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Kim, Y.-j. and Yoon, J.-s., 2023. Shoreline variation prediction of the Jeongdongjin Sea area considering effective sediment volumes. Journal of Coastal Research, 39(1), 154–166. Charlotte (North Carolina), ISSN 0749-0208. The coastal erosion in the East Sea region of Korea has been increasing because of the imbalance in the effective sediment volume and sediment transport from coasts and rivers, which causes intermittent erosion and sedimentation. The accurate prediction of the coastal sediment budget is an extremely difficult task because the sediment transport mechanism on the coast is highly complex. Studies considering the effective sediment volume supplied through rivers remain limited, although many other studies have focused on identifying the characteristics of sediment transport on the east coast. The grain-size distribution of the soil on the coast is considered the single-grain size (D50); however, the grain-size distribution of sediments flowing into and out of the coast and the topographical characteristics of the sea area need to be considered to predict shoreline variation with a high degree of accuracy. Thus, this study conducts in-depth analysis on the changing state of soil movement in wave-current co-existing fields (mountain, river, and coastal areas). The objective is to predict shoreline variation considering the environment of the Jeongdongjin Sea area by establishing a quantitative evaluation system of the effective sediment volume discharged from the area of river mouth bars. An effective sediment volume was evaluated using a sediment runoff model; the wave transformation for each survey line was calculated using SWAN to consider the wave characteristics acting on the sea area. The prediction performance was greatly improved by applying the mixed grain size to the soil in the sea area and by applying jetties to the reefs for upgrading the prediction of the shoreline variation. [ABSTRACT FROM AUTHOR]

Beck, T.M.; Wang, P.; Li, H., and Wu, W., 2020. Sediment bypassing pathways between tidal inlets and adjacent beaches. Journal of Coastal Research, 36(5), 897–914. Coconut Creek (Florida), ISSN 0749-0208. This study investigated the sediment transport pathways in three sandy barrier, tidal inlet systems through sediment tracking within a numerical model that simulates hydrodynamics and morphodynamics. The three tidal inlet systems, Coos Bay, Oregon, Shark River Inlet, New Jersey, and John's Pass, Florida, represented high-, medium-, and low-wave energy regimes for U.S. inlets (Pacific, Atlantic, and Gulf of Mexico Coasts, respectively). Three methods employed to define sediment pathways from the results of a numerical morphology model were evaluated: (1) morphodynamic interpretation, (2) mean transport vectors across the modeled inlet, and (3) sediment tracer migration. The sediment tracing methodology employed in this study allowed for an evaluation of the sediment transport pathways between the various morphologic features of a tidal inlet, as well as their respective processes that drive the exchange of sediments. Characterizing and correlating the dominant and subdominant, or seasonal, sediment pathways between tidal inlet morphologic features (sediment reservoirs) can improve long-term models of an inlet sediment system. Divergences in pathways to subfeature shoals of a complex tidal inlet shoal, such as the updrift and downdrift shoals of an ebb-tidal delta, can be resolved through tracking sediment migration. The results of this study illustrate the value of including sediment-tracking techniques in simulating sediment bypassing and the potential of this application to inform coastal engineering and design modifications to the sediment reservoirs of tidal inlet systems. [ABSTRACT FROM AUTHOR]

Sediment mobilization, especially from offshore bay to the coast during the Holocene, along the inner continental shelf of Bay of Biscay is less understood. Acoustic and sediment sampling and surveys were conducted offshore of the Bay of Étel to define the shallow geologic framework and the sedimentology. Results of these campaigns are used to identify and map Holocene deposits, discuss sediment transport pathways and depth of closure using Hallermeier's approach in order to define the active sedimentary prism using the depth of closure on a meso-tidal and wave dominated coast. In the Bay of Étel, Holocene sediments are concentrated between rocky shoals and emerged rocks, passing from external zone by sand lobe, 20 m thick to the medium zone, 15 m thick, to the beaches of the Gâvres-Penthièvre beach dune system (modern coastal prism). This case study found that the thickest deposits of Quaternary sediments observed along the inner shelf have a strong dependence on coastal topography and structural heritage. The presence of offshore basement shoal has been determined to have exercised control over sediment transfers from offshore to landward regions during the last marine inundation. Due to the lack of any significant modern fluvial input of sand in the region, the Holocene deposits are inferred to have been derived by reworking of relict Pleistocene and older inner-shelf deposits. Sediment textural trends and seafloor morphology from the medium zone to the beach dune system indicate an absence of relationships (linking) between the modern sedimentary prism and the potential source of sediment to the shoreline. [ABSTRACT FROM AUTHOR]

ABSTRACT Kolokythas, G.A.; Grigoriadis, D.G.E., and Dimas, A.A., 2018. Dynamic friction coefficient in formulas of bed-load transport induced by waves over vortex orbital ripples. Empirical formulas for the computation of bed sediment transport induced by wave propagation over sand ripples often depend on, among other parameters, the dynamic friction coefficient, μd, of the sand grain motion. Here, a new approach is presented for the determination of μd based on the physics of the interaction between flow and sediment transport. Specifically, the correlation of μd to the wave, ripple, and sand grain characteristics was obtained using coupled numerical simulations of the flow over the rippled bed, the bed-load transport, and the bed morphology evolution. Flow results were obtained by two different numerical methods, one for wave boundary layer flow and one for purely oscillatory flow, both based on the solution of the Navier-Stokes equations. The bed-load transport rate, which drives the bed morphology evolution, was computed using three different empirical formulas. The value of μd that leads to an equilibrium of the rippled bed profile after many wave periods was found to depend almost linearly on (Lr/ao)·(hr/ao), where, Lr is the ripple length, hr is the ripple height, and ao is the wave orbital motion amplitude. [ABSTRACT FROM AUTHOR]

ABSTRACT Solari, S.; Alonso, R., and Teixeira, L., 2018. Analysis of Coastal Vulnerability Along the Uruguayan Coasts. 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. 1536–1540. Coconut Creek (Florida), ISSN 0749-0208. The objective of this work is to identify the most vulnerable areas to coastal erosion on the Uruguayan coast. To this end, global wind and local waves and sea level reanalysis were used to estimate the littoral and aeolian sand transport rates (cross- and long-shore), the response of the beach profile to extreme events (by means of X-Beach model) and the supply of sand from rivers all along the Uruguayan coast, obtaining 18 years of three-hourly data. For each estimated variable, its intra- and inter-annual variability and its correlation with relevant climatic indexes were calculated. Using this information the sediment budget of the coast was analyzed at different scales: global (all the Uruguayan coast; O(100 km)), regional (physiographic units, O(10km)) and local (beach nodes; O(1km)). In turn, the above information was combined with a qualitative assessment of the coastal uses, obtaining a vulnerability index used to identify priority areas to undertake detailed studies. [ABSTRACT FROM AUTHOR]

