No 3 (2019)

The paper presents the description of main channel types of braided rivers distinguished in the channel pattern classification produced in the Moscow State University. It is shown that the diversity of braided channels is determined by various conditions of their formation, different degree of channel stability and other factors. This diversity is defined by the number, size and shape of islands, formation of islands in channel arms, composing bifurcations of the 2^nd and 3^rd orders, presence of floodplain branches (floodplain multi-channel), symmetry or asymmetry of braided reaches themselves, development of the bends of the branches, water discharge of the branches and distribution of runoff over them in different phases of water regime, high- and low-water years, etc. Also braided channel reaches occur when cut-off meanders are formed (incomplete meandering). On the largest rivers there are braided reaches which are characterized by the development of branches in different parts of the river valley bottom and differing in their channel and even water regime. Certain features are typical for braided reaches of wide-floodplain or incised channels, for rivers with a one-sided floodplain. As a result single, conjugated, floodplain, parallel branches, one-sided, alternate one-sided braided reaches can be either simple (for example, single or parts of conjugated formed by one island) or complex, and the latter are represented by several varieties. The identification of various morphological types, subtypes and varieties of braided channel reaches is directly connected and determines the methods of channel processes management in water economy and water transport development of rivers, construction of communications through rivers, etc.

This paper presents the results of geomorphological studies carried out using the singular spectral analysis (SSA) complemented with geological and geophysical data. The SSA method was used to study the topography of the shelf and adjacent land areas in two scales. The large scale study covered the whole territory of the Southern Primorye and the Peter the Great Bay, the small scale — a major part of the Peter the Great Bay and the adjacent land in the northwest-ern direction. This technique of the relief analysis gives an opportunity to select different groups of elevations (modes in the relief), isolating them among the others, and to carry out geomorpho-logical studies based on discrete changes in the relief levels. Based on the geological and geo-physical data, it was determined that the area is located on a massive granite block. By analyzing the first (“older”) modes of the decomposition of the relief of the studied area, contouring of the massive block was carried out, and the choice of the location of the experimental hydrophysical ground was explained.

On the example of a southern part of the Russian Plain the surface slope runoff, the runoff from the hydrographic network and snow melt river runoff are considered. Based on the analysis of the data by water balance stations and the correlation of surface slope runoff values from different lands to the zonal river runoff value, the zonal values of the spring surface slope flow from separate lands located on loam and sandy loam soils are determined. Within agricultural lands there are fall plowed fields and non-plowed in autumn (stubble, layland, winter crops, perennial grasses). By the beginning of the spring flood, the soil at autumn-plowed fields is loosened and reduces the runoff, while on the fields that were not plowed in the autumn soil is compacted. In addition, the microtopography created by autumn plowing also contributes to the runoff reduction. The smallest surface slope runoff occurs under the forest. Differences in runoff increase in the direction from the southern part of the forest zone to the steppe areas. Taking into account the land composition and the mechanical composition of the soils, the weighted average values of the surface slope runoff were obtained for the period of the long-time average annual flow calculation (late 19^th century and early 1960s). It is shown that subsequently there was a decrease in the spring surface slope runoff, initially as a result of the autumn plowing increase, and more recently, mainly as a result of changes in meteorological conditions, especially during the cold season (air temperature rising, frequent thaws, increased infiltration). In the overall structure of the spring river flood, along with a decrease in the share of surface slope runoff, the share of surface runoff formed in the hydrographic network increases, and especially the flow of infiltration origin (verhovodka and underground runoff). In the steppe zone the structure of river flow has changed most significantly.

The principles of morphostructural zoning are presented on the example of the North-West of the Black Sea. Research techniques and criteria for distinguishing the morphostructural regions are discussed. In the morphostructural province of the Black Sea the following subprovinces were identified: shelf under conditions of active and passive wave action, continental slope with non-wave accumulation, deep-sea depression. Fragment of the map of morphostructural zoning of the North-West of the Black Sea at 1:500 000 scale is presented. Main morphogenetic types of morphostructures of the shelf, continental slope and deep sea basin of the Black sea are given. The characteristics of the selected morphostructural taxa are described.

The article presents the results of diatom analysis of bottom sediment cores of Lake Shchuchye located in the northern part of the Khibiny Mountains. Data of radiocarbon dating of lacustrine sediments and comparison with previously published sections of lake sediments in the Kola Peninsula suggest that the accumulation of sediments in Shchuchye Lake began during the final stages of deglaciation in the early Holocene and continued uninterruptedly until the present time. Changes in the composition of diatom associations in sediments reflect alterations in the hydrodynamic regime of the lake associated with the isolation from the Goltsovoye Lake, influence of Kunyok River runoff, evolution of vegetation and weathering processes in the catchment area. We used concentration, variety and composition of species and distinguished 8 separate zones of diatoms. Climate changes in the Holocene are reflected directly in the change of the percentage of indicator species, and indirectly through changes in pH, etc. The early Holocene rise of temperature began in this region later than in the sea coastal area. It may reflect the pecularities of deglaciation, namely — late melting of alpine glaciers. Along with the evolutionary environmental changes some catastrophic events are reflected in the sediments of the Shchuchye Lake. For example, in early stages, there the yield of big quantity of terrigenous deposits into the lake was revealed produced by mud flows and erosion from slopes covered by scarce vegetation at that time. Mudflow processes probably led to the formation of a clear interlayer of terrigenous material in the biogenic sediments in the upper part of the section.

Academician A. A. Grigoriev was the acknowledged creator of the theory of physical-geographical process, of the role of the ratio of heat and moisture in the formation of vegetation zones of the Earth, many theoretical issues of physical geography, etc. At the beginning of his scientific activity, A. A. Grigoriev was a talented geomorphologist. His scientific interests were unusually broad, he developed the theory and practice of physical geography, regional geography, paleogeography, economic geography, climatology and geomorphology, history of science. He was a talented geomorphologist and prominent organizer of geomorphological science in our country in the first half of the 20^th century.