River Hydraulics

Green infrastructure stormwater control measures, such as permeable pavement systems, are common practices used for controlling stormwater runoff in a developed country. This paper focus on the permeable pavement as a measure of stormwater mitigation in urban area. A hydraulic design aspect of reservoir stone layer is offered along with solution for the study area. Hydraulic design of the stone reservoir storage area includes depth of reservoir layer, drawdown time and storage volume. The depth of stone reservoir is calculated using the minimum depth approach for a permeable pavement of a given specific region. Rajendra Nagar Patna as study area is considered for design calculation. The depth of reservoir layer is 471 mm corresponding to last three years average annual precipitation of 120 mm. This will store water 7963 m3 with draw down time of 57 h. Soil beneath reservoir layer having low-infiltration rate, hence required additional measure like drain pipe. In addition, proper maintenance is needed to keep pores of the pavement surface remain open. According to researchers, cost of the permeable pavement is 15–80% less than the other stormwater management measures. Increasing the amount of stormwater in-filtered can result in lower stream flow levels after storm events. Permeable pavement can be used to substantially reduce the volume of stormwater runoff.

Flow measurement in rectangular channels can easily be carried out using measuring flumes. The type of flume used in a particular application depends on the need for precision and cost. Traditional flumes such as cutthroat flumes are usually built with the channel itself by channel side convergence. Their construction or removal involves engineering work on the channel. The authors feel this as the limitation of the traditional flumes; as for similar sections of the network of channels, a new and independent construction of flume is required. The present study negates this drawback and proposes a particular kind of flume for flow measurement in rectangular irrigation channels in which the throat section of the flume is obtained with a cone shaped object, placed at the center of the rectangular channel. The limitation of a fixed structure can be overcome by using a mobile structure that works on the same principle and remains effective in similar situations. The present study involves the use of a cone shaped obstruction to restrict the flow in order to achieve critical condition. An analytical model is developed for discharge measurement in rectangular channels using the conical obstruction. The geometry of the channel at the location of the obstruction becomes complex due to the presence of cone shaped object. The study presents various comprehensive equations defining the flume geometry. The cone shaped obstruction is equipped with a gauge at its upstream side to measure the depth of flow upstream of the critical flow section. The reading of the gauge is directly related to the flow rate. The relation between upstream flow depth and rate of flow is obtained analytically using energy concept. An experiment is performed in the laboratory by observing flow depth after placing a cone in the rectangular channel under free flow condition. The experiment results validated the developed analytical model. The maximum error of the flow discharge obtained using the analytical approach was found to be 5.19 percent when compared with the actual flow rate. The proposed flume is appropriate for temporary use and can replace the traditional flumes for flow measurement in small conduits. The flume is a simple and affordable device for flow measurement which is easy to construct, carry, and mount. The cone is physically independent of the channel and can be used in different, similar sections of the network of channels. The unit can be quickly fixed and detached for momentary use in open channels. This flume can be used as a mobile device for momentary flow measurement in open channels under free flow condition.

A comparative analysis of the experimental and numerical results on flow fields around submerged tandem and aligned cylinders is presented. The flow characteristics were measured using Acoustic Doppler Velocimeter (ADV), and the cylinders were aligned 0 and 20° over horizontal plane rigid beds. The results are validated using steady numerical simulation using COMSOL 5.3. Experiments were conducted with two unsymmetrical cylinders of upstream cylinder diameter 3 cm and downstream cylinder diameter 7.5 cm, separated by 2.5 times the spacing i.e., 18.75 cm, under completely submerged conditions. A submergence ratio (depth of water to height of cylinder) of 1.4 was taken. A fully developed flow condition with an average flow velocity of 0.1165 m/s was ensured for both the arrangement. For numerical simulation, all the parameters and boundary conditions remain the same as experimental. The computational domain was limited around the cylinder to reduce the computational time. The horizontal distributions of time averaged three dimensional velocities at various radial loci on different horizontal planes have been plotted. Streamlines are plotted to study the flow features. The results collectively delineate the changes in the characteristics of the flow field at the wake of the upstream cylinder brought to effect by the presence of a larger downstream cylinder. A weak sheltering effect by the upstream cylinder on the downstream cylinder for 20o angular alignment especially differentiates its flow field characteristics from that of the linear tandem arrangement of the cylinders at 0°.

