Numerical simulation of optimum groyne arrangement for preventing bank erosion (Case study of Ghezel-Ozan River)

Numerical simulation of optimum groyne arrangement for preventing bank erosion (Case study of Ghezel-Ozan River) | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Numerical simulation of optimum groyne arrangement for preventing bank erosion (Case study of Ghezel-Ozan River) Jafar Chabokpour This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4623183/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This paper will discuss the optimum groyne configuration for preventing bank erosion alongside the Ghezel-Ozan River in Iran through advanced numerical simulations. The research used FLOW3D software to investigate the effects of spacing, lengths, the number, and the orientation of groins on flow patterns and erosion potential. In this regard, some key hydrodynamic parameters, such as Turbulent Kinetic Energy, Overall Flow Velocity, and Froude Number, are analyzed to quantify the efficacy of various groyne arrangements. The study area, belonging to the Eshtibin region of East Azarbaijan Province, is a 3-kilometer segment of the river, with a design flood discharge of 1435 m3/s for a 25-year return period. Coupled with detailed mesh (with 800,000 elements) and bathymetric data, this numerical model is to be used to represent as exactly as possible the morphology of the river. In this study, there are four groyne placement scenarios, showing the effect of number of groynes (4 or 7 units), spacing intervals (2.8 and 3.6 times the groyne length), and angular orientation (perpendicular and 30 degrees downstream). The results indicate that, upon the introduction of groynes, there are prominent changes in flow patterns and velocity distributions; therefore, this offers an avenue for erosion control. The study reveals that the optimal groyne configuration is dependent on site-specific conditions and design objectives, such as 4 number of groynes with 30 degrees orientation, stating tailored approaches are very important in river management strategies. Ghezel-Ozan River groyne arrangement FLOW3D software hydrodynamic parameters Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction A groyne is a structure that is placed transverse to the flow of a river to manage river bank erosion by diverting flow from the river bank. A groyne can be made out of various material like stone, concrete, wood, or a gabion. Groyne work by altering the flow away from the bank side, as flow is diverted sediment deposition begins, which leads to the stabilization of the river bank. Groyne effectiveness may depend on the dimensions of the groyne, which are groyne length, flow deflection angle, and groyne spacing. The groyne length should be long enough for the groyne to deflect flow, though not too long that excessive scour occurs at the groyne head. The flow deflection angle is designed to maximize sediment deposition and minimize bank side erosion. Groyne spacing should be close enough to protect the bank entirely, but not so close, which reduces the upstream sedimentation or impedes flow promoting further erosion. Overall, groynes are generally considered a cost effective protection system for river banks. Groynes can have adverse effects on the river system including but are not limited to changing river morphology and disrupting riparian habitats. Therefore, it is important to evaluate potential impacts before using groins (Chabokpour & Raji, 2024 ; Chabokpour & Zabihi, 2019 ). (LUU et al., 2004) has conducted the research applying a newly developed numerical model and field data analysis to understanding the changes of river channel in the study site, Tan Chau reach of Mekong River in Vietnam. The research results show that bank erosion on the left bank was the main of channel shifting under the influence of a lot of factors such as sediment composition (because inorganic and organic sediments have the different strength) bankline protection measures, flow patterns (meandering, straight), formation of sandbar, and shape of the channel developed. This created numerical model considers the processes including channel shifting and bank erosion are cohesive sediment erosion and sand transport by bedload layer thickness that changed and partly explain the process of channel shifting. In order to evaluate channel erosion and floodplain deposition patterns, (Zhang et al., 2011 ) used a 2D numerical model to simulate water flow and sediment transport and investigate the consequences of overbank flooding on the Lower Yellow River. The study demonstrates that larger floods do not always correlate with increased main channel erosion and that there is a non-linear relationship between sediment concentration and floodplain deposition. The relationship between flood magnitude, sediment concentration, and erosion/deposition processes is complex. The results indicate that the best flood control plans for maintaining channels rely on the specific circumstances, emphasizing the necessity for customized methods to river management and urging more investigation to overcome model constraints and improve comprehension of these intricate fluvial processes. (Asahi et al., 2013 ) introduced a novel computer model that incorporates the intricate relationships between flow dynamics, sediment transport, and bank erosion-deposition processes to simulate the long-term evolution of meandering rivers. The model takes into account variables like vegetation growth and flood events and integrates a number of components, including flow equations, bed evolution tracking, and bank erosion prediction. Even with certain oversimplifications, the model provides insightful information about the development and evolution of river meanders, which may be useful in projects involving river engineering and flood management. (Onda et al., 2010 ) presented a numerical model that included a depth-averaged flow model with equilibrium and non-equilibrium sediment transport models, as well as a simplified bank failure model, to simulate river channel processes with bank erosion in steep curved channels. The study highlights the significance of non-equilibrium sediment transport conditions near river banks for improved accuracy and shows how the model can replicate important features seen in experimental settings, such as point bar formation and riverbed scouring. Nevertheless, the authors acknowledge that additional refinement is required to address complex interactions between flow, sediment transport, and bank erosion in order to improve the model's overall predictive capabilities. (Korovkin, 2015 ) addressed the drawbacks of conventional methods by modeling soil stiffness and treating piles as flexible, rotatable rods in order to provide an inventive way for calculating pile foundation embankments in urban waterfront renovation projects. Through a case study of a St. Petersburg waterfront that has been rebuilt, the study illustrates the improved accuracy of this new approach, contrasting its outcomes with those attained through conventional methods and emphasizing its potential to more closely mimic the behavior of pile foundation structures in the real world. The effectiveness of several building techniques for geobag revetments in preventing erosion along riverbanks was examined by (Khajenoori et al., 2017 ). The results showed that the arrangement of the geobags in stacks had little bearing on the overall performance of the revetment. In order to mimic geobag revetment failure, the researchers created a computer model. This model has the potential to be a useful tool for designing future geobag revetments and help create riverbank protection techniques that are more effective. (Mojtahedi & Basmenji, 2017 ) used the MIKE21-FM numerical model to simulate flow patterns around groynes to test the effectiveness of these structures as riverbank protection structures on Iran's Ghezel-Ozan River, specifically in Achachi. These results suggest that groynes, especially L-shaped designs, can be very effective tools for protecting riverbank erosion. The research shows that groynes successfully diverted the main river flow away from the banks, effectively protecting agricultural land from erosion. L-shaped groynes proved particularly effective at deflecting flow and reducing scouring at the groyne's headland. (Lee & Dang, 2018 ) introduced a novel numerical model that uses a mixed grain size method for bed load representation in order to mimic morphological changes in natural channel bends. The model shows a considerable improvement over earlier uniform grain size models and has been tested using both laboratory and field data. It solves shallow water equations and sediment transport equations to anticipate bed level variations. With its more accurate portrayal of intricate channel dynamics, this sophisticated simulation tool has the potential to improve river management and flood control tactics by providing useful forecasting skills for river behavior and morphology. In a 575-meter section of the Krueng Aceh River in Indonesia, where bridge development has disturbed the river's natural flow patterns, (Fatimah et al., 2020 ) investigated the effectiveness of groynes in reducing bank erosion. The study assesses different groyne structures to maximize flow redirection and erosion reduction at the outer river bend using numerical simulations via the Surface Water Modelling System (SMS 11.2). The results of the study show that strategically placed groynes can effectively deflect water velocity from the bank. The study concluded that the best balance between velocity reduction and minimal eddy formation is achieved by a 7-meter groyne angled at 10 degrees, though the ideal design parameters depend on the particular conditions of the river. The optimal design for groynes (riverbank protection structures) for Indonesia's Konaweha River was studied by (Zulfan et al., 2021 ).The effect of groynes on water flow and erosion was simulated by the researchers using a computer model (2D numerical modeling). After testing sixteen various groyne designs, they discovered that the ones that reduced water flow velocity and stopped erosion along the outer riverbank were those with five structures separated twice as long as the groyne itself. In their research of bank erosion in braided channels, (Masbahul et al., 2022 ) used numerical simulations to identify vulnerable spots and the Brahmaputra River as a case study. Sandbar development and watercourse modifications are examples of small-scale events that are integrated into a model that the researchers construct. Large-scale phenomena include the distribution of flow throughout several channels. In order to show that differences in flow distribution between channels can cause bank erosion, the model effectively reproduces observed channel patterns and sandbar formation. Higher flow rates in a single channel may cause the channel to widen and erode along its bank. (Gao et al., 2023 ) used a mix of computer modeling and experimental data to study the flow structure and short-term riverbed change in curved flumes. The study revealed distorted water surfaces with greater levels on the convex bank and lower levels on the concave bank, coupled with complicated flow patterns in curved flumes that are characterized by secondary circulation and longitudinal velocity differences across the channel width. The results shed important light on the hydrodynamics of curved rivers by showing how flow patterns affect the evolution of bed topography, including scouring upstream of convex banks and deposition downstream. They also emphasize the impact of living vegetation on flow patterns and the severity of bed scouring, which helps to improve river channel design and management techniques. (Vigna et al., 2023 ) performed detailed studies on RPEs (rockfall protection embankments) composed of natural soil. In the process, finite element method simulations assessed their performance against the rock impact. The identification of key failure mechanisms, design tools, and factors that influence the performance of RPEs were evaluated, improving the deficiencies inherent in the existing methodologies. It contributes key findings toward the development of more sophisticated design strategies for RPEs made from natural soils that will eventually be deployed in mountainous areas for mitigation purposes against rockfall hazards. (Hasan & Toda, 2024 ) considered the riverbank protection works on the Jamuna River in Bangladesh. In this regard, a 50 km reach was analyzed with the iRIC Nays2DH numerical modeling. The research evaluates several past countermeasures—for example, embankments, hard points groynes, and revetments. According to this study, the right bank of the riverbank is more prone to erosion as compared to its left bank, and the existing infrastructural works have deep-rooted impacts upon the morphology of the river. The research recommends, on the basis of those findings, strategic placement