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Quaternary glaciations have significantly impacted the midcontinental North American landscape, leaving behind a proglacial sediment record of glacial lake deposits, glacio-fluvial sand and gravel, and windblown loess. This paper aims to expand upon a previous study using detrital zircon provenance analysis to investigate midcontinental North American loess provenance in relation to the glacial history of the southern Laurentide ice sheet during the middle to late Pleistocene. The study incorporates previously published detrital zircon data from last glacial tills (representing the Huron-Erie Lobe, Lake Michigan Lobe, Green Bay Lobe, Superior Lobe, Des Moines Lobe, and James Lobe), middle to late Pleistocene loess from several sites along the Illinois and Mississippi River valleys, and suspended sediment load inputs from the Missouri River and Arkansas River. A statistical mixing model (DzMix version 2.2) was used to estimate the relative proportions of glacial and nonglacial sources to Wisconsin Episode, Illinois Episode, and pre-Illinois Episode age loess. We show that mixing models that include the modern suspended sediment loads of the Missouri and Arkansas Rivers significantly improve (up to 23% increase in cross-correlation value) the source characterization of Wisconsin Episode (last glacial) and Illinois Episode (penultimate glacial) loess deposits within the Mississippi River drainage basin. These river sources are dominant inputs for certain loess sites (as much as 51%), but their relative contributions are not static across time and space, which has implications for temporal and spatial differences in relative sediment source estimates and glacial and fluvial sediment transport evolution. Specifically, differences in relative sediment proportion estimates among Wisconsin, Illinois, and pre-Illinois Episode loess support previous evidence for the persistence of a Quebec-Labrador ice dome source through multiple glacial cycles, even with the inclusion of river sources in updated mixing models. Illinois and pre-Illinois Episode loess in the southern portion of our study area received ~20% detrital zircon input from sources similar to the present-day Missouri and Arkansas Rivers, suggesting that these river systems were contributing a significant amount of detritus to the lower Mississippi River valley region during the middle Pleistocene. [ABSTRACT FROM AUTHOR]

Predicting suspended sediment loads in areas without detailed measurements, or with only short-term records, is crucial for the sustainable management of water resources. This study aimed to establish the relationships between specific suspended sediment loads and the characteristics of 23 sub-basins within the Haraz-Neka River basin, in Iran, to create regional models to estimate the sediment loads. To achieve this, several analytical methods were used, including cluster analysis, principal component analysis, principal component and classification analysis, and general linear modelling. Among these, the principal component analysis regression model was the most effective for estimating suspended sediment loads in the clusters. The principal component and classification analysis revealed that the best predictor was the first principal component, which strongly correlated with the minimum and mean elevation of the sub-basins. The general linear model regression showed the best overall performance for estimating regional suspended sediment loads in the study area. [ABSTRACT FROM AUTHOR]

Agriculture is a key contributor to poor water quality, but the sources of sediment and nutrient losses from agricultural catchments – including from riverbank erosion – are highly variable. Riverbank erosion is particularly difficult to quantify and control. Here, we developed a quick assessment approach to quantify riverbank erosion rates and associated sediment and nutrient loading rates into waterways using airborne LiDAR combined with field-collected data. We applied this approach and explored its relationships to water quality at four sites within the Blackwater catchment in Northern Ireland for two analysis periods. GIS LiDAR image differencing revealed that volume changes in riverbank elevation equated to average erosion rates which indicated spatial and temporal variability in erosion rates. Combining the erosion rates with in-situ riverbank bulk density and total extractable phosphorus content provided sediment and phosphorus loading rates. The relative differences between estimated erosion at the different sites corresponded well with in-stream suspended sediment variations, but patterns for total phosphorus concentrations were more complex. We conclude that the use of LiDAR combined with field data is an innovative means for riverbank erosion quantification. Furthermore, by using LiDAR-to-LiDAR analyses, the reductions in erosion, sediment, and phosphorus loading rates following riverbank stabilization techniques can be determined. [ABSTRACT FROM AUTHOR]

Several geochemical characteristics ((La/Yb)N, Eu/Eu*, and Th content) of gray silts of the Volga River, suspended particulate matter of the Lena River, and silt–pelite fraction of bottom sediments in the Yangtze River are analyzed. It has been established that the above parameters of the chondrite-normalized lanthanide spectra and the Th content turn out in almost all cases to be comparable with their values determined for the specially prepared (removal of nonterrigenous carriers of rare earth elements (carbonate minerals, Fe–Mn oxyhydroxides, and organic components) pelite fractions of bottom sediments deposited near the mouths of named major rivers, and are retained over thousands of kilometers upstream from their deltas/mouths. The regulation of the Volga and Yangtze flows does not have a significant impact on parameters of the suspended particulate matter and bottom sediments under consideration. [ABSTRACT FROM AUTHOR]

The present study deals with investigating the spatial variation of suspended sediment properties in the Sutlej river basin (SRB). Twenty sampling locations were selected in the Sutlej river and its tributaries, and sediment sampling was carried out during monsoon season. The suspended sediment properties, namely suspended sediment concentration (SSC), particle size distribution (PSD), shape, and mineralogy, were measured through dynamic imaging, laser diffraction, and x-ray diffraction techniques. It was found that there is a wide variation of SSC, whereas there is an insignificant variation of PSD, shape, and mineralogy in the SRB. The highest SSC (2841 mg/l) was observed in the Kiran tributary, whereas the lowest (131 mg/l) was in the Titang tributary. The highest SSC (1749 mg/l) in the Sutlej main stem was observed at Khab, the topmost sampling location. The mean particle size varies from 6.00 to 25.36 µm (5.53–7.53 Φ). Shape analysis showed high degree of sphericity varying from 0.81 to 0.88 and slight elongation varying from 0.70 to 0.8. Mineralogical analysis depicts the dominance of quartz (66.73–82.25%) in the SRB. International Electrotechnical Commission IEC 62364 (IEC 62364 (2019) Hydraulic machines—Guidelines for dealing with hydro-abrasive erosion in Kaplan, Francis, and Pelton turbines, 2nd edn. Geneva, Switzerland) based average shape and hardness factors for SRB were estimated as 1.36 and 0.85, respectively. The maximum particle load for SRB was estimated as 0.014 kg/m3. [ABSTRACT FROM AUTHOR]

Investigating erosion and river sediment yield in high-mountain areas is crucial for understanding landscape and biogeochemical responses to environmental change. We compile data on contemporary fluvial suspended sediment yield (SSY) and 12 environmental proxies from 151 rivers in High Mountain Asia surrounding the Tibetan Plateau. We demonstrate that glaciers exert a first-order control on fluvial SSYs, with high precipitation nonlinearly amplifying their role, especially in high-glacier cover basins. We find a bidirectional response to vegetation's influence on SSY in the Eastern Tibetan Plateau and Tien Shan and identify that the two interacting factors of precipitation and vegetation cover explain 54% of the variability in SSY, reflecting the divergent roles of vegetation in promoting biogenic-weathering versus slope stabilization across bioclimatic zones. The competing interactions between glaciers, ecosystems, and climate in delivering suspended sediment have important implications for predicting carbon and nutrient exports and water quality in response to future climate change. [ABSTRACT FROM AUTHOR]

Hurricanes can benefit wetland accretion by augmenting the delivery of mineral sediment, an essential process allowing marshes to offset submergence during rising sea levels. Using Hurricane Gustav (2008, Louisiana) as a control, we examined eight synthetic storms with varying characteristics (track, speed, intensity, size) to evaluate sediment exchange between the inner shelf and bay and bay‐to‐marsh interfaces. All storms showed net landward sediment exchange from the inner shelf to the bay to the marsh—storms with closer proximity, higher intensity, and slower forward speed positively correlated with net sediment exchange; storm size had little impact. Except for slow‐moving storms (½ speed of Gustav), our analyses suggest that most hurricane scenarios cause net bay erosion, because more sediment is conveyed to landward wetlands than is replenished from erosion of the inner shelf. Our results suggest that the ongoing deepening of the bay will likely worsen because of rising sea levels. Plain Language Summary: Under most circumstances, hurricanes are perceived as agents of destruction that erode coastlines and destroy dwellings and infrastructure. However, for marshes and wetlands they can add much needed sediment and new sources of nutrients helping them to build vertically. As hurricanes move onshore, the accompanying large waves and currents suspend sediment into the water column followed by surge waters that carry this sediment onto wetlands. We have modeled this process using category 2 Hurricane Gustav that struck near Terrebonne Bay on the central Louisiana coast in 2008. By changing various hurricane characteristics, we find that in addition to the importance of storm track, forward speed and intensity cause the greatest net sediment exchange from inner shelf to landward bay and from bay to adjacent wetlands. Moreover, under most conditions a deficit of sediment replenishing bays will lead to their deepening and ultimately less sediment transferred to wetlands, hastening their demise. Key Points: Hurricane modeling indicates forward speed and intensity dominate net sediment exchange and transport along a shelf‐bay‐marsh systemAs hurricane forward speed slows, more sediment is moved onshore due to longer storm duration which entrains and transports more sedimentMost scenarios show inner shelf does not fully replenish sediment moved to wetlands suggesting long‐term sediment deficit and Bay deepening [ABSTRACT FROM AUTHOR]

