Wyniki wyszukiwania - Biblioteka Nauki

1

A quasi phase-resolving model of net sand transport and short-term cross-shore profile evolution

100%

Ostrowski R.

Oceanologia

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2003

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tom No. 45 (2)

261-282

EN

A way of modelling of the net sediment transport rate on a cross-shore profile and the resulting sea bed changes is presented. In the sediment transport computations, a three-layer model with a description of the bedload based on the water-soil mixture theory by Kaczmarek & Ostrowski (1998, 2002) is used. The modelling system is applied to wave-current conditions variable over the cross-shore profile, and determined using the computational framework of Szmytkiewicz (2002a, b). The sediment transport module incorporates the asymmetric wave approaches as proposed by Ostrowski (2002). Model simulations have been produced for uniformly sloped and multi-bar initial cross-shore profiles. Some of the model results are compared with the IBW PAN (Institute of Hydroengineering of the Polish Academy of Sciences) field data collected at the Coastal Research Station in Lubiatowo.

2

Experimental Analysis of Relations Between Coherent Turbulent Structures and Formation of Bedforms

100%

Termini D. , Sammartano V.

Archives of Hydro-Engineering and Environmental Mechanics

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2008

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tom Vol. 55, nr 3-4

125-143

EN

The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measurements of flow velocity components were carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) was verified through conditioned quadrant analysis. The quantitative information on the spatial and temporal evolution of turbulent events was obtained through space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence formation of bedforms, the spatial scale of turbulent event evolution has been compared with the wavelength of bed-forms (alternate bars) observed on the bed. The analysis has essentially highlighted that such spatial scale compares well with the wavelength of the bars.

3

Effect of Riffle Sequences on Discharge and Sediment Transport in a Mountain Stream

100%

Korpak J. , Lenar-Matyas A. , Łapuszek M. , Mączałowski A.

Journal of Ecological Engineering

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2019

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tom Vol. 20, nr 3

157--166

EN

Natural riffles are formed as a result of fluvial processes in the stream channel, water flow, and sediment movement. In recent years, artificial riffles have also been constructed in order to improve the water flow and sediment transport as well as to initiate the processes that lead to the restoration of natural riffle–pool sequences. In river engineering, the utilization of artificial riffles (rapid hydraulic structures) is still in its experimental stage. Artificial riffles are studied and described in the literature on a case study basis. However, the studies on riffle sequences and their effects on stream channel evolution need to be improved. A system of artificial riffles was created in the mouth section of Krzczonówka Stream in 2013. The new riffles made the stream channel more morphologically diverse and also reduced its longitudinal slope. The check dam on the stream, located upstream of the newly formed riffles, was renovated and lowered in 2014. At this time, a flood occurred and released a large mass of sediment downstream of the check dam. Then, the sediment settled in the sections between the artificial riffles, thus covering some of them. The aim of the study was to examine the effect of the system of riffles on the changes in sediment transport and water flow in the studied stream channel. Calculations indicate that the system of riffles established downstream of the check dam has limited the movement of sediment. The sediment transport is varied throughout the studied stream course and is mostly dependent on the sediment supply.

4

Coastal Processes at Selected Shore Segments of South Baltic Sea and Gulf of Tonkin (South China Sea)

100%

Ostrowski R. , Pruszak Z. , Różyński G. , Szmytkiewicz M. , Ninh P. V. , Quynh D. N. , Lien N. T. V.

