River Bend Research Articles

Research on Ecological Culture in Mongolian Folk Songs from the Hetao Region

Mongolian folk songs are deeply rooted in the vastness of the grasslands and the rhythm of nature. The lyrics reflect a profound reverence and love for the ecological environment, demonstrating a strong awareness of ecology and environmental protection. Especially in the Hetao region, Mongolian culture along the Yellow River's bend showcases a rich and diverse uniqueness, forming a distinctive cultural phenomenon in this area. By deeply analyzing Mongolian folk songs from the Hetao region, this study, through the combined perspectives of literature, linguistics, ethnology, history, and ecology, discusses the ecological values and educational significance of the harmonious relationship between humans and nature as embedded in these songs.

Flow Dynamics in a River Bend in Response to Hydrological Variations—The Gomti River (India) Case Study

Flow Dynamics in a River Bend in Response to Hydrological Variations—The Gomti River (India) Case Study

Numerical simulation of morphological evolution in a gravel-bed meandering river during floods: a case study on the Sai-Jiang river

ABSTRACT The water velocity undergoes a significant increase during the initial stage of floods. The present study focuses on investigating the scours and silting occurring in an S-shaped gravel-bed river. The primary objective is to analyze the impact of 10-year flood events on both the riverbed and bank stability. This river is located in the Sai-jiang River reach, Fujian Province, China. A numerical model of riverbed scours and silting is herein tested. The research results indicate that the morphological evolution of the whole river section is affected in the early stage of flood evolution; however, in the later stage, some key places such as the bridge and the river land are still greatly affected. The apex of the river bend is in close proximity to the downstream river island, resulting in scour at the head of the river island that deviates from conventional patterns of head scour and tail siting. Furthermore, the presence of artificial structures like bridges exacerbates the scour and silting processes in river beds during flood events. For this case, the riverbed adjacent to the Banzhong Bridge pier experienced a widening of approximately 50 m and downstream extension of around 300 m, with a maximum vertical scouring depth of 2.87 m.

Characteristics of thalweg profile and cross-sectional geometry along alluvial river bends

ABSTRACT River bends have always drawn attention for their complicated hydraulic, geometric and migration nature. Laboratory as well as field experiments have been carried out to study the geometric behaviour of channel bends. This study aims to analyse the nature of the thalweg profile, longitudinal and transverse slope and distribution of depth in the cross-sectional geometry of both single and consecutive double bends of the channel. In the single bend, the thalweg approaches to the outer bank and becomes closest after the apex of the bend whereas in the successive bends of a double bend, the thalweg is closest before the apex of the bend. These results indicate that the thalweg of a bend depends on the previous consecutive bend. The longitudinal slopes vary periodically along the river bend creating the deepest pool before the apex of the bend. The centre line transverse slope varies periodically; however, the outer transverse slope with respect to the thalweg is maximum where the thalweg is closest to the outer bank. The thalweg and outer quarter line to centre line depth ratio is higher before the apex and reduces after the apex of the bend. The inner quarter line to centre line depth ratio varies periodically with a relatively smaller amplitude.

Scour Features due to Inclined and Curved Rock Sills at River Bends

Scour Features due to Inclined and Curved Rock Sills at River Bends

Research On the Path of High Quality Development Enabled by Big Data Technology in the Curved Area of The Yellow River

Big data is a key factor of production to promote the current social development, and the good use of big data technology is a must to achieve high-quality development. Jiziwan of the Yellow River is a strategic overlapping area of the western development and the overland Silk Road, which has very important strategic value both in terms of geographical space and historical development. Therefore, it is particularly important to enable the high-quality development of the Yellow River Jiziwan region with big data technology. By analyzing the relevant data of the high-quality development of the main provinces of the Yellow River Bend in recent years, this paper makes a comparison of the gross product of the region in recent years, the added value of the three major industries, and the R&D investment of the industrial enterprises, so as to get the results of the high-quality development of the Yellow River Bend area and the existing problems. Through these analysis results, this paper puts forward some solutions: using big data technology to optimize regional industrial structure, promote high-quality ecological development and promote innovative development. These optimization paths help promote the importance of the digital economy and promote high-quality, sustainable and coordinated development in the region.

