scholarly journals The Impact of Ice Cover and Sediment Nonuniformity on Erosion Around Hydraulic Structures

10.5772/61468 ◽  
2015 ◽  
Author(s):  
Peng Wu ◽  
Jueyi Sui ◽  
Ram Balachandar
Keyword(s):  
Ice Cover ◽  
Hydraulic Structures ◽  
The Impact

Reconsidering the sediment connectivity and sediment transfer under the influence of hydraulic structures and coal mining in the Jiu river basin

2021 ◽  
Author(s):  
Gabriela Adina Morosanu ◽  
Marta Cristina Jurchescu
Keyword(s):  
Coal Mining ◽  
River Basin ◽  
Spatial Scales ◽  
Sediment Supply ◽  
Anthropogenic Factors ◽  
Hydraulic Structures ◽  
Water Runoff ◽  
Sediment Sources ◽  
Sediment Transfer ◽  
The Impact

<p>The key to an efficient basin management, taking into account both the liquid (river water runoff and its quality) and the solid (sediment sources and delivery) components lies in the way we approach the complex problem of sediment-generating areas in a river basin. This complexity is manifested both through the primary geomorphological processes that contribute to the mobilization of significant amounts of alluvia from the slopes and along the river valleys, and the various environmental and anthropogenic factors that act as restrictors or catalysts of sediment transfer.</p><p>In the present study, we aim to analyze the various categories of anthropogenic factors, operating at different spatial scales (local or at subcatchment/river sector level), which contribute, together with the intrinsic geomorphological potential, to the sediment supply or, conversely, to the inhibition of erosion, transport and accumulation processes.</p><p>Tracking sediment mobilization, transfer, intermediate storage and final delivery in a lithologically and geomorphologically complex environment, such as the Jiu River Basin (10,070 km<sup>2</sup>), located in SW Romania, is a difficult task which can become even more challenging when we factor in the contribution of some additional elements of an anthropic nature. In our study area, represented by a Carpathian and Danubian river basin, some of the most significant issues impacting the research include, on the one hand, the existence of reservoirs and dams, the strengthening of anti-flood embankments or the presence of water diversions, to cite only hydrotechnical interventions, or the impact of coal mining on landforms, slope processes and sediment sources, on the other hand.  All these factors can act locally or regionally and they can surpass the influence exerted by the natural factors, thus being responsible for the reduction, storage, or, on the contrary, for the acceleration of specific hydro-sedimentary fluxes on certain paths.</p><p>In order to connect these two categories of potential factors regulating sediment generation and transfer, the methodological approach consists in evaluating the internal – geomorphic upstream-downstream connectivity in relation/contrast with the disruptive anthropogenic factors. The proposed workflow can be divided in two steps: 1) the identification of the upstream sediment generating areas which are most connected to the downstream delivery/ storage/ accumulation areas (river network and river mouth) by applying the connectivity index (IC) proposed by Cavalli et al. (2013); and 2) the evaluation of potential hotspot areas exhibiting the highest degree of connectivity, as seen through the lens of the additional coupling or decoupling effects induced by the anthropic activities specific to the Jiu river basin: hydraulic structures and coal mining.</p><p>Outcome discussions will focus on mapping problematic sediment production, storage and transfer sectors, as evidenced by the impact of hydrotechnical works and artificial landforms from coal mining on the connectivity potential of the Jiu river basin.</p>

Radiothermal radiation of the ice cover of the Arakhley lake as a geo-indicator of changes in a water body

2020 ◽  
Vol 26 (7) ◽  
pp. 6-16
Author(s):  
V. Venslavsky ◽  
◽  
А. Orlov ◽  
Yu. Kharin ◽  
◽  
...  
Keyword(s):  
Thermal Radiation ◽  
Water Body ◽  
Seasonal Variability ◽  
Crack Formation ◽  
Time Lag ◽  
Ice Cover ◽  
Anthropogenic Factors ◽  
Microwave Range ◽  
Ecological State ◽  
The Impact