of new groynes along the right bank to reduce erosion, underlining that proper design and maintenance are critical for the long-term functionality of such protective structures in managing this dynamic, braided river system. (Compaoré et al.) have proposed a new hybridization approach wherein the MOMA-Plus method is combined with the Differential Evolution method with improved convergence, without loss of diversity in solutions, for solving several multi-objective optimization problems. In this hybridized approach, efficiency is illustrated by showing an evaluation process over several test problems that evidences the capacity of hybridization to improve the convergence of the MOMA-Plus method, maintaining solution diversity, and encourages development for which new metaheuristics are solicited to solve this kind of complex optimization problem. These numerical studies show the importance of numerical investigations to better understand the interaction between groins, flow patterns, and erosion control measures. If one considers their placement, shape, and spacing, for instance, this gives rise to the possibility of optimizing the design and implementation of these structures for effective strategies in river management and erosion mitigation. This research is aimed at finding out the optimum groyne configuration for preventing bank erosion along the Ghezel-Ozan River in Iran using numerical simulations. The primary objectives of this study are to evaluate the effects of various groyne parameters, spacing, length, number, and their orientation on flow pattern and probable erosion. The research usesFLOW3D software to find the best arrangement of groynes in mitigating bank erosion by analyzing key hydrodynamic parameters, including Turbulent Kinetic Energy, Overall Flow Velocity, and Froude Number. In this paper, the performances with respect to both perpendicular and angled groynes and a different number of groynes with regard to their consequences for flow characteristic conditions and efficiency regarding erosion control have been modeled and compared. Ultimately, it delivers practical insights that will be of utility in the management of rivers and erosion-preventing strategies within similar hydraulic environments. 2. Materials and methods 2.1. Modeling and meshing using FLOW3D In the present research, the simulation of groynes was carried out using Flow3D software. This is a useful computational fluid dynamics model that works appropriately with complex fluid problems, especially three-dimensional, unsteady flows going along with a free surface and intricate geometries. In Flow3D, the governing equations are solved by the FVM. It considers different techniques for fluid volume detection; among them, this work used the automatic fluid volume method. It sets a partial fill amount for the cells of a free surface flow, stating what fraction each cell of the flow is filled with water. Friction no-slip conditions at the wall interface were assumed by the research study. In performing meshing for models, Flow3D allows the use of blocks, which can, in turn, be discretized into finer cells; this flexibility thereby accommodates the detail of replicating complex geometries. All the governing equations for incompressible, viscous fluid flow are represented by the continuity equation and the Navier-Stokes equation, Eqs. ( 1 ) and ( 2 ), respectively (Hirt & Nichols, 1988 ). Then, the developed rigorous modeling methodology gives valuable insights into the hydrodynamic behavior of the river systems with groynes, and the proper management of rivers in such cases is possible. This software is ideal for studying the complex interactions between permeable groynes and river flow due to the ability of the applied software to deal with complex fluid dynamics problems, along with advanced meshing capabilities and robust governing equations (Chabokpour & Azamathulla, 2022 ). $$\frac{\partial \rho }{\partial t}+\frac{\partial u}{\partial x}+\frac{\partial v}{\partial y}+\frac{\partial w}{\partial z}=0$$ 1 $$\frac{\partial {u}_{i}}{\partial t}+u\frac{\partial {u}_{i}}{\partial x}+v\frac{\partial {u}_{i}}{\partial y}+w\frac{\partial {u}_{i}}{\partial z}= -\frac{1}{\rho }\frac{\partial p}{\partial {x}_{i}}+\frac{\partial g}{\partial {x}_{i}}+\frac{\mu }{\rho }\left(\frac{{\partial }^{2}{u}_{i}}{\partial {x}^{2}}+\frac{{\partial }^{2}{u}_{i}}{\partial {y}^{2}}+\frac{{\partial }^{2}{u}_{i}}{\partial {z}^{2}}\right)$$ 2 Where: ρ represents the fluid density, u, v, and w are the velocities in the principal directions, p denotes pressure, g is the gravitational acceleration, and µ is the dynamic viscosity. These parameters form the core of the governing equations for incompressible, viscous fluid flow, namely the continuity equation and the Navier-Stokes equation. The continuity equation ensures the mass conservation of the fluid, the other, through the Navier-Stokes equation, describes how momenta within the fluid are balanced due to various forcing: pressure gradients, viscous forces, and gravity. Together, these two form a complete mathematical description of fluid behavior, which allows for an accurate simulation of complex flow situations as they occur in river systems with permeable groynes. In this study, a numerical model was used to simulate the flow pattern and groyne construction effect in different scenarios. The geometry of the model is shown in Fig. 1 . It is a 3000-m-long, 1000-m-wide, and 100-m-deep real river channel. Upstream and downstream boundary conditions have been set to have a specified water surface elevation. For the flow domain discretization, a computational mesh with 800,000 elements was used, as shown in Fig. 2 . By using such a detailed numerical approach to the scouring process at the groyne structure, the real hydraulic behavior and possible erosion patterns of such a system will be narrowed down. This also requires a fine resolution in the model and, importantly, properly defined boundary conditions that enable nuanced understanding of the complex processes of interaction between water flow and sediment transport, contributing to appropriate design and management strategies for similar hydraulic structures. 2.2. Conventional relationships for design of groyne Three critical parameters in regard to the design of groynes are spacing, S, and length, L, and width, W, which define the effectiveness and stability of the structure. Traditionally, groyne spacing is determined with reference to the groyne length using empirical ratios, normally varying between 2L and 5L. More detailed methods, however, include Lane's Equation and the Ackers and White Formula, which use variables that include average flow velocity ( \({V}_{\text{a}\text{v}\text{g} }\) ); median bed material size ( \({\text{d}}_{50}\) ), and sediment transport rate ( \({q}_{s}\) ). The variables just mentioned can be used in estimating the ideal groyne spacing S by (Kang et al., 2006 ; Koutrouveli et al., 2019 ; Mao et al., 2023 ). Hence, groyne spacing S can be estimated using Eqs. 1 , 2 . Lane's Equation : This formula relates groyne spacing to the average flow velocity ( \({V}_{\text{a}\text{v}\text{g} }\) ), median grain size of bed material ( \({\text{d}}_{50}\) ), and a coefficient (K) $$S= \text{K} \times ({{V}_{\text{a}\text{v}\text{g} }\times {\text{d}}_{50})}^{0.5}$$ 1 where K is typically between 5 and 10. Ackers and White Formula : This formula considers the influence of both flow velocity and sediment transport rate $$S= 15\times \frac{{\left({V}_{\text{a}\text{v}\text{g} } \times {\text{d}}_{50}\right)}^{0.5}}{{{q}_{s}}^{0.25}}$$ 2 where \({q}_{s}\) is the sediment transport rate (m³/s). In the traditional approaches, groyne length is usually defined with respect to the level of bank protection to be achieved or the active channel width. More sophisticated methods, like the Van Rijn Formula and the Ackers and White Formula, make use of flow velocity, sediment characteristics, and transport rates for the estimation. Most of the formulae have coefficients, K, which might be calibrated respecting local conditions and design requirements Eqs. 3 , 4 . Van Rijn Formula : This formula relates groyne length to the average flow velocity ( \({V}_{\text{a}\text{v}\text{g} }\) ), median grain size of bed material ( \({\text{d}}_{50}\) ), and a coefficient (K) $$L= \text{K} \times ({{V}_{\text{a}\text{v}\text{g} }\times {\text{d}}_{50})}^{0.5}$$ 3 where K is typically between 2 and 5. Ackers and White Formula : This formula considers the influence of both flow velocity and sediment transport rate: $$S= 10\times \frac{{\left({V}_{\text{a}\text{v}\text{g} } \times {\text{d}}_{50}\right)}^{0.5}}{{{q}_{s}}^{0.25}}$$ 4 Groynes width are usually estimated based on stability criteria against flow forces and sediment erosion. Similar to the case of estimating the length, the Van Rijn Formula and the Ackers and White Formula can be used in connection with the flow velocity, sediment characteristics, and transport rates for determining groyne width. These formulae give some additional detail on the approach to groyne design, which might be used to optimize the structures with regard to specific river conditions and management objectives Eqs. 5 , 6 . Van Rijn Formula : This formula relates groyne width to the average flow velocity ( \({V}_{\text{a}\text{v}\text{g} }\) ), median grain size of bed material ( \({\text{d}}_{50}\) ), and a coefficient (K) $$L= \text{K} \times ({{V}_{\text{a}\text{v}\text{g} }\times {\text{d}}_{50})}^{0.25}$$ 5 where K is typically between 2 and 5. Ackers and White Formula : This formula considers the influence of both flow velocity and sediment transport rate: $$W= 5\times \frac{{\left({V}_{\text{a}\text{v}\text{g} } \times {\text{d}}_{50}\right)}^{0.25}}{{{q}_{s}}^{0.25}}$$ 6 2.3. Field study area The second-longest river of Iran is the Ghezel-Ozan or Red River, which has its source in the Chehel Cheshme Mountains between Saqqez and Divandarreh in Kurdistan Province. It forms a very vital waterway that flows across several provinces, such as Zanjan, Gilan, Qazvin, Ardabil, East Azerbaijan, West Azerbaijan, and Kurdistan. A number of long rivers flow into this river; the major ones are Shahrchayi, Gharanghu Chayi, Aydoghmush, Heyrow, Zanjan, and Shahrud rivers. In its course through the western, northwestern, and northern parts of Zanjan Province, the Ghezel-Ozan receives a number of smaller rivers and streams. On approaching Mianeh, it absorbs the rivers Gharanghu, Aydoghmush, and Hashtrud before it flows further to the east. It enters the Khalkhāl district at 37°30′N latitude and 48°05′E longitude, where several more tributaries enter it from Darband Meshkul. Ultimately, it empties into the Sepid Rud Reservoir, located in the southern part of Gilan Province, and joins the Sefid Rud River to flow into the Caspian Sea. The Ghezel-Ozan is one of the most important fluvial systems with regard to hydrology and ecology in NW Iran, as it passes through several provinces and a wide variety of landscapes (Fig. 3 ). One of the important rivers in Iran is the Ghezel-Ozan River, with a basin area of 5000 square kilometers. The river training project was in the area of Eshtibin—a district in the East Azarbaijan Province. This river training project is supposed to solve the problems created by the Ghezel-Ozan River in the Eshtibin region. The strategies to be used in the project control and manage the possible risk of flooding or erosion, at the same time as ensuring there is a sustainable management of the river system. This important 3-kilometer reach will ensure protection for local communities and infrastructure from the impacts of the river's dynamics. The design flood discharge with a 25-year return period in the Eshtibin area was estimated to be 1435 cubic meters per second. Previously, studies have computed the roughness coefficient values over various cross-sections through the SCS method. In the present case study, the mean roughness coefficient is found to be 0.033. Since the area of the Ghezel-Ozan River is sensitive, these groynes were built only with stone materials, where they formed junctions with the longitudinal embankment at right angles (Fig. 4 ). As part of mesh generation, the bathymetric values were extracted from AutoCAD to ensure their compatibility with the Surface-water Modeling System. Simulations were carried out to gain mesh independence, considered important for putting out reliable results from numerical models. The simulations ran for 2 hours so that the models would reach a steady-state condition to ensure the numerical stability and convergence. It ensured a correct simulation of the hydrodynamic behavior of the river. It thus provided very good grounds for subsequent analyses and, therefore, forms the core for any future decision-making process in the study. Comprehensive data collection and mesh generation procedures in this study, with due consideration to critical factors such as flood discharges, water elevations, and topographic