Fractal structure of the Kashubian hydrographic system

Abstract

Summary The research included seven drainage basins comprising of 30 sub-basins of the Kashubian hydrographic system ( ksh ), part of the Pomeranian Lake District in northern Poland. In the study maps of 1:50 000 scale were used. The river network is developing according to the Horton’s laws. The network as identified with the method of hydrographic interpretation, while its ordering was based on the methods of Horton–Strahler ( Horton, 1945 ) and of Drwal ( Drwal, 1982 ). The fractal dimension was calculated by two methods: one of them is based on the bifurcation ratio and the stream length ratio and is called geomorphic fractal dimension, and second method to estimate the fractal dimension of river networks is functional box counting (is called raster fractal dimension). Ordering of a network by the results of the Drwal method means reducing the bifurcation ratio ( R b ) and the average length ratio ( R l ) values in comparison with the analogous values obtained with the Horton–Strahler method. In the network analysis more reliable results were obtained by using Drwal’s method, as the values of the geomorphic fractal dimension obtained with the Horton–Strahler method do not always fall within the range specified for the fractal dimension, e.g. between 1 and 2. However, in the box-counting method (raster dimension) it is important to adopt as short measurement lines as possible or as many measurement line sections as possible, and not only two. The ksh river network is still in the organization stage. Its most mature stage is represented by the network of the catchments A2 ( D = 1.89), C3 ( D = 1.97) and D ( D = 1.97) on the northern slope and the network G ( D = 1.79) on the southern slope.