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Geography and Natural Resources

2021 year, number 3

STRUCTURAL AND HYDROGRAPHIC FEATURES IN THE FORMATION OF SURFACE FLOW OF THE IYA RIVER SYSTEM

I.Yu. Amosova
V.B. Sochava Institute of Geography, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
Keywords: region of flow formation, region of flow transit, region of flow accumulation, stream order, structural analysis, maximum water-carrying capacity

Abstract

Data of a structural and hydrographic analysis of the Iya river system are presented for the first time. Mapping of the territory used the technique of automated identification of catchment basins in terms of the digital elevation model (SRTM DEM). A dynamic model is constructed, a water-erosion network is identified, and morphometric characteristics of streams and their basins (lengths, areas, and slopes) are determined based on the digital elevation model. Using a methodological approach based on the Horton - Strahler classification, we determined the order of the water-erosion network. Episodic, ephemeral and permanent streams were singled out on the basis of a combined analysis of the results of a dynamic modeling of the water-erosion network and the river network pattern displayed on topographic maps. Episodic, ephemeral and permanent streams include streams of the first and second orders and streams starting with the third order. Regions of formation, transit, and accumulation of flow were identified by using the structural approach on the basis of the structural regularities in the water-erosion network for the Iya basin. By analyzing the structural and hydrographic parameters for the individual partial sub-basins, it is possible to identify in more detail the conditions of flow formation in the basin as a whole. The technique based on the relationship of structural measures with average water-carrying capacity combined with a comparison of the automated processing of the water-erosion network with the channel network obtained from topographic maps permits calculations of the maximum water-carrying capacity of river systems. The specific character of the basin under investigation was the crucial factor for the individual construction of a local relation of the maximum water-carrying capacity, as a result of which the elements of the Iya river system was categorized into three groups. The predictive estimate of the maximum possible flow of the Iya river system, which the water-erosion network can transport, greatly exceeds the observed values.