Regional flood frequency analysis using index flood method based on L-moments

The design of hydraulic structures require a design value expected to be observed in a given return period. Regional frequency analysis, being a statistical method, is used for this purpose. Regional flood frequency analysis provides a solution not only in estimating the design event magnitudes but also at sites having too short records and at sites where no hydrologic information is available.In this study, regional flood frequency analysis using the L-moments method for estimating the probability distribution parameters were applied to recorded series of annual flood peaks which belong to 455 stations in 26 river basin in Turkey . The index flood method based on L-moments method was used for identification of homogenous region. Generalized Normal, Generalized Ekstreme Value, Generalized Logistic, Generalized Pareto, Pearson Type 3 and Wakeby distributions were applied to homogenous regions.The accuracy of the estimated quantiles is assessed through the regional L-moment algorithm using Monte Carlo simulation. As a result, generally the Generalized Logistic (GLO) distribution is found to be suitable for river basins in Turkey.