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Knowing the amount of sediment transported in rivers is important in river and hydraulic engineering. In essence, sediment transport process is very complex, whose direct measurement is not only challenging but also costly. In this regard, several equations have been developed to estimate sediment discharge, while their estimations may be an order of magnitudes different from one another under specific circumstances. In a bid to improve the estimation of sediment transport, this study proposed a new data-driven equation based on 543 reliable field measurements at 25 rivers using the Modified honey bee mating optimization (MHBMO) algorithm. The data include mean flow velocity, water surface slope, mean flow depth, median particle size, water surface width, suspended load, and bed load measured in the field. The performance of the new equation was compared to those of Yang, Engelund and Hansen, Shen and Hung, and Ackers and White using 6 metrics. Moreover, another nature-inspired optimization algorithm, i.e., genetic algorithm (GA) was employed to enhance the comparison. Based on the results, the MHBMO-based equation outperformed other estimation models and served as the best method in the ranking analysis. For instance, it improves the determination coefficient of Yang's equation, which is one of the widely-used equations recommended by the United States Bureau of Reclamation by 15.2%. Despite being ranked the second, the GA-based equation was only marginally less precise than the MHBMO-based model. Furthermore, the sensitivity analysis indicates that the sediment load is mostly sensitive to mean flow depth. Finally, it is postulated that applications of nature-inspired algorithms can help to improve the estimation of sediment transport. [ABSTRACT FROM AUTHOR]

Estimation of total sediment loads is a significant topic in river management as direct measurement is costly and time-consuming. This study aims not only to use the eXtreme Gradient Boosting (XGBoost) model but also to compare its performance with that of other empirical equations and ML models, including Artificial Neural Networks (ANN), AdaBoost, Gradient Boost Regressor, Random Forest Regressor, and Gaussian Process. 543 data points from the United States Geological Survey were used to train and test different models. The results showed that XGBoost outperformed other methods considering six performance metrics. To be more specific, the root mean square errors and determination coefficient were 216 and 0.95, respectively, whereas the corresponding metrics for ANN were 316.23 and 0.87, respectively. To interpret the sediment predictions and delineate the importance of each feature, XGBoost feature importance and SHapley Additive exPlanations (SHAP) were utilized. According to the feature importance analysis, estimations of the XGBoost model was mostly (72%) affected by the water surface width. Moreover, SHAP analysis verified the importance of water surface width on the final predictions. Finally, based on the results achieved in this study, further applications of XGBoost in water resources management are postulated. [ABSTRACT FROM AUTHOR]

Total sediment load exerts control over the river channel morphology. Due to the non-linear and multi-dimensional behavior of the variables impacting total sediment load, the prediction is often complex and challenging. To handle this non-linearity and multi-dimensional behavior of total sediment load variables, various approaches like empirical equations, data mining techniques, genetic algorithms, and machine learning (ML) methods have been proposed in the literature. This study provides a substantially better prediction of total sediment load using various methods i.e., linear regression (LR), support vector regression (SVR), extreme learning machine (ELM), and deep neural network (DNN). To evaluate the models, several performance metrics have been used i.e., index of agreement ( I d ), Pearson correlation coefficient (PCC), mean square error (MSE), Nash-Sutcliffe efficiency (NSE), root mean square error (RMSE), R 2 , and discrepancy ratio (D r ). Results show that, the proposed DNN method predicted the total sediment load with significant accuracy and had the highest prediction accuracy (I d = 0.989, PCC = 0.979, MSE = 0.042, NSE = 0.958, RMSE = 0.204, R 2 = 0.959, D r = 91.91%, respectively) followed by ELM, SVR, and LR. However, the performance of other proposed methods has been satisfactory when compared with the existing techniques. The proposed methods are compared with various well-known empirical equations available in the literature. [ABSTRACT FROM AUTHOR]

The study is to evaluate the total sediment transport (suspended and bed load) in a Mediterranean river (Bellah, Tipaza, Algeria). To understand this study, we based our analysis on hydrometric data related to the instantaneous discharge and to the concentration of suspended sediment, over a period of 33 years (from 1974/75 to 2006/07). The results show that a good correlation between the suspended sediments and water discharge. The exponent b of our model is equal to 1.38, a value close to those found by researchers who worked in semi-arid region. The suspended sediment transport is about 610 t km-2 year-1. This value is comparable to those found in other regions with similar hydrologic regimes. The bed load is about 170 t km-2 year-1 for τ0 = γ × I × Rh t km-2 year-1 and it is about 115 t km-2 year-1 for τ0 = 0.7×γ × I × Rh. The total sediment transport is estimated at 725 t km-2 year-1 if we take into account the corrective coefficient of roughness in the bed of the wadi and equal to 780 t km-2 year-1 in other direction. To better judge our results, we compared them with those obtained by the relationship Tixeront which remains the most used for estimating the specific degradation in the basins of the Maghreb. The value obtained by the relation of Tixeront is slightly below our own values, but it is permissible to say that the results are of the same order of magnitude. This slight difference can be explained by the introduction of the amount of sediments carried in the determination of the specific erosion of the watershed rates. [ABSTRACT FROM AUTHOR]

