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The upper third member of Eocene Dongying Formation (Ed 3 u) is considered to be one of the most important hydrocarbon-rich intervals in Nanpu Sag, Bohai Bay Basin, China. Through integrated analysis of the drilling cores, wire-line logs, and high-quality three-dimensional (3-D) seismic data, the sedimentary characteristics of Ed 3 u were analyzed by utilizing the seismic geomorphology approach in the double slope systems of Laoyemiao transverse anticline, Nanpu Sag. The Ed 3 u, a third-order sequence, can be subdivided into three fourth-order sequences (from base to top as SS1, SS2, and SS3). The fan delta front and sublacustrine fan have been identified from well-based analysis of the sedimentary facies and core examinations reveal that the sublacustrine fan deposits were dominated by six types of resedimented lithofacies, namely, slides, slumps, sandy debris flows, muddy debris flows, turbidity currents, and hyperpycnal flows. Stratal slices were obtained from 3-D single-frequency seismic volumes to map the sediment dispersal characteristics and document the evolution of the depositional systems constrained by the double slope break zones of Laoyemiao transverse anticline. The unique structures of the double slope break zones and the variation in the lake level associated with the system tracts of the third-order sequence jointly control the dispersal patterns of the sand bodies and the spatial-temporal evolution of the depositional systems. Based on the above analysis, the depositional evolution model of Ed 3 u was established. The proposed facies-controlled model and sediment transport model can be used to accurately predict the favorable reservoir sandstones. • Analysis lithofacies and origin of sublacustrine fan. • Investigate the controls of double slope break zones over the distribution of sedimentary systems and sand bodies. • Exhibit the spatial-temporal evolution of fan delta front and sublacustrine fan in the systems tract. • Establish the depositional model from source to sink under the control of the transfer zones and slope systems. [ABSTRACT FROM AUTHOR]

• Rill morphology evolution on 4 coarse-textured topsoils is studied by laser scanning. • Rill headward and downward erosion are two mutually reinforcing processes. • Soil erosion intensity can be indirectly evaluated by geomorphologic comentropy. The sheet and rill erosion phases dominate the erosion process of the catchment area and up-slope of Benggang (a special gully) area, and its evolution has a vital impact on erosion characteristics in the erosion feedback loop. Here, the rill development processes, morphological characteristics and corresponding soil loss were investigated by laser scanning on the four coarse-textured granite topsoils defined as WH, TC, GX, and CT for the counties of Wuhua, Tongcheng, Ganxian, and Changting in China, respectively. A soil flume (3 × 0.8 m) at a slope gradient of 16.7% was treated with rainfall-inflow at the upslope inflow rate of 2 L min−1 and rainfall intensity of 90 mm h−1. Results showed that soil erosion rate increased with erosion evolution (sheet erosion, rill advance, and rill maturity phases). A comparison of the four different soils exhibited that the soil erosion rate showed a downtrend with the increase of soil clay and gravel contents. Specifically, the CT soil with high clay and gravel content showed the minimal soil erosion rate (0.024 kg m−2 min−1), rill density (0.95 m m−2), headward erosion rate (0.41 cm min−1), and surface evolution rate. The maximal soil erosion rate and rill depth were observed on the WH slope, with the rill headward erosion rate reaching the maximum of 20.59 cm min−1. Despite no significant difference in the geomorphologic comentropy of the four soils, their variation trend and rate could reflect dynamic changes in erosion. The total sediment transport efficiency was improved by rill formation and development, with rill erosion contributing to about 70% of total soil loss for the four soils. This study can enrich our understanding of the rill erosion process and surface morphology of coarse-textured topsoils. [ABSTRACT FROM AUTHOR]

• Combine geochemical and geomorphological analyses to determine desert sand supply. • For Tengger sand, main provenances are the NE Tibetan Plateau and the Alxa Block. • Wind & water as competing agents supply sand from two sources to the desert center. • Glaciations triggered variations in the desert sand supply, during ∼2.7–1.2 Ma and <0.8 Ma. Knowledge of surface processes in source-to-sink system of sand is important for the development and utilization of natural resources in desert. However, the surface processes within Chinese deserts, especially their response to long-term global cooling since the Late Pliocene, are still poorly understood. Here, we use geochemical analyses of aeolian sand (63–500 μm) samples from a drill core in the central Tengger Desert of China, together with widely-distributed surface samples, to elucidate the present and past surface processes. The main sand provenances for the southwestern and northeastern parts of the Tengger Desert are the northeastern Tibetan Plateau and the Alxa Block, respectively. After the inception of Northern Hemisphere glaciation at ∼2.7 Ma, the expansion of ice sheets in high northern latitudes was the major trigger of an increased sand supply from the Alxa Block to the desert hinterland, via the strengthening of the Siberian High. After the Mid-Pleistocene Transition (MPT), during ∼1.2–0.8 Ma, the development of mountain glaciers in the Tibetan Plateau was the major trigger of an enhanced fluvial sand supply from the northeastern Tibetan Plateau to the hinterland. Further, we propose that these two triggers may subsequently have caused substantial variations in the sand supply to most of the deserts surrounding the northern Tibetan Plateau rather than only the Tengger, due to the similarity of their sand supply mechanisms. And the enhanced fluvial sand supply from the northern Tibetan Plateau may be of significance to the continuous existence of a sand sea landscape in the surrounding basins during the post-MPT interval. Overall, our study suggests that glaciation in the high latitudes and the high mountains of the Northern Hemisphere have a significant impact on the two sand supply agents, i.e., wind and water, of Chinese deserts respectively. [ABSTRACT FROM AUTHOR]