In recent years, as river-borne sediment transport has decreased, land loss in estuarine areas has become increasingly severe. Particularly from 2009 to 2022, due to the reduced sediment load from the upper reaches of the Yangtze River, significant changes in the erosion-deposition conditions at the Yangtze River Estuary have become a critical concern. The suspended sediment concentration (SSC) in the estuary is closely linked to sediment content, and against this backdrop, this study aims to thoroughly explore the response mechanisms of the Yangtze River Estuary's SSC to changes in erosion-deposition conditions, with the goal of providing scientific bases and strategic recommendations for erosion-deposition management. To this end, this research collected historical water depth data for the Yangtze River Estuary, measured vertical distribution of SSC in September 2022, surface suspended sediment concentration (SSSC) data from 2021 to 2023, and 25 factors influencing SSSC, to analyze in detail the changes in the erosion-deposition conditions at the Yangtze River Estuary and the response mechanisms of SSC to these changes. The analysis showed that between 2009 and 2022, the mouth bar area of the Yangtze River Estuary experienced net erosion for the first time since 1958, with an annual erosion rate reaching 63.2 × 10^6 m3/yr, and the highest erosion rate occurring in the North Passage area, reaching 83.3 mm/yr. This phenomenon is likely caused by human-induced changes in underwater topography, with the Yangtze River Estuary shifting from deposition to erosion. Between 2021 and 2023, the turbidity maximum zone (TMZ) of the Yangtze River Estuary did not show regular changes in SSSC, which may be related to the frequent occurrence of typhoons and changes in sediment supply in the submerged delta of the Yangtze River Estuary. [ABSTRACT FROM AUTHOR]

Plastic debris pollution transported by river systems to lakes and oceans has emerged as a significant environmental concern with adverse impacts on ecosystems, food webs, and human health. Remote sensing presents a cost-effective approach to bolster interception and removal efforts. However, unlike marine environments, the optical properties of plastic debris in fresh waters remain poorly understood. This study aims to address this gap by providing an open-access hyperspectral reflectance database of floating weathered and virgin plastic debris found in river systems under controlled laboratory experiments. Utilizing natural waters from the Mississippi River, the database was assembled using a remote sensing data acquisition system deployed over a hydraulic flume operating under subcritical flow conditions and varying suspended sediment concentrations. The measurements encompass hyperspectral diffused light reflectance from ultraviolet (UV, 350 nm) to shortwave infrared (SWIR, 2500 nm) wavelengths. The database archived in Network Common Data Form (NetCDF) and Comma-separated values (CSV), offers valuable insights for better understanding key spectral signatures indicative of floating plastic debris, with different fractional abundance, in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Forestry operations and climate variability affect hydrologic response and sediment transport. Management of forested catchments under intense forestry activity in areas under climatic stress is critical. This study analyzes the impact of forest operations (thinning and clearcutting) on runoff (Q) and suspended sediment loads (SSL) in three small catchments (named N02, N03 and N04, respectively) in south-central Chile, where rainfall has decreased by 20% since 2010. Using modified double mass curves and piecewise regression, we separated the effects of forest practices and climate. Thinning in N02 initially reduced Q and SSL, with stable Q overtime, while final harvest in N03 and N04 increased Q, although less than expected. SSL surged post-harvest: 3.6 times in N03 and 1.8 times in N04, potentially linked to hillslope instability. Major SSL events contributed over 55% of post-harvest sediment yield in both catchments, with maximum yields reaching 7.2 tons ha−1 yr−1 in N03 and 4.1 tons ha−1 yr−1 in N04. SSL recovered to pre-harvest levels by the third year, except during a rainy year. Management practices likely contributed to lower SSL and faster recovery. These findings improve our understanding of catchment responses to forest practices and climate change, aiding sustainable forest and water resource management. [ABSTRACT FROM AUTHOR]

We investigate the influence of land use and land cover (LU/LC) changes on soil erosion and chemical weathering processes within the Nonguén watershed in the Coastal Cordillera of south-central Chile. The watershed is divided into three sub-basins, each characterized by distinct LU/LC patterns: native forest and exotic plantations. A comprehensive geochemical analysis, including trace elements and lithium (Li) isotopes, was conducted on river water and suspended sediment samples collected from streams within these sub-basins to assess how land management practices, particularly plantation activities, influence the geochemical composition of river systems. Our results show that sub-basins dominated by exotic plantations exhibit significantly higher concentrations of major and trace elements in suspended sediments compared to sub-basins dominated by native forests. The elevated trace element concentrations are primarily attributed to increased physical erosion due to forestry activities such as clear-cutting and soil disturbance, which enhance sediment mobilization. Notably, concentrations of elements such as Fe, Al, and As in plantation-dominated sub-basins are raised to ten times higher than in native-dominated sub-basins. In contrast, sub-basins with native forest cover exhibit lower levels of sediment transport and trace element mobilization, suggesting that native vegetation exerts a stabilizing effect that mitigates soil erosion. Despite the substantial differences in sediment transport and element concentrations, Li isotopic data (δ7Li) show minimal fractionation across the different LU/LC types. This indicates that land use changes impact the chemical weathering processes less compared to physical erosion. The isotopic signatures suggest that physical erosion, rather than chemical weathering, is the dominant process influencing trace element distribution in plantation-dominated areas. The study provides critical insights into how forestry practices, specifically the expansion of exotic plantations, accelerate soil degradation and affect the geochemical composition of river systems. The increased sediment loads, and trace element concentrations observed in plantation-dominated sub-basins, raise concerns about the long-term sustainability of forest management practices, particularly regarding their impacts on water quality in urban catchment areas. These results are of significant relevance for environmental management and policy, as they underscore the need for more investigation and sustainable land use strategies to minimize soil erosion and preserve water resources in regions undergoing rapid LU/LC changes. [ABSTRACT FROM AUTHOR]

Light is essential for phytoplankton photosynthesis and many other biogeochemical processes in the aquatic system. However, light regimes vary greatly in the estuaries and coasts due to the optical complexity of the Case-2 waters. In this study, observed vertical profiles of photosynthetically active radiation (PAR; 400-700 nm) in a highly turbid mega estuary, the Changjiang (Yangtze River) Estuary, are used to quantify the effects of sedimentary and biogeochemical components on PAR attenuation in the water column and associated ecological impacts. The in-situ data suggest suspended sediment plays the most crucial role in light diffuse attenuation coefficient (Kd) distribution, followed by salinity (i.e., an index for colored dissolved organic matter) and phytoplankton chlorophyll-a. A new parameterization of Kd, based on suspended sediment, chlorophyll-a concentration, and salinity, is fitted using multiple linear regression. The previous and new Kd parameterizations are further applied to a coupled hydrodynamics-sediment-ecosystem model to simulate spring phytoplankton blooms. Comparative model runs reveal that the new Kd parameterization resulted in a better representation of the spring bloom patterns in magnitude, horizontal distribution, and vertical thickness of the high chlorophyll-a band offshore the turbidity maximum zone during the spring bloom. In summary, accurate representations of underwater light fields in the optically complex Case-2 water are critical in understanding biophysical processes that control planktonic ecosystem dynamics in the estuaries and coastal seas. [ABSTRACT FROM AUTHOR]

This study aims to identify distinct small-scale temporary patterns between the river discharge and suspended sediment load for the main tropical rivers using continuous wavelet transform. Strong annual and irregular semi-annual variabilities, with few quarterly and interdecadal variabilities, are observed in river discharge and sediment load. The wavelet coherence reveals that the strongest in-phase coherence relationships exist between total suspended sediment and streamflow. The methodology for identifying the primary climate factors that integrate the partial wavelet coherence (PWC), multiple wavelet coherence (MWC), and quadruple wavelet coherence (QMWC) techniques is presented. The results show that the El-Nino/Southern Oscillation (ENSO) is the major regulator of streamflow followed by Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). The chosen rivers show a statistically significant ($p \le 0.05$p≤0.05) descending trend in sediment load but no significant positive or negative trend in river discharge. This could be due to regional sediment storage and large-scale stream events affecting the sediment transport dynamics. [ABSTRACT FROM AUTHOR]

The ecological implications of deep-sea mining, particularly the considerable discharge of suspended sediments during operational processes, have attracted substantial concerns. In order to reveal the metal regeneration dynamics in the polymetallic nodule area of the western Pacific Ocean, ex-situ sediment disturbance experiments were conducted on a research vessel. After two levels of regulated stirring disturbance were exerted for half an hour, the concentrations of 12 dissolved metals and physicochemical parameters, including Eh and pH, were monitored continuously in the overlying water for three days. Porewater samples were also collected at the starting and ending time of each experiment to detect the change of dissolved metal profiles within the sediments. The findings revealed that the sediment disturbance led to fluctuations in the concentrations of metals in the overlying water, with manganese exhibiting the most pronounced change at a coefficient of 208%. The temporal patterns of dissolved metal concentrations demonstrated a coherent behavior among certain metals, such as Li, V, Co, Ni, Rb, Mo, and Cs, which displayed an overall increase, ultimately surpassing the initial concentrations in the overlying water. In line with this, the metal concentration profiles in the porewater were also elevated. Spearman correlation analysis confirmed the synchronized behavior of these metals. The results suggested that the metals mobility might be governed by physicochemical factors in the overlying water. Moreover, the sedimentary features, such as grain size composition, and the morphological state of metals in sediments played pivotal roles in the differential responses of metal groups to sediment disturbance across stations. Conversely, the disturbance intensity was found to have a relatively minor impact on the dissolved metal behavior. The findings from the ex-situ experiments provided critical insights for predicting metal regeneration related to deep-sea mining, which are expected to be validated through rigorous monitoring protocols during future in-situ mining trials. [ABSTRACT FROM AUTHOR]