features, increase the reliability and applicability of numerical model. This stringent methodology opens the gate to detailed investigations in the field and developing effective strategies for river management. From the calculations of Eqs. 1 – 6 , the following is expected concerning groyne characteristics, a groyne length of L = 0.0616B is selected. The spacing considered were 2.8 and 3.6 times the groyne length with a number of groynes ranging from 4 through 7 units. The spacing used are at two angular variations: perpendicular and 30 degrees, facing the downstream area. The different scenarios for groyne placement were summarized in Table 1 . This kept things organized, and then it was possible to move on and look more thoroughly at the effects of several groyne placement parameters: distance between structures, number of groynes, and angular orientation with respect to the river flow. By exploring these diverse scenarios, the study aimed to identify the optimal groyne placement strategies for effective river management and erosion control. The systematic variation of parameters and the consideration of multiple configurations provide valuable insights into the complex interactions between groynes, flow patterns, and riverbank stability, ultimately contributing to the development of informed decision-making processes for river engineering projects. Table 1 Groyne placement scenario Discharge \(\left({\text{Q}}_{25}\right)\) \(\frac{{\text{m}}^{3}}{\text{s}}\) Groyne position Number of groyne (N-Unit) 4 7 Groyne spacing (m) 75 150 1435 Perpendicular \({90}^{\circ }\) \(\text{G}\text{T}\) GT4L75 GT7L150 Downstream \({30}^{\circ }\) GI GI4L75 GI7L150 In order to validate this numerical model, the Manning's roughness coefficient, n, was calibrated. The validation was carried out by comparing the measured and numerical velocities at two cross-sectional points: upstream, the first, and downstream, the second. The measured velocities at the first and second cross-sections were 1.08 m/s and 1.19 m/s, respectively. In comparison, the numerical velocities obtained in these two corresponding cross-sections were 1.248 m/s and 1.412 m/s. 3. Results In this work, three parameters have been utilized in representing the flow dynamics: the Turbulent Kinetic Energy, TKE, defined by Eq. 7 , the Overall Flow Velocity, OV, defined by Eq. 8 , and the Froude Number, Fr, defined by Eq. 9 . TKE is half of the summed squared fluctuating velocity components, u', v', w', which provides the mean kinetic energy as a result of velocity fluctuations. It means that the overall flow velocity, OV, is taken to be the square root of the squared sum of the mean velocity components; thus, it becomes a full measure of flow magnitude. The Froude Number, Fr, is a dimensionless parameter indicative of the relative significance of inertial to gravitational forces and is computed as the ratio of OV to the square root of the product of gravitational acceleration, g, by characteristic flow depth, h. These parameters comprehensively describe flow characteristics and thus allow for an in-depth analysis of turbulence, velocity distribution, and flow regimes. In this respect, these metrics embed valuable insights into the complex hydrodynamics of the groyne structure, underpinning a nuanced appreciation of the scouring processes and resultant impacts on the system's overall performance and stability (Wilcox, 1998 ). $$\text{T}\text{K}\text{E} = (1/2) \times ({\text{u}{\prime }}^{2}+ {\text{v}{\prime }}^{2} + {\text{w}{\prime }}^{2})$$ 7 Where: \(\text{T}\text{K}\text{E}\) is the turbulent kinetic energy (m²/s²), u' is the fluctuating component of the horizontal velocity (m/s), v' is the fluctuating component of the vertical velocity (m/s), w' is the fluctuating component of the transverse velocity (m/s). $$\text{O}\text{V}= \sqrt{({\text{u}{\prime }}^{2}+ {\text{v}{\prime }}^{2} + {\text{w}{\prime }}^{2})}$$ 8 where: \(\text{O}\text{V}\) is the overall flow velocity (m/s), u is the mean horizontal velocity (m/s), v is the mean vertical velocity (m/s), w is the mean transverse velocity (m/s). $$\text{F}\text{r}= \text{O}\text{V} / \sqrt{(\text{g} \times \text{h})}$$ 9 where: Fr is the Froude number, OV is the overall flow velocity (m/s), g is the acceleration due to gravity (9.81 m/s²), h is the characteristic flow depth (m) Figure 5 shows a computer-generated model of the Qezil Ozan River flow patterns with velocity distribution. Color coded contours indicate various flow velocities, where the warmer colors reflect higher and cooler colors reflect lower velocities. Streamlines are also superimposed on top to indicate the direction of water flow inside the river channel. It can be seen that the highest magnitude values of velocities are still confined to the main channel of the river because water can flow freely along the middle of the channel, having a minimal frictional resistance from the banks and bed of the river. On the contrary, the flow velocities decrease towards the riverbanks because of the frictional interaction of the flowing water with the banks that leads to loss of energy and consequent reduction in velocity. Local variations in flow velocity occur around obstacles or irregularities in the bed; accordingly, swirls or eddies in the streamline pattern represent turbulence and localized disruptions in flow. Knowing the flow velocity distribution, therefore, those areas in the river channel prone to erosion can be pointed out. The flow velocities at outer bends of the river channel are concentrated and may cause scouring, resulting in sediment removal and leading to bank erosion. Furthermore, narrow sections of flow and regions that include points downstream of obstacles are equally vulnerable to erosion due to the possibility that channel narrowing or obstacle presence can be the cause of a local gaining in speed, thus enhancing the potential erosive power of the water. Similarly, eddy formation assessment is found to create eddies, represented by swirling patterns in stream lines, formed in areas of flow separation and turbulence. The reason for these eddies is mostly related to the obstacles and irregularities that the bed of the river and its banks have, which disrupt the smooth flow of water and result in a change in direction and huge variations of flow velocities, creating swirls.. Figure 6 is showing TKE distribution and velocity vectors. Color-coded contours indicate the TKE varying between different values according to their intensity. Warmer colors show the higher and cooler colors the lower TKE values. Velocity vectors are further superimposed in the view, showing the direction and magnitude of the water flow in the river channel. Analysis of the TKE distribution indicates that the largest values concentrate near the obstacles or irregularities in the riverbed. This is due to an increase in turbulence and energy dissipation through a breakdown in smooth flow patterns. Large velocity gradients across the adjacent water layers form shear zones that also illustrate high TKE values, evidenced by bands of warm colors next to the riverbanks and at the transition between the main channel and near-bank flow. Generally, the deeper pools within the river channel hold lower TKE values because they are least affected by surface turbulence and energy dissipation. Based on the TKE distribution, what may be identified as locations prone to erosion would be those areas having high TKE, since vigorous turbulence and large shear stresses can dislodge sediments and cause the erosion of riverbanks and beds. Further, swallowing currents, turbulence, and energy dissipation occur in the downstream areas of obstacles and bends with high TKE, and thus localized erosion can also be expected. Eddy formation assessment has shown that eddies form at the sites of flow separation or wherever there is turbulence, as indicated by swirling patterns in velocity vectors. Eddies are usually attached to obstacles and irregularities on a riverbed, abrupt changes in flow direction, and high-shear zones whose dissimilar velocities of interaction create localized Turbulence and a rotational flow. Figure 7 shows Computer-aided model of Qezil Ozan River flow patterns, Froude number distribution, and velocity vectors. From the Fr distribution analysis, it can be understood that most of the areas prone to erosion in the river channel are located at the outer bends of supercritical flow regions. In these areas, high flow velocities may scour the outer banks due to the formation of secondary currents, causing bank erosion. Moreover, downstream of obstacles, hydraulic jumps or standing waves arising at the transition from supercritical to subcritical flow can locally erode and displace sediments, creating scour holes. Also, only in the case of tectonically or topographically-induced narrowing or constrictions in the river channel or due to artificial obstacles, there might be a danger of localized increases of flow velocity and the associated gain in erosive energy, which would eventually lead to erosion. The swirling patterns of velocity vectors represent the simulation of eddy formations, indicating that the eddies obviously form at the site of flow separation and turbulence. In most cases, they are attached to obstacles and irregularities of the riverbed that disrupt the smooth flow of water to eventually form localized turbulence and a rotational flow. Moreover, sharp changes in flow direction can result in eddy formation at such features as bends or confluences due to the inertia of the flowing water, which resists a sudden change in direction. In addition, transition areas from supercritical to subcritical flow, most commonly bends or near obstacles, may further foster eddy formation as a result of confused flow patterns and turbulence connected with such areas. Figure 8 shows two various flow patterns of Qezil Ozan River in the presence and absence of longitudinal groins, which are structures installed perpendicular to the shoreline for erosion control. Figure 8 (a) – without a groin; Fig. 8 (b) – after construction of six groins along the right bank of the river. In Fig. 8 (a), the flow velocities are typically the smallest within the main channel, evidenced through dense streamlines, and the warmer color tones. As one goes towards the river banks, the velocities are smaller, as shown through the cooler color tones and thinner streamlines. Velocity variations come up around the bends with higher velocities on the outer bends and lower on the inner bends. In this case, outer bends, downstream of obstacles, and areas of flow constriction are all prone to erosion. Eddy formations are mainly related to the presence of obstacles and irregularities in the riverbed, sudden changes in flow direction, and zones of high shear. Whereas in Fig. 8 (b) the addition of groynes fundamentally changes the flows. Groynes create localized perturbations in the flow field precipitating velocity fluctuations along the channel. In general, flow velocities normally increase on the upstream side and decrease on the downstream side of a groyne. The velocities then gradually return to their original values with decreasing groyne influence. While groynes can induce sedimentation and hence reduce erosion on the upstream side, scour holes could form on the downstream side as a result of increases in flow velocity and ensuing turbulence. Furthermore, groynes are able to alter the erosion pattern along the riverbank and may cause erosion at locations, which would otherwise be less susceptible to erosion. In terms of eddy formation, groynes themselves introduce localized eddies through the disruption of flow around them, and downstream of the groynes, increased turbulence and eddies are formed as a result of these structures' complicated flow patterns. Further, it is possible to form shear zones at greater distances around groynes and in the area between the groynes and the riverbank, possibly leading to eddy formation. Figure 9 shows diversifying flow patterns in Qezil Ozan River with an installed number of groynes on the right bank for erosion control. Figure 9 (a) shows the condition in the case of four groynes, and Fig. 9 (b) shows the effects with seven groynes installed. For both these cases, the highest flow velocities will be limited to the main channel, as indicated by the closely spaced streamlines and warmer color tones. It is observed that the velocities in flow increase at the upstream side of the groins and decrease at the downstream side, before increasing again as the effects of the groin weaken. However, as shown in Fig. 9 (b), the more intense localized disturbances in the flow due to the added groins, result in more dramatic changes in velocity along the channel than in the other case. In all such cases, scour holes can be expected to form downstream of groynes due to localized increases in flow velocity and turbulence. Similarly, upstream of groynes, sediment aggrading may be caused, which may reduce erosion in those areas. Consequently, this causes a deflection of the erosion distribution along the riverbank and probably causes erosion in regions that would not have been strong before. This effect would be more profound with six groynes in Fig. 9 (b) than four groynes in Fig. 9 (a). The modification or breaking of flow pattern within the vicinity of the groynes is considered due to eddy turbulence formation, with eddies most highly explicit in the downstream of groynes because of the complex flow pattern. Shear zones can be created around groynes and between the groynes and riverbank, that could create eddies in both cases. Nonetheless, the presence of six groins in Figure (b) might generate more energetic eddies and long-lasting ones than those four groins in Fig. 9 (a). 