In paper we perform an assessment of channel dynamics in the lower courses of Rivers Severnaya Dvina, Mezen’, Vychegda and Pechora in the past, present and future according to the development of channel forms, periodical long-term changes of water runoff and possible scenarios of hydroclimate trends in the XXI century. The study emphasized low channel stability of the northern rivers, prevalence of complex types of braided channel patterns. Fluvial response to human impacts have been evaluated, which is mostly related to channel dredging for navigation maintenance based on simplification of channel structure. Hydraulic geometry relationships have been used for predictive assessment of channel changes within braided reaches. Results indicate that the rise of braiding intensity will be related both to water flow increase through water delivery into floodplain branches and water flow decrease followed by modifications of bars to islands.

An analytical method for the preliminary assessment of the maximum volume of mudflow deposit in the North Caucasus. It involves typification of mudflow catchments by genetic type of mudflows, keeping the height of river source and the estimate of the maximum volume of mudflow deposits using the analytical expressions suggested by the authors. To receive them, the multivariate analysis was made of the relations between the maximum amount of deposited sediments (W) with the parameters such as the area of debris catchment (S), the average slope of the channel (б) and the length of the debris channel (L), for the investigated area. On this basis, the analytical expressions were obtained for the approximation of the W(S, L, б) equations depending on the genesis of the floods and the elevation of the sources. To construct the empirical equations, the mudflow statistics was used for various basins in the North Caucasus for the period of more than 50 years.

A model is suggested to predict the shoreline changes in the vicinity of coastal structures of the type of jetty, cofferdam or groin. Input data comprise the characteristics of coastal profile, dimensions of structure and the annual alongshore sediment fluxes. Shoreline contour from each side of the obstacle is described in general by a concave curve. Mean shoreline displacement A is proportional to the sediment volume trapped by a structure. Extension Λ of the area where the structure influences the shoreline contour depends on both the length of structure and the width of sediment flux. Displacement A and the length Λ tend to increase with the time t in proportion to √t . Verification of the model is based on the published data on shoreline changes due to a jetty protecting a navigational channel or a port basin. An example of model calculation is given.

The texture and structure of the alluvial deposits are the reflection of the dynamics of the river flow. The texture of the modern river alluvium is used as a measure of the velocity field in the river channel. The formulas for the calculation of the critical flow rate for the conditions of the beginning of the movement or the beginning of the deposition of particles of varying size are used for this purpose. Significant development of the theory and experimental verification of such formulas gives an opportunity for reconstruction paleo­flow velocity by measuring the size of particles in alluvial deposits. This procedure is supported by non­linearity of the relationship between critical velocities and diameters of the soil particles. A wide range of particle sizes is transformed into rather narrow range of flow rates, necessary for movement of these particles. As the result, with the correct assessment of the particular dynamic conditions of formation of the alluvial strata and efficient selection of alluvium samples, the average paleo­flow rate and (in some cases) the intensity of its turbulence can be estimated.

The methods of calculating the critical velocities provide a range of values, typically ±20–30% of the mean. Another significant limitation of this method is the lack of ability to determine other flow and channel characteristics by the use of the size of alluvium. The flow depth, which is required for correct calculation of the velocity, must be determined from the other characteristics, such as the structure of the alluvium, geometry of paleochannels, and etc. Therefore an evaluation of flow rate by alluvium size is usually complements and refines paleogeomorphological and paleohydrological reconstructions, performed by other methods.

The Shura-Ozen’ River originales in the low mountains of the northeast of the Great Caucasus and flows into the Caspian Sea in the north of the city of Makhachkala (Republic of Dagestan, Russia). The paper presents the results of its geomorphological study based on grain size and mineralogical analyzes, and geologicalgeophysical profiling. The study area is located near the aeolian-accumulative complex Sarykum, which is one of the largest isolated (i.e., formed away from deserts) aeolian sandy landforms in Eurasia. There are two principal groups of terraces differed sharply by their structure. The first group is presented by the floodplain and the high (V and VI) terraces, which are composed by overbank and riverbed alluvial   facies with normal thickness. The second group unites the terraces I, III and IV characterized by much higher thickness of alluvial overbank sands, evident especially in the terrace IV. The formation time of Terrace VI occurred before the Atelian regression (i.e. presumably in Late Girkan epoch (?), more than 44–41 cal.ka BP), Terrace V – in Early Khvalynian epoch (app. 40–33 cal.ka BP). Terrace IV formation coincided the Mid Khvalynian epoch (app. 33–(25)20 cal.ka BP), between the two deep incisions of the river correlated with the El’ton and Enotaev regressions of the palaeo-Caspian Sea. Terrace III formation occurred in Late Khvalynian epoch (app. (25)20–12 cal.ka BP), between the Enotaev and Mangyshlak regressions. All lower terraces and floodplain of the river valley are dated to the Holocene. Consequently, it could preliminarily be assumed that the Shura-Ozen’ River valley formation in its present form, as well as formation of the Sarykum sands originated from proluvial-deltaic deposits, occurred more than 44–41 cal.ka BP. (or 41-37 ka BP).

