“…It is common because it inevitably happens with a given frequency in all natural drainage systems (Hussain & Pasha, ), and devastating for being often associated with severe economical and human losses (Hussain & Pasha, ; Rahman et al, ). Reliable estimates of flood magnitude and frequency are essential in the design of hydraulic structures such as dams, spillways, irrigation ditches, bridges, culverts, and urban drainage systems (Abida & Ellouze, ). In such cases, events associated with return periods (RPs) greater than the existing observed frequency, for instance 1,000–10,000 years and 10,000 years for spillways and dams, respectively, are the most relevant (Aydoğan, Kankal, & Onsoy, ).…”