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This study investigates the effectiveness of flow splitters in reducing scour downstream of trapezoidal Piano Key Weirs through a comprehensive experimental study. Three distinct geometries of flow splitters—square, rectangular, and circular—are examined under various hydraulic conditions to assess their impact on local scouring. The experiments were conducted in a dedicated channel measuring 10 m in length, 0.75 m in width, and 0.80 m in height. The results indicate that flow splitters facilitate flow separation by linking trapped air beneath the flow to the free surface, thereby mitigating nappe oscillation. Additionally, the geometric variations of flow splitters did not significantly influence the upstream water head, with rectangular-shaped flow splitters proving more effective than square and circular splitters. On average, the maximum scour depth for the weir with rectangular, square, and circular splitters is reduced by approximately 13, 11, and 10%, respectively, compared to the weir without splitters. Furthermore, the volume of scour holes in tests with rectangular, square, and circular splitters showed reductions of 18.53, 17.77, and 14.92%, respectively, compared to tests without splitters. As discharge decreases, the effectiveness of these flow splitters in reducing scour depth becomes more pronounced. Due to the existence of splitters, the location of maximum scour depth approaches the weir. New equations were developed for predicting scour hole parameters with and without flow splitters, incorporating various splitter geometries. These equations were formulated using non-linear regression, achieving high accuracy with a correction factor, yielding R2 values between 0.78 and 0.94, and RMSE values ranging from 0.09 to 0.54. Overall, the findings underscore the significance of flow splitter geometry in mitigating scour effects, providing valuable insights for future engineering applications. [ABSTRACT FROM AUTHOR]

Understanding and improving passage by diadromous species at tidal barriers is less well advanced than that for non-tidal anthropogenic river barriers. This study assessed factors affecting upstream passage of anadromous river lamprey (Lampetra fluviatilis) at a tidal weir with pool-and-weir (PAW) and bypass (BP) fishways. A Continuous Time Markov Model (CTMM) was used to analyse migration behaviours of 120 acoustic- and PIT-tagged lamprey across 2 years. The weir was a major barrier to upstream migration with a mean time of 31.0 days taken to pass the weir compared to 2.5 days for the unobstructed reach immediately downstream. River stage was the most important variable associated with weir passage, with a 5.68 (CI = 3.95, 8.17) increase in passage probability for every 1 m river stage increase. Passage was predominately over the weir directly rather than by the fishways. Monitoring the fishways using additional PIT-tagged lamprey (n = 2814) suggested poor entrance efficiency (BP2018, 28.6%; BP2019, 53.1%; PAW2018, 37.0%). Successful fishway passage was estimated as 5.4% (BP2019)–9.0% (PAW2018) of lamprey that entered. Effective fishway entrance for lamprey is probably facilitated by high fishway discharge, yet high-velocity areas may have made it difficult for river lamprey to successfully ascend the fishways. [ABSTRACT FROM AUTHOR]

Due to their superior technical and hydraulic performance and minimal environmental impact, porous weirs have emerged as a feasible alternative to traditional impermeable solid weirs in water transmission and distribution systems. This research study assesses the hydraulic performance of porous broad-crested weirs (PBCWs) with sloping crests. To accomplish this, 30 PBCW models were designed and tested under various operating conditions, including free and submerged flow scenarios. A comparative analysis was conducted to evaluate the performance of PBCWs with and without sloping crests, with the results being compared against a solid broad-crested weir (SBCW) model. The findings revealed that PBCWs with an upstream crest slope exhibited an average increase of 38% in the discharge coefficient compared to similar SBCWs. Similarly, PBCWs with a downstream crest slope demonstrated an average increase of 28% in the discharge coefficient. Additionally, PBCWs with sloping crests showcased heightened sensitivity to changes in tailwater levels compared to PBCWs with horizontal crests, with PBCWs featuring an upstream crest slope being more responsive than those with a downstream crest slope. Finally, leveraging extensive experimental data, empirical equations were derived using nonlinear multi-variable regression and gene-expression programming techniques to accurately represent the free flow discharge coefficient and submerged flow discharge reduction factor. [ABSTRACT FROM AUTHOR]

Herein, a novel filtering weir with multi-stepped orifices is proposed to solve the problem of ineffective removal of small inclusions with traditional flow control devices in tundishes. Without changing the installation position, three types of novel filtering weir were designed. The flow and heat transfer behavior, wall shear distribution of the weir and dam, and removal rate of inclusions with different sizes were compared and analyzed. A 1:0.4 scale water model was conducted to validate the flow field calculated by mathematical simulation. The results indicate that the filtering weir can extend the response time and promote the mixing of liquid steel, but has little impact on the residence time and dead volume fraction. Due to the influence of the flow, the near-wall velocity and wall shear stress of the weir and dam decrease, but the area of the low-temperature zone of liquid surface in tundishes increases. The multi-stepped orifices added on the weir increase the removal rate of inclusions below 50 μm, especially the removal rate of inclusion of 2 and 5 μm increases to 63 to 64 pct, which is 18 to 21 pct higher than that with a traditional weir. [ABSTRACT FROM AUTHOR]

Scour depth downstream of weirs is considered one of the most important hydraulic problems, which greatly influences the stability of weirs. Recently, artificial intelligence (AI) methods have become increasingly popular in modeling hydraulic variables, especially scour depth, because they can capture nonlinear relationships between input variables and their associated objectives. Despite their importance, these models have problems with hyperparameter tuning in scour depth modeling due to their structures, so algorithms must be used to tune the hyperparameters. Moreover, these algorithms are usually tuned by using the trial-and-error method to select the hyperparameters such as the number of hidden nodes, transfer function, and learning rate, and in this case, the main problem is overfitting during the training phase. To solve these problems, the high-order response surface method (HORSM), an improved version of the response surface method (RSM), is used as an alternative approach for the first time in this study to predict the scour depth. The HORSM model is based on high-order polynomial functions (from two to six) compared with the artificial neural network model (ANN). The findings indicate that the fifth order of the HORSM polynomial function yields the most precise predictions, with a higher coefficient of determination (R2) of 0.912 and Willmott Index (WI) of 0.972 compared to the values obtained using ANN (R2 = 0.886 and WI = 0.927). Moreover, the accuracy of the predictions is represented by a reduction of the mean square error by up to 44.17 and 29.01% compared to the classical RSM and ANN, respectively. The suggested model established an excellent correlation and accuracy with experimental values. [ABSTRACT FROM AUTHOR]

