Spur Dike Research Articles

Scour Pit Characteristics and Safety Operation Index of Riprap Spur Dikes under Runoff and Tidal Current

The flow dynamics adjacent to spur dikes exhibit turbulence and complexity, often resulting in the formation of scouring pits in the riverbed nearby. In regions downstream characterized by robust riverbed mobility, the vulnerability of riprap spur dikes stems from the instability of the upper riprap induced by these scour pits. Current research on scour pits primarily focuses on singular runoff conditions, with a limited exploration into the formation and traits of these scour pits under the combined influence of runoff and tidal currents. This study delves into the formation process and features of scour pits adjacent to submerged riprap spur dikes shielded by flexible mattresses, considering the impact of both runoff and tidal forces, using flume model tests in the tidal zone of the lower Yangtze River as a reference. Our findings reveal that the scour pits at the forefront and rear of riprap spur dikes undergo cyclic scouring and silting influenced by the runoff and tide current’s duration and intensity. The maximum scour depth observed ranges from 60% to 90% of that during runoff alone, contingent upon the ratio of maximum flow velocity at flood tide and ebb tide (denoted as e). This law can be quantitatively elucidated through the concept of the average effect of flow on the riverbed scouring and silting in a unit time (denoted as E). A formula to calculate the maximum scour depth of riprap spur dikes under both runoff and tidal current scenarios, along with a slope formula describing the maximum scour depth relative to the spur dike toe are proposed in this study. These formulations offer versatility across varying flow conditions. Subsequently, we establish an evaluation index pertinent to the safety operation of spur dikes based on the latter formula. This research contributes to a more comprehensive understanding of scour pit dynamics adjacent to spur dikes, especially under combined runoff and tidal influences. The proposed formulae and evaluation index hold promise in enhancing the assessment and maintenance practices for these critical riverbank structures.

3D SIMULATION OF THE EFFECT OF SPUR DIKES SPACING ON BED DEFORMATION, FLOW AND PERFORMANCE EVALUATION IN MEANDERING CHANNELS

3D SIMULATION OF THE EFFECT OF SPUR DIKES SPACING ON BED DEFORMATION, FLOW AND PERFORMANCE EVALUATION IN MEANDERING CHANNELS

The Impact of Spur Dikes on the Dynamics of Erosion and Deposition Processes in the Nile River in Abnub Area: A Study in Engineering Geomorphology Using Artificial Intelligence

The Impact of Spur Dikes on the Dynamics of Erosion and Deposition Processes in the Nile River in Abnub Area: A Study in Engineering Geomorphology Using Artificial Intelligence

Review on different shapes of spurs and their effects on channel morphology

Abstract In this paper, the significance of the shape of spurs on flow and bed morphology is understood, accompanied by an appeal to investigate alternative shapes like L-head, T-head spurs, and hockey-shaped spurs, which could offer considerable benefits for river management. The spurs with T-head shape are found to be more efficient in reducing the bed scouring of the channel relatively, although it depends on the orientation of the spur, location of installation, and shape of the channel. Furthermore, development of horseshoe vortex is found insignificant near the base of the T-head spur dike. T-head spurs could more effectively redirect flow and prevent erosion while L-head spurs may enhance riverbank stability. This highlights the need for more investigation into how different spur shapes collectively affect river morphology, flow velocity, and sediment transport patterns. Temporal variations in bed morphology, especially the scour depth and sediment transport dynamics near spur dikes, should also be investigated to understand their changing impact better. Finally, this study provides a complete summary of existing knowledge gaps and future research initiatives relevant to various shapes of spur dikes and their role in riverbank erosion management.

Assessment of the Technical Condition of Spur Dikes

Spur dikes are one of the types of structures for engineering protection of the roadbed, which, in combination with a wavedamping beach, are used to protect the railway track from wave action.The objective of this work is to improve safety of coast railway track operation in areas subject to wave action. The author used the methods of experimental research and survey for obtaining the criteria for assessing the technical condition of spur dikes.Based on the results of the survey of spur dikes, conclusions were drawn about low quality of construction, and the main types of defects were identified both in entire structures and in their elements. Experimental studies on hydrowave models were carried out to assess the beach­holding capacity of the spur dikes and their resistance to wave action in the wave basin. It was proposed to divide the spur dikes into separate elements according to the degree of their significance, and the criteria for the technical condition by types of defects for each element of the structure under consideration were obtained.The technical condition criteria obtained from the results of surveys and experimental studies make it possible to assess the technical condition of spur dikes, which will increase railway operation safety.

