Search Results (62)

Time domain reflectometry (TDR) has been validated for monitoring water level evolution and riverbed scouring in the laboratory. Previous studies have also validated the feasibility of field-based single hydrological parameter monitoring using TDR. However, the current research focuses on developing separated TDR sensing systems, and integrated measurements of multiple hydrological parameters from a single reflected waveform have not been reported. This study presents an improved helical probe sensor specifically designed for implementation in geologically hard soils, together with an improved data interpreting methodology to simultaneously determine water surface level, bed elevation, and suspended sediment concentration from a single reflection signal. Experimental comparisons were conducted in the laboratory to evaluate the measuring performance between the traditional dual-needle probe and the novel spiral probe under the same scouring conditions. The experiments confirmed the reliability and superior performance of spiral probe in accurately capturing multiple hydrological parameters. The measurement errors for the spiral probe across multiple hydrological parameters were all within ±10%, and the accuracy further improved with increased probe embedding depth in the sand medium. Across all tested parameters, the spiral probe showed enhanced measurement precision with a particularly significant improvement in suspended sediment concentration detection. Full article

This study investigates the dynamic response mechanisms of discharge capacity in the Han River Estuary to hydrological process changes at the Yangtze–Han River confluence. By constructing a one-dimensional hydrodynamic model for the 265 km Xinglong–Hankou reach, we quantitatively decouple the synergistic effects of riverbed scouring (mean annual incision rate: 0.12 m) and Three Gorges Dam (TGD) operation through four orthogonal scenarios. Key findings reveal: (1) Riverbed incision dominates discharge variation (annual mean contribution >84%), enhancing flood conveyance efficiency with a peak flow increase of 21.3 m³/s during July–September; (2) TGD regulation exhibits spatiotemporal intermittency, contributing 25–36% during impoundment periods (September–October) by reducing Yangtze backwater effects; (3) Nonlinear interactions between drivers reconfigure flow paths—antagonism occurs at low confluence ratios (R < 0.15, e.g., Cd increases to 45 under TGD but decreases to 8 under incision), while synergy at high ratios (R > 0.25) reduces Hanchuan Station flow by 13.84 m³/s; (4) The 180–265 km confluence-proximal zone is identified as a sensitive area, where coupled drivers amplify water surface gradients to −1.41 × 10⁻³ m/km (2.3× upstream) and velocity increments to 0.0027 m/s. The proposed “Natural/Anthropogenic Dual-Stressor Framework” elucidates estuary discharge mechanisms under intensive human interference, providing critical insights for flood control and trans-basin water resource management in tide-free estuaries globally. Full article

The article investigates the development of local scour downstream of a damming structure, emphasizing the dynamic equilibrium of river morphology influenced by both natural processes and human interventions like the construction of weirs. It distinguishes between clear-water and live-bed conditions, discussing how sediment transport interacts with hydraulic forces to shape the riverbed. The introduction of a damming structure disrupts sediment flow and initiates local scour formation, which varies depending on stream conditions. In the experimental section, a physical model of a damming weir was tested under controlled conditions. The laboratory model was inspired by an existing damming weir on the Radomka River in Poland. Granulometric analysis and eleven flow series were conducted to assess scour evolution over time. The results showed the fastest erosion in the first hours, followed by stabilization in scour depth but continued elongation of the scour hole. The analysis identified four phases of scour development: initiation, intensive growth, stabilization, and equilibrium. Despite depth stabilization, scour length continued to increase, indicating that full equilibrium had not been reached. The study highlights the complexity of predicting scour behavior and recommends incorporating both depth and length evolution into design analyses to improve the resilience of such damming structures. The innovative aspect of the present study lies in the inclusion of coarse sediment transport, previously accumulated in the upstream reach due to the weir’s impoundment effect, into the scour development process. This specific effect has not been addressed in the studies cited by other authors. This research provides crucial insights for the sustainable design of hydraulic structures and effective sediment management strategies, contributing to the long-term stability and safety of riverine infrastructure. Full article

