Hydrography Tapering and Stream Order Computing for GIS-Based Mapping

Existing tools in geographic information systems (GIS) do not allow to automatically map hydrography, taking into account both the stream’s order (so that streams vary in widths) and the flow direction (so that streams taper). The article focuses on developing a QGIS plugin for displaying hydrographic networks according to automatically determined lengths, orders and parts of the course. Rivers are divided into segments, line features are transformed into polygons (by setting a buffer with a varying width), and then the resulting objects are merged back into single streams. In this paper, automated and modified by the authors Hack’s algorithm is used to determine stream orders from vector data. To correctly visualize hydrography, the user has to select the main river and run the plugin: it will automatically determine the necessary parameters, transform the geometry and apply the style. The article discusses previous studies and the capabilities of modern GIS in the field of tapered visualization, which helps to highlight the advantages (including the reduction of time needed or accounting for the stream hierarchy and flow direction) and disadvantages (mainly scale limitations) of the developed plugin. As a result, proposed solution can be recommended to correctly display hydrography for small-scale mapping.