Flocculation hysteresis, temporal asymmetry, and their impacts on sediment transport in the benthic boundary layer of Sansha Bay, SE China

Simulating suspended sediment transport during the 2023–2024 floods in southern Brazil

Bedload and suspended sediment transport analysis in a Mediterranean intermittent river

Erosion and transport of sediments in watersheds of southwest Puerto Rico determined from strontium isotopes and mixing models

Ensemble machine learning and landsat observations reveal seasonal and spatial dynamics of water quality in a river-influenced estuarine system

Modern sediment sources and transport processes in the southern Arabian Sea: Evidences from geochemistry and mineralogy

The Danube River floodplain downstream of Vienna (Austria), contains anthropogenic signals, which are exposed in erosional cuts. Sedimentological, geochronological, and chemo-stratigraphic techniques were applied to reconstruct past floods and understand anthropogenic signals at regional to supra-regional scales. Key facies associations were identified, aiding depositional analysis and palaeoenvironmental reconstruction. Deposition began with channel infilling (FA1) behind a mid-channel island. By 1916, the island has docked onto the riverbank, leading to lateral point bar deposition (FA2), throughout which floods occur with increasing intensity (FA3 and FA4). Using field sedimentological techniques and 137 Cs, seven major flood events from 1954 to 2013 were identified, overall exhibiting a coarsening-upward sequence, which contrasts typical “natural” overbank fining sequences and reflects changes potentially linked to upstream hydro-power infrastructure. Geochemical signals indicate: i) singular events resulting from local human agency e.g., Sn contamination peak in 1991 due to local pollution; ii) shifts in provenance signals indicating catchment-scale changes of sediment transport and connectivity, e.g., decrease in CaO as upstream hydro-power stations act as sediment sinks; and iii) supra-national signatures connected to atmospheric emission trends, e.g., Zn, Cd, Pb increase since the Great Acceleration and decline during the phase-out of leaded fuels. This multi-proxy archive provides a baseline for future cross-site correlation, and for understanding the impacts of river management and restoration measures. • Event-based dating of modern floodplain deposits by using field sedimentology, radiogenic nuclides, and historical records. • Coarsening- and thickening-upward trend in recent flood deposits potentially linked to remobilisation from hydropower dams. • Both local and global trends in environmental pollution over more than 100 years can be pinpointed. • Element composition and sedimentary structures reflect the impact of human activities on sediment composition and balance.

Seagrass meadows have been proposed as a nature-based coastal protection measure to reduce incoming wave energy. Although numerous studies have demonstrated the capability of seagrass meadows to attenuate waves, their real-world effectiveness in providing coastal protection remains uncertain. The aim of this study was to quantify the influence of a Zostera marina meadow located in a non-tidal fetch-limited environment on three coastal protection metrics: wave runup at the shore, the storm-induced erosion of dunes, and the longshore sediment transport. Field observations were combined with numerical wave simulations using the open-source model SWAN. The field study encompassed one year of wave observations along a transect from 1.5 to 8.0 m depth, using a wave buoy and six pressure sensors. Seagrass characteristics were mapped on four occasions to capture seasonal variability. The effect on wave attenuation of the seagrass meadow was isolated from other dissipation processes by comparing model scenarios with and without vegetation. Results showed that maximum wave attenuation occurred under high-energy conditions, with a maximum wave height attenuation of 12%. However, as depth-induced breaking became the dominant dissipation process, the contribution of the seagrass meadow diminished, leading only to modest reductions in wave runup (1.0%), storm erosion volume (4.0%), and longshore sediment transport (0.6%). These findings indicate that seagrass meadows situated in relatively deep, fetch-limited environments offer limited potential for wave energy dissipation and coastal protection.

Reliable prediction of suspended sediment concentration is essential for reservoir operation, sustainable water management, and river ecosystem restoration. However, accurate forecasting remains challenging due to the strong nonlinearity and nonstationarity of sediment transport processes, as well as the complex interactions between hydrological variability and sediment supply dynamics.This study develops an integrated forecasting framework that combines signal decomposition, feature selection, deep learning, and optimization. In the proposed framework, variational mode decomposition is used to decompose suspended sediment concentration time series into multiple subcomponents, enabling the separation of temporal patterns at different scales. An improved sparrow search algorithm calibrates the decomposition parameters and improves component stability. Multigene genetic programming is then applied to select informative subcomponents and reduce redundancy. A hybrid convolution-transformer network is constructed to model both local fluctuation patterns and longer-range dependencies within the selected components. Finally, the improved sparrow search algorithm(ISSA) optimizes the weighting of individual model outputs to form an integrated adaptive predictor. The framework is evaluated using daily streamflow(Q) and suspended sediment concentration observations from 1977 to 1986 at the Tangnaihai Hydrological Station in the upper Yellow River Basin. The results show high predictive accuracy, achieving a Nash-Sutcliffe efficiency of 0.9535 on an independent test period with consistently low error metrics. Overall, the proposed framework provides a robust and generalizable approach for suspended sediment concentration forecasting under complex environmental conditions.