Two different arrangements of the weir (i.e., straight weir and rectangular labyrinth weir) were used to evaluate the effects of geometric parameters such as weir shape, weir spacing, presence of an orifice at the weir, and bed slope on the flow regime and the relationship between discharge and depth, variation and distribution of depth-averaged velocity, turbulence characteristics, and energy dissipation at the fishway. Computational fluid dynamics simulations were performed using FLOW-3D® software to examine the effects on flow conditions. The numerical model was validated by comparing the calculated surface profiles and velocities with experimentally measured values from the literature. The results of the numerical model and experimental data showed that the root-mean-square error and mean absolute percentage error for the surface profiles and normalized velocity profiles of plunging flows were 0.014 m and 3.11%, respectively, confirming the ability of the numerical model to predict the flow characteristics of the pool and weir. A plunging flow can occur at values of L/B = 1.83 (L: distance of the weir, B: width of the channel) and streaming flow at L/B = 0.61 for each model. The rectangular labyrinth weir model has larger dimensionless discharge values (Q+) than the conventional model. For the conventional weir and the rectangular labyrinth weir at submerged flow, Q is proportional to 1.56 and 1.47h, respectively (h: the water depth above the weir). The average depth velocity in the pool of a conventional weir is higher than that of a rectangular labyrinth weir. However, for a given discharge, bed slope, and weir spacing, the turbulent kinetic energy (TKE) and turbulence intensity (TI) values are higher for a rectangular labyrinth weir compared to conventional weir. The conventional weir has lower energy dissipation than the rectangular labyrinth weir. Lower TKE and TI values were observed at the top of the labyrinth weir, at the corner of the wall downstream of the weir, and between the side walls of the weir and the channel wall. As the distance between the weirs and the bottom slope increased, the average depth velocity, the average value of turbulent kinetic energy and the turbulence intensity increased, and the volumetric energy dissipation in the pool decreased. The presence of an opening in the weir increased the average depth velocity and TI values and decreased the range of highest TKE within the pool, resulted in larger resting areas for fish (lower TKE), and decreased the energy dissipation rates in both models. [ABSTRACT FROM AUTHOR]

When settlements are located close to a dam, it is important to accurately predict the breach peak flow and the time to reach the peak. Therefore, the prediction of dam breach properties is essential in dam break studies. Dam breach parameters such as the breach side slope, final bottom width, final bottom elevation, weir coefficient, breach formation time, and initial elevation of reservoirs are the key variables for estimating the peak discharge during a dam break scenario. In this study, these six breach parameters were analyzed to investigate the impact of breach parameters on breach peak flow and the time to reach the peak. Thus, several scenarios were calculated and compared for Atasu Dam. The results revealed that the role of the initial water elevation, final bottom elevation, and breach development time had more of an impact on the breach peak flow and the time to reach the peak. In addition, the study indicated that the final bottom width and breach weir coefficient were less sensitive to both the peak discharge and peak discharge time. Furthermore, the analysis indicated that the breach side slope parameter had no major influence on the time to peak while also having an insignificant impact on the peak discharge. Understanding this breach mechanism provides a basis for relevant research in designating key parameters for dam break analysis. Thus, the results can contribute to decision making toward the design of flood mitigation and dam emergency action planning. [ABSTRACT FROM AUTHOR]

The deduction of the weir flow stage-discharge relationship is a hydraulic problem generally solved by energy considerations and using the discharge coefficient to correct the gap between theoretical results and experimental measurements. In this context, the dimensional analysis represents an alternative to find simple and reliable equations to obtain the rating curve. In this study, the outflow process of vegetated weirs is investigated applying the Π-Theorem of dimensional analysis and the incomplete self-similarity theory. The aim of this paper is to propose a new theoretically-based stage-discharge relationship, and test its applicability by measurements recently published in the literature. The results showed that the errors in discharge estimate obtained by the proposed stage-discharge relationship are always less than or equal to ± 10% and less than or equal to ± 5% for 97–100% of cases. The main advantage of the proposed relationships is providing a single stage-discharge relationship, which has better performances than the equations reported in the literature and excludes the use of discharge coefficient. [ABSTRACT FROM AUTHOR]

European rivers are disconnected by more than one million man-made barriers that physically limit aquatic species migration and contribute to modification of freshwater habitats. Here, a Conceptual Habitat Alteration Model for Ponding is developed to aid in evaluating the effects of impoundments on fish habitats. Fish communities present in rivers with low human impact and their broad environmental settings enable classification of European rivers into 15 macrohabitat types. These classifications, together with the estimated fish sensitivity to alteration of their habitat are used for assessing the impacts of six main barrier types (dams, weirs, sluices, culverts, fords, and ramps). Our results indicate that over 200,000 km or 10% of previously free-flowing river habitat has been altered due to impoundments. Although they appear less frequently, dams, weirs and sluices cause much more habitat alteration than the other types. Their impact is regionally diverse, which is a function of barrier height, type and density, as well as biogeographical location. This work allows us to foresee what potential environmental gain or loss can be expected with planned barrier management actions in rivers, and to prioritize management actions. European rivers have over a million barriers hindering aquatic species migration and altering freshwater habitats. This study quantifies the spatial extent of upstream fish habitat alteration caused by physical blockage and shows that impoundments have altered 10% or 200,000 km of free-flowing river habitat in Europe. [ABSTRACT FROM AUTHOR]

This paper investigated the efficiency of the traditional weir equation (TWE), Domínguez, adjusted Domínguez, and Schmidt approaches, as an alternative to the De Marchi procedure, for computing discharge of a sharp-crested triangular side weir. Comprehensive experimental data were used for the analysis, including 342 data from the present study and 140 data from other sources. The effects of approach Froude number Fr1, the ratio of weir height to upstream flow depth p/y1, and weir apex angle θ on the discharge coefficients obtained from different methods were studied. Sensitivity analysis using the partial swarm optimization-support vector regression method indicated that Fr1, p/y1, and θ affect the discharge coefficients. It was found that Fr1 with sensitivity indices equal to 1.89, 3.74, and 4.04 has the most substantial effect on the De Marchi coefficient, TWE coefficient, and adjusted Domínguez coefficient; meanwhile, p/y1 has the most significant impact on Domínguez coefficient and Schmidt coefficient with sensitivity index equal to 1.57. In addition, it was found that θ had the lowest sensitivity indices in estimating discharge coefficients. New equations for forecasting sharp-crested triangular side weir discharge coefficient were presented based on dimensional analysis. The new De Marchi coefficient executed better for calculating triangular side weir discharge than earlier De Marchi coefficients. Moreover, TWE, Domínguez, adjusted Domínguez, and Schmidt methods performed better than the De Marchi procedure (with MSE = 4.581) in calculating sharp-crested triangular side weir discharge. However, considering the simplicity of the TWE approach compared to other methods, this approach with R2 = 0.975, NSE = 0.975, MSE = 3.610, MRE = 0.097, and CP10% = 71.36 was introduced as the superior procedure. [ABSTRACT FROM AUTHOR]

This study focuses on the experimental investigation of an inclined circular labyrinth weir with angles of inclination of 60, 70, 80, and 90 degrees. Additionally, the influence of different weir diameters (15, 20, 25, and 30 cm) under various flow rates on hydraulic performance and the discharge coefficient of the weirs were examined. Experimental results revealed that the flow over the weir initially exhibited a free flow type, transitioning to submerged flow as the flow rate increased. No air infiltration into the flow was observed. Moreover, an increase in the dimensionless ratio of the total hydraulic head to the inclined labyrinth weir's height led to a decrease in the discharge coefficient. The inclined weir with an angle of inclination of 60 degrees exhibited the highest discharge coefficient, while the vertical weir had the lowest coefficient. The analysis of weir diameter showed that although the initial highest discharge coefficient occurred at a 15 cm diameter, further variations in the discharge coefficients among different diameters were minimal, indicating an insignificant effect of weir diameter on the discharge coefficient. Overall, this study provides insights into the hydraulic behavior and discharge coefficient of inclined circular labyrinth weirs, contributing to the understanding and optimization of their performance in water management systems. [ABSTRACT FROM AUTHOR]

