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Ha, H.K.; Seo, J.Y.; Jung, Y.H.; Ha. H.J.; Kim, S.B.; Kang, J.W.; Kim, Y.H., and Ryu, J., 2018. Dynamics of sediment resuspension in the inner harbor under different forcing conditions: A case study of Ulsan, Korea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 451–455. Coconut Creek (Florida), ISSN 0749-0208. Bottom mooring data of currents and backscatter strength derived from a 1200-kHz acoustic Doppler current profiler were collected in the inner Onsan Harbor, Ulsan during the summer season (July 5 to August 5, 2016). The mean volume backscattering strength (MVBS), which is a proxy of suspended sediment concentration (SSC), continued to exhibit distinct signatures of sediment erosion (or resuspension) under different forcing conditions such as tides, winds, and precipitation. Results exhibit the different patterns of sediment resuspension between spring and neap tides. During spring tide, the extensive tidal forcing provided a favorable condition to resuspend sediments trapped near the bed. The MVBS with high SSC was consistently recorded. During neap tide, on the other hand, the MVBS with high SSC was intermittently recorded, which was related to the strong wind events. While the flow was being intensified by winds, the short-lasting (2–4 hours) sharp spikes of MVBS were observed. The stratification developed by increased precipitation might cause to block the upward transport of sediments near the bed, even though the strong winds (>13.6 m s−1) lasted over 4 days. These outcomes could give insight into the complexity of hydrodynamics and sediment transport occurring in the harbor where various natural and artificial forcings are combined. [ABSTRACT FROM AUTHOR]

Wang, A. M.; Wang, H. J.; Bi, N. S., and Wu, X., 2016. Sediment transport and dispersal pattern from the Bohai Sea to the Yellow Sea. Suspended sediment flux, dispersal patterns and its possible mechanisms in the Bohai Sea were investigated based on the observational data in May and November, 2012, data retrieved from MODIS imageries and the ocean current data from HYCOM. The sediment dispersal pattern and the annual net sediment flux presented evident seasonal variability. During wintertime, the prevailing strong northerly winds and the related high wave heights resuspended the sediment along the coast of the Huanghe Delta that was transported into the Laizhou Bay along its western coast and exported to the Bohai Strait through the eastern Laizhou Bay as enhanced by the coastal current. The wintertime contributed approximately 4.84 Mt of suspended sediment flux to the Yellow Sea, as higher than the flux in summertime by one order. In summertime, the less energetic environment together with the stratified water column was unfavorable to the sediment export to the Yellow Sea. As a result, the sediment delivered by the Huanghe to the sea in summertime mostly accumulated within the subaqueous delta, which acted as a primary source of sediment export to the Yellow Sea in wintertime. [ABSTRACT FROM AUTHOR]

The behaviour of sediment fluxes is currently less well understood in the inner-surf and swash zones than farther seaward. In the present study, field measurements were obtained of cross-shore velocity and suspended-sediment concentration from 6 and 13 heights above the bed, respectively, between the breakpoint and the shore of an intermediate- to-reflective beach, over a range of hydrodynamic conditions, to examine the cross-shore structure of sediment flux and the physical mechanisms responsible for the observed patterns. Particular attention is given to the innersurf and swash zones, which are known to contain sediment-transport processes poorly predicted by models based on velocity moments. The cross-shore structure of the depth-integrated, suspended sediment flux is found to vary according to the forcing conditions considerably more in the inner-surf and swash zones than in the outer surf and shoaling zones. In high-energy conditions, fluxes are dominated by a large offshore peak in the outer swash zone, and in low-energy conditions, fluxes are dominated by weak onshore values increasing shorewards. Examination of the temporal and vertical structure of the velocity, sediment concentration, and flux within individual events where offshore transport was dominant reveals that near-bed suspended sediment responds just as readily to mid-watercolumn velocity shear as to boundary-layer shear. Examination of events in which onshore transport was dominant reveals that near-bed suspended-sediment concentration responds more readily to near-bed horizontal acceleration than to absolute values of near-bed velocity. [ABSTRACT FROM AUTHOR]

