Design Flood Estimation for Narmada Sagar Project Using Partial Duration Series - A Case Study

This paper highlights details of a study for estimation of flood magnitudes of different return periods for Narmada Sagar dam(India) using the partial duration series. The comparison of the efficiencies of annual and partial flood series has been given on the basis of exact theoretical approach and approximate theoretical approach. On the basis of exact theoretical approach it is seen that the partial flood series estimate of T year flood Q(T) (for any value of λ) always has a smaller sampling variance than that of the annual flood series for a return period T less than 11 years. For any return period the partial flood series estimate of Q(T) has a smaller sampling variance than annual flood series if the average number of peaks per year(λ) is at least 1.65. On the basis of approximate theoretical approach, it is observed that in the range of λ studied (1.0 to 2.437) the sampling variance of annual flood series is smaller than that of partial flood series.