The object of this study was the ecosystem of a water body; the subject was the radio-thermal radiation of the ice cover as a geo-indicator of changes in the ecological state of the Lake Arakhley. On the basis of a systematic approach, the work assessed the contribution of the seasonal variability of the properties of the ice cover to the intensity of radio-thermal radiation as a geo-indicator of the ecological system. At present, the influence of the ice cover deformation during the crack formation period on the intensity of radio-thermal radiation has not been sufficiently studied, which determined the relevance of an experimental study for use in problems of assessing anthropogenic factors of influence. The aim of the study was to measure the seasonal variability of the intensity of radio-thermal radiation as a background geo-indicator of the temperature regime and deformation of the ice cover during the crack formation period in the absence of direct anthropogenic factors. In January-March 2020, remote radio-physical methods were used to study the intensity of radio-thermal radiation of the microwave range for the test area of the ice cover of the Lake Arakhley during synchronous contact measurements of deformation and temperature in a niche at a depth of 40 cm from the surface. According to the data obtained, the reaction of the deformation sensor signal to daily temperature variations with a time lag of 1…3 hours was recorded. According to the results of the study, the correlation coefficient of the data of the ice deformation channel and the intensity of radio-thermal radiation in the range of 8…14 mm exceeded ± 0.7 (with a window of 1000 s), with the data of the temperature sensor in most areas exceeded ± 0.9. This proves the relationship between the temperature and deformation of the ice surface with the intensity of radio-thermal radiation, as a seasonal geo-indicator in determining the ecological state of the lake. The increments in the brightness temperature during the period of increased crack formation in the 14 mm channel, with a significant correlation with the deformation data, were about 3…6 K, which can also serve as a geo-indicator of seasonal changes in the properties of the ice cover. The results of the study were obtained in the absence of direct anthropogenic factors and are background geoindicators of the seasonal state of the ice cover during the period of temperature and dynamic loads during deformation and cracking, and in the future will be used in practice for correction in assessing the impact of anthropogenic factors

scholarly journals The Impact of Regional Arctic Sea Ice Loss on Atmospheric Circulation and the NAO

2016 ◽  
Vol 29 (2) ◽  
pp. 889-902 ◽  
Author(s):  
Rasmus A. Pedersen ◽  
Ivana Cvijanovic ◽  
Peter L. Langen ◽  
Bo M. Vinther
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
General Circulation ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Near Surface ◽  
Arctic Sea ◽  
The Impact ◽  
Sea Ice Reduction

Abstract Reduction of the Arctic sea ice cover can affect the atmospheric circulation and thus impact the climate beyond the Arctic. The atmospheric response may, however, vary with the geographical location of sea ice loss. The atmospheric sensitivity to the location of sea ice loss is studied using a general circulation model in a configuration that allows combination of a prescribed sea ice cover and an active mixed layer ocean. This hybrid setup makes it possible to simulate the isolated impact of sea ice loss and provides a more complete response compared to experiments with fixed sea surface temperatures. Three investigated sea ice scenarios with ice loss in different regions all exhibit substantial near-surface warming, which peaks over the area of ice loss. The maximum warming is found during winter, delayed compared to the maximum sea ice reduction. The wintertime response of the midlatitude atmospheric circulation shows a nonuniform sensitivity to the location of sea ice reduction. While all three scenarios exhibit decreased zonal winds related to high-latitude geopotential height increases, the magnitudes and locations of the anomalies vary between the simulations. Investigation of the North Atlantic Oscillation reveals a high sensitivity to the location of the ice loss. The northern center of action exhibits clear shifts in response to the different sea ice reductions. Sea ice loss in the Atlantic and Pacific sectors of the Arctic cause westward and eastward shifts, respectively.