Archives of Hydro-Engineering and Environmental Mechanics

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2009

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tom Vol. 56, nr 1-2

3-28

EN

The paper presents a comparative analysis of physical processes occurring at two different coasts, which belong to two different geographic zones, namely a subtropical region exposed to monsoons and typhoons and a region of temperate climate with ice-snowy winter season. The former coast comprises sandy shores nearby Lubiatowo and the Hel Peninsula, located at the south Baltic Sea in Poland. The shore at Lubiatowo is relatively stable in the long run, while the shore along Hel Peninsula is mostly vulnerable to erosion and strongly protected by use of various measures (groins, seawall and artificial beach nourishment). The second site is the eroded (and partly protected by dikes) coast at Hai Hau in the Gulf of Tonkin (the South China Sea, Vietnam). This shore segment is built of mixtures of sandy and cohesive material, comprising both marine sands and river-borne sediments which nourish the coastal zone at the Red River mouth, located northwards of the Hai Hau beach. The present analysis is focused on differences and similarities of hydro- and morphodynamics between the above coastal zones in various time and spatial scales. The analysis shows that regional climatic and environmental conditions, associated with geographical zones, play a key role in dynamic evolution of the coastal regions and necessitate different engineering activities against erosion and flooding.

5

Application of two coastal profile evolution models to Lubiatowo, Poland and La Barrosa, Spain

100%

O'Hare T. J. , Ostrowski R. , Emsley S. M. , Huntley D. A.

Archives of Hydro-Engineering and Environmental Mechanics

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2006

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tom Vol. 53, nr 3

235-266

EN

Two contrasting coastal profile models are applied to three bathymetries including a uniform gradient beach and natural profiles (multi-barred and multi-stepped) obtained from Lubiatowo, Poland and La Barrosa, Spain. The first model, developed at the Institute of Hydro-Engineering of the Polish Academy of Science (IBW PAN) (Poland), couples a quasi-3D model for nearshore hydrodynamics with a quasi-phase resolving sediment transport model which considers transport in the bed load, contact load and outer layers. The second model (PLYMPROF), developed at the University of Plymouth (UK), couples a relatively simple wave transformation model with a new abstracted description of cross-shore sediment transport beneath waves. A variety of model simulations are described, including simple runs with uniform wave forcing (up to 50 days in duration using PLYMPROF) and runs with parameterized wave forcing (wave height and wave period in deep water) for periods with one or two storm events (6-11 days total duration). Both models coped well with the different initial profiles and with uniform and time-varying wave conditions. The results of the simulations suggest that onshore-directed sediment transport in the shoaling and outer surf zones is dominant for the cases considered. Compared to the IBW PAN model, the PLYMPROF model results (using coefficients from a separate study of bar evolution at Duck, USA) show larger offshore-directed transport in the inner surf zone associated with return flow, with the overall sediment transport pattern located considerably closer to the shore. Alteration of a single coefficient in the PLYMPROF model shifts the predicted transport pattern seawards, but also results in enhanced offshore-directed transport. Despite differences in predicted cross-shore sediment transport the two models produced surprisingly similar trends in overall profile evolution suggesting that feedback between existing bathymetry and the sediment transport pattern may exert a major control on profile development. Results also suggested that bar migration patterns cannot be simply related to the occurrence or absence of storm conditions, but rather depend more subtly on the exact placement of wave breaking locations in relation to existing bars. Incorporation of tidal water level variations for La Barrosa produced small changes in model predictions, with tidal migration of the sediment flux pattern suppressing the development of bar morphology in line with the form of the observed profile.

6

Variability of Hydrodynamic and Lithodynamic Coastal Processes in the East Part of the Gulf of Gdańsk

100%

Ostrowski R. , Pruszak Z. , Skaja M. , Szmytkiewicz M.

Archives of Hydro-Engineering and Environmental Mechanics

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2010

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tom Vol. 57, nr 2

139-153

EN

The paper presents new findings concerning motion of water and sediment in the coastal zone of the east part of the Gulf of Gdańsk, from the Vistula River mouth at Świbno (Poland) to Cape Taran (Russia, Kaliningrad Oblast). The presented study deals with spatial variability of parameters of hydrodynamic and lithodynamic processes which have been subject to theoretical modelling. For the considered coastal segment, deep-water wave conditions reconstructed for a 44-year period have been analysed and transformed to the nearshore zone. Next, velocities of wave-driven longshore currents for the mean statistical year have been calculated, along with the longshore sediment transport rates. Regarding the net longshore sand motion, its detected direction is from Cape Taran towards the Vistula Spit. Very high annual rates of longshore sediment transport have been obtained for the coastal segment at Sambian Peninsula. These rates decrease considerably along the Vistula Spit, reaching zero at a distance of about one third of the Polish part of the Spit, measured from its root. At this location, the net longshore sediment transport (resulting from net longshore wave-current impact) reverses from westward to eastward.