ABSTRACT Shim, W.J. and Kim, C.W., 2018. The necessity of coastal management in Busan Considering human and natural conditions: The case of barrier islands in Nakdong-estuary. 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.1501–1505. Coconut Creek (Florida), ISSN 0749-0208. The Busan coasts have complex natural and human conditions including dynamic coastal, river processes and human activities. These complex natural and human factors have had direct and indirect impacts on the coastal areas of Busan, so a spatially integrated approach for management is required. Especially, the barrier islands located in the Nakdong River estuary are proper examples that show the effect of the sediment budget as natural and human conditions. This research aims to identify the effects of natural and human conditions on the barrier islands. The area of the barrier islands, sediment budget from the watershed, the amount of dredging at Nakdong-Estuarine-Dam and land use coverage were compared using correlation analysis. The more sediment eroded from watershed and the less sediment was dredged at Nakdong-Estuarine-Dam, the larger area of the barrier islands. This indicates that boundary conditions such as the supply of sediment from the rivers are related to the barrier islands; thus river and watershed management are important. Regarding land use, used and barren areas are positively correlated with the barrier islands, but water, forests and agricultural lands are negatively correlated. Internal factors within Busan, such as coastal modifications and urban growth, are affecting coastal dynamics, which change the sediment budget. These results show that the barrier islands sensitively respond to boundary conditions from the river and watershed and to internal conditions such as shoreline management and development. Therefore, for the effective management of Busan's coasts, it is necessary to consider how natural and human conditions interact spatially. [ABSTRACT FROM AUTHOR]

Wang, J.; Qu, Z.; Xu, Z.; Shim, J.S.; Liang, B., and Lee, D.Y., 2018. Measurement of Sediment Concentration of the Oscillatory Flow in the Surf- and Swash-zone.. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1231–1235. Coconut Creek (Florida), ISSN 0749-0208. The sediment transports near the bed need to be accurately observed to validate the existing models that are based on the empirical formula for the sediment flux and to develop more realistic morphology prediction model. One of the essential tasks for the evaluating the existing models and developing new one is the precise measurement of the sediment transport at swash zone without disturbing flow. Different methods in estimating the sediment transport rates at the surf-zone and swash-zone such as measuring the time evolution of the bed profile, sand ripple volume and migration speed are investigated and evaluated. To develop more reliable estimation of the sediment flux by measuring the vertical profiles of sediment concentration and velocity without disturbing the flow conditions, method of estimation of the vertical sediment concentration profile by detecting the backscattered light intensity using high quality camera was tested and evaluated. The problems of different methods in estimating the sediment flux are identified and discussed. [ABSTRACT FROM AUTHOR]

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]

Shi, H.Y.; You, Z.J.; Yin, B.S., and Bai, Y.C., 2018. Critical Depths Derived for Three Distinct Modes of Coastal Sediment Transport. 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. 271–275. Coconut Creek (Florida), ISSN 0749-0208. A unified criterion is developed for three distinct modes of coastal sediment transport: incipient movement of sediment (only bedload), initiation of bedripple formation (bedload and suspended load), and inception of bed ripple disappearance or sheet flow (mainly bed load) based on three unique laboratory datasets collected on a horizontal bed of sediment under regular waves. The onset velocity criterion on the three distinct sediment transport modesis derived to be of the same simple form, U0 = 2πC (1 − T0/T), where U0 is the maximum on set wave orbital velocity close to the bed, T is the wave period, and C and T0 are the coefficients dependent of sediment property only. The newly developed criterion is then extended to calculate critical depths for the distinct modes of sediment transport under coastal waves by replacing regular wave height H and period T with statistical wave height Hrms and period Trms according to the recently developed "zero-crossing and energy balance" wave analysis method and linear wave theory. The critical depth calculated from this unified criterion is shown to be a function of sediment grain size and density, and wave height and period, but more sensitive to wave period. The critical depth estimated for the initiation of bed sediment ripple formation is found to be much larger than the depth of closure derived for beach-fill designs. [ABSTRACT FROM AUTHOR]

Yuhi, M. and Umeda, S., 2018. Characteristics of systematic migrations of multiple sandbars and related cross-shore sediment transport at Chirihama and adjacent coasts, Japan. 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. 231–235. Coconut Creek (Florida), ISSN 0749-0208. Characteristics of systematic migration of multiple bar system on the Chirihama and adjacent coasts, Japan, have been investigated based on a set of annual field surveys collected over 11 years. The morphological variations were first separated into time-averaged profiles and deviation components. An EOF analysis was conducted on the deviation components in order to extract the principal modes of periodic bar migration. The migration cycle consisting of generation, migration and degeneration were well reproduced by the combination of first and second modes. The cross-shore sediment transport and sediment volume variation related to bar migration were then examined. An integration of the equation for sediment volume conservation revealed that the principal modes of cross-shore sediment transport was characterized by the spatial integration of spatial eigen-functions and the temporal derivative of the temporal eigen-functions. Corresponding to the cyclic behaviors of sandbar system, the direction of sediment transport changed alternatively between seaward and landward directions. On short-term, cyclic exchange of sediment occurred between the bar migration zone and foreshore, but on long-term the principal modes of bar migration made little contribution to overall sediment volume variation. [ABSTRACT FROM AUTHOR]

Small tidal inlets with an entrance width of less than 50 m or a cross-sectional area of less than 100 m2 have not been investigated as often as their larger counterparts. To discern the major processes responsible for entrance infilling in a small inlet system, the hydrosedimentological processes in the annually dredged Currumbin Creek (Australia) inlet system were investigated. Delft3D was applied and validated using local field measurements and regional data. A standalone regional hydrodynamic model and three nested standalone wave models provided detailed data for the offshore boundary of the more detailed creek entrance model, which was a coupled, local flow-wave-sediment transport model. The noncohesive sediment transport module was calibrated based on the volume of dredging and the net annual volume of longshore transport. The results of this hindcast model provided insight into the dominant processes responsible for the inlet's current configuration (i.e. significant refraction of incident waves to a nearly shore normal direction; a noteworthy onshore-offshore transfer of sediments; channel infilling induced by wave-induced currents; very limited sediment transport within the back-barrier lagoon because of an absence of wave-induced currents, as well as weak tide-induced currents; and infilling of the dredged area because of immersed slope stability, rather than hydrodynamic processes). Overall, the adopted modelling approach and the selected model setups proved to be a suitable combination of the available resources and tools to forecast the influence of any alteration to the current maintenance strategy. Accordingly, the identified physical processes and findings can be applied to similar cases with narrow inlet entrance widths and small back barriers with limited circulation. [ABSTRACT FROM AUTHOR]

Wang, P. and Beck, T.M., 2017. Determining dredge-induced turbidity and sediment plume settling within an intracoastal waterway system. The intracoastal waterway (IWW) is a continuous navigation channel that often extends across seagrass beds and other sensitive habitats throughout the Gulf and Atlantic Coast estuaries of the United States. Turbidity increase associated with an IWW dredging operation in west-central Florida and subsequent dredge plume subsidence were measured with optical backscatter sensors and acoustic Doppler velocimeters, which also measured in situ wave and current conditions. The field experiments were conducted over a dense seagrass bed. Sediment in the study area is dominantly composed of fine, well-sorted quartz sand, typical of Florida estuaries. The dredge plume temporally increased the turbidity to more than 400 mg/L around a midwater depth. The settling of the dredge plume and sediment resuspension were calculated with commonly used empirical formulas for noncohesive sediments and compared with field observations. The relatively energetic conditions generated by frequent boat wake did not result in significant resuspension and remixing of the suspended sediments and had minor influence on the settling time of the dredge plume. Findings from this study may provide information on understanding potential impacts of dredging on seagrass beds. [ABSTRACT FROM AUTHOR]