In response to the growing demand for improved operational efficiency in road and bridge networks, constructing parallel bridges in complex river sections has become a crucial strategy. This study focuses on a parallel bridge construction project in the Jinan section of the lower Yellow River, conducting physical model tests to investigate the unique aspects of the impacts of different pier shapes and spans on the flow characteristics of sediment-laden rivers under real-world engineering scenarios. The experimental results demonstrate that the hydraulic physical model of this river section that was constructed is reliable, with a relative error of <20% in sediment deposition, in the simulation of sediment erosion and deposition, flow velocity patterns, water levels, and riverbed morphological changes during parallel bridge construction in bridge-clustered river sections. The newly constructed bridges have a limited influence on the overall regime of this river section, with their impacts on both banks remaining within controllable limits, and the river flow remains largely stable. In areas with denser pier arrangements, the phenomenon of backwater upstream of the bridges is more pronounced, and under characteristic flood conditions, the newly built bridges amplify the water level differences between the upstream and downstream sections near the bridge sites. The ranges of influence of the water level drop downstream of the bridges increase, particularly in the main flow areas. Flow velocities generally increase in the main channel, while significant fluctuations are observed in the floodplain areas. Flood process experiments reveal that the slope at the junction between the main channel and the floodplain becomes gentler, with noticeable scouring occurring in the main channel. After flood events, the river tends to evolve toward a U-shaped channel, posing certain safety risks to the piers located at the junction of the floodplains and the main channel. This research methodology can serve as a reference for studying flow characteristics in similar parallel bridge construction projects in river sections, and the findings hold significant implications for practical engineering. Full article

To address the problem of concave bank scour in a 120° bend river, this study designed and explored the bank protection effect of different arrangements of semi-cylinder sandbags. Based on the actual riverbed structure, a simplified geometric model of the bend riverbed was constructed, and the bank protection effect of sandbags arranged at different angles and spacings under different flow conditions was evaluated by using a multi-objective genetic algorithm (MOGA). The optimization results showed that the net sediment mass flow rate of the riverbed in the curved riverbed model using one semi-cylinder sandbag was maximum when the angle between the semi-cylinder sandbag and the concave bank of the riverbed was 158°. Further, the results of the analyses of velocity and spacing indicated that the effect of inlet flow velocity on the effectiveness of bank protection is 1.5 times greater than the spacing of the throw pillows in a bend channel with two semi-cylindrical sandbags. In the conventional flow velocity range of 1~2 m/s, the net sediment mass flow rate in the riverbed is the largest when the throw pillow distance is set at 49 m, which is about 9.4 kg/s, which can provide a better bank protection effect and can provide a certain reference for the design of engineering bank protection. Full article

As the largest inland river in China, the Tarim River’s flood events significantly influence its riverbed formation. This paper took the Alar to Xinquman section of the Tarim River as the study area. The study area’s digital elevation model of the river was constructed using historical Google images and Copernicus DEM 30. Six different flood events were selected, corresponding to flood events with varying sediment loads, flood volumes, and peak flow volumes. The MIKE 21 software was used to simulate and investigate the response of the riverbed shape to different flood events. The experimental findings indicate that the sand content constitutes a pivotal factor in the formation of the riverbed during flood events. Flood sediment load goes through stages linked to changes in riverbed erosion and deposition. The combination of high peak flow and bed-forming flow after the peak effectively shapes the central channel’s morphology. The fourth type of flood event had the highest sediment transport coefficient Φ among the six types of floods and caused the most significant scouring effect on the riverbed under low sediment load conditions. Full article

When rivers impinge on the steep bluffs of valley walls, dynamic changes stem from a combination of fluvial and mass wasting processes. This study identifies the geomorphic changes, drivers, and timing of a landslide adjacent to the Apalachicola River at Alum Bluff, the tallest natural geological exposure in Florida at ~40 m, comprising horizontal sediments of mixed lithology. We used hydrographic surveys from 1960 and 2010, two sets of LiDAR from 2007 and 2018, historical aerial, drone, and ground photography, and satellite imagery to interpret changes at this bluff and river bottom. Evidence of slope failure includes a recessed upper section with concave scarps and debris fans in the lower section with subaqueous features including two occlusions and a small island exposed from the channel bottom at lower water levels. Aerial photos and satellite images indicate that the failure occurred in at least two phases in early 2013 and 2015. The loss in volume in the 11-year interval, dominantly from the upper portion of the bluff, was ~72,750 m³ and was offset by gains of ~14,760 m³ at the lower portion of the bluff, suggesting that nearly 80% of the material traveled into the river, causing changes in riverbed morphology from the runout. Despite being along a cutbank and next to the scour pool of a large meandering river, this failure was not driven by floods and the associated lateral erosion, but instead by rainfall in noncohesive sediments at the upper portion of the bluff. This medium-magnitude landslide is now the second documented landslide in Florida. Full article

This study explores the transverse response of bridge piers in riverbeds under a multi-hazard scenario, involving seismic actions and scoured foundations. The combined impact of scour on foundations’ stability and on the dynamic stiffness of soil–foundation systems makes bridges more susceptible to earthquake damage. While previous research has extensively investigated this issue for bridges founded on piles, this work addresses the less explored but critical scenario of bridges on shallow foundations, typical of existing bridges. A comprehensive soil–foundation structure model is developed to be representative of the transverse response of multi-span and continuous girder bridges, and the effects of different scour scenarios and foundation embedment on the dynamic stiffness of the soil–foundation sub-systems are investigated through refined finite element models. Then, a parametric investigation is conducted to assess the effects of scour on the dynamic properties of the systems and, for some representative bridge prototypes, the seismic response at scoured and non-scoured conditions are compared considering real earthquakes. The research results demonstrate the significance of scour effects on the dynamic properties of the soil–foundation structure system and on the displacement demand of the bridge decks. Full article

