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A calibrated, coupled model (COAWST) of the Bohai and Yellow Seas was employed to examine the contributions of waves and tides to the sediment transport, and to understand the dynamic factors controlling bottom sediment resuspension around the Shandong Peninsula. The numerical results, which were consistent with the in-situ observations, illustrated two events with large values of suspended sediment concentration (SSC). The two events had similar wave heights, but SSC during the second event was more than twice that of the first one. Numerical experiments indicated that the large values of SSC east of the Shandong Peninsula were mainly ascribed to local resuspension, and that waves played a primary role in sediment resuspension for both high SSC events. The differences in SSC and bottom shear stress between the two events were mainly due to differences in wave period, representing about 65% of the total difference, and the non-linear interactions of wave and currents played a secondary role. Therefore, wave period is an important factor along with wave amplitude in the contribution of waves to sediment resuspension in this region. The combined actions of waves and currents dynamics dominate the sediment resuspension rather than either factor in isolation. Due to sheltering effect by the Shandong Peninsula, the wave effect on sediment resuspension was less to the south of the Peninsula than that to the north and east. In addition, the Shandong Coastal Current was enhanced by the northerly wind leading to more sediment transport southward along the coast of Shandong Peninsula, but this has small effect on the difference of suspended sediment concentration between two storm events. • Large values of suspended sediment concentration east of the Shandong Peninsula is mainly due to local resuspension. • The combined actions of waves and tidal dynamics dominate the sediment resuspension. • Wave period is an important factor along with wave amplitude in the contribution of waves to sediment resuspension. [ABSTRACT FROM AUTHOR]

The long-distance transport of Yellow River sediments has formed an omega-shaped ('Ω') distal muddy deposit in the Yellow Sea. Numerous studies have investigated the sediment dynamics and sedimentary evolution of the deposit, but several key questions remain unanswered due to insufficient observations. To reveal the mechanisms of sediment dynamics and quantify sediment transport and deposition processes, this study collected field datasets in the depocenter of the muddy deposit off the Shandong Peninsula. Bottom mounted tripods were deployed from August 18 to 27, 2017, and from February 23 to March 2, 2018, during which two strong wind events with speeds of over 10.8 m/s occurred. The results showed that near-bed suspended sediment concentration responded directly to varying hydrodynamic conditions, and significant differences in suspended sediment concentration between two wind events could be ascribed to a number of factors (e.g., tidal current, wave periods, wind stress, turbulence). The harmonic analysis demonstrated that suspended sediment variations during the spring tide were directed mainly by resuspension, while resuspension and advection contributed equally at neap tide. The variations in background suspended sediment concentration can be ascribed to the residual current. Furthermore, the sediment transport pattern is similar to the pattern of water circulation. Generally, the along-shore suspended sediment flux is about one order of magnitude higher than the cross-shore flux. In summer, the suspended sediment was transported mainly downcoast. In winter, sediment was transported downcoast during wavy periods and upcoast during calm periods. Advection dominated sediment flux in most cases, except during wavy periods when local resuspension increased significantly, and the contribution of resuspension term to along-shore flux was up to 87%. Meanwhile, cross-shore flux also increased significantly under strong winds, which was simultaneously modulated by downcoast and offshore winds. After statistical analysis, we found that offshore winds controlled the cross-shore sediment transport in winter. Using parameterized calculation and statistical analysis, the average accumulation rate of the study site was estimated to be 0.6 cm/yr. During calm periods, lower background sediment concentration in summer led to lower deposition rates than in winter. In addition, the frequent strong wind events in winter cause extremely high erosion rates. This study provides new perspectives on quantitative variations in suspended sediment transport and regional erosion/deposition from synoptic to seasonal variations in the distal mud deposit. • In-situ observations at the bottom boundary layer were conducted in summer and winter on the muddy deposit off the Shandong Peninsula. • The advection dominates sediment flux in most cases, except for during wind gusts when local resuspension increases significantly. • Combining parameterized method and observational data, the accumulation rate is estimated. [ABSTRACT FROM AUTHOR]