CFD Study on Free-Surface Influence on Tidal Turbines in Hydraulic Structures

2015 ◽  
Author(s):  
Aldo Tralli ◽  
Arnout C. Bijlsma ◽  
Wilbert te Velde ◽  
Pieter de Haas
Keyword(s):  
Free Surface ◽  
Storm Surge ◽  
Field Measurements ◽  
Hydraulic Structures ◽  
Generic Structure ◽  
Tidal Turbines ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Method Model ◽  
Blade Element

In order to estimate the impact on energy production and environment of tidal turbines placed in or near hydraulic structures like discharge sluices or storm surge barriers, a Computational Fluid Dynamics (CFD) study has been carried out on the relation between (head) loss induced by the turbines and their gross power production. CFD computations have been performed for Tocardo T2 turbines, using STAR-CCM+. Simulations of a single turbine in free flow conditions compare favorably with results of Blade Element Momentum (BEM) computations, in terms of torque and thrust. This BEM method model had been previously validated against both CFD data and field measurements. Then, a series of tests has been performed in a “virtual tow tank”, including the effect of the free surface and the blockage by side and bottom walls. These computations provide a base for a first estimate of the effect of turbines on the discharge capacity of a generic structure. This is considered to be the first step in a more general approach in which ultimately the effect of tidal turbines in the Eastern Scheldt Storm Surge Barrier will be assessed.

scholarly journals Pack-Ice Motion in the Weddell Sea in Relation to Weather Systems and Determination of a Weddell Sea Sea-Ice Budget

1989 ◽  
Vol 12 ◽  
pp. 104-112 ◽  
Author(s):  
D.W.S. Limbert ◽  
S.J. Morrison ◽  
C.B. Sear ◽  
P. Wadhams ◽  
M.A. Rowe
Keyword(s):  
Sea Ice ◽  
Surface Pressure ◽  
Ice Cover ◽  
Weddell Sea ◽  
Air Pressure ◽  
Ice Formation ◽  
Pack Ice ◽  
The Impact

As part of the Winter Weddell Sea Project 1986 (WWSP 86), a buoy, transmitting via TIROS-N satellites to Service Argos, was inserted into an ice floe in the southern Weddell Sea. Operational U.K. Meteorological Office numerical surface-pressure analyses, which utilized the buoy’s measured values of air pressure and temperature, are used to assess the impact of weather systems on pack-ice movement. The motion of the buoy is shown to be related closely to the position of the circumpolar trough and to the tracks of depressions crossing the area. The tracks of this and other buoys deployed during WWSP 86 are analysed, together with the known drifts of some ice-bound vessels, to establish the overall movement of sea ice in the central and western Weddell Sea. Using these data, the area of ice transported northward out of the Weddell Sea is determined. Roughly 60% of the winter sea-ice cover is discharged out of the area, and is replaced by new ice formation in coastal polynyas and by influx of new ice from the east. In summer, a further 30% is discharged northward out of the region, leaving 40% cover and by implication a 30% loss by melting.

scholarly journals Conditions of spatiotemporal variability of the thickness of the ice cover on lakes in the Tatra Mountains

2020 ◽  
Vol 17 (10) ◽  
pp. 2369-2386
Author(s):  
Maksymilian Solarski ◽  
Mirosław Szumny
Keyword(s):  
Snow Cover ◽  
Winter Season ◽  
Ice Cover ◽  
Spatiotemporal Variability ◽  
Ice Thickness ◽  
Tatra Mountains ◽  
Cover Thickness ◽  
The Tatra Mountains ◽  
The Impact

Abstract This research aimed to identify the impact of local climatic and topographic conditions on the formation and development of the ice cover in high-mountain lakes and the representativeness assessment of periodic point measurements of the ice cover thickness by taking into consideration the role of the avalanches on the icing of the lakes. Field works included measurement of the ice and snow cover thickness of seven lakes situated in the Tatra Mountains (UNESCO biosphere reserve) at the beginning and the end of the 2017/2018 winter season. In addition, morphometric, topographic and daily meteorological data of lakes from local IMGW (Polish Institute of Meteorology and Water Management) stations and satellite images were used. The obtained results enabled us to quantify the impact of the winter eolian snow accumulation on the variation in ice thickness. This variation was ranging from several centimetres up to about 2 meters and had a tendency to increase during the winter season. The thickest ice covers occurred in the most shaded places in the direct vicinity of rock walls. The obtained results confirm a dominating role of the snow cover in the variation of the ice thickness within individual lakes.