Weirs are hydraulic structures mostly used to measure the flow discharge and control the flow level in artificial or natural open channels. The ratio of the actual discharge to the theoretical discharge (discharge coefficient—Cd) must be known, in order to calculate the discharge of the channel having the weir. In this study, 91 experimental measurements are taken on seven trapezoidal broad-crested weirs with different upstream and downstream slopes. Experimentally measured flow properties are used to validate numerical models based on the computational fluid dynamics (CFD) methods. Two new weir geometries, not experimentally measured, are added in the numerical modeling, and 270 Cd values are calculated for nine weir geometries using numerical modeling. Theoretical Cd values are estimated using the artificial neural network (ANN), support vector machine (SVM), and M5Tree methods. In the models, the Froude number in the upstream region and dimensionless parameters of the flow are used as inputs. The performance of these methods has been examined to estimate the Cd values for eight cases. The performances of the methods are evaluated by the coefficient of determination (R2), root-mean-square error, mean absolute percentage error, and Nash–Sutcliffe model efficiency coefficient. The study results show that the Froude number significantly increases the performance of the models in estimating Cd values, and the ANN method is more successful in determining Cd than other methods. [ABSTRACT FROM AUTHOR]

One of the practical and financial solutions to increase the efficiency of weirs is to modify the geometry of the plan and increase the length of the weir to a specific width. This increases the discharge coefficient (Cd) of the weir. In this study, a new weir referred to pseudo-cosine labyrinth weir (PCLW) was introduced. A hybrid machine learning LXGB algorithm was introduced to estimate the Cd of the PCLW. The LXGB is a combination of the linear population size reduction history-based adaptive differential evolution (LSHADE) and extreme gradient boosting (XGB) algorithm. Seven different input scenarios were presented to estimate the discharge coefficient of the PCLW weir. To train and test the proposed method, 132 data series, including geometric and hydraulic parameters from PCLW1 and PCLW2 models were used. The root mean square error (RMSE), relative root mean square error (RRMSE), and Nash–Sutcliffe model efficiency coefficient (NSE) indices were used to evaluate the proposed approach. The results showed that the input variables were the ratio of the radius to the weir height (R/W), the ratio of the length of the weir to the weir height (L/W), and the ratio of the hydraulic head to the weir height (H/W), with the average values of RMSE = 0.009, RRMSE = 0.010, and NSE = 0.977 provided better results in estimating the Cd of PCLW1 and PCLW2 models. The improvement compared to SAELM, ANFIS-FFA, GEP, and ANN in terms of R2 is 2.06%, 3.09%, 1.03%, and 5.15%. In general, intelligent hybrid approaches can be introduced as the most suitable method for estimating the Cd of PCLW weirs. [ABSTRACT FROM AUTHOR]

In this study, the flow characteristics over modified semi-cylindrical weirs (MSCM) were investigated using computational fluid dynamics (CFD) simulations. The simulations included the analysis of flow velocity and pressure distribution, turbulence intensity, and streamline patterns. The numerical results were compared to laboratory observations, and a good agreement was observed. Different turbulence models, including renormalized group (RNG) k-ε, standard k-ε, k-ω two-equations, and large eddy simulation (LES), were evaluated, and all showed suitable performance in simulating the flow field and hydraulic characteristics. However, the standard k-ε model outperformed the other models. The analysis of streamline patterns from upstream to downstream of the weirs showed that the curve of the crest provided an opportunity for the flow to harmonize with the surface of the crest. The downstream ramp guided the streamlines, preventing collision with the downstream slab surface and vorticity formation. Additionally, the results indicated that adding the downstream ramp significantly reduced the turbulence intensity of the flow at the toe of the weirs. The analysis of pressure distribution showed that the flow departed from hydrostatic state when reaching the weir, and the maximum deviation occurred at the crest vertex. [ABSTRACT FROM AUTHOR]

Recently, weather data have been applied to one of deep learning techniques known as "long short-term memory (LSTM)" to predict streamflow in rainfall-runoff relationships. However, this approach may not be suitable for regions with artificial water management structures such as dams and weirs. Therefore, this study aims to evaluate the prediction accuracy of LSTM for streamflow depending on the availability of dam/weir operational data across South Korea. Four scenarios were prepared for 25 streamflow stations. Scenarios #1 and #2 used weather data and weather and dam/weir operational data, respectively, with the same LSTM model conditions for all stations. Scenarios #3 and #4 used weather data and weather and dam/weir operational data, respectively, with the different LSTM models for individual stations. The Nash–Sutcliffe efficiency (NSE) and the root mean squared error (RMSE) were adopted to assess the LSTM's performance. The results indicated that the mean values of NSE and RMSE were 0.277 and 292.6 (Scenario #1), 0.482 and 214.3 (Scenario #2), 0.410 and 260.7 (Scenario #3), and 0.592 and 181.1 (Scenario #4), respectively. Overall, the model performance was improved by the addition of dam/weir operational data, with an increase in NSE values of 0.182–0.206 and a decrease in RMSE values of 78.2–79.6. Surprisingly, the degree of performance improvement varied according to the operational characteristics of the dam/weir, and the performance tended to increase when the dam/weir with high frequency and great amount of water discharge was included. Our findings showed that the overall LSTM prediction of streamflow was improved by the inclusion of dam/weir operational data. When using dam/weir operational data to predict streamflow using LSTM, understanding of their operational characteristics is important to obtain reliable streamflow predictions. [ABSTRACT FROM AUTHOR]

During the recent decades, a number of overflow embankment protection systems were implemented. One design is the Minimum Energy Loss (MEL) weir, developed to pass large flood events with minimum energy loss and low erosion. Several MEL weirs have successfully operated for decades in Australian catchments affected by heavy tropical and sub-tropical rainfalls with very flat gradients. Their historical performances are discussed and confirmed the design capability to pass large floods with small afflux and very small energy loss and little environmental impact including no significant erosion at the abutments. During a major flood, visual and quantitative observations were undertaken at the Chinchilla MEL weir. On the smooth converging chute, the observations showed that the inception of self‐aeration was a three‐dimensional process with a gradual change in free‐surface roughness, from a smooth glassy free-surface to a very-rough choppy surface. An optical technique (OF) was implemented to derive the contour maps of surface velocities based upon video movies taken from a sturdy tripod. The self-aerated flow velocity data were close to the backwater equation in the self‐aerated region, while highlighting regions of high- and low-velocities across the chute. The OF data showed large streamwise surface velocity fluctuations in the aerated flow region, consistent with the broad literature on self-aerated flow measurements. The ratio of transverse to streamwise surface turbulence intensity indicated a strong anisotropy of the free-surface turbulence. Highlights: Minimum energy loss (MEL) weirs were developed for river catchment with heavy rainfall and very flat gradient. Field observations were performed at the Chinchilla MEL weir spillway in late 2021 during a major flood. Surface velocity data showed large transverse difference in longitudinal surface velocities across the chute [ABSTRACT FROM AUTHOR]

The paper's novelty is in combining two comparatively new fields of research: non-transitive logic and the proof method of correspondence analysis. To be more detailed, in this paper the latter is adapted to Weir's non-transitive trivalent logic NC 3 . As a result, for each binary extension of NC 3 , we present a sound and complete Lemmon-style natural deduction system. Last, but not least, we stress the fact that Avron and his co-authors' general method of obtaining n-sequent proof systems for any n-valent logic with deterministic or non-deterministic matrices is not applicable to NC 3 and its binary extensions. [ABSTRACT FROM AUTHOR]

