No 1 (2019)

Suspended sediment yield is one of the objective and sufficiently accurate measures of erosion intensity in river basins. In first approximation, it can be divided into the riverbed component –r(rb), the products of vertical and horizontal riverbed deformations), and basin component – r(bas), the products of soil and gully erosion. An attempt was made to distinguish this erosion structure in the USA river basins based on the partition of suspended sediments of 224 rivers (based on the data from the US Geological Service on the average monthly water discharges and suspended sediment yields) according to the method proposed by one of the authors of the paper, as well as an assessment of its factor dependence.

The average r(rb) value for the analyzed rivers of the USA is 7.9±1.1%: for lowland rivers – 10.6±1.7%, for low-mountain (including uplands) rivers – 5.7±1.5%, for mid-mountain rivers – 4.3±1.5%. The geomorphic factor, landscape and climatic conditions within the river basins have a major impact on the suspended sediments flux ratio r(rb)/r(bas). Thus, in the USA plains, the largest average r(rb) portion is in the forest landscapes (taiga, mixed and broadleaf forests of the temperate zone, subtropical forests) – 10–15%. On the contrary, in the arid landscapes (semi-deserts) this value does not exceed 1%. Within these general trends, there are quite strong variations in the r(rb)/r(bas) ratios due to the changes in high river basin areas, agricultural activities and lithologic composition of the riverbed and floodplain sediments. There is an inverse hyperbolic relationship between the actual suspended sediment yield of rivers and the riverbed sediment portion (r(rb)), which is most manifested in the plains and low-mountains of the USA. It is also shown that a composition of the river basin parent (surficial) rocks does not play a significant role in the variability of the r(rb)/r(bas) at this scale of the study. A comparison of the r(rb)/r(bas)-estimates and their factor dependence on the US rivers with the rivers of Northern Eurasia (the territory of the former Soviet Union) makes it possible to reveal good convergence of the results obtained in these parts of the Earth, and to suggest the universal nature of the revealed regularities (in total for 684 river basins) for the whole temperate (partly for subtropical and tropical) zone of the Northern hemisphere of our planet.

The use of an unmanned aerial vehicle (UAV) with a photo-video camera in the shore of Lake Ladoga in 2015 showed its high efficiency for studying the geomorphology of the shores. A number of features of the morphology of the Ladoga shores in several areas have been revealed, including: the structure of the submerged coastal slope on shallow banks has been refined; the main fracture systems for a number of crystalline massifs on the northern shore of the lake have been determined. A new map of the Ladoga Lake shores types was created. The integration of the method of terrestrial and aerial geomorphological surveys with subsequent generalization of the results to space survey data is an effective addition to the method of geomorphological studies of the coasts.

Possibility for landscape pattern modeling was demonstrated for areas characterized by active ground subsidence in the eastern part of the Middle Russian Upland (the Kursk Region) as a case study, based on the mathematical morphology of landscapes technique. Applicability of this approach for the case study area was substantiated. The investigation revealed objective difficulties caused by complex morphological pattern of the area compared with the previously proposed canonical models (in terms of the landscape science). The  simultaneous occurrence of morphometrically and physiographically different types of the depressions was considered with subsequent analysis of particular types. Significant differences in morphometric characteristics of forested and meadow depressions as well as low areas without morphologically distinct depressions (so-called “wet spots”) have been found by the application of the variance method. Correspondence of the meadow depressions mean radius sample distribution with log-normal distribution and of the “wet spots” one with normal distribution have been revealed. The forested depressions mean radius sample shows correspondence with both types of statistical distributions.

The estimates of water flow in the paleorivers with known paleochannel morphometry was compared with basic hydrological and climatic indicators found by paleogeographic analogy in the regions-analogues, determined by fossil flora analysis from the Holocene (from the present to 10 thousand years ago), the Late Valday (17–18 thousand years ago) and before the Eemian (~140 thousand years ago) deposits. Comparison of annual runoff depth obtained by regime equations and equations of hydraulics and taken from the hydrological maps in the regions-analogues, showed quite satisfactory compliance. Relative error of comparison for the different objects is in the range of ±11–23%, which does not exceed the average error of water flow estimation by each of these techniques separately. However, the error of ±20% is significant and geomorphological approaches can be applied only for the cases of sufficient changes in the water flow of ancient rivers (twice or more) and for long-term periods. Nevertheless, the use of geomorphological approaches and the method of paleogeographic analogy is now one of the main ways to reconstruct water resources in the past and to construct water resources scenarios for possible future climate changes.

The studied reach of the upper River Ob is quite complicated in the morphological aspect and characterized by very low channel stability and high discharge of sand load. Unconstrained conditions for lateral channel migration promotes active channel deformations not only at long-term scale, but also seasonally. Channel deformations contribute to the transformation of the channel and its morphodynamic type in time. The upper River Ob is intensively used as a water course, so any reorganization of the channel and river islands should be taken into account to support navigation.

Morphometric and morphodynamic analysis of the islands made it possible to develop their morphological classification. Morphometric parameters of islands, being associated with the characteristics of the channel itself, are one of the main classification features. Empirical relations were obtained that link the dimensions (L_o, B_o) and shape of islands (L_o/B_o) with the morphodynamic channel type and its stability, the degree of branching of the channel (number of islands n_o per 1 km of channel length x). The features of island dynamics are also determined by the morphodynamic type of the channel and are associated with the morphometric characteristics of the islands themselves and their position in the channel, which determines the transgressive, regressive and transverse shift or their stable position in time.

Fifty years ago, in the autumn of 1968, experiments on interpretation of the first Soviet global space image made by ‘Zond-5’ automatic spacecraft and of American space images from Gemini III, IV, V piloted spacecrafts were carried out for the first time in the USSR. The aim of these experiments was the study of possibilities to use satellite images in geomorphology and geography.

The first results demonstrated high value of space images for geomorphological research for the studies of morphostructures and morphosculptures of various genesis, the discovery of a 2500 km long lineament in Sahara; real time-related transitive borders of latitudinal landscape zones in Africa were indicated for the first time. It was suggested that satellite images could be applied for the studies of various geological structures, seismicity, volcanic activity, global and regional zones of jointing as well as for thematic mapping. Thanks to these studies a new Department of Satellite-related Geography was established at the Institute of Geography of the USSR Academy of Sciences. Later on, studies were carried out at the Institute’s Department of Satellite-related Geography in order to find application possibilities of TV multispectral scanned and photographic satellite images for thematic research and mapping. The first conclusions were confirmed in the course of further studies in the field of aerospace remote sensing in Russia and abroad; their results were summarized in two fundamental atlases published under the auspices of the Institute of Geography of the Russian Academy of Sciences (IGRAS): “Resources and Environment World Atlas” (1998) and “World Atlas of Snow and Ice Resources” (1997). Up to date, methods of aerospace remote sensing continue to be applied successfully at IGRAS for geomorphological studies and for resolving of environmental problems in physical and human geography.