Frequency Analysis of Rainfall Data for Estimation of Peak Flood Discharge for Ungauged Basin

N. Vivekanandan


Estimation of Peak Flood Discharge (PFD) at a desired location on a river is important for planning, design and management of
hydraulic structures. For ungauged basin, rainfall depth becomes an important input in derivation of PFD. So, rainfall depth can be
estimated through frequency analysis by fitting probability distribution to the recorded Annual 1-day Maximum Rainfall (AMR)
data. In the present study, the series of AMR is derived from daily rainfall data recorded at Una district and used to estimate 1-day
maximum rainfall adopting Extreme Value Type-1 (EV1) distribution. Maximum Likelihood Method (MLM) is used for
determination of parameters of the distribution. Goodness-of-Fit tests viz., Anderson-Darling, Chi-square and Kolmogorov-
Smirnov are applied for checking the adequacy of fitting of EV1 distribution to the recorded AMR data. The estimated 1-day
maximum rainfall adopting EV1 distribution (using MLM) is used to compute 1-hour maximum value of distributed rainfall that
is considered as an input to estimate PFD using rational formula. The study suggests the estimated PFD could be considered for
design of flood protection measures for river Swan and its tributaries joining the Beas river basin, Himachal Pradesh.

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