Definição da equação IDF a partir de dados de pluviômetro automático - Teresina/PI

Abstract

The Intensity-Duration-Frequency (IDF) curves are tools used to quantify rainfall intensity at a given location, correlating the main characteristics of intense precipitation events. Defining an IDF equation that accurately represents the local pluviometric reality is essential, as it provides greater precision in the planning and design of hydraulic works, resulting in more efficient drainage systems adapted to regional climatic conditions. This study aims to obtain the IDF equation for the city of Teresina based on the analysis of historical precipitation series recorded by automatic rain gauges, using two methodologies: that proposed by CETESB (1986) and that by CPRM (2007). The partial duration series was analyzed by rainfall duration, with return periods calculated and plotted on bilogarithmic paper, as indicated by the CETESB (1986) methodology. In the CPRM (2007) method, the Poisson distribution was applied for all durations, adjusting the recurrence intervals to annual exceedances. The resulting plots allowed extrapolation of the return periods of interest and determination of the maximum intensities for all durations. The adjusted parameters of the CETESB (1986) and CPRM (2007) equations were found to be of the same order of magnitude, with only minor differences - the largest deviation being 48.52%. Both curves showed similar behavior, although the CETESB curve presented slightly higher values. On the other hand, when compared to the equation from Teresina’s Urban Drainage Master Plan (PDDrU), the obtained intensities were significantly higher for all return periods, suggesting an underestimation of intense rainfall in the PDDrU, which could justify the current inefficiency of the city’s drainage systems.