Labyrinth side weirs have significant advantages according to conventional side weirs in terms of discharge capacity. Labyrinth side weirs are especially advantageous in places where more discharge is required from small weir openings lengths. The most significant feature of labyrinth side weirs is their effective crest length, which enables them to discharge more flow. In this study, the situation where the discharge capacity is decreased due to the narrowing of the crest length of the labyrinth side weir for any reason was experimentally investigated in detail. It was also considered that the potential narrowing could be in the upstream weir crest length. The overflow from the remaining length of the crest was enabled by the 1/3, 2/3, and 3/3 closure of the upstream crest length of the labyrinth side weir. Therefore, it was attempted to determine the decrease in discharge capacity due to the narrowing in the effective crest length. The values of the discharge coefficient were obtained by using the De Marchi approach. The study was conducted for subcritical flow regimes and steady-state flow conditions. A total of 980 experimental runs were conducted in this study. As the length of upstream effective crest length of the triangular labyrinth side weir at the straight channel decreases, the discharge coefficient also decreases. By narrowing the length of effective upstream crest length in 1/3, 2/3, and 3/3 ratios, the total discharge capacity decreased by approximately 10%, 23%, and 48%, respectively. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted out to investigate the regimes of submerged flows over the sharp-crested weirs in sand bed Channel. These kinds of flows were classified as five states such as (I) impinging jet, (II) bed surface flow, (III) surface jump, (IV) surface wave, and (V) surface jet based on the depicted vector plots of the regimes. By increasing the submergence ratio, the impinging jet was developed as a downward jet which was impinged from the weir crest to the downstream. By continue the increasing, flow regime was developed as a bed-surface flow which is supposed that the impinging jet is turned as flow near the bed position instead of having a direct impact with the bed. Additionally, increasing constancy of the submergence ratio causes that the bed-surface regime turned to the surface jump which is accompanied by a hydraulic jump at the water surface. Subcritical condition at downstream of the weir which is provided by raising the tailwater due to constant flow discharge causes that the surface wave regime has vanished at the water surface of the downstream of the weir and some oscillating waves were transferred to downstream. Finally, by considering the maximum range of submergence ratio, the flow regime was changed to the surface jet which was accompanied by a big clockwise vortex at the lower water elevation. The present study classifies these flow regimes based on the velocity components (u, v, w). This approach was chosen by the authors to show the different classification between visual inspection and investigating the velocity direction by ADV. Then, an empirical equation was proposed to show the boundaries of the presented regimes. Also, a dynamic restriction was proposed based on experimental and literate data as a non-eroded status that is due to a submerge ratio, the scour hole is not provided at downstream of sharp-crested weir. [ABSTRACT FROM AUTHOR]

In this study, dimensionless parameters influencing the coefficient of discharge (COD) are found and four different WRELM models are developed. After that, a dataset is created for verifying the WRELM models in which 70% of the data are employed to train learning machine models and the remaining 30% to test them. For the mentioned algorithm, the optimal number of hidden layer neurons along with the best activation function is chosen. Additionally, the best value for the regularization parameter of the WRELM algorithm is computed. By analyzing the simulation results, the superior WRELM model and the variables impacting the COD are detected. The superior WRELM model approximates COD values with the minimum error and the highest correlation with laboratory values. For the superior model, the values of the R, MAE and VAF statistical indices are computed to be 0.994, 0.0004 and 98.662, respectively. The analysis of the simulation results indicates that the dimensionless parameters α and T/B are the most influencing input parameters. The superior WRELM model results are compared with the algorithm, and it is concluded that the WRELM model is noticeably more efficient. For the superior WRELM model, a partial derivative sensitivity analysis (PDSA) is conducted in which as the input parameter α increases, the PSDA value increases as well. Finally, an equation is suggested for estimating COD values. [ABSTRACT FROM AUTHOR]

Gabion weirs are environment-friendly structures widely used for irrigation and drainage network purposes. These structures' hydraulic performance is fundamentally different from solid weirs' due to their porosity and the existence of a through-flow discharge. This paper investigates the reliability and suitability of a number of Machine learning models for estimation of hydraulic performance of gabion weirs. Generally, three different Boosting ensemble models, including Gradient Boosting, XGBoost, and CatBoost, are compared to the well-known Random Forest and a Stacked Regression model, with respect to their accuracy in prediction of the discharge coefficient and through-flow discharge ratio of gabion weirs in free flow conditions. The Bayesian optimization approach is used to fine-tune model hyper-parameters automatically. Recursive feature elimination analysis is also performed to find optimum combination of features for each model. Results indicate that the CatBoost model has outperformed other models in terms of estimating the through flow discharge ratio (Qin/Qt) with R2 = 0.982, while both XGBoost and CatBoost models have shown close performance in terms of estimating the discharge coefficient (Cd) with R2 of CatBoost equal to 0.994 and R2 of XGBoost equal to 0.992. Weakest results were also produced by Decision tree regressor with R2 = 0.821 and 0.865 for estimation of Cd and Qin/Qt values. [ABSTRACT FROM AUTHOR]

A rectangular slit weir is used to measure small discharges (Q < 5 L/s) and contraction ratios (b/B ≤ 0.25). Various discharge relationships were reported in the literature for calculating the discharge capacity of slit weirs in terms of frontal flow. However, this is not valid for lateral flow. In the current study, the side slit weir flow was investigated experimentally using piezometric heads over the weirs. The discharge coefficient was investigated for side slit weirs with different contraction ratios, which ranged from 0.075 to 0.25. Accordingly, the discharge coefficients were calculated using the Schmidt approach. Moreover, the outflow discharge of sharp-crested side slit weir was analyzed using the incomplete self-similarity theory (ISS) and dimensional analysis. The new discharge model was theoretically created based on the experimental results obtained from laboratory tests. The results of the current study indicated that the contraction ratio, dimensionless head over the weir, and Froude number were dominant parameters over the discharge of sharp-crested side slit weirs. Within this framework, slit weirs can be used laterally as water intake structures for small discharges. Furthermore, a nonlinear equation including all effective parameters is proposed to obtain the discharge capacity of sharp-crested side slit weirs with the highest accuracy. [ABSTRACT FROM AUTHOR]

In the current study, the scour behavior and scour rate downstream of PKWs with rectangular and trapezoidal geometries are investigated and compared for the first time. For this purpose; two experimental models of rectangular and trapezoidal PKWs were constructed and tested at different discharges and three different tail water depths. Three height differences between the sedimentary bed and the weir's base were considered to investigate the effects of drop height on scouring. The scour measurements showed that the scour hole characteristics increased with the increase in the discharge and the decrease in the tailwater depth in both models. The rectangular PKW model created higher scour depths than the trapezoidal model; however, this difference decreased with the increase in discharge and upstream head. Moreover, as the height difference between the sedimentary bed and the weir's base increased, the difference between the maximum scour depth of the two models decreased, and their scour profiles became increasingly similar. Numerical modeling of flow pattern under the same hydraulic conditions was used to interpret the scour profiles of rectangular and trapezoidal models of PKWs. Several equations were formulated for predicting the maximum scour hole depth, its location, and the scour hole length downstream of the models based on the regression method, which can help designers with designing and assessing the safety of weirs. In these equations, the most influential parameter is the head difference between upstream and downstream of the weir. The accuracy of the new formulas for score hole dimensions was compared with previous investigations, especially with equations for falling jet scour. More accuracy was achieved for both types of PKWS scour hole characteristics. [ABSTRACT FROM AUTHOR]

