Summary:

One of educating activities aims is characteristic, grouping and classifi-cation of phenomena, objects and behaviors. Division of some group of objects, subjects or devices into subgroups plays very important role in standardization operations. A result of objective analysis of the tested set structure is the possi-bility to determine mutual relations between elements which create the set. This is particularly important in hydrology, especially in modeling of processes that oc-cur in catchments or drainage basins. Relations between catchments characteris-tics and hydrologic models’ parameters are extremely important in estimation of parameters of statistic distributions, evaluation of changes in catchments and prognosis of hydrological phenomena in uncontrolled catchments. The knowledge of the spatial distribution of hydrological characteristics is more and more often used in water management, especially during water management plans creation in the area of catchments or drainage basins. In order to estimate interesting hy-drological characteristics in uncontrolled catchments the method of regional fre-quency analysis is applied, which allows to allocate areas of homogenous type of the analyzed phenomenon. To allocate the homogenous areas methods of two or more variables regression, cluster analysis, kriging or artificial neural networks are applied, too. Grouping methods base on the internal division criterion, which is mathematic definition of similarity between the objects. The appropriate pro-cedures of grouping create sets of objects. In practice distances between the sets are defined with the following methods: single linkage, full linkage, pair group average, weighted pair group average, center of gravity, weighted center of grav-ity and Ward method. The aim of the work is the analysis of possibilities of clus-ter analysis method appliance to allocate homogenous areas regarding the flood index and selected physiographic characteristics of catchments in Vistula River drainage basin. The initial material was the hydrological data and chosen physi-ographic characteristics of rivers in Vistula River drainage basin. Data from 33 catchments of rivers which are direct Vistula inflows was used. The analysis took the following physiographic characteristics: the area of catchment (A) and its average height over the sea level (Hav), catchments inclination (I), length of the main stream (L) and the catchments’ shape factor (Rf). The analyses have shown that the best grouping results were gained using the Ward method, in which six homogenous catchments were allocated regarding the flood index, area, average height over the sea level and inclination, main stream length and the shape fac-tor. In each of the set homogenous areas analyzed physiographic factors influ-ence the flood index in the different way and to the different degree.