The Tigris River in Baghdad is a large sand-bed river, supply-limited because of the implementation of a water flow regulation scheme comprising a series of reservoirs and barrages. The significant reduction in the water discharge has affected the hydraulic performance of the river and turned it into an under-fit river of complicated morphology where many islands and bank deposits have been showed up across an 18 km reach in addition to the essential sinuosity. Measuring sediment load at individual cross-sections in the river gives misleading estimates and the corresponding sediment rating curve has a locally limited using. A spatially sediment rating by investigating sediment loads over the complicated reach is required to overcome the local limitations. Sediment transport rates have been investigated at 16 cross-sections along the study reach by collecting suspended load, bed load and bed material samples. Velocity profiles were measured at the sampling stations using an Acoustic Doppler Current Profiler (ADCP). The measurement results indicated that the suspended load is the dominant mode of transport (93.5%). However, bedloads were considered in determining the total loads. A spatial total load rating curve in the form of a power function was established and examined against the sediment measurements. Twenty-two previously published total load formulae where applied at the same sections and of these the Colby1964 formula gave the closest fit to the measured loads. Based on the results from this study a recommended procedure is established for using a spatial total load rating curve to estimate sediment transport rates for similar morphologically complicated rivers. Average annual transport rates during the period 2009–13 was estimated at 3.21 million tons. [ABSTRACT FROM AUTHOR]

The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of topographic data from 1950 to 2015, this paper studied the erosion-deposition pattern of the entire Yangtze Estuary. An alternation between erosion and deposition was found during the past 65 years, which was in correspondence to the alternation between flood and dry periods identified by multi-year average duration days of high-level water flow (defined as discharge ≥ 60,000 m3/s, namely, D≥60,000) from the Yangtze River Basin. A quantitative relationship was further developed between the erosional/depositional rate of the Yangtze Estuary and the interpreting variables of yearly water discharge, D≥60,000 and yearly river sediment load, with contributing rates of 1%, 59% and 40%, respectively. Mechanism behind the alternate erosion and deposition pattern was analyzed by examining residual water surface slope and the corresponding capacity of sediment transport in flood and dry periods. In flood periods, a larger discharge results in steeper slope of residual water level which permits a greater capacity of sediment transport. Therefore, more bed materials can be washed to the sea, leading to erosion of the estuary. In contrast, flatter slope of residual water level occurs in dry periods, and deposition dominates the estuarine area due to the decreased capacity of sediment transport and the increased backwater effect of flood-tide. Coastal dynamics and estuarine engineering projects alter the local morphological changes, but slightly affect the total erosional/depositional rate of the whole estuarine region. Heavy sedimentation within the Yangtze Estuary after the impoundment of the Three Gorges Dam can be attributed to the reduced occurrence frequency of flood years due to water regulation by the dam, and largely (at least 36%–52%) sourced from the sea. Deposition is still possible to occur in the Yangtze Estuary in the future, because the multi-year average D≥60,000 is unlikely to exceed the critical value of 14 days/yr which corresponds to the future equilibrium state of the Yangtze Estuary, under the water regulation of the large cascade dams in the upper Yangtze. Nevertheless, the mean depositional rate will not surpass the peak value of the past years, since the total sediment load entering the Yangtze Estuary has presented a decreasing trend. [ABSTRACT FROM AUTHOR]

Abstract It is important to examine the ratio of measured to total sediment discharge to determine the error in measured sediment transport rates from depth-integrated samplers. The ratio of measured to total sediment discharge as well as the ratio of suspended to total sediment discharge are examined based on the Modified Einstein Procedure. Both ratios reduce to a function of the ratio of shear velocity, u * , to the fall velocity, ω , of suspended material, u * / ω , and the ratio, h / d s , of flow depth, h , to the median grain size of bed material, d 50. In rivers transporting fine material (such as silt or clay), the ratio of suspended to total load is a function of the ratio, h / d 50 . In this study, it is found that the ratio of measured to total load becomes a simple function of flow depth. For fine sediment transport, with a Rouse number (Ro) < 0.3 , at least 80% of sediment load is in suspension when h / d 50 > 15 , and at least 90% of sediment load is measured from depth integrating samples when h > 1 m. Detailed measurements from 35 river stations in South Korea demonstrate that sand sizes and finer fractions predominantly are transported in suspension. Also, at least 90% of sand and finer fractions are transported in suspension in gravel and sand bed rivers when the discharge is larger than the mean annual discharge. [ABSTRACT FROM AUTHOR]