High methane ebullition throughout one year in a regulated central European stream

Ebullition transports large amounts of the potent greenhouse gas methane (CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}) from aquatic sediments to the atmosphere. River beds are a main source of biogenic CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}, but emission estimates and the relative contribution of ebullition as a transport pathway are poorly constrained. This study meets a need for more direct measurements with a whole-year data set on CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} ebullition from a small stream in southern Germany. Four gas traps were installed in a cross section in a river bend, representing different bed substrates between undercut and slip-off slope. For a comparison, diffusive fluxes were estimated from concentration gradients in the sediment and from measurements of dissolved CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} in the surface water. The data revealed highest activity with gas fluxes above 1000 ml m-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-2}$$\\end{document} d-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} in the center of the stream, sustained ebullition during winter, and a larger contribution of ebullitive compared to diffusive CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} fluxes. Increased gas fluxes from the center of the river may be connected to greater exchange with the surface water, thus increased carbon and nutrient supply, and a higher sediment permeability for gas bubbles. By using stable isotope fractionation, we estimated that 12-44% of the CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} transported diffusively was oxidized. Predictors like temperature, air pressure drop, discharge, or precipitation could not or only poorly explain temporal variations of ebullitive CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} fluxes.

Flow patterns at river bends and its response to surrounding infrastructures

On January 6, 2023, high-intensity precipitation occurred in the Babon River watershed, causing the river overflow and flood in several areas. Severe impact in the surrounding area was observed, such as in the Dinar Indah Housing Complex. Hydrodynamic complexity around a river bend points out the importance of understanding the flow patterns at a river bend. Therefore, this study aimed to describe the flow pattern of the river bend and analyze its response to the surrounding infrastructure using the HEC-RAS 6.3 model. Furthermore, improvement to structural mitigation was also designed. Field observations were also conducted to gather field data on the flood impact. The model results indicate that the highest water level within the river bend is 1.9 m, and the highest velocity is 5.85 m/s, which is on the outer bend. A dyke was then planned to be about 3.75 meters high, accompanied by a retaining wall to protect the river bank using the interlocking permeable revetment (IPR). Dyke and retaining walls provide stability against shear, overturning, and collapse.

Late‐Holocene counterpoint deposition in the Lower Rhine River

ABSTRACTChannel deposits from meandering rivers have proven to be far more complex than the well‐known lithofacies model consisting of coarse‐grained channel, gravelly channel‐lag and fine‐grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine‐grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint‐bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice‐pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice‐pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives.

Effect of the transition section on the flow structure of consecutive river bends with point bars

The transition section (TS), linking the front bend and the back bend in consecutive river bends, plays a key role in the flow hydraulic characteristics, sediment transport, and riverbed evolution in meandering rivers, which is crucial for flood control, navigation, and river stability. Most existing studies on the hydraulic effect of the TS focus on flat-bed scenarios, rendering an inadequate understanding of the TS in consecutive bends with point bars, often found in natural rivers. Based on three-dimensional numerical simulations, the effects of the length and the topography of the TS are investigated in detail on the flow structure in consecutive bends with point bars, respectively. The results reveal that without an adequate TS length, the residual circulation of the front bend (RC) inhibits the development of the main circulation in the back bend (MC), causing the positions of the maximum strength of the MC and the maximum value of cross-section-averaged turbulent kinetic energy (<tke˜>) in the back bend moving upstream. As the length of the TS increases, the above effect of the front bend gradually decreases. The critical length of the TS to fully decay the RC is 4.8 times the bend width (B) in consecutive bends with point bars, longer than that (4B) in the flat-bed bend. Furthermore, the central bar in the TS is found to facilitate the generation of the outer bank cell and accelerate the decay of the RC. These effects of the TS can profoundly change the flow hydraulics, sedimentation, and stream stability of consecutive bends. The results of the study will help to further understand the linkage role of the TS in consecutive bends and may serve as a rational reference for managing natural meandering rivers with multiple hydrological, geomorphological, and/or ecological goals.

Potential Dam Breach Flood Assessment with the 2D Diffusion and Full Dynamic Wave Equations Using a Hydrologic Engineering Center-River Analysis System

Dam breaches have catastrophic consequences, causing severe property damage, life loss, and environmental impact. The potential dam breach downstream flooding of the Kulekhani reservoir, Nepal, was studied using a 2D Diffusion Wave Equation (DWE) and Full Dynamic Wave Equation (FDWE) through an open-source solver, Hydrologic Engineering Center-River Analysis System (HEC-RAS). The suitable dam breach model was identified based on the dam geometry and sixteen historical dam failure cases. The simulated downstream peak was tested with an empirical relation, considering reservoir volume and duration of failure. Model comparisons through the flood plain mapping of water depth, flow velocity, flood intensity as per guidelines of the American Society of Civil Engineers (ASCE), and arrival time were carried out for flood hazard assessment. FDWE was able to capture the physical flow phenomena in the river bend resulting in higher flow velocity at the outer bend, lower velocity at the inner bend, and formation of eddies due to the application of the turbulence model, considering possible momentum losses, whereas DWE was unable to capture these effects due to a simplified momentum equation. The total area of flood extension was found to be increased by 30% using FDWE than the DWE due to higher water surface elevation. Most of the towns along the Kulekhani River were classified as “Very High” intensity flood regions according to ASCE, due to the V-shape valley. The peak time difference at the Bagmati River confluence was evaluated between the models. This plays an important role in decision-making for the selection of the flood model to make a safe evacuation plan. The application of FDWE was found to be suitable for the rapidly varying unsteady flow in the steep meandering river.

