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This work proposes the use of an array of yawed porous vanes to control the lateral bedload transport by locally steering bedform migration and maximize the amount of sediments redirected toward a potential sediment extraction system or bypass channel. A laboratory experiment was conducted in a quasifield-scale channel with an array of permeable vanes installed on one side, in live-bed conditions under bedload dominant regime, i.e., negligible suspended load. A baseline experiment without vanes was also performed for comparison. The evolution of migrating bedforms of different scales was tracked in space and time using a high-resolution, state-of-the-art laser scanning device. The bedload transport rate in the streamwise direction was first calculated using bedforms' geometry and migration velocity, and then spatially distributed over the entire monitored area using a new Eulerian-averaged grid-mapping method. This allowed us to introduce a new methodology to estimate the lateral bedload transport using control volume theory and applying mass conservation. Quantitative assessments of lateral bedload transport along the channel yield consistent results, suggesting that the vanes effectively move sediments laterally as intended. Under the investigated setup, the maximum lateral sediment transport rate ranges from 9% to 18% of the whole domain-averaged streamwise transport rate. The developed methodology also allowed to identify the location where sediment capture could be maximized for the given vane spatial distribution. Practical Applications: In river engineering, in-stream structures are used to control flow and sediment movement to prevent erosion, intake clogging, and habitat disruption. Submerged vanes are small, angled structures that are installed to redirect sediments toward a preferred direction by creating secondary flow circulations. This study tests experimentally an array of porous vanes in an open channel to measure and quantify the lateral displacement of sediment. Porous plates were selected to minimize local scour and anchoring requirements while directing flow, bedforms, and sediment laterally. The amount of sand moved laterally is measured by comparing the streamwise bedform transport within and outside of the vane array. The proposed vane array is part of a modular hydrosuction sediment bypass system being developed for low-head dams, which features inlets to collect coarse sediments and siphon them over the dam via a slurry conduit. The vane array is meant to be installed upstream of the collector to increase the lateral transport of coarse sediment toward the intake structures. Porous elements can potentially be replaced by vegetation and log structures for nature-based alternatives. [ABSTRACT FROM AUTHOR]

Bedforms are complex and varied features on riverbeds created by the interaction between flow and sediment particles. Bedform evolution is crucial for understanding sediment transport, bed resistance, and the ecological environment of rivers. In this study, a series of movable-bed dune experiments were conducted utilizing advanced 3D topographic laser scanning technology to precisely measure the 2D and 3D dune bedforms under various conditions. This enabled the detailed analysis of the bedform parameters, including the dune length and height, the crest height, and the trough depth. Furthermore, this study examined the relationship between bed resistance and dune morphology and investigated how the intensity of bedload transport affects bed resistance. The findings indicate that bedload mass transport on the riverbed significantly contributes to increased bed resistance. Given the limitations of the traditional bedload transport rate formulas for dune bedforms, this research introduces a new formula derived from the experimental data. The accuracy of this formula was confirmed using the nonlinear least squares method. Our study enhances the accuracy of sediment transport predictions and provides scientific support for river management and engineering practices. [ABSTRACT FROM AUTHOR]

In order to explore the applicability of the hardening soil constitutive model for numerical analysis of soft soil underground engineering in the Pearl River Delta region, and based on four different stress path triaxial tests, the mechanical properties and variation of constitutive model parameters of hardening soil were analyzed for the typical silty soil in this region. Research results have shown that lateral unloading and drainage conditions have significantly impact on the partial parameters of constitutive model, such as the strength parameters of c' and φ ', the stiffness parameters such as Eref 50, E ref ur and m, but the impact on the failure ratio Rf is relatively small. For the consolidated undrained lateral unloading condition, the main parameters of the constitutive model for typical silty soil in the Pearl River Delta region are shown as the reference secant modulus Eref 50 is 2.34 MPa, with reference to tangent modulus Eref oed is 1.59 MPa, with reference to the loading unloading modulus E ref ur is 11.67 MPa, with a failure stress ratio of Rf is 0.98, and the power exponent m related to stiffness stress level is 1.84; Among them: Eref 50 is 1.47 times of Eref oed, E ref ur is 7.34 times of Eref oed. The practice of a deep foundation pit of soft soil in the Pearl River Delta has proven that the constitutive model of hardening soil is suitable for simulating the mechanical properties of soft soil in this region. [ABSTRACT FROM AUTHOR]

River floods disrupt communication and transportation networks, damage buildings and infrastructure, destroy agricultural products and livestock, cause capital losses and endanger human life. Accurate and proper flood prediction and forecasting are major challenges in hydrology and water resources management. The aim of this study was to forecast and estimate the daily flows of three rivers in Iran using four tree-based data-mining methods, two ensemble bagging methods and the stochastic time series model Arima (auto-regressive integrated moving average). A comparison of these different methodologies is the main contribution of this work. Five statistical measures were used to evaluate the accuracy of these models based on 4 years of daily discharge flow data. The hold-out method was used to divide the data into training (70%) and testing (30%) sets. It was found that the ensemble tree-based chi-square automatic interaction detector provided the most precise forecasts. The overall results indicate that the data-mining methods of ensemble models and tree-based models improved the average accuracy of the models by 25.0% and 15.5% compared with the stochastic Arima model, respectively, indicating the superiority of their potential in capturing the non-linear behaviour of flow discharges. [ABSTRACT FROM AUTHOR]

Grade control structure (GCS) can be used to reduce erosion in river beds. They decrease the river bed scour by changing the flow regime and reducing its velocity. It is required to maintain the stability of these structures against the scour hole that generates downstream of them, so investigating the scour hole characteristics downstream of the GCS is inevitable. In the present research, the equilibrium scour holes downstream of GCS were investigated under three discharges (q=0.00467, 0.00583, 0.00700 m3/s.m) and two different sedimentation conditions (d50=0.082, 1.6 mm). The results show that in the constant GCS geometry and finer sediment, the maximum scour depth (ds) and maximum scour hole length (ls) increase. In the same sedimentary conditions and different geometry, when the slope of the GCS downstream face varied from 90° to 60°, ds increases, but ls decreases. Also, the hydraulic jump forms on the scour hole at high flow intensity, which has an essential influence on the geometry of the equilibrium scour hole. Comparison of ds/Hc between the present study and Ben Meftah and Mossa (2020) has R2=0.891 and RE=10.66%, which reveals acceptable compatibility between the present study results and previous ones. [ABSTRACT FROM AUTHOR]

