Journal of Watershed Management Research

     Due to the extent of Iran and the variety of climates in different area with variation of precipitation cause urgency obtaining to new methods for flood calculations. For this purpose necessary, efficient of new method assessment in compare of current method in different area of Iran until if suitable fitness for different region, used to calculation of flood. Two current methods for calculating of statistical parameter about flood have been ordinary moments and maximum likelihood that these methods calculate in Hyfa (Hydrological frequency analysis) and using of these results in our country. Another new method for computation of these statistical parameters in the recent years, that using in the world have been linear moments that applied by Hydrological experts for assessment in different area of the world and have been   suitable recommendation for applying of this new method. The aim of this research was assessment of efficiency of this method in the selection area of sheikh Osman watershed from Oshnavieh in west Azerbaijan province as has been assessment, efficiency of this method in this region and if suitable developed for another region of Iran. The result of this study distinguished  for five selection station in this region  and pay attention to comparison between three methods of ordinary moment ,maximum likelihood and linear moment method, the best selection method and distribution have been the Gamble distribution with  linear  moment and  extinct  efficiency of this method for calculation  of annual maximum peak floods  that distinguish more accuracy compare with current method.