Study of the influence of the scale of topographic maps on the values of hydrological characteristics of the river network using GIS technologies

Nowadays, GIS Technologies are used in many areas of human life, both in everyday life and scientific research. The purpose of the presented study is to identify the relationship between the scale of topographic maps and the main hydrographic characteristics of the river based on the data of observations in the Siverskyi Donets basin. The study is based on the results of the identification of the hydrographic network, which was performed based on the Open Street Map in the GIS environment of the QGIS program using the method of A. N. Straller and I. N. Hartzman. The process of identifying, describing, and analyzing subcontracted connections consists in assigning its identification order to each element of the river network, which makes it possible to compare and standardize streams. Operating with a hierarchical "tree" of the channel network, the main characteristic of which is the number of elementary, unbranched streams, it is possible to identify and analytically describe the dependencies between the detailing of the map and the main characteristics of the river network structures, such as water discharges, network density, drainage basin area, and river length. The basis for describing these relationships was the method of B.V. Kindiuk, who introduced the concept of the coefficient of the river network structure or the fractional order of the stream as a basis for approximating the above-mentioned dependencies, which allows mathematically describing the obtained functions and obtaining numerical values of empirical parameters. Using QGIS made it possible to create maps of the Siverskyi Donets hydrographic network within Ukraine based on maps of scales 1:50 000 and 1:200, 000. With their help, as well as data from a 1:100,000 map, the number of elementary unbranched watercourses was calculated, and each element of the system was identified, where the order of the main river changes depending on the map scale. The change in these indicators shows a tendency to increase the density and complexity of the river network with increasing map detail, and, as a result, potential changes in indicators of the catchment area, water runoff, and river length. The identified dependencies were expressed mathematically in the form of functions, and are also characterized by high values of the approximation reliability coefficient, which made it possible to construct a general transitional graph from the order of the water flow to the scale of the map with the corresponding values of the calculation parameters. The novelty and practical significance lie in the fact that the use of modern GIS technologies in hydrological science significantly increases the quality of cartographic data and concerning the studied object - the Siverskyi Donets River creates a database in the form of digital maps for further use in hydrographic studies. This sub‑basin has not been previously studied using the methodology proposed by B. V. Kindiuk about the influence of map scales on the characteristics of the river network structure. Such study from a practical point of view, can significantly help the work of engineers, researchers, and designers with cartographic data. This study is designed to explain the peculiarities in the scaling of river networks and propose a mechanism for a scientifically based transition from the existing map scale to the desired one within the Siverskyi Donets sub-basin.