Olsen, M.J.; Johnstone, E.; Driscoll, N.; Kuester, F., and Ashford, S.A., 2016. Fate and transport of seacliff failure sediment in southern California. In: Brock, J.C.; Gesch, D.B.; Parrish, C.E.; Rogers, J.N., and Wright, C.W. (eds.), Advances in Topobathymetric Mapping, Models, and Applications. Journal of Coastal Research, Special Issue, No. 76, pp. 185-199. Coconut Creek (Florida), ISSN 0749-0208. Continual erosion and collapse of unstable seacliffs along the economically important coastline of San Diego County, California, threatens existing development and public safety. Frequent time-series mapping of the seacliffs and beaches provides valuable insight into the processes responsible for cliff erosion and into the reworking and transport of the failed material. High-resolution terrestrial laser scan (TLS) data provide quantitative data for analyzing seacliff morphology, capturing patterns over time and across a wide range of spatial scales. Through an ongoing 'rapid response' program operational since spring 2007, eleven substantial seacliff failure sites were mapped pre-collapse, immediately post-collapse, and repeatedly after the collapse to constrain processes causing cliff failure and estimate the rate at which failed material is reworked. Comparison of the TLS data with water levels and climate data highlights the contributing mechanisms to the seacliff failures and the rapid reworking of the failed material. Failure sites were categorized based on the frequency of wave contact ( i.e., total water level) compared with the beach elevation to assess differences in the rates of sediment reworking. For example, unconsolidated failed material on the beach was reworked quickly by waves at sites where waves reached the failure on a nearly daily basis. Conversely, other failure masses with less wave contact were only reworked during storm events producing larger waves. At sites where the failure material consisted of large boulders, there are feedback mechanisms at play where the failed material protects the cliff toe by stabilizing talus deposits, akin to riprap engineering techniques. Failures due to wave undercutting and notching were observed to migrate laterally at these sites. This lateral progression of failures might explain the long-term linear retreat of the seacliffs in the region, which minimizes the development of embayments and promontories. [ABSTRACT FROM AUTHOR]

Kong, J.; Pan, M.; Shen, C.; Hua, G., and Zhao, H., 2016. Analysis of the morphological changes and related sediment transport mechanisms of the Baisha Shoal in the Qiongzhou Strait, China. The morphological changes and evolutionary mechanism of the Baisha Shoal in the Qiongzhou Strait were investigated using various methods, including bathymetric chart comparisons, geomodeling, hydrodynamic modeling, and hydrologic statistical analysis. Water depths were extracted from digitized charts to explore the evolution of the Baisha Shoal and to quantitatively estimate the changes in the shoal area within the 5-m isobath. The grain-size trend analysis (GSTA) model was introduced to explain the features of bed sediment distribution and to analyze the sources of the sediment. Tidal flow models and wave models were adopted to simulate the tidal flows and wave fields around the Baisha Shoal and to reveal the sediment transport dynamics. Further comparisons based on a Mann-Kendall trend analysis and remote-sensing image data from different years were used to discuss the reason for the recent evolution of the Baisha Shoal. The results show that the formation of the Baisha Shoal was caused by the combined effects of reciprocating flow in the eastern and western directions and waves from the NE direction. However, in recent years, the Baisha Shoal has demonstrated an unsteady geomorphological state and is transitioning from a deposition-dominated state to an erosion-dominated state. Erosion has become most significant since 2004, as reflected in the shoal area within the 5-m isobath, which is decreasing by 0.732 km2/y. The analysis demonstrated that a reduction in sediment load and increased sand mining are the two most significant factors that are progressively altering the shoal morphology. If these issues cannot be resolved, the strong dynamic surroundings will aggravate the erosion of the Baisha Shoal. This study on the Baisha Shoal highlights the necessity of combining different approaches to better understand coastal evolutionary features, dynamic mechanisms, and evolutionary causes, as well as to guide future coastal protection engineering design. [ABSTRACT FROM AUTHOR]

Gibeault, C.; Neumeier, U., and Bernatchez, P., 2016. Spatial and temporal sediment dynamics in a subarctic salt marsh (Gulf of St. Lawrence, Canada). Sediment transport in the salt marsh and the lagoon of Penouille is driven by tidal currents, waves, wind, and ice rafting, which interact with topography and vegetation to control the spatial distribution of surface sediments. Multiple linear regressions of 203 samples of marsh surface sediments show that grain size gets finer and organic matter content increases with distance from the lagoon inlet, the sandy peninsula, the closest creek, and the lagoon. The vegetation parameters and surface microtopography have only a minor influence. Locally, grain size can get finer with elevation, while organic matter content increases. However, across the entire marsh, grain size exhibits the opposite trend with elevation, a consequence of aeolian transport and ice rafting. The 94 samples covering the lagoon show a trend of finer grain size with distance from the lagoon inlet and with sea grass cover. Penouille marsh has been relatively stable from 1975 to 2008: analysis of five georeferenced aerial photographs shows that only 3% of the marsh area was lost due to outer marsh edge retreat. Ten sediment cores collected in the marsh show a thickness of 0.14-0.72 m of marsh sediments overlying a sandy substrate. Radiocarbon dates suggest that marsh establishment occurred in the north side of the lagoon around 1000-1200 cal BP. Accretion rates based on radiocarbon dates are 0.4-1 mm/y for several centuries, whereas 137Cs dating indicates rates of 1-3 mm/y since 1963, and accretion plates indicate 2.9 ± 0.9 mm/y between 2010 and 2012. Accretion rates since 1963 are similar to the relative sea-level rise (RSLR) of 1.5 mm/y at Penouille for the 1969-2014 period. However, the accelerated RSLR of 3.7 mm/y observed over the last 20 years and additional RSLR due to climate change may progressively drown the marsh if accretion rate does not substantially increase. [ABSTRACT FROM AUTHOR]

Dalledonne, G. L., and Mayerle, R., 2016. Modelling of storm impacts on the Shandong peninsula coast. This paper presents results of the investigation of the effect of storms on the morphodynamics of the Yantai coastal areas in the Shandong Peninsula, China. A two-dimensional depth integrated morphodynamic model for prediction of the morphological changes during extreme events was developed and applied. The model covers the entire Bohai Sea with increasing grid resolution towards the coastal areas near Yantai. Calibration and validation using tidal constituents and measured water levels and current velocities showed that the model is capable of predicting the hydrodynamics in good agreement with observations. Emphasis was given to the proper description of the spatial distribution of the seabed sediments and bed stratigraphy. The 20 most severe storms observed in the region from 2000 to 2013 were identified and reconstructed. Storm surges with increases in mean sea level of up to 1.7 m and significant wave heights up to 4.1 m were considered. The results showed that during the storms the levels of energy are mainly due to waves and tidal currents are only relevant at the capes and some channels and straits along the Shandong Peninsula. The resulting morphological changes indicated that although there is an overall loss of seabed material, particularly during the peak of the storms, the beaches near Yantai recover quite quickly just a few days after the extreme events. [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]