4. Conclusion This comprehensive numerical study on groyne configurations to prevent bank erosion along the Ghezel-Ozan River has shed light on the complex hydraulic structure-river dynamics interaction. By using advanced computational fluid dynamics modeling with FLOW3D software, this study has been able to clarify the influence of various parameters of groins on flow pattern, velocity distribution, and erosion potential. The following key findings were deduced from the TKE, OV, and Fr distributions in the different groyne scenarios: most importantly, the introduction of groynes changes the flow regime inside the river channel by significantly producing zones with reduced velocity and higher sediment deposition upstream of the structures. This effect is most pronounced within the near-bank regions where serious erosion control efforts are usually focused. It is demonstrated that the spacing of groynes will be the critical factor in modifying flow and, hence, the efficacy of bank protection. A comparison of the orientations of a perpendicular and angled groyne (30 degrees downstream) has revealed that each confers advantages with respect to different river characteristics and modes of erosion. Perpendicular groynes showed better performance in deflecting the main flow from the bank and creating zones of reduced velocity, which are larger when compared with those created by angled groynes. However, angled groynes of 30 degrees performed better in terms of promoting deposition and reducing scour at the tips—a very critical consideration for long-term structural stability. The variation of the number of groynes from 4 to 7 units enlightened the optimum density of the structures, which in this research is 4 units required for bank protection. While generally improving control of the erosion, increasing the number of groynes also increased flow pattern complexity and potentially had a downstream impact. In terms of determining the appropriate number of groynes, a balanced approach was proposed by the study, in which local protection would be weighed against the broader impacts on the river system. From the Froude number distributions, it can already be stated that groins may hence induce transitions between subcritical and supercritical flow states, in particular near the structures. For sediment transport and local scour, such phase transitions are very relevant. Hence, hydraulic conditions have very sensitive functions during the design and emplacement of groins. The study indicates that, even though the groynes are effective in reducing near-bank velocities, they can induce areas of enhanced turbulence and possible scour at their tips and in gaps between structures. It underlines that appropriate scour protection measures should be provided in groyne design and that morphological changes of the river bed over time need to be considered. The research has practical implications with regard to the site-specific consideration of groyne design and its implementation. In this sense, the optimal configuration found for the Ghezel-Ozan River, 4 units with distances of 150 and a length of 140, pointed 30 degrees, might be directly applicable to other river systems in similar rivers of the respective region. Declarations Conflicts of interest: No potential conflict of interest was reported by the authors. Availability of data and material: The datasets generated during and/or analyzed during the current study is available from the corresponding author on reasonable request Code availability : Not applicable Authors' contributions: Data analysis, Conception or design of the work, simulation interpretation, drafting the article Ethics approval: Not applicable Consent to participate : Not applicable Consent for publication: Not applicable Funding: Not applicable References Asahi K, Shimizu Y, Nelson J, Parker G (2013) Numerical simulation of river meandering with self-evolving banks. J Geophys Research: Earth Surf 118(4):2208–2229 Chabokpour J, Azamathulla HM (2022) Numerical simulation of pollution transport and hydrodynamic characteristics through the river confluence using FLOW 3D. Water Supply 22(10):7821–7832 Chabokpour J, Raji M (2024) Predicting Morphological Changes in Rivers Using Image Processing (Case Study: Qizil Ouzan River). J Hydraulic Struct, 10 (2) Chabokpour J, Zabihi M (2019) Evaluation of the transfer function method in the flood routing of the river reaches. J Hydraulics 14(2):145–158 Compaoré A, Som A, Somé K (2023) A NEW HYBRIDIZATION FOR IMPROVING THE CONVERGENCE OF THE MOMA-PLUS METHOD. Advances in Mathematics, 12(8), 701–718. Fatimah E, Fauzi A, Rezeki S, Suryati S (2020) Numerical simulation of groyne placement in minimising Krueng Aceh river bank erosion. IOP Conference Series: Materials Science and Engineering Gao S, Cao Y, Bai Y, Yang Y (2023) Flow Structure and Short-Term Riverbed Evolution in Curved Flumes. Fluid Dynamics Mater Process, 19 (2) Hasan MZ, Toda Y (2024) Enhancing Riverbank Protection along the Jamuna River, Bangladesh: Review of Previous Countermeasures and Morphological Assessment through Groyne-Based Solutions Using Numerical Modeling. Water 16(2):297 Hirt C, Nichols B (1988) Flow-3D User’s manual. Flow Science Inc , 107 Kang JG, Yeo HK, Roh YS (2006) An experimental study on a characteristics of flow around groynes for groyne spacing. KSCE J Civil Environ Eng Res 26(3B):271–278 Khajenoori L, Wright G, Crapper M (2017) Simulating geobag revetment failure processes, 37 edn. IAHR World Congress Korovkin V (2015) Numerical simulation of the reconstruction bank-protection type grillage on canals and rivers of St. Petersburg. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference Koutrouveli TI, Dimas AA, Fourniotis NT, Demetracopoulos AC (2019) Groyne spacing role on the effective control of wall shear stress in open-channel flow. J Hydraul Res 57(2):167–182 Lee S, Dang T (2018) Experimental investigation and numerical simulation of morphological changes in natural channel bend. J Appl Fluid Mech 11(3):721–731 LUU LX, EGASHIRA, S., TAKEBAYASHI H (2004) Investigation of Tan Chau reach in lower Mekong using field data and numerical simulation. Proceedings of Hydraulic Engineering , 48 , 1057–1062 Mao X, Liu X, Xie C, Xu Z, Huang J, Li H, Lei N, Wang S, Wang L, Chen S (2023) Research on the Protective Effect of Twin-groyne Arrangement on Riverbank. Stavební obzor-Civil Eng J 32(4):457–467 Masbahul IM, Yorozuya A, Harada D, Egashira S (2022) A numerical study on bank erosion of a braided channel: case study of the Tangail and Manikganj districts along the Brahmaputra River. J Disaster Res 17(2):263–269 Mojtahedi A, Basmenji AB (2017) Numerical and field investigation of the impacts of the bank protection projects on the fluvial hydrodynamics (case study: Ghezel Ozan River). Int J Eng Technol 9(6):492 Onda S, Shirai H, Hosoda T, Arimitsu T, Ooe K (2010) Numerical simulation of river channel processes with bank erosion in steep curved channel. River Flow Vigna S, Marchelli M, De Biagi V, Peila D (2023) Numerical Simulation of Rockfall Protection Embankments in Natural Soil. Geosciences 13(12):368 Wilcox DC (1998) Turbulence modeling for CFD, vol 2. DCW industries La Canada, CA Zhang XL, Sun DP, Zhang FR (2011) Research on the Numerical Simulation of Silting in Floodplain and Scouting in Main Channel of Over-Bank Flooding in the Lower Yellow River. Adv Mater Res 255:3692–3696 Zulfan J, Ginting B, Hidayat M, Rimawan R (2021) Finding the optimum groin layout for the Konaweha river banks protection via 2D numerical modeling. IOP Conference Series: Earth and Environmental Science Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4623183","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":322479118,"identity":"595d0e44-3459-4be3-b9c7-f5877fe02721","order_by":0,"name":"Jafar 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18:25:54","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1382942,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic of Eshtibin area in Ghezel-Ozan river for groyne structures construction to prevent bank erosion\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/49fda4d75e99c764cc2f2561.png"},{"id":61348937,"identity":"bb65846b-351f-4d27-a73e-dbf7544fb383","added_by":"auto","created_at":"2024-07-29 18:25:54","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":723215,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOverall flow magnitude and streamline orientation through the Qezil Ozan River without groyne construction\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/11bf66e89f94079b038ee800.png"},{"id":61349703,"identity":"10445fc2-c3db-4e45-b6e2-ac6dd7f36731","added_by":"auto","created_at":"2024-07-29 18:33:54","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":265063,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTurbulent kinetic energy and velocity vector formation through the Qezil Ozan River without groyne construction\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/a2065ab87762b055e25b41f0.jpeg"},{"id":61347673,"identity":"1759d93e-67ec-4cf9-8aa5-62b23fbcc9c3","added_by":"auto","created_at":"2024-07-29 18:17:54","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":280015,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFr number and velocity vector formation through the Qezil Ozan River without groyne construction\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/8fb27b98184114b99fa0ff17.jpeg"},{"id":61347676,"identity":"3d60fd18-e4eb-40c7-9685-9849ef8aaeef","added_by":"auto","created_at":"2024-07-29 18:17:54","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1044709,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) Overall flow magnitude and streamline orientation through the Qezil Ozan River without groyne construction (b) Overall flow magnitude and streamline orientation through the Qezil Ozan River with 7 perpendicular groynes construction\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/61514f836c5148ed9d4fd43e.png"},{"id":61347675,"identity":"a7167a81-e2aa-49bd-b0db-19595f934eea","added_by":"auto","created_at":"2024-07-29 18:17:54","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":876669,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) Overall flow magnitude and streamline orientation through the Qezil Ozan River with 4 perpendicular groyne construction (b) Overall flow magnitude and streamline orientation through the Qezil Ozan River with 7 perpendicular groynes construction\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/dd270e4c4fffe65ea87e2a6f.png"},{"id":61705292,"identity":"b118574e-43b5-403c-bcbf-5038909cc00c","added_by":"auto","created_at":"2024-08-03 19:39:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5945726,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4623183/v1/637eef6f-9aad-429a-a4d8-7e81a75223f6.pdf"}],"financialInterests":"","formattedTitle":"Numerical simulation of optimum groyne arrangement for preventing bank erosion (Case study of Ghezel-Ozan River)","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eA groyne is a structure that is placed transverse to the flow of a river to manage river bank erosion by diverting flow from the river bank. A groyne can be made out of various material like stone, concrete, wood, or a gabion. Groyne work by altering the flow away from the bank side, as flow is diverted sediment deposition begins, which leads to the stabilization of the river bank. Groyne effectiveness may depend on the dimensions of the groyne, which are groyne length, flow deflection angle, and groyne spacing. The groyne length should be long enough for the groyne to deflect flow, though not too long that excessive scour occurs at the groyne head. The flow deflection angle is designed to maximize sediment deposition and minimize bank side erosion. Groyne spacing should be close enough to protect the bank entirely, but not so close, which reduces the upstream sedimentation or impedes flow promoting further erosion. Overall, groynes are generally considered a cost effective protection system for river banks. Groynes can have adverse effects on the river system including but are not limited to changing river morphology and disrupting riparian habitats. Therefore, it is important to evaluate potential impacts before using groins (Chabokpour \u0026amp; Raji, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Chabokpour \u0026amp; Zabihi, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e(LUU et al., 2004) has conducted the research applying a newly developed numerical model and field data analysis to understanding the changes of river channel in the study site, Tan Chau reach of Mekong River in Vietnam. The research results show that bank erosion on the left bank was the main of channel shifting under the influence of a lot of factors such as sediment composition (because inorganic and organic sediments have the different strength) bankline protection measures, flow patterns (meandering, straight), formation of sandbar, and shape of the channel developed. This created numerical model considers the processes including channel shifting and bank erosion are cohesive sediment erosion and sand transport by bedload layer thickness that changed and partly explain the process of channel shifting. In order to evaluate channel erosion and floodplain deposition patterns, (Zhang et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) used a 2D numerical model to simulate water flow and sediment transport and investigate the consequences of overbank flooding on the Lower Yellow River. The study demonstrates that larger floods do not always correlate with increased main channel erosion and that there is a non-linear relationship between sediment concentration and floodplain deposition. The relationship between flood magnitude, sediment concentration, and erosion/deposition processes is complex. The results indicate that the best flood control plans for maintaining channels rely on the specific circumstances, emphasizing the necessity for customized methods to river management and urging more investigation to overcome model constraints and improve comprehension of these intricate fluvial processes.