Structural and Morphometric Analysis of the Third-Order River Basins of the Ilimpeya-Nidym High Trap Plateau (Krasnoyarsk Krai)

A structural and morphometric analysis of small rivers of the middle reaches of the Nizhnyaya Tunguska River, draining the Ilimpeya-Nidym high trap plateau located within the Central Siberian Plateau, has been carried out using nine drainage basins as an example. To determine the morphometric characteristics of the streams, we use scenes from the FABDEM V1-2 global digital elevation model (DEM). The standard method of processing a DEM in ArcGIS Desktop 10.1 was applied as an algorithm for constructing hydrological networks, based on the morphometric analysis of river basins (Horton analysis, implemented in A. Strahler’s stream order system). Using the simplest structure of the basin organization of the Ganalchik River as an example, the article considers in detail the erosion network of streams of the third-order subbasins, which is characterized by significant variability of the main structural and morphometric indicators. For the study area, in general, a wide variation in the values of structural indices and morphometric characteristics is revealed. The deviations of the structural basin indices from modal values reflect the regional specifics of the geological and geomophrological structure of the territory and result from the layering of relief characteristic of the Ilimpeya-Nidym trap plateau, high tectonic fragmentation at elevations of 600–800 m, and the presence of traces of mountain–valley glaciation. In particular, it is found that the rivers under study have weak dissection of the river network in the middle and upper reaches, and the study area is dominated by basins with the uneven distribution of sediments along the main channel due to the middle and lower reaches, with the most stable proportion of the third-order channels. The most predominant among all third-order basins of the studied rivers are transit basins with a tendency to accumulate and accumulative basins, which account for 37 and 29%, respectively.