Labyrinth weirs are utilized to transport a greater discharge during floods in contrast to conventional weirs due to their increased weir crest length. Nevertheless, due to the increased geometric complexity of labyrinth weirs, determination of accurate discharge coefficients and accordingly, head-discharge ratings are quite essential issues in practical application. Hence, as a first step the present study proposes the following eight standalone algorithms: decision table (DT), Kstar, least median square (LMS), M5 prime (M5P), M5 rule (M5R), pace regression (PR), random forest (RF) and sequential minimal optimization (SMO). Then, applying the stacking (ST) algorithm, these standalone models were hybridized to predict the discharge coefficient (Cd) for sharp-crested labyrinth weirs. Potential/effective variables were constructed in the form of several independent dimensionless parameters (i.e., θ, h/W, L/B, L/h, Froude number (Fr), B/W and L/W) to predict Cd as an output. The accuracy of the developed models was examined in terms of different statistical visually based and quantitative-based error measurement criteria. The results illustrate that h/W and B/W parameters have the highest and lowest effect on the Cd prediction, respectively. According to NSE, all developed algorithms provided accurate performances, while ST-Kstar had the highest prediction power. [ABSTRACT FROM AUTHOR]

Weirs are important hydraulic structures widely used to control the flow rates in open channels and rivers. The discharge coefficient is a vital parameter in computing flow rate over weirs. In this work, we introduce the Walnut algorithm, a new nature-inspired optimization strategy. Then, it is combined with support vector regression (SVR) to predict the discharge coefficient parameter of triangular labyrinth weirs. The proposed Walnut-SVR method takes a set of observations as inputs specified by five non-dimensional features and attempts to find the discharge coefficient of unseen records. Walnut algorithm is proposed for feature selection, and optimum values of SVR parameters are found. The proposed method is evaluated using the Kumar dataset and compared with several counterpart methods. The results show the superiority of the Walnut-SVR method compared to other counterparts with R 2 = 0.986 , R M S E = 0.004 , S I = 0.006 , σ = 0.858 , and N S E = 0.981 on test dataset. Feature analysis shows that the proposed method obtained the best results when three geometric parameters, the ratio of the weir crest length to the weir height (L/w), the ratio of head over the crest to the weir height (h/w), and the vertex angle (θ ) are used. [ABSTRACT FROM AUTHOR]

Using the outlier robust extreme learning machine (ORELM) method, the discharge coefficient of side weirs placed on rectangular and trapezoidal canals was simulated for the first time in this study. The parameters governing the discharge coefficient of side weirs including Froude number (Fr), the ratio of the weir length to the main channel length (L/b), the ratio of the flow depth at the upstream of the side weir to the main channel width (y1/b) and the ratio of the crest height of the side weir to the flow depth at the upstream of the side weir (W/y1), the ratio of the weir length to the main channel width (L/y1), and the side wall slope parameter (m) were initially detected. Using the parameters governing, eight different input combinations were defined. By randomly selection approach, 65% of the data were considered to train the ORELM models and the rest of samples were applied to test them. The correlation coefficient, Nash–Sutcliffe efficiency coefficient, and Scatter Index for this model were calculated to be 0.937, 0.869 and 0.092, respectively. The results of sensitivity analysis indicated the ORELM model was more sensitive to the W/y1 and L/b than Fr and y1/b. The results of the ORELM model were also compared with the support vector machine optimized with genetic algorithm (SVM-GA) and extreme learning machine (ELM)) and four multiple linear regression models, with a better performance of the ORELM model. The ORELM models demonstrated a higher precision and correlation with experimental values. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Environmental influences on the phenology of immigrating juvenile eels over weirs at the tidal limit of regulated rivers" published in the journal Hydrobiologia. The correction addresses an incomplete in-text citation and a missing reference in the original publication. The correct reference is provided in this correction notice. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. The authors of the article are Rose M. Boardman, Adrian C. Pinder, Adam T. Piper, Catherine Gutmann Roberts, Rosalind M. Wright, and J. Robert Britton. [Extracted from the article]

Hydraulic engineers are always seeking solutions to increase the flow rate capacity of weirs in order to overpass and regulate large flow rates with low upstream afflux, preventing the submergence of valuable lands and private properties. The current study intends to improve the flow rate capacity of sharp-crested triangle weirs using upstream slopes or guiding vanes. The laboratory work involved building and testing twenty-one weir models. Six weir models were left unmodified, while six were modified with upstream slopes changing the angle of vertex θ = 45°, 60°, and 75°, and the height of the weir Pw = 20 and 25 cm. Nine weir models were modified with guiding vanes, with vane heights of 20, 15, and 10 cm. Laboratory results showed that the flow rate coefficient Cdt value decreases as the ratio of upstream head Hcr to height of weir Pw increases, and weirs with a small angle of vertex and a low height of weir allow high flow rates to overpass. In all situations investigated, modified weir models produced greater values of Cdt than unmodified ones. Two empirical power equations were given for estimating Cdt in terms of Hcr/Pw and angle of vertex θ. One for weir models modified with upstream slopes and the other for weir models modified with guiding vanes. The flow rate magnification decreased significantly as Hcr/Pw increased, and models with a small angle of vertex and low weir height provided high flow rate magnification values. A weir model with θ = 45°, Pw = 20 cm, and Pv = 10 cm, modified with guiding vanes, showed the biggest percentage increase in flow rate, ranging from 110 to 220%. [ABSTRACT FROM AUTHOR]

Controlling water levels in main channels by constructing side weirs can be influenced by geometric modification. Therefore, proposed geometric changes to the crest of the traditional sharp-crested weir are tested to study the hydrodynamic performance of these weirs. Triangular labyrinth side weir with and without a ramp, curved wing crest and 3 different diameters of circular crest were investigated experimentally and numerically. All the tested shapes have three inclusion angles (θ = 30, 45, and 60°), and three heights (0.1, 0.15, 0.2 m). The fluid volume (VOF) and the turbulence renormalization (RNG k-ϵ) method were selected for simulation and verifying the free surface flow along the center line and beside the weir in the main channel and measuring the velocity at certain cross sectionssections. The smaller inclusion angle between the walls (θ = 30°) performs better in discharging side flow and has a higher discharge coefficient than others. Upon comparison with a traditional labyrinth side weir, a modified side weir with a curved wing and a smaller circular crest diameter increases discharge coefficient (Cd) by about 20.7% and 6.43%, respectively, while its value reduced with the increase of crest diameter and its performance decreased about 17% by increasing the weir crest diameter from 2.5 to 5 cm. However, no improvements have been visualized for adding an upstream ramp. Moreover, in a smaller inclusion angle, the diverting streamline width of flow was obtained to be 0.81 and 0.65 times the main channel width for the modified weir with a curved wing and triangular labyrinth side weir, respectively. In addition, the highest separation zone width downstream of the parent channel for inclusion angle (30°) was observed to be about 2.5 and 1.8 times its width of angle (60°) for curved wing and traditional labyrinth weir, respectively. The discharge coefficient of the curved wing was 3 times the normal rectangular side weir coefficient. [ABSTRACT FROM AUTHOR]