Numerical Simulation of 3D Flow Structure and Turbulence Characteristics near Permeable Spur Dike in Channels with Varying Sinuosities

Owing to the different degrees of bending in rivers in nature, it is difficult to conduct experiments in situ. In this study, the renormalization group (RNG) k-ε turbulence model in ANSYS Fluent was used to analyze the three-dimensional flow structure and turbulence characteristics near a spur dike and to evaluate the variation trend of flow in rivers with different degrees of bending. The results show that in channels with different curvatures, the vortex appears between the spur dikes and is disturbed by the permeable hole, and the backflow area moves downstream. The strength of secondary flow (SSF) fluctuates greatly in the vicinity of the spur dike and the downstream region, and the peak value appears 3.22 m (21.5 times L) away from the inlet of the bend. The SSF increases as the bend curvature increases. The SSF displays similar variation trends in the three kinds of bends. The peak value of normalized turbulent kinetic energy (NTKE) appears 3.14 m away from the entrance of the bend, the NTKE is the largest in the 45° bend and the smallest in the 180° bend, and it decreases only at distances of 3.25–4.19 m away from the entrance of the bend as the bend curvature increases.

Downward seepage effects on flow near a L-shape spur dike and bed morphology

Spur dikes are structures built along riverbanks that serve two purposes: stabilizing the banks and minimizing erosion risk by controlling water flow in the river channel. The current study used L-shaped spur dikes in an alluvial channel to analyze the bed morphology and flow pattern in the spur dikes zone with the influence of no-seepage and two distinct seepage velocities, VS1 = 0.075 mm/s and VS2 = 0.15 mm/s near the channel bed z/h < 0.2. The experimental study was also done to examine and compare the transformation in the local scour depth for the seepage condition. According to the study results, downward seepage movement causes significant modification in the channel's bed elevation and the development of scour depth. Observations indicate that the maximum local scour occurs at the first spur dike's leading edge. Seepage velocity VS1 results in a 16.1% increase in the maximum scour depth compared to the no-seepage scenario. In comparison, seepage velocity VS2 causes an increase of 25.2% in the maximum scour depth. Due to downward seepage, the flow distribution is shifted down near the channel's boundary. With an increase in the seepage rate, the magnitude of velocity, Reynold shear stress, turbulent kinetic energy, and bed shear stress also rise close to the channel's boundary. The current study also examined bursting events near the channel's bed under seepage and no-seepage conditions. These events included outward interaction, inward interaction, ejection, and sweep. Quadrant analysis of velocimeter data revealed that ejection and sweep were the dominant events contributing to the production of Reynolds shear stress in seepage and no-seepage flows. Meanwhile, outward interactions and inward interactions made minor contributions compared to ejection and sweep events to the Reynolds shear stress.

Improving in-stream nutrient retention potential through factitious manipulation: the stepping stone structures of flying-geese pattern and their reinforcement structures.

Small streams are essential parts of water ecosystems, such as rivers, lakes, and reservoirs, performing vital functions in the attenuation of nutrient pollution. As eutrophication becomes an increasingly severe problem in waters, it is necessary to investigate how to improve nutrient retention potential in streams. In this study, the effect of artificial manipulation was examined on transient storage and nutrient uptake in streams by setting up the stepping stone structures of flying-geese pattern (SG) and the combination mode of SG and bilaterally staggered spur dikes (SG+SD) in the channel. The tracer experiments were performed to confirm the effectiveness of SG and SG+SD in two headwater streams, which are tributaries of the Chaohu Lake basin. Additionally, the transient storage and nutrient uptake potential were assessed by the OTIS (one-dimensional transport with inflow and storage) model and the nutrient spiraling theory. Compared with the control, the implementation of SG in the Banqiao River increased the retention of ammonium (NH4+) and phosphate (PO43). Furthermore, the transient storage capacity and nutrient uptake potential in the Ershibu River were strengthened with the addition of bilaterally staggered spur dikes based on SG. These results highlight the importance of manipulating the geomorphology of the streambed to enhance the nutrient retention potential in streams.