Abstract: Submarine barchans in three new regions were described using new high-resolution multibeam bathymetric data off the Dongfang coast in Beibu Gulf. Currents, seismic profiles of horns, surface sediments and comparative surveys in 2007 and 2009 were obtained to study barchan mobility and sand transport in the barchan fields. The submarine barchans occur at depths of 15–25m, reaching up to 551.9m in horn length and 8.6m in height. Most barchans have asymmetrical horns and display wider plane shapes than subaerial barchans for the same length and height. The morphology of barchans exhibits regional variations that are mainly controlled by finite water depth, daily reverse currents, sand supply changes and interaction of dunes. Barchan asymmetries, internal bedding inclinations and grain size changes are in agreement with the dominant current directions. Results show that submarine barchans migrated 5–43m in two years (2007–2009) through comparison of bathymetric data. Because of the marginally cohesive fine sediment composition and long distance from contemporary sediment sources, it is believed that barchans in region C are not of modern origin. However, these bedforms can be also affected by high energy flow regimes. Collisions limit barchan widths and provide efficient transport paths between barchans on their horns. Large sand supply through the horns increases the barchan heights and also changes their shapes. Some small dunes are identified that are moving away from the barchans field in 2007 and have departed from the host barchans in 2009. These small barchans were probably caused by the separation of the faster-moving horn tails from the host barchans when extreme situations happen. The mechanism gives a new explanation for sand loss and size determination of submarine barchans. [Copyright &y& Elsevier]

• An efficient 2D shallow water hydro-sediment-morphodynamic model is presented. • Morphodynamic processes under the impact of cascade movable weirs are studied. • Disparate morphological changes may result under different operation schemes. • An alternating operation scheme is proposed to constrain morphological changes. Cascade movable weirs have been increasingly widely used for river landscaping, water storage and ecological wellbeing. The weirs disturb the prior equilibrium in line with fluvial hydrology, sediment transport and geomorphology, and may lead to profound changes in the river, of which, however, the understanding has so far remained poor. Here, the first of its kind, a computational modelling study is presented on the morphodynamic processes under the impact of cascade hydraulic lifting dams, a type of movable weirs, as to the middle Fen River, China. A two-dimensional shallow water hydro-sediment-morphodynamic model is applied to resolve the fluvial processes, which is physically coupled and computationally efficient based on Finite Volume Method, unstructured mesh, local time stepping and parallel computing. Computational results show that the cascade dams alter the flow and sediment transport locally and on the reach scale in a distinct manner under different operation schemes, which in turn incur disparate morphological changes. Collapse of all the dams all year round would lead to net degradation in the study reach, with the floodplains aggrading and the main channel degrading. Operation of all the dams all year round may induce an overall aggradation both on the floodplains and in the main channel. If all the dams collapse in flood seasons and operate in dry seasons (CF), degradation occurs in the main channel whereas the floodplains experience aggradation, with a net degradation. When only the dams in the main channel operate all year round (OM), the floodplains degrade while the main channel aggrades, resulting in a net aggradation in the study reach. Either aggradation or degradation may prevail locally on floodplains, in main channel and individual subreaches. The present findings lead us to propose a complex operation scheme of annually alternating CF and OM to constrain significant morphological changes. [ABSTRACT FROM AUTHOR]

Abstract: To improve navigability of the major access channel into Shanghai Harbor, a large-scale Deep Waterway Project was carried out in the North Passage (NP) of the Yangtze Estuary. In this paper, we investigate how the navigational works affected morphological changes of this channel, as well as those of the adjacent North Channel (NC), Hengsha East Shoal (HES), Jiuduansha Shoal (JDS), and the South Passage (SP). Morphological changes were assessed by analyzing digitized bathymetric data of this area prior to and after execution of the engineering works. The qualitative relations between these changes, along with the hydrodynamic changes as a result of the construction of engineering works, were subsequently investigated. The results reveal that the construction of training walls, groins and jetties resulted in decreased ebb transport in the upper reach of the NP and increased ebb transport in the upper reach of the SP. In turn, this led to intensive upstream erosion with large amounts of sediment transported seaward in the SP and associated sedimentation in the downstream area. At the same time, intense siltation occurred in the upper reach of the NP, while the main channel of the NP mainly experienced erosion caused by the construction of training walls and groins that concentrated ebb flow in the main channel. The waterway deepened significantly in previously shallow areas. Small tidal channels in the HES, which used to connect the NP and the NC, were cut off by the northern training wall. Consequently, residual flow in the middle reach of the NC flowed directly toward the northern bank of the HES, leading to local erosion. Flow obstruction by the southern training wall reduced the upstream propagation of the flood tide in the SP. As a result, a collection of small flood channels evolved under the flushing action of flood currents in the JDS, preventing the natural trend of horizontal extension of the JDS. However, the flow obstruction enhanced the vertical accretion of the JDS. [Copyright &y& Elsevier]

