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

Document Type : Research Paper


1 Assistant Professor, International Desert Research Center (IDRC), University of Tehran, Tehran, Iran

2 Associate Professor, Faculty of Natural Resources, University of Tehran, Karaj, Iran

3 MSc. Graduate, Natural Resources and Watershed Management Office, Koohrang, 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.