Migrating scour depth around a spur dike with downward seepage using multiscale characterizations

The current work uses an experimental method to analyse a multiscale statistical assessment of scour depth surrounding the spur dikes with downward seepage. The experiments used three T-shape spur dikes arranged in three series and provided outward from the channel's bank. A no-seepage condition and two distinct seepage velocities, VS1 = 0.09 mm/s and VS2 = 0.18 mm/s, were used in the experiments. Seepage from a channel affects the morphological behaviour and stability of the channel's bed, leading to changes in its hydrodynamic characteristics. In addition, downward seepage movement shifts the flow near the channel boundary and weakens the particles' stability. Thus, the streamwise velocity and Reynolds shear stress increase near the bed. As the seepage velocity increases, the local scour formation also rises relative to the channel's bed until the channel reaches a state of equilibrium. The celerity of scour depth for both time and length scales depends on the amount of downward seepage. Initially, higher seepage leads to faster changes in the scour depth, but over time, this rate decreases until it becomes constant. The bedform elevations' tails are thicker initially, but they become thinner and closer to the Gaussian distribution curve over time.

Effects of waterway regulation structures on the planktonic community in the upper Yangtze River

To investigate the effects of the waterway regulation structures on the hydraulic characteristics, water physicochemical factors, and the planktonic community in the upper Yangtze River, this study was conducted in August and September of 2022 on two ecological dikes in the Chongqing section of the upper Yangtze River: the longitudinal dike and the spur dike. High-throughput sequencing technology was used to explore the differences in planktonic community structures upstream and downstream of the waterway regulation structures during the dry season, as well as their main influencing factors. The results showed that the dissolved oxygen increased significantly, and the turbidity and flow rate decreased significantly in downstream of dikes. The spur dike exhibited more pronounced changes in water quality and hydrodynamic factors compared to the longitudinal dike. The diversity index of phytoplankton, zooplankton, and fungi in the downstream of dikes were higher than those in the upstream, and the bacterial diversity index was higher than those of eukaryotes at each sampling site. The impact of the spur dike on the planktonic biodiversity index was greater than that of the longitudinal dike, as it alters flow velocity, turbidity, and dissolved oxygen. The major phyla of phytoplankton, zooplankton, and bacteria, including Cryptophyta (70.37–80.57 %), Mollusca (7.56–37.50 %), and Proteobacteria (48.53–55.92 %), had a higher relative abundance in upstream of dike, and their relative abundance in spur dike was higher than that in longitudinal dike. In contrast, the relative abundance of the major phylum of fungi, Ascomycota (37.15–56.85 %), showed an opposite trend in both dike-to-dike comparison and dike upstream-to-downstream comparison to the above three plankton. The analysis of the neutral community model indicated that the predominance of stochastic assembly processes in the planktonic community was higher in the longitudinal dike compared to the spur dike, and longitudinal dike demonstrated higher rates of planktonic migration and speciation compared to the spur dike. Flow rate, dissolved oxygen, and turbidity were the significance influencing factors on the planktonic community structure in the aquatic environment around dike. Differences in dike-related environmental factors result in greater interactions among prokaryotes in the spur dike, while eukaryotes exhibited a more complex network of relationships in the longitudinal dike. These findings can provide a theoretical basis for the protection of biodiversity and the construction of ecological waterways in the waterway regulation engineering area.

Influence of spur dike’s angle on sand bar formation in a rectangular channel

Spur dike is one of the various technologies utilized in river rehabilitation. Spur dike provides many advantages, such as promoting aquatic habitat, improving channel for navigation, and protecting the stream banks. This study serves to evaluate the effect of a spur dike on the formation of sand bars in a straight rectangular channel fed by suspended sediment. The performance of spur dike in inducing the formation of spur dike is investigated under three different spur dike angles. A three-dimensional (3D) model was developed using Flow-3D® to investigate the flow depth and velocity around spur dike. Based on the velocity distribution, the influence of spur dike angle on the formation of sand bar was explained. A scalar concentration is used to represent the suspended sediment in the simulation, and the formation of sand bar is represented by the scalar concentration. According to the numerical results, the 90° spur dike produced a larger and longer sand bar than the 45° and 135° spur dikes.