Downstream pebble variability in river systems is assessed through various methods, with recent emphasis on efficient, time-saving semi-automatic processes involving photography and digital analysis. The Inaouène valley, however, lacked a comprehensive survey of its main channel using either manual or image-based methods. This study bridges this gap by combining both approaches to analyze the downstream evolution of surface pebbles' morphometric parameters along approximately 60 km of the Inaouène's middle reach. Our research focuses on two key aspects: grain size and particle shape. Results reveal a general downstream trend of size fining, increasing circularity and decreasing elongation, primarily attributed to abrasion and travel distance. Notably, this pattern is interrupted by localized variations associated with tributary inputs and sediment recycling processes. This study significantly contributes to the understanding of fluvial sediment dynamics in the Inaouène Valley. Its findings have broad implications, supporting ecological assessment and restoration efforts, while also informing decision-making in river engineering and management. By providing a comprehensive analysis of pebble characteristics and their downstream evolution, this research establishes a foundation for future geomorphological studies and practical applications in river system management. [ABSTRACT FROM AUTHOR]

Stream sediment transport results from a convolution of climate, weather, geology, topography, biology, and human influence. In addition to providing water and food security for rural dryland communities, sand dams—small weirs designed to trap only the coarse fractions of transported sediments in seasonal and ephemeral streams—highlight many complexities of geomorphological dynamics. Sand dams store water in interstitial riverbed pores and the size of deposited sediment particles largely determines the recoverability of stored water: Fine materials limit transmission and provide lower volumetric yield. In this study, we seek to identify a practical method for evaluating the theoretical effect of staged sand dam crest construction on key sediment‐trapping processes for a proposed dam site. We argue that the Rouse number provides a useful criterion for identifying regimes where the target material grades are trapped. These ideas were tested using sediment data collected in Kenya and US Army Corps of Engineers River Analysis System numerical simulations to evaluate the sensitivity of sedimentation processes to crest height. We show that constructing sand dams in stages results in more targeted trapping of coarse material. Sedimentation is shown to be more sensitive to variation in crest height than the flood hydrograph, especially when a dam's crest height is small. By introducing a method to assess the necessity and inform design of staged crest construction based on local flow dynamics, this study offers a framework for optimising sand dam performance in data‐scarce environments. This approach provides a means to balance construction costs with expected benefits, enhancing the sustainability and functionality of sand dams in arid and semi‐arid regions. [ABSTRACT FROM AUTHOR]

This study investigates the potential use of Yellow River sand (YRS) sourced from the lower reaches of the Yellow River in China as a sustainable and cost-effective substitute for quartz sand in Engineered Cementitious Composites (ECC). With an annual accumulation of approximately 400 million tons in this region, YRS presents a substantial resource. ECC specimens with 100% YRS replacement with quartz sand were subjected to various curing methods: natural, steam, standard, and sprinkler. Extensive mechanical testing including flexural, compressive, uniaxial tensile, and four-point flexural tests was conducted. Additionally, Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses investigated microscopic mechanisms influencing macroscopic mechanical properties. Finally, the mechanical properties of the YRS-ECC test block after 14 days of standard curing and the traditional sand ECC test block were compared and analyzed. The results indicate that ECC specimens with 100% YRS substitution under natural curing show an optimal ultimate tensile strain of more than 4%, providing the best resistance to the reduction in ultimate flexural load and deflection due to aging. Steam curing enhances flexural and compressive strength, achieving an ultimate flexural load of 5 kN and a maximum deflection of 4.42 mm at 90 days. SEM analysis revealed lower C-S-H gel density under natural curing and higher under steam curing, enhancing fiber pull-out in steam-cured specimens. The MIP tests demonstrated that natural curing had the highest porosity (32.86%) and average pore size (51.69 nm), whereas steam curing resulted in the smallest average pore size, with 44% of pores under 50 nm. Compared with traditional sand, it is found that the ultimate bending load and deflection of YRS-ECC are 5.7% and 9.4% higher than those of traditional sand ECC, respectively, and its ultimate tensile strength and strain are also improved. These findings highlight YRS as a sustainable alternative to natural sand in ECC, with natural curing proving the most effective for superior mechanical performance, including tensile strain, crack resistance, and durability. [ABSTRACT FROM AUTHOR]

To improve the economic benefits of river dredging engineering construction, studies have been undertaken to optimize construction period costs. This study suggests a scheme for optimizing schedule costs through the use of three algorithms: non-dominated sorting genetic algorithm with elite strategy, simulated annealing colony algorithm, and ant colony algorithm. To achieve the preliminary algorithm selection of construction duration cost, the objectives have single and multi-objective, and iterative models are constructed separately. The validation results showed that the simulated annealing algorithm achieved the optimal solution in single objective optimization after the 81st iteration. The optimal solution of genetic algorithm in multi-objective optimization was a construction period of 49 days and a cost of 1788.15 million yuan. The non-dominated algorithm reduced the construction period to 313 days, which can save 52 days of construction period and reduce costs by 52.32 million yuan. This optimization algorithm has high efficiency in predicting shorter construction periods and lower costs, and has strategic foresight in the decision plans of decision-makers. [ABSTRACT FROM AUTHOR]

Non-stationary sediment load analysis is critical for river engineering design and water resource management. Traditional sediment load frequency analysis methods usually assume stationarity, which can lead to inconsistent results in a changing environment because they cannot account for factors such as time variations. Here, we use generalized additive models for location, scale and shape (GAMLSS) to establish non-stationary models with time, precipitation and streamflow as covariates (named Model 1 and Model 2, respectively), and compare their fitting effects with stationary models (parameters unchanged: Model 0). In this study, the sediment load of the Jinsha River Basin in southwest China was analyzed. Outcomes indicate that: (1) the research area's sediment load decreased significantly, with a significant change point in 2002 (p < 0.1); (2) the goodness of fit indices (global fitting deviation: GD, AIC criterion and SBC criterion) based on Model 2 are smaller than the values of the other two models. The other two models' sediment load quantile design values are within Model 2's range. (3) Compared with Model1, precipitation and streamflow as covariates in Model 2 are more able to capture the non-stationary features of sediment load frequency. Furthermore, Model 2 can more accurately forecast future changes in sediment load when external physical factors are considered. The findings of this research can serve as a scientific foundation for decision makers to carry out water conservancy planning and design and river management and development. [ABSTRACT FROM AUTHOR]

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Understanding the ecological conditions of vegetation growth in water sources is vital to appraise the influence of vegetation on river engineering. Based on the experimental information that is accessible, the consequences of vegetation on flow resistance is described as an alteration in the drag coefficient and the planned area. The current study analytically estimates the vertical distribution of stream-wise velocity in open-channel flow while considering rigid and flexible vegetation. The flow is vertically separated into top free water layer and bottom vegetation layer using the projected deflection height of both vegetation. Related momentum calculations for each layer are then derived. Based on the gathered experimental data, a 3D numerical model with various simulation situations is used to model, calibrate, and evaluate the artificial cylinders. A considerable deflection analysis is utilised to calculate the velocity-dependent stem height. This has proven to be more precise compared to formerly deflection investigation. The estimated outcomes show that precise predictions may be made for the vertical contours of vertical Reynolds shear stress based on mean horizontal velocity. The numerical simulations demonstrate that plant flexibility reduces the vertical Reynolds shear stress and prompted flow resistance force of the vegetation. [ABSTRACT FROM AUTHOR]