Hale, R.; Jacques, R.O., and Tolhurst, T.J., 2015. Cryogenic defaunation of sediments in the field. Ecological experiments designed to examine the effects of macrofaunal biodiversity may require the defaunation of intertidal sediments; however, many current techniques result in physical disruption of the sediments. A method of field-based cryogenic defaunation, which has advantages over existing methodologies, was developed to provide macrofaunal defaunation of intertidal cohesive sediment with minimum physical disruption. A sediment core transport apparatus and polystyrene freezing chamber allow the use of liquid nitrogen for effective freezing of a whole core of sediment in the field. Freezing the whole core intact minimises physical disturbance to the sediment and retains the topography of the sediment surface and sediment grain distribution with minimal effect on sediment properties and the microphytobenthos. This method is effective at removing up to 97% of infaunal macrofauna abundance from the sediment. Hediste diversicolor were found to be the most resistant species, with a 71% reduction in species abundance. Sediments defaunated in this way can be replaced in situ or removed to the laboratory for experimentation. This method of cryogenic defaunation would also be suitable for the defaunation of other marine or terrestrial sediments. [ABSTRACT FROM AUTHOR]

The Solís Chico river, located on the southern Uruguayan coast, flows into the Río de la Plata estuary. The seaside resorts La Floresta and Parque del Plata are located on the estuary. In recent years the river mouth has migrated westward, away from the river axis, forming a sand spit that hinders the recreational use of Parque del Plata beach. In turn, at La Floresta there is a beach nourishment project whose main objective is to mitigate the erosion of the beach and the adjoining cliffs. This work aims to identify the causes of the recent migration of the river mouth and to analyze the possibility of using the sand spit as a borrow area for the beach nourishment. The river sediment supply to the coast for the period 1900-2010 was estimated, along with the long-shore and cross-shore sediment transport produced by sea waves. Furthermore, the plan-view stability of the river was studied in order to determine if the long-term evolution of the river is affecting the migration of the mouth. It was found that the migration of the mouth is mainly due to an extraordinarily high river sediment supply in 2002, combined with an increase in the net westward potential long-shore transport rate since the late 90s, and that the meander dynamics of the river are not affecting the evolution of the mouth. Additionally, the most likely area of natural breaching of the sand spit was identified, recommending its use as a borrow area for nearby beach nourishment. [ABSTRACT FROM AUTHOR]

Our current understanding of the morphodynamics in swash and surf zones is limited due to their turbulent and irregular nature. The importance of this zone to sediment transport led us to perform a sophisticated field experiment using painted sediments. Sediments collected locally from beach ridges were sorted into the following diameters: 1-2.5 cm, 2.5-5 cm and 5-10 cm. The sediments were painted, amassed in piles and placed at 0.5-10 m depths in three sites near the Estonian coast. The locations were recorded with GPS devices and photographed. The sediment piles placed in the sea were monitored at least once after an intense storm or once before and after the storm season. Some sediments were placed on the shoreline and monitored daily for a shorter period. Hydrodynamic parameters were also measured or hindcasted during the experiment. We found that wave breaking during storms can take place even at 6 m depth, but mostly between 2-4 m depth. Sediment fractions between 1-10 cm diameters can be transported over 20 m towards the shore. Even sediment piles at 10 m depth were moved 2-4 m, but towards the open sea. Sediments accumulated on the shoreline moved up to 3 m/hour along the shore and approximately 350 m during three months. We also found that calm periods can be more influential in places where regular vessel-generated waves wash the shores. As vesselgenerated waves often approach from a different angle than natural waves, they can cause notable erosion during the periods when natural waves are weak or absent. [ABSTRACT FROM AUTHOR]

Ahmed, M.T.T.; Sato, S., and Tajima, Y., 2014. Quantitative estimation of longshore sediment transport based on thermoluminescence: two case studies around Tenryu and Nile River mouths. Longshore sediment transport (LST) is one of the key factors determining coastal deformation. Appropriate understanding of LST is thus essential to sustain coastal management and propose efficient countermeasures. However, it is quite difficult to quantify LST where detailed information of waves and bathymetries is not available. This study provides a novel methodology for quantitative estimation of LST by utilizing the residual thermoluminescence (TL) properties of feldspar grains. A newly proposed TL-based system estimates LST as a function of alongshore distributions of TL and dominant wave heights at the study sites. This study first analyzed and developed the TL-based bleaching curves due to sun exposure of the 180-300 μm fraction of feldspar grains from three different regions: Egypt, Japan, and Sri Lanka. On the basis of the obtained bleaching curves, the spatial distribution of TL along the coast was estimated, and the alongshore slope of TL decay was compared with the locally estimated average longshore current velocity, mixing sand layers, and moving sand volume, all of which were subsequently linked to LST. The newly proposed methodology was applied to two coastal areas around the Tenryu River and Nile River mouths, and it was found that the proposed methodology is capable of estimating directions and amount of LST around river mouths where sand with high TL is discharged continuously. [ABSTRACT FROM AUTHOR]

Vila-Concejo, A. Harris, D.L., Shannon, A.M., Webster, J.M., and, Power, H.E., 2013. Coral reef sediment dynamics: evidence of sand-apron evolution on a daily and decadal scale This paper investigates sand apron progradation on decadal and daily scales on a platform reef (One Tree Reef, OTR) located in the southern Great Barrier Reef. The decadal scale is addressed by analysing sand apron progradation using remotely sensed images (aerial photos and satellite imagery) coupled with wind data and cyclone events. The daily scale is addressed through a field campaign that was undertaken in September-October 2011. The campaign consisted of hydrodynamic measurements in three stations over the southern sand apron in OTR. It was found that while there was a small overall progradation over the last 31 years, the progradation had not occurred continuously or consistently along the entire sand apron. Additionally, the effect of cyclones was not clear on the decadal scale. On the daily scale, it was found that currents are generally weak (<0.4 m/s) and that currents during conditions at which suspended sediment is maximized are ocean-ward directed on the central part of the sand apron and lagoon-ward directed on the easternmost end. As such, daily sediment transport does not represent a gross contribution to lagoon infilling by sand apron progradation. Our results show that sand apron progradation does not occur continuously on the decadal or the daily scale. [ABSTRACT FROM AUTHOR]