Ensemble-averaged suspended sediment concentrations (SSC) and transport from the swash zone of a high-energy beach are investigated with respect to the time-averaged setup level obtained from calibrated video records. Ensemble-averaged data indicate variability in SSC between both uprush and backwash during rising and falling tides. Mean ebb-tide SSC exceeds mean flood-tide SSC during both the uprush (by 28-34%) and backwash (by up to 25%). Suspended sediment concentration also varies between swash phases over a tidal cycle with mean uprush SSC exceeding mean backwash SSC by 46% to 108% depending on tidal level, with a general percentage decrease during the falling tide. The net ensemble-averaged transport (velocity-SSC product) magnitude displays a decreasing trend from roughly 30 to 20 kg m-1 during the rising tide and from roughly 45 to 15 kg m-1 during the falling tide that cannot be explained based on the percentage of foreshore immersion (water depth) alone. Thus, relative tidal level (cross-shore instrument position within the swash zone) and the phase of tide (rising or falling) within the swash zone play an important role in determining the magnitude of sediment suspension and transport. [ABSTRACT FROM AUTHOR]

Swash zone sediment transport is generally measured in an Eulerian reference frame, but this approach tends to give insufficient information on spatial transport characteristics. This paper utilizes a novel technique to map measured suspended sediment concentrations (SSC) onto the x-t plane, thus providing a visualization of SSC at all locations throughout a swash cycle. The widely adopted energetics or bed shear stress approaches to modeling suspended sediment transport in the swash predict that SSC varies directly with the horizontal velocity, u, to the power of either 2 or 3. A calibrated ballistic swash model was used to predict SSC(x,t) ∞ u² and SSC(x,t) ∞ u³. The qualitative comparison between field measurements and transport model predictions in x-t space provides the opportunity to examine the transport model performance throughout the swash zone. The agreement between observed and modeled SSC patterns was generally poor. Similar to previous observations, SSC was larger during the uprush than the backwash. During the uprush, however, the models predict a maximum in SSC at the moving shoreline and a rapid drop-off behind the leading swash edge, whereas observed SSC was maintained at high levels for most of the uprush phase. During backwash, there was very little correspondence at all between the patterns of predicted and observed SSC; in particular, observed SSC was unexpectedly small in the mid- and late stages of the backwash. A general consensus is emerging that existing swash zone sediment transport models that assume SSC is in equilibrium with the horizontal flow velocity are inadequate. This study suggests that this is probably due to presuspended sediment being advected into the swash zone, the effects of bore-generated turbulence being advected into the swash zone, and both bed shear stress and Reynolds stresses being out of phase with the horizontal flow velocity. [ABSTRACT FROM AUTHOR]

Measurements of cross-shore velocity (u) at z = 3 cm and suspended sediment concentration (SSC) at z = 1–33 cm were collected from the swash zones of gently sloping (Perranporth, UK) and steep (Sennen, UK) beaches, during morphodynamic conditions ranging from highly dissipative to almost reflective and breaker heights ranging from 0.8 to 2.2 m. Nine swash-zone data collection runs were used to compare the performance of simplified versions of Bagnold-type energetics sediment transport models on the two different beaches. Models originally designed for suspended load, where the sediment transport (I) is approximately proportional to u4, showed no apparent improvement over those intended for bedload, where I ∞ u³. It is suggested that the lowest SSC sensors could be measuring high concentrations in the sheet-flow layer, where previous laboratory results suggest a u³ model is most appropriate. The overall performance of the model is better (average r² = 76%) on the gently sloping beach than on the steep beach (average r² = 49%). Modifications to account for processes, such as bore turbulence, may improve the model's performance, particularly on steep reflective beaches. [ABSTRACT FROM AUTHOR]

Two-dimensional data of mean and sediment flow collected at a natural confluence of channels in the inner Bahía Blanca Estuary are presented. We describe the two-dimensional flow field to assess the role of changes in bed morphology occurring during transport-effective events on the structure of flow at a confluence; and to examine how the flow structure varies with changes in the ratio of momentum flux. At each station, vertical profiles of velocity, salinity, temperature and suspended sediment were obtained during the whole tidal cycle and residual fluxes were obtained. Lagrangean flux is higher than possible fresh water input, denoting an extra output of water which is the flux over the tidal flats along the southern and northern coasts of the channel. The effect of the junction produces a distortion of the vertical profile flow and in the suspended sediment transport. The effect of the particular conformation of the system makes necessary for consider the lateral effect of the tidal fiats in the circulation of the estuary which exerts a significant influence. [ABSTRACT FROM AUTHOR]

