Coastal wave processes numerical modeling for large valley-type reservoirs

The problem of modeling sediment transport and wave processes of large valley-type reservoir under non-stationary conditions of the hydrological cycle active phase (spring-autumn period) is considered. Coupled 2D sediment transport model and 3D wave hydrodynamics was considered to describe these processes, which uses the Navier-Stokes equations. The wave hydrodynamics model is applied to large reservoir of the valley type, such as Tsimlyansky reservoir. Detailed numerical experiments were performed taking into account the real coastline geometry and the bottom relief of the Tsimlyansk reservoir southwestern part. The developed complex of models and programs allows to predict reshaping the bottom relief and coastline under various hydrometeorological conditions. The results of modeling can be in demand when planning water management activities in valley-type reservoirs.

Experimental studies of the kinematics flow and bottom’s reformations in the area of bridge pier during the construction of the bridge crossing

The results of laboratory modeling of bottom reformations in the area of bridge pier crossing over water barriers are presented. The basics of hydraulic modeling are described taking into account the similarity criteria. The flow around a rectangular box (tongued-and-grooved protection of a constructed pier) is experimentally studied, the pattern of erosion if an ice-cutter device is installed in front of the box in the form of a triangle directed at an acute angle towards the flow is considered. The structure of the bottom relief in the vicinity of the tongued-and-grooved box is experimentally studied under the conditions of the bottom erosion. Two cycles of experiments were performed for different values of the flow depth and specific discharge of water. Localization and quantitative characteristics of washouts and alleviation of sandy soil in the vicinity of the streamlined design are established. It is noted that the main mechanism for the formation of the bottom relief is a horseshoe vortex at the base of the pier. A stagnation zone is formed inside the horseshoe. In the absence of an ice cutter, the main zones of soil erosion occur in the corners of the frontal bezel of the box, alluvium forms in the rear unit of the design. By installing an ice-cutter device in front of the box, the erosion zones move to the vicinity of the corners lying at the base of the triangular ice-cutter facing the box. The alluvium remains in the wake of the box. At the same time, the absolute values of the erosion depth and the height of the alluvium under installing the ice-cutter close to the box are reduced. The data of velocity measurements on the free surface and in the flow thickness are also given.

The tsunami energy radiation directivity on the example of the 1994, 2006 and 2007 events

<p>Determining the tsunami source danger is currently one of the most urgent tasks. The vast majority of recorded tsunamis are of seismic origin. Part of the energy released during an earthquake passes into the energy of the initial tsunami source. The tsunami excitation efficiency depends on a number of factors: the depth of the sea above the source and its location relative to the coast and continental slope; the shape and area of residual post-seismic bottom displacements, as well as the bottom relief directly in the zone of the seismic source; inhomogeneities of the ocean floor relief along the path of tsunami propagation (for estimating wave heights in the zone farthest from the source); time inhomogeneities of tsunami wave radiation from the source zone; non-isotropy of the tsunami radiation spectrum.</p><p>To study the tsunami source efficiency, we considered three tsunamis in the Kuril ridge region: the Shikotan tsunami of 1994, and two Simushir tsunamis of 2006 and 2007. The choice of events was largely determined by the close geographical location – all of them belong to the Kuril-Kamchatka subduction zone. Also, these events are well studied, and there is quite a large amount of data on tsunami measurements onshore and in the deep ocean. At the same time, all three sources differ in the mechanisms of the seismic focus and location relative to the coast and the continental slope.</p><p>We analyzed the tsunami wave field for three events near the Russian Pacific coast. Tsunami energy flow calculations show that frontal energy flow is mainly directed to the southeast. The flux magnitude decreases with distance from the source as a result of geometric divergence and scattering. At longer distances, the effect of refraction becomes more significant – the flow is divided into separate rays due to the focusing on the irregular bottom relief.</p><p>The radiation patterns of each source that also were created show the part of wave energy that penetrated the Sea of Okhotsk through the Kuril Straits. It is easy to indicate the effect of the capture of tsunami waves by the shelf and the formation of edge waves that carry the wave energy away from the source area along the Kuril Ridge shelf. For 2006 and 2007 events a relatively small part of the wave energy went into the captured waves, but for 1994 the initial sea surface displacement area was in the shelf zone and a significant part of the energy was transferred to the captured edge waves, radiated mainly in the northeast direction.</p>