Water wave transients in an ice-covered channel

2011 ◽  
Vol 38 (4) ◽  
pp. 404-414 ◽  
Author(s):  
François Nzokou ◽  
Brian Morse ◽  
Jean-Loup Robert ◽  
Martin Richard ◽  
Edmond Tossou
Keyword(s):  
Analytical Solutions ◽  
Water Waves ◽  
Numerical Solutions ◽  
Wave Attenuation ◽  
Ice Sheet ◽  
Ice Cover ◽  
Beam Equation ◽  
Transverse Cracks ◽  
Time Step ◽  
The Impact

Many studies show that the propagation of a breakup water surge in impeded rivers (ice cover present) differs from the unimpeded case. Some of the differences are due to ice sheet breaking into pieces as the wave travels downstream while others are due to the effect of a fissured but otherwise intact ice cover’s resistance to motion. This is the subject of this paper: water waves that are sufficiently strong to break the cover away from the banks but not strong enough to create transverse cracks. Although some analytical solutions exist for the propagation of these transients for simple cases, for the first time in the literature, this paper introduces numerical solutions using a FEM model (HYDROBEAM) that simulates this interaction using the one-dimensional Saint-Venant equations appropriately written for rivers having an intact fissured floating ice cover coupled with a classic beam equation subject to hydrostatic loads (often referred to as a beam on an elastic foundation). The governing equations are numerically expressed and are solved using a finite element method (FEM) for the hydrodynamic and ice beam equations separately. A coupling technique is used to converge to a unique solution at each time step (for more information on the numerical characteristics of the model, see companion paper presented by the authors in this issue). The coupled model, gives a first and unique opportunity to compare the simplified analytical solutions to the full numerical solutions. A parametric analysis is herein presented that quantifies the impact of the ice cover's presence and stiffness on wave attenuation and wave celerity as well as to quantify tensile stresses generated in the ice sheet as a function of ice properties (thickness and strength) and channel shape (rectangular and trapezoidal). In general, for rectangular channels, it was found that the simplified analytical solutions are quite representative of the phenomenon namely that short wave transients are affected by the cover’s stiffness but long waves (>400 m) are not.

scholarly journals Phytoplankton distribution in unusually low sea ice cover over the Pacific Arctic

2012 ◽  
Vol 9 (11) ◽  
pp. 4835-4850 ◽  
Author(s):  
P. Coupel ◽  
H. Y. Jin ◽  
M. Joo ◽  
R. Horner ◽  
H. A. Bouvet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Marine Ecosystem ◽  
Environmental Parameters ◽  
Arctic Basin ◽  
Ice Cover ◽  
Phytoplankton Distribution ◽  
The Pacific ◽  
Ice Retreat ◽  
Sea Ice Retreat ◽  
The Impact

Abstract. A large part of the Pacific Arctic basin experiences ice-free conditions in summer as a result of sea ice cover steadily decreasing over the last decades. To evaluate the impact of sea ice retreat on the marine ecosystem, phytoplankton in situ observations were acquired over the Chukchi shelf and the Canadian basin in 2008, a year of high melting. Pigment analyses and taxonomy enumerations were used to characterise the distribution of main phytoplanktonic groups. Marked spatial variability of the phytoplankton distribution was observed in summer 2008. Comparison of eight phytoplankton functional groups and 3 size-classes (pico-, nano- and micro-phytoplankton) also showed significant differences in abundance, biomass and distribution between summer of low ice cover (2008) and heavy ice summer (1994). Environmental parameters such as freshening, stratification, light and nutrient availability are discussed as possible causes to explain the observed differences in phytoplankton community structure between 1994 and 2008.

scholarly journals Impact of a warm anomaly in the Pacific Arctic region derived from time-series export fluxes

