Abstract
ABSTRACT The objective of this work was to propose an alternative model of IDF equation based on the disaggregation of daily rainfall. Data from the rainfall gauge station code 02649018 of the Brazilian National Water Agency from the period 1968 to 2011 were used. Several extreme event probability distributions were adjusted. Rainfall intensity with a return period of 2 to 100 years and durations of 5 to 1440 minutes were estimated using the relationships between rainfall for different durations. The four coefficients of the traditionally used IDF equation were adjusted, obtaining a sum of squares of deviations equal to 695.1 (mm.h-1)2 and standard error of estimation equal to 2.69 mm.h-1. For the model of the intense rainfall equation proposed, that relates the rain intensity and duration with the maximum daily rainfall, the sum of squares of the deviations was 33.6 (mm.h-1)2 and the standard estimated error was 0.59 mm.h-1. Including the return period in the model, we obtained squares of the deviations of 129.4 (mm.h-1)2, with a standard error of estimation of 1.16 mm.h-1. The models proposed have, besides better estimation accuracy, the advantages of facilitating the updating only by updating the maximum daily precipitation and sub serve the spatial representation.
Highlights
The knowledge of the heavy rainfall characteristics is important for the design of rainwater drainage structures, such as urban drainage works, and erosion control structures
For the 100-year return period, the largest difference was 11.9%, obtained with the Log-Normal with 3 parameters (LN3)-ML distribution. These results show that, for this data series, all distributions tested could be used to estimate the maximum daily rainfall
Based on the results obtained it can be concluded that: 1) the adhesion tests indicate that more than one probability distribution can be used for the estimation of maximum daily rainfall, one should carefully analyze the best distribution to be used; 2) The model of the proposed equation for the estimation of the rain intensity from the disaggregation of the maximum daily rainfall is given by: Figure 5
Summary
The knowledge of the heavy rainfall characteristics is important for the design of rainwater drainage structures, such as urban drainage works, and erosion control structures. For a complete characterization of the rainfall, the rain’s intensity or height, duration and frequency has to be determined (Pérez-Zanón et al, 2016; Pereira et al, 2017; Coelho Filho et al, 2017). The relations of these quantities can be expressed with the intensity rain equations or the IDF equations. The IDF equations are widely used in several hydrological procedures and are of great importance because they allow the use of computational routines in the hydrological calculations that involve the design rainfall. The use of the IDF equation is frequent in software or spreadsheets for designing urban drainage structures. Damé et al (2008) emphasize the importance of IDF equations as input data in models that make rain-flow transformation
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