The hydrodynamic and morphodynamic parameters of a region in southern Brazil were determined by collecting sediments with stream traps (bedload and suspended load) in the surfzone and capturing images, studying topography, and researching sedimentology with the help of a movie camera, a total station, and laboratory work. Data on deep-water waves were garnered with a CPTEC/INPE model. Field work was carried out in 50 field trips during a 1-year period; 42 out of 50 trips focused exclusively on hydrodynamic and morphodynamic data, whereas eight of the trips were also used for collecting sediments. In addition, data on wind direction and velocity and on the longshore currents were also collected. All data were obtained in normal atmospheric conditions. Field work was carried out in six cross-shore profiles along Cassino Beach and Mar Grosso Beach (three profiles on each side of the estuary of Patos Lagoon). [ABSTRACT FROM AUTHOR]

Sediment budget analyses along the south shore of Fire Island, New York, have been conducted and debated in the scientific and coastal engineering literature for decades. It is well documented that a primary component of sediment transport in this system is directed alongshore from E to W, but discrepancies in volumetric sediment budget calculations remain. An additional quantity of sand, averaging about 200,000 m3/y is required to explain the growth of the western segment of the barrier island, a prograding spit. Littoral sediment derived from updrift erosion of the coast, addition of beach nourishment fill, and onshore transport of inner continental shelf, shoreface sediments, or both have all been proposed as potential sources of the additional sediment needed to balance the sediment budget deficit. Analysis of highresolution seafloor mapping data collected in 2011, including seismic reflection profiles and inteferometric sonar acoustic backscatter and swath bathymetry; comparison with seafloor mapping data collected in 1996-1997; and shoreline change analysis from 1933 to 2011 support previous suggestions that the inner-shelf Holocene sedimentary deposit is a likely source to resolve this sediment budget discrepancy. [ABSTRACT FROM AUTHOR]

Fine sediment (silt and clay) plays an important role in the physical, ecological, and environmental conditions of coastal systems, yet little is known about the dispersal and fate of fine sediment across coastal margin settings outside of river mouths. Here I provide simple physical scaling and detailed monitoring of a beach nourishment project near Imperial Beach, California, with a high portion of fines (~40% silt and clay by weight). These results provide insights into the pathways and residence times of fine sediment transport across a wave-dominated coastal margin. Monitoring of the project used physical, optical, acoustic, and remote sensing techniques to track the fine portion of the nourishment sediment. The initial transport of fine sediment from the beach was influenced strongly by longshore currents of the surf zone that were established in response to the approach angles of the waves. The mean residence time of fine sediment in the surf zone-once it was suspended-was approximately 1 hour, and rapid decreases in surf zone fine sediment concentrations along the beach resulted from mixing and offshore transport in turbid rip heads. For example, during a day with oblique wave directions and surf zone longshore currents of approximately 25 cm/s, the offshore losses of fine sediment in rips resulted in a 95% reduction in alongshore surf zone fine sediment flux within 1 km of the nourishment site. However, because of the direct placement of nourishment sediment on the beach, fine suspended-sediment concentrations in the swash zone remained elevated for several days after nourishment, while fine sediment was winnowed from the beach. Once offshore of the surf zone, fine sediment settled downward in the water column and was observed to transport along and across the inner shelf. Vertically sheared currents influenced the directions and rates of fine sediment transport on the shelf. Sedimentation of fine sediment was greatest on the seafloor directly offshore of the nourishment site. However, a mass balance of sediment suggests that the majority of the fine sediment moved far away (over 2 km) from the nourishment site or to water depths greater than 10 m, where fine sediment represents a substantial portion of the bed material. Thus, the fate of fine sediment in nearshore waters was influenced strongly by wave conditions, surf zone and rip current transport, and the vertical density and flow conditions of coastal waters. [ABSTRACT FROM AUTHOR]

Devastating tsunami waves can mobilize a substantial amount of coastal sediments and change the coastal morphology considerably. In this study, laboratory experiments were performed in a wave flume to investigate the changes of beach profile and mean grain size caused by tsunami-like waves that have a front similar to that of a solitary wave and an undulating tail following the wave front. A composite slope was constructed using a mixture of two sizes of sand. In addition to recording the wave rush-up and rush-down processes using video cameras, measurements were also made on water surface elevation, bed profile and the final size distribution of the sand mixture for three water depths. The results showed that sand suspension and erosion were caused mainly by sheet flows when water retreats from the beach, whereas the offshore sandbars, composed mainly of coarser sand, formed mainly from the run-down jumps caused by the collapsing of retreating water with waves in the undulating tail. The findings of this study have the potential to assist researchers in understanding nearshore tsunami flows from tsunami deposits. [ABSTRACT FROM AUTHOR]

This contribution is part of the Gulf Regional Sediment Management Master Plan and serves as a broad overview of the general setting, geologic history, coastal processes, hydrodynamics, and sediment sources for the Gulf of Mexico (GOM). The GOM is approximately 1,500,000 km2. The five U.S. states bordering the Gulf comprise over 75,000 km of coastline. Gulf circulation is dominated by the Loop Current and gyres. The general trend of longshore sediment transport is in the westward direction west of the Mississippi River and in the eastward direction east of the Mississippi River, and is driven primarily by the wave and tidal energy. The GOM is a shallow basin and its climate is strongly dependent on precipitation and temperature averages. The general coastal climate is subtropical with warm to hot summers and cool winters with precipitation and high relative humidity throughout the year. The GOM coast is predominantly microtidal (<2-m range) with coastal processes and associated morphodynamics strongly influenced by storms. Tropical cyclones have affected every GOM coastal county or parish since 1900. Over 150 rivers flow into the Gulf; 85% of the fluvial water contribution is from U.S. rivers and of that, 64% is from the Mississippi River, which discharges approximately 2.4 billion kg of sediment annually. Humans are altering the natural coastal sediment budget through beach nourishment and dredging that affects the beach-dune sediment exchange. Six of the 10 most socioeconomically vulnerable coastal counties in the United States are in the Gulf region, which emphasizes the need for a sediment management master plan. [ABSTRACT FROM AUTHOR]

A partnership has been instituted through the Gulf of Mexico Alliance (GOMA) among the Gulf States to enhance the ecological and economic health of the Gulf of Mexico. Established under the GOMA, the Habitat Conservation and Restoration Team (HCRT) recognized that sediments are integral to and a critical resource in accomplishing the GOMA conservation and restoration objectives. As a result, the Gulf Regional Sediment Management Master Plan (GRSMMP) was initiated for managing sediment resources and corroborates the need for an understanding of regional sediment processes. The plan provides guidelines using the understanding of sediment dynamics to manage resources toward accomplishing environmental restoration, conservation, and preservation while enhancing abilities to make informed, management decisions. A key step in this process is the recognition of a technical framework that provides a foundation associated with regional sediment management processes essential for establishing management guidelines that balance sediment dynamics and available sediment resources with needs and that enhance abilities to make informed management decisions and develop regional strategies. Issues surrounding sediment management, both natural and dredged sediments, have a considerable impact on the ability to sustain coastal habitats. Sediment management must occur on a regional scale unencumbered by agency, state, or political boundaries. Guidelines and recommendations from this effort will aid the Gulf States in more effective management of sediment resources, recognizing they are a part of a regional system involving natural and man- made processes. The effort involves a range of state and federal agencies, as well as nongovernmental representatives. Thus, a technical framework for the GRSMMP was compiled/completed and submitted to the HCRT/GOMA. The decision was made to publish this document as peer-reviewed papers in a special issue of the Journal of Coastal Research for benefit of the global scientific community. In return, feedback in terms of review and comments will be beneficial for the team. [ABSTRACT FROM AUTHOR]