\u003c/p\u003e \u003cp\u003e(Asahi et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) introduced a novel computer model that incorporates the intricate relationships between flow dynamics, sediment transport, and bank erosion-deposition processes to simulate the long-term evolution of meandering rivers. The model takes into account variables like vegetation growth and flood events and integrates a number of components, including flow equations, bed evolution tracking, and bank erosion prediction. Even with certain oversimplifications, the model provides insightful information about the development and evolution of river meanders, which may be useful in projects involving river engineering and flood management.\u003c/p\u003e \u003cp\u003e(Onda et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) presented a numerical model that included a depth-averaged flow model with equilibrium and non-equilibrium sediment transport models, as well as a simplified bank failure model, to simulate river channel processes with bank erosion in steep curved channels. The study highlights the significance of non-equilibrium sediment transport conditions near river banks for improved accuracy and shows how the model can replicate important features seen in experimental settings, such as point bar formation and riverbed scouring. Nevertheless, the authors acknowledge that additional refinement is required to address complex interactions between flow, sediment transport, and bank erosion in order to improve the model's overall predictive capabilities.\u003c/p\u003e \u003cp\u003e(Korovkin, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) addressed the drawbacks of conventional methods by modeling soil stiffness and treating piles as flexible, rotatable rods in order to provide an inventive way for calculating pile foundation embankments in urban waterfront renovation projects. Through a case study of a St. Petersburg waterfront that has been rebuilt, the study illustrates the improved accuracy of this new approach, contrasting its outcomes with those attained through conventional methods and emphasizing its potential to more closely mimic the behavior of pile foundation structures in the real world. The effectiveness of several building techniques for geobag revetments in preventing erosion along riverbanks was examined by (Khajenoori et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The results showed that the arrangement of the geobags in stacks had little bearing on the overall performance of the revetment. In order to mimic geobag revetment failure, the researchers created a computer model. This model has the potential to be a useful tool for designing future geobag revetments and help create riverbank protection techniques that are more effective. (Mojtahedi \u0026amp; Basmenji, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) used the MIKE21-FM numerical model to simulate flow patterns around groynes to test the effectiveness of these structures as riverbank protection structures on Iran's Ghezel-Ozan River, specifically in Achachi. These results suggest that groynes, especially L-shaped designs, can be very effective tools for protecting riverbank erosion. The research shows that groynes successfully diverted the main river flow away from the banks, effectively protecting agricultural land from erosion. L-shaped groynes proved particularly effective at deflecting flow and reducing scouring at the groyne's headland. (Lee \u0026amp; Dang, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) introduced a novel numerical model that uses a mixed grain size method for bed load representation in order to mimic morphological changes in natural channel bends. The model shows a considerable improvement over earlier uniform grain size models and has been tested using both laboratory and field data. It solves shallow water equations and sediment transport equations to anticipate bed level variations. With its more accurate portrayal of intricate channel dynamics, this sophisticated simulation tool has the potential to improve river management and flood control tactics by providing useful forecasting skills for river behavior and morphology. In a 575-meter section of the Krueng Aceh River in Indonesia, where bridge development has disturbed the river's natural flow patterns, (Fatimah et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) investigated the effectiveness of groynes in reducing bank erosion. The study assesses different groyne structures to maximize flow redirection and erosion reduction at the outer river bend using numerical simulations via the Surface Water Modelling System (SMS 11.2). The results of the study show that strategically placed groynes can effectively deflect water velocity from the bank. The study concluded that the best balance between velocity reduction and minimal eddy formation is achieved by a 7-meter groyne angled at 10 degrees, though the ideal design parameters depend on the particular conditions of the river. The optimal design for groynes (riverbank protection structures) for Indonesia's Konaweha River was studied by (Zulfan et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).The effect of groynes on water flow and erosion was simulated by the researchers using a computer model (2D numerical modeling). After testing sixteen various groyne designs, they discovered that the ones that reduced water flow velocity and stopped erosion along the outer riverbank were those with five structures separated twice as long as the groyne itself. In their research of bank erosion in braided channels, (Masbahul et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) used numerical simulations to identify vulnerable spots and the Brahmaputra River as a case study. Sandbar development and watercourse modifications are examples of small-scale events that are integrated into a model that the researchers construct. Large-scale phenomena include the distribution of flow throughout several channels. In order to show that differences in flow distribution between channels can cause bank erosion, the model effectively reproduces observed channel patterns and sandbar formation. Higher flow rates in a single channel may cause the channel to widen and erode along its bank.\u003c/p\u003e \u003cp\u003e(Gao et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) used a mix of computer modeling and experimental data to study the flow structure and short-term riverbed change in curved flumes. The study revealed distorted water surfaces with greater levels on the convex bank and lower levels on the concave bank, coupled with complicated flow patterns in curved flumes that are characterized by secondary circulation and longitudinal velocity differences across the channel width. The results shed important light on the hydrodynamics of curved rivers by showing how flow patterns affect the evolution of bed topography, including scouring upstream of convex banks and deposition downstream. They also emphasize the impact of living vegetation on flow patterns and the severity of bed scouring, which helps to improve river channel design and management techniques.\u003c/p\u003e \u003cp\u003e(Vigna et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) performed detailed studies on RPEs (rockfall protection embankments) composed of natural soil. In the process, finite element method simulations assessed their performance against the rock impact. The identification of key failure mechanisms, design tools, and factors that influence the performance of RPEs were evaluated, improving the deficiencies inherent in the existing methodologies. It contributes key findings toward the development of more sophisticated design strategies for RPEs made from natural soils that will eventually be deployed in mountainous areas for mitigation purposes against rockfall hazards.\u003c/p\u003e \u003cp\u003e(Hasan \u0026amp; Toda, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) considered the riverbank protection works on the Jamuna River in Bangladesh. In this regard, a 50 km reach was analyzed with the iRIC Nays2DH numerical modeling. The research evaluates several past countermeasures\u0026mdash;for example, embankments, hard points groynes, and revetments. According to this study, the right bank of the riverbank is more prone to erosion as compared to its left bank, and the existing infrastructural works have deep-rooted impacts upon the morphology of the river. The research recommends, on the basis of those findings, strategic placement of new groynes along the right bank to reduce erosion, underlining that proper design and maintenance are critical for the long-term functionality of such protective structures in managing this dynamic, braided river system.\u003c/p\u003e \u003cp\u003e(Compaor\u0026eacute; et al.) have proposed a new hybridization approach wherein the MOMA-Plus method is combined with the Differential Evolution method with improved convergence, without loss of diversity in solutions, for solving several multi-objective optimization problems. In this hybridized approach, efficiency is illustrated by showing an evaluation process over several test problems that evidences the capacity of hybridization to improve the convergence of the MOMA-Plus method, maintaining solution diversity, and encourages development for which new metaheuristics are solicited to solve this kind of complex optimization problem.\u003c/p\u003e \u003cp\u003eThese numerical studies show the importance of numerical investigations to better understand the interaction between groins, flow patterns, and erosion control measures. If one considers their placement, shape, and spacing, for instance, this gives rise to the possibility of optimizing the design and implementation of these structures for effective strategies in river management and erosion mitigation. This research is aimed at finding out the optimum groyne configuration for preventing bank erosion along the Ghezel-Ozan River in Iran using numerical simulations. The primary objectives of this study are to evaluate the effects of various groyne parameters, spacing, length, number, and their orientation on flow pattern and probable erosion. The research usesFLOW3D software to find the best arrangement of groynes in mitigating bank erosion by analyzing key hydrodynamic parameters, including Turbulent Kinetic Energy, Overall Flow Velocity, and Froude Number. In this paper, the performances with respect to both perpendicular and angled groynes and a different number of groynes with regard to their consequences for flow characteristic conditions and efficiency regarding erosion control have been modeled and compared. Ultimately, it delivers practical insights that will be of utility in the management of rivers and erosion-preventing strategies within similar hydraulic environments.