ABSTRACT Mangla Lake, a vital freshwater reservoir in Azad Jammu and Kashmir, Pakistan, sustains nearly half a million people. This study presents a novel, integrated assessment of heavy metal (HM) contamination in its sediments, combining high-resolution geospatial sampling with multivariate chemometric analysis to elucidate pollution sources, spatial patterns, and ecological risks. Sediment samples (n = 123 from 41 sites) were analyzed via ICP-MS for 10 HMs (Cr, Mn, Fe, Ni, Cu, As, Cd, Sb, Hg, Pb). Advanced statistical techniques – including cluster analysis, factor analysis, principal component analysis, and generalized network dimensionality reduction (GNDA) were employed alongside pollution indices (Igeo, EF, Hakanson’s RI) to identify and apportion contamination sources. Results indicate that Fe, Mn, Cr, Ni, Pb, and As are the predominant contaminants, forming distinct spatial clusters linked to anthropogenic inputs (agricultural runoff, urban/industrial discharges) and natural weathering. GNDA outperformed traditional methods, explaining 86% variance and effectively discriminating between geogenic and anthropogenic sources. While ecological risk indices suggest low-to-moderate basin-wide risk, localized hotspots near inflows exhibit elevated concentrations, necessitating targeted management. The study advances regional sediment pollution assessments by coupling statistical source apportionment with sedimentological and hydrodynamic context, highlighting the roles of fine sediment transport, seasonal hydrology, and land use in contamination dynamics. Comparative analysis with regional and global reservoirs reveals Mangla’s unique contamination profile, driven by Himalayan lithology and moderate urbanization. Findings underscore the value of integrated, process-informed monitoring and provide a scalable framework for reservoir sediment management in data-scarce regions. The results are significant for national governmental agencies (including healthcare) and planning authorities in the region and highlight the value of multidisciplinary analysis.

ABSTRACT Monopile foundations significantly disturb local hydrodynamics and are prone to severe local scour under steady currents. This study proposes a novel active scour protection concept, termed the spoiler pipe, installed upstream of the monopile to modify the approaching flow field. A three-dimensional CFD model coupled with sediment transport is developed and validated against classical laboratory experiments. The results show that the spoiler pipe attenuates the incoming flow, weakens erosive vortex structures around the pile, and induces wake-related sediment deposition, leading to effective scour mitigation. Parametric simulations indicate that the maximum scour depth can be reduced by up to 49%, depending on the spoiler pipe diameter and its upstream stand-off distance. The stand-off distance primarily controls the maximum scour depth, while the pipe diameter governs sediment replenishment and scour pit extent. The spoiler pipe provides a simple, low-disturbance active scour protection solution, particularly suited to current-dominated or mixed-flow offshore environments.

Understanding the coupled interactions among water resources, sediment processes, ecological restoration, and socio-economic development is critical for sustainable river basin management under changing environments, particularly in arid and semi-arid regions. The Ningxia reach of the Yellow River Basin represents a strongly human-impacted system in arid/semi-arid area, where water scarcity, intensive regulation, and ecological vulnerability coexist. In this study, we develop an integrated water-sediment-ecology-socioeconomic (WSES) nexus framework based on System Dynamics to investigate long-term co-evolutionary processes and policy trade-offs in this region. The model is calibrated using long-term observational and statistical data from 2010 to 2021, and future simulations are conducted for the period 2022-2050 under combined scenarios.The model explicitly couples hydrological dynamics, sediment transport, ecological restoration measures, and socio-economic development, and is calibrated using long-term observational and statistical data. By combining afforestation and grassland restoration scenarios with SSPs-RCPs climate-socioeconomic pathways, we simulate system responses from 2010 to 2050. Results reveal pronounced nonlinear relationships and trade-offs between ecological benefits and water availability, identify threshold behaviors in water-sediment regulation, and demonstrate that high-emission pathways substantially amplify hydrological and environmental risks. Moderate ecological restoration (9% forest-grassland growth rate) under low-emission development pathways reduces sediment load by approximately 73% compared to the 3% restoration scenario, while maintaining a stable runoff range and supporting sustained economic growth, emerging as a more robust and adaptive strategy for balancing water security, sediment control, and economic growth.

