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During extreme conditions, the transport of the wave-averaged suspended sediment concentrations in the inner surf zone affects dune erosion. Although large-scale laboratory experiments have provided insight in what drives these sediment concentrations, corresponding field data are lacking. To fill this gap, novel field observations of suspended sediment concentrations are compared to drivers that govern sediment suspension during storm conditions known from literature. A total of 128 time intervals of 20 min are analysed, spread over 10 different high water events with different hydrodynamic conditions. For each time interval, the wave-averaged (i.e. 20 min mean) suspended sediment concentration is computed and compared to three suspension drivers. The studied drivers are (1) bed shear due to near bed velocities that originate from mean currents in combination with wave-induced orbital flow, (2) the horizontal pressure gradients under steep wave fronts that increase the forces on the bed material, and (3) bore-induced turbulence that is generated at the free surface and reaches the bed. The derived bore-induced turbulence generates the greatest correlation with the mean suspended sediment concentrations (r = 0.74, p = 4.47E-23). Samples that deviate from this correlation correspond to time intervals with lower values of derived bore turbulence, less wave energy saturation in the inner surf zone, and stronger mean currents. The correlation with the mean suspended sediment concentrations increases when the shear stress originating from mean currents is used for these time intervals (r = 0.83, p = 1.63E-33). For time intervals during which more energetic conditions persist and the wave energy is saturated in the nearshore, bore turbulence was the dominant mechanism in stirring up sediment. The outcome of this study suggests that, based on the events analysed, dune erosion models may achieve more accurate results if computations of suspended sediment concentrations include a bore-induced turbulence term, or if already included, properly address the relative importance of bore-induced turbulence when compared to bed shearing. • A dune erosion field experiment was conducted to study drivers of wave-averaged suspended sediment concentrations. • The studied drivers are (1) flow-induced bed shearing, (2) horizontal pressure gradients under wave fronts, and (3) bore-induced turbulence. • The variability in bore-induced turbulence generated the greatest correlation with the variability in mean suspended sediment concentrations. • When more energetic conditions persisted and wave energy was saturated in the inner surf zone, bore turbulence appeared the dominant driver. [ABSTRACT FROM AUTHOR]

Submarine canyons serve as important sediment transport conduits from littoral zones to the deep sea, with strong impacts on the sedimentation patterns in marginal areas of the ocean. Moreover, such canyons can be major geohazards for submarine infrastructure, warranting a good understanding of their past and current behavior. Here, we present a study of the geological history and the recent activity of the Nahariya submarine canyon, the longest of a system of ∼15 small blind canyons located in the eastern Mediterranean Sea, offshore Israel. Two piston cores retrieved from the middle and outlet of the canyon, at 650 m and 915 m water depth, respectively, were the focus of a multi-proxy study aiming to characterize sediment transport and deposition along the canyon during the Last Glacial and up to the present. Both cores reveal a sequence of homogenous sediment of late last glacial age, which are capped by an unconformity overlying by fine laminated sediment dated to the last ∼200 years. Thus, the deglacial and most of the Holocene intervals are absent from the record. Evidence for down canyon sediment transport are abundant and include a 70 cm interval of mud clasts with disordered glacial ages that appears immediately below the hiatus, as well as broken calcareous shells of dead benthic foraminiferal species of shallow marine habitats, which are abundant throughout both cores. Similarly, shelf-derived living benthic foraminiferal species were found in the core-tops, indicating that active sediment transport persists along this canyon today. We conclude that the history of Nahariya submarine canyon includes a period of sediment accumulation that lasted until the last deglaciation. Thereafter, the canyon was dominated by an erosive regime that persisted throughout the Holocene. Sediment accumulation resumed ∼200 years ago. We suggest that the recent resumption of sediment-accumulation is a result of anthropogenic amplification of on-land soil erosion accompanied by a wet period that persisted in the region and enhanced land to sea sediment transport. • The geological history of a blind submarine canyon of E. Mediterranean is studied. • In-canyon last glacial sediment accumulation and Holocene erosion are observed. • Resumption of sediment accumulation occurred ca. 200 years ago. • This resumption reflects anthropogenic on-land soil erosion and shift to wet climate. • Shelf origin sediment is transported to deep canyon during glacial period and recent. [ABSTRACT FROM AUTHOR]

