The study was aimed to verify the Punzet formula to flood frequency (Qmaxp) in two rivers: Lepietnica in cross-section Ludźmierz and Koprzywianka in cross-section Koprzywnica. The verification was aimed to assess the usefulness of the Punzet formula in hydrological calculations, in relation to current hydrometric data. The data- the long-term observation records of the annual maximum floods (Qmax) from the period 1980-2013 - were obtained from the Institute of Meteorology and Water Management - National Research Institute in Warsaw. The obtained data were evaluated considering their homogeneity and independence using Mann-Kendall-Sneyers test. Qmaxp was calculated using the statistic method of the Pearson III type distribution with maximum likelihood method of estimating the parameters of distribution.
The calculations Qmaxp for the Lepietnica River obtained with statistical methods and the Punzet equation, where Qmax50 was calculated with the Carpathian formula, have shown that differences between the results were insignificant. However, the calculations for the Koprzywianka, where Qmax50 was calculated with the Punzet formula for non-Carpathian plain catchments, have shown substantial differences between the results obtained through empirical and statistical methods.This justifies the need for verification and updating the Punzet formula to calculate Qmaxp in non-Carpathian plain catchments of the upper Vistula basin.