Bathymetric contour mapping in inland waterway systems presents significant challenges in balancing data simplification, feature preservation, and visual quality. Traditional single-stage methods address individual aspects but fail to meet comprehensive hydrographic surveying requirements. This study proposes a dual-stage BCPO+FRO algorithm framework that combines Boundary Control Point Optimization and Fluctuation Reduction Optimization. The BCPO stage performs global shape optimization through control point calculation, polygon construction, and iterative smoothing. This process reduces line complexity while preserving bathymetric accuracy. The FRO stage identifies and suppresses local fluctuation features using terrain-weighted indicators and dynamic parameter adjustment mechanisms. This approach improves visual quality without compromising critical underwater terrain characteristics. Experimental validation was conducted on diverse terrain types in the Yangtze River inland waterway navigation channel. Results demonstrate superior performance with substantial turning point reductions, minimal horizontal deviations, and high terrain feature preservation rates. This research provides practical applications for inland waterway management, navigation safety, and hydraulic engineering, and provides technical reference for research on China's smart water conservancy construction.
This study investigates the optimization of key CCHE2D model parameters through sensitivity analysis of computational mesh resolution, turbulence closures, and roughness coefficients for simulating turbulent flow in a sharply curved meandering reach downstream of the Minab Dam, Iran. A two-dimensional hydrodynamic model was developed using surveyed topographic data and multiple mesh configurations. Parameter sensitivity was evaluated using the GLUE uncertainty framework together with RMSE and MAPE metrics, and model results were validated against field measurements of flow velocity and depth. Results show that a mesh resolution of 55 & times; 500 cells and Manning's n values of 0.033-0.052, estimated using the Cowan method, provided the best agreement with observations. Flow depth was relatively insensitive to mesh refinement, whereas velocity predictions were highly sensitive, particularly near concave banks of high-curvature bends. The k-epsilon turbulence model outperformed the parabolic eddy-viscosity formulation by more accurately representing curvature-induced turbulence and secondary currents. The findings demonstrate the effectiveness of the GLUE framework for uncertainty quantification and emphasize the importance of appropriate hydraulic parameter selection. The proposed framework offers a practical approach for improving hydrodynamic simulations in complex meandering rivers.
Accurate flood quantile estimation at ungauged sites is essential in water resource planning and flood risk management. Regional Flood Frequency Analysis (RFFA) based on the L-moment framework offers a robust and computationally efficient approach for estimating flood quantiles, particularly in data-scarce or ungauged catchments. Recent studies highlight the advantages of LH moments (i.e. higher-order probability-weighted moments), which provide enhanced sensitivity to distributional tails and improve the representation of extreme flood events. This paper assesses the influence of Koppen-Geiger climatic zones (i.e. arid, temperate, and tropical) on design flood estimation for ungauged rivers of peninsular India. The Conventional Index Flood method is compared with a recently proposed RFFA approach tailored for general peak discharge distribution datasets within the LH-moment framework, treating climatic zones as homogeneous regions. Results indicate higher heterogeneity in the arid zone, while the tropical zone is relatively homogeneous. Regional goodness-of-fit tests identify the GEV and GLO distributions as suitable regional distributions for the arid region, whereas the GLO distribution is more appropriate for the tropical region. The findings support improved flood risk assessment and infrastructure design and contribute to the development of more reliable, climate-sensitive flood management strategies.
The present study explores the wave generation, progression, and decay induced by the collapse of partially/completely submerged granular columns in a confined domain. The wave reflection at the opposite side of the landslide becomes important, especially in reservoirs of narrow width, leading to the consideration of a confined experimental setup. The time history of the waves recorded at fixed spatial points within the domain is characterized by the peak amplitude, time of arrival and decay. The non-dimensional peak amplitude for the same granular heights varies inversely with the fluid depth. The maximum wave amplitude is recorded at the downstream boundary, and the decay of the waves follows an exponential law that becomes asymptotic to the mean water level. The decay coefficient of the exponential law for partially submerged cases depicts that the water surface fluctuations die down faster in the middle than in the downstream extremity and near the collapse zone. For fully submerged cases, the faster dissipation is observed near the toe of the collapse zone. The post-collapse interaction of the waves with a sloping porous surface leads to a slowed dissipation of the waves in the domain and sometimes induces secondary granular motion as well.