Abstract: This paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat, Jiangsu coast, which used to be one of the widest intertidal flats in China. Investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kgm−1 on the upper intertidal flat to 103–4 kgm−1 on the lower intertidal flat, per tidal cycle. This variation was caused mainly by the phases of the current velocity, suspended sediment concentration (SSC), local bed geomorphology, inundation patterns, and extreme weather conditions. The longshore component of tidal currents intensifies seaward over the intertidal flat. Extreme weather conditions (e.g. storms) and strong winds were important factors affecting the current velocity structures, the intensity of residual currents, and the SSCs. The SSCs were characterized by several peaks throughout the tidal cycle. These peaks were associated with strong currents, combined wave-current interactions and intense turbulences due to the initial flood surge. Furthermore, the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle, than during the ebb. Fine particles were transported within the upper water column by landward residual currents, but coarse particles were transported within the lower water column by seaward residual currents. Overall, residual currents were apt to transport fine-grained sediment landward and coarse-grained sediment seaward. This pattern indicates that the suspended sediment fluxes are highly variable in the water column, even for very shallow tidal environments. The cross-shore component accounted only for a small percentage of the total sediment flux. However, this part of sediment supply dominated accretion over the intertidal flat. The intertidal flat has become narrower and steeper, following sequential reclamations. A negative feedback process existed to maintain the convex profile shape, although the human activities (i.e. reclamation) could have modified the natural process. The surficial sediment tended to become finer on the mid-upper intertidal flat but coarser on the lower intertidal flat following reclamations, in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat. Accretion, with high rates, was maintained by landward transport of sediment. In such an accretional system with influences of reclamation, the width or slope of the intertidal flat is adjusted continuously. Before the cease of reclamation, the intertidal flat is unable to achieve an equilibrium shape. [Copyright &y& Elsevier]

Summary: The variability of effective discharge is analysed for three geomorphological zones (gullied hilly loess, valley–hill loess and eolian sand) in the Wuding River basin, China, based on mean daily flow discharge and mean daily suspended sediment discharge from 1959 to 1969, a period when human disturbance in this catchment was less intensive. A modified approach to the determination of discharge class intervals is developed, framed in terms of equal arithmetic intervals of the standard deviation S for all the discharges, such as S, 0.75S, 0.5S, and 0.25S. The average flow duration of effective discharge in the river basin ranges primarily from 0.026% to 3.16% in the two loess regions (corresponding to large flood events), and from 18.75% to 91.51% in the eolian sand region (corresponding to low or moderate flows). The average flow duration of effective discharge is significantly influenced by the size of class intervals and by characteristics of the flow and sediment regime. Using the most appropriate class interval of 0.25S, the average flow duration of effective discharge is about 0.026% in the two loess regions (other than 0.104% at Hengshan), but in the eolian sand region it reaches 24.50% at Yulin and 52.66% at Hanjiamao, respectively. Histograms of suspended sediment transport indicate that there is a bimodal dominant discharge for suspended sediment transport, with one peak in the range of low flows and the other in the range of large floods. Drainage density and specific sediment yields are lower in the eolian sand region, where effective discharge events occur more frequently and suspended sediment concentration is much lower than that carried by events of the same discharge in the loess region. In contrast, drainage density is higher in the two loess regions, where infrequent hyperconcentrated flows generate high specific sediment yields. Effective discharge differs significantly from bankfull discharge across the whole Wuding River basin. [Copyright &y& Elsevier]

Abstract: This paper presents a three-dimensional (3-D) numerical model to simulate morphological changes in alluvial channels due to bank erosion. A method for the simulation of bank erosion is established. This is incorporated into a 3-D mathematical model for turbulent flow and non-uniform, non-equilibrium sediment transport. This model is applied to simulate morphological changes in the Shishou bend of the middle Yangtze River in China, where serious bank erosions occurred during the last two decades. The double-layer sediment structure of the riverbank on the middle Yangtze River is taken into account in the bank erosion module. Both cohesive and non-cohesive bank material in the different layers are considered. The bank erosion module also includes other factors affecting the rate of bank erosion, such as the longitudinal length of failed bank, the thickness of each layer in the double-layer structure, and the erosion-resisting effect of cohesive material from the top layer of failed bank. A locally-adaptive grid system is proposed to efficiently simulate the lateral migration of alluvial channel due to bank erosion. The predictive capability of the 3-D model is examined by laboratory data. Simulated processes of bank erosion agree with field observations in the Shishou bend during the period of October 1996–October 1998, and the bank erosion module plays a significant role in simulating morphological changes of the study reach. In addition, the equivalent channel-forming discharge, which is defined as a constant discharge that can create the same amount of bank erosion in an alluvial channel as that created by natural runoff processes during the same period of time, is proposed to improve calculation efficiency for feasibility studies. [Copyright &y& Elsevier]