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Modeling and meshing using FLOW3D\u003c/h2\u003e \u003cp\u003eIn the present research, the simulation of groynes was carried out using Flow3D software. This is a useful computational fluid dynamics model that works appropriately with complex fluid problems, especially three-dimensional, unsteady flows going along with a free surface and intricate geometries. In Flow3D, the governing equations are solved by the FVM. It considers different techniques for fluid volume detection; among them, this work used the automatic fluid volume method. It sets a partial fill amount for the cells of a free surface flow, stating what fraction each cell of the flow is filled with water. Friction no-slip conditions at the wall interface were assumed by the research study. In performing meshing for models, Flow3D allows the use of blocks, which can, in turn, be discretized into finer cells; this flexibility thereby accommodates the detail of replicating complex geometries. All the governing equations for incompressible, viscous fluid flow are represented by the continuity equation and the Navier-Stokes equation, Eqs.\u0026nbsp;(\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and (\u003cspan refid=\"Equ4\" class=\"InternalRef\"\u003e2\u003c/span\u003e), respectively (Hirt \u0026amp; Nichols, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). Then, the developed rigorous modeling methodology gives valuable insights into the hydrodynamic behavior of the river systems with groynes, and the proper management of rivers in such cases is possible. This software is ideal for studying the complex interactions between permeable groynes and river flow due to the ability of the applied software to deal with complex fluid dynamics problems, along with advanced meshing capabilities and robust governing equations (Chabokpour \u0026amp; Azamathulla, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\frac{\\partial \\rho }{\\partial t}+\\frac{\\partial u}{\\partial x}+\\frac{\\partial v}{\\partial y}+\\frac{\\partial w}{\\partial z}=0$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\frac{\\partial {u}_{i}}{\\partial t}+u\\frac{\\partial {u}_{i}}{\\partial x}+v\\frac{\\partial {u}_{i}}{\\partial y}+w\\frac{\\partial {u}_{i}}{\\partial z}= -\\frac{1}{\\rho }\\frac{\\partial p}{\\partial {x}_{i}}+\\frac{\\partial g}{\\partial {x}_{i}}+\\frac{\\mu }{\\rho }\\left(\\frac{{\\partial }^{2}{u}_{i}}{\\partial {x}^{2}}+\\frac{{\\partial }^{2}{u}_{i}}{\\partial {y}^{2}}+\\frac{{\\partial }^{2}{u}_{i}}{\\partial {z}^{2}}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere: ρ represents the fluid density, u, v, and w are the velocities in the principal directions, p denotes pressure, g is the gravitational acceleration, and \u0026micro; is the dynamic viscosity. These parameters form the core of the governing equations for incompressible, viscous fluid flow, namely the continuity equation and the Navier-Stokes equation. The continuity equation ensures the mass conservation of the fluid, the other, through the Navier-Stokes equation, describes how momenta within the fluid are balanced due to various forcing: pressure gradients, viscous forces, and gravity. Together, these two form a complete mathematical description of fluid behavior, which allows for an accurate simulation of complex flow situations as they occur in river systems with permeable groynes. In this study, a numerical model was used to simulate the flow pattern and groyne construction effect in different scenarios. The geometry of the model is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. It is a 3000-m-long, 1000-m-wide, and 100-m-deep real river channel. Upstream and downstream boundary conditions have been set to have a specified water surface elevation. For the flow domain discretization, a computational mesh with 800,000 elements was used, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. By using such a detailed numerical approach to the scouring process at the groyne structure, the real hydraulic behavior and possible erosion patterns of such a system will be narrowed down. This also requires a fine resolution in the model and, importantly, properly defined boundary conditions that enable nuanced understanding of the complex processes of interaction between water flow and sediment transport, contributing to appropriate design and management strategies for similar hydraulic structures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Conventional relationships for design of groyne\u003c/h2\u003e \u003cp\u003eThree critical parameters in regard to the design of groynes are spacing, S, and length, L, and width, W, which define the effectiveness and stability of the structure. Traditionally, groyne spacing is determined with reference to the groyne length using empirical ratios, normally varying between 2L and 5L. More detailed methods, however, include Lane's Equation and the Ackers and White Formula, which use variables that include average flow velocity (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({V}_{\\text{a}\\text{v}\\text{g} }\\)\u003c/span\u003e\u003c/span\u003e); median bed material size (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{d}}_{50}\\)\u003c/span\u003e\u003c/span\u003e), and sediment transport rate (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{s}\\)\u003c/span\u003e\u003c/span\u003e). The variables just mentioned can be used in estimating the ideal groyne spacing S by (Kang et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Koutrouveli et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Mao et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Hence, groyne spacing S can be estimated using Eqs.\u0026nbsp;\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Equ4\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eLane's Equation\u003c/b\u003e: This formula relates groyne spacing to the average flow velocity (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({V}_{\\text{a}\\text{v}\\text{g} }\\)\u003c/span\u003e\u003c/span\u003e), median grain size of bed material (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{d}}_{50}\\)\u003c/span\u003e\u003c/span\u003e), and a coefficient (K)\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003cdiv id=\"Equ3\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$S= \\text{K} \\times ({{V}_{\\text{a}\\text{v}\\text{g} }\\times {\\text{d}}_{50})}^{0.5}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ewhere K is typically between 5 and 10.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eAckers and White Formula\u003c/b\u003e: This formula considers the influence of both flow velocity and sediment transport rate\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003cdiv id=\"Equ4\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$S= 15\\times \\frac{{\\left({V}_{\\text{a}\\text{v}\\text{g} } \\times {\\text{d}}_{50}\\right)}^{0.5}}{{{q}_{s}}^{0.25}}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{s}\\)\u003c/span\u003e\u003c/span\u003e is the sediment transport rate (m\u0026sup3;/s).\u003c/p\u003e \u003cp\u003eIn the traditional approaches, groyne length is usually defined with respect to the level of bank protection to be achieved or the active channel width. More sophisticated methods, like the Van Rijn Formula and the Ackers and White Formula, make use of flow velocity, sediment characteristics, and transport rates for the estimation. Most of the formulae have coefficients, K, which might be calibrated respecting local conditions and design requirements Eqs.\u0026nbsp;\u003cspan refid=\"Equ5\" class=\"InternalRef\"\u003e3\u003c/span\u003e, \u003cspan refid=\"Equ6\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eVan Rijn Formula\u003c/b\u003e: This formula relates groyne length to the average flow velocity (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({V}_{\\text{a}\\text{v}\\text{g} }\\)\u003c/span\u003e\u003c/span\u003e), median grain size of bed material (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{d}}_{50}\\)\u003c/span\u003e\u003c/span\u003e), and a coefficient (K)\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003cdiv id=\"Equ5\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$L= \\text{K} \\times ({{V}_{\\text{a}\\text{v}\\text{g} }\\times {\\text{d}}_{50})}^{0.5}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ewhere K is typically between 2 and 5.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eAckers and White Formula\u003c/b\u003e: This formula considers the influence of both flow velocity and sediment transport rate:\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003cdiv id=\"Equ6\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ6\" name=\"EquationSource\"\u003e\n$$S= 10\\times \\frac{{\\left({V}_{\\text{a}\\text{v}\\text{g} } \\times {\\text{d}}_{50}\\right)}^{0.5}}{{{q}_{s}}^{0.25}}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eGroynes width are usually estimated based on stability criteria against flow forces and sediment erosion. Similar to the case of estimating the length, the Van Rijn Formula and the Ackers and White Formula can be used in connection with the flow velocity, sediment characteristics, and transport rates for determining groyne width. These formulae give some additional detail on the approach to groyne design, which might be used to optimize the structures with regard to specific river conditions and management objectives Eqs.\u0026nbsp;\u003cspan refid=\"Equ7\" class=\"InternalRef\"\u003e5\u003c/span\u003e, \u003cspan refid=\"Equ8\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eVan Rijn Formula\u003c/b\u003e: This formula relates groyne width to the average flow velocity (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({V}_{\\text{a}\\text{v}\\text{g} }\\)\u003c/span\u003e\u003c/span\u003e), median grain size of bed material (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{d}}_{50}\\)\u003c/span\u003e\u003c/span\u003e), and a coefficient (K)\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003cdiv id=\"Equ7\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ7\" name=\"EquationSource\"\u003e\n$$L= \\text{K} \\times ({{V}_{\\text{a}\\text{v}\\text{g} }\\times {\\text{d}}_{50})}^{0.25}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ewhere K is typically between 2 and 5.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eAckers and White Formula\u003c/b\u003e: This formula considers the influence of both flow velocity and sediment transport rate:\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003cdiv id=\"Equ8\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ8\" name=\"EquationSource\"\u003e\n$$W= 5\\times \\frac{{\\left({V}_{\\text{a}\\text{v}\\text{g} } \\times {\\text{d}}_{50}\\right)}^{0.25}}{{{q}_{s}}^{0.25}}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Field study area\u003c/h2\u003e \u003cp\u003eThe second-longest river of Iran is the Ghezel-Ozan or Red River, which has its source in the Chehel Cheshme Mountains between Saqqez and Divandarreh in Kurdistan Province. It forms a very vital waterway that flows across several provinces, such as Zanjan, Gilan, Qazvin, Ardabil, East Azerbaijan, West Azerbaijan, and Kurdistan. A number of long rivers flow into this river; the major ones are Shahrchayi, Gharanghu Chayi, Aydoghmush, Heyrow, Zanjan, and Shahrud rivers. In its course through the western, northwestern, and northern parts of Zanjan Province, the Ghezel-Ozan receives a number of smaller rivers and streams. On approaching Mianeh, it absorbs the rivers Gharanghu, Aydoghmush, and Hashtrud before it flows further to the east. It enters the Khalkhāl district at 37\u0026deg;30\u0026prime;N latitude and 48\u0026deg;05\u0026prime;E longitude, where several more tributaries enter it from Darband Meshkul. Ultimately, it empties into the Sepid Rud Reservoir, located in the southern part of Gilan Province, and joins the Sefid Rud River to flow into the Caspian Sea. The Ghezel-Ozan is one of the most important fluvial systems with regard to hydrology and ecology in NW Iran, as it passes through several provinces and a wide variety of landscapes (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOne of the important rivers in Iran is the Ghezel-Ozan River, with a basin area of 5000 square kilometers. The river training project was in the area of Eshtibin\u0026mdash;a district in the East Azarbaijan Province. This river training project is supposed to solve the problems created by the Ghezel-Ozan River in the Eshtibin region. The strategies to be used in the project control and manage the possible risk of flooding or erosion, at the same time as ensuring there is a sustainable management of the river system. This important 3-kilometer reach will ensure protection for local communities and infrastructure from the impacts of the river's dynamics. The design flood discharge with a 25-year return period in the Eshtibin area was estimated to be 1435 cubic meters per second. Previously, studies have computed the roughness coefficient values over various cross-sections through the SCS method. In the present case study, the mean roughness coefficient is found to be 0.033. Since the area of the Ghezel-Ozan River is sensitive, these groynes were built only with stone materials, where they formed junctions with the longitudinal embankment at right angles (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs part of mesh generation, the bathymetric values were extracted from AutoCAD to ensure their compatibility with the Surface-water Modeling System. Simulations were carried out to gain mesh independence, considered important for putting out reliable results from numerical models. The simulations ran for 2 hours so that the models would reach a steady-state condition to ensure the numerical stability and convergence. It ensured a correct simulation of the hydrodynamic behavior of the river. It thus provided very good grounds for subsequent analyses and, therefore, forms the core for any future decision-making process in the study. Comprehensive data collection and mesh generation procedures in this study, with due consideration to critical factors such as flood discharges, water elevations, and topographic features, increase the reliability and applicability of numerical model. This stringent methodology opens the gate to detailed investigations in the field and developing effective strategies for river management. From the calculations of Eqs.