Flooding poses serious risks to agriculture, infrastructure, and human life, making accurate flood susceptibility assessment essential for effective management. This study focuses on the Cachar district of Assam in the Barak River basin, where flood events have intensified in recent years. To enhance prediction accuracy, Classification and Regression Tree (CART) models were integrated with nature-inspired optimization algorithms: Shark Smell Optimization (SSO-CART), Spotted Hyena Optimization (SHO-CART), and Wild Horse Optimization (WHO-CART). Sixteen flood-conditioning factors were initially analyzed, with twelve key variables selected for model development using feature selection techniques. Model performance was evaluated using the Area Under the Receiver Operating Characteristics (AUROC) curve. All models demonstrated strong predictive ability, with AUROC values above 0.70. Among them, WHO-CART achieved the highest accuracy, with an AUROC of 0.94. The Wilcoxon Signed-Rank test confirmed statistically significant differences between the models. Flood Susceptibility Maps indicated lower risk in the northern region and higher vulnerability in the western and central areas of Cachar. Approximately 45% of the basin (about 1,700 km & sup2;) falls within moderate to high flood-prone zones. Overall, this study presents an interpretable hybrid modeling framework that improves CART performance and supports informed flood risk management and planning. [GRAPHICS]
Surface water contamination by heavy metals poses rising environmental and public health risks in rapidly urbanizing, agro-intensive regions. This study evaluates the contamination intensity and ecological risk of copper (Cu), zinc (Zn), lead (Pb), iron (Fe), and mercury (Hg), in 10 inland waterbodies in and around Pollachi, Coimbatore region, Tamil Nadu. A holistic assessment couples conventional indices Contamination Factor, Enrichment Factor, Pollution Load Index, and Potential Ecological Risk Index with multivariate tools (PCA, CA and MTA) to delineate hotspots and apportion sources. Pre-monsoon samples analysed by atomic absorption spectrophotometry revealed severe contamination Fe = 56.04-230.49 mg L-1 Cu = 8.32-29.88 mg L-1, Zn <= 21.83 mg L-1, Hg = 0-0.69 mg L-1, and Pb = 0.10-1.79 mg L-1. Pollachi Central and Zamin Uthukuli were critical hotspots (PLI up to 11; PERI 2400-2800). PCA showed 68.6% of variances, loadings indicated anthropogenic inputs, clustering grouped industrial proximal and mixed land-use sites, MTA identified outliers at Kaliyapuram and Angalakuruchi. CF/EF patterns showed high enrichment of Pb and Hg at sites caused by industrial effluents, agricultural runoff, and urban waste. The integrated index multivariate framework strengthens diagnostic confidence and provides practical evidence for continuous monitoring, source control and remediation to protect our ecosystem.
Storage reservoirs are constructed and operated to overcome mismatch between supply of water and demands. Reservoir operation causes changes in downstream rivers. While operating a reservoir, environmental flows (Eflows) are released in the river to meet the requirements of aquatic ecosystems and mitigate impacts due to diminished flows. Numerous studies have estimated Eflows in different river basins, but trade-offs between sizing and operation of multipurpose reservoirs have not been adequately studied for seasonal rivers. This study has examined how the performance of reservoirs in seasonal basins is impacted as storage size and Eflows change. It is found that if the reservoir size is increased beyond a storage ratio (defined later) of about 0.7, additional irrigation benefits show small increase, but spills do not reduce significantly. The zone between storage ratios 0.2-0.8 is crucial in reservoir design. A framework has been presented to assess the trade-offs in reservoir sizing and operation to meet Eflows and other needs and arrive at acceptable solutions. Results show that the trade-offs depend on the relative magnitude of Eflows and other demands and on statistical properties of inflows and demands.
The research analyzes how Venturi flumes improve oxygen absorption through throat-induced turbulence that dramatically enhances the volumetric oxygen transfer coefficient (K(L)a). Machine Learning models were developed to predict K(L)a using discharge per meter width (q), throat width (W), throat length (F), converging (C), and diverging (D) side wall length, upstream entrance width (E), flume height (H), and water depth (H-b). Tested models included Linear Regression (LINR), Ridge Regression (LINRE), Bayesian Ridge Regression (BAY), Polynomial Regression (POLYR), and Decision Tree Regressor (DTR). Ensemble approaches comprised Bagging with Decision Tree (BAGD), along with Random Forest (RF), Extra Trees (EXTR), AdaBoost (ADaB), and Gradient Boosting (GRaB). Performance was evaluated using 5-fold cross-validation with statistical metrics and graphical evaluators. POLYR achieved the highest accuracy, followed by RF, on both datasets. Uncertainty analysis validated their robustness. Sensitivity analysis identified q and H-b as key dimensional factors, while Reynolds number (R-e) and H-b/H ratio dominated non-dimensional datasets, consistent with Shapley analysis. An independent validation study under the maximum observed K(L)a demonstrated strong agreement between predicted and experimental values, confirming the robustness and generalization capability of the developed POLYR model.
Lower flow regime bedforms have a significant influence on the hydraulic characteristics of flow, and their effects can be observed as discontinuities in stage-discharge rating curves. Various methods have previously been proposed to accurately predict bedform resistance; these methods are generally presented in the form of experimental diagrams or empirical relationships. Owing to the large number of influencing parameters, the application of such methods is often associated with considerable complexity. In the present study, using the results of 292 experiments collected from four different sources, a simple and practical method is proposed to predict the effect of lower flow regime bedforms on the increase in flow depth. The obtained results show reasonable accuracy, such that in 90% of the estimations the computational error was less than 25%. According to the newly proposed approach, the formation of ripple or dune bedforms in a rectangular channel leads to an increase in flow depth of approximately 25%. Based on this ratio, relationships were also developed to predict the Manning roughness coefficient. The variation of the bedform-related Manning roughness coefficient ranges from 0.25 of the grain Manning roughness coefficient for deep flow in narrow channels to 0.45 for shallow flow in wide channels.