Bridges positioned near riverbeds experience complex interactions between flow dynamics and structural geometry, significantly affecting hydrodynamic loading and stability. This study analyzes the effect of deck proximity to the bed on pressure distribution and hydrodynamic loading, including drag and lift forces. Experimental tests were conducted in a rectangular channel using a scaled bridge deck model, varying deck positions, flow conditions, and upstream–downstream water depth levels. To the best of the authors’ knowledge, for the first time, a comparative analysis of hydrodynamic loads on bridge decks was conducted using both rigid and deformable granular beds. Pressure distributions on the front, rear, and bottom faces of the deck were measured using transducers sensors. Our findings corroborate that changes in Reynolds number have minimal impact on the deck drag and lift coefficients, under identical submergence conditions, whereas both coefficients decrease with the Froude number for both bed types. More importantly, the analysis of experimental evidence unveiled some interesting aspects pertaining to the physics of the phenomenon, allowing us to provide the following, unprecedented results: (1) lift and drag coefficients significantly decrease with proximity, exhibiting much higher values than those reported in the literature for larger clearance; (2) under identical hydraulic conditions (both upstream and downstream of the deck), drag and lift coefficients are significantly amplified by the presence of rigid beds compared to granular beds; and (3) the scour evolution alters the effective deck proximity, resulting in time-dependent hydrodynamic loads acting on the deck. Full article

High-speed water flow conditions can cause erosion of the bedrock in engineering areas. Due to the lack of accurate evaluation of bedrock scour and erosion rates, there has been a consumption of manpower and resources without achieving satisfactory engineering outcomes. Therefore, studying the scouring and erosion effects of water flow on bedrock is of significant importance for maintaining the sustainable development and safety of engineering projects. Using the bedrock prototype from the Xiaonanhai site in the upper reaches of the Yangtze River, a model test device was developed to conduct anti-scour tests on the bedrock. The study quantitatively examined the basic physical properties, incipient erosion velocity, and erosion rates of different types of bedrock. The study found that the prototype bedrock under natural exposure, submerged immersion, and alternating wet and dry conditions showed a trend of decreased tensile strength, with the alternating wet and dry conditions being the most detrimental to maintaining the physical properties of the rock mass. The anti-scour velocity of silty claystone and clayey siltstone samples increased with the increase in tensile strength, and the erosion rate increased with the increase in shear stress. If the shear stress is kept constant, the erosion rate decreases with the increase in tensile strength. The erosion rate is inversely proportional to the ratio of the bedrock’s tensile strength to the riverbed shear stress, with the fitting relationship showing a piecewise linear distribution. The research results can provide guidance for the safe production of engineering involving bedrock erosion in engineering reservoir areas that are conducive to sustainable development. Full article

Currently, there are two primary issues with CFD simulations of local scour around bridge foundations using the RANS method. Firstly, the self-sustaining characteristics of turbulent boundary conditions at the inlet require special attention. Secondly, the simulated location of the maximum scour depth does not align with experimental observations. This paper employs the RANS method to model the hydrodynamic characteristics surrounding bridge piers. The sediment transport model and sediment-sliding model, considering any slope of the riverbed, were adopted to simulate the spatiotemporal evolution of local scour around the bridge foundation. Building on traditional methods and assuming local turbulence equilibrium, a self-sustaining model is theoretically derived. This model swiftly develops a balanced turbulent boundary layer, achieving a horizontally uniform flow field and effectively maintaining consistency between the inlet-given turbulent profile and physical reality. Additionally, by incorporating the velocity component of the downward-flow in front of the pier and the average shear stress around the pier into the excess shear stress model, the refined wall shear stress model accurately estimates the scouring contributions of the downward-flow and the horseshoe vortex system in this region. The numerical results including the maximum scour depth, location, and scour pit shape are consistent with experimental findings. The findings demonstrate that the numerical approach proposed in this study effectively addresses the issue of inadequate estimation of turbulent characteristics in scour pit at the leading edge of bridge piers using the RANS method. This method offers novel insights and approaches for addressing local scour issues in bridges and offshore wind turbines, as well as vortex-induced vibration issues in submarine pipelines. Full article

