Evaluation of Various Probability Distributions for Deriving Design Flood of Lower Ganga River Basin in Bihar, India

IJEP 43(3): 227-235 : Vol. 43 Issue. 3 (March 2023)

Suraj Kushwaha and Ramakar Jha*

National Institute of Technology, Department of Civil Engineering, Patna, Bihar – 800 005, India


Flood is the most destructive natural disasters. Estimation of annual maximum discharge for a particular return period T (T-year flood) at a specific location is needed for design of hydraulic structures, nevertheless it has acquired little interest. Its estimation requires appropriate distribution to avoid failure of hydraulic structures. Hence, this paper aims to identify most suitable flood frequency distribution to estimate return period discharge using annual maximum discharge data from two stations of lower Ganga river basin in Bihar. Various probability distributions were applied to fit the annual maximum discharge data. Goodness-of-fit test results show that generalized extreme value distribution gives best results at both stations. The principle of the maximum likelihood estimation method was proposed to estimate the distribution’s parameters. Using developed statistical model, design discharge is estimated at both gauging stations for 5, 10, 25, 50, 100, 200 and 500 years. Results can be very useful for further study on flood risk assessment works in the study area.


Distribution, Flood frequency analysis, Generalized extreme value, Parameter, Return period


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