Scouring is considered a major contributor to bridge failure across the world. The expansion of the scour hole can lead to instability of the bridge structure. Consequently, scour depth prediction is considered a common river engineering practice to take necessary controlling measures. Accordingly, this study investigated the impact of perforated collars of different shapes on scouring around bridge piers. It was found that the scour further decreased as the collar shape was changed from triangular to rectangular. By installing triangular, circular, square, and rectangular perforated collars with the same hole diameter (d/D) of 0.1, maximum scour depth respectively decreased by 35.2, 37.4, 38.4, and 50.9% in comparison with the collarless bridge pier. Installation of the triangular, circular, square, and rectangular perforated collars with a hole diameter (d/D) of 0.15 reduced scouring respectively by 27.7, 31.6, 33.4, and 45.8% compared to the collar-less pier. Scouring respectively decreased by 16.6, 22.3, 24.7, and 27.6% compared to the collar-less pier by installing the triangular, circular, square, and rectangular perforated collars with a constant hole diameter (d/D) of 0.2. Scouring increased by 29.7% on average at all velocities as the diameter of the collar hole (d/D) increased from 0.1 to 0.2. Furthermore, scouring increased with increasing velocity. Scouring was found to increase by 94.7% on average with a rise from 0.54 to 0.95 of the flow intensity (V/Vc). [ABSTRACT FROM AUTHOR]

River bank protection is vital in hydraulic river engineering to preserve natural rivers, lands, and critical constructions such as bridges. Spur dikes are erosion-protective structures that protrude outward from the river bank in different orientations to deflect the flow away from the riverbank. The present experimental study provides insight into the temporal variation in bed morphology and scours around rectangular-shaped spur dikes with different orientations, such as 60º, 90º, and 120º. Also, maximum scour depth (MSD) is developed compared to the condition when downward seepage is applied. The experiments examined the suitability of various spur dike orientation configurations and the scour development over time, specifically at intervals of 2, 12, and 24 hours, and compared with 24 hours (Seepage). Results showed that the orientation angle of 90º generated the highest scour depth, while the least scour depth was found with an orientation angle of 120º. The downward seepage intensifies the motion of sediment particles and leads to an escalated particle detachment, resulting in deeper scour depressions. The development of scour depth is initiated from the spur dike tip and reaches its maximum there. The deposition of sand particles shifted downstream, and a dune-like structure formed near the second spur dike. [ABSTRACT FROM AUTHOR]

Short-term dramatic degradation of a riverbed poses a great threat to the river and functioning of infrastructure in its vicinity. In this paper, a straight flume experiment was conducted to measure the velocity, water level, riverbed elevation and riverbed morphology under different experimental conditions. This was combined with the SfM (structure-from-motion) method to generate riverbed digital elevation models and orthomosaic, and the impact of a flexible net on the riverbed evolution of a degrading channel was studied. The study reveals that, under the action of the flexible net, the degradation mode of the riverbed changes from parallel to rotational degradation with the erosion datum as the fulcrum, and with an increase in the longitudinal length of the flexible net, the riverbed's protection efficiency grows. The flexible net can effectively limit the movement of sediment under the net, and the finer sediment silting raises the erosion datum elevation. The location and morphological characteristics of the downstream scour holes are observed to be greatly affected by the deformation of the erosion datum. The scour hole shows an asymmetric distribution because of uneven scouring of the flow to the downstream riverbed. The research results could provide guidance in the management of degrading channels. [ABSTRACT FROM AUTHOR]

By decreasing the entrained air flow discharge and improving the hydraulic characteristics of vertical shaft spillways, Marguerite-shaped inlets (MSIs) can mitigate the effects of swirling flow surrounding their inlet. The hydraulic and hydrodynamic characteristics of flow around MSIs under orifice flow regime were numerically investigated, applying different geometrical parameters. This inlet configuration can decrease the strength of swirling flow and increase the flow discharge through the shaft. The finite-volume method and the re-normalisation group k–ε turbulence model were employed to solve the governing equations of motion in a cylindrical coordinate system and a two-phase air–water flow on the water free-surface. Increasing the height and length of the blades of the MSIs was found to increase the area of the barriers against swirling flow, weaken the swirling flow strength, engender a more uniform flow and lower the water free-surface level. Extremely long or high blades, however, resulted in an intense collision of the flow with the spillway and increased the water free-surface level and the swirling flow strength at the MSI. [ABSTRACT FROM AUTHOR]

The formation conditions of maximum- and minimum-wave jumps were experimentally investigated. A total of 110 wave-type jump experiments were carried out for several discharges, supercritical upstream and subcritical downstream water depths and drop heights. The experimental results revealed that the influential parameters on wave-type jumps are the upstream Froude number and the relative drop height. As the classical hydraulic jump equation is not sufficient to define conjugate depths of wave-type flow, empirical equations were developed for defining the conjugate depths of maximum-wave jumps and minimum-wave jumps (for which insufficient experimental data are available in the literature). The agreement between calculated and measured conjugate depths was good. It was also found that the value of the lower limit for the upstream Froude number is not constant for the formation of a maximum-wave jump – it depends on the relative drop height. Furthermore, the experimental results showed that the energy-dissipation ratios of maximum- and minimum-wave jumps are equal to or larger than those of classical hydraulic jumps. For this reason, wave-type jumps may be preferred at stilling basins with drops along with A-jumps. [ABSTRACT FROM AUTHOR]

Migrating bedforms in alluvial rivers can exacerbate scour damage at instream structures and lead to structural failure. This study investigates the interaction between scour at instream structures and bedform migration. Both two-dimensional (submerged weirs) and three-dimensional (uniform and complex piers) structures are considered. Two components constitute live-bed scour depth: the dynamic scour amplification Δds caused by bedforms and the local flow-induced baseline scour depth dsNB. Results show that, for 2D structures, the baseline scour depth is negligible, while the live-bed scour is mainly caused by approaching bedforms. The dynamic scour amplification normalised by the approaching bedform height (Δds/Hb) decreases with the decrease of upstream angle and varies between 0.5 and 2. For uniform 3D structures, the local flow could cause a considerable baseline scour depth, and Δds/Hb varies between 0.25 and 0.5 and decreases with the increase in the flow capacity to damp bedforms. For complex 3D structures, flow pressurisation beneath the pile-cap magnifies Δds/Hb to near 1. In general, Δds/Hb is inversely correlated with ds_NB/y0, where y0 is flow depth. New equations are proposed for estimating the dynamic scour amplification at various instream structures with design rules recommended. [ABSTRACT FROM AUTHOR]