Internal phosphorus loading (IPL), as an important part of lake phosphorus cycle and the key to solve the eutrophication problem, is still an important cause of regional and seasonal algal blooms for some mesotrophic lakes located in plateau areas. We investigated the composition, distribution of P fractions in sediments and suspended particulate matter (SPM) of Erhai Lake, southwest China, and explored the relationships between environmental variables and spatial-temporal variations of P fractions. The total P (TP) in surface sediments ranged from 817 to 1216 mg/kg, with inert Ca-P (32%) and Res-P (24%) predominating, at a moderate level. The comparison of short-term release fluxes (0.08 mg/(m2·d)) and long-term release fluxes (0.09 mg/(m2·d)) reflected that the northern region was recovering slowly from the previous P pollution. Mobile-P (the sum of loosely adsorbed P, iron bound P, and organic P) accounted for 52.3% of the TP in SPM and showed high spatial-temporal variations, which were closely related to the growth of algae throughout the investigation. The results suggested that sediments could make a sustained contribution to IPL, and that the P in SPM was highly active and significantly contributed to eutrophication in Erhai Lake especially at the time of seasonal alternations. Our data provided important theoretical bases for the relationship between internal phosphorus loading and eutrophication in plateau lakes. [ABSTRACT FROM AUTHOR]

Optical turbidity and acoustic sensors have been widely used in laboratory experiments and field studies to investigate suspended particulate matter concentration over the last four decades. Both methods face a serious challenge as laboratory and in‐situ calibrations are usually required. Furthermore, in coastal and estuarine environments, the coexistence of mud and sand often results in multimodal particle size distributions, amplifying erroneous measurements. This paper proposes a new approach of combining a pair of optical turbidity‐acoustic sensors to estimate the total concentration and sediment composition of a mud/sand mixture in an efficient way without an extensive calibration. More specifically, we first carried out a set of 54 bimodal size regime experiments to derive empirical functions of optical‐acoustic signals, concentrations, and mud/sand fractions. The functionalities of these relationships were then tested and validated using more complex multimodal size regime experiments over 30 optical‐acoustic pairs of 5 wavelengths (420, 532, 620, 700, 852 nm) and six frequencies (0.5, 1, 2, 4, 6, 8 MHz). In the range of our data, without prior knowledge of particle size distribution, combinations between optical wavelengths 620–700 nm and acoustic frequencies 4–6 MHz predict mud/sand fraction and total concentration with the variation <10% for the former and <15% for the later. The results also suggest that acoustic‐acoustic signals could be combined to produce meaningful information regarding concentration and mud/sand fraction, while no useful knowledge could be extracted from a combination of optical‐optical pairs. This approach therefore enables the robust estimation of suspended sediment concentration and composition, which is particularly practical in cases where calibration data is insufficient. Plain Language Summary: Crucial decisions to govern the development of an estuary, delta, or coastal zone often rely heavily on the knowledge of where sediment accumulates. Such knowledge primarily comes from long‐term, high‐frequency monitoring of the transport of mud and sand particles in the water column. Optical or acoustic sensors are usually used for this task. Optical/acoustic sensors emit a light/sound beam to the particles and then measure the strength of the reflecting signals to estimate the concentration of the suspension. Since particles with different shape, size, and density respond differently to the light/sound signals, intensive calibrations are required whenever there is a significant change in the water column, for example, during a tidal cycle, seasonal variations between summer and winter. To avoid these tedious calibrations processes, we experimentally show that combination of optical and acoustic sensors in one measurement will help to derive empirical functions which in turn allow us to estimate the ratio of mud/sand and total concentration. Key Points: A new approach of coupling uncalibrated optical and acoustic signals to predict mud/sand fraction and total concentration was proposedWe experimentally show that without knowledge of the suspension estimations of mud/sand ratio and concentration can be as accurate as 10%–15%The new approach is particularly useful in cases where calibration data is insufficient or impractical [ABSTRACT FROM AUTHOR]

In this study, an acoustic Doppler current profiler (ADCP) operating at 600 kHz was installed on an ocean data buoy in the Qigu waters, Taiwan, to gather real-time sound echo intensity data. These data were then correlated with turbidity measurements obtained by a turbidimeter mounted on the buoy's mooring line at a water depth of 13 m. The data buoy operated from 6 June to 16 August 2017. During this period, turbidity measurements were recorded from 6 to 21 June 2017. This study established a calibration between the sound echo intensity measured by the ADCP and the turbidity measured using the turbidimeter; a strong linear correlation was discovered between these two variables. This correlation enabled the conversion of echo intensity data into a continuous time series of turbidity measurements, facilitating real-time and long-term monitoring of coastal water turbidity through the deployment of a buoy equipped with an ADCP. The relationships between turbidity and environmental factors such as rainfall, tides, current speeds, and wave activity over an extended period were then investigated. The results revealed that stronger tides and currents in the Qigu waters often lead to higher turbidity, suggesting that these two factors are the primary driving forces for sediment transport in the Qigu waters. Additionally, sampling of water in the Qigu area revealed sediment particles of size ranging from 2 to 120 μm. [ABSTRACT FROM AUTHOR]

The Yellow River, China's second-largest river, is renowned for its high sediment content. In response to the potential impacts of climate change on Yellow River water resources and water environmental management, an advanced monitoring and forecasting system for water and sediment throughout the entire Yellow River basin—from its source to the sea—is urgently needed. In this paper, based on the current status of water and sediment monitoring technologies, we proposed an integrated remote sensing monitoring network that combines satellite remote sensing, drone remote sensing, and ground-based wireless automatic monitoring networks, aiming to achieve the digital monitoring of water and sediment across the entire Yellow River basin, from its upper reaches to its estuary in the Bohai Sea. By utilizing ground-based in situ hyperspectral stations for sediment source areas in the upper reaches, such as the Qingshui River basin in Ningxia, and satellite remote sensing for midstream processes in the Xiaolangdi reservoir before the flood season in 2023, as well as downstream monitoring at the Yellow River estuary, this paper demonstrates the novelty and efficiency of the space–air–ground integrated remote sensing monitoring technology. [ABSTRACT FROM AUTHOR]

Desanding facilities (DFs) limit particle sizes and reduce the suspended sediment load in hydropower plants. Multiple successive tranquilizing racks (TRs) at settling chamber inlets are a cost-efficient structural measure to homogenize the flow and reduce local velocities and turbulence in the chambers. We summarized the state of the art of TRs and conducted detailed flow velocity measurements in the settling chambers of a DF with TRs. In the first campaign, a pronounced flow concentration beneath the vertical bars of the TRs was found, resulting in flow velocities along the invert of up to 3.5 times the average cross-sectional velocity. Because this impairs the trapping efficiency, the TR bars were extended downward to achieve a more even distribution of the flow resistance over the entire flow section. A subsequent measurement campaign confirmed a more homogeneous flow field and a considerable reduction of the turbulence intensities and turbulent kinetic energy, which were the lowest compared to six other DFs. The results highlight the potential to modify existing TRs at other DFs with inhomogeneous flow fields and the practical importance of TR design for new DFs. Practical Applications: In hydropower plants (HPPs) with water intakes located at sediment-laden rivers, DFs are crucial for reducing the sediment load in the turbine water, consequently minimizing wear on the turbines. A DF usually consists of one or several chambers through which the water flows slowly, allowing sand particles to settle. However, for geometrical, hydraulic, and economic reasons, the flow at the chamber inlet is often not favorable for settling. In such situations, TRs can be installed to slow down and distribute the inflow more evenly. Because no general design guidelines for TRs are available, we reviewed the state of the art based on literature and present the field investigation of flow fields in a DF with TRs. We found an unfavorable flow concentration and modified the TRs to cover the whole flow section. This resulted in more favorable conditions for settling, also in comparison with other DFs. In DFs with inhomogeneous inflow conditions, suitably designed TRs enhance the trapping efficiency and contribute hence to the cost- and energy-efficient use of the hydropower potential at sediment-laden rivers. [ABSTRACT FROM AUTHOR]

A filter unit (FU) is a structure installed with the aim of protecting the foundation of an embankment revetment from riverbed scouring, and there are cases in which sediment is deposited in the surrounding area after installation. Vegetation growth in sediment can improve the environment and protect revetments. Hydraulic experiments and numerical calculations were conducted to investigate how suspended sediments are deposited around FUs over a large area within a short period of time. We performed suspended sediment deposition experiments using FU models and confirmed that sediment deposition can be calculated accurately using a two-dimensional planar model. We also analyzed FU placement and its impact on topographical changes in an actual river in which FUs were installed. The results showed that (1) the continuous placement of FUs inhibits sediment deposition on the downstream side; (2) arranging FUs at intervals facilitates sediment deposition even under small-scale floods; and (3) employing an interval of half the FU width for every three or more FUs can effectively promote suspended sediment deposition at intervals. [ABSTRACT FROM AUTHOR]

