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Liang, Z.; Ji, D.; Zhang, X.; Lingyun, W.; Zhang, T.; Li, S.; Yong, J.; Luo, J.; Liu, Y., and Zeng, J., 2023. Carboniferous oceanic basin sediment-gravity flows in the margin of the Junggar Basin, NW China: Characterisation and implications for hydrocarbon potential and evolution pacing. Journal of Coastal Research, 39(5), 890–906. Charlotte (North Carolina), ISSN 0749-0208. Several Carboniferous deep-marine-sandstone reservoirs have recently been discovered in the Junggar Basin, NW China. These reservoir sandstones were deposited by sediment-gravity flows that occurred on the continental slope of the Junggar Basin, and they have high hydrocarbon exploration potential. In this study, careful observations and petrological and geochemical analyses of samples from outcrop sections of Carboniferous rocks from the Junggar Basin were conducted to establish the deep-marine sedimentary characteristics, depositional environments, and mechanism of these gravity-flow deposits, as well as a sedimentary model for their occurrence. The deep-marine, gravity-flow deposit types include those of turbidity currents, debris flows, and slumps. The debris-flow deposits can be divided into pebbly debris-flow deposits and sandy debris-flow deposits. Results allow the relationship between the type and nature of gravity flows and ocean basin evolution to be established. During the early Carboniferous, the ocean basin had sufficient space to accommodate incoming sediment, and the sediment transport distance was long. The gravity-flow sediments of this period are dominated by sandy debris-flow deposits and turbidity-flow deposits characterised by thin individual layers but thick accumulations of multiple deposits. With continuous narrowing of the oceanic basin during the late Carboniferous, the basin had a smaller accommodation space. The main types of gravity-flow deposition during this period were pebbly and sandy debris flows, with rare thin turbidity-flow deposits. These deposits were coarser grained than their early Carboniferous equivalents, and their cumulative thicknesses were smaller. The results of the study provide insights into the prediction of deep-marine reservoir sandstones and the distribution of hydrocarbons in the Junggar Basin. [ABSTRACT FROM AUTHOR]

ABSTRACT Xu, B.B.; Gong, Z.; Zhang, Q.; Zhang, C.K., and Zhao, K., 2018. Non-equilibrium suspended sediment transport on the intertidal tidal flats of Jiangsu coast, China. 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. 251–255. Coconut Creek (Florida), ISSN 0749-0208. Accurate modelling of instantaneous sediment transport processes in coastal environments has been a great challenge for many decades. One of the difficulties comes from the existence of time lag between flow and sediment transport, termed as “the non-equilibrium transport effect”. To better understand and simulate the sediment transport processes, field observations were conducted on the middle intertidal flats of Jiangsu coast. Water depths, current velocity profiles, wave parameters, stratified suspended sediment concentrations (SSC), as well as grain sizes of both suspended sediment and bed sediment were measured. Results show that suspended sediment has an average grain size of 11.2 μm, the percentage of cohesive suspended sediment can be up to 97%. The bed load has an average grain size of 40 μm, the percentage of cohesive sediment is only 76%. The measured maximum SSC occurs at the beginning and the end of each tidal cycle. It is well-mixed during flood and ebb peak, but stratified during slack period. The vertical equilibrium SSC profiles were calculated based on the advection-diffusion theory. Calculated equilibrium SSC is well-mixed during whole tidal cycle and is controlled by the local hydrodynamics. The difference between calculated equilibrium SSC and real ones indicates that the contribution of advection is dominant. Thus the non-equilibrium suspended sediment transport processes should be taken into account for intertidal flat evolution. [ABSTRACT FROM AUTHOR]