7

Sediment transport in the coastal zone

100%

Sawczyński S. , Kaczmarek L. M.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2014

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tom nr 17(2)

165--180

EN

The paper provides basic information on the description of sediment transport in the coastal zone of the sea. It explains the mechanisms of sediment movement under the influence of the waves and currents interactions, characteristic for the coastal zone. It presents models describing the movement of sediment in the regime of flat bottom, making their divided in accordance with the method of description of vertical structure of sediments transport. Particular emphasis is placed on modeling of graded sediment transport. It presents basis for the three-layer model of graded sediment transport. This allows, among others, the analysis of the variability of particle size distribution in the whole area of sediment movement. The model assumes that the movement of sediment is divided into three layers: bedload layer, contact load layer and outer flow region, as a result of the shear stress influence on the bottom.

8

Grain-size characteristics and net transport patterns of surficial sediments in the Zhejiang nearshore area, East China Sea

100%

Liang J. , Liu J. , Xu G. , Chen B.

Oceanologia

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2020

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tom No. 62 (1)

12--22

EN

Spatial variations in grain-size parameters can reflect sediment transport patterns and depositional dynamic environments. Therefore, 616 surficial sediment samples taken from the Zhejiang nearshore area in the East China Sea were analyzed to better understand the net sediment transport pattern in this region. The study area is generally dominated by clayey silt and has relatively coarse mud sediment in the southeast. The sorting coefficient of surface sediment is higher than 1.4, and sediment is poorly sorted throughout the study area. The skewness has a strong correlation with the mean grain-size diameter. The net sediment transport pathways obtained by the grain-size trend analysis indicate several distinct characteristics of the surficial sediment transport. The sediment is transported southward under the action of the stronger southward Zhejiang-Fujian Coastal Current (ZMCC) in winter in the upper part of the nearshore area. Influenced by the obstruction of the Taiwan Warm Current (TWC) and the tidal current, surficial sediment transport vectors display two areas of grain-size trend convergence and indicate the net deposition environment has a high sedimentation rate. However, the transport is mainly toward the north under the control of the prevailing northward ZMCC and the strong TWC in the summer. The sedimentary rate is closely related to the processes of the sediment transport. On the one hand, sediment transportation affects the depositional rate in a different environment. On the other hand, the modern sedimentary rate can reflect indirectly the sediment source and sediment transportation.

9

Effect of seepage on initiation of cohesionless sediment transport

100%

Liu X. , Chiew Y.-M.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1778-1796

EN

This paper presents theoretical analyses and experimental results of seepage effects, especially downward seepage, on the initiation of cohesionless sediment particles. The theoretical analysis examines how the additional seepage force acts to modify the critical shear stress for sediment entrainment. Laboratory experiments were conducted using medium sand with diameter of 0.9 mm with downward seepage to quantitatively show suction effects on sediment entrainment. The critical shear stresses with different suction rates were calculated using the experimental results. The measured data together with published results provide an overall view on seepage effects on the initiation of cohesionless sediment transport. Depending on whether seepage is in the form of injection or suction, it will either increase or decrease the critical shear stress. The result reveals that the ratio of drag force at the threshold condition with seepage to that without seepage is dependent on the ratio of the hydraulic gradient with seepage to its value at the quick condition.

10

Podstawy modelowania transportu osadów

100%

Kaczmarek L. M.

