Intensity-duration-frequency curves in the municipality of Belo Horizonte from the perspective of non-stationarity

Abstract

The study of changes in hydrological data series is of great scientific and practical importance for water resources systems, since these are normally projected based on the assumption that time series is statistically stationary. However, such assumption may not be verified when aspects as changes or climatic variability are considered. In this sense, the present study sought to identify trends in maximum rainfall intensities in Belo Horizonte (MG) and propose, in view of the observed results, a new intensity-duration-frequency (IDF) curve from the perspective of non-stationarity. For the trend analysis, statistical tests were applied, and an adaptation of the concept “Minimax Design Life Level” was proposed to quantify rainfall intensities and fit a non-stationary IDF curve. As a result, different trends were detected, with an increase in rainfall intensities for durations equal to or less than 1 hour starting in 2000. Regarding the IDF relationships, the obtained rain intensities were up to 48% higher than current estimates. Our results emphasize the need to periodically review IDF relationships in order to avoid under or overestimation in the design of hydraulic structures.

Adaptability of the city of Belo Horizonte to changes in rainfall patterns – a case study of the Ressaca Stream Basin

“…For Scenarios 4, 5, and 6, the design hyetographs were obtained through the non-stationary IDF equation proposed by Nunes et al (2021) for exceedance probabilities (EP) of 50%, 10%, and 2%, equivalent to the return periods of the initial scenarios. In addition, considering that the scenarios were proposed over a 20-year timeline, the period from 2018 to 2038 was defined as the project lifespan (considering the time constraint for applying the equation, defined by Nunes et al (2021). In this sense, according to Nunes et al ( 2021) the design rainfall estimation was carried out by Equation 1 (GEV model).…”

“…Associated with the climate change scenario, according to Nunes et al (2021), trends were detected in the series of daily and subdaily precipitation in the city of Belo Horizonte, which justify the need to change the intense rainfall equation (IDF) for the municipality. This fact highlights the importance of obtaining continuous and quality data to have long-term hydrological observations that help in the evaluation of how the change in the atmosphere is altering the hydrological processes.…”

Methodology for IDF equation based on reduced pluviograph records

“…Thus, the quantification of these intense rainfalls in hydraulic-hydrological engineering projects is carried out by intense rainfall equations, also called intensity-duration-frequency (IDF) relationships (Faridzad et al, 2018;Dorneles et al, 2019a;Nunes et al, 2021;Abreu et al, 2022a). IDF equations relate the average maximum rainfall intensities associated with durations (d) and specific return periods (RP), based on site specific characteristics.…”

“…In the literature, there is consensus that the determination of the IDF equations should be carried out based on the rainfall sub-daily resolution rain data (pluviographic data) (Abreu, 2018;Nunes et al, 2021;Abreu et al, 2022a). However, sub-daily time series of rainfall data is generally scarce or has short periods of observations (less than 30 years as recommended by the World Meteorological Organization [WMO]), and times with no data records (Teodoro et al, 2014;Dias and Penner, 2019;Abreu et al, 2022b).…”

Assessing intensity-duration-frequency equations and spatialization techniques across the Grande River Basin in the state of Bahia, Brazil

“…Reliable rainfall estimates, at suitable temporal and spatial scales, are required for planning and designing water infrastructure for flood conveyance, and for developing strategies for flood hazard mitigation. In this sense, the probabilistic understanding on extreme rainfall at a given site or region is necessary for supporting decision making processes regarding the cost-risk tradeoff in such projects (Nunes et al, 2021). In general, for the sub daily time scales, the random behavior of extreme rainfall is summarized by Intensity-Duration-Frequency (IDF) models, which accommodate, in a single parametric form, the functional relationships among the maximum rainfall intensities and their durations and frequencies (or return periods) (Sabino et al, 2020).…”