Flood Frequency Analysis Using Variable And Fixed Kernel Density Case study: Dez river

Traditional method in flood frequency analysis is parametric approach. This method lacks the ability to describe multimodal and Asymmetric densities. In order to overcome this problem¡ the nonparametric models can be used. Two methods of nonparametric approach are: fixed and variable kernel density. In fixed kernel density method¡ the probability density function can be estimated by selecting a kernel function and optimal bandwidth and in variable kernel density method the probability density function can be estimated by selecting a kernel function and bandwidth at each observation point. Cross validation and Rule of thumb are common methods for estimating the optimum bandwidth. In this paper¡ besides mentioned methods Plug in bandwidth method is used and nonparametric flood frequency analysis is performed using annual maximum flood data of the Dez river. Finally results were compared with parametric method. According to RMSE¡ it is concluded that plug in bandwidth is the most accurate method for estimating optimum bandwidth. As well as Nonparametric method based on variable kernel density is more accurate than fixed kernel density and both types of these models are more accurate than LP3 distribution.