By: N. Vivekanandan
Scientist-C, Central Water and Power Research Station, Pune,
Maharashtra, India
Estimation of peak flood discharge (PFD) for a given return period is required for the design of culverts, dams, spillways, bridges, flood protection and soil conservation work, etc. The dimension and capacity of the hydraulic structures will also depend on design flood magnitude that may have some uncertainty due to model error. This paper presented a study assessment of uncertainty on estimation of PFD using LN2 distribution for river Tapi at Sarangkheda site. For this purpose, the annual maximum discharge (AMD) series with different data length (say, series with 50 years data (DS1), series with 70 years data (DS2) and series with 82 years data (DS3) was generated from the observed AMD data (1941 to 2022) of Sarangkheda and used for estimation of PFD. Goodness-of-Fit (GoF) (viz., Chi-Square and Kolmogorov–Smirnov  tests and model performance indicators (viz., correlation coefficient (CC) and mean absolute error (MAE)) was applied for checking the adequacy of fitting three parameter estimation methods viz., method of moments (MoM), maximum likelihood method (MLM) and method of L-Moments (LMO) of LN2 to the series of AMD data. The GoF tests results supported the use of all three methods of LN2 for estimation of PFD for different return periods. The outcomes of the study indicated that (i) there is a good correlation between the observed and estimated AMDs by three methods of LN2, and the CC values vary from 0.985 to 0.991; (ii) the quantum of uncertainty in the estimated PFD measured through MAE by MoM, MLM and LMO is in decreasing order when the data length increases; and (iii) the MAE computed by MLM is minimum than those values of MoM and LMO while applying the DS1, DS2 and DS3 series for estimation of PFD. The study showed that the PFD given by MLM of LN2 distribution could be used for the design of civil and hydraulic structures.
Citation:
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