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0255837
Author(s):  
Catherine Lalande ◽  
Jacqueline M. Grebmeier ◽  
Andrew M. P. McDonnell ◽  
Russell R. Hopcroft ◽  
Stephanie O’Daly ◽  
...  
Keyword(s):  
Sea Ice ◽  
Bering Sea ◽  
Chukchi Sea ◽  
Arctic Region ◽  
Ice Cover ◽  
Biological Pump ◽  
Northern Bering Sea ◽  
Pacific Waters ◽  
The Pacific ◽  
The Impact

Unusually warm conditions recently observed in the Pacific Arctic region included a dramatic loss of sea ice cover and an enhanced inflow of warmer Pacific-derived waters. Moored sediment traps deployed at three biological hotspots of the Distributed Biological Observatory (DBO) during this anomalously warm period collected sinking particles nearly continuously from June 2017 to July 2019 in the northern Bering Sea (DBO2) and in the southern Chukchi Sea (DBO3), and from August 2018 to July 2019 in the northern Chukchi Sea (DBO4). Fluxes of living algal cells, chlorophyll a (chl a), total particulate matter (TPM), particulate organic carbon (POC), and zooplankton fecal pellets, along with zooplankton and meroplankton collected in the traps, were used to evaluate spatial and temporal variations in the development and composition of the phytoplankton and zooplankton communities in relation to sea ice cover and water temperature. The unprecedented sea ice loss of 2018 in the northern Bering Sea led to the export of a large bloom dominated by the exclusively pelagic diatoms Chaetoceros spp. at DBO2. Despite this intense bloom, early sea ice breakup resulted in shorter periods of enhanced chl a and diatom fluxes at all DBO sites, suggesting a weaker biological pump under reduced ice cover in the Pacific Arctic region, while the coincident increase or decrease in TPM and POC fluxes likely reflected variations in resuspension events. Meanwhile, the highest transport of warm Pacific waters during 2017–2018 led to a dominance of the small copepods Pseudocalanus at all sites. Whereas the export of ice-associated diatoms during 2019 suggested a return to more typical conditions in the northern Bering Sea, the impact on copepods persisted under the continuously enhanced transport of warm Pacific waters. Regardless, the biological pump remained strong on the shallow Pacific Arctic shelves.

scholarly journals Influence of speed distribution in a rounded flow on the character of slopes erosion

2019 ◽  
Vol 20 (1) ◽  
pp. 85-95
Author(s):  
O. Ya. Maslikova ◽  
I. I. Gritsuk ◽  
D. N. Ionov ◽  
V. K. Debolskiy
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Hydraulic Structures ◽  
Natural Conditions ◽  
Channel Processes ◽  
Speed Distribution ◽  
Straight Line ◽  
River Hydraulics ◽  
Critical Reynolds Numbers ◽  
The Impact

One of the most important issues of river hydraulics is the movement of water and the formation of a channel in a stream that has a non-straight-line outline in the plan. Under natural conditions for rivers characteristic winding shape in the plan. The curvature of the jet occurs when the flow is divided into sleeves, at the inflow into the river, the confluence of flows, etc. Therefore, the study of channel processes in rivers is impossible without knowledge of the flow patterns at the curve of the channel. When designing hydraulic structures, including bridge crossings on the meandering sections of rivers, one should know the features of the dynamics of the channel in the sections of the flow turning. In winter, such areas may be narrowed due to the freezing of the channel, and during the period of ice thawing they are clogged with ice fragments. The narrowing of the canal causes an increase in the Reynolds number and a redistribution of velocity diagrams in the area under consideration, which causes a change in the erosion pattern. In laboratory conditions, the nature of the distribution of velocities and the formation of vortices on the installation, creating a rounded flow. It is shown that, at critical Reynolds numbers, a vortex countercurrent occurs in the rounded flow at the inner shore. The impact of this velocity distribution on the erosion pattern of the various slopes of the rounded flow was analyzed.

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