Channel deformations of the Irkut river in the Tunkinskaya depression

We examine the intrasecular morphodynamics of the Irkut river within the Tunkinskaya depression and the associated partitions between depressions. An analysis is made of the changes in the channel pattern in plan, and a typization is provided for the channel processes for three time intervals: 1914, 1975 and 2015. We identified eleven morphodynamically uniform reaches of the channel: three, one and seven of them are of the adapted, incised and broad-floodplain types, respectively. The types of morphodynamical development of the river are systematized, and reaches with a different degree of deformation are identified within the most mobile broad-band segment of the river in conditions of free meandering. It is ascertained that the reaches of the braided type and the reach with sharp loop-like bends are the most stable, which is, in either case, due to the consolidation of vegetation by the high floodplain which made it possible to stabilize the movement of the channel in plan. The most strongly altered reaches are determined, where river channel displacements were accompanied by a complete change of the morphodynamical types of bends; the macrobends mainly experienced a regular breakthrough or were complicated by lower-order bends. We identified the reaches with lower-order (local) changes where the development of the bends (for the most part, of the loop-like type) changed into a new evolutionary cycle). We determined the role played by the influence of the territory’s geologo-geomorphological structure, hydrological conditions and natural processes of channel evolution on the dynamics of homogeneous reaches, and on morphological changes within them. The period of the most significant channel deformations, from 1914 to 1976, was determined, which is accounted for by an enhancement in anthropogenic pressure and by the associated increase in suspended load, and the period of decrease in the magnitude of manifestations of channel deformations from 1976 to 2015.     

Chemistry and Toxicity of Bottom Sediments in Small Watercourses of St. Petersburg

Water Resources - The article gives the results of integrated studies of bottom sediments in four watercourses in the central St. Petersburg: the rivers of Ekateringofka, Okhta, Fontanka, and...     

Channel deformations and geomorphological processes in the upper reach of the Lena River

The analysis of changes in the morphology of the Lena river in its upper reach for a 100-year-long period revealed morphodynamically uniform channel reaches and identified the dominant geomorphological processes in the valley-floor basement.     

Extreme manifestations of fluvial processes under natural-technogenic conditions

Changes in micro-relief under the influence of natural as well as technogenic factors lead to generation of elementary models of development of erosional and landslide processes, which is confirmed by examples of the development of fluvial processes occurring during torrential rainfall events on the territory of the Baikal region and the Transbaikalia. Formation of such processes under natural conditions is influenced by a larger number of parameters than in the case of experimental modeling.     

Structure of river valleys on the Lena-Katanga Plateau

Exploration data for different-order river crossings on the Lena-Katanga Plateau (northern Irkutsk oblast) were used to identify, according to the occurrence conditions of bedrocks, weathering crusts and alluvial deposits, three types of structure of river valley bottoms. In the geological evolution history of loose deposits in the valleys, six stages were determined, which occurred mostly during the Holocene. Karst lakes evolved into existence along tectonic fault lines in the river valleys at that time period which complicated their structure.