The hydraulic relationships of flow through the weir of different common shapes were investigated in this study. The hydraulic performances of weirs were carried out experimentally, by using eight different types of weir models, and the effect of various shapes of the weir to specify different hydraulic parameters such as coefficient of discharge (Cd), weir geometric shape and size constants (K) and weir shape number (n), energy dissipation ratio (E %) for selecting best flow measuring weir type. The experimental work was carried out on a tilted rectangular flume with 7.5 m long, 0.30 m wide and 0.45 m deep with a discharge range 0.50–20.95 L/s. The experimental results of this study showed that the dissipation energy corresponding to triangular notches is larger than the resulted from rectangular notches. For compound notches of rectangle and triangle, turbulence inflow increases as the angle of lower notch decreases. Thus, this type with an angle of (θ = 120ο) is the most efficient between the studied models, which gives the average Cd of 0.82, the value of K is equal to 0.75 and n values of 1.96, and the dissipation of flow energy ratio of (35.86%) for strong hydraulic jump. Finally, depending on a statistical basis, this study derived empirical relationships to estimate the coefficient of discharge with acceptable values of the coefficient of determination. [ABSTRACT FROM AUTHOR]

Weirs are structures that are important for measuring flow and controlling water levels. Research has shown that the discharge coefficient is not constant and depends on the crest length, the height of the weir, the upstream head, and the upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficient (Cd) is investigated by numerical simulation. The current study present numerical simulation using the ANSYS FLUENT software. The total number of simulations is 432 which includes: 4 upstream slopes, 4 downstream slopes, 3 weir heights, 3 upstream heads (h1) and 3 weir crest lengths. It was found that the downstream face slope has little effect on Cd. For 0.1 < H1/w < 0.4 by decreasing the upstream slope, Cd increases, where H1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the Cd increases. For 0.16 < H1/p < 2, as the length of the crest decreases, the Cd increases. By comparing the numerical simulation results to physical measurements, multi-variable regression equations for estimating Cd are presented. In addition to Cd, extraction of other more detailed information such as water level profiles and velocity profiles at different locations is provided. [ABSTRACT FROM AUTHOR]

Dams are multipurpose structures that provide water for drinking purposes, hydroelectric power generation, navigation, industrial uses, and irrigation, in addition to flood control. The loss of storage due to siltation or submergence can be remedied by constructing an ungated spillway or weir over the dam structure. Many researchers have studied different shapes of the weir to reduce the submergence problem; some used the modified shape of the weir named Labyrinth weir in their studies, which gives the concept of a new shape of the nonlinear Piano Key Weir (PKWs). The PKW is a cost-effective solution for rehabilitation and new dam projects with a high level of constraints, for instance, limited space, small reservoir level, high specific flood discharge, etc. This paper reviews the previous studies on the historical development of the PKW, the geometry and structural integrity, the methodologies developed by researchers, and the stability of flow hydrodynamics at the PKW. The purpose of this study is to summarize the available information to date about PKW hydraulics and compare it to other alternative rectilinear or nonlinear weirs from the literature in terms of discharge capabilities, sediment transportation efficiency, aeration performance, and economic aspects. The comparison shows that the PKW is an excellent alternative for dam risk mitigation due to its high spillway capabilities, aeration performance, and economic point of view with other alternatives. Furthermore, in addition to field applicability, this study identifies future research possibilities that merit further investigation. [ABSTRACT FROM AUTHOR]

Free overfall structures might affect the structural safety of weirs. Thus, it is essential to minimize local scour in the downstream pool to ensure structural safety. In the present study, triangular, trapezoidal, and labyrinth weirs were analyzed numerically for free overfall with the Computational Fluid Dynamics method to estimate local scour depths. The finite-volume approach was employed to solve the RANS equations by using Flow-3D software. For turbulence closure, the standard k–ɛ turbulence model was preferred, which is widely used in the literature with certain confidence especially in open channel problems. The numerical results were tested with some experimental observations, and a reasonable agreement was achieved between numerical and physical model results. The findings also indicated that the local scour at the labyrinth weir downstream is lower than that of the classical weirs, while the horizontal distance of maximum scour depth in the labyrinth weir is lower than that in the classical ones. [ABSTRACT FROM AUTHOR]

Many researchers have suggested that birds may use natural infrasound sources for navigation and hazard avoidance. However, there is a need to define the sound levels and frequencies to characterize potential infrasound sources. This paper summarizes new measurements from Niagara Falls which define a stable, powerful infrasound source that could be detected by birds on a regional scale of over 400 km. Measurements made in the vicinity of Niagara Falls show that exceptional infrasonic pressure levels can occur in the regions of large waterfalls (> 100 Pa at a range of about 500 m). This paper reviews investigator assessments of avian use of infrasound. A review of the results of Cornell researchers on pigeon hearing provides a basis for estimating avian detection ranges of waterfalls. It is possible that migrating birds use sounds from waterfalls as beacons- a component of their "navigation toolbox" as well as infrasound for hazard avoidance. [ABSTRACT FROM AUTHOR]

The Dujiangyan Project, located at the junction of the upstream of the Minjiang River and Chengdu Plain, Sichuan Province, China, is an irrigation system project as important as the Great Wall in the history of China. Without dam structures, this project has been continuously playing its crucial role in diverting water for irrigation, separating sediments, and controlling flood for 2275 years. In this study, the predicaments of the Dujiangyan Project under the background of rapid urbanization and social economic development were summarized by conducting the field research and using the Indicators of Hydrological alteration (IHA) method: excessive diversion of water, disruption of hydrological pulses, erosion and deposition imbalance and conflicts between power generation and water supply. These contradictions have led to the weakening of the function of automatic water diversion and sand removal in the Dujiangyan Project. Considering the influence of climate change and strong human activities, we pointed out the challenges faced by the millennium ancient weir in balancing human and environmental water usage and project operation and management based on the simulation results of the hydrological model. The corresponding suggestions about strengthening agricultural water saving, generating artificial flood peak were provided to protect and continue to maintain the function of the Dujiangyan Project. [ABSTRACT FROM AUTHOR]

The piano key weir (PK-Weir) is a hydraulic structure used in the irrigation system by its construction on artificial or natural channels such as rivers or irrigation canals, it may be in the submerged state due to an increase in flow or an obstacle downstream of the PK-Weir. Therefore, this type of weir has been the subject of several experimental studies in order to understand the phenomenon of streaming flow on the weir, which led to the development of empirical relationships describing the effects of streaming flow on hydraulic performance. Experimental studies are essential for the design of weirs, but they require a lot of time to collect a real database. The main objective of this paper is to predict the relative head of PK-Weir for submerged flow using artificial neural networks. To do this, we have used the results of our experimental study to develop a neural model. The results obtained were very satisfactory with very acceptable errors (RMSE = 0.0133 and MAE = 0.0066). In addition, a comparative study was made between empirical relationships and the developed model. The results of this comparative study showed a good agreement. [ABSTRACT FROM AUTHOR]

A moving weir to reduce the time for grade transition is proposed. To investigate benefits of the proposed moving weir, tundish flow subject to various conditions of a moving weir was numerically investigated. First, an optimal travelling path of a horizontally moving weir was determined in a water model. Investigation of various cases shows that the shortest transition time is obtained when new molten steel is injected after the weir returns to its original position after a round-trip. Using this travelling path, the speed of the moving weir was investigated in a real-scale model to determine an optimal speed that stabilizes the surface height while the transition time is minimized. As a result, intermixing of steel with dissimilar grades has been reduced by 14.5 % by using the optimal conditions of the moving weir. Lastly, the performance of vertically moving weirs was assessed by comparing with that of the horizontal counterpart. [ABSTRACT FROM AUTHOR]

