineering areas such as urban drainage designs, hydrological modeling, and soil conservation projects. This study analyzes the annual maximum series and fits IDF equations for 44 rainfall stations in Alagoas State, Brazil. We adjusted parameters of the Gumbel distribution (GD) and the Generalized Extreme Value (GEV) distribution. The fitting of the observed data to the probability distributions, as well as the selection of the best distribution, were based on the Kolmogorov-Smirnov and Anderson-Darling tests at a 5% significance level. The GEV distribution with parameters obtained by the L-moments method was considered the best in 73% of rainfall stations. The estimated IDF equations showed a good fit, with determination coefficients above 0.991. The maximum rainfall intensities have spatial variation following the climatic zones of the state. The fitted equations allow estimating rainfall intensities from 5 minutes to 24 hours with a return period of 2 to 100 years, and standard error of less than 6.83 mm h-1.
Highlights
Excessive rainfall can cause agricultural losses, soil erosion, and flooding
Neither Gumbel distribution (GD) nor Generalized Extreme Value (GEV) distributions were rejected by the KS and AD adhesion tests
The GEV distribution obtained by the Lmoments method was highlighted with the best fitting in 32 (73%) historical series
Summary
Excessive rainfall can cause agricultural losses, soil erosion, and flooding. In addition to causing material damage, these events represent a major risk to life, especially in urban areas. Knowledge about extreme rainfall in a given location has great application in urban and agricultural planning, besides being used in environmental risk analysis, water infrastructure projects, irrigation, and dimensioning of engineering drawings (Deng et al, 2017; Coelho Filho et al, 2017). One must know the intensity, duration of the event, and the frequency of occurrence, which can be represented by intensity-duration-frequency (IDF) curves and equations (Silveira, 2016). These equations have great application in the hydrological dimensioning of urban drainage structures, in hydrological models for flow estimation, and in agricultural drainage and soil conservation (Marra et al, 2017; Ouali and Cannon, 2018). Some studies assess the possibility of using satellite or radar observations to obtain IDF equations (Marra et al, 2017)
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