Flash floods play a key role in soil erosion and land degradation on hillslopes and lands with low or no vegetation cover, particularly in arid and semi-arid climates. These conditions prevail in most regions of Kerman province, southeastern Iran, where intense, short-duration rainfall generates rapid runoff and substantial sediment transport. Hence, to understand the process of erosion induced by flash floods, this study explored the combined influence of slope gradient (0-0.175) and flood discharge (3, 4.5, and 6L/s) on scour and sediment yield using controlled flume experiments. A 300cm glass flume with non-uniform sand (1-4mm particles) was used to test 18 configurations under three repetition test schemes. Using dimensional analysis, scour depths were measured at 50mm intervals. The results showed that both scour volume and sediment yield increased significantly with increasing slope and discharge. For example, at a discharge of 6L/s, the maximum scour volume was observed at a slope of 0.175. When the slope was reduced to 0.15, the scour volume decreased by approximately 30-50%. At the same discharge, for slopes below 0.1, the reduction exceeded 93%. Increasing discharge from 3 to 6L/s at a 15% slope increased scoured sediment by 36.3%. Moreover, with a 12.5% increase in bed slope, the amount of eroded sediment increased by a factor of 18.5. The results showed that mild slopes (0-0.05) with moderate flows improved bed stability, whereas steeper slopes under high discharges intensified upstream erosion and shifted deposition downstream.

River capture occurs when a river is diverted into a neighboring drainage basin, changing the routing of water and sediment and altering the dispersal pathways of aquatic organisms. Captures are commonly used to explain drainage patterns and biogeographic distributions, yet the mechanisms that govern river capture are not well understood, especially for alluvial rivers. Field observations suggest that an alluvial river capture begins when a river’s flow is partially diverted into an adjacent basin, forming a bifurcation. We adapted a morphodynamical model of river bifurcation to study the evolution of an ongoing alluvial river capture and test how the relative slopes and discharges of the two branches determine whether the capture succeeds or fails. The results indicate that the branch with the smaller initial ratio of sediment supply to sediment transport capacity ultimately claims most of the discharge. This competition proceeds more rapidly if the branches differ more in their supply-to-capacity ratios. Applied to the ongoing capture of the upper Orinoco River by the Casiquiare River, a tributary of the Amazon River, the model predicts that the capture will succeed over thousands of years.

Relevance. This article examines the characteristics of suspended sediment transport in a section of the Upper Lena River near Lensk City. As this area has no suspended sediment measurements, data must be reconstructed using analogue stations. Methods. A comparative analysis of water and sediment discharge has been carried out, considering geomorphological, climatic, and anthropogenic factors. Relationships between sediment and water discharge, as well as flow velocities, have been identified. Intra-annual changes in suspended sediment concentration, grain size, and flow structure have been assessed. Results. It was found that placer mining in the Vitim, Olyokma, and Chara river basins significantly affects sediment concentration and grain size distribution. This influence increases sediment load, the proportion of finer sediments, and the spatial variation within the flow. The analysis showed that data from the Rosgidromet network has limited use because of measurement errors, infrequent sampling, the underestimation of colloidal and clay particles, and local anthropogenic impacts. The results obtained provide a basis for reasonably extending sediment transport characteristics to the calculated cross-section near Lensk City and for estimating initial data for the design of water intake and other hydraulic structures.

We address the impact of systematic changes in the wave directions to the magnitude and direction of wave-induced sediment transport along the southern and eastern sedimentary Baltic Sea shores. The analysis was performed using the CERC approach in terms of potential alongshore sediment transport based on SWAN-reconstructed wave time series forced by ERA5 winds for 1990–2021. The majority of transport is driven by waves approaching from one or two narrow (±15°) ranges of prevailing wave directions. These wave systems produce mostly >60% and in many locations up to 80–90% of the total transport. While either clockwise (CW) or counterclockwise (CCW) transport predominates in a part of the study area, many locations experience a delicate balance of transport under the impact of waves from the south-west and north-west and adjacent directions that generate CW and CCW transport. We show that the prevailing wave directions that drive most of the transport have not changed 1990–2021. Instead, the balance of waves from these directions has changed because of a systematic decrease in the frequency of waves from the north-west and adjacent directions. The overall intensity of transport driven by waves from these directions has considerably decreased in about 1/3 of the study area. The decrease rate of CW transport is up to 16,000 m 3 /yr. Such alterations infringe the balance or even direction of sediment transport in sectors affected by bi-directional wave patterns but usually only affect the magnitude of sediment transport in coastal sectors that develop under the impact of a single-peak wave system. • Prevailing wave directions driving most of sediment transport are identified. • Waves from SW and NW keep fragile balance of transport on the Baltic proper shores. • Significant changes have occurred in sediment transport across the study area. • The reason is a decrease in the frequency of waves from the north-west. • Changes in wave fields have varying impact across the study area.