Effect of Bridge Piers Locations and Flow Intensity on Morphological Change in a 180-Degree River Bend

Effect of Bridge Piers Locations and Flow Intensity on Morphological Change in a 180-Degree River Bend

Higher-order turbulent characteristics of sinuous alluvial river

Sinuous channels with movable banks were examined for flow patterns in laboratory experiments. The velocity, Turbulent kinetic energy (TKE) budget, TKE flux, and bursting events were analyzed to examine the turbulent flow behavior. Quadrant analysis is performed to determine the contribution of bursting events to Reynold shear stress. At the apex of the sinuous channel, quadrant analysis reveals a mixing of events. On the other hand, as the hole size increases, the contribution of events decreases. The TKE (turbulent kinetic energy) flux is greater near the riverbed and diminishes as it approaches the bed surface. The TKE flux is higher at the river bend's exit than at the entry point. Examining the TKE budget, the TKE production and TKE dissipation indicate that TKE dissipation surpasses the production near the riverbed and the surface. These terms are uniformly distributed and decrease as they approach the surface.

Morphology Dynamics of Ice Cover in a River Bend Revealed by the UAV-GPR and Sentinel-2

After the formation of the bend ice cover, the ice thickness of the bend is not uniformly distributed, and an open-water area is usually formed downstream of the bend. The spatial and temporal variation of the ice thickness in seven cross sections was determined via Unmanned Aerial Vehicle Ground Penetrating Radar (UAV-GPR) technology and traditional borehole measurements. The plane morphology change of the open water was observed by Sentinel-2. The results show that the average dielectric permittivity of GPR was 3.231, 3.249, and 3.317 on three surveys (5 January 2022, 16 February 2022, and 25 February 2022) of the Yellow River ice growing period, respectively. The average ice thickness of the three surveys was 0.402 m, 0.509 m, and 0.633 m, respectively. The ice thickness of the concave bank was larger than that of the convex bank. The plane morphology of the open water first shrinks rapidly longitudinally and then shrinks slowly transversely. The vertical boundary of the open water was composed of two arcs, in which the slope of Arc I (close to the water surface) was steeper than that of Arc II, and the hazardous distance of the open-water boundary was 10.3 m. The increased flow mostly affected the slope change of Arc I. Finally, we discuss the variation of hummocky ice and flat ice in GPR images and the physical factors affecting GPR detection accuracy, as well as the ice-thickness variation of concave and convex banks in relation to channel curvature.

Assessment of wastewater treatment potential of sand beds of River Ganga at Varanasi, India

Abstract Inadequate sewage treatment plant (STP) capacity, limited power supply, and discharge of partially treated and raw sewage create a significant sanitation problem in Varanasi city, India. This problem becomes severe during the lean period of the river. To reduce the burden on STPs, sewage can be treated and filtered in a naturally occurring sand bed at the convex bank side of the river. In the present study, a 7-km stretch of the sand bed of River Ganga at Varanasi has been selected. This stretch is divided into three zones: entrance, middle, and exit zones. The objective of this research is to assess the filtration potential of selected sections in respective zones and to find out the most suitable zone, out of the three, for wastewater filtration. Seven basic parameters such as dissolved oxygen, biological oxygen demand, electrical conductivity, total dissolved solids, salinity, pH, and temperature were measured before and after filtration, through the sand bed of the three zones of River Ganga. Of the three selected zones of the river bend, filtration length and the amount of available sand were found to be maximum in the middle zone. Experimental results and survey work show that the sand bed in the middle zone of the river bend is best suited for wastewater disposal and filtration.

River bend sediment management using modified triangular vanes

ABSTRACT Triangular vanes (TVs) are among the flow pattern correction structures which have recently been considered environmentally friendly structures against river bend bank erosion. However, the scour around the structure’s tip may cause its failure. On the other hand, it has been shown that the use of slot in the bridge pier and bridge abutment is effective in reducing scour depth, hence in this study, the effect of four different positions of rectangular slot on TV: Case 1) near the TV’s tip, parallel to the vane’s chord and close to the bed; Case 2) near the outer bank, parallel to the vane’s chord and close to the water surface; Case 3) horizontally and near the bed and Case 4) vertically and near the outer bank is experimentally studied in a 90° mild bend flume. The maximum scour depth (ds), and the point bar height at the end of experiments were compared with the case of no slot (Case 0). The best performance in reducing ds was obtained for Case 1 and then Case 3 with 24% and 19% reduction compared to Case 0, respectively. Poor performance was found for Case 2.