This study examined the river sediment transport characteristics of the Ping River basin, which is one of the major river basins in Thailand. River surveys of the Ping River were carried out nine times between 2011 and 2013. Survey data included river cross sections, flow velocities, suspended sediment concentration, and bed load transport in the river. Analyzes of these data indicated that suspended transport rates in the Ping River during normal flow conditions in 2012-2013 ranged between 107 and 9,562 metric tons/day (mt/d), but increased to 35,300 mt/d during high flooding conditions (Thailand's Great Flood of 2011). The rate of bed load transport was 1,401 mt/d during the Flood of 2011. However, the measured bed load in 2012-2013 varied between 0 and 482 mt/d. The bed-to-suspended load ratio in the Ping River fluctuated in the broad range of 0-2.0. Estimates of total sediment transport in the Ping River were made using some of the classic equations from the hydrologic literature. The results obtained from the different methods show that the Laursen-Copeland formula gives the best estimate of total sediment transport rate of the Ping River compared to other methods. Results from this study also reveal that the Bhumibol Dam, constructed in 1964, has had a significant effect on suspended sediment load reduction downstream of the dam. [ABSTRACT FROM AUTHOR]

A new numerical model for predicting the total sediment load in the river is presented. The model is comprised of two parts, namely flow and sediment transport parts. The flow analysis is carried out using the lateral distribution method, which distributes the flow and sediment load across the width, based on channel geometry and flow dynamics. To obtain the total sediment load, the bedload and suspended load are predicted separately. Conventional formulas are used for the bedload, and Rousean distribution with an entrainment function is used for the suspended load. Einstein partition is used to separate the form drag component from the total shear stress. The model is applied to the Danube River, a gravel-bed river in Slovakia and the Han River, a sand-bed river in Korea. Predicted distributions of sediment load in the lateral direction are given. The predicted results are compared with those obtained using the 1D approach as well as from measured data. Total sediment load rating curves are presented and the mixture effect of bed-materials is discussed. [ABSTRACT FROM AUTHOR]

Point velocity and suspended sediment concentration measurements are used to calculate the total sediment discharge in sand-bed rivers. Calculations with the Series Expansion of the Modified Einstein Point Procedure (SEMEPP) depend on grain diameter d s and settling velocity ω, flow depth h shear velocity u * , and sampling depth h p . This procedure extends the applicability of the Modified Einstein Procedure (MEP) by using point sediment concentration and velocity measurements. This procedure is tested using the laboratory data from Coleman, and field measurements from the Enoree, Middle Rio Grande and Mississippi Rivers. Based on 801 point measurements over 124 verticals at flow depths ranging from 0.17 m to 33.5 m and sediment concentrations less than 0.1 kg L −1 , the accuracy of the calculations depends on u * /ω and h p / d s . Point measurement techniques like SEMEPP are well-suited when u * /ω 5 where at least 60% of the total sediment load is measured when 90% of the flow depth is sampled. The determination of sediment discharge from point measurements is most accurate in deep rivers when h p / d s > 10,000, and u * /ω > 10. Point measurements are not well-suited for shallow rivers and laboratory flumes where h < 0.5 m and when u * /ω < 2. [ABSTRACT FROM AUTHOR]

A new method for numerically predicting the total sediment load in a river is proposed. The method can be used to predict the total sediment load with information on channel geometry and slope, flow, and bed materials. The conventional method uses a 1D approach that assumes the channel has a wide rectangular shape. However, the proposed method computes depth-averaged velocity over the width and predicts the total sediment load based on the flow computations. The new method, therefore, is expected to predict better if the flow changes significantly in the lateral direction. The proposed method was applied to three large sand-bed rivers in Korea, where information is available regarding suspended sediment. Five formulas were tested of use in making total sediment load computations, namely Engelund-Hansen's, Ackers-White's, Yang's, Brownlie's, and Karim's formulas. The predicted total sediment loads are compared not only with measured data but also with results calculated using the 1D approach. Discrepancy ratios between the predicted and measured total sediment loads are given and the results are discussed. [ABSTRACT FROM AUTHOR]

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