ABSTRACT Tao, J.; Xu, F.; Yao, P.; Zhou, Z., and Zhang, C., 2018. The variations of sediment transport patterns in the radial sand ridges along the Jiangsu coast, China over the last 30 years. 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. 216–220. Coconut Creek (Florida), ISSN 0749-0208. The research objective is to clarify the primary factors lead to the variations of the suspended sediment transport in the radial sand ridges (RSRs) along the Jiangsu Coast over the last 30 years. The suspended sediment concentration (SSC) fields measured in several field surveys from 1980 to 2010 were analyzed. The field data indicate that the SSCs in 1980 are higher than those 2010. A two-dimensional numerical model was developed to simulate the inter-annual variations of the suspended sediment transport. Generally, the magnitude of the SSC is highly relevant with the current speed, which peaks around the Old Yellow River Delta (OYRD) and in the central RSRs. However, the northern part of the RSRs indicates higher SSC than the southern part, which is attributed to their different bed sediment composition. The net suspended sediment flux was calculated. In the north of the RSRs, the sediments are transported in the south direction, which implies a sediment input from the OYRD to the RSRs. In the south of the RSRs, a net sediment loss was observed, which is consistent with the decreasing of the sediment flux from the Yangtze River. The simulated suspended sediment transport in 1980 and 2010 mutually show similar spatial patterns, while SSCs in 1980 are overall larger than those in 2010. It is concluded that the decrease of the SSCs from 1980 to 2010 is attributed to the reduction of the OYRD and the large-scale reclamation along the Jiangsu coast, while the sediment fluxes from the Yangtze River is less important. [ABSTRACT FROM AUTHOR]

Li, L.; Wu, H.; Liu, J. T., and Zhu, J., 2015. Sediment transport induced by the advection of a moving salt wedge in the Changjiang Estuary. This study focused on the intratidal variations of suspended sediment concentration (SSC) and residual sediment transport near a moving salt wedge in the Changjiang Estuary. The stratification was controlled by the advection of the salt wedge and was strengthened during the flood tide and weakened during the ebb tide. This phenomenon is the opposite of systems that are dominated by tidal straining of salinity, which diminishes the stratification during the flood tide and enhances it during the ebb tide. The enhanced stratification during the flood tide restricts turbulent mixing; hence, the resuspended sediment is concentrated below the pycnocline. Because of the stronger turbulent mixing during the ebb tide, the suspended sediment can be elevated to the surface, decreasing the near-bottom SSC. Such tidal asymmetries of mixing and near-bottom SSC cause the net sediment flux to be directed landward in the lower layers after a tidal cycle. [ABSTRACT FROM AUTHOR]

This paper focuses on the process-based morphodynamic modeling of a mudflat dominated by a long-shore tidal current. The model is schematized as a shore-parallel tidal basin with dimensions similar to the tidal flats near the Wanggang Mouth at the central Jiangsu coast, China. A long-shore tidal current and associated sediment transport are dominant in comparison with their cross-shore components. The mudflat evolution is reproduced for both the case with abundant sediment supply and that with insufficient sediment supply. The simulated flow patterns agree qualitatively with field observations from literature, i.e., involving tidal asymmetry, current directions, and tidal wave features. The analysis of sediment fluxes depicts that deposition occurs from spring tide to neap tide and erosion from neap tide to spring tide. The results show that siltation on intertidal flats is favored by flood dominance, as well as settling and scour lag effects, with less dependence on sediment supply. However, subtidal flats are strongly affected by sediment supply. The simulated double-convex cross-shore profile associated with an abundant sediment supply is qualitatively consistent with field observations. An insufficient sediment supply causes erosion and consequent widening of the subtidal flats. Finally, the practical case with an initial sand seabed is reproduced. The long-shore sediment transport contributes to long-shore variations of cross-shore profiles. Deposition rates increase clearly southward in the area between the lower intertidal and middle subtidal flats when sediment supply is abundant. In contrast, deposition rates increase southward only slightly when sediment supply is insufficient. In addition, stronger sediment supply generates wider intertidal flats. Most importantly, the creek patterns, i.e., the incised creeks on mudflats, are roughly reproduced. [ABSTRACT FROM AUTHOR]

(1) Simulations of wave action and erosion, using a wave-producing device and a recirculating flume, were established on the Haigang mudflat, in the Yellow River estuary, China, along with the geotechnical-parameter tests of the water content, bulk density, undrained shear strength, penetration strength, and grain-size distribution. Moreover, the variety of seabed morphological characteristics under different wave actions was also observed in field. The experimental results showed that the erodibility of the silty sediment was significantly affected by the cyclic wave loading in Yellow River estuary. The erodibility varied with the changing wave loading and was closely related to the liquefaction and topography characteristics of the surficial sediment, which restricted the physical and mechanical properties of the sediment. Additionally, the wave loading transformed the sediment components and the size grading, which also had a remarkable effect on the erodibility. Increasing the length of the time vibration during wave loading clearly reduced erosion resistivity, although fluctuations appeared in the overall downward trend, consistent with the strength indexes of the silty sediment. The other geotechnical parameters, size grading, and sediment components show the wave’s dynamic variation with the changing conditions, but no clear internal relationship could be found between the varying physical parameters and the variation in erosion during the changing conditions of the wave during the experiments. [ABSTRACT FROM AUTHOR]