This article defines short-term (tidal cycle) sediment-transport patterns at a backbarrier beach based on detailed field studies. Fieldwork was planned to record nonstorm, spring tide conditions that enable the definition of background sediment dynamics at the study area. The experiment was set at two beach morphologies: beach face and sandbank. Current meters were deployed at both sites. Fluorescent tracer techniques were applied to determine rates and direction of transport. Topographic surveys and sediment sampling were undertaken. During the experiment, limited tracer displacement and small morphological changes occurred. The low magnitude changes are representative of predominant, low-energy hydrodynamic conditions. Sediment transport was primarily longshore orientated and dependent on the velocity of tidal currents. Tidal currents had the potential for sediment transport only during a short period of the tidal cycle and had higher velocities during ebb, which results in a net sediment transport orientated towards the nearby inlet. It is suggested that there is dependence on sediment transport rate at the study site and on the variability of tidal currents, which are greatly influenced by the distance to, and conditions of, the nearby Ancão Inlet. [ABSTRACT FROM AUTHOR]

This study evaluated the potential increase in shoaling and associated sources of sediment as a result of proposed channel improvements for the Houma Navigation Channel in the vicinity of Cat Island Pass, Louisiana. Using morphologic change data and historical maintenance dredging rates, historical and forecasted with-deepening sediment budgets were developed. Conclusions from this study were that deepening the channel from 5.5 m to 6.1 m relative to Mean Low Gulf, a local low water datum, would increase the shoaling rate from the present 191,000 m3/year to 220,000 m3/year, and the likely source of shoaling would be sediment that is presently bypassed naturally. It was recommended that all environmentally-acceptable sediment dredged from Cat Island Pass be placed on the downdrift barrier island, East Island, part of the Isle Dernieres barrier island system. Clays and silts should be placed on the bayside of the island and sand similar to or coarser than the existing beach sand should be placed downdrift of the nodal zone on the Gulf side of East Island. Historically, sediment dredged from Cat Island Pass has been placed in designated dredged material disposal sites located 760 m west of the channel. Based on morphologic change in the region from 1980 to 2006, it appears that sediment may be transported from this placement site to deposit back into the channel. It is recommended that, if sediment cannot be placed on either East Island or Timbalier Island, that the dredged material disposal site be moved further to the west, away from the channel. Finally, based on movement of Timbalier Island and Cat Island Pass over the past 100 years, it is recommended that the channel be moved further to the west to avoid future impingement by Timbalier Island. Based on the results of this and other studies of the Houma Navigation Channel, channel realignment was approved in 2009, and authorization of the deepened channel is being requested during 2010. [ABSTRACT FROM AUTHOR]

This paper examines the short-term evolution of a cuspate foreland with diminished sediment supply in the western Gulf of St. Lawrence. Topographic light detection and ranging and airborne light detection and ranging bathymetry are used to provide an overall analysis of the foreland system at Paspébiac, Quebec, including high-resolution digital morphology of combined subaerial and subaqueous components, between 2003 and 2006. Results indicate large differences in coastal stability around the foreland. The western barrier exhibits a stable shoreline (net change = +0.3 m·y-1), a moderate beach slope (0.12-0.18), and no subtidal bar system. The morphodynamic response in this sector is influenced by jetties and alongshore variability and is related to beach planform readjustments to varying wave conditions. The eastern barrier has higher wave exposure, high erosion rates (<6.7 m·y-1), wave washover, and an intermediate barred-beach profile, with higher beach slopes (β 5 0.16-0.24). The alongshore variability is controlled, at length scales of about 500 to 700 m, by differences in relaxation time between distal and proximal sections of the foreland. At shorter length scales (∼100-500 m), alongshore variation is related to inner bar morphology, higher erosion rates being observed near rip channels or in the absence of an inner bar. Sand transport patterns reflect wave energy and approach and include a reversal in transport direction along the eastern barrier under storm waves from the SW. We show that, under declining sediment supply, sediment is being lost to a shoal and deep water off the tip of the foreland and erosion on the eastern barrier is not compensated by the slow accretion on the western side of the point. [ABSTRACT FROM AUTHOR]

Sediment transport between the emerged land masses and deep marine basins is a fundamental process that affects the exploitation of resources and protection of the environment and its ecosystems. Sediment transport models on the continental shelf are often very complex and subject to semiempirical or empirical equilibrium transport equations that relate sediment fluxes and turbulence to physical properties such as velocity, depth, and characteristic bed-load sediment particle sizes. In engineering applications, errors in these physical properties affect the accuracy of the sediment fluxes. The present analysis details the importance of physical properties to the bed-load fluxes and suggests which parameters have more influence on the final result by providing insight into the relative strengths, weaknesses, and limitations of all the selected 52 bed-load equations for noncohesive particles (sand and gravel are treated separately). Various parameters were first investigated individually to pinpoint the key physical properties that control the errors. Because the existence of strong nonlinearity in most bed-load transport equations precludes analytical approaches, the multilinear regression (MLR) method was used to validate this analysis. Several graphs are presented to emphasize the influencing effect of those parameters that were either used directly or embedded in these equations. The most significant parameters that directly influence the sand particles are θ, ds, and vav, and the embedded parameters are sfτo, θds, and Sfθ. On the other hand, for gravel particles, the most significant parameters are θ, ds, and θcr and qs*, Sfθ, and sfτo, respectively. [ABSTRACT FROM AUTHOR]

The mouth of the Guadiaro River (SW Spain), oriented in a NE-SW direction, is often closed, resulting in environmental, social, and economic problems. An analysis of the factors influencing this phenomenon was performed using the Coastal Modeling System, a numerical model based on the mild slope equation (waves, currents, and sediment transport), and a coastal evolution study was performed comparing aerial photographs to the monitoring campaigns carried out in 2005 and 2006 (topographic surveys, current meters, tidal gauges, and water quality parameters). Global transport at the Spanish south Mediterranean coast occurs in a southwestern direction. However, the spit that closes the Guadiaro River grows in the opposite direction. The points and conditions where transport direction changes occur along the coastline were identified. The results, obtained from 200 different propagations, were consistent with field data, showing that northeastern littoral transport during easterly waves was sufficient to block the river mouth. Furthermore, significant differences in sediment transport patterns were found despite the existence of a fixed wave power direction. Through this research we also learned that use of wave propagation numerical models by nonexperts is prone to error, as small variations in input parameters can induce dramatically different results that may be contradictory in certain bathymetric configurations. [ABSTRACT FROM AUTHOR]