As boundary shear stress is an important parameter in open channel flow so experiments are carried out in non-prismatic compound channel. These experimental channels comprising of rectangular main channel, two symmetrically disposed diverging flood plains. The boundary shear stress distribution cannot be determined easily as they depend upon the velocity field, the shape of the cross section, and the boundary roughness. Variation of shear on flood plain and main channel with respect to the relative flow depth and divergence angle has been demonstrated. The present experimental non-prismatic compound channel is having diverging flood plain. Here, experimentations were done with two water depth ratio (Dr) such as 0.4 and 0.5 and two diverging angle such as 5.93 and 9.83°. As a complementary study of the experimental research undertaken in this work, one numerical hydrodynamic tools, viz., three-dimensional CFD model (ANSYS—FLUENT) is applied to simulate the flow in non-prismatic compound channel. This study aims to validate ANSYS—FLUENT simulations of open channel flow by comparing the data observed in the hydraulics laboratory of the National Institute of Technology, Rourkela. In this study, I have used four turbulence models to validate the result up to the at most accuracy. The four models are as follows: LES, k-ɛ, k-ω, and SST. The experimental results were taken as the reference, and all the models simulation result of boundary shear stress is compared with it, among the four models LES was given the approximate result and was taken as the best model for the analysis of boundary shear stress for non-prismatic compound channel.

An experimental approach was performed to examine the interaction between the rigid boundary and grid turbulence of different mesh sizes. Three unlike mesh sizes (M1, M2 and M3) were used having a constant diameter (d) and cross-section. Variation of mean velocities in stream-wise and vertical direction, turbulent intensities, Reynolds shear stresses and turbulence kinetic energy at the different locations of the grid M1, M2 and M3 are discussed. The time series of velocity was measured by an acoustic Doppler velocimetry (ADV). The measured data of velocity fluctuations were used to understand the variations of turbulent characteristics behind the grids with rigid boundary interaction.

A meander is a bend in a sinuous watercourse or river. It consists of a series of turns with curvatures in alternate directions which are connected at the points of inflection or by short straight crossings (Dey). Scientists and researchers are studying the hydrodynamics, morphology, bed topography, etc. of meandering rivers for a very long time. The details of secondary flow become an integral part for some researchers while studying meandering rivers. The role of the centre region cell and the presence of the outer bank cell have also been investigated by many researchers and experts. The centre region cell or helical motion occurs due to unequal forces between centrifugal force and pressure force with flow near the surface directed towards the outer bank and that near the bed directed towards the inner bank. Many of them also tried to find the relation between outer bank circulation cell and bank shear stresses and how it affects bank erosion. Researchers and experts have worked to find out various parameters like mean flow, Reynolds shear stress, turbulent kinetic energy (TKE), etc. and their interactions in meander bends. A lot of field and laboratory experiments have been carried out with different conditions to understand the behaviour of meandering rivers.

A side rectangular weir is used as a flow diversion structure, having spatially varied flow with decreasing discharge. They have various applications in the field of river, hydraulic, environmental and irrigation engineering. In this study, group method of data handling (GMDH) with two types of transfer function, namely quadratic polynomial one variable and quadratic polynomial two variable, were used to estimate the coefficient of discharge for sharp-crested side rectangular weir. On the basis of the F-test, it is found that the upstream Froude number is the most influencing parameter for the estimation of the coefficient of discharge. On the basis of dimensional analysis, it is observed that the coefficient of discharge depends on the ratio of the crest height to the length (P/L), ratio of breadth of the main channel to length (B/L), approach flow Froude number (F1) and ratio of the upstream depth to length (y1/L) of sharp-crested side rectangular weir. The coefficient of correlation (R = 0.93), average absolute deviation (AAD = 2.99) and mean absolute percentage error (MAPE = 3.078) show better performance of the present GMDH model. Finally, the results indicated that the GMDH model could provide more accurate predictions than those obtained by traditional regression models.