Sediment transport in urban streams is a critical environmental issue, with significant implications for water quality, ecosystem health, and infrastructure management. Accurately estimating suspended sediment concentration (SSC) is essential for effective long-term environmental management. This study investigates the relationships between streamflow, turbidity, and SSC in Dry Creek, South Australia, to understand sediment transport dynamics in urbanised catchments. We collected grab samples from the field and analysed them in the laboratory. We employed statistical modelling to develop a sediment rating curve (SRC) that provides insights into the sediment transport dynamics in the urban stream. The grab sample measurements showed variations in SSC between 3.2 and 431.8 mg/L, with a median value of 77.3 mg/L. The analysis revealed a strong linear relationship between streamflow and SSC, while turbidity exhibited a two-regime linear relationship, in which the low-turbidity regime demonstrated a stronger linear relationship compared to the high-turbidity regime. This is attributed to the urbanised nature of the catchment, which contributes to a first-flush effect in turbidity. This contributes to sediment hysteresis, resulting in non-proportional turbidity and SSC responses to streamflow changes. The findings demonstrate the effectiveness of a streamflow-based SRC for accurately predicting sediment discharge, explaining 97% of the variability in sediment discharge. The sediment discharge predicted using the SRC indicated a sediment load of 341.8 tonnes per year along the creek. The developed sediment rating curve provides a valuable tool for long-term sediment management in Dry Creek, enabling the assessment of downstream environmental risks. By addressing data limitations, this study contributes to a deeper understanding of sediment transport dynamics in urbanized environments, offering insights for informed decision-making and effective sediment management strategies. [ABSTRACT FROM AUTHOR]

Suspended sediment (SS) has a wide range of negative effects such as increased water turbidity, altered habitat structures, sedimentation, and effects on hydraulic systems and environmental engineering projects. Nevertheless, the methods for accurately determining SS sources on a basin-scale are poorly understood. Herein, we used a simplified neural network analysis (NNA) model to identify the sources of SS in Japan's Oromushi River Catchment Basin. Fine soil samples were collected from different locations of the catchment basin, processed, and separately analysed using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The sampling stations were grouped according to the type of soil cover, vegetation type and land-use pattern. The geochemical components of each group were fed into the same neural network layer, and a series of equations were applied to estimate the sediment contribution from each group to the downstream side of the river. Samples from the same sampling locations were also analysed by XRD, and the obtained peak intensity values were used as the input in the NNA model. SS mainly originated from agricultural fields, with regions where the ground is covered with volcanic ash identified as the key sources through XRF and XRD analysis, respectively. Therefore, based on the nature of the surface soil cover and the land use pattern in the catchment basin, NNA was found to be a reliable data analytical technique. Moreover, XRD analysis does not incorporate carbon, and also provides detailed information on crystalline phases. The results obtained in this study, therefore, do not depend on seasonal uncertainty due to organic matter. [ABSTRACT FROM AUTHOR]

Water jet scouring technology is extensively applied in marine engineering, harbor maintenance, river training, and various other fields, showcasing a broad spectrum of potential applications. However, achieving a comprehensive understanding of the transient sand scouring characteristics of water jets remains challenging due to the inherent complexity of the coupled flow structure involving submerged jets and environmental fluids, along with the intricate dynamics of two-phase flow. This study, rooted in numerical simulation and experimental validation, introduces pulse characteristics into a submerged jet. A thorough investigation is conducted to explore the transient sand scouring characteristics and sand transport laws of the submerged jet under diverse working conditions. The results of this study revealed that the main reason for the asymmetry of the sand pit morphology is not the non-uniform distribution of sand grains, but more likely caused by turbulence effects. Simultaneously, within the initial 0.25 s of the pulse cycle, suspended sediment resulting from the pulsed jet in the preceding cycle gradually transports to the dune and its surrounding areas. Subsequently, from 0.25 s to 0.5 s, sediment on both sides of the pit's bottom undergoes movement and amalgamation with the sediment that remained unsettled during the previous cycle. The findings reveal that higher jet velocities significantly enhance sediment suspension, migration, and redeposition, leading to deeper erosion and the rapid formation of the sand pit's outline within 2 s. Additionally, the jet velocity and the impact distance are identified as critical factors influencing erosion depth and sediment dynamics. These insights advance the understanding of erosion mechanisms driven by pulsed jets, highlighting their impact on sediment transport processes. The research findings provide important guidance for dredging and ocean engineering fields and offer a theoretical basis for improving the understanding of submerged jet scouring mechanisms. [ABSTRACT FROM AUTHOR]

Port coasts are affected by waves and tidal currents, and sediment continues to silt up, leading to a reduction in the depth of water in the channel, blocking the channel and seriously affecting the safe operation of ports. The main cause of sediment deposition in ports is suspended sediment transport, and the characteristics of the vertical distribution of suspended sediment concentrations are the embodiment of the suspended sediment transport law. This paper is divided into three parts to study the vertical distribution characteristics of suspended sediment concentrations. Firstly, the shortcomings of the traditional diffusion model were analysed by using the finite mixing theory (FMT); secondly, the sediment mixing length coefficient κs model was introduced and combined with the sediment group settling velocity model to establish the vertical distribution model of suspended sediment concentrations under wave–current; finally, the effects of various factors on the vertical distribution of the suspended sediment concentration were investigated. The results show that the model in this paper has the characteristics of "low variance and low bias", which solves the problem that κs is difficult to determine. When the model κs < κs′ (κs′ = 0.4), the concentration of suspended sediment predicted by κs′ is overestimated, and vice versa. As the sediment concentration increases, the interaction between particles increases and the vertical distribution of the suspended sediment concentration shows the pattern of "small top and large bottom". The larger the particle size, the greater the sedimentation rate of the suspended sediment, and a large amount of sediment will be suspended near the bottom without mixing. The higher the wave height, the stronger the boundary layer turbulence and the movement of the water particles' trajectory, and the smaller the difference in sediment concentration between the bottom and the sea surface. [ABSTRACT FROM AUTHOR]

Chemical weathering processes are becoming increasingly important in studies on carbon cycling because they are responsible for increased solute fluxes in the proglacial zone, can effectively sequester atmospheric CO2 and raise carbon budgets for lateral transport via rivers. Here, we examined the hydrochemical and hydrogeochemical processes, solute sources and factors controlling riverine pCO2 of the Alaknanda River and its tributaries for three sampling seasons, viz. pre-monsoon (May 2021), post-monsoon (October 2021) and winter (January 2022). The surface water is enriched with Ca2+ and Mg2+ as the dominant cations, while HCO3− and SO42− were the major anions. Gibbs's plot confirmed rock weathering as the leading mechanism in controlling the hydrochemistry of the basin. The chemical composition of river water was mainly regulated by the weathering of carbonate end members: dolomite, limestone and feldspar along with small inputs from silicate weathering. The mean pCO2 values in the mainstream (1702.7 µatm), Pindar (2267.9 µatm) and Mandakini (1136.1 µatm) revealed the streams were oversaturated with CO2 having a higher rate of exporting excess CO2 gas to the atmosphere. The study showed the persistence of high pCO2 closed system characteristics associated with increased suspended sediment concentration resulting from carbonate weathering, dominance of HCO3− over SO42− and thereby results in high values of C ratio. Principal component analysis of the water chemistry suggests that weathering contributes about 41%, while humans contribute about 13% of the ionic load to the river. This study is one of its kind to understand the system characteristics of Alaknanda River water. [ABSTRACT FROM AUTHOR]

River confluences, which are characterized by complex hydrodynamics, are key nodes for flood control and environmental protection. Two field surveys were carried out at the confluence of the Yangtze River and Poyang Lake to investigate the transient character of flow structures, which are often assumed steady. Repeat‐transect acoustic Doppler current profile measurements were processed and analyzed, adopting a new method to separate mean flow from turbulence and measurement error based on physics‐informed generalized Tikhonov regularization. The two field surveys were characterized by two distinct mixing interface modes: A so‐called Kelvin–Helmholtz (KH) mode, and a wake mode. In KH mode, large‐scale flow fluctuations were observed. These flow fluctuations exert a substantial influence on the alternation of secondary flows by changing the water surface pressure gradient, affecting the intensity of secondary flows rather than their spatial structure. We infer that temperature‐induced stratification is the main cause of this. In the wake mode, multiple vortices in the wake region at the confluence apex also produced flow fluctuations, directly related to the primary velocity gradient. We argue that even for constant incoming flows, secondary flow at river confluences can exhibit channel‐scale unsteadiness related to migration of the turbulent mixing interface. Our findings highlight the crucial role of density effects in regulating secondary flow unsteadiness, which is essential for understanding contaminant and sediment dispersal in river systems. Plain Language Summary: Secondary flow at river confluences is the vertical circulation of water perpendicular to the streamwise river axis. It is capable of transporting suspended sediment or pollutants from the river's surface and bottom to either of the two opposite banks. This feature affects river morphology as well as the aquatic ecological environment. It is commonly assumed that secondary flow remains steady in field observations, and time‐averaging is employed to obtain this steady flow pattern. To investigate the hypothesized transient character of secondary flow, we applied principles from water flow physics on acoustic flow measurements. This approach eliminated flow velocity data contributions from turbulence and measurement errors, allowing us to obtain near‐instantaneous secondary flow structures. The results reveal that the interaction between incoming flows at the confluence can cause the secondary flow indeed to change over time. These variations depend on the discharge and density difference between waters in the two rivers. Our findings suggest that secondary flows are less stable than commonly assumed, and time‐averaged flow field measurements may be insufficient when aiming to understand flow dynamics at river confluences. Key Points: The mechanisms governing unsteady secondary flow at a large scale river confluence depend on the occurring flow modeIn Kelvin‐Helmholtz mode, primary flow fluctuations translate to secondary flow variation by alternating centrifugal and pressure forcingIn wake mode, vortex within mixing interface cause the secondary flow structure to be unsteady near the confluence apex [ABSTRACT FROM AUTHOR]