Inżynieria Morska i Geotechnika

|

2012

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tom nr 1

19-24

PL

Krytyczne uwagi dotyczące podstawowych tez zaprezentowanych w artykule A. Sawickego „O elementarnym modelowaniu transportu osadów”opublikowanym w nr 5/2011 „Inżynierii Morskiej i Geotechniki”. Formalna analiza problemu transportu osadów.

EN

Critical comments regarding basic theses included in the paper of A. Sawicki entitled „On elementary modelling of sediment transport” published in „Inżynieria Morska i Geotechnika”, No.5/2011. Formal analysis of sediment transport problem.

11

The impact of Klaipėda Port entrance channel dredging on the dynamics of coastal zone, Lithuania

100%

Žilinskas G. , Janušaitė R. , Jarmalavičius D. , Pupienis D.

Oceanologia

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2020

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tom No. 62 (4PA)

489--500

EN

Dredging entrance channels to ports on open littoral drift seashores often causes major morphological changes to the shoreline. This study aims to assess the impact of dredging the Port of Klaipėda's entrance channel and the construction of the jetties on the coastal zone. Based on an analysis of cartographic material collected between 1835 and 2017, and on field data (bathymetric surveys and cross-shore profile levelling), changes to the coastal zone in the area nearest to the port were evaluated. The dominant longshore sediment transport on the Lithuanian nearshore runs from south to north. Thus, based on established patterns, intensive accretion could have been expected to take place on the southern side of the port jetties and erosion on their northern side. However, in the case of the Port of Klaipėda, in the area nearest to the port on the updrift side of the port jetties, where accretion would have been expected to take place, the nearshore depth increased throughout the 20th century (when the length and configuration of the jetties did not change). The shoreline shifted landward instead of moving further out to sea. The present study shows that the intensive dredging of the entrance channel caused nearshore and shore erosion on the updrift side of the port jetties, even while a sufficient sediment load was being transported by the longshore drift.

12

Grain Kinematics in Weak Linear Transport

100%

Ballio F. , Radice A.

Archives of Hydro-Engineering and Environmental Mechanics

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2007

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tom Vol. 54, nr 3

223-242

EN

Some preliminary results of measurements of one-dimensional sediment transport on a flat bed are presented. Image processing was applied to measure the time evolution of the areal concentration and the velocity of transported grains in a series of bed-load tests with values of the bed shear stress up to twice the threshold for incipient motion. The concentration and velocity data were used to compute the time evolution of the solid discharge per unit width. It was found, as expected, that the sediment transport is an episodic phenomenon, particularly at low shear stress; visualization of the moving particles allows recognition of the existence of longitudinal streaks, that can be more clearly observed when the sediment rate is weaker. The first and second order statistics of sediment concentration and velocity and solid discharge have been analyzed; the mean and standard deviation of the quantities increase as the transport intensity increases, while the coefficient of variation decreases. The ranges of variation of all the time-averaged quantities with the mean sediment rate are narrower if the zero values of the samples are disregarded prior to calculating the statistics; the coefficient of variation is almost constant. The solid discharge data samples were analyzed in the amplitude domain, by calculating the Cumulative Frequency Distributions; it was found that the shape of the CFDs computed with reference to the non-zero values of the sediment rate alone is self-similar regardless of the transport intensity.

13

Double-average characteristics of sediment motion in one-dimensional bed load

100%

Radice A. , Ballio F.

Acta Geophysica

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2008

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tom Vol. 56, no. 3

654-668

EN

The sediment transport process on a flat bed was investigated experimentally, with reference to the relationship between the average solid discharge and the concentration and velocity of the moving grains. The instantaneous values of the quantities were measured and, therefore, it was possible to quantify the contribution of the temporal fluctuations of concentration and velocity to the resulting average sediment transport rate. Recognizing that the sediment transport process is an episodic phenomenon, an intermittency factor was defined and its contribution to the solid discharge, typically implicit in earlier formulations of the sediment flux, was highlighted. Conceptual analyses of the spatial scale dependence of the quantities were also made.