Analysis of granulometric spectra of the alluvial sediments made it possible to draw an important conclusion that the most active phase of dune formation within the aeolian-accumulative complex Sarykum took place in the epoch preceding the formation of the river terraces, i.e. after the formation of proluvial-deltaic sands, but before the valley formation. It is also assumed that the relic marine sandy spits and the pebble coastal bar (to the north of Sarykum) are genetically linked with the alluvial deposits of the terrace III and the terrace V, respectively.

Analysis of the long-term dynamics of underwater slope is necessary to identify the differences and common trends in the evolution of the different types of shores and for long-term forecast of geomorphic dynamics of coastal zone. The dynamics of a coastal profile exemplified by three different types of sandy beaches in the northern part of the Black Sea, was explored on the basis of cartographic data and individual measurements on profiles. The transformation of a coastal profile was revealed that can be associated with different budget of coastal marine sediments during the study period, with the effect of varying structure and intensity of storms and with dynamics of relative sea level due to tectonic conditions. The results prove the stability of the outer border of the dynamic zone defined by wave regime during the analyzed period.

The volcano-tectonic and tephrachronological analysis and available materials regarding the northern edge of the Emperor Seamount Chain allowed for the first time to detect the unknown circled volcano-tectonic 42-km deep-sea morphostructure known as calderoida (author's terminology) lying at –2900–2200 m depth. It is structurally complex and broken by faults into blocks of different sizes and shapes. It refers to the northern portion of the Detroit Seamount Rise (NW Pacific Ocean) and is a Pliocene horst that was formed in the Early Pleistocene at depths from –3000 to –2000 m. Its close analogues have not yet been found on Earth, but similar objects do probably exist on Venus.

An analysis of sedimentation at first-order-valley bottoms allows the gathering of a sufficiently reliable quantitative evaluation of soil losses from a catchment area for two time intervals (1963–1986 and 1987–2015) and its temporal variability. The catchment studied (Temeva Rechka, 1.13 km²) is located in the River Myósha basin, the northwestern part of the Republic of Tatarstan, Russia. Combination of methods and approaches was used for estimation of sediment redistribution for the both time intervals, including detail geodetic survey of main morphological units of the catchment dry valley, large scale geomorphological mapping, caesium-137 technique for sediment dating in typical locations of the valley bottom, calculation of soil losses using modi fied version of USLE and State Hydrological Institute (Russia) models. In addition, available information about dynamics of some climate characteristics for the period 1950–2015 was collected from regional weather stations. LandSat images were applied for evaluation of possible land use changes. Crop management coefficients were calculated separately for the rainfall and snow-melt periods using available data about crop-rotation dynamics for the last 55 years. A significant decrease of average annual soil losses from the cultivated part of the Temeva Rechka catchment was found for the period 1987–2015 compared to the period 1963–1986. Such conclusion was mainly based on different sedimentation rates in the valley bottom: for the period of 1963–1986 the average sedimentation rates were 0.92–1.81 cm per year, while for the period of 1987–2015 these rates were only 0.17–0.50 cm per year. The main reason for this significant decrease was the reduction of surface runoff caused by climate warming in the region. The warming led to a reduction of soils freezing depth before the snow-melt period, and to a decline in frequency of extreme (rainstorm) precipitation (40–50 mm per a rainstorm). The influence of agricultural activity on the erosion and sedimentation rates changeabi lity was insignificant, although some regional variation of crop rotation including a increase in proportion of perennial grasses obviously caused a decline in soil losses during warm period of year. The same trend of erosion/sedimentation rates due to mostly climate changes was identified in some regions of the European Russiaʼs southern half.