Black bloom is a very serious water pollution phenomenon in eutrophic lakes, with Fe(II) and S(−II) being the key limiting factors for this problem. In this paper, three different machine learning methods, namely, Random Forest (RF), Gaussian Mixture Model (GMM), and Bayesian Network (BN), were used to explore the complex interactions among Fe(II), S(−II), and other aquatic factors in the estuary of Chaohu Lake to better characterize and monitor water degradation by black bloom. The results of RF showed that total nitrogen (TN), ammonia, total phosphorous (TP), suspended sediment concentration (SSC), and oxidation–reduction potential (ORP), which were chosen from 11 factors, had the most important relationships with Fe(II) and S(−II). The 69 sampling sites were divided in three groups identified as worst, worse, and bad according to the observed values of seven factors using the GMM. Then, the BN model was applied to three observation groups. The results showed that the structures of the interaction networks were different between the groups. S(−II) controlled only SSC production in the bad and worse group sites, while SSC was determined by both S(−II) and Fe(II) in the worst group. Ammonia and TN exhibited the most direct importance for S(−II) and Fe(II) production in all observation groups. According to the indications from the BNs, potential management strategies for different water pollution conditions were developed. Finally, the threshold values of Fe(II), S(−II), TP, ammonia, TN, SSC, and ORP, which were 0.80 mg/L, 0.04 mg/L, 0.45 mg/L, 3.44 mg/L, 4.15 mg/L, 55 mg/L, and 135 mv, respectively, were determined on the basis of the BN models. These values will be helpful to develop accurate strategies of oxygenation to quickly eliminate black bloom in the lake. [ABSTRACT FROM AUTHOR]

The partial detonation of munitions used in military exercises leaves behind energetic particles on the surface of soil. Energetic particles deposited by incomplete detonations can then dissolve and be transported by overland flow and potentially contaminate ground and surface waters. The objective of this study was to evaluate the mechanisms of transport of Composition B, a formulation that includes TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5- trinitro-1,3,5-triazine) during overland flow. The transport of Composition B was examined using a rill flume with three flow rates (165-, 265-, and 300-mL min-1) and four energetic particle sizes (4.75--9.51 mm, 2.83--4.75 mm, 2--2.83 mm, and <2 mm). After each erosion simulation, energetic particles remaining on the soil surface were measured along with energetics dissolved in runoff, in suspended sediment, and in infiltration. Smaller particle sizes led to greater transport in both solution and sediment. The properties of the energetic compounds also influenced transport. More TNT was transported in runoff than RDX, likely due to TNT's higher solubility and dissolution rates, however, overall, dissolved energetics in runoff and infiltration accounted for very little of the total transport. Most transport of Composition B was the result of the physical movement of energetic particles and flakes by erosion forces. This study's results allow for improved prediction of Composition B transport during overland flow. [ABSTRACT FROM AUTHOR]

Numerous studies have demonstrated that high suspended sediment concentration (SSC) can change density distribution and affect water mixing, but few scholars have investigated this impact on numerical simulations of estuarian salinity distribution. The Qiantang Estuary is a macro-tidal estuary with high SSC, which has a more significant influence on water density than that of salinity. Therefore, this paper established a three-dimensional (3D) numerical model coupling flow, salinity and SSC based on Delft3D and first analyzes the impact of SSC on salinity distribution under different runoff and tidal conditions in the Qiantang Estuary. The results indicated that simulated salinity generally decreases when considering the impact of SSC, suggesting a weakening effect on saltwater intrusion. The distribution of salinity difference (DS) and SSC show a strong spatial and temporal correlation, and DS peak increases and shifts upstream as the tidal range increases or runoff discharge decreases. The mechanism of SSC influencing saltwater intrusion can be summarized as follows: On the one hand, SSC increases the water density, which weakens the driving force for saltwater to move upstream, causing a decrease in flood current velocity and water level, and thereby diminishing the advective transport of salinity. On the other hand, SSC enhances density stratification, which weakens vertical turbulence and reduces the dispersive transport of salinity. These combined effects reduce both the advective and diffusive salinity fluxes during the flood tide, ultimately leading to a decrease in upstream salinity. Therefore, neglecting this effect in estuaries with high SSC can cause significant deviations in salinity simulation results, especially under low-flow and high-tide conditions. [ABSTRACT FROM AUTHOR]

The parameterization of suspended sediments in vegetated flows presents a significant challenge, yet it is crucial across various environmental and geophysical disciplines. This study focuses on modeling suspended sediment concentrations (SSC) in vegetated flows with a canopy density of avH ∈ [0.3, 1.0] by examining turbulent dispersive flux. While conventional studies disregard dispersive momentum flux for avH > 0.1, our findings reveal significant dispersive sediment flux for large particles with a diameter‐to‐Kolmogorov length ratio when dp/η > 0.1. Traditional Rouse alike approaches therefore must be revised to account for this effect. We introduce a hybrid methodology that combines physical modeling with machine learning to parameterize dispersive flux, guided by constraints from diffusive and settling fluxes, characterized using recent covariance and turbulent settling methods, respectively. The model predictions align well with reported SSC data, demonstrating the versatility of the model in parameterizing sediment‐vegetation interactions in turbulent flows. Plain Language Summary: This research focuses on the movement of suspended sediments in rivers, specifically in areas with vegetation. Traditional models cannot depict this process, prompting the development of a new methodology that merges conventional scientific techniques with advanced machine learning. The proposed approach has demonstrated superior performance, particularly in transitional areas between vegetated and non‐vegetated zones. The significance of this study lies in its contribution to modeling an often‐overlooked spatial term (called "turbulent dispersive flux") by showing that its magnitude is much greater than conventionally supposed. This study also advances the current methodology of including physics‐based artificial intelligence to model sediment dynamics in vegetated river systems. The proposed approach is versatile and can be included in the large‐scale transport models. Key Points: Rouse budget without dispersive flux cannot describe coarse sediment concentration in vegetated flowsA machine‐assisted physical closure for turbulent dispersive flux from spatial average is proposedPredicted sediment concentration results agree with reported experimental data in the literature [ABSTRACT FROM AUTHOR]

The non-uniform suspended sediment flowing into the Yangtze River Estuary (YRE) has a substantial impact on riverbed evolution and the ecological environment. Conducting a numerical simulation can provide missing measurement data and act as an important support for river management. In this study, we developed a formula for determining the non-uniform suspended sediment-carrying capacity (SCC) based on the statistical theory of sediment transport. The formula was applied to a river network model domaining the tidal section of the lower reaches of the Yangtze River (LYR) to simulate the non-uniform suspended sediment flowing into the YRE. The verification results showed that the model accurately simulated fine-grained sediments with a high measurement accuracy. The simulation results for coarsegrained sediments were consistent with riverbed evolution thatmanifests as erosion. Owing to the sediment transport complexity in natural rivers, we propose a method for optimizing calculations of the SCC that providesmore accuratemodeling results and can be adapted when the observational measurement accuracy is improved in the future. These findings provide support for simulations and measurements of non-uniform suspended sediment transported in the LYR. [ABSTRACT FROM AUTHOR]

The brine‐seawater interface (BSI) is a unique type of groundwater‐seawater interface (GSI) characterized by the higher density of underground brine compared to seawater. This study focuses on characterizing the bay‐scale BSI morphology and identifying submarine‐groundwater discharge windows using a comprehensive in‐situ geophysical detection on the south bank of Laizhou Bay. Our findings reveal that the BSI forms an extensive mixing zone (15–20 km) without distinct contours between waters of varying salinities. The discharge windows for underground brine are located in nearshore areas with fine sand distribution and offshore pockmark areas. Hydraulic and salinity gradients drive the underground brine discharge through these windows. The aquitard window is the primary area for shallow and deep brine exchange, likely evolved from paleochannels, ancient tidal creeks, or ancient underwater barriers. These findings provide crucial modeling support for analyzing environmental evolution mechanisms and theoretical basis for planning the underground brine mining in similar coastal regions. Plain Language Summary: This study investigates a unique interface where underground brine meets seawater, known as the brine‐seawater interface (BSI). Unlike regular groundwater‐seawater interfaces, the BSI features brine that is denser than seawater. The research focused on characterizing the BSI's morphology and identifying locations where brine discharges into the sea along the south bank of Laizhou Bay. By using advanced detection methods and analyzing samples, the study found that the BSI forms a broad mixing zone of about 15–20 km. There are no clear boundaries between water of different salinities within this zone. The study also identified specific areas near the shore with fine sand and offshore pockmarks where brine discharges occur. These areas are recognized by the presence of suspended fine sediment on the seabed. The movement of brine through these discharge areas is driven by differences in water pressure and salinity. The study suggests that ancient channels and barriers underwater play a significant role in these discharge processes. Understanding these dynamics can help us manage coastal environments and predict how changes in sea and land interactions may affect them. Key Points: The bay‐scale brine‐seawater interface (BSI) is a long mixing zone with underground water salinity ranging from high to low from land to seaThe nearshore seabed fine sand area and offshore pockmarked area are the main windows for underground brine dischargeThe BSI morphology and submarine groundwater discharge/exchange windows can be identified by comprehensive geophysical detection results [ABSTRACT FROM AUTHOR]