14

A coupled model for sediment transport dynamics and prediction of seabed morphology with application to 1DH/2DH coastal engineering problems

88%

Afentoulis V. , Papadimitriou A. , Belibassakis K. , Tsoukala V.

Oceanologia

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2022

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tom No. 64 (3)

514--534

EN

Coastline retreat poses a threat to nearshore environment and the assessment of erosion phenomena is required to plan the coastal engineering works. The hydro-morphodynamic response of a beach to natural and artificial forcing factors differ considerably, as the nearshore processes are especially complex and depended on a multitude of parameters, including prevailing wave and hydrodynamic conditions, beach topography, sediment characteristics and the presence of coastal protection works. The present study serves the purpose of numerically evaluating nearshore morphological processes and ultimately assessing the capacity of coastal defence structures to control beach erosion. For this reason, a new sediment transport model including unsteady effects and swash zone morphodynamics, was coupled to the highly nonlinear Boussinesq wave model FUNWAVE-TVD, providing integrated predictions of bed level evolution, across various timescales of interest. The compound model was validated thoroughly against laboratory data and other numerical investigations. Overall, a good agreement between experimental and numerical results was achieved for a number of test cases, investigating the effects of different types of shore protection structures. The proposed integrated model can be a valuable tool for engineers and scientists desiring to obtain accurate bed level predictions, over complex mildly and steeply sloping sea bottoms composed of non-cohesive sediment particles.

15

Towards validating a last generation, integrated wave-current-sediment numerical model in coastal regions using video measurements

88%

Carniel S. , Sclavo M. , Archetti R.

Oceanological and Hydrobiological Studies

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2011

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tom Vol. 40, No.4

11-20

EN

This paper presents the first steps in the implementation of a morphological numerical model to be applied in the Bevano River region, a shallow water area in the Adriatic Sea, with the aim of helping the identification and assessment of erosional patterns and bottom morphological modifications induced by severe marine storms. The numerical modeling, performed using a fully 3D coupled wave-current-sediment version of the ROMS model, has been complemented with in situ data analysis and observations: a first qualitative validation of the results was given by the analysis of images acquired via an ARGUS video station. Hydrodynamic modeling highlighted how shear bottom stresses and bottom currents fields were heavily influenced by severe storm situations, and had large effects on the morphology of shallow regions. The correlation between the wave-current induced bottom stresses and the resulting topography was investigated. Nearshore hydrodynamics modeling results demonstrated the dominant role played by alongshore sediment transport, with the magnitude of both cross- and along-shore wave-induced currents strongly depending on wave height and direction. We found a good qualitative conformity between the results of the numerical models applied during a "Bora" storm and the corresponding video observations; both techniques indicated the migration of the existing sandbar within the range of about 40 m seaward. Results show how integrated numerical open source tools, often used in oceanography, are becoming suitable for both preliminary investigations and for planning the effective littoral management, and how their calibration can be supported by the use of new low cost techniques, such as video measurements.

16

Recent developments in studies of sediment transport in open channels

88%

Majewski W.

Zeszyty Naukowe Akademii Rolniczej we Wrocławiu. Melioracja

|

1988

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nr 31

17

Modelling nearshore hydrodynamics and circulation under the impact of high waves at the coast of Varkiza in Saronic-Athens Gulf

88%

Belibassakis K. A. , Karathanasi F. E.