Scour is a significant concern for bridge design/maintenance, and scour countermeasures are often used to prevent or reduce erosion caused by scouring. The W weir is a grade control structure serving many purposes, including scour control at bridge piers. A series of laboratory experimental runs was conducted, changing the size, height and location of the pier in relation to the weir to optimise the structural configuration of the downscaled W weir. These experiments revealed that the scour hole profile upstream of the downscaled W weir changes with weir height. At a weir height of 1.0D (D = diameter of pier), two small depressions of almost identical size were observed inside the main scour hole, one just in front of each upstream apex of the W weir. One cone-shaped scour hole was observed when the W weir height was 0.5D with its maximum depth in between the upstream apexes. Reduction of scour in front of the pier was greater when the weir height was 1.0D. The maximum scour control achieved among all different structural combinations of downscaled W weir was 47.66%. This was achieved when the downscaled W weir was 2.0D in size and 1.0D high, placed 2.0D distant from the pier. [ABSTRACT FROM AUTHOR]

Knowing the amount of sediment transported in rivers is important in river and hydraulic engineering. In essence, sediment transport process is very complex, whose direct measurement is not only challenging but also costly. In this regard, several equations have been developed to estimate sediment discharge, while their estimations may be an order of magnitudes different from one another under specific circumstances. In a bid to improve the estimation of sediment transport, this study proposed a new data-driven equation based on 543 reliable field measurements at 25 rivers using the Modified honey bee mating optimization (MHBMO) algorithm. The data include mean flow velocity, water surface slope, mean flow depth, median particle size, water surface width, suspended load, and bed load measured in the field. The performance of the new equation was compared to those of Yang, Engelund and Hansen, Shen and Hung, and Ackers and White using 6 metrics. Moreover, another nature-inspired optimization algorithm, i.e., genetic algorithm (GA) was employed to enhance the comparison. Based on the results, the MHBMO-based equation outperformed other estimation models and served as the best method in the ranking analysis. For instance, it improves the determination coefficient of Yang's equation, which is one of the widely-used equations recommended by the United States Bureau of Reclamation by 15.2%. Despite being ranked the second, the GA-based equation was only marginally less precise than the MHBMO-based model. Furthermore, the sensitivity analysis indicates that the sediment load is mostly sensitive to mean flow depth. Finally, it is postulated that applications of nature-inspired algorithms can help to improve the estimation of sediment transport. [ABSTRACT FROM AUTHOR]

Obtaining river or sea pebbles from local resources for concrete production is considered an economical and eco-friendly alternative, particularly in marine and island-offshore engineering. However, the resulting changes in the mechanical properties of these concrete have attracted attention. This study investigates the compressive behavior of concretes where river or sea pebbles partially (i.e., 33% and 67%) or fully (i.e., 100%) replace traditional gravel as coarse aggregate, using a noncontact full-field deformation measurement system based on digital image correlation (DIC). Compared to the traditional gravel concrete (GC), compressive strengths of the river pebble concrete (RPC) at constitution rates of 33%, 67%, and 100% decreased by 6.5%, 29.8%, and 38.9% while those values of the sea pebble concrete (SPC) decreased by 13.1%, 32.7%, and 44.3%, respectively. Meanwhile, SPC exhibited slightly lower compressive strength than RPC. The peak strains of both SPC and RPC decreased at lower substitution rates, although their stress-strain curves resembled those of GC. In contrast, RPC and SPC at higher substitution rates exhibited a noticeable stage of load hardening. Full-field deformation data and interfacial characteristics indicated that the compressive failure modes of both RPC and SPC showed significant interfacial slipping between pebbles and mortar with increasing coarse aggregate substitution rates. In comparison, fractures in coarse aggregate and mortar were observed in damaged GC. The study demonstrated that the spatio-temporal compressive deformation response and failure modes of SPC and RPC were distinct due to the introduction of pebbles, providing insights for engineering applications of river/sea pebble concrete in practical offshore or island construction projects. [ABSTRACT FROM AUTHOR]

Climate change elevates the threat of compound heat and drought events, with their ecological and socioeconomic impacts exacerbated by human ecosystem alterations such as eutrophication, salinization, and river engineering. Here, we study how multiple stressors produced an environmental disaster in a large European river, the Oder River, where a toxic bloom of the brackish-water planktonic haptophyte Prymnesium parvum (the "golden algae") killed approximately 1000 metric tons of fish and most mussels and snails. We uncovered the complexity of this event using hydroclimatic data, remote sensing, cell counts, hydrochemical and toxin analyses, and genetics. After incubation in impounded upstream channels with drastically elevated concentrations of salts and nutrients, only a critical combination of chronic salt and nutrient pollution, acute high water temperatures, and low river discharge during a heatwave enabled the riverine mass proliferation of B-type P. parvum along a 500 km river section. The dramatic losses of large filter feeders and the spreading of vegetative cells and resting stages make the system more susceptible to new harmful algal blooms. Our findings show that global warming, water use intensification, and chronic ecosystem pollution could increase likelihood and severity of such compound ecoclimatic events, necessitating consideration in future impact models. [ABSTRACT FROM AUTHOR]

Human-induced breaches in the dikes of the major river systems were a common phenomenon in late imperial China. The article examines cases mainly related to the Yellow River and how these cases were dealt with on the basis of the legal code. While the extensive coverage of such cases in legal documents is an important reminder of the high degree of attention that the state paid to hydraulic installations, the phenomenon also needs to be understood as an manifestation of societal conflicts resulting from the pressures of the demographic and environmental developments of China in the late imperial period. [ABSTRACT FROM AUTHOR]