\u0026nbsp;\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Equ8\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the following is expected concerning groyne characteristics, a groyne length of L\u0026thinsp;=\u0026thinsp;0.0616B is selected. The spacing considered were 2.8 and 3.6 times the groyne length with a number of groynes ranging from 4 through 7 units. The spacing used are at two angular variations: perpendicular and 30 degrees, facing the downstream area. The different scenarios for groyne placement were summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This kept things organized, and then it was possible to move on and look more thoroughly at the effects of several groyne placement parameters: distance between structures, number of groynes, and angular orientation with respect to the river flow. By exploring these diverse scenarios, the study aimed to identify the optimal groyne placement strategies for effective river management and erosion control. The systematic variation of parameters and the consideration of multiple configurations provide valuable insights into the complex interactions between groynes, flow patterns, and riverbank stability, ultimately contributing to the development of informed decision-making processes for river engineering projects.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGroyne placement scenario\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDischarge\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\left({\\text{Q}}_{25}\\right)\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{{\\text{m}}^{3}}{\\text{s}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c3\" namest=\"c2\" rowspan=\"2\"\u003e \u003cp\u003eGroyne position\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNumber of groyne\u003c/p\u003e \u003cp\u003e(N-Unit)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroyne spacing (m)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1435\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePerpendicular\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({90}^{\\circ }\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{G}\\text{T}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGT4L75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGT7L150\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDownstream\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({30}^{\\circ }\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGI4L75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGI7L150\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn order to validate this numerical model, the Manning's roughness coefficient, n, was calibrated. The validation was carried out by comparing the measured and numerical velocities at two cross-sectional points: upstream, the first, and downstream, the second. The measured velocities at the first and second cross-sections were 1.08 m/s and 1.19 m/s, respectively. In comparison, the numerical velocities obtained in these two corresponding cross-sections were 1.248 m/s and 1.412 m/s.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eIn this work, three parameters have been utilized in representing the flow dynamics: the Turbulent Kinetic Energy, TKE, defined by Eq.\u0026nbsp;\u003cspan refid=\"Equ9\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the Overall Flow Velocity, OV, defined by Eq.\u0026nbsp;\u003cspan refid=\"Equ10\" class=\"InternalRef\"\u003e8\u003c/span\u003e, and the Froude Number, Fr, defined by Eq.\u0026nbsp;\u003cspan refid=\"Equ11\" class=\"InternalRef\"\u003e9\u003c/span\u003e. TKE is half of the summed squared fluctuating velocity components, u', v', w', which provides the mean kinetic energy as a result of velocity fluctuations. It means that the overall flow velocity, OV, is taken to be the square root of the squared sum of the mean velocity components; thus, it becomes a full measure of flow magnitude. The Froude Number, Fr, is a dimensionless parameter indicative of the relative significance of inertial to gravitational forces and is computed as the ratio of OV to the square root of the product of gravitational acceleration, g, by characteristic flow depth, h.\u003c/p\u003e \u003cp\u003eThese parameters comprehensively describe flow characteristics and thus allow for an in-depth analysis of turbulence, velocity distribution, and flow regimes. In this respect, these metrics embed valuable insights into the complex hydrodynamics of the groyne structure, underpinning a nuanced appreciation of the scouring processes and resultant impacts on the system's overall performance and stability (Wilcox, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1998\u003c/span\u003e).\u003cdiv id=\"Equ9\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ9\" name=\"EquationSource\"\u003e\n$$\\text{T}\\text{K}\\text{E} = (1/2) \\times ({\\text{u}{\\prime }}^{2}+ {\\text{v}{\\prime }}^{2} + {\\text{w}{\\prime }}^{2})$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\text{T}\\text{K}\\text{E}\\)\u003c/span\u003e \u003c/span\u003e is the turbulent kinetic energy (m\u0026sup2;/s\u0026sup2;), u' is the fluctuating component of the horizontal velocity (m/s), v' is the fluctuating component of the vertical velocity (m/s), w' is the fluctuating component of the transverse velocity (m/s).\u003cdiv id=\"Equ10\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ10\" name=\"EquationSource\"\u003e\n$$\\text{O}\\text{V}= \\sqrt{({\\text{u}{\\prime }}^{2}+ {\\text{v}{\\prime }}^{2} + {\\text{w}{\\prime }}^{2})}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e8\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\text{O}\\text{V}\\)\u003c/span\u003e \u003c/span\u003e is the overall flow velocity (m/s), u is the mean horizontal velocity (m/s), v is the mean vertical velocity (m/s), w is the mean transverse velocity (m/s).\u003cdiv id=\"Equ11\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ11\" name=\"EquationSource\"\u003e\n$$\\text{F}\\text{r}= \\text{O}\\text{V} / \\sqrt{(\\text{g} \\times \\text{h})}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e9\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere:\u003c/p\u003e \u003cp\u003eFr is the Froude number, OV is the overall flow velocity (m/s), g is the acceleration due to gravity (9.81 m/s\u0026sup2;), h is the characteristic flow depth (m)\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows a computer-generated model of the Qezil Ozan River flow patterns with velocity distribution. Color coded contours indicate various flow velocities, where the warmer colors reflect higher and cooler colors reflect lower velocities. Streamlines are also superimposed on top to indicate the direction of water flow inside the river channel. It can be seen that the highest magnitude values of velocities are still confined to the main channel of the river because water can flow freely along the middle of the channel, having a minimal frictional resistance from the banks and bed of the river. On the contrary, the flow velocities decrease towards the riverbanks because of the frictional interaction of the flowing water with the banks that leads to loss of energy and consequent reduction in velocity. Local variations in flow velocity occur around obstacles or irregularities in the bed; accordingly, swirls or eddies in the streamline pattern represent turbulence and localized disruptions in flow. Knowing the flow velocity distribution, therefore, those areas in the river channel prone to erosion can be pointed out. The flow velocities at outer bends of the river channel are concentrated and may cause scouring, resulting in sediment removal and leading to bank erosion. Furthermore, narrow sections of flow and regions that include points downstream of obstacles are equally vulnerable to erosion due to the possibility that channel narrowing or obstacle presence can be the cause of a local gaining in speed, thus enhancing the potential erosive power of the water. Similarly, eddy formation assessment is found to create eddies, represented by swirling patterns in stream lines, formed in areas of flow separation and turbulence. The reason for these eddies is mostly related to the obstacles and irregularities that the bed of the river and its banks have, which disrupt the smooth flow of water and result in a change in direction and huge variations of flow velocities, creating swirls..\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e is showing TKE distribution and velocity vectors. Color-coded contours indicate the TKE varying between different values according to their intensity. Warmer colors show the higher and cooler colors the lower TKE values. Velocity vectors are further superimposed in the view, showing the direction and magnitude of the water flow in the river channel. Analysis of the TKE distribution indicates that the largest values concentrate near the obstacles or irregularities in the riverbed. This is due to an increase in turbulence and energy dissipation through a breakdown in smooth flow patterns. Large velocity gradients across the adjacent water layers form shear zones that also illustrate high TKE values, evidenced by bands of warm colors next to the riverbanks and at the transition between the main channel and near-bank flow. Generally, the deeper pools within the river channel hold lower TKE values because they are least affected by surface turbulence and energy dissipation. Based on the TKE distribution, what may be identified as locations prone to erosion would be those areas having high TKE, since vigorous turbulence and large shear stresses can dislodge sediments and cause the erosion of riverbanks and beds. Further, swallowing currents, turbulence, and energy dissipation occur in the downstream areas of obstacles and bends with high TKE, and thus localized erosion can also be expected. Eddy formation assessment has shown that eddies form at the sites of flow separation or wherever there is turbulence, as indicated by swirling patterns in velocity vectors. Eddies are usually attached to obstacles and irregularities on a riverbed, abrupt changes in flow direction, and high-shear zones whose dissimilar velocities of interaction create localized Turbulence and a rotational flow.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows Computer-aided model of Qezil Ozan River flow patterns, Froude number distribution, and velocity vectors. From the Fr distribution analysis, it can be understood that most of the areas prone to erosion in the river channel are located at the outer bends of supercritical flow regions. In these areas, high flow velocities may scour the outer banks due to the formation of secondary currents, causing bank erosion. Moreover, downstream of obstacles, hydraulic jumps or standing waves arising at the transition from supercritical to subcritical flow can locally erode and displace sediments, creating scour holes. Also, only in the case of tectonically or topographically-induced narrowing or constrictions in the river channel or due to artificial obstacles, there might be a danger of localized increases of flow velocity and the associated gain in erosive energy, which would eventually lead to erosion. The swirling patterns of velocity vectors represent the simulation of eddy formations, indicating that the eddies obviously form at the site of flow separation and turbulence. In most cases, they are attached to obstacles and irregularities of the riverbed that disrupt the smooth flow of water to eventually form localized turbulence and a rotational flow. Moreover, sharp changes in flow direction can result in eddy formation at such features as bends or confluences due to the inertia of the flowing water, which resists a sudden change in direction. In addition, transition areas from supercritical to subcritical flow, most commonly bends or near obstacles, may further foster eddy formation as a result of confused flow patterns and turbulence connected with such areas.