A piano key weir (PK weir) is a non-linear, labyrinth-type weir that benefits of a high discharge capacity, and is well suited for low head dams. Determination of the discharge coefficient (Cd) is considered as one of the most important issues, which plays a substantial role in reducing structural and financial damages caused by floods. The main aim of the present study is to experimentally investigate the variations of PK weirs discharge coefficient (Cd) through altering the geometric parameters. The obtained results revealed that in modified PK weirs (by an 11.5% increase in weir height, changing the crest shape, and fillet installation), the Cd values were about 5–15% more than those of the standard PK weirs. The Cd values of the non-contracted weirs were increased by increasing the inlet/outlet width ratio by 1.4, while this relation was adverse for contracted weirs. In the modified PK weirs, the submergence would occur faster than the standard weirs, while the complete submergence would occur later. Moreover, robust kernel-based approaches (kernel extreme learning machine and support vector machine) were successfully employed to the extensive experimental dataset by taking into consideration the Cd as a function of dimensionless geometric variables of PK weirs. The obtained results showed that the ratio of the upstream hydraulic head (H0) to total weir height (P) plays a significant role in the modeling process. [ABSTRACT FROM AUTHOR]

A theoretical framework, based on the phenomenological theory of turbulence applied to scour-related processes due to plunging jets on cohesionless beds, is considered in this paper. More specifically, its predictive capability is assessed herein for large-scale domains, after it was developed for small scales elsewhere. The analysis focuses on both the time-evolution process and the equilibrium configuration for a wide range of hydraulic structures. After revisiting the theory for the temporal evolution of the scour processes, the scour for large-scale tests is investigated using unpublished experiments performed at Colorado State University by the last author. These tests confirm the existence of two stages in the scour hole development, namely the developing and developed phases. Thus, the scour dynamics at large scales is shown to be consistent with that at smaller scales. Then, the theory recently introduced by the first three authors is used to predict the time evolution of scour, corroborating that the very same equations, together with the same coefficients, provide successful predictions, regardless of scale and granulometric distribution. Finally, the theory is again verified against laboratory data on PK weirs obtained at the University of Pisa. Overall, the work described in the paper offers a tool with general validity. [ABSTRACT FROM AUTHOR]

Lake Tana is one of East Africa's largest freshwater bodies, yet many of its fishes are migratory and utilize in-flowing tributaries as critical spawning habitat. However, factors such as expanding water resources developments and sand mining along these rivers and streams may disrupt this ecosystem function. We monitored juvenile and adult fish abundance and water quality across five lake tributaries from August 2014 to April 2015 to examine how irrigation schemes and water quality affect assemblage and population structure. Adult assemblages were dominated by Labeobarbus cyprinids and varied between tributaries, albeit without separation by irrigation development or sand mining. Overall, adult abundances of the dominant migratory Labeobarbus species were four-fold higher below the Shini River irrigation weir than upstream. Contrastingly, juvenile abundances were often significantly higher above these structures. Juvenile abundances decreased on average by 46% along the first 1000 m of two irrigation canals, suggesting poor habitat suitability or high mortalities from water withdrawals. Water quality varied more between rivers than sampling times, but without any separation of tributaries by irrigation or sand mining. Conductivity and turbidity-related parameters had the highest correlation with adult assemblage structure and individual species abundances. These findings indicate that Lake Tana tributaries must be managed on a case by case basis, with more focus given to mechanisms allowing fish to bypass irrigation developments and the direct assessment of fish populations between sand mining and other sites. [ABSTRACT FROM AUTHOR]

This article describes the Zhongbao landslide that occurred in Liujing Village, Tudi Township, Wulong District, Chongqing, China, on July 25, 2020. Due to the catastrophic soil and rock landslide, the houses and village roads of three villagers in the landslide area are damaged and formed weirs. The landslide eventually formed a barrier lake. In order to reveal the failure mechanism of the landslide, aerial data was collected on the landslide site using UAV and high-resolution remote sensing images. The characteristics of the landslide are analyzed based on the geological conditions and the properties of the rock formations in the landslide area. The continuous intense rainfall increased the water content of the landslide in this area, increasing its weight. Increasing the water content softens the sliding surface and lowers strength. Therefore, the rock and soil mass on the upper slope slides along the sliding surface under the action of gravity, causing a shale rock mass of about 1.3 million cubic meters to slide quickly from the upper part of the slope into the V-shaped valley and form a barrier dam and barrier lake. By evaluating the rising height of the initial dammed lake, the affected area can be predicted. Through the analysis of the study area, it can provide references for the failure mechanism of landslides, the characteristics of landslide bounce, and the risk assessment of cofferdams in Southwest China. [ABSTRACT FROM AUTHOR]

Piano key weirs (PKWs) are an improved form of labyrinth weirs, which are becoming popular as a more hydraulically efficient and cost-effective type of weir over its counterparts for both spillway and river flow conditions. More than thirty PKWs are already in construction worldwide, with constructions in India at Swara Kuddu. More than twenty parameters influence the flow over a PKW, and as such, the flow hydraulics near PKW is complex. It is imperative to study the performance of different shapes of PKW to know which shape offers more hydraulically and cost-effective advantages over other shapes. The present study combines the experimental and numerical study of discharge capacity and sediment carrying capacity of the different plan geometries of PKW. The experimental study of the discharging capacity of PKW has been carried out at eighteen discharge points for three plan geometries of PKW. A numerical study using ANSYS FLUENT has also been carried out at five discharges and compared with the experimental results. Vertical velocity near a weir is an essential factor facilitating the uplift of sediment. Sediment profile in the channel has been studied at three discharges experimentally for two types of PKWs: RPKW and TPKW6, all for free-flow conditions. The numerical study has also been carried out at these experimental discharges for studying the vertical component of velocity (v) upstream of PKW. An attempt has been made to isolate critical areas where the sediments are being lifted by the turbulence mechanism, thus helping them pass over the weir. The study shows PKW with a rectangular plan (RPKW) to be more hydraulically efficient than TPKWs with six-degree and thirteen-degree lateral crest variations (TPKW6 & TPKW13). The study also shows RPKW to be more self-cleaning in nature than its trapezoidal counterpart (TPKW6). Numerical study shows a close resemblance to the experimental results with errors well within permissible limits implying its greater use in ascertaining complex flows around hydraulic structures. [ABSTRACT FROM AUTHOR]

Piano Key Weirs (PKW) is a free-flowing weir, and an improvement over the labyrinth weir family. PKW has higher discharge for the same head as compared to other types of weirs. They tend to reduce the upstream submergence in reservoirs or other flow systems and can be effectively used for flood risk mitigation. CFD studies have been carried out earlier but mostly for H/P (Total head to height ratio) greater than 0.1. The present paper investigates the use and validation of Computational Fluid Dynamics (CFD) for modeling Open Channel flows over common hydraulic structures such as PKW for small discharges with the entire range of head to height ratio h/P from 0.035 to 0.1, where h is not the total head upstream of PKW but the head measured at the crest of PKW. The numerical results have been validated with experimental results. Since the discharge is minimal surface tension force has been incorporated in the numerical model. The numerical model is a half PKW unit model with the same geometrical parameters as the experimental setup from Literature. The results show that CFD simulations can reproduce flow depths near PKW with reasonably good accuracy. The present paper compares the head obtained from CFD with that of empirical formula in the Literature but with head measured at the crest of PKW. Investigation of water surface profile and velocity profile near the upstream of PKW has also been carried out. [ABSTRACT FROM AUTHOR]