Riverbed elevations play a crucial role in sediment transport and flow resistance, making it essential to understand and quantify their effects. This knowledge is vital for various fields, including river engineering and stream ecology. Previous observations have revealed that fluctuations in the bed surface can exhibit both multifractal and monofractal behaviors. Specifically, the probability distribution function (PDF) of elevation increments may transition from Laplace (two‐sided exponential) to Gaussian with increasing scales or consistently remain Gaussian, respectively. These differences at the finest timescale lead to distinct patterns of bedload particle exchange with the bed surface, thereby influencing particle resting times and streamwise transport. In this paper, we utilize the fractional Laplace motion (FLM) model to analyze riverbed elevation series, demonstrating its capability to capture both mono‐ and multi‐fractal behaviors. Our focus is on studying the resting time distribution of bedload particles during downstream transport, with the FLM model primarily parameterized based on the Laplace distribution of increments PDF at the finest timescale. Resting times are extracted from the bed elevation series by identifying pairs of adjacent deposition and entrainment events at the same elevation. We demonstrate that in cases of insufficient data series length, the FLM model robustly estimates the tail exponent of the resting time distribution. Notably, the tail of the exceedance probability distribution of resting times is much heavier for experimental measurements displaying Laplace increments PDF at the finest scale, compared to previous studies observing Gaussian PDF for bed elevation. Plain Language Summary: The evolution of riverbed elevations is difficult to describe due to its highly variable and strongly non‐linear nature. Understanding and quantifying the dynamics of riverbed elevations are important for river engineering and stream ecology, and serve as the basis for numerical models of predicting sediment transport as well as interpreting stratigraphy from the past records. Through laboratory experiments, we have observed that the form of elevation increment PDF can change from Laplace to Gaussian as the timescale increases. This phenomenon is successfully modeled in this paper for the first time by the fractional Laplace motion, which essentially generates bed elevation series for the evolution of bed surface height at a certain spatial location of the bed. This series contains information on how long a bedload particle can rest (resting time) in the riverbed before it can be re‐entrained to move downstream, the determination of which by other means (e.g., particle‐tracking measurements) is challenging. By extracting resting times embedded in this bed elevation series, we obtain statistics (i.e., the tail behavior of the resting time distribution) that are key for correctly modeling the transport of bedload particles, and more specifically, that can help us to understand the anomalous bedload diffusion process. Key Points: The Fractional Laplace motion (FLM) can be used to describe the evolution of the distribution of bed elevation increments over different timescalesCorrectly predicting bed elevation fluctuations at the finest timescale is critical for estimating resting times for bedload tracer transportFLM model provides a means of robustly estimating the tail exponent of the resting time distribution in case of insufficient data series length [ABSTRACT FROM AUTHOR]

In smooth prismatic open channels, the boundary shear stress is obtained from continuity and momentum equations. The shear stress is a function of gravity, secondary flow and gradient velocity. In this research, semi-analytical equations were developed to estimate the average boundary shear stress in smooth rectangular and trapezoidal open channels with side slopes of 0.5, 1.0, 1.5 and 2.0 using conformal mapping techniques. After dividing the channel cross-section into bed and wall sub-sections, a previously presented method was used to estimate the average shear stress of the bed and the wall in open channels. For the studied case, in the first estimate of shear stress, the secondary current and constant eddy viscosity were neglected. After determining correction factors for secondary currents and eddy viscosity, the second estimation provided a good match with experimental measurements of the average shear stress for all aspect ratios. [ABSTRACT FROM AUTHOR]

Meandering channels are common in natural rivers, especially in lowland alluvial plains. In this research, a meandering channel was designed in order to explore the effect of sediment supply on the flow characteristics. The water level, three-dimensional (3D) instantaneous velocity and riverbed elevation were measured using a digital wave altimeter, a 3D acoustic Doppler velocimeter and a 3D laser scanner, respectively, and the flow characteristics with and without sediment supply were compared. Under the same discharge, the transverse slope of the water surface in the case with sediment was larger than that without sediment and the change was steep; the change in the longitudinal slope of the water surface was small in the upper half bend and large in the lower half bend. By increasing the water discharge, the number of secondary flow vortices at the apex of the meandering channel increased. The trends of the mainstream lines with and without sediment supply were roughly opposite and the difference between them decreased with increasing discharge. The lateral and vertical turbulence intensities of the flow near the outer bank were larger in both cases (with and without sediment). In the case with sediment, the turbulent kinetic energy of the cross-section was larger near the bed and the water surface. [ABSTRACT FROM AUTHOR]

This paper analyses flood frequency and performs flood simulation modeling along the Chenab River from Trimmu–Panjnad reach, to simulate flood 2014 and identify resultant flood inundated areas, under different return periods of floods. The aim of this study is to assist policymakers in designing efficient flood mitigation policies for the Chenab River, Pakistan which has been frequently hit by floods, especially in September 2014. Flood frequency analysis was carried out using log-Pearson type III (LP3) distributions to estimate peak flows with various return periods. The peak floods were incorporated into the Hydrologic Engineering Centre River Analysis System (HEC-RAS) model to predict the relevant flood levels for river stretches from Trimmu to Panjnad reach. The HEC-RAS model outcomes were integrated with ArcGIS to prepare flood risk maps that helped in identifying different flood-vulnerable areas. Two flood risk zones were developed; low to moderate and high to very high flood risk zones. The simulation analysis of a 50-year flood period showed that about 400% of the land would be submerged when compared to normal river flow. The simulation of the flood 2014 extent was found to clearly match the MODIS images provided by the United Nations Satellite Centre (UNOSAT). The surface areas of floods having different return periods, were also estimated. The utilization of the HEC-RAS model for simulating the 2014 flood, presents an opportunity for flood policymakers to enhance their understanding and formulate effective risk reduction strategies in the Chenab River basin. [ABSTRACT FROM AUTHOR]

Local river interventions, such as channel narrowing or side channels, are often necessary to maintain safety, ecology, or navigation. Such interventions have different effects on the river's bed morphology during periods of high‐ and low‐discharge events. Mapping the bed‐level variations for different discharge levels and understanding these effects can provide new opportunities for the design of interventions in multifunctional rivers. At any moment, the local bed level in a river is composed of bed‐level changes that occur at various spatial and temporal scales. These changes consist of bed aggradation/degradation trends on a large scale, on an intermediate scale bed‐level variations as a result of discharge fluctuations, and on small‐scale moving river bed forms like dunes. Using the river Waal in the Netherlands as a case study, we analyze the intermediate‐term bed‐level changes resulting from discharge fluctuations (dynamic component) and propose adaptations to the design of floodplain interventions such that possible negative impact on the local bed‐level changes is minimized. Time series of bed levels along two 10 km stretches of the case study are considered for a period of 16 years (2005–2020). Using a wavelet transform, we isolate bed‐level variations resulting from discharge events. These bed‐level variations are presented based on the magnitude of the discharge event and are compiled in an interactive atlas of river morphodynamics, allowing us to mitigate the impact of interventions. This will help river managers in the design of interventions and lead to improved management, operation, and maintenance of multifunctional rivers. [ABSTRACT FROM AUTHOR]

The main cause of the destruction of many bridges built on rivers is local scour around their piers, especially during floods. The failure and destruction of bridges, in addition to financial and human losses, also cuts the communication path to flood-affected areas that need assistance and doubles the damages. The present study examined the effect of transverse distance between vertical rectangular piers in the pier group on the local scour around them in a straight channel under different hydraulic conditions (Froude numbers 0.160, 0.186, 0.211, and 0.245). The piers used in this study were rectangular 2.5 cm wide and 3.5 cm long. The longitudinal distance between the piers was fixed and 4 times the width of the pier (10 cm), and the transverse distance between the piers was 1, 3, 5, and 8 times the width of the pier, which were equivalent to 2.5, 7.5, 12.5 and 20 cm. The results showed that with an increase in the transverse distance between the piers, the maximum scour depth first began to decrease and reached the minimum value at a distance three times the width of the pier, then with an increase in the transverse distance, the maximum scour depth increased and reached the maximum at a distance of 8 times the width of the pier. The maximum scour depth at a distance of 8 times the width of the pier was obtained on average 34% more than the distance of 3 times the width of the pier. [ABSTRACT FROM AUTHOR]