This study presents in situ, high-resolution optical measurements of particle size distributions (PSD) within sediment plumes generated by a pre-prototype deep seabed nodule collector vehicle operating in the abyssal Pacific Ocean. These measurements were obtained using a cutting-edge instrument, the LISST-RTSSV sensor. The data collected in situ reveal marked differences compared to previously reported laboratory-based, ex situ measurements. The grain size and other key particle shape characteristics are found to be dependent on multiple factors, including the collector vehicle maneuvers, the time elapsed following sediment discharge, and the complex hydrodynamic processes that generate the sediment in suspension. Significantly, the PSD from a highly complex succession of straight-line maneuvers converges to that of the canonical case of a simple straight-line driving maneuver within a timescale of ten minutes. Our results underscore the importance of parameterizing sediment plume transport models based on well-informed, comprehensive PSDs of detrained suspended sediment measured in situ at adequate timescales and in regions no longer strongly influenced by active and complex hydrodynamic processes. [ABSTRACT FROM AUTHOR]

Fluvial sediment dynamics in mountain rivers are changing rapidly in a degrading cryosphere, raising the potential for erosive rainfall and runoff and detrimental effects on downstream areas. Hence, we need to understand better what characterises and drives episodic pulses of water and suspended solids in rivers. Here, we infer different types of such sediment-discharge events from 959 automatically detected events based on 16 metrics derived from 15 min time series of streamflow and suspended sediment concentrations from Vent–Rofental in the high Ötztal Alps, Austria. We use principal component analysis to extract uncorrelated event characteristics and cluster event types with a Gaussian mixture model. We interpret the thus inferred event types with catchment metrics describing antecedent conditions, hydrometeorological forcing, and fraction of catchment area with freezing temperatures and snow cover. We find event magnitude, hysteresis, and event shape complexity to be the main factors characterising the overall event regime. The most important characteristics distinguishing the event types are suspended sediment and streamflow magnitude and complexity of the hydro- and sedigraphs. Sediment-discharge hysteresis is less relevant for discerning event types. We derive four event types that we attribute to (1) compound rainfall–melt extremes, (2) glacier and seasonal snowmelt, (3) freeze–thaw-modulated snowmelt and precipitation events, and (4) late-season glacier melt. Glacier and snowmelt events driven by warm conditions and high insolation were the most frequent and contributed some 40 % to annual suspended sediment yield on average; compound rainfall–melt extremes were the rarest but contributed the second-highest proportion (26 %). Our approach represents a reproducible method for objectively estimating the variety of event-scale suspended sediment transport conditions in mountain rivers, which can provide insights into the contribution of different drivers to annual sediment yields in current and future regimes. Our findings highlight the importance of both meltwater and rainfall–runoff as drivers of high-magnitude suspended sediment fluxes in mountain rivers. [ABSTRACT FROM AUTHOR]

River sediment load estimation poses a critical challenge for water engineers due to its complex and nonlinear hydrological processes. This study assessed the amount of suspended sediment at the Bagh-e-Kalayeh hydrometric station on the Alamut River in the Qazvin province of Iran using two hydrological and meteorological variables, including discharge and rainfall, by considering three scenarios (discharge, discharge + monthly rainfall, and discharge + monthly rainfall + daily rainfall). For modeling, kernel-based data-driven methods, including Gaussian process regression (GPR) and support vector regression (SVR), and tree models, including the M5 tree, random forest (RF), random tree (RT), extra trees, reduced error pruning tree (REPT), and multi-search methods, were used. The results showed that the best performance was achieved by the SVR, with r = 0.948, Wilmot index = 0.965, and RMSE = 0.011 in the first scenario (only discharge). Discharge had the most significant impact on sediment estimation compared to rainfall. It was determined that the suspended sediment load in the Alamut River can be successfully estimated by the SVR method, where only the discharge was used as the input parameter. Additionally, the results indicated that given its characteristics and inherent features, the multi-search method can be used as a complementary approach in sediment modeling, especially in situations where the data volume is not extensive. [ABSTRACT FROM AUTHOR]

Stratigraphic positions and the nature of some breccias and mudstones observed in the Lower Cretaceous McMurray Formation type section (Alberta, Canada) challenge the existing fluvial point bar facies models. The currently applied large‐scale, tidally influenced, sandy bedload facies model suggests that point bars fine upward, where breccias and cross‐strata occur at the base of the succession and mud content increases upward. Instead, this study documents that: (i) mudstone clast breccias are not exclusively associated with basal channel‐lag deposits and can occur throughout the point bar; and (ii) stratified mudstones are not limited to the top of the fining‐upward succession and can occur at or near the channel base. This outcrop data, including lithology, sedimentary structures, trace fossils, bed thickness and boundaries, and the nature of stratal packages, further suggests dynamic interplay between fluvial and tidal processes. This article discusses the potential role of high‐magnitude river floods in temporarily elevated suspended sediment concentrations and highlights that fluid mud processes played a crucial role in mud deposition in both tide‐influenced and fluvial parts of the system. Fluid mud processes allowed mud deposition along the channel base and across the point bar accretion surfaces. The breccias predominantly consist of broken pieces of inclined heterolithic strata and mostly occur on accretion sets of point bars, suggesting erosion and collapse of the point bar rather than of the cutbank. This work introduces a novel perspective to the existing models of point bar sedimentation, offering a new end member and concepts for the interpretation of subsurface data. The authors hope that this research encourages further investigations into similar phenomena elsewhere in the world. [ABSTRACT FROM AUTHOR]

[Objective] The transportation of sediment via glacial meltwater can not only reflect the glacial erosion and land form evolution? but also is one of the important sediment sources for the downstream river. Thus, understanding the suspended sediment and bed load dynamics in glacier meltwater runoff on the Tibetan Plateau is significant for predicting glacier land form evolution and conducting downstream disaster prevention and mitigation efforts. Methods］ To achieve the goal, the variations of flow discharge, sediment concentration of suspended load, and bed load transport rate per unit width were monitored at the downstream channel of Qiyi Glacier in the Qilian Mountains from August 11 to 24, 2023. Based on the observed data, the relationship curves of flow discharge-water level, sediment concentration of suspended load-flow discharge, and unit bed load transport rate-flow shear stress were developed to obtain the variations of both water flow and sediment transport throughout the study period. Results］ The sediment concentration of suspended load and the bed load transport rate in the downstream channel of Qiyi Glacier are predominantly influenced by the variations in meltwater runoff, exhibiting pronounced daily fluctuations. The daily nadir of suspended sediment concentration is observed around 1(): ()()，while the acme occurs around 16: ()()• The median particle size of the sediments is approximately ().3 mm, indicating a fine-grained sediment composition. The variation trend of bed load transport rate versus time is almost the same to the suspended load, excepting at ()5: ()0 -- 09: 0(). During this period, there is no bed load in the channel since the flow shear stress is insufficient to mobilize and transport the bed load. Note that the median particle size of bed load is about 1 2 mm. The sediment transport in the downstream channel of Qiyi Glacier is primarily dominated by suspended sediment, and the daily sediment transport amount of bed load is much smaller than that of suspended sediment, accounting for only 1. 73% 〜2. 81 % of the daily sediment transport amount of suspended sediment. Air temperature of glacier is a critical factor influencing the flow discharge of glacier meltwater, the sediment concentration of suspended load, and the transport rate of bed load. Moreover, as air temperature of glacier rises, both the flow discharge and suspended sediment concentration display linear increasing trends, while the bed load transport rate exhibits an exponential increase. Conclusion] This implies that, in future climate change scenarios, where the flow discharge of glacier meltwater increases, the suspended and bed loads transport within the Qiyi Glacier meltwater will become more significant and deserve more attentions. [ABSTRACT FROM AUTHOR]

Several climate-driven processes take place in the Arctic fjords. These include ice–ocean interactions, biodiversity and ocean circulation pattern changes, and coastal erosion phenomena. Conducting long-term oceanographic monitoring in the Arctic fjords is, therefore, essential for better understanding and predicting global environmental shifts. Here we address this issue by introducing a new hydrographic dataset from Hornsund, a fjord located in the southwestern part of the Svalbard archipelago. Hydrographic properties have been monitored with vertical temperature, salinity and depth profiles in several locations across the Hornsund fjord from 2015 to 2023. From 2016 onward, dissolved oxygen and turbidity data are available for the majority of casts. The dataset contributes to the so far infrequent observations, especially in spring and autumn, and extends the observations, typically concentrated in the central fjord, to the areas adjacent to the tidewater glaciers. Because sediment discharge from glaciers and land is an inseparable part of the glacier–ocean interactions, the suspended sediment concentration in the water column and the daily sedimentation rate adjacent to the tidewater glaciers are monitored with regular water sampling and bottom-moored sediment traps. Here we present the planning and execution of the monitoring campaign from the collection of the data to the postprocessing methods. All datasets are publicly available in the repositories referred to in the "Data availability" section of this paper. [ABSTRACT FROM AUTHOR]