On many tidal flats, there is a transition from sand flat at the more energetic seaward margin to mudflat further inland. However, the ability of sand flats to attenuate incident wave energy is an important but poorly understood constraint on mudflat development and morphology. This paper presents the results of an instrumented field study of incident wave attenuation across Roberts Bank, the sandy intertidal portion of the Fraser River Delta. The attenuation of wave height was monitored at four stations along a shore-normal transect for a period of 2 months (December 23, 2003, to February 10, 2004). The attenuation varied with the relative wave height ratio (Hs h-1 ≈) along the seaward margin, with dissipation increasing as water depths decrease and/or incident wave heights increase. Under the most dissipative conditions observed (Hs h-1 ≈0.25), the exponential decay coefficient reached 0.00045. This decay coefficient is an order of magnitude smaller than predicted by a simple wave transformation model due to the relatively large wind fetch over the sand flat. Despite the maintenance of wave energy, the range of wave heights remains constrained in the landward direction, with the frequency of waves capable of entraining sediment on the sand flat decreasing from 11% at the outer flat to 2% at the inner stations. In response, bed elevation change and depth of sediment activation are greatest at the seaward margin and decrease exponentially landward. It is argued that the sand flat provides a natural barrier that defines the extent of mudflat development by limiting the potential for sediment resuspension and morphological change on the mudflat. [ABSTRACT FROM AUTHOR]

Waves and currents were monitored over a range of incident forcing between March 23 and April 24, 2003, on Roberts Bank, the sandy intertidal portion of the Fraser River Delta. A comparison of the dimensionless, current-induced skin friction with the critical skin friction for the initiation of sediment motion suggests that the currents are only capable of entraining sediment briefly with the ebbing tide or when enhanced by the wind. Since these wind-generated currents are associated with storm waves, which typically exceed the critical skin friction, they have a disproportionately large impact on the direction of the sediment transport. An energetics-based model, driven by locally measured near-bottom currents, is used to characterize the rate and direction of bedload and suspended load transport. The largest transport rates were predicted in response to storm waves and were initially directed onshore with weak oscillatory transport and alongshore by wind-generated currents that turned offshore as the ebbing currents strengthened. The integrated transport (over the duration of the study) was predicted to be weakly offshore, but this is ascribed to the coincidental occurrence of storm activity with the ebbing tide. It is argued that if storm waves were equally distributed between the flood and ebb phases of the tide, the wind-generated currents and oscillatory transport would lead to a partly onshore-directed net transport during storms, which may in turn lead to tidal flat accretion. This suggests that sand flats are morphodynamically different than mudflats and open beaches, although further study is required to ascertain the link between the small-scale observations of this study and the larger-scale transport pathways that are ultimately responsible for tidal flat morphology. [ABSTRACT FROM AUTHOR]

Long-term studies (1989-2007) of the gravel beaches in Prince William Sound, Alaska, conducted as part of the Exxon Valdez oil spill monitoring programs, provide the basis for understanding the geomorphology and sediment dynamics of these intermittently exposed, coarse-grained gravel beaches. There are key differences between these beaches and open-ocean gravel beaches, including bermlike ridges that occur at different levels on the beach as a result of the diurnal inequality of the tides. The 1964 earthquake, with up to 3.5 m of uplift, provided information on sediment transport patterns and rates. In less than 25 years, a stable cobble/boulder armor formed on the upper and lower platforms, and the beaches reached a steady-state or graded condition. Eighteen years after the spill, oiled sediments were still present at depths greater than about 25 cm on beaches with a stable armor in the middle and lower intertidal zones. Cleanup efforts to remove the deep oil penetration into the porous gravel of the upper intertidal zone provided an indicator of short-term rates of sediment erosion and deposition. Where the high-tide berms were pushed onto the middle intertidal zone, they quickly reformed, usually after a few storms. However, the storm berm that was relocated for 2000 m along one of the most exposed shorelines in Prince William Sound took 6 years to recover. Data on the occurrence of gravel beaches in North America show that they are most common (comprise 48% of the shoreline) on paraglacial, leading-edge coasts and least common on nonparaglacial, trailing-edge coasts (~2% of the shoreline). [ABSTRACT FROM AUTHOR]

The thermoluminescence (TL) properties of feldspar were used to investigate the sediment movement processes in a fluvial-coastal system. Field samples were collected at various locations along the Tenryu River and the Enshunada Coast in Japan. After a series of pretests, an appropriate TL measuring sequence was proposed for this study. Applying this approach, the natural TL intensity of feldspar grains was measured. Owing to the young age of the research area, it was assumed that the natural TL difference was ascribed to the sample depositional environment under which different possibilities of sunlight exposure exist. Surface sediment particles in the target area were classified into three groups in terms of TL intensities, i.e., river sand with large TL signals, coastal sand with medium TL signals, and dune sand with small TL signals. Stratified configuration of the Nakatajima Coastal Dune was observed from the underground-sample TL glow curves with a top, windblown, dune-sand layer; a bottom, wave-induced, coastal sand layer; and a mixing layer in between. A rather complex sediment-movement pattern in front of the Tenryu River mouth was revealed after investigation of the underwater samples. Because of the seawater influence, acting as an ultraviolet filter to sunlight, underwater samples present a larger, high-temperature TL peak than the low-temperature peak; whereas these two are almost the same for ground samples. [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]

Experiments were conducted in the Large-scale Sediment Transport Facility (LSTF) at the U.S. Army Engineer Research and Development Center to investigate the importance of wave height, period, and breaker type (spilling and plunging breakers) on total rate of longshore sediment transport (LST) and the cross-shore distribution of LST. Estimates computed by the CERC formula and Kamphius were compared to the accurately measured total LST rates. Several K-values were used with the CERC formula, including the recommended value of 0.39 and calculated values by Kamphuis and Readshaw, Ozhan, Bailard, and Del Valle et al. The recommended K-value and most of the calculated K-values overpredicted the measured total LST rates, but methods that included parameters to indicate breaker type gave good estimates. The Kamphuis and Readshaw equation, in which K is a function of surf similarity parameter, gave consistent estimates with measurements. The Kamphuis equation, which includes wave period and beach slope that in turn influences wave breaking, also compared well with the measurements. Additionally, the CERC formula has been used successfully if K is calibrated, and the formula gave excellent results if K was calibrated with measured data and applied to similar breaker types. The findings indicate that total LST rate is strongly influenced by breaker type. The cross-shore distribution of LST indicated three distinct zones of transport: the incipient breaker zone, the inner surf zone, and the swash zone. Transport in the incipient breaker zone was influenced by breaker type. Transport in the inner surf zone indicated that wave height was the dominating factor and independent of wave period. Swash zone transport, which accounted for a significant percentage of the total transport, showed a dependence on wave height, period, and beach slope. [ABSTRACT FROM AUTHOR]