While research on the hydrologic impact of different types of stormwater control measures (SCMs) is extensive, little research exists linking urbanization, widespread implementation of SCMs and channel stability in headwater streams. This study evaluated whether the unified stormwater sizing criteria (USSC) regulations in the state of Maryland, USA, which require the use of both end‐of‐pipe and distributed, small‐scale SCMs, protect channel stability. To achieve this goal, a coupled hierarchical modelling approach utilizing the Storm Water Management Model (SWMM) and the Hydrologic Engineering Center River Analysis System 6.3 (HEC‐RAS) was developed to predict changes in streamflow and sediment transport dynamics in a first‐order gravel‐bed, riffle‐pool channel. Storm event discretization revealed that 88% of observed storm events during the 16 years (2004–2020) had durations less than 18 h and that the greatest peak flows resulted from storm events with durations less than 24 h. HEC‐RAS simulation results also showed that both channel degradation and aggradation, as high as 1.2 m, will likely occur due to regulations which require the use of 24 h duration design storms with a target stormwater detention time rather than bed material sediment transport limits. Overall, this study provides valuable insights into the complex interactions between SCM practises, flow regimes and sediment transport dynamics in heavily urbanized watersheds. It is recommended that SCMs be designed using a continuous simulation model with at least 10 years of continuous rainfall data. Furthermore, to protect channel stability, the SCM design goal should focus on maintaining pre‐development sediment transport regimes across a range of flows. [ABSTRACT FROM AUTHOR]

To comprehensively assess the impact of sediment retention by reservoirs on downstream fluvial processes and flood control, this study analyzed sediment and cross- sectional data collected during the sediment retention periods at the Sanmenxia ( SMX) and Xiaolangdi ( XLD) reservoirs. The research explored patterns of channel aggradation and degradation, flood scouring efficiency, channel geometric characteristics, and flood discharge capacity in the Lower Yellow River (LYR). The results revealed uneven scouring throughout the LYR, with notable riverbed coarsening—the median grain size of the bed sediment increased by 2. 1 to 2. 5 times that before scouring. Above Gaocun, enhanced flood discharge capacity at equivalent water levels was observed, and the larger channel storage can temporarily detain sediment from the XLD Reservoir. However, following riverbed coarsening, the depletion of fine and medium silt led to a significant decline in channel scouring efficiency over time. The long-term sediment and water management by the reservoirs, coupled with advanced river engineering in the LYR, shifted the focal area of channel scouring downstream during the XLD Reservoir′s sediment retention period compared to that during the SMX period. This shift was accompanied by an increase in riverbed coarsening and a marked decrease in scouring efficiency. These findings provide a scientific foundation for defining technical parameters for reservoir sediment and water regulation. [ABSTRACT FROM AUTHOR]

The Abassia-Shammia is a meandering stream in Najaf province. Predicting and estimating the flow behavior of meandering rivers is crucial for designing hydraulic structures in an accurate manner in the vicinity and conducting environmental and ecological studies. The hydraulic properties of an alluvial stream are typically subject to change due to its location between two barrages. In this study, HEC RAS 2D, developed by the Hydrologic Engineering Center’s River Analysis System, was employed to simulate the hydraulic performance of the Euphrates River reach between two series of barrages, i.e., Abbassia and Shammia. Reliable input data, such as Digital Elevation Models (DEMs), land cover classification, and data for the 2023 hydrograph as a boundary condition, were utilized to develop the hydraulic model. The model was calibrated by using the observed water surface elevation from field measurements downstream of Abbassia to match the ones calculated by the model. Hence, the hydraulic model of the Euphrates River was created using an appropriate Manning roughness coefficient value (n = 0.04) based on the most suitable values of statistical indices, correlation coefficient (R²), and root mean squared error (RMSE) to assess the agreement between the observed and simulated data throughout the calibration and validation phases. To visualize the HECRAS2D output, the hydraulic maps for the study region were presented. The ten cross-sections from the field study (investigated at the same period of flow hydrograph) were presented for modeling to emphasize the river's hydraulic behaviors. Based on the results, the water surface elevation ranged between 19.1–29.2 m.a.s.l., and the flow velocity was 2.50 m/s. Meanwhile, the values of bed shear stress (Pa) and the water depth (m) ranged between 0.1 Pa and 8.93 m for the entire river. The results also proved the superiority of the HEC RAS2D model to reliably represent the hydraulic performance of the Euphrates River reach located between the two barrages. [ABSTRACT FROM AUTHOR]

Suspended sediment load is an indicator of erosion in watersheds. Therefore, accurately estimating the daily suspended sediment load (DSSL) is an important issue in river engineering. In this research, Artificial Neural Networks (ANN), Genetic Expression Programming (GEP) intelligent models, and the traditional Sediment rating curve (SRC) model were used to estimate DSSL in the Kasilian and Rood Zard watersheds in Iran. The input data to the models included instantaneous flow discharge (Q), average daily flow discharge (Qi), average daily flow discharge with a delay of three days (Qi-1,Qi-2,Qi-3), average daily precipitation (Pi), and average daily precipitation with a delay of three days (Pi-1,Pi-2,Pi-3); the output data was DSSL. In this research, the selforganizing map (SOM) artificial neural network was used for data clustering, and gamma test (GT) methods were used to obtain the best combination of input variables to intelligent models. The results showed that the best models for estimating DSSL in the Kasilian and Rood Zard watersheds were respectively the ANN model with an activation function of tangent sigmoid with the best combination of input variables (Qi-1,Qi-2,Qi-3,Pi,Pi-1,Pi-2,Pi-3) and the GEP model with the input variables Qi,Qi-1,Qi-2,Pi,Pi-1,Pi-2,Pi-3. The statistical values of the ANN-tangent sigmoid model for the Kasilian watershed were MAE=231.4 (ton day-1), RMSE=578.6 (ton day-1), NSE =0.98, and R²=0.98; these values for the GEP model in the Rood Zard watershed were MAE=475.7 (ton day-1), RMSE=1671.9 (ton day-1), NSE=0.99, and R²=0.99. The SRC model in the Kasilian watershed with R²=0.34 and NSE=0.08 and the Rood Zard watershed with R²=0.59 and NSE=-0.11 showed the low accuracy of this model in estimating DSSL. [ABSTRACT FROM AUTHOR]