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e shows two various flow patterns of Qezil Ozan River in the presence and absence of longitudinal groins, which are structures installed perpendicular to the shoreline for erosion control. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a) \u0026ndash; without a groin; Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b) \u0026ndash; after construction of six groins along the right bank of the river.\u003c/p\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a), the flow velocities are typically the smallest within the main channel, evidenced through dense streamlines, and the warmer color tones. As one goes towards the river banks, the velocities are smaller, as shown through the cooler color tones and thinner streamlines. Velocity variations come up around the bends with higher velocities on the outer bends and lower on the inner bends. In this case, outer bends, downstream of obstacles, and areas of flow constriction are all prone to erosion. Eddy formations are mainly related to the presence of obstacles and irregularities in the riverbed, sudden changes in flow direction, and zones of high shear. Whereas in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b) the addition of groynes fundamentally changes the flows. Groynes create localized perturbations in the flow field precipitating velocity fluctuations along the channel. In general, flow velocities normally increase on the upstream side and decrease on the downstream side of a groyne. The velocities then gradually return to their original values with decreasing groyne influence. While groynes can induce sedimentation and hence reduce erosion on the upstream side, scour holes could form on the downstream side as a result of increases in flow velocity and ensuing turbulence. Furthermore, groynes are able to alter the erosion pattern along the riverbank and may cause erosion at locations, which would otherwise be less susceptible to erosion. In terms of eddy formation, groynes themselves introduce localized eddies through the disruption of flow around them, and downstream of the groynes, increased turbulence and eddies are formed as a result of these structures' complicated flow patterns. Further, it is possible to form shear zones at greater distances around groynes and in the area between the groynes and the riverbank, possibly leading to eddy formation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e shows diversifying flow patterns in Qezil Ozan River with an installed number of groynes on the right bank for erosion control. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a) shows the condition in the case of four groynes, and Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (b) shows the effects with seven groynes installed. For both these cases, the highest flow velocities will be limited to the main channel, as indicated by the closely spaced streamlines and warmer color tones. It is observed that the velocities in flow increase at the upstream side of the groins and decrease at the downstream side, before increasing again as the effects of the groin weaken. However, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (b), the more intense localized disturbances in the flow due to the added groins, result in more dramatic changes in velocity along the channel than in the other case. In all such cases, scour holes can be expected to form downstream of groynes due to localized increases in flow velocity and turbulence. Similarly, upstream of groynes, sediment aggrading may be caused, which may reduce erosion in those areas. Consequently, this causes a deflection of the erosion distribution along the riverbank and probably causes erosion in regions that would not have been strong before. This effect would be more profound with six groynes in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (b) than four groynes in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a). The modification or breaking of flow pattern within the vicinity of the groynes is considered due to eddy turbulence formation, with eddies most highly explicit in the downstream of groynes because of the complex flow pattern. Shear zones can be created around groynes and between the groynes and riverbank, that could create eddies in both cases. Nonetheless, the presence of six groins in Figure (b) might generate more energetic eddies and long-lasting ones than those four groins in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a).\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis comprehensive numerical study on groyne configurations to prevent bank erosion along the Ghezel-Ozan River has shed light on the complex hydraulic structure-river dynamics interaction. By using advanced computational fluid dynamics modeling with FLOW3D software, this study has been able to clarify the influence of various parameters of groins on flow pattern, velocity distribution, and erosion potential. The following key findings were deduced from the TKE, OV, and Fr distributions in the different groyne scenarios: most importantly, the introduction of groynes changes the flow regime inside the river channel by significantly producing zones with reduced velocity and higher sediment deposition upstream of the structures. This effect is most pronounced within the near-bank regions where serious erosion control efforts are usually focused.\u003c/p\u003e \u003cp\u003eIt is demonstrated that the spacing of groynes will be the critical factor in modifying flow and, hence, the efficacy of bank protection. A comparison of the orientations of a perpendicular and angled groyne (30 degrees downstream) has revealed that each confers advantages with respect to different river characteristics and modes of erosion. Perpendicular groynes showed better performance in deflecting the main flow from the bank and creating zones of reduced velocity, which are larger when compared with those created by angled groynes. However, angled groynes of 30 degrees performed better in terms of promoting deposition and reducing scour at the tips\u0026mdash;a very critical consideration for long-term structural stability. The variation of the number of groynes from 4 to 7 units enlightened the optimum density of the structures, which in this research is 4 units required for bank protection. While generally improving control of the erosion, increasing the number of groynes also increased flow pattern complexity and potentially had a downstream impact. In terms of determining the appropriate number of groynes, a balanced approach was proposed by the study, in which local protection would be weighed against the broader impacts on the river system. From the Froude number distributions, it can already be stated that groins may hence induce transitions between subcritical and supercritical flow states, in particular near the structures. For sediment transport and local scour, such phase transitions are very relevant. Hence, hydraulic conditions have very sensitive functions during the design and emplacement of groins. The study indicates that, even though the groynes are effective in reducing near-bank velocities, they can induce areas of enhanced turbulence and possible scour at their tips and in gaps between structures. It underlines that appropriate scour protection measures should be provided in groyne design and that morphological changes of the river bed over time need to be considered. The research has practical implications with regard to the site-specific consideration of groyne design and its implementation. In this sense, the optimal configuration found for the Ghezel-Ozan River, 4 units with distances of 150 and a length of 140, pointed 30 degrees, might be directly applicable to other river systems in similar rivers of the respective region.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflicts of interest:\u003c/strong\u003e No potential conflict of interest was reported by the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material:\u003c/strong\u003e The datasets generated during and/or analyzed during the current study is available from the corresponding author on reasonable request\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability\u003c/strong\u003e: Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions:\u003c/strong\u003e\u0026nbsp; Data analysis, Conception or design of the work, simulation interpretation, drafting the article\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval:\u003c/strong\u003e\u0026nbsp; Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e: Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e Not applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAsahi K, Shimizu Y, Nelson J, Parker G (2013) Numerical simulation of river meandering with self-evolving banks. J Geophys Research: Earth Surf 118(4):2208\u0026ndash;2229\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChabokpour J, Azamathulla HM (2022) Numerical simulation of pollution transport and hydrodynamic characteristics through the river confluence using FLOW 3D. Water Supply 22(10):7821\u0026ndash;7832\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChabokpour J, Raji M (2024) Predicting Morphological Changes in Rivers Using Image Processing (Case Study: Qizil Ouzan River). J Hydraulic Struct, \u003cem\u003e10\u003c/em\u003e(2)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChabokpour J, Zabihi M (2019) Evaluation of the transfer function method in the flood routing of the river reaches. J Hydraulics 14(2):145\u0026ndash;158\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCompaor\u0026eacute; A, Som A, Som\u0026eacute; K (2023) A NEW HYBRIDIZATION FOR IMPROVING THE CONVERGENCE OF THE MOMA-PLUS METHOD. \u003cem\u003eAdvances in Mathematics, 12(8), 701\u0026ndash;718.\u003c/em\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFatimah E, Fauzi A, Rezeki S, Suryati S (2020) Numerical simulation of groyne placement in minimising Krueng Aceh river bank erosion. IOP Conference Series: Materials Science and Engineering\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGao S, Cao Y, Bai Y, Yang Y (2023) Flow Structure and Short-Term Riverbed Evolution in Curved Flumes. 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IOP Conference Series: Earth and Environmental Science\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ghezel-Ozan River, groyne arrangement, FLOW3D software, hydrodynamic parameters","lastPublishedDoi":"10.21203/rs.3.rs-4623183/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4623183/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper will discuss the optimum groyne configuration for preventing bank erosion alongside the Ghezel-Ozan River in Iran through advanced numerical simulations. The research used FLOW3D software to investigate the effects of spacing, lengths, the number, and the orientation of groins on flow patterns and erosion potential. In this regard, some key hydrodynamic parameters, such as Turbulent Kinetic Energy, Overall Flow Velocity, and Froude Number, are analyzed to quantify the efficacy of various groyne arrangements. The study area, belonging to the Eshtibin region of East Azarbaijan Province, is a 3-kilometer segment of the river, with a design flood discharge of 1435 m3/s for a 25-year return period. Coupled with detailed mesh (with 800,000 elements) and bathymetric data, this numerical model is to be used to represent as exactly as possible the morphology of the river. In this study, there are four groyne placement scenarios, showing the effect of number of groynes (4 or 7 units), spacing intervals (2.8 and 3.6 times the groyne length), and angular orientation (perpendicular and 30 degrees downstream). The results indicate that, upon the introduction of groynes, there are prominent changes in flow patterns and velocity distributions; therefore, this offers an avenue for erosion control. The study reveals that the optimal groyne configuration is dependent on site-specific conditions and design objectives, such as 4 number of groynes with 30 degrees orientation, stating tailored approaches are very important in river management strategies.\u003c/p\u003e","manuscriptTitle":"Numerical simulation of optimum groyne arrangement for preventing bank erosion (Case study of Ghezel-Ozan River)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-29 18:17:49","doi":"10.21203/rs.3.rs-4623183/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9a31c09b-0d97-4a92-8b8c-c487fd7b118e","owner":[],"postedDate":"July 29th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-08-03T19:31:34+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-29 18:17:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4623183","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4623183","identity":"rs-4623183","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}