Embayed beaches bounded by headlands, headland bay beaches, are a common feature along the coast of southern China. The patterns of sediment transport pathways in these beaches are important for understanding changes in beach and nearshore geomorphology that are a response to different wave energy conditions. Nanwan Beach in southern China is characterized by a large seasonal variation of incident waves. In this study, sediment samples and a series of beach profiles from Nanwan Beach are examined to determine spatial changes in sediment transport pathways. Empirical orthogonal function analysis of the profile data indicates that the variation of sediment transport occurs in two distinct modes. The first mode is related to seasonal changes in cross-shore sediment transport with associated alongshore sediment transport. The trend of sediment transport is seaward in winter and landward in summer. The second mode is onshore-offshore sediment exchange, which occurs in the intertidal zone in summer and in the swash zone in winter. Moreover, grain size trend analysis of sediment samples suggests that sediment transport in the nearshore zone is predominantly in the northwesterly direction because of southeast incidence waves in winter, with Nanwan Bay opening to the south. The sediment transport pathways are to the north in summer from the influence of typhoons. [ABSTRACT FROM AUTHOR]

Study of suspended sediment transport in an estuary affected by tidal bore is important for coastal engineering and management because the tidal bore can cause strong sediment resuspension and scour in shallow waters. Numerical modeling of suspended sediment transport in a natural estuary affected by tidal bore is such a challenging research topic that there are few articles on the subject available in the literature. In this study, a two-dimensional, numerical model was developed to investigate suspended sediment transport induced by a tidal bore. The hydrodynamic component of the model employs the Godunov-type scheme with second-order accuracy in space, which effectively describes the rapid supercritical flow and sharp horizontal pressure gradients of the tidal bore. To preserve balance between the source terms and the internal forces, both the water level-bottom topography formulation (WLTF) method and a special technique for triangular mesh have been applied to solve the source term in the model equations to account for the irregular bottom topography. The wet/dry boundary issue was solved by using the improved exact-Riemann solver on the dry bed. The coupled sediment transport model incorporates more reliable equations from recent publications to characterize the rapid increase of sediment resuspension in the water column. The model test against an analytical solution of convection transport shows that the sharp gradient of scalar transport is satisfactorily estimated in the model simulations. The model in the application has been validated to simulate hydrodynamics and suspended sediment transport affected by a tidal bore in the Qiantang River of China. The results compare well with a time series of observations to characterize the rapid increases of surface elevation, currents, and suspended sediment concentration resulting from the tidal bore. Results of spatial distributions of water levels and currents indicate that the model adequately describes the sharp horizontal gradients of the surface elevation and the tidal currents during the passage of the tidal bore and characterizes the suspended concentrations in the estuary. [ABSTRACT FROM AUTHOR]

Using mooring hydrodynamic observation, cross-shore profiles, and topographic-map and satellite-image comparisons, this study shows dramatic coastal erosion on the Qinhuangdao coast (northeast Bohai Sea, China) between 1986 and 2000, with an average retreat rate of 3.7 m/y. While the retreat rate during 1996-2003 decreased to 1.5 m/y, serious coastal erosion was found around river mouths, such as the Tang, Dai, Yang, Dapu, and Renzaohe Rivers, as well as Qilihai Lagoon, with the maximum of >7.0 m/y. Sediment starvation induced by dams mainly caused this fast coastal retreat. Sediment flux of the Luan River, the dominant fluvial sediment source in the study area, declined to only 9.0% of the levels before the impoundment of two large dams in 1979. Sharply reduced sediment supply disrupted the stability of sediment transport as well as the beaches' self-recovery processes after storm surges. Coastal erosion was further intensified by coastal engineering and tourism activities. [ABSTRACT FROM AUTHOR]

