Summary:

In the article, analysis coefficient of reduction of annual maximum flows for San, Wisłok and Wisłoka catchments was made. Basis of executed analysis was data about annual maximum flows from years 1984-2009 got from IMGW PIB in Warsaw. Data were verified in view of its homogeneity and then, values of maximum flows with probability of exceed were calculated, based on Pearson III type distribution with use maximum likelihood method of parameters calculation. Values of coefficient of reduction of maximum flows were calculated with use following methods: segment values, correlation and dimensionless charts.
Analysis showed, that values of coefficient of reduction of maximum flows were statistically significant depending on used method (the highest values were got for method of outliers values). Value of coefficient of reduction depends on the probability of flows -increases with probability increasing. In practical hydrologic calculation, in analyzed area, coefficient of reduction of maximum flow calculated with use method of segment values should be used, also it should not be taken values of n coefficient amounting 2/3 given by Dębski.