One of the most critical factors in the design of a hydraulic system is the energy dissipation arrangement for high-velocity flow in an ogee spillway. The release of excess water from crest to toe of the ogee spillway generates a large amount of kinetic energy. This would result in scour and erosion on the spillway's downstream face. Many different forms of energy dissipators have been used for ogee spillways in the past. However, they have energy dissipation, scouring, and erosion issues. The aim of this study is to create a physical working model of an ogee stepped spillway with a combination of solid roller bucket and type II stilling basin as an energy dissipator for the Khadakwasla dam in Pune (India). Two sets of phase models for a design discharge of 2700 m3/s were used in laboratory experiments. The non-dimensional parameter (yc/h 0.8), nappe flow, and Froude number must be held within acceptable limits with 12 and 9 steps, respectively. The model results show that the 9-step model (Set 2) achieved 80.24% energy dissipation for a 4 m head with a controlled value of non-dimensional parameter up to 0.69, which is the highest energy dissipation among all sets of subject models. As a result of the current model analysis, it was discovered that the combination of a solid roller bucket and a type II stilling basin is the best energy dissipator for an ogee stepped spillway.

A sharp-crested side compound weir is a flow diversion structure provided in one or both sidewalls of a channel to spill/divert water from the main channel. It is widely used in irrigation, hydraulic and environmental engineering. The mechanism of flow through the compound side weir is complicated, and it is difficult to establish a model to accurately predict the coefficient of discharge. In this study, the group method of data handling network with quadratic polynomial, ratio and linear two-variable functions was used to predict the coefficient of discharge for side compound sharp-crested weir. The discharge coefficient of compound side weir has a high correlation with three dimensionless parameters including upstream Froude number (F1), ratio of weighted crest height of side weir to crest length of side weir ( $$P$$ P /L) and the ratio of upstream flow depth to crest length of side weir (y1/L). Therefore, a new model for the determination of coefficient of discharge of side rectangular sharp-crested compound weir was developed. Results of the GMDH model were also compared with the available regression model, and it was found that GMDH results were better than that of the regression model. The performance of the present model is based on the coefficient of correlation (R = 0.8489), mean absolute percentage error (MAPE = 17.62) and average root means square error (RMSE = 16.10). On the basis of sensitivity analysis, it was found that ( $$P$$ P /L) was the most effective parameter for the prediction of coefficient of discharge.

During flood, the flow distribution in main channel and floodplain is always an important factor for river engineer to model, accordingly, the measures can be taken in the floodplain area. Experiments on diverging compound channel show that the flow distribution in main channel and floodplains are found to be a function of four non-dimensional geometric and hydraulic parameters such as width ratio, relative flow depth, relative longitudinal distance and flow aspect ratio. This paper presents an empirical-non-linear-multivariable regression model by considering the aforementioned parameters to compute discharge distribution in diverging compound channels. The model is developed using discharge distribution data obtained from present laboratory experiments and with the published data of other researchers on diverging compound channels. The predictive strength of the developed regression model is validated using several major statistics. All deployed statistics have indicated that the developed model is highly significant. The outcome for all diverging compound channels resulted in minimum RMSE and MAPE values as 0.0092 and 4.35%, respectively, when the discharge is predicted using the developed multivariable regression model.

Compound channels are basically described as two stage open channels having main river and its adjoining floodplains. The momentum transfer phenomenon at the junction of main channel and floodplain is very crucial to be understood to estimate the discharge. The difference in water depth and roughness between the two zones generally causes momentum exchange at the interface. It is simple to quantify this momentum exchange for uniform flow conditions in river; however, for non-uniform flow condition the quantification is complex as the flow properties change in both longitudinal and lateral directions. Therefore, a study has been done on overbank flow with non-uniform flow condition, and stage discharge relationships are analyzed for accurate modeling. As natural rivers may have different configurations, so two different types of channels that are converging and diverging channels are considered and flow variables at different longitudinal positions are analyzed. Two discharge predicting models are developed which can be used for flow in natural rivers. These models depend on the non-dimensional forms of geometric and flow parameters and the percentage of the boundary shear forces carried by the adjacent floodplains. So it is required to analyze and estimate the boundary shear force distribution carried by main channel and non-prismatic floodplains before predicting flow. So, two different equations are proposed for percentage shear carried by converging and diverging floodplains. In addition, the developed models give simple ways for the quantification of percentage boundary shear force and provide accurate discharge result through non-prismatic channels. The predictions of the models are then compared with the models of other researchers. The prediction efficiency of the present model is found better than the models of previous researchers.