The backwater effect of large hydraulic structures (dams or gates) alters upstream hydrodynamics and sediment transport. However, the turbulent characteristics and sediment transport mechanisms under backwater remain unclear. This study investigates how dam-induced backwater affects open-channel turbulence and suspended sediment transport. Laboratory experiments are conducted to analyze flow velocity distribution, turbulence intensity, and suspended sediment concentration (SSC) under varying backwater conditions for clear and sediment-laden flows. Horizontally, an increased backwater indicator (BI, β) reduces streamwise velocity, and substituting section-averaged velocity for friction velocity yields a logarithmic profile (R2=0.977–0.994). Vertically, backwater induces “vertical-plane” secondary flows and an adverse pressure gradient at relative water depth (y/h) larger than 0.2, producing a velocity peak at y/h≈0.4; these vertical flow components are more sensitive to discharge (25%) than to bed-slope changes (33.4%). In sediment-laden flows, near-bed velocities (y/h<0.2) decrease and sensitivity to BI weakens, indicating two-phase feedback. These results fill gaps in understanding backwater flow dynamics and provide a foundation for refining models and optimizing hydraulic-structure design and operation.

Accurate prediction of long-term morphodynamic evolution in mixed-energy coastal systems requires models that resolve key hydrodynamic processes and reproduce the correct sequence and magnitude of forcing events. However, determining what constitutes the ‘correct’ events remains challenging because the governing processes operate across a wide range of temporal scales. In this study, we develop a hydro-morphodynamic modelling framework based on the TELEMAC suite to simulate multi-decadal morphological changes along the Belgian Part of the North Sea (BPNS). After validation against hydrodynamic and suspended particulate matter observations, a 10-year benchmark run is used to establish a target morphology against which 43 tests to optimise boundary conditions for morphological acceleration using the MORFAC approach are evaluated. The optimisation results show that predictive morphodynamic skill is linked to the co-occurrence of energetic wave events with the spring-neap tidal cycle. We subsequently introduce a new metric, the -factor, which quantifies the wave-tide interaction and can be used for MORFAC-based optimisation. Optimal performance is achieved when synthetic wave series preserve the natural alignment of high-energy waves with spring tides, consistent with the benchmark run. In addition to the wave-tide timing ( -factor), the optimization test shows that the predictive skill also depends strongly on the combined choice of value and wave schematization. When applied to hindcast the 1984-2022 BPNS evolution, the optimized model reproduces the large-scale development of the deeper sandbanks but fails to capture the coastward migration of a shallower bank. This mismatch is attributed to missing wave-induced cross-shore sediment transport processes and is subsequently resolved by including effects of wave nonlinearity and Stokes-drift on sediment transport in the model equations. A final sensitivity analysis demonstrates a significant risk of model equifinality: an inaccurate representation of wave conditions and their temporal alignment with tidal cycles can still appear to produce correct morphological behaviour when compensated by parameter tuning, thereby hiding the shortcomings in the physical forcing. This underscores the need for physically informed and deliberate modelling choices when predicting long-term morphological changes. • Development of a mixed sediment morphodynamic model suited for long-term predictions • Optimization of hydrodynamic forcing for MORFAC approach using forcing occurrence and magnitude • Introduced a wave-tide co-occurrence metric to strengthen long-term predictions • Identified dominant processes driving long-term nearshore sandbank movement

Integrating DEM and flow stress factors to identify sedimentation-transportation zone in the eastern Himalayan foothill region.

Wakes generated by deep-draft vessels are known to cause various environmental concerns, including erosion, increased sediment suspension, sedimentation, and ecological disturbances. This study employed field measurements in the Upper Galveston Bay, Texas (GBT) to record water-level fluctuations, 3D water velocities, and suspended sediment concentrations (SSCs) at a fixed location during wakes caused by deep-draft vessels transiting the Houston Ship Channel (HSC). The typical depths of the GBT and the HSC are 3 and 15 m, respectively, with over 20,000 deep-draft vessel movements per year. Using two SSC measurements at different elevations above the bed, a simple composite model was developed to estimate the vertical distribution of SSC during different phases of vessel wake influence. Correlations of vessel and wake parameters to SSC and sediment transport revealed that maximum secondary wave height and the combined drawdown-secondary height were the best predictors of SSC and total gross sediment flux out of all tested parameters. In contrast, the drawdown height was more effective at predicting total net sediment flux, as the unidirectional flow of the drawdown was the dominant contributor to overall sediment movement. The dominant transport direction was opposite the wake propagation direction, toward the HSC, with a high-level estimate of total sediment transported to the HSC of 8.05 × 108 kg/year, which is approximately 39% of typical shoaling rates for the area.