The Xisan Tidal Furrow appeared as early as 1976. The major dynamic factor in the formation of the Xisan Tidal Furrow is the increase in the flood-tidal level near Xisan Gate and the extension of beach face accretion in An'dong, both of which originated from large-scale human activities. The inlet position of the Xisan Tidal Furrow has experienced four stages, i.e., swinging, stabilizing, moving eastward, and stabilizing, while the series furrow at the outside beach face is the main cause of the change in the scouring and silting of the Xisan Tidal Furrow. This article explains the causes of the Xisan Tidal Furrow's formation and its evolution, and proposes the guideline of "regulating the furrow and reclaiming the tidal flats by making the best use of local topography." On one hand, the river channel direction must comply with the regular pattern of the stream current and of sediment movements. On the other hand, furrow regulation and reclamation of tidal flats along the riverbank should be combined. We suggest that fill stone should be used and a rock dam built to completely cut the Xisan Tidal Furrow; this should occur when the Qiantang River basin has a wet year. [ABSTRACT FROM AUTHOR]

The three-dimensional circulation, salinity distribution, and overall transport pattern were simulated in the Pearl River Estuary, China, using a modified version of the Princeton Ocean Model (POM). The circulation in the estuary is mainly driven by tide, wind, and river runoff in a complex manner, where the relative importance of the different forcing factors varies over the year. Field data on currents from several locations in the estuary taken at different elevations through the water column were employed to validate the model together with measurements of the salinity distribution in the surface layer. Also, satellite images were utilized to qualitatively confirm the simulated overall transport pattern. Comparisons between measurements and calculations showed that the POM yielded satisfactory predictions without any particular calibration. However, for some events the coastal current outside the estuary induced by the large-scale circulation in the South China Sea affected the flow in the estuary, making it necessary to employ a more sophisticated boundary condition on the ocean side than what was initially implemented. The long-term objective of the numerical modeling of the flow and material transport in the Pearl River Estuary is to utilize the validated model for forecasting the circulation and water quality in the estuary in a comprehensive system where in-situ measurements and remote sensing are the other main components. [ABSTRACT FROM AUTHOR]

Ji, X.-M.; Yang, Y.; Fang, Y.-J., and Zhang, W., 2020. Tidal-fluvial processes at the outlets of delta distributaries: A multi-cruise observational study. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1449-1453. Coconut Creek (Florida), ISSN 0749-0208. The hydrodynamics in delta distributaries has tremendous impact on sediment transport, water quality and deltaic ecosystems; yet many processes acting at the riverine-esturarine interface of a delta are not well understood. This contribution investigates the interplay between riverine runoff and tidal motions at the outlets of delta distributaries. We focus on the tidal-fluvial processes at eight outlets of three main distributaries of the Pearl River Delta, China. The field measurements of water levels, discharges, velocities at the eight outlets were conducted synchronously for five times, with three times in wet season during spring, moderate and neap tides, respectively, and once in normal season, once in dry season. The observations reveal that the tidal asymmetry in the Pearl River Estuary is largely influenced by river discharge. The tidal velocity amplitudes depend mainly on the river discharge and tidal prism. To be specific, while during low discharge conditions the presence of a river discharge decreases tidal velocity amplitudes, during very high flow regimes the effect of tides at the distributary outlets is magnified with a noteworthy increase in tidal velocity amplitudes. [ABSTRACT FROM AUTHOR]

Zheng, J.-H., Jeng, D.-S. and Mase, H., 2007. Sandy beach profile response to sloping seawalls: an experimental study. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 334 – 337. Gold Coast, Australia, ISSN 0749.0208. Seawalls are commonly used as a tool for coastal defence worldwide. Most previous studies have considered the case of vertical seawalls and descriptions of existing seawalls, rather than the influence of different designs of sloping seawalls on beach erosion. In this study, laboratory investigations of an undistorted moveable bed model were conducted to determine the resulting beach profile of artificial sandy beaches. In the experiments, three different sloping seawalls were considered under erosive wave conditions with a 50-year return period. The coast of Northern Jiangsu Province, China, is used as a case study. To simulate natural conditions, similarity criteria are developed assuming that the energy dissipation per unit volume along the beach profile is uniform and that the wave properties can be properly scaled by Froude criteria. Field surveys of beach profile changes due to the storm surge induced by Typhoon 9711 were taken to validate the experimental model and good agreements were attained. Spatial profile configurations were studied by examining dominant profile features such as the break point bar and the scour trough on the seawall-backed profiles. Experimental results provided a reference for the maintenance of artificial sandy beaches and the design of seawalls on the coast of Northern Jiangsu Province, China. [ABSTRACT FROM AUTHOR]