Bottom mounted platforms equipped with current profilers/meters, temperature/salinity and turbidity sensors were deployed for about 10 days in August 2017 over an elongated deposit off the coast of Shandong Peninsula, in order to monitor the hydrodynamics and sediment processes in the bottom boundary layer. In total, semidiurnal barotropic tides dominate the measured currents, accounting for 90% of total variance. However, in the cross-shore direction, greater variance is associated with the semidiurnal internal tidal currents than the semidiurnal barotropic currents. Both the Empirical Orthogonal Functions and normal mode analysis demonstrate that the baroclinic velocity is dominated by the mode-1 internal tides, i.e. the current has a vertical shear with strong opposite flows near the surface and bottom while weak in the middle. Although the bottom slope is subcritical in most area of the deposit, the ratio between the bottom slope and the slope of internal tide characteristics is greater than 0.5, suitable for local internal tide generation. The internal tides generated from the deposit are especially significant considering that the shelf of the Yellow Sea is usually broad and flat. The quantitative estimation of the water column mixing indicate that the bottom dissipation induced by the barotropic tides (6.44ⅹ10−4 m3 s−3) is greater than the internal tides (−0.95ⅹ10−4 m3 s−3), and the total dissipation rate due to bottom drag is 5.49ⅹ10−4 m3 s−3, which is much greater than the interior one due to internal tides (2.69ⅹ10−4 m3 s−3). The internal tidal current alone is not energetic enough to resuspend the local fine-grained sediments. However, in the cross-shore direction, the sediment flux due to internal tides is twice as much as the barotropic component, resulting in a net onshore sediment flux, thus highlighting the advection effect of internal tides in the coastal mass transport. • This investigation is the first to quantify the semidiurnal-band characteristics of baroclinic tidal currents and evaluate the effect of the internal tides to sediment resuspension and transport in the region of a unique elongated mud deposit off the coast of Shandong peninsula. • Mode-1 semidiurnal internal tides, the dominant baroclinic motion, is believed to be related to the steep topography of the deposit and enhanced stratification in summer. • The near-bed stress induced by internal tides is not strong enough to suspend sediments, but its contribution to sediment transport due to advection cannot be ignored. [ABSTRACT FROM AUTHOR]

This paper investigates sediment trapping in coastal embayments during summer seasons based on observation data obtained from two instrumented tripods that were placed at the mouth of Weihai Bay on north coast of Shandong Peninsula, China, over a 15-day period between 5 and August 20, 2018. The data consisted of time series of water depths, current profiles, wave parameters, near-bed flow velocities, turbidity, water salinity and temperature. Distributions of suspended sediment concentration (SSC) and water temperature in the bay and adjacent sea areas were also investigated at 87 grid stations from July 31 to August 4, 2018. From these data the bed shear stresses, residual currents and suspended sediment fluxes (SSF) were calculated. The results indicated that the variability in the SSC at the northern mouth was mainly controlled by local sediment resuspension while at the southern mouth horizontal advection due to the SSC gradient was the dominant mechanism. To identify the main drivers of the sediment transport, the SSF was analyzed using the decomposition method. The seaward advective transport due to residual flow and landward tidal pumping effect dominated the total near-bed sediment transport at the northern and southern mouths, respectively. Therefore, trapping processes occurred mainly through the southern mouth. The suspended sediment fluxes (SSF) during neap and spring tides at the southern mouth were 0.053 and 0.321 g m−2 s−1, respectively, while during moderate wave conditions (H s > 0.8 m), the SSF was two times larger than the spring tide. In summer, the fine-grained sediments trapped in the bay were mainly derived from resuspension off the eastern tip of the Shandong Peninsula and thus is indirectly from the Yellow River. During such sediment transport and trapping processes, upwelling and winds can also play important roles. • SSC variations at the northern and southern bay mouth were controlled by local resuspension and horizontal advection. • Trapping occurred mainly through the southern mouth via tidal pumping as the SSC gradient dominated the net sediment flux. • Sediments trapped in the bay were mainly derived from resuspension off the eastern tip of the Shandong Peninsula. [ABSTRACT FROM AUTHOR]