The majority of open channel flows of interest to hydraulic engineers and hydrologists are unsteady. In unsteady flow cases, some aspects of flow (velocity, depth, viscosity, pressure, etc.) will be evolving in time. However, more numbers of issues identified with the unsteady flow have been roughly accepting as steady flow (for example, constant peak discharges in floodplains). Very few experimental investigations have been conveyed in previous literature to examine turbulence qualities in an open channel flow under unsteady flow states over rough beds. The present study investigates the vertical and horizontal fluctuating velocity profiles under unsteady flow states in a rectangular open channel. An experiment is conducted to observe the turbulence characteristics under unsteady flow conditions in a rough bed open channel for two different flow depths. One identical hydrograph is passed repeatedly through the rectangular flume with a fixed rough bed. The dense rough mat is used as a rough bed which replica of a dense grass bed. The flow patterns are investigated at both lateral and longitudinal positions over three different cross-sections by using a micro Pitot tube and Acoustic Doppler Velocimeter (ADV). For two given flow depths, the velocities on both the rising and falling limbs are observed and analyzed. Hysteresis effect loop between stage-discharge (h ~ Q) rating curve between the rising and falling limbs is illustrated. Turbulence characteristics, i. e., variations of lateral and vertical Reynolds stresses, are analyzed from measured fluctuation velocities.

In this paper, an attempt has been made to carry out the study of scour depth at one of the piers of the Gandhi Setu in Ganga River near Gaye Ghat, Patna. Different parameters of the different empirical equations have been calculated by collecting soil samples from the site and analyzed in the laboratory. Based on these parameters, the scour depth is calculated by using different empirical equations given by different researchers such as Shen et al., the Modified Laursen, Jain and Fischer and Lacey’s. The actual scour was also measured near one of the piers of Gandhi Setu in Ganga River at Patna, in-situ measurement using the rope attached with heavy weight. It was found that the scour depth measured manually matches satisfactorily with the scour depth computed using Lacey’s empirical formula.

Optimisation of hydraulic design of spillway involves verification of designs of various components of spillway which includes crest profile of spillway and bottom profile of breast wall, adequacy of spillway spans to pass the design flood, the sufficiency of divide walls and training walls, location of trunnion of gates, assessing the performance of energy dissipator, assessing the scour downstream of ski-jump bucket, design of pre-formed plunge pool, location of head regulator/power intake structure and upstream and downstream protection subjected to design floodwaters. Hydraulic model studies play a key role in optimising the designs of various components of the spillway as mentioned above. Hydraulic design of spillway of Uri-II dam was optimised in CWPRS, Pune, by conducting hydraulic model studies. Uri-II H.E.Project was envisaged as a run-of-the-river scheme on the River Jhelum in Uri Tehsil of Baramulla District of Jammu and Kashmir. It has a power generation capacity of 240 MW (4 units of 60 MW each) utilising a gross head of about 130 m. The project consists of a 52 m high and 173 m long concrete gravity dam with a 4.27 km long headrace tunnel (8.4 m diameter), a restricted orifice-type surge shaft (25 m diameter), two 5 m diameter steel-lined penstocks, four 3.5 m diameter bifurcated steel-lined penstocks, an underground powerhouse and a horseshoe shaped tailrace tunnel 3.77 km in length. The spillway is designed to pass design outflow flood of 4850 m3/s at FRL El. 1241 m and also to flush the sediment deposited in the reservoir into the river downstream. A breast wall spillway has been proposed with four low-level orifices of size 9 m wide × 11.4 m high (originally 12 m high) with crest level at El. 1217 m. The ski-jump bucket is provided for energy dissipation with invert at El. 1210.19 m and lip at El. 1213 m. The project was completed and all four units were commissioned and the 4th unit in July 2014. Hydraulic model studies enabled optimisation of various components of spillway by optimising the size of spillway spans and design of natural plunge pool and suggesting downstream hill slopes protection. Optimised hydraulic design was made by assessing the discharging capacity of the spillway, validating crest profile with pressures on the spillway surface, the performance of energy dissipation arrangement for the entire range of discharges, flow conditions in the reservoir upstream of the spillway and head regulator, flow conditions downstream of the spillway and head regulator and requirement of a natural plunge pool with expected scour levels. This paper provides detailed information on the hydraulic model studies carried out on the spillway and energy dissipator of Uri-II dam spillway, Jammu and Kashmir.

Spillways are provided to dispose off excess flood safely to downstream without causing excessive erosion. To dissipate the energy of flood, energy dissipators are provided for spillways. Ski jump buckets are one of the popular types of energy dissipators provided for spillways when the available tail water depths are very low, so that the clear ski jump forms and throws the flood away from the toe of the spillway, preventing the undