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Conventional methods of measuring water discharge and suspended sediment concentration (e.g., water sampling and moving acoustic Doppler current profiler [ADCP]) present challenges in large tidal rivers due to temporal and spatial constraints. This study introduces a novel approach to monitor water discharge and suspended sediment discharge (SSD) in large tidal rivers. Total water discharge and SSD exhibit notable variability in tidal rivers due to the river–tidal interactions; understanding this variability and its causes is essential for effective tidal river management. From June to November 2023, a field study was conducted at Nanjing (NJ) to continuously monitor water discharge, suspended sediment concentration (SSC), and SSD in the tidal reaches of the Yangtze River using coastal acoustic tomography (CAT). Total water discharge ranged from 8,765 to 43,356 m3/s, with a mean of 27,825 m3/s, while tidal discharge varied between −11,998 and 9,983 m3/s, with a mean of 69 m3/s. SSC ranged from 0.02 to 0.09 kg/m3, and SSD ranged from 110 to 3,823 kg/s. Tidal variations in SSC and SSD were within ±0.04 kg/m3 and −1,252 to 1,410 kg/s, respectively. Over short timescales, tides caused instantaneous fluctuations in velocity, water discharge, and SSD, with tides contributing −40% to instantaneous water discharge and SSD at NJ. Over seasonal timescales, no significant wet/dry variations were observed in water discharge, SSC, or SSD during a few months of 2023. Long‐term CAT application (e.g., decades) is required to reveal trends in tidal river dynamics. Plain Language Summary Due to temporal and spatial limitations, traditional methods for measuring suspended sediment concentration (SSC) and discharge, such as moving acoustic Doppler current profilers (ADCP), fail to directly measure transect variations in water discharge, SSC, and SSD in tidal reaches of the Yangtze River. This study developed a new method using coastal acoustic tomography (CAT). Two CAT systems were utilized to continuously measure water discharge, SSC, and SSD at the Nanjing Tidal Station. The CAT results were highly consistent with traditional methods, showing a correlation coefficient greater than 0.9. This study demonstrates the potential of CAT for continuous, real‐time monitoring of water discharge, SSC, and SSD in large tidal rivers. The results showed that mean water discharge, SSC, and SSD are primarily driven by river flow at Nanjing, while tides induce instantaneous variations in water discharge and sediment transport. Key Points Coastal acoustic tomography enabled water discharge and suspended sediment discharge (SSD) monitoring in Nanjing tidal reach of Yangtze River Total water discharge and SSD at Nanjing varied from 8,765 to 43,356 m3/s and 110–3,823 kg/s from June to November 2023, respectively Tides can directly trigger instantaneous variations in sediment discharge, while average sediment discharge is river‐dominated at Nanjing

Sediment rating curves (SRCs) are tools of satisfactory reliability in the attempt to describe the sediment regime in catchments with limited or poor-quality records. The study valorised the most suitable SRC development method for the estimation of the coarse suspended sediment load at the outlet of nine Mediterranean sub-watersheds. Four established grouping techniques were assessed, to minimize the uncertainty of the results, namely simple rating curve, different ratings for the dry and wet season of the year, hydrographic classification, and broken line interpolation, at three major Greek rivers (Aliakmon, Acheloos – upper route, Arachthos). The methods’ performance was benchmarked against sediment discharge field records, utilizing statistical measures and graphical analyses. The necessary observations were conducted by the Greek Public Power Corporation. The results were site/station dependent, and no methodology emerged as universally accepted. The analysis designated that the simple rating curve performs best at the cross-sections Moni Ilarion, Moni Prodromou, and Arta bridge, the different ratings for the dry and wet season of the year at Grevena bridge and Gogo bridge, the hydrographic classification at Velventos and Plaka bridge, and the broken line interpolation at Avlaki dam and Tsimovo bridge. In this regard, the study advocates the use of multiple SRC methods. Despite its limitations, the method merits a rather simple and cost-effective generation of a (continuous, detailed, sufficiently accurate) synthetic suspended sediment discharge timeseries, with high interpolating, extrapolating and reproducibility potential. The success of the application could benefit, among others, water quality restoration and dam management operations.

In history, the Yellow River has been suffering from endless floods, which has brought great damage or destruction to agriculture, cities, and people’s lives and property along the river. In this study, the rainfall and runoff characteristics of the Yellow River upstream (Tangnaihai and Lanzhou) after the vegetation restoration were analyzed. With the government implementation of ecological restoration policy since 1999, the vegetation cover in this area has been greatly improved and the normalized difference vegetation index (NDVI) shows a fluctuating increase, with the maximum value of 0.323 (in 2010) and the minimum value of 0.289 (in 2008). The trend of rainfall from 1948 to 2019 was increased, with an average increase of 1.747mm per 10 years. Before the implementation of ecological policy (1948 to 1999), the rainfall decreased by an average of 0.953mm per 10 years, and then increased by an average of 16.519mm per 10 years (2000 to 2019). From 1998 to 2017, the runoff increased by 11.13×10 8 m 3 per 10 years (Tangnaihai) and 30.517×10 8 m 3 (Lanzhou) per 10 years, which was due to the increase in rainfall. Annual sediment discharge and annual average sediment concentration decreased by 0.002×10 8 t and 0.103 kg/m 3 per 10 years in Tangnaihai, 0.081×10 8 t and 0.395kg/m 3 per 10 years in Lanzhou respectively. The decreasing intensity of Lanzhou station was greater. The sediment runoff modulus of Tangnaihai and Lanzhou decreased by 1.4875 km 2 ·year and 4.9439 km 2 ·year respectively. The increase of vegetation has a decreasing effect on sediment discharge. The implementation of ecological restoration policy reduces the amount of sediment into the Yellow River and plays an important role in the protection of ecological environment in the Yellow River Basin.

In Humboldt Bay, tectonic subsidence exacerbates sea-level rise (SLR). To build surface elevations and to keep pace with SLR, the sediment demand created by subsidence and SLR must be balanced by an adequate sediment supply. This study used an ensemble of plausible future scenarios to predict potential climate change impacts on suspended-sediment discharge (Qss) from fluvial sources. Streamflow was simulated using a deterministic water-balance model, and Qss was computed using statistical sediment-transport models. Changes relative to a baseline period (1981–2010) were used to assess climate impacts. For local basins that discharge directly to the bay, the ensemble means projected increases in Qss of 27% for the mid-century (2040–2069) and 58% for the end-of-century (2070–2099). For the Eel River, a regional sediment source that discharges sediment-laden plumes to the coastal margin, the ensemble means projected increases in Qss of 53% for the mid-century and 99% for the end-of-century. Climate projections of increased precipitation and streamflow produced amplified increases in the regional sediment supply that may partially or wholly mitigate sediment demand caused by the combined effects of subsidence and SLR. This finding has important implications for coastal resiliency. Coastal regions with an increasing sediment supply may be more resilient to SLR. In a broader context, an increasing sediment supply from fluvial sources has global relevance for communities threatened by SLR that are increasingly building resiliency to SLR using sediment-based solutions that include regional sediment management, beneficial reuse strategies, and marsh restoration.

This study discusses the coastal sediment budget for the Ishikawa coast using 12 years of observational datasets; it involves an understanding the local and regional sediment dynamics, the intensity of the transport processes in the region, and sediment supply from a local river. Although alongshore sediment transport and sediment budgets have been analyzed in previous studies, only a few conducted cross-shore sediment transport evaluations. The concentration of suspended sediments will be determined in this study, taking into account the influence of waves that are associated with the coastal current. The cross-shore sediment transport using sediment budget analysis indicated that the net alongshore sediment transport directions in the surf and offshore zones are opposite on the Ishikawa coast. The increase in the sediment budget of the surf zone can be attributed to the river sediment supply and longshore sediment transport inflow. Because of the significant outflow components of longshore and cross-shore sediment transports, the offshore zone budget showed a decreasing trend. A detailed sensitivity study was performed by varying the input parameters, in order to determine the possible ranges of net transport rates and sediment transport to the adjacent coasts. The results demonstrated the possibility of a clockwise residual sediment circulation. Our method can be used to analyze the alongshore sediment transport for other coasts and supplement future studies on coastal sedimentology and sediment budgets.

The study aims to evaluate the performance of four sediment rating curve development methods, namely (i) simple rating curve, (ii) different ratings for the dry and wet season of the year, (iii) different ratings for the rising and falling limb of the runoff hydrograph, and (iv) broken line interpolation that uses different exponents for two discharge classes at the outlet of the Venetikos River catchment, located at Western Macedonia, Northern Greece. The goal is to provide guidance on the selection of the most appropriate one for the estimation of sediment discharge (yield) at this gauging site (basin), as well as to properly assess such values. The necessary field measurements (discharge, sediment discharge, discharge–sediment discharge pairs) were conducted by the Greek Public Power Corporation. The performance of each method was evaluated by executing a statistical analysis (1965–1982), using as benchmark the observed mean monthly sediment discharge values. The broken line interpolation method performed best, not only by meeting the desired criteria of most statistical indicators used but also by being overall superior to all other methods. Thus, henceforward is to be treated as the representative rating curve development method for the specific site. Finally, an attempt was made to evaluate the estimated (and observed) sediment yield values against the ones attributed by four empirical equations, yet with relatively poor results.