Along-channel velocity, salinity, and total suspended sediment concentration profiles were measured during 15 complete neap and spring tidal cycles in the dry and rainy seasons in four cross-sections in a tropical estuary, Itamaracá, Pernambuco, Brazil. The net longitudinal fluxes of salt and sediments were decomposed into advective, tidal, and cross-sectional shear transports. The advective transport of both salt and suspended sediments were for most parts export-directed and greater than the combined river discharge, suggesting a non-steady state. The dispersive tidal transport was decomposed into four separate mechanisms of which tidal pumping transport and tidal wave transport (similar to transport by Stokes' drift) are the main transport mechanisms. The cross-sectional shear transport was negligibly small, and thus, vertical nor lateral effects are significant with respect to longitudinal dispersion in the case of Itamaracá. [ABSTRACT FROM AUTHOR]

In this paper, the geometric characteristics of wave-induced offshore bars are investigated by using physical models. Both regular and irregular waves were used during the testing. Beach sand with a mean diameter of 0 35 mm and a specific gravity of 2.63 was selected for the study. The initial slope of the beach was 1:5. Different wave groups were generated over the initially flat beach, and a number of geometric parameters were determined. These parameters included the location of the bar crest, the equilibrium point, and the closure point. The results of the experimental study wore evaluated and some empirical expressions based upon the results are suggested to define those geometric parameters for pure regular waves, pure irregular waves and regular-irregular waves. The proposed formulas were compared with those of Silvester and Hsu (1997). These comparisons showed that a good correlation exists between the results of their earlier formulas and those of the proposed formulas derived for regular waves. It was also determined that the effect of wave types upon the bar crest is more than that of the equilibrium point. [ABSTRACT FROM AUTHOR]

On a high-energy coast, with heterogeneous nearshore bathymetry and sediment dynamic (New Plymouth, New Zealand), two colours of artificial fluorescent tracer were used to i) investigate tbe sediment entrapment/bypassing of a port entrance, and ii) to monitor sediment movement from an experimental nearshore dredged-sand dump mound (47,000 m3). Two simultaneous releases lone for each colour) were made in 6 to 10 m water depths, near the port entrance and on the dump mound. 1400 m apart. Tbe tracer was tracked over 10 months by collecting and analysing 1179 surficial sediment samples, with concomitant wave/current recording at up to 13 nearshore sites. Tbe results demonstrate trapping in the breakwater tip-shoal of tbe part, by-passing and movement through the complex nearshore reef system. The dominant transport was alongshore. Tracer released near the port entrance depicted a natural sediment "pathway" past the harbour shipping entrance and over tbe rocky reefs to the beaches 4.5 km away. Very little tracer was detected within tbe harbour, indicating that tbe main transport from the release depths 16-10 ml by-passed tbe harbour entrance and tip-shoal. The tracer shows that only sediments very close to tbe harbour breakwater (i.e. within 100 m) are trapped at the harbour entrance. From the dump mound, tracer was observed to migrate mostly longshore away from tbe port, although a minor "updrift" migration was observed. The tracer results are in accordance with measured and numerically modeled currents, which show a dominant longshore flow away from the port and weak reversing flows in the quiescent lee of the harbour at the dump mound. The tracer data also suggest that the raised shore normal reefs do not present a significant impediment to longshore transport, but rather that the nearshore circulation patterns are the predominant influence on the .sediment transport vectors. Rates of tracer spreading were found to range from 0.095 to 0.288 m2s-1. which is consistent with a high-energy coastal environment. Diffusion and advection of suspended sediments is the primary mechanism of sediment transport, and tracer was found on beaches 4.5 km distant from the release point within 13 days of injection. [ABSTRACT FROM AUTHOR]