Oceanologia

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2017

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tom No. 59 (3)

350--364

EN

A plethora of physical parameters, such as hydro-, litho- and morpho-dynamic characteristics, are essential for understanding the response of coastal systems to intense sea states in terms of sediment transport and shoreline evolution. Nowadays, numerical models are extensively applied to meet the above needs and support coastal planning and management. In the present work, a 2DH dynamic modelling system is used for simulating the hydrodynamic and meteorological/oceanographic characteristics of the Saronic Gulf, in order to examine circulation patterns and predict sediment transport phenomena under high wave conditions at the coast of Varkiza, a sandy beach in the southern Attica, Greece. Time series of wind and wave data were used as input at the open boundaries of the model domain while the model was calibrated and validated through (linear and directional) statistical measures with respect to in situ wave measurements, since there was lack of hydrodynamic data at the site of interest. The simulation period of the model was between January 3 and February 19, 2013, with consecutive high waves in-between. The good agreement of the numerical results from the wave and hydrodynamic model with in situ measurements confirmed the suitability of the model for the support of sediment transport rates at Varkiza coastal segment. Model results reveal that there is a counter-clockwise water circulation during high waves that contribute to the erosion of the examined beach, which is also confirmed by independent field measurements.

18

On Flow-Altering Countermeasures for Scour at Vertical-Wall Abutment

88%

Radice A. , Lauva O.

Archives of Hydro-Engineering and Environmental Mechanics

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2012

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tom Vol. 59, nr 3-4

137-153

EN

Results are presented for clear-water scour experiments at a vertical-wall abutment where the obstacle was modified with slots or roughening elements as flow-altering countermeasures against the erosion process. The laboratory campaign comprehended an initial experiment with an unprotected obstacle, two experiments with slots above and beneath the non-scoured bed level, respectively, and one experiment with a roughened abutment. The repeatability of the experiments was checked and found satisfactory. The measured data set consisted of (i) scour depth with time; (ii) geometry of the erosion hole; and (iii) sediment motion pattern at several evolution stages of the process. A novel feature of the work was the attempt to combine evidence on the scour depth and that on sediment motion so as to shed light on the mechanism of scour reduction by the countermeasures tested. It is argued that this strategy might furnish guidelines for future extensive investigations of scour countermeasures, aimed at finding optimal design solutions.

19

Influence of the climatic variations in the wind waves parameters on the alongshore sediment transport

88%

Divinsky B. V. , Kosyan R. D.

Oceanologia

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2020

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tom No. 62 (2)

190--199

EN

The purpose of this work was to analyze the influence of climatic variability of wind waves and swell parameters in the coastal zone on the sediment transport and to assess the contribution of the swell to the formation of alongshore fluxes. The object of research is the Anapa bay-bar (the Black Sea). Mathematical modeling has shown that in the Anapa bay-bar area the average annual wind waves and swell powers have significant interannual variability. For the period from 1979 to 2017, in the southern part of the bay-bar, there was a statistically significant decrease in the share of swell in the alongshore transport, directed from NW to SE, in the central part – an increase in the contribution of swell to the total sediment flow from SE to NW, in the northern part – probable increase in flows to NW and decrease – to SE. Such a dynamic is consistent, in general, with experimental observations of the processes of erosion and accumulation of beach-forming material along the Anapa bay-bar coastline. A separate description of the bottom sediment fluxes under the influence of wind waves and swell made it possible to explain the fluctuations of the coastline over a climatic period.

20

On Uncertainties in Determination of Sediment Transport Rates in Coastal Regions

88%

Ostrowski R.

Archives of Hydro-Engineering and Environmental Mechanics

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2016

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tom Vol. 63, nr 4

265--280

EN

The paper deals with research uncertainties, difficulties, inaccuracies and unreliabilities related to the modelling of physical phenomena involving coastal lithodynamics. The considerations are focused on processes of wave transformation, wave-driven currents and sediment transport itself. It is shown that possible inaccuracies at individual stages of the modelling of coastal hydrodynamics can lead to serious uncertainties with respect to the ultimate modelling output, namely bed shear stresses and sediment transport rates. These inaccuracies result mostly from arbitrarily assumed parameters and constants. Other modelling biases discussed in the paper comprise simplifications and approximations with respect to sediment resources and size-graded properties, randomness of hydrodynamic impacts, bottom roughness and land-borne factors involved in coastal lithodynamics.