Flood Frequency Analysis of Narmada River Basin in India under Nonstationary Condition

The influence of recent climate variability coupled with the intensified human-induced changes has led hydrologists to modify the flood frequency analysis (FFA) considering nonstationary behavior of time series. Presently, a case study has been undertaken to demonstrate a methodology for FFA considering nonstationarity of annual maximum flood series of six gauging sites from Narmada River Basin. Two different approaches, namely time-varying nonstationarity and nonstationarity due to physical covariates, have been applied in the present case. The influence of climate indices and the effect of reservoir constructions on the Narmada River Basin have been included as external covariates. The results indicated that the construction of reservoirs has played a major role for the changing behavior of flood series of Narmada River Basin from stationary to nonstationary. Due to nonstationarity, the return level flood value increased substantially with time and may create problems for the old structures, which were designed using traditional FFA assumptions of stationarity. The present case study can be used as an alternative to the stationary FFA for any basins worldwide, which will provide more options to the designers and managers.