Prediction of rainfall-runoff process, peak discharges, and finally flood hydrograph is essential for flood risk management and river engineering projects. In most previous studies in this field, the precipitation rates have been entered into the models without considering seasonal and monthly distribution. In this study, the daily precipitation data of 144 climatology stations in Iran were used to evaluate the seasonal and monthly pattern of flood-causing precipitation. Then, by determining the rainy seasons and seasonal fit of precipitation with a probabilistic model and using regional precipitation, a semi-distributed conceptual model of rainfall-runoff (MORDOR-SD) was trained and validated using the observed discharge data. Flood prediction was performed using climatic data, modeling of hydrological conditions, and extreme flow data with high performance. According to the results, the Nash–Sutcliffe and Kling–Gupta coefficients were 0.69 and 0.82 for the mean daily streamflow, 0.98 and 0.98 for the seasonal streamflow, 0.98 and 0.94 for the maximum discharges, and 0.57 and 0.78 for low flows, respectively. Moreover, the maximum daily discharges in different return periods were estimated using the results of the MORDOR-SD model, considering the probability distribution function of the probabilistic model of central precipitation (MEWP), the probabilistic model of adjacent precipitation, and probability distribution function of the previous precipitation. Finally, the extreme flows were predicted and compared using different methods including the SCHADEX, regional flood analysis, GRADEX, and AGREGEE. The results showed that the methods GRADEX, AGREGEE, and SCHADEX have the highest performance in predicting extreme floods, respectively. [ABSTRACT FROM AUTHOR]

Model experiments were conducted on the hydraulic characteristics of air-water two-phase flow inside the bottom outlet of shaft spillways as a result of natural air suction from air-core vortices at the pipe intake. Experiments were performed in a cylindrical reservoir 2 m in diameter and 1 m high, under a swirling flow around the intake, investigating the most severe two-phase flow regimes. Three different vertical pipe intakes, attached to the floor of the reservoir at its centre, were examined for different flow discharges, establishing different vortex types. Results indicate that the void fraction decreases by changing the type of swirling flow. For a constant submergence depth, reducing the intake pipe diameter or increasing its height led to an increase in void fraction and two-phase slug flow wave velocity, length and frequency. However, by the increase in Kolf number, the frequency of slug waves reduced and the two-phase flow pressure inside the bottom outlet was increased. The relationships between two-phase flow hydraulic characteristics and regimes inside the bottom outlet and types of vortices at the intakes will be of interest to both scientific research and design engineers, to increase the efficiency and safety of pressurised waterway systems. [ABSTRACT FROM AUTHOR]

The occurrence of scour around bridge elements due to the transportation of bed material during flood events can cause serious structural damage and loss of life. Increased uncertainties in precipitation and runoff predictions due to climate change make this phenomenon more complex and dangerous. Bridge scour countermeasures should thus be more focused on decreasing scour formation around bridge elements. In this study, abutment scour under clear-water conditions with constant flow intensity was conducted and collars were tested as scour countermeasures around semi-circular end bridge abutments. The experimental study was performed in a rectangular channel with an almost uniform cohesionless bed material for 3 h with and without collars. Collars of various lengths located at different elevations around the abutments were tested to investigate the effect of collars on scour development. The results of the study showed that the scour depth decreased with increasing collar width and when the collar was placed below the bed level for a given abutment length. The results were compared with those of similar earlier studies to show the effect of abutment shape, size of the bed sediment and test durations on the development of scour depth around abutments. [ABSTRACT FROM AUTHOR]

Flood estimates based on stationary flood frequency models are commonly used as inputs to flood hazard mapping. However, changing flood characteristics caused by climate change necessitate more accurate assessments of the probabilities of rare flood events. This study aims to develop a flood hazard map based on the nonstationary flood frequency using a generalized extreme value distribution model for the Becho floodplain in the upper Awash River basin. The distributional location parameter was modeled as a function of rainfall amount of different durations, annual total precipitation from wet days, yearly mean maximum temperature and time as covariates. The one-dimensional Hydrological Engineering Center River Analysis System (HEC-RAS) hydraulic model with steady flow analysis was used to generate flood hazard map input, depth and velocity, and inundation extent for different return periods. The result indicated that the model as a function of rainfall, such as monthly rainfall (August) and annual wet day precipitation, provided the best fit to the observed hydrological data. Rainfall as a covariate can explain the variation in the peak flood series. The developed hazard map based on depth alone and the combination of depth and velocity thresholds resulted in more than 70% of the floodplain area being classified as a high hazard zone under 2, 25, 50, and 100-years return periods. The current study assists water resource managers in considering changing environmental factors and an alternative flood frequency model for developing flood hazard management and mitigation strategies. [ABSTRACT FROM AUTHOR]

Morphological studies are among the most important topics in river engineering, dealing with the geometric shape, bed form, and longitudinal profile of the waterway, cross-sections, deformations, and lateral migration of rivers over time. Researchers worldwide have noted the capability of satellite imagery and its integration with geographic information systems (GIS) to provide comprehensive information about river conditions and monitor spatial changes at different time intervals. In this paper, a new method is proposed to detect the current morphology of different parts of the Qizil Ouzan river and its main branches using a CNN neural network with support vector machine (SVM) and multilayer perceptron (MLP). The results of the studies show that the current meander length of the river is more than anything else the result of non-river factors such as stream piracy and mass movements like landslides and lateral collapses of waterways. Moreover, using GIS software, the meander and its changes over different time periods were obtained and compared with each other. Also, the present research aims to predict river morphological changes using image processing in MATLAB. The results demonstrate the efficacy of combining these two methods for predicting the morphological changes of the Qizil Ouzan River. [ABSTRACT FROM AUTHOR]

Assessing river water quality is crucial for human and ecological needs because of the deterioration of the river and escalated water pollution under the threats of anthropogenic activities. In order to assess river water quality, the Damodar River water was evaluated from the perspectives of spatio-temporal dynamics of ecological (organic pollution index or OPI and eutrophication index or EI), bacteriological (coliform count and comprehensive bathing water quality index or CBWQI), and overall water quality assessments (water quality index or WQI and comprehensive pollution index or CPI). The OPI reveals that 44.66% of water samples have heavy organic pollution; however, EI depicts that almost all water samples of Damodar River have severe eutrophication, especially in the pre- and post-monsoon seasons. Moreover, the fecal coliform count and CBWQI indicate the unsuitability of river water for bathing. The overall WQI portrays that 21.56%, 33.59%, and 22.47% of water samples have heavy pollution in pre-monsoon, monsoon, and post-monsoon, respectively. Moreover, 73.39% of water samples have low CPI indicating slight comprehensive pollution. This study also reveals that the pollution level in the Damodar River downstream of the Durgapur barrage is high among the other stations. The major reasons behind the severe contamination of Damodar River water are urban-industrial and agricultural effluents mixing into the river that lead to higher concentrations of BOD, DO, fecal coliform, COD, fluoride TSS, and turbidity in the river water. Thus, this study carries appreciated information on policy recommendations for the different stakeholders of the Damodar River basin including regional planners, agri-engineers, and ecological river engineers for sustainable river management. [ABSTRACT FROM AUTHOR]