Hydrological models are vital for water management to determine in-stream flow, irrigational water, domestic water supply, and biodiversity conservation. This study formulates a hydrological model with a novel approach for streamflow and sediment load in the QGIS-supported Soil and Water Assessment Tool for the Halda River catchment, a unique ecological habitat for natural carp spawning and freshwater sources. The daily simulation uses an innovative stage-discharge relationship technique from available 15-day interval flow data. The model evaluation parameters R2 values 0.80 and 0.62, and NS values 0.81 and 0.61 for calibration and validation of streamflow suggested excellent agreement in the seasonal cycle and most of the monsoon peak flow. The streamflow/precipitation ratio indicates a significant influence of groundwater through infiltration. The baseflow shows a decreasing trend. The sediment load based on suspended sediment concentration at a downstream location is 1,625 tons/day. On the contrary, the model prediction is 30 times lower. The scattered sediment load data support the model estimate by considering relatively lower intervention or land use change in its upstream. This model provides a baseline for daily flow and sediment load for scenario modeling (e.g., climate change, land use change) for environmental flow estimation of the fish habitat, freshwater supply, irrigation, and salinity intrusion. [ABSTRACT FROM AUTHOR]

Wave nonlinearity and free surface effects are recognized as important factors for sediment transport under nonlinear waves. Existing studies primarily focus on oscillatory water tunnel (OWT) instead of real waves for sediment transport due to the challenges in constructing real-scale wave tank. In contrast to OWT, the wave tank performs both wave nonlinearity and free surface effect on sediment transport. A numerical wave-sediment tank is developed for strong nonlinear wave propagation over sediment bed with low computational cost. The nonlinear wave is generated by defining the inlet boundary condition and absorbed by using a damping function, and the classical volume of fluid method is used to handle the free surface. The numerical tank further considers particle wake vortex effect and modifications in relative velocity of high sediment concentration, and incorporates phase lag, mass conservation, acceleration effect, and asymmetric wave boundary layer into near-bed sediment conditions. Therefore, the numerical tank avoids complex calculations for near-bed hyper-concentrated sediment in comparison with a two-phase model, i.e., the calculation of particle collision, friction, and detection of mobile bed surface. The numerical tank reasonably agrees with large-scale wave flume experiments and a two-phase model including free surface wave, and successfully performs sediment transport induced by strong nonlinear (second-order Cnoidal) wave. Compared to the OWT, the extra onshore streaming caused by free surface wave significantly enhances onshore sediment transport. [ABSTRACT FROM AUTHOR]

This study presents a modified stochastic diffusion particle tracking model (MSDPTM) that incorporates energy cascade theory to more accurately simulate suspended sediment transport. The impact of turbulent eddies on sediment particles is an intermittent process, which is also considered in this study. The study examines the time correlation between eddies using eddy turnover time and finds that closer-scale eddies exhibit higher correlations than those farther apart. The statistical properties of particle movement, such as the ensemble mean and variance of particle trajectories, have been calculated and compared with the stochastic diffusion particle tracking model (SDPTM) results. Notably, MSDPTM with intermittency demonstrates a significantly larger ensemble mean of particle trajectories in the streamwise direction than other particle tracking models. The proposed model is validated through comparison with available data, showing its enhanced performance. The results of the simulation indicate that MSDPTM outperforms SDPTM, especially when the intermittency effect of eddies is considered. [ABSTRACT FROM AUTHOR]

Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism of the microbial community were studied. The results indicated that the total phosphorus (TP) content increased from 678.875 to 1019.133 mg/kg and from 1126.017 to 1280.679 mg/kg in sediments and suspended solids (SSs) during the sediment resuspension process, respectively. Organic P (OP) increased by 127.344 mg/kg and 302.448 mg/kg in sediments and SSs after the disturbance, respectively. The microbial communities in the sediments and the leaves of V. natans had higher Chao values after the disturbance, while Shannon values decreased after the disturbance compared to the control in SSs. Proteobacteria had the highest abundance with the value of 51.1% after the disturbance in the sediments and SSs, and the abundance values of Proteobacteria in rhizomes and leaves of V. natans could reach 73.2% on average. Chloroflexi, Acidobacteria, and Firmicutes were also the main phyla in the sediment resuspension system. Sodium hydroxide extractable P (NaOH-P) in sediments could reduce the bioavailability of this P fraction under disturbance conditions. The decrease in the abundance of Bacteroidetes and Nitrospirae indicated that they were more sensitive to the disturbance, and the rotational speed changed the survival conditions for the Bacteroidetes and Nitrospirae. The response mechanism of microbial community during the sediment resuspension process could reflect the influence of the microbial community on the changing characteristics of P and could provide a theoretical foundation for P control at the micro level. [ABSTRACT FROM AUTHOR]

Water-sediment flow patterns can greatly contribute to the operational efficiency and safety of the pumping station. Among them, the vortex flow patterns have frequently caused sediment deposition in the forebay of forward pumping stations in a sediment-laden river. The forebay of the pumping station is also characterized by a complex two-phase flow structure with water and sediment. It is still lacking in the impact of pump start-up combinations on the flow pattern and suspended sediment movement. In this study, the mixture multiphase flow and the Realizable k-ε turbulence model were utilized from an engineering perspective. Grid evaluation criteria were selected as the hydraulic loss of water sediment flowing through the forebay and the operational efficiency of the pump. The inlet of the diversion channel was set as a mixed velocity inflow boundary, while the pump outlet was designated as a free outflow boundary. Solid boundaries were treated using the wall function. The free boundary of the water surface was handled with the assumption of a free-sliding rigid cover. A mathematical model was then established for the forebay of the pump station. The flow and sediment movement were simulated under different start-up combinations. The characteristics and formation mechanisms of each vortex region were analyzed to predict the sediment deposition in the forebay. An optimal start-up combination was proposed to alter the flow field structure. The hydrodynamic dredging was achieved for the large sediment deposits within the forebay. The velocity and sediment deposition within the forebay were measured using the Acoustic Doppler Current Profilers velocity profiler. These measurements were also used to validate the numerical simulation. The results show that a "plane sudden expansion vortex" was formed in the water-sediment two-phase flow from the diversion channel to the inlet of the forebay, due to the separation of the boundary layer. The vortex depth was about 90% of the water depth. A "near bottom three-dimensional vortex" in the intake pond was formed, influenced by the sudden increase of local water depth and the plane vortex. The vortex depth was about 93% of the water depth. The suspended sediment migrated to both sides of the forebay wall under the action of the vortex, where the "fanshape" sediment deposition was observed. The total sediment deposition accounted for about 60% of the total volume of the forebay. At the same time, the sediment content at the bottom of the intake pond was 8 to 9 times higher than that of the diversion canal. While the sediment content in the middle area was basically the same as that of the diversion canal. A total of five start-up combinations were proposed, including imported full open type, imported half-open type, intermediate focusing type start-up pump, two side decentralized type start-up pump, and fully open type pump. The comprehensive comparison showed that the flow pattern was significantly improved in the forebay after 91 days of operation of the pump station. Specifically, the flow velocity uniformity at the pump port of intermediate focusing type case 5 increased by 5.84%, whereas, the drift angle, the area of high sediment concentration area, and the sediment deposition decreased by 3.35%, 75%, and 58.60%, respectively. The findings can provide theoretical support to mitigate the harmful effects of vortex areas and sediment deposition in the forebay, thereby optimizing the operation of the pumping station. In addition, future research should consider optimizing and improving many more factors, including the separated forebay, in order to further optimize the sediment deposition and operation efficiency in the forebay of the pump station. [ABSTRACT FROM AUTHOR]

In the Tsitsa River catchment of the Eastern Cape Province, South Africa, concerns regarding the sedimentation of a proposed large, multipurpose, in-channel water storage scheme prompted investigations of sub-catchment suspended sediment loads and yields. Confluence-based fingerprinting and source apportionment was undertaken to explore whether this simple approach could identify relative sub-catchment contributions to downstream sediment loads, supplementing modelling and direct sampling. In November 2018, fine sediment sequestered in bed substrates was sampled above and below confluences, using a resuspension technique. The < 63 µm sample fraction underwent analysis of mineral magnetic properties, gamma emitting radionuclide activities and geochemistry to identify suitable tracers. Conservatism and range tests were used to select different combinations of composite fingerprints at seven confluences. Bivariate source apportionment using an unmixing model showed that the approach could be used as a preliminary means of determining relative sub-catchment sediment contributions. Catchment characteristics such as geology and land cover, as well as land tenure and management, were considered as explanatory factors for the difference in sediment contributions. The results for most sub-catchments were broadly similar to those from other studies. Shortcomings of this approach included the reliance on a single sampling effort, and uncertainty associated with sub-catchment sediment transport and residence times. [ABSTRACT FROM AUTHOR]

The present study discusses flood hazard characteristics in the lower reaches of the West Rapti River based on the results obtained from field surveys and numerical computations using depth averaged 2-D numerical models for flood flow and associated sediment transportation. To evaluate the inundation process with sediment erosion and deposition in the floodplain, a new erosion term was introduced into the mass conservation equations for suspended sediment and bed sediment. The results obtained from numerical computations indicated that field data on the spatial distributions of depths for inundation, and sediment erosion and deposition can be evaluated by the numerical model. Thus, numerical predictions were performed for the inundated areas, and the accumulated volumes of sediment erosion/deposition for floods with return periods of 50, 100, and 200 years, as a step towards damage assessment and risk assessment due to floods with active sediment transportation in the floodplains. [ABSTRACT FROM AUTHOR]

