Flood Flow Frequency Model Selection Using L-moment Method in Arid and Semi Arid Regions of Iran

Statistical frequency analysis is the most common procedure for the analysis of flood data at a gauged location that in first step it is needed to select a model to represent the population. Among them, the central moment has been the most common and widely used, and with the using of computers, the application of the maximum likelihood has increased. This research was carried out in order to recognition of suitable probability distributions with pervious common methods. In order to investigate of suitable probability distribution for flood flow, using L moment method through the existing hydrometric stations in the region, 17 hydrometric stations were selected for peak discharges data studies. According to results of this research for peak discharge, LP3 distribution and ordinary moment method, P3 distribution and L-moment method, LN2 and LN3 distributions and ordinary method have been suitable distinguished for 53%, 35%, 6% and 6% of stations, respectively. We concluded that L-moment method is suitable to determine peak series probability distributions in the Iran central plateau and P3 is the best probability distribution for modeling peak series in this region.