Flow velocity in open channels is a fundamental hydraulic parameter with wide-ranging applications, including the development of rating curves and the study of sediment transport. While some river engineering projects may only require the calculation of average flow velocity, others, such as the design of hydraulic structures and stable channels, as well as the assessment of boundary shear stress, necessitate a more comprehensive understanding of flow dynamics, including the two-dimensional velocity distribution within open channels. To address this, various mathematical models have been proposed for estimating the two-dimensional distribution of flow velocity across transverse and depth directions. However, these models often come with complexities that hinder their practical application. In this research, we introduce a simplified numerical model that combines simplified Navier–Stokes equations with an eddy viscosity formula. This innovative approach aims to estimate velocity distribution in both rectangular and trapezoidal channels. The accuracy of our developed model hinges on the momentum transfer coefficient used in the eddy viscosity formula. Through the execution of the numerical model and the utilization of observational data, we determined the optimal value of the momentum transfer coefficient to be 0.241. To validate the effectiveness of our numerical model, we compared its predictions with laboratory data encompassing diverse hydraulic conditions. The results demonstrated a high level of accuracy, with the calculated velocity distribution and flow discharge differing by no more than 7.6% and 6.8%, respectively. [ABSTRACT FROM AUTHOR]

Erosion‐control measures in rivers aim to provide sufficient navigation width, reduce local erosion, or to protect neighboring communities from flooding. These measures are typically devised to solve a local problem. However, local channel modifications trigger a large‐scale channel response in the form of migrating bed level and sediment sorting waves. Our objective is to investigate the large‐scale channel response to such measures. We consider the lower Rhine River from Bonn (Germany) to Gorinchem (the Netherlands), where numerous erosion‐control measures have been implemented since the 1980s. We analyze measured bed level data (1999–2020) around four erosion‐control measures, comprising scour filling, bendway weirs, and two fixed beds. To get further insight on the physics behind the observed behavior, we set up an idealized one‐dimensional numerical model. Finally, we study how the geometry and spacing of the measures affect channel response. We show that erosion‐control measures reduce the sediment flux due to (a) lack of erosion over the measure and (b) sediment trapping upstream of the measure, resulting in downstream‐migrating incision waves that travel tens of kilometers at decadal timescales. When the measures are in close proximity, their downstream effects may be amplified. We conclude that, despite fulfilling erosion‐control goals at the local scale, erosion‐control measures may worsen large‐scale channel‐bed incision. Key Points: Erosion‐control measures reduce upstream incision and enhance downstream incision in an overall‐incising river systemThe net amount and extent of enhanced downstream incision are larger than the reduced incision upstreamFor multiple erosion‐control measures, the enhanced downstream incision increases with reduced spacing between measures [ABSTRACT FROM AUTHOR]

This paper presents a method to quantitatively assess the impact of ice-affected hydraulics on hydropower operations using the widely used Hydrologic Engineering Center River Analysis System (HEC-RAS) hydraulic model. The model was used to identify historical periods where downstream river ice growth reduced the net head on a US Army Corps of Engineers dam on the Pend Oreille River in Idaho, USA. The model was used to create curves of projected stage impacts based on border-ice and continuous bank-to-bank ice formation scenarios. The temperature modelling capabilities in HEC-RAS were used to hindcast ice formation periods on the river that were validated with shore-based webcam data. These results provide a framework that can be applied to other rivers with hydropower generation, particularly sites where an open-water HEC-RAS model exists. [ABSTRACT FROM AUTHOR]

This work presents an experimental study of the fluctuating properties of hydraulic jump rollers for high-Froude-number and pre-aerated inflow conditions, to investigate the validity of empirical relationships in the literature that are derived typically from experiments for smaller Froude numbers and clear-water approach flows. The jump roller fluctuations are evaluated in terms of the dimensions of the roller surface profile, the fluctuation magnitudes and frequencies of the instantaneous jump toe positions and water elevations, including at the tailwater surface, and the formation frequency and advection velocity of internal vortices in the shear layer. The effects of pre-aeration are found primarily in the length-scale properties such as jump length and surface fluctuation magnitudes, while the time-scale properties such as characteristic frequencies of the unsteady motions are not affected. Extrapolation of existing quantitative prediction of jump roller dynamic properties to high-Froude-number flow conditions should be performed carefully. An assessment of the fluctuating bubble counts within fixed time intervals yields close frequencies between the bubble grouping motions in the shear layer and the jump toe and tailwater wave motions, thus implying possible correlations between the roller surface deformations and air entrainment. [ABSTRACT FROM AUTHOR]

Hydrodynamic model outputs are used in urban flood risk modelling, flood alert systems, and Monte Carlo hazard assessment. This study tackles an under-explored challenge wherein regular updates to the spatial characteristics of the watershed -- due to factors such as changing land use -- alter the watershed's response to rainfall forcing, thus rendering existing model outputs obsolete. Because state-of-the-art hydrodynamic models are computationally expensive, frequently re-running simulations can be costly. Modularization addresses this problem by requiring re-computation only for a limited domain affected by the land use changes. This article introduces a novel approach by modularizing the 2D domain into independent sub-domains before ('discrete') and after ('abstract') the numerical computations. Using the Hydrologic Engineering Center River Analysis System (HEC-RAS) 2D model of a large urban watershed in Houston as an illustrative and generalizable testbed, we show that both the discrete and abstract modularization closely approximates the results from rerunning the entire model. The computational cost of modularization scales linearly with model size for memory requirements as storing the solution on the interior boundaries (discrete) or throughout the domain (abstract) are necessary. This trade-off of memory for computation may facilitate advances in surrogate modelling or Monte Carlo flood risk assessment. [ABSTRACT FROM AUTHOR]

A water availability modelling system implemented in the state of Texas in the United States consists of the generalized Water Rights Analysis Package, which can be applied to river/reservoir systems throughout the world, and datasets for all the river basins of Texas. A monthly version of the modelling system has contributed greatly to improving water allocation and statewide and regional water planning. A recently developed daily version adds capabilities for simulating flood control operations and environmental flow requirements. The simulation study reported here employed the daily modelling system to explore the interactions between the multiple-purposes served by a 12-reservoir system owned by the U.S. Army Corps of Engineers and Brazos River Authority. Interactions between this reservoir system and numerous other water users and reservoirs in the Brazos River Basin are also reflected in the model. The investigation focuses on relationships between water supply, hydropower, flood control, and environmental flow needs. [ABSTRACT FROM AUTHOR]