Acoustic backscatter data were collected in the shallow nearshore environment under breaking and non‐breaking waves, using a multi‐frequency sonar at 0.5, 1.0, and 2.0 MHz. The data are used to develop and test an acoustic inverse model for measuring suspended sediment concentration (SSC) in the presence of bubbles generated by breaking waves. The model leverages the contrasting frequency dependence of acoustic scattering by bubbles and sand, to simultaneously estimate SSC and bubble void fraction. Validation against in situ sediment measurements shows the acoustic technique can recover sediment concentration with good accuracy in both breaking and non‐breaking waves, unlike existing algorithms which only perform well in non‐breaking waves. Finally, data from the experiment are used to validate existing theories for suspended sediment dynamics under breaking waves, for which few previous data sets exist. Plain Language Summary: The surfzone is the energetic region of the coast where waves break, causing strong currents, mixing, and sediment transport. An understanding of fundamental sediment transport processes in the surfzone is essential to coastal engineering applications, for example, mitigating coastal erosion and flooding. However, theories for nearshore sediment transport suffer from a lack of direct field validation, owing to inadequate measurement techniques. The measurement challenges are many, including the need to detect sediment concentrations within centimeters of a moving seabed. Here, we introduce and validate a multi‐frequency sonar technique capable of obtaining the necessary measurements, including in bubbly flow under breaking waves where field data are arguably most critical. The method is validated with field data collected at Duck, NC. Results from the experiment are used to test existing theories for the vertical distribution of suspended sediment. The data show wave breaking has a strong influence on sediment vertical mixing, with implications for sediment transport predictions. Key Points: Novel observations of mobile sediment in the energetic nearshore zoneNew acoustic remote sensing technique for detecting sediments under breaking wavesField validation of models for near‐bed sediment concentration and vertical mixing, in breaking and non‐breaking waves [ABSTRACT FROM AUTHOR]

This study assesses the settling dynamics of suspended sediments along the hyper‐turbid Gironde Garonne fluvial‐estuarine system, with an innovative optical SCAF instrument (System of Characterization of Aggregates and Flocs). Two fields campaigns were carried out to determine the settling velocity and properties of suspended sediments during a semi‐diurnal tidal cycle, as well as hydrodynamic conditions and water properties. The two sampling stations were representative of two regions: a tidal river dominated by fresh water and an estuary affected by salty or brackish waters. A high spatial variability of the settling velocity was observed along the fluvial‐estuarine system and vertically along the water column. Settling velocities ranged from 0.02 to 0.4 mm/s. This study confirms that in hyper‐turbid systems, the suspended sediment concentration (SSC) is predominantly driving the settling dynamics of suspended sediment. Threshold concentrations have been defined for the flocculation and hindered regimes where the settling velocity may vary by one order of magnitude. Although in natural environments it is difficult to distinguish between the effects of SSC and turbulence (as they are correlated), in the Gironde‐Garonne system the turbulent shear G seems to affect the settling of suspended sediment to a lower extent. Settling velocity variations cannot be directly correlated to salinity or organic matter content. Despite differences in hydrodynamic and environmental conditions in fluvial and estuarine regions, a common prediction law has been found to estimate settling velocity of suspended sediment as a function of suspended sediment concentration. Plain Language Summary: Estuaries and rivers are biotically rich environments strongly impacted by human activities. Mud trapping capacity of such systems has a major influence on water quality by reducing light availability, promoting oxygen depletion and by trapping adsorbed contaminants, bacteria and nutrients. A key dynamical parameter impacting the trapping of mud is the sediment settling velocity. Sediment settling is influenced by a wide range of environmental factors such as salinity, sediment concentration, turbulence of the flow and organic matter. This manuscript presents sediment settling data from field surveys carried out along the Garonne River—Gironde Estuary system (France), where large quantities of mud are trapped during the dry season. It highlights the driving role of sediment concentration on the settling dynamics along the entire system, despite the hydrodynamics and water properties of riverine waters differing from the estuarine waters. The turbulence of the flow appeared to be of secondary importance. An unique empirical prediction law has been established for the whole system contrary to other systems around the world. An improved understanding of sediment fluxes contributes to effective waterways management and the preservation of essential ecological environments. Key Points: In such hyper‐turbid system, the suspended sediment concentration predominantly drives the settling dynamics of suspended sedimentThe turbulent shear appeared to be a control parameter of secondary importanceA common prediction law can be found for the whole system [ABSTRACT FROM AUTHOR]

The prediction of sediment concentrations is of significant importance for watershed sediment control, water-sediment regulation, as well as water quality and environmental management. The upper reaches of the Yangtze River, vast area in size and abundant in tributaries with complex water and sediment sources, pose a great challenge to accurately predict the process of suspended sediment concentration (SSC) entering the Three Gorges Reservoir. In this study, we propose a deep learning model named RF-LSTM, which combines Random Forest (RF) algorithm and Long Short-Term Memory (LSTM) neural network for daily SSC prediction at Cuntan station. This model addresses the varying impacts of rainfall in the upper reaches of the Yangtze River, as well as the inflow of water and sediment from its main stream and tributaries, on the daily SSC observed at the station. Firstly, the RF algorithm is employed to identify water and sediment factors that exhibit a strong correlation with the SSC at Cuntan. These factors are then utilized as input variables for the LSTM neural network to discern the mapping relationship between the optimized set of factors and the SSC at Cuntan. Finally, the model is applied in the region spanning from Xiangjiaba to Cuntan of the upper Yangtze River to predict the daily SSC during flood season at Cuntan station under different forecast periods. Results show that, compared to the LSTM model, the RF-LSTM model can better account for the lagged effects of the predictor factors on the SSC, and effectively capture the features that are strongly correlated with the SSC at Cuntan station. Under all the four different forecast horizons considered, the RF-LSTM exhibits superior performance in terms of both prediction accuracy and overall capability. Specially, when considering no-forecast and 1-d forecast horizons, both models exhibit high prediction accuracy, with Nash-Sutcliffe efficiency coefficients exceeding 0.82 during the validation period. Notably, the RF-LSTM model achieves a Nash-Sutcliffe efficiency coefficient of 0.91 in the no-forecast horizon, outperforming the LSTM model by reducing mean absolute errors and root mean square errors by 8% and 13%, respectively. Furthermore, under both of these forecast horizons, the RF-LSTM model more precisely captures SSC peaks and their occurrence timings. However, as the forecast horizon increases to 2 days and 3 days, the accuracy of both models decrease significantly. Nevertheless, the RF-LSTM model continues to outperform the LSTM model in terms of computational accuracy, demonstrating its robustness and reliability across different forecast horizons. These findings highlight the potential of the RF-LSTM model as a valuable tool for SSC prediction in the upper reaches of the Yangtze River, offering a valuable reference for future studies in this domain. [ABSTRACT FROM AUTHOR]

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Water column removal in streams is a nitrogen (N) cycling pathway that has been historically overlooked. Studies filling this knowledge gap have focused on the role of water column N removal in mid‐to‐large‐order rivers with consistently high suspended sediment concentrations. However, smaller streams may provide comparable suspended sediment concentrations during and after storm events, creating favorable conditions for water column N removal. To assess the presence, magnitude, and control of water column N removal during storms in low‐order watersheds, we measured water column denitrification and heterotrophic assimilatory N uptake rates at three locations in a Mid‐Atlantic watershed during five storm events of different magnitude, sediment loads, and nutrient availability. We found large variations in water column denitrification (0–5.56 mg N g−1 d−1) and assimilatory uptake (0.003–1.67 mg N g−1 d−1). Higher rates of N removal occurred during flow recession, with a correlation between suspended sediment organic matter content and denitrification. On average, denitrification rates in the water column were higher when flashy responses to storm events occurred. In contrast to denitrification, water column N removal rates (as both denitrification and heterotrophic assimilation) during storm events were comparable to those measured at baseflow in larger rivers. However, water column denitrification could only account for less than 10% of potential reach‐scale N removal during most of the storm events. Our findings provide insight into the ecological relevance of small stream water columns and suggest that more research is needed to understand the magnitude of stream water column processing on watershed‐scale N removal. Plain Language Summary: In freshwater ecosystems, microorganisms facilitate the transfer of nutrients from the surrounding environment to other organisms. Through a process known as nitrogen removal, microbes capture and modify nitrogen—an essential element for life—into forms that other organisms can use. In streams, microbes that perform nitrogen removal can live on the streambed, or on the surface of small sediment particles suspended in the water column. During storms, the amount of suspended particles in a stream increases dramatically, potentially providing more surface area where nitrogen removal can occur. Our study measured how much nitrogen removal takes place in the water column of streams during storms. We also determined whether other environmental factors influence the rates of removal. We found that higher rates of nitrogen removal occur after the peak of a storm, when the stream water level is decreasing. Additionally, we found that the rate of nitrogen removal increases with the amount of organic matter present in the suspended sediment. Overall, the rates of uptake we measured were comparable to those observed in much larger rivers, suggesting that nitrogen uptake in the water column during storms may be an important but overlooked component of the nitrogen cycle in small streams. Key Points: More flashy storms showed higher rates of water column denitrificationWater column removal rates were higher during flow recession than during rising flowsDenitrification was positively related to organic matter content in suspended sediment, whereas N uptake decreased with suspended chlorophyll [ABSTRACT FROM AUTHOR]