Tidal marshes are increasingly vulnerable to degradation or loss from eutrophication, land-use changes, and accelerating sea-level rise, making restoration necessary to recover ecosystem services. To evaluate effects of restoration planting density and sea-level rise on ecosystem function (i.e., nitrogen removal), we restored three marshes, which differed in elevation, at Weeks Bay National Estuarine Research Reserve, Alabama, USA and planted them with Juncus roemerianus sods at 0, 25, 50, 75, or 100% initial cover. We simulated future sea level using passive weirs that increased flooding during low tide. Because additional species emerged shortly after transplantation, we also tested for treatment effects on community structure. In all marshes, species richness increased following restoration, regardless of treatments, while relative abundances of new species tended to increase with increasing initial cover. Plant percent cover increased with increasing initial cover in all marshes, with similar vegetated cover at 50, 75, and 100% after 3 years in the highest elevation marsh. Porewater dissolved inorganic nitrogen concentrations ([DIN]) decreased with increasing initial cover in all marshes, and were significantly lower in 50, 75, and 100% treatments than 0 or 25% after 1 year. Furthermore, [DIN] was similarly low among 50, 75, and 100% treatments when elevation capital was highest. These results suggest that intermediate initial cover (50%) can recover plant cover and promote nitrogen removal when elevation capital is adequate at relatively lower labor and material costs than planting at higher cover, thereby maximizing restoration outcomes in the face of low to moderate sea-level rise. [ABSTRACT FROM AUTHOR]

Many hydraulic structures are constructed in an open channel according to the purposes and the nature of the region. Weir is one of these structures which is used for discharge measurements as well as rising water depth in irrigation channels. According to the crest, there are two different shapes: sharp and broad crested weir. A stepped weir is constructed to reduce scour that happened downstream. There are different studies dealt with discharge coefficient, energy dissipation, and other hydraulic characteristics for flow over the weir. In this study, the coefficient of discharge for the Al-Shalalat stepped weir on the Al-Khusr River has been evaluated. The discharge coefficient equation is predicted, and the result values are compared with previous studies. The percentage error for the predicted discharge equation presented in this study compared with previous studies does not exceed 10%. [ABSTRACT FROM AUTHOR]

The circular crested weir (CCW) has been introduced as weirs having a high discharge coefficient (Cd). The ratio of flow head to the radius of the crest (H/R) is the most important parameter affecting the Cd, that the Cd ≈ a H / R b can mathematical model their relation. In this study, the parameters of the Cd formula (i.e., a and b) were uncertainty analyzed using Monte Carlo (MC) and Bootstrap methods (BM). To perform these methods, some of the built-in functions of Excel software were utilized. The results declared that the average values of a and b were 1.187 and 0.140. The outcome of the MC method showed that the range of a and b at 95% confidence interval changed between 1.179 to 1.194 and 0.134 to 0.146, respectively, while at the same confidence interval the BM ranged from 1.187 to 1.200 and 0.133 to 0.147. [ABSTRACT FROM AUTHOR]

Barriers preventing species from dispersing to a location can have a major influence on how communities assemble. Dispersal success may also depend on whether dispersers have to colonise an established community or a largely depauperate location. In freshwater systems, dams and weirs have fragmented rivers, potentially limiting dispersal of biota along rivers. Decommissioning aqueducts on two weirs, each within a tributary of different regulated rivers, delivered flow to previously dry riverbeds and additional flows to the main stem, regulated rivers further downstream. This provided an opportunity to test how removal of dispersal constraints affected community assembly in new habitats and whether changed dispersal can alter existing communities. The results were very similar for the two systems. Even with dispersal constrained via reduced drift rates, the new communities in the newly formed habitat in tributaries rapidly resembled unimpacted reference communities that were the source of colonists. For established communities (regulated rivers), greater flow increased the densities of filter feeders but this was due to greater areas of fast-flowing habitat (a change in environmental constraints) rather than higher dispersal rates. Our study illustrates that communities can quickly re-assemble when natural channels that have been dry for decades are re-wetted by flows that deliver dispersers from intact locations upstream. Nevertheless, boosting flows and concomitant densities of dispersers had no strong effects on existing communities. Instead, increased discharges effected a reduction in environmental constraints, which altered trophic structure. Thus, increases in discharge and dispersal produced different outcomes in new versus established communities. [ABSTRACT FROM AUTHOR]

Laboratory tests of water flowing over a modified ogee weir are carried out in a wave–current flume for two different scales. A model of a weir representing a part of a spillway section of the existing Włocławek dam (Vistula River, Poland) is mounted in a wave–current flume. The Froude similarity law is used to simulate the flow over a real damming structure at 1:25 and 1:50 scales. Particle image velocimetry methods are employed to measure a flow velocity field over the crest of the weir model. The system is capable of providing high fidelity velocity fields at sampling rates of 10 Hz and 50 Hz. Detailed information on flow characteristics is extracted from the instantaneous velocity field measurements to provide a comprehensive description of the kinematics of a weir flow at discharges corresponding to hydrological events with return periods of 100 and 1000 years, revealing some interesting spatial features. The geometry of the weir results in the development of a characteristic circulation cell, which is relatively wide for the lower discharge. When the flow intensity increases, a triangular circulation develops behind the weir crest instead. Moreover, sudden changes in the flow regime lead to the rapid formation of vortex structures, which propagate downstream at speeds ranging from 0.3 to 1 m s−1. The origin of eddy formation is identified at the upstream and downstream ends of the weir crest for respective average velocities at the crest of approx. 0.6 m s−1 and 1.2 m s−1. [ABSTRACT FROM AUTHOR]

The construction of artificial weirs as part of the Four Major Rivers Restoration Project is expected to result in the Nakdong River Basin having the characteristics of closed water bodies and properties of water quality that convert suspended components into soluble ones due to a long retention time, thereby leading to the continuous deterioration of water quality. In this regard, this study investigated the changes of water quality on four weirs in the mid-lower Nakdong River Basin. In addition, it examined the organic matters and nutrient salts affecting the water quality, established mass balance with respect to the nutrient salts, and analyzed the load accumulations of each weir to present the directions for water quality management. With regard to the water quality, the items of BOD and COD, T-N and NH4-N, and T-P and PO4-P showed similar tendencies, and most of the items exhibited high concentrations from July to September. Furthermore, it was confirmed that the concentrations of the water quality items were high in Dalseong Weir and Hapcheon-Changnyeong Weir. In July, most of the weirs showed the greatest difference of DO in the surface layer and deepwater layer, while the DO concentration of the deepwater layer dropped below 4.0 mg/L in all four weirs. The sediment survey showed that the SS, T-N, and T-P have a larger amount of sediment in the aphotic zone than in the photic zone, and the amount of sediment per unit area was greatest in Dalseong Weir. According to the sediment release survey results, the release concentration was high in July, which was due to the effects of high water temperature and low DO concentration. T-N was eluted mostly from Dalseong Weir and Gangjeong-Goryeong Weir, and T-P was eluted mostly from Dalseong Weir and Hapcheon-Changnyeong Weir. Among the mass balance, nitrogen balance showed the highest amount of accumulation in Gangjeong-Goryeong Weir (6109 kg/d), and phosphorus balance showed the highest amount of accumulation in Changnyeong-Haman Weir (447 kg/d). These results are expected to be utilized as important materials for setting the management directions for each weir. [ABSTRACT FROM AUTHOR]