Dangerous ice phenomena on the lowland rivers of European Russia

The site amplification functions at 48 sites of NCR have been estimated in this study using the waveforms of locally recorded 23 earthquakes. Due to the absence of a suitable reference site in the region, the widely used horizontal-to-vertical spectral ratio (HVSR) technique has been used for this purpose. The maps showing the spatial distribution of predominant frequencies and the site amplifications at different frequencies corresponding to the natural frequencies of the different-storey buildings have been presented. The predominant frequencies in general are found to be in the range 2.5–7.5 Hz with an average of 4.4 Hz for the region having older alluvium sediments and in the range 1.1–6.4 Hz with an average of 3.3 Hz for the region with the younger alluvium deposits. The average value of the site amplifications for the frequency band 3.0–10.0 Hz is in the range 2.0–5.3 for the sites with significant soil cover, while the spectral amplification corresponding to the predominant frequency varies from 2.5 to 7.5 at most of the sites. The spectral amplification level lies in the range 2.0–3.0 for the sites with less or no sediment cover. The spectral amplification levels presented for the different-storey buildings may be used for the mitigation of seismic hazard in the region. The estimated site amplification functions may be used in the simulation of the site-specific strong ground motions and therefore useful for the evaluation of seismic hazard of a region.     

Dangerous ice phenomena on the lowland rivers of European Russia

In the Russian climate, the security of populations and economic security are often limited by dangerous ice phenomena. Not only ice-jam floods, but also some processes lead to the violation of operating conditions of various facilities (water intakes, roads, bridges) and damage hydraulic structures and shipping. Currently, rivers’ ice regime characteristics change under the influence of both natural (primarily climatic) and anthropogenic factors. Changes have been analyzed in detail on the basis of observations of 300 hydrological stations in the period from 1936 to 2013. Changes of ice phenomena hazards have been estimated. Hazard assessment of flooding caused by ice jams has been carried out for the Northern Dvina River reach from the Velikiy Ustyug City to Kotlas, the most problematic ice jam flooding area in European Russia. The modeling was performed on the basis of STREAM_2D software complex for current conditions and taking into account the possible construction of various protective structures. Methods for the prevention of negative impact of water at the site are examined.

     

Analysis of the Impact of Hydrotechnical Construction on the Amur River near Blagoveshchensk and Heihe Cities Using a Two-Dimensional Hydrodynamic Model

Water flow and sediment transport under the effect of hydrotechnical constructions on the Amur River near Blagoveshchensk and Heihe cities was analyzed based on two-dimensional hydrodynamic modeling using STREAM_2D software (the authors V. Belikov et al., Russia). Three modeling scenarios were considered: without constructions, with the embankment of Blagoveshchensk, with the embankment of Blagoveshchensk and a system of dams near the Chinese island of Big Heihe. Modeling results have shown that the embankment has only a local effect on the part of the Amur R. upstream from confluence with the Zeya R. The construction of dams in the side channels near the island of Big Heihe can lead to significant flow redistribution, providing the flow concentration in the main river channel and reduction of the water flow, entering the island system. An increase in erosion in the main channel downstream of the confluence near the left bank and a simultaneous increase in accumulation near the right bank of the Amur R. below the island system can take place as the result of side channels shutting by dams from the right bank.