No 3 (2019)

ARTICLES
Morphological diversity of channel patterns of braided rivers
Chalov R.S.
Abstract

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 2nd and 3rd 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.

Geomorphology RAS. 2019;(3):3-18
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Postglacial seismogenic deformations of an esker in the Northern Karelian Isthmus (south-east Fennoscandia)
Shvarev S.V.
Abstract

The research area is located in the Northern part of the Karelian Isthmus between Lake Ladoga and the Gulf of Finland of the Baltic Sea. The terrain features are closely related to the tectonic structure of the crystalline basement, partially covered with thin deposition layer of the Last Glaciation and Holocene mostly. Accumulative forms are rarely but strongly correlated with the tectonic structure also. Most expressive features of accumulative topography are esker ridges that stretch for tens of kilometers. Analysis of eskers spatial distribution shows their close connection with the structural plan of the crystalline basement. One of the ridges under study was described in three sections where a lot of deformations in soft sediments, accompanied by deformations of the esker’s topography (in one case) were found. The nature and stratigraphic position of deformations indicates their appearance during the period of existence of the Baltic Ice Lake after the retreat of the ice sheet. Post-sedimentary deformations were accompanied by partial re-deposition of sedimentary strata. Deformations are represented by several types and generations. The ensembles of faults and fold deformations in the esker deposition kinematically connected with each other and coinciding along the strike with the structural lineaments demonstrate the influence of the activated tectonic structure to the formation of the sedimentary cover. The conjugation of normal and thrust faults, the presence of several “event horizons” with traces of liquefaction testify to the seismotectonic genesis of deformations and several strong earthquakes that occurred at different stages of the existence of the Baltic Ice Lake in the period 13.0–11.6 thousand years BP.

Geomorphology RAS. 2019;(3):19-35
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Scientific Research Methods
Use of singular spectral analysis in geomorphological studies in the Southern Primorye and the Peter the Great Bay of the Sea of Japan
Samchenko A.N.
Abstract

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.

Geomorphology RAS. 2019;(3):36-45
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Short communications
On the hydrological role of the relief in the southern part of the Russian plain
Koronkevich N.I., Dolgov S.V.
Abstract

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 19th 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.

Geomorphology RAS. 2019;(3):46-56
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Modeling the dynamics of a sand beach governed by the wave and underwater bar interaction
Kuznetsova O.A., Saprykina Y.V.
Abstract

Effect of bar position on underwater profile of sandy beach was studied at the timescale of one storm using the xBeach numerical model. Beach profiles were extracted from the bathymetry of the Shkorpilovtsy beach (the Bulgarian coast of the Black Sea). Computed results were verified by field measurements. The largest shoreline retreat occurred in the first hour of a storm. For the chosen wave regime (largest wave height 1.5 m, wave period 10.5 s), an equilibrium profile was formed after 6 hours. The resulting profile contained an underwater terrace with the slope close to that of the theoretical equilibrium profile. It was shown that the position of the underwater bar affects the shoreline retreat rate. The smallest and the largest shore retreat occur if bar crest is located at a distance about 0.7–0.8 and 0.5 of the deep water wavelength, correspondingly. It was found that the shoreline retreat depends on the height of infragravity waves and mean wave period: the smaller mean wave period and the higher infragravity waves near the coast, the smaller is the retreat of the coastal line. Distance of seaward sediment transfer is directly relates to the height of large waves near the shore.

Geomorphology RAS. 2019;(3):57-67
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Factors and criteria of the morphostructural zoning and the main types of morphostructures of the North-West of the Black Sea
Pasynkov А.А., Vakhrushev B.A.
Abstract

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.

Geomorphology RAS. 2019;(3):68-82
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Lake Onego development in the late glacial assessed with the use of GIS technologies
Subetto D.A., Potakhin M.S., Zobkov M.B., Tarasov A.Y., Shelekhova T.S., Gurbich V.A.
Abstract

The GIS-based reconstructions of Lake Onego development in the Late Glacial (14500–12300 yrs ago) were performed. Reconstructions have been based on the deglaciation model of the Lake Onego depression, digital elevation model of the lake depression, SRTM model of its drainage basin and on the data obtained from the palaeolimnological studies of numerous lake sediment cores. This allowed us to distinguish six main stages of the lake development for which a series of detailed schemes were produced. 1. Formation of the ice-dammed lake as a result of the ice sheet retreating (14.5 cal ka BP). 2. Emerging of the southern and central parts of the lake basin from the ice cover (14.0 cal ka BP). 3. The maximum development of the proglacial lake (13.3 cal ka BP). The lake area in this period was around 33 000 km2. 4. The first regression (13.2 ka BP). 5. The second regression (12.4 ka BP). 6. The third regression (12.3 ka BP), when the area of the lake dropped to 18 000 km2. We created detailed digital maps of the main stages of Lake Onego development during the Late Glacial and calculated the spatial parameters of the lake. The quantitative data obtained in this study would be used in estimation of the volumes of the lake and outflow discharges in the past. Maps are available in electronic form.

Geomorphology RAS. 2019;(3):83-90
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Holocene environmental changes in the Northern Khibiny mountains (Kola Peninsula) inferred by diatom analysis of lake sediments
Shilova O.S., Romanenko F.A., Kolka V.V., Denisov D.B.
Abstract

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.

Geomorphology RAS. 2019;(3):91-101
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History of Science
Andrey Aleksandrovich Grigoryev (1883–1968) — prominent geomorphologist and organizer of geomorphology in the USSR in 1920–1930s
Chichagov V.P.
Abstract

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 20th century.

Geomorphology RAS. 2019;(3):102-112
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