Soil loss rate, suspended load, and suspended sediment discharge were simulated for the drainage basin of the Komarovka R., located at the territory of the former Primorskaya Water Balance, Russian Far East. The study was based on an open-code SWAT model. The model was calibrated and verified using archive measurement data on sediment load and suspended sediment discharge at PWBS by data of Tsentral’nyi hydrological gage (157 km 2 ). The simulation efficiency of the suspended load and suspended sediment discharge corresponds to categories satisfactory and higher. On the average for the drainage basin, the rate of soil washout is 11–12 t/ha per year. The washout rate is maximal in the period of active snow melting. The mean monthly value for April–May is 75 thous. t. The mean annual washout is 171 thous. t, and the maximal is 800 thous. t/year. The mean annual runoff of suspended sediments in the outlet section of the drainage basin is 2.6 thous. t. The highest monthly values of sediment runoff correspond to the period of summer floods in August, when with average of 1 thous. and maximum of 7.7 thous. t. The obtained data on the heterogeneity of the spatial distribution of the simulated values of washout rate are in good agreement with the landscape and climatic features of runoff formation in the drainage river basin. The major errors in the estimation of sediment load are due to the simulation quality of the hydrological regime and dynamics of runoff components that form flood hydrographs.

In this study, we used moderate resolution imaging spectroradiometer (MODIS) satellite images to quantify the sedimentation processes in a cascade of six hydropower dams along a 700-km transect in the Paranapanema River in Brazil. Turbidity field measurement acquired over 10 years were used to calibrate a turbidity retrieval algorithm based on MODIS surface reflectance products. An independent field dataset was used to validate the remote sensing estimates showing fine accuracy (RMSE of 9.5 NTU, r = 0.75, N = 138). By processing 13 years of MODIS images since 2000, we showed that satellite data can provide robust turbidity monitoring over the entire transect and can identify extreme sediment discharge events occurring on daily to annual scales. We retrieved the decrease in the water turbidity as a function of distance within each reservoir that is related to sedimentation processes. The remote sensing-retrieved turbidity decrease within the reservoirs ranged from 2 to 62% making possible to infer the reservoir type and operation (storage versus run-of-river reservoirs). The reduction in turbidity assessed from space presented a good relationship with conventional sediment trapping efficiency calculations, demonstrating the potential use of this technology for monitoring the intensity of sedimentation processes within reservoirs and at large scale.

The Yellow River Delta has undergone significant changes, developing a temperate chalk-sand silty coast with expansive and level tidal flats. However, the area is currently facing the threat of erosion due to coastal area construction, decreased river sediment discharge into the sea, and intensified marine hydrodynamic forces. Remote sensing technology has important applications in spatial and temporal monitoring of tidal flats. This study employs tidal data to establish the threshold range for the extraction of tidal flats in the Yellow River Qingshuigou sub-delta, using the water frequency method based on the image element proposed by previous authors. The study successfully identifies and analyzes the range of tidal flats, and further delves into their evolutionary process and underlying mechanisms. The study concludes that the area of tidal flats has shown a decreasing trend and was divided into a “rapid decline phase” and an “overall stabilization phase” with 2006 as the boundary. The spatial and temporal evolution of tidal flats is primarily influenced by three main factors: river sediment discharges, marine hydrodynamic forces, and anthropogenic reclamation activities. Specifically, the river sediment discharges and marine hydrodynamic forces impact the extent of tidal flats by modifying the boundary conditions, primarily at the sea boundary. Reclamation activities have a direct and rapid effect on the extent of tidal flats, primarily at the land boundary. In this study, we determined the contribution of three factors to the spatial and temporal evolution of tidal flats in different periods. During the two phases of the tidal flats’ spatial and temporal evolution in the Yellow River Qingshuigou sub-delta, the driving mechanisms were identified as “reclamation - marine hydrodynamic forces - river sediment discharges” and “marine hydrodynamic forces - river sediment discharges - reclamation”.

Estimating total sediment discharge is challenging. This study aims to assess performances of various data-driven models including empirical equations, machine learning (ML), and ensemble models for such estimations. The ML models include Support Vector Machine (SVM), Artificial Neural Network (ANN), K Nearest Neighbor (KNN), Random Forest (RF), and Decision Tree Regression (DTR). For this purpose, 543 widely-ranged data were collected from the United States Geological Survey (USGS) resources and used to train and test different models. Ranking different models demonstrated that Ackers and White's equation outperformed multiple linear regression (MLR) and SVM, which indicates that all ML models do not necessarily outperform empirical equations. Moreover, despite conducting multiple runs and parameter tuning, the results consistently indicated that increasing the number of hidden layers and neurons in ANN structures did not significantly improve the overall performance of the ANN models. In addition, the nonlinear ensemble model outperformed all methods and placed first in the ranking. Despite a notable difference between metrics obtained by KNN for the train and test data, it outperformed other methods and ranked second, while ANN achieved the third-best ranking place. The obtained result was also confirmed by the reliability analysis and confidence limits. However, due to negative predictions for some small sediment discharges by the nonlinear ensemble method, it did not demonstrate good reliability. Finally, the comparative analysis indicates that selecting a suitable model for estimating sediment discharges with a desirable accuracy is challenging, while further studies are required to assess other ML models or variants of ensemble models.