Estuarine deltas play a critical role in the interaction between the ocean and land and serve as the primary location for the deposition of terrestrial organic carbon and pollutants. However, many deltas are increasingly at risk of erosion due to natural processes and human activities. In particular, abandoned estuarine deltas are extremely prone to erosion in the absence of sediment replenishment. The erosion of sediment in these deltas is crucial in comprehending the evolution of delta erosion as it directly impacts coastal geomorphology, ecological environments, geochemical cycling, and carbon sequestration dynamics. Therefore, determining accurately the erosion characteristics of estuarine deltaic sediments is essential for assessing and managing these evolving coastal systems. Therefore, this study conducted erosion experiments on undisturbed sediment samples collected from the subaqueous delta of the abandoned Yellow River Estuary (Old Qingshuigou Estuary) utilizing the UMCES-Gust Erosion Microcosm System. The aim was to reveal the spatial distribution characteristics of sediment erodibility and explore the erosion process, characteristics, and influencing factors of the surface sediments in the area. Erosion characteristics exhibited a spatial distribution pattern of increased erodibility in nearshore sediment and reduced erodibility in offshore sediments. The critical erosion shear stress of surface sediments ranged from 0.2 to 0.68 N/m2, while the erosion rate increased linearly with an increase in erosion shear stress and reached a maximum value of 2.119 g/m2 s, suggesting that nearshore sediments exhibited strong erodibility. Furthermore, the erosion characteristics exhibited a strong correlation with the type of sediment. Silt exhibited surface erosion and Type I erosion (depth-limited erosion), whereas silty sand primarily underwent volume erosion and Type II erosion (steady-state erosion). Particle size characteristics played a crucial role in influencing erosion. Additionally, our results revealed that the effective particle size of sediment aggregates and the scale effect of turbulence were also important factors that affected sediment erosion characteristics. These findings not only enhance our understanding of the erosion characteristics of silty sediments but also provide valuable parameters for sediment transport models in large river deltas such as the Yellow River Delta, thus facilitating the release of buried organic carbon and heavy metals from estuaries. • The subaqueous delta of the abandoned Yellow River Estuary sediments were assessed. • UMCES-Gust Erosion Microcosm System was employed for erosion experiments. • Sediment erodibility distribution and erosion process characteristics were analyzed. • Particle size characteristics represented the most important influencing factors. • Erosion characteristics were closely related to the sediment type. [ABSTRACT FROM AUTHOR]

Coastal zones are dynamic environments where sediment transport significantly influences erosion, deposition, and ecosystem stability. Accurate modelling of the complex interactions between hydrodynamics, sediment transport, and morphological changes in high-energy shoreface areas is crucial for sustainable coastal management. This study aims to assess sediment dynamics and understand the dominant physical drivers of sediment transport in the shoreface by coupling high-resolution numerical modelling with a shoreface sand tracer experiment. Results from the field experiment showed high diffusion and a net onshore and downdrift movement of the tracer in agreement with the observed hydrodynamic data. The numerical modelling strategy, validated with in situ hydrodynamic data and tracer results, demonstrated good performance and highlighted the dominant modes of shoreface sediment transport. While during low energetic wave conditions, the dominant transport mechanism involves the slow-rate bed load sediment movement toward the shore, under moderate energetic wave conditions, longshore wave-induced suspended transport becomes the prevailing mode of transport. The study provides valuable insights to increase the understanding of sediment transport in the shoreface and highlights the importance of coupling numerical modelling with sediment tracer experiments. • Field observations and numerical modelling are used to understand sediment transport in the shoreface • Conceptual sediment dynamic model combines Lagrangian and Eulerian approaches • Energetic wave conditions increase wave-induced currents and sediment transport rates, with waves breaking over the bar crest. • Streaming and wave nonlinearities are the main drivers of sediment transport in the shoreface • Alongshore suspended transport dominates in the surf zone, distributing sediments downdrift [ABSTRACT FROM AUTHOR]