The present study examines the impact of flexible floodplain vegetation on flow behavior in compound channels with converging geometries. Experiments were conducted in a laboratory flume to quantify differences in water surface profiles and depth-averaged velocities under vegetated and non-vegetated conditions at various flow depths. The results show that vegetation increases flow resistance, resulting in higher water levels at the same flow rate than in the case without vegetation. Vegetation significantly reduced velocity in the floodplain, creating a more even distribution across the channel's cross-section. These changes demonstrate how vegetation dampens flow momentum and affects the exchange between the main channel and the floodplain. The results offer valuable insights for river engineers and planners, enhancing their understanding of flow movement, improving stage-discharge prediction, and informing floodplain management and restoration efforts.
Water-retaining structures, such as earth dams, require a careful assessment of seepage behavior to ensure structural stability and prevent failure. This study presents a comprehensive numerical investigation of sheet pile cutoff walls as seepage control measures in earth dam foundations using finite element analysis with SEEP/W software. An earth dam model with varying sheet pile configurations was analyzed to evaluate the effects of sheet pile position and length on seepage parameters, including flow rate, water pressure head, and hydraulic gradient. Four different sheet pile lengths (6, 8, 10, and 12 m) were positioned at various distances from the dam heel (25.5, 51, 77, and 102.5 m) to assess optimal placement strategies. Results demonstrate that sheet piles significantly reduce seepage in all scenarios of the research. Sheet piles positioned closer to the downstream toe achieved superior seepage control performance compared to those at upstream positions. Increasing sheet pile length results in a substantial rise in water pressure head loss and hydraulic gradient by about 13 and 15%, respectively, whereas seepage discharge diminishes (about 9%). Moreover, it was deduced that the sheet pile length has a higher impact on changes in the studied parameters and earth dam safety compared to sheet pile distance.
Under large unit discharges, the upstream section of stepped spillways is highly susceptible to cavitation damage due to the lack of aeration protection. This compromises its energy dissipation efficiency and can even lead to safety incidents. To address this, a novel pre-aeration facility named as gradual contraction aerators is proposed. Physical experiments were conducted to analyze and compare the hydraulic characteristics of the spillway with and without the aerators with the unit discharge, contraction angle, and contraction ratio as variables. The results demonstrate that after installing the aerators, aeration occurs effectively at both the upper and lower surfaces of the jet. The bottom air concentration along the spillway exceeds the safe threshold of 1.5%. The maximum time-averaged pressure on the step surfaces downstream of the aerator, measured to be only 1.92 kPa, occurs at the jet impingement point. This indicates that the jets from the aerators do not compromise the structural safety of the spillway. Key parameters, including the jet height, depth and inception point of quasi-uniform aerated flow were measured under various cases. Through multivariate nonlinear regression, empirical formulas relating these parameters to the Froude number, contraction ratio and contraction angle were established.
Trapezoidal labyrinth weirs, due to their increased crest lengths, can discharge more water for the same weir opening length and hydraulic head. However, due to their increased length and structural degrees of freedom, they can cause undesirable vibrations and oscillations under new flow conditions. In order to prevent these oscillations, it is necessary to somehow eliminate the negative pressures created under the unventilated water nappe on the downstream surface of the weir and the temporal and spatial variations of these pressures. These undesirable effects can be partially or completely prevented by the nappe breaker devices to be used on the labyrinth weirs. Within the scope of this study, the hydraulic performance of a trapezoidal labyrinth weir with and without nappe breakers was analyzed using a three-dimensional CFD-based numerical model under free-surface and turbulent flow conditions. The analysis results indicated that sub-atmospheric pressures in regions near the crest, where under-nappe pressures play a critical role, were reduced by 54%. Additionally, the hydrostatic pressures at the crest experienced an average reduction of 12%. Furthermore, the standard deviation of pressure fluctuations along the crest length, which could contribute to weir vibrations, was decreased by 27% due to the implementation of nappe breakers.
The water quality of urban rivers is reported to be polluted due to the discharge of untreated wastewater and the dumping of solid waste, resulting in critical damage to the river ecosystem. This study focuses on the Mula-Mutha River in Pune, Maharashtra, India, which has been severely affected by urban development. The primary aim of this study is to develop a model of Mula-Mutha river for simulating river hydraulics and water quality parameters, such as DO and BOD. The work involves integrated water quality modeling, calibration and validation of 123 km river stretch from Khadakwasla reservoir to Daund. Close agreement was observed between simulated and observed values for DO and BOD at five representative locations of the study area. Process constants, including manning's n, first-order decay rate and half-saturation oxygen concentration, were tuned for the development of the model. Model efficiency of greater than 90% and a correlation factor of about 0.900 are achieved. Simulations conclude that a release of fresh water of 3 cumec can improve water quality for propagation of fish in an initial urban river stretch. The model can be used for evaluating and predicting water quality dynamics of urban rivers and studying strategies for urban river rejuvenation.
