Abstract
ABSTRACT Hydrologic studies are essential for the design and safety of hydraulic structures. In the past, a number of empirical equations were developed to represent relationships between drainage areas and observed peak discharges. Although these empirical equations have not been used frequently to study peak discharges due to the use of more detailed and sophisticated analysis, they can be used to estimate reference values, especially in ungaged sites. The objective of this paper is to assess peak discharges observed in many regions in Brazil, estimate the 10,000-year discharges according the Guia para Cálculo de Cheia de Projeto de Vertedores from Eletrobrás and compare them to the Creager envelope curves. In this study we used the records of naturalized discharges for the period of 1931 to 2012, for 131 hydroelectric projects selected in the main river basins in Brazil, using the official data published by the Operador Nacional do Sistema Elétrico (ONS) for the Sistema Interligado Nacional (SIN). The results presented in this paper show that it is possible to use the Creager envelope curves as a preliminary estimate of the design floods in Brazil. Generally, values of the Greager C coefficient between 60 and 100 are recommended for a preliminary estimate of a range of maximum discharges within drainage areas bigger than 10,000 km2. The results can be used in the preliminary estimate of maximum discharges and 10,000-year discharges for sites with no data using C values obtained from areas with enough data in the same river basin and with similar physical characteristics.
Highlights
Hydrologic studies of floods are essential for the dimensioning and security of hydraulic works
Empirical formulas were developed to describe the relationship between drainage areas and observed maximum discharges
The study was based on the following steps: selection of locations with available consistent historic series of daily discharges: definition of criteria for selecting series of maximum daily discharges; frequency analysis of maximum daily discharges and estimation of 10,000-year values; and assessment of the behaviour of observed and 10,000-year floods in Brazil in relation to the envelope curves defined by Creager, Justin and Hinds (1945)
Summary
Hydrologic studies of floods are essential for the dimensioning and security of hydraulic works. The envelope curve of Creager provides an estimate of maximum expected discharge as a function of drainage area, and is based on a large number of exceptional floods in the United States and some in other countries, including the Amazon River.
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