Flood is the major catastrophic phenomena that induce a significant impact on human life and property. As seminal papers indicated that it is a common problem in Ethiopia; however, its frequency and magnitude had increased rapidly in the last half century. Methods were developed like Flood frequency curves in order relate magnitude of peak flow with return period. The conventional way of flood frequency analysis was applied in determining flood magnitudes of defined return periods by selecting theoretically the best fit probability distributions. The increase in flooding was a result of climate change as well as land-use change. Notable impacts of flooding were loss of human lives and properties, destruction of roads and electric systems that result great economical loss for the country. The most important part of the distribution is the tail as far as extreme flooding phenomena are best concern in water resources development and management. flood prone areas in Ethiopia were: Oromia and Afar Regional States that constitute the mid and downstream plains of the Awash River; Somali Regional State that fall mainly along downstream of the Wabishebelle, Genalle and Dawa Rivers; low-lying areas falling along Baro, Gilo and Akobo Rivers in Gambella Regional State; downstream areas of Omo River in the Southern Nations, Nationalities and Peoples Regional State; extensive plain fields surrounding Lake Tana and Gumara and Rib Rivers in Amhara Regional State .

Keywords: flood frequency, regionalization, Quantile, probability distribution, Ethiopia