Regional flood frequency analysis: evaluation of the design flood for 5 Brazilian dams

Engineers in the water resources field frequently have to estimate the probability of exceedance related to a determined flow value at a chosen river cross-section, also known as flood quantile. This estimation is necessary in order to proceed with the design of different structures, such as dam spillways, and for other functions, such as risk management. The accurate estimation of the flood quantile of interest is not an easy task, as return periods of interest usually require a data record that exceeds the length of the available gauging record at the site of concern. In order to accurately estimate flood quantiles at a given river cross-section, the regional flood frequency analysis (RFFA) is often used, allowing to compensate the lack of data by gathering information from other gauging stations which are supposed to be similar to the target station. The present Thesis deals with the evaluation of the 1,000-year flood quantile for five Brazilian dams based on a RFFA. The five studied dams are: Cachoeira Dourada, Ponte Alta do Bom Jesus, Quatiara, Poxoréo and Volta Grande. An index-flood method is applied as a usual approach in RFFA. The Region of Influence approach is then considered in order to define a homogeneous pooling-group of sites for a given target site. Overall, 79 gauging stations are examined for the evaluation of the 1,000-year flood quantile.