Scour Mitigation at Bridge Abutments Using Spur Dikes

Scour Mitigation at Bridge Abutments Using Spur Dikes

Effects of the Diversity of Flow Velocity on the Upstream Migration Behavior of Grass Carp in the Reaches of Spur Dikes

The construction of spur dikes alters the flow pattern of rivers and affects the upstream migration behavior of fishes. Traditional rock-fill spur dikes and experimental permeable spur dikes with a “Weighted Excess Storage” (WES) profile were evaluated using hydrodynamic experiments and experiments on the upstream migration behavior of juvenile Grass Carp (Mylopharyngodon idella). The swimming ability and upstream migration paths of juvenile Grass Carp in the spur dike were analyzed, and the relationship between the upstream migration success rate of Grass Carp and the diversity of flow velocity was studied. The induced velocity and critical velocity of juvenile Grass Carp with a body length of 5 ± 0.5 cm are 0.1 m/s and 0.7 m/s according to the experiment. The flow velocity diversity index increased roughly in a power function trend with the increase in flow discharge, and under the same flow conditions, the flow velocity diversity index of permeable spur dikes was greater than that of rock-fill spur dikes. When the flow velocity was within the preferred velocity range of Grass Carp, the success rate of upstream migration increased linearly with the diversity of flow velocity. When the velocity was greater than 60% of the critical velocity of Grass Carp, the success rate of upstream migration dropped sharply. Compared with rock-fill spur dikes, the experimental permeable spur dikes provide a passage for the upstream migration of fishes and reduce the impact on the upstream migration of fish. The results of this research provide theoretical support for ecologically optimized designs of spur dikes and the ecological management of rivers.

Local scour around submerged angled spur dikes under ice cover

Local scour is a phenomenon leading to the localized lowering of the channel bed due to the imbalance of sediment transport. As spur dikes protrude into the natural channels, local scour could be triggered. Accurate estimation of local scour around spur dikes is crucial for the effectiveness of erosion control and prevention and habitat enhancement measures. In the current study, the correlations between the maximum scour depth and the overtopping ratio, spur dike dimensions, ice cover roughness, and grain size of the bed material are investigated. Under both open channel and ice-covered flow conditions, a variety of experiments were done in a large-scale outdoor flume with different experimental setups. The results revealed that the scour depths around submerged spur dikes increased with increases in the densimetric Froude number and the decreases in the overtopping ratio and alignment angle. The maximum scour depth around a submerged angled vertical wall spur dike is significantly affected by the presence of an ice cover on the water surface, namely, the rougher the cover, the deeper the scour hole. Based on data collected from the laboratory experiments, an existing maximum scour depth estimation equation has been modified to consider the influence of the cover condition and the submergence level. The calculated results showed high accuracy in estimation of the measured data.

Numerical modeling of scour and erosion processes around spur dike

AbstractSpur dikes are popular river training structures used for flow diversion, flood control, bank protection, and improving navigation. This paper aims to study the numerical modeling of scour depth in the vicinity of a rectangular spur dike using the renormalization group (RNG) turbulence model and sedimentary van Rijn model with nested mesh configuration using FLOW‐3D. This study is also carried out to analyze the three turbulence models such as RNG, 𝑘−𝜀, and Large‐Eddy simulation (LES), for estimating the scour depth and evaluating the temporal variation of maximum scour depth. It is observed that scour depth is overpredicted with the LES model configuration used in the present study, as compared to 𝑘−𝜀 and RNG models. Furthermore, the scour depth increases by increasing the bed load coefficient near to the spur dike. Simulated results show a good agreement within a 5% error with experimental results regarding the net change of sediment elevation and scour depth.

Energy Dissipation Potentials of Grouped Spur Dikes in an Open Channel

Energy Dissipation Potentials of Grouped Spur Dikes in an Open Channel

Restoration of a fish-attracting flow field downstream of a dam based on the swimming ability of endemic fishes: A case study in the upper Yangtze River basin

