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Pluviographic measurement results from the Institute of Meteorology and Water Management (IMGW) Wrocław–Strachowice meteorological station from the years 1960–2009 constitute the basis for this paper. While conducting the statistical analysis of precipitation occurrence frequency, the criterion of interval precipitation amounts was assumed in order to isolate the intensive rainfalls from the pluviograms, which made it possible to select a number of the most intensive rainfalls in each year. A total of 514 synthetic rainfall instances were isolated, which were then were arranged according to non-increasing amounts in 16 duration intervals. This was the basis to propose the unification of the development methodology of probabilistic models for maximum precipitation amounts, reliable in the designing and verification of drain flow capacity, especially for low probability of precipitation occurrence. Maximum precipitation models for Wrocław were developed (average annual precipitation H = 590 mm).

Modeling the reliability of storm water drainage systems encounters a number of methodological difficulties, especially in the selection of a reliable rainfall scenario. Many methods for creating reference hyetographs are described in the literature. The aim of the work was the analysis of the shapes of local precipitation hyetographs and the verification of the reference shapes of rainfall hyetographs used for the drainage systems designing and modeling its operation in Poland (Euler type II and DVWK models). The research material was represented by historical records of rainfall data from the measuring station located in Jelenia Góra (Poland). Rainfall were grouped due to the similarity of physical features, using various methodologies: Huff, cluster analysis using the Ward and k-means methods. The k-means method proved to be especially useful for selecting precipitation in terms of shape hyetographs. The statistical analysis of the similarity of the rainfall hyetograph shapes was performed within the separated genetic clusters, based on the parameters of mass distributions and unevenness over time. The comparative analysis allowed for the positive verification of the Euler type II and DVWK models for the tested station.