Being tidal-sensitive, the river channel in the Longjin Yangqi area of Cangshan, Fuzhou City, is challenged further because of rapid urbanization. Thus, resultant remediation efforts are crucial. This study aims analyzes hydrodynamic characteristics of the area and, secondly, proposes an ecological dispatch solution with evaluation of its effectiveness through the Storm Water Management Model (SWMM). The chief tasks cover imitating rainfall runoff, optimizing sluice gate activities, reorganizing pump management, and reshaping river morphology to bolster flood control and water quality. Improvements were shown through ecological dispatch strategies, which suggested increasing the channel width for the river and deepening the riverbed, thereby increasing the flood duration, lowering water levels, and less frequent flood occurrences. Optimizing sluice gate settings improved efficiency in the regulation of water flow and reduced scour or siltation problems. Various adjustments to pumping operations scattered over various times were based on live-data analysis, therefore enhancing water flow and the self-purification capacity of the water body. The SWMM was directly applied in this tidal river for urban water resource management with data processing from over 100,000 points in simulations. Wherever needed, changes to model parameters were made to improve its capability and enhance its appropriate use in future urban settings. As a whole, this study presents a plan for sustainable water resource management paired with environmental conditions for the benefit of over 500,000 urban residents in the Longjin Yangqi area. Full article

Examining scouring around bridge piers is crucial for ensuring water-related infrastructure’s long-term safety and stability. Accurate forecasting models are essential for addressing scour, especially in complex water systems where traditional methods fall short. This study investigates the application of the HEC-RAS 2D sedimentation model, which has recently become available for detailed sediment analysis, to evaluate its effectiveness in predicting scoring around various pier shapes and under different water conditions. This study offers a comprehensive assessment of the model’s predictive capabilities by focusing on variables such as water velocity, shear stress, and riverbed changes. Particular attention was paid to the influence of factors like floating debris and different pier geometries on scour predictions. The results demonstrate that while the HEC-RAS 2D model generally provides accurate predictions for simpler pier shapes—achieving up to 85% precision—it shows varied performance for more complex designs and debris-influenced scenarios. Specifically, the model overpredicted scouring depths by approximately 20% for diamond-shaped piers and underpredicted by 15% for square piers in debris conditions. Elliptical piers, in contrast, experienced significantly less erosion, with scour depths up to 30% shallower compared to other shapes. This study highlights the novel application of the HEC-RAS 2D model in this context and underscores its strengths and limitations. Identified issues include difficulties in modeling water flow and debris-induced bottlenecks. This research points to the improved calibration of sediment movement parameters and the development of advanced computational techniques to enhance scour prediction accuracy in complex environments. This work contributes valuable insights for future research and practical applications in civil engineering, especially where traditional scour mitigation methods, such as apron coverings, are not feasible. Full article

Gas pipelines are buried and installed across rivers to supply the gas necessary for daily life. When crossing rivers, gas pipelines are typically installed on bridges; however, when installation on bridges is not feasible, the pipelines are buried in riverbeds. This study utilized both a one-dimensional model (HEC-RAS) and two-dimensional models (SMS) to simulate river flow and estimate the potential for scour and deposition around buried pipelines. The hydrodynamic simulations considered critical factors, including sediment transport, river discharge, and geological characteristics, to derive the maximum scour depth and assess the risk of pipeline exposure. The findings from the long-term and short-term simulations confirmed that riverbed changes due to natural hydrological events do not exceed the minimum burial depth standards, thereby ensuring pipeline safety. In addition, the study proposed specific reinforcement measures tailored to local site conditions, addressing concerns of continuous subsidence and ensuring long-term structural stability. This research offers important insights into pipeline risk management and contributes to the development of more effective regulatory standards for gas pipelines buried in riverbeds, enhancing both their safety and environmental sustainability Full article

The Rhine River is affected by major human interventions affecting its morphology and sediment regime, which have severely changed its flow and sediment transport. While channelization has increased the sediment transport capacity in the free-flowing sections, the sediment retention behind dams has caused a bedload deficit downstream and has additionally intensified riverbed erosion. The resulting consequences range from the exposure of less erodible sediment layers that pose obstacles for navigation, to the scouring of infrastructure, the lowering of groundwater levels, and multiple negative ecological consequences. To optimize the efficiency of countermeasures, a coherent overview of all sediment-related activities and the state of knowledge on the Rhine catchment is required. That is why the present study aims to give a catchment-wide overview in this regard, identify knowledge gaps and proposing a future research programme. The methodological approach includes a comprehensive literature review and online interviews with experts from six riparian countries working in the fields of sediment research and management. Based on our investigations, we have derived several research topics, each consisting of research questions. Three project ideas were defined that should primarily be realized: (i) the influence of climate change and land use change on the sediment regime; (ii) alteration and improvement of the sediment balance and continuity, sediment transport, and morphology; and (iii) national and bilateral projects on sediment transport processes and management. Full article