The construction of fish passage facilities can mitigate the negative effects of dams and other water engineering construction on river connectivity and have a significant positive effect on the conservation of local fish diversity. To attract target fishes into fish passage facilities effectively, the optimal flow velocity range to attract fish must be determined. Three local endemic species of the Mishi Reservoir were considered as the protection targets. However, their swimming abilities remain unclear. Therefore, the induced swimming speed (Uind), critical swimming speed (Ucrit) and burst swimming speed (Uburst) of three fish species were tested. Based on these results, we identified the optimal flow velocity to attract fish, which falls within the range of 0.15–0.51 m/s. A validated three-dimensional hydrodynamic model was used to simulate different schemes. By comparing the flow field simulation results of different schemes, we obtained the optimal measure to restore the flow field, namely, a multiple engineering measure combining increased the fish attraction flow in the fish collection pond and the construction of a spur dike. This study offers a solution for the specific case and enhances the database of swimming characteristics of endemic fish in the upstream reaches of the Yangtze River. It also provides a valuable reference for designing fish-attracting flows and potential measures for restoring flow fields in similar future projects.

Hydro-morphological behavior around T-shaped spur dikes with downward seepage

The present work experimentally analyses the flow behaviour near the T-shaped spur dike field with no seepage, 5%, and 10% downward seepage. Experiments were aimed at analysing the channel morphology with different discharges. According to the results, downward seepage movement causes significant modification in the channels bed elevation and the development of scour depth. The maximum scour depth is observed at the edge of the first spur dike facing the flow. The rate of scouring also increases with the effect of seepage. Due to downward seepage, the flow distribution is shifted near the channel bed. However, near the channel boundary attained some velocity, significantly enhancing the sediment transport rate. The wake zone between the spur dikes saw very low-velocity magnitudes of positive and negative values. This reveals secondary current generation inside the loop and cross-stream circulation. With an increment of seepage percentage, the velocity, Reynold shear stress, and turbulent kinetic energy magnitude also rise close to the channel’s boundary.

The influence of hyporheic exchange with spur dikes: Laboratory experiments

It is important to understand heat transfer changes in the hyporheic zone of spur dikes when assessing ecological restoration and sustainability in rivers. To reveal the rule of hyporheic exchange under the action of a spur dike, the sinusoidal temperature change of surface water was set with a period of 24 h. The porous subsurface flow paths under different riverbed forms were plotted through dye tracing. In addition, the influences of surface water velocity (U), river width narrowing ratio (L/B), the number of spur dikes and riverbed shape on hyporheic exchange were also studied using the temperature tracing method. The results show that the hyporheic exchange path presents a trend of diagonal flow downstream, first conducting turbulent diffusion upstream and then sinking, with different riverbed morphologies having different path lengths. The temperature of surface water has a significant controlling effect on the temperature field of the riverbed. The sediment temperature change from the water–sediment interface to 0.3 m depth is closer to the sinusoidal trend. The change in surface water velocity (U) has the most significant effect on the temperature amplitude ratio. The temperature field below spur dikes is more susceptible to the impact of spur dikes and usually presents a “semielliptical” high-temperature area. With the increase in surface water velocity (U), river width narrowing ratio (L/B), and the number of spur dikes, the range of hyporheic exchange under the dam head also increases, which is positively related to the vertical section hyporheic exchange flux at the dam head. The local backwater area generated by spur dikes also affects pressure field distribution near spur dikes, but the changes caused by the fluctuation of the riverbed itself are greater than the impact of spur dikes on the riverbed. The water–sediment interface velocity at the spur dike increases sharply, and the upstream 1 m of the dam head gradually experiences upflow, drops sharply after reaching the maximum at the dam head, and then approaches zero after 1 m. There is no obvious upwelling and downwelling at the whole interface.

Flow Control in a Rectangular Open Channel using Two Impermeable Spur Dikes: A Numerical Study

The present study examines how adjusting vegetation patches in a rectangular open channel with two impermeable spur dikes alters the displacement of the recirculation region. The Reynolds stress turbulence model is implemented via the 3D numerical code FLUENT (ANSYS). Mean stream-wise velocity profiles were drawn at selected positions and at mid of flow depth i.e., 3.5 cm, a horizontal plane is cut through the open channel for analyzing velocity contours and streamline flow. The findings indicate that the stream-wise velocity profiles showed fluctuations in the presence of different shapes and arrangement of cylindrical patch discussed and the maximum velocity within the field of spur dike is of the order of 0.018 m/s due to the prism shape. By changing the position of the cylindrical patch, the location of the recirculation region displaces within the field of impermeable spur dike.