In order to understand regional variations in coastal behavior on Prince Edward Island, Canada, we investigated the role of Milne Bank, a submarine bank at East Point, the eastern tip of the island. The objective was to determine how the bank might facilitate transfer sediment from the eroding north coast to the adjacent sediment-rich south coast. The study utilized grain-size and seismic data collected on Milne Bank in 1989 and multibeam sonar surveys in 1997 and 1999. The disturbing effect of East Point on the hydrodynamic regime controls sediment transport. The northern boundary of the bank is a steep sand wave located where southward tidal and wave-driven currents rounding East Point suddenly decelerate. Sand from the north coast enters Milne Bank and is carried south in a field of migrating sand waves that are shed from the northern bounding sand wave toward the prograding end of the bank. Milne Bank is a major sediment sink, rather than a link between the eroding north coast and the sediment-rich south-facing coast. Longshore transport in nearshore bars is more likely to be responsible for continued sediment accumulation on the south coast. Embayments on the south coast have filled up in a cascading fashion, each one facilitating sediment bypassing when it has reached full capacity. [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]

The Maspalomas dune field and adjacent beaches are the most extensive coastal sedimentary environment on the island of Gran Canaria. This area is very important from both a natural and an economic perspective. The analysis of aerial photographs and satellite images from recent decades does not show important shoreline changes for the El Inglés and Maspalomas beaches, which can be considered, consequently, in a state of equilibrium. However, the Maspalomas dune field presents several modifications, such as aeolian corridors associated with beach kiosks, a significant reduction in thickness of the aeolian deposits, and an increase of deflation areas in the underlying substratum. All these are proof of a drastic reduction in sediments. Sediment transport pathways obtained from the grain size parameters of beach samples show an input of sediments from El Inglés beach to Maspalomas dune field, whereas longshore drift is predominant on Maspalomas beach. This grain-scale analysis agrees with previous geomorphologic and wind studies. Foraminiferal content analysis also confirms the input of sediments from El Inglés beach to the dune field, as well as indicating the lack of inputs across Maspalomas beach, on which only seaward fluxes from closer dunes can be expected. Input and sinking areas of the system have been confirmed as well as a notable lack of sediments in the dune area, which is suffering severe erosion because of the shortage of sediment supplies from El Inglés beach. [ABSTRACT FROM AUTHOR]

The mechanism of the threshold of sediment motion under wave action has been investigated by examining the dynamic forces acting on the sediment particle. The force analysis has led to a range of nondimensional parameters of clear physical significance, which are then applied to the analysis of a range of existing experimental data. The introduction of some new nondimensional parameters has resulted in significant improvement in the definition of the threshold of motion condition. Several empirical equations involving different nondimensional parameters have been derived, providing a mathematical description of the threshold condition of the sediment motion. The accuracy of these empirical equations is examined in the context of scientific and engineering applications and a simple equation is recommended for its accuracy and ease of use. [ABSTRACT FROM AUTHOR]

Forty-nine sediments were sampled along the coast of the Seine bay: 19 from the Port-en-Bessin harbor and 30 from the Bay des Veys. Metallic and polychlorinated biphenyl contaminations were estimated in harbor sediments by their comparison to the OSPAR Convention guidelines. Sediments in Bay des Veys were considered as nonpolluted materials and metal concentrations were chosen as regional reference data to calculate anthropogenic factor and gave human contributions of each metal in harbor sediments. The source of the principal pollutants was principally associated with the careening activities and the use of antifouling paints. A statistical study of data showed strong relationships between metals, organic matter, and fine-grained fraction (<50 μm) of sediments, assuming mobility of metals to water column in case of removal. [ABSTRACT FROM AUTHOR]

The greatest change in particle roundness, sphericity, and size in most fluvial systems generally occurs in the initial first few kilometers of sediment transport. Observations in natural settings and laboratory experiments have shown that changes, such as increased grain rounding and decreased size due to particle breakage, wear, and attrition, tend to be progressive along the dispersal path. In marked contrast, this study records highly variable and poorly developed particle-texture trends downslope along short (<5 km) channels that extend directly from a high-relief carbonate source area down to the shore of Lake Annecy in the western Alps, SE France. The observed inconsistent patterns are measured in both a region-wide analysis using all collected samples and also in a more specific survey of samples in six different channels incised on the steep, topographically irregular mountain flanks that border the lake. The major factor responsible for the irregular downslope patterns of roundness, sphericity, and size in the Annecy study area is the lateral introduction of sediment into the fluvial channels along dispersal paths. Episodic failure of mechanically unstable sediments and their transport down steep valley walls bring less-abraded sediment of variable shape and size along the dispersal paths. The valley wall sediment influx factor warrants further examination to better interpret sedimentation processes in dissected, high-gradient terrains that border coastal areas. [ABSTRACT FROM AUTHOR]

Sorting of sediment on a beach occurs when the cross-shore profile consists of graded sediments. Each grain-size fraction within a mixture responds differently to the same hydrodynamic regime. Sorting of sediment under wave action takes several forms. Stratified layers of finer and coarser sediment are formed, depending on wave climate, grain size, and beach slope. Grain size and sorting studies are of great importance in characterizing the dynamic beach environment. Some field data have been reported in the literature. In the present study, the cross-shore distribution of sediments, as well as the corresponding beach profiles, were measured in a wave basin on 1:5 beach slope for regular waves. Eighteen sets of experiments were performed on cross-shore sorting mechanisms using two different sand beds. The sorting of bed material and the formation of armor coats along beach profiles were defined by grain-size distribution and dimensionless parameters in this study. The experiments showed that finer material was deposited on the crest of bar-type beach profiles, but coarser grains accumulated on the foreshore, trough, ridge, and toe sections. Finer materials settled on the foreshore and crest of step-type profiles while coarser grains were deposited on the ridge and toe sections. The effect of the movement of a particular fraction on the sediment transport rate was also studied. Calculated sediment transport, modified to include the effects of sorting, was compared with transport rates measured in the wave basin. This suggested that the results under the experimental conditions were satisfactory for the description of sediment transport in the surf zone using the partial sediment transport mechanism over the beach profiles. [ABSTRACT FROM AUTHOR]

Measurements of longshore sediment transport rate were conducted on a reflective to intermediate sandy beach during energetic sea breeze activity. The suspended load transport was obtained with optical backscatter sensors, current meters, and streamer traps, whereas the total load rate was measured with fluorescent sand tracer. The streamer trap measurements revealed an exponential vertical distribution of the suspended sediment flux, with the degree of vertical mixing decreasing in the onshore direction. A continuous time series of longshore suspended sediment flux across the surf zone was obtained by combining streamer trap measurements with data collected with surf zone instruments. Comparison of the suspended longshore flux with the total longshore flux derived from the dispersal of fluorescent tracer indicated that the relative contribution of suspended load to total load was ca. 35%. The movement of sand tracer further demonstrated that nearshore sediments were transported obliquely across the surf zone, challenging our conventional view of dividing nearshore sediment transport into cross-shore and longshore components. Sand tracer was found to move onshore as well as offshore, indicating a bi-directional sediment exchange between outer surf zone and swash zone. Equations from previous studies predicted the suspended longshore transport rate rather well, but underestimated the total longshore transport rate by a factor of two. The Kamphuis formula underestimated both suspended and total longshore transport rates. [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]