CASPIAN REGION: ANNULAR SUB-VERTICAL STRUCTURES, POCKMARKS AND EX-POCKMARKS

A compilation of available geological and geophysical materials and published data on annular subvertical structures and fluid manifestations within a fragment of the Scythian-Turan Plate(Caspian region)is performed.In the offshore of the Northern and Middle Caspian, the following were previously identified: zones of film «slicks» of non-technogenic origin; zones of natural oil showingss; gas seeps zones; «gas pipes», «gas-water-mud pipes», pockmarks and ex-pockmarks; hilly forms of the bottom relief, confined to the centers of gas seeps. On the Buzachi and Tyubkaragan peninsulas, typical gas-water-mud hills called «salses» were previously discovered. On the territories of the Aral-Caspian region, cone-shaped relief forms – «chukalaki» are often found. These objects have traditionally been studied by geomorphologists, botanists, and soil scientists, who explained their formation by unloading ground water. An analysis of the Buzachi mud hills and Chukalaks suggests their genetic identity. Considerations have been expressed on the relevance of their study for environmental monitoring and with a view to their possible use in exploration for hydrocarbons (Part II). In continuation of the author’s study (Part III), well-known data on annular subvertical structures, pockmarks and ex-pockmarks in the Caspian basin (Caspian region) will be presented. The results of a geological and geophysical study of the first identified annular subvertical structures and expockmarks in the inter-dome troughs in the Caspian salt dome region will be presented.

Bryozoa of the northern part of Barents Sea: species composition, distribution, ecology (based on the materials of expeditions MMBI 2016–2017).

The modern data about fauna of Bryozoa in the northern part of Barents Sea are obtained. The taxonomic and biogeographic composition, distribution features of bryozoan communities, and their quantitative indicators are analyzed. 124 Bryozoa species are identified in the samples, one of which (Uschakovia gorbunoviKluge, 1946) is a new for the Barents Sea fauna. It was found that the richness of the bryozoan fauna is determined by the variety of environmental conditions and depends on the bottom relief (and related factors: soil, hydrodynamic intensity and sedimentation) and the parameters of water masses.

The features of Antarctic Bottom Water in the fracture zones at 7-10 deg. N of the Mid-Atlantic ridge

<p>Despite the fact that there are numerous estimates of the Antarctic Bottom Water (AABW) formation and transport, its evolution and distribution pathways are still debatable (Morozov E.G. et al., 2010).</p><p>The main task of this work was to identify the structure and transport of deep and bottom water mass of the fracture zones (7 40', Vernadsky and Doldrums). The research is based on new data (multibeam bottom relief, temperature, salinity, velocity) obtained during the research cruise on the RV "Akademik Nikolaj Strakhov" in October-November 2019 and WODB18 historical data.</p><p>The main result of the research is proper estimation of the AABW and LNADW transport, which takes into consideration the influence of fracture zone morphometry. Accordingly, the preliminary circulation scheme of water masses is obtained.</p>

Mathematical modeling of 3D current flows for narrow shallow water bodies of complicated forms

This article is devoted to the modeling of three-dimensional currents for narrow shallow water systems like Kerch straight. Model, which is presented in this article, is based on previously constructed 3D discrete model which has used cell filling function and rectangular uniform grids. The effect of rising free surface function has been detected in narrowest part of straight in numerical modelling. The proposed discrete models remain stable at depth differences tens of times, which is an important factor for coastal systems. Also this approach may be applied for wave evolution prediction in narrow straits of complicated bottom relief and coastal line.

HISTORY OF THE CHANNEL SYSTEMS REORGANIZATION OF THE KAMA-KELTMA LOWLAND IN THE LATE PLEISTOCENE – HOLOCENE

The analysis of the actual data on the age and stages of the channel systems formation in the Kama-Keltma lowland was based on the altitudinal differentiation of different stages of the relief and the results of radiocarbon dating of organics from the channel and floodplain facies. Late Pleistocene lake terrace is the highest level in the Upper Kama depression and Keltma hollow. The research into the geomorphological structure and age of deposited materials, with a particular focus on separate elements of the Kama-Keltma lowland erosive and accumulative relief, indicates the existence of six stages of the channel systems formation (reorganization). The first stage (end of the Kalinin stadial) is the Chepets hollow formation. The hollow was preserved after large-scale changes in the bottom relief of the Upper Kama depression. The second stage (Mologa-Sheksna interstadial) is the first Kama terrace formation. The third stage (Ostashkov stadial, 20-18 ka) is the period of the runoff hollow formation (including the ‘large terrace hollow’), which actively dissected the surface of aeolian landforms. The fourth stage (LGM, 18-10 ka) is the formation of the macromeanders of the South Keltma, Pilva, and Timsher, as well as the multi-arm channel of the Kama during alternating periods of relatively short-term warming and cooling. The fifth stage is the wide Kama floodplain formation in the Preboreal – Subboreal, represented by segmental generations. The sixth stage (modern) is characterized by the ‘straightening’ of the Kama channel – the formation of a relatively straight channel throughout the Kama-Keltma lowland.