Assessment of flood dynamics in a mountain stream using high‐resolution river flow records

AbstractUnderstanding the streamflow hydrodynamics is important for forecasting flooding phenomena in mountainous rivers. Accordingly, based on long‐term runoff observations obtained using diverse runoff techniques (i.e., rating curves and fluvial acoustic tomography (FAT)), the authors (1) evaluated and explored flood phenomena, (2) discussed the effects of dams on flood hydrograph, (3) and revealed backwater effects caused by river channel bends, sand bars, and floodplains. The duration and slope of the falling limb of the hydrograph were directly influenced by the catchment characteristics that affected runoff recession, whereas the behaviour of the rising limb of the hydrograph was directly influenced by rainfall. A weaker correlation between discharge and rainfall in higher flood events indicates that rainfall events were strongly altered by water released from dams in the basin. Additionally, because of the backwater effects, the rate at which the flow velocity and boundary shear stress changed with the increasing discharge was reduced, potentially slowing the pace of erosion. Our findings are relevant for managing mountain rivers, particularly in river bend reaches prone to backwater effects. The FAT method could help increase the ability to monitor short‐term fluctuations in floods and associated hazards.

Numerical Modeling of Flow Pattern at a Right-angled River Bend Using CCHE2D Model

In this study, the CCHE2D model is used to analyse the flow pattern in a meander reach of the Gomati River. The finite volume method is used by the numerical model to solve the depth-averaged two-dimensional equations with 𝑘−𝜀turbulence closure. The numerical findings were compared with field data for two different flow rates in order to calibrate the CCHE2D model using various Manning's roughness coefficients. The results show that for the minimum and maximum discharges, a smaller Manning's roughness factor (0.015≥𝑛≥0.025)is more favorableto a higher Manning's roughness factor(0.030≤𝑛≤0.040). The results of the numerical model demonstrated that fluctuations in hydraulic parameters including shear stress, velocity, flow depth, and Froude number in the river bend are greatly influenced by the existence of centrifugal force and helical cells. The linear relationship between velocity and shear stress is presented across the whole study reach, as indicated by the R-squareand linear correlation coefficient (r) components. The results of the model show that the flow field within the river bend can be accurately simulated by the computational model.

Morphological evolution mechanism of Gravel-bed braided river by numerical simulation on Da-jia River

• “central bar formation” and “channel avulsion” are the main river evolution mechanism in the simulated gravel-bed reach. • As the river width expands downstream, the longitudinal profile gets stable, while the transverse oscillation becomes wild. • If the longitudinal structure (bank revetment) on the concave bank of a gravel-bed river is made by concrete with relatively smooth surface, it is very likely to cause further damage on the longitudinal structure. Due to a steep slope, rapid flow, and large amounts of sediment, rivers in Taiwan are braided rivers that are full of bars and bifurcated flows. The channel shifting behavior and bar migration within natural braided rivers results in difficult river engineering. In this study, the Nays2DH model was used to simulate the braiding processes and morphological changes downstream of Shigang Dam in the Da-jia River from 2012 to 2013. Furthermore, the characteristics of riverbed erosion, the stability of the channel in the longitudinal and transverse directions and the impact of river structures on the morphology were simulated. The numerical model can present morphological and evolutionary processes similar to an actual river, such as: central bar formation, chute cutoff, and channel avulsion. The scour pool mostly occurred at the apex of the river bend and downstream of the bar (confluence) in a braided river, which means that bar migration is the main factor that alters scour position. Under the assumption of equilibrium sediment transportation across the upstream inflow section, the width of the channel determines whether the river demonstrates longitudinal erosion or transverse changing. Results from this research can be used as a substantial reference for future research concerning river morphology evolution, river engineering, and river space planning.

On the Impacts of Ice Cover on Flow Profiles in a Bend

AbstractWe investigate the impact of ice coverage on flow and bed shear stress profiles in a river bend. We perform field measurements using Acoustic Doppler Current Profiler in a bend of the Red River, North Dakota, the United States. Field campaigns were carried out under both open‐surface and ice‐covered conditions in 2020 and 2021. Our results show that the time‐averaged velocity profile follows closely the quartic solution (Guo et al., 2017, under full ice coverage. While the flow profile under open‐surface condition follows closely the logarithmic law near the bed, it is challenging to identify the logarithmic layers in our measured data under ice‐covered condition. Our results also show that the impact of ice coverage is most significant near both banks where the vertical velocity profile is modified significantly due to the interaction of turbulent flows with the ice cover. Our results suggest that the bend curvature and ice coverage both have significant impacts on the velocity profile as well as the distribution of the bed shear stresses. Our findings provide new insights on sediment transport processes of ice‐covered rivers, especially during the break‐up period when the surface coverage changes rapidly.