The purpose of the study was to compute design flood frequency by the optimized algorithm.According to the regulations of design flood frequency computation for water resources and hydropower projects

a curve fitting method of design flood frequency was presented by using the particle swarm optimization and applying the WLS

ABS

and WLS.The method was then applied to the practical computation of design flood frequency.Results indicate that the method presented in the study is better than the empirical fitting met hod.Comparing with other conventional optimization met hods

it requires a lower target function and need not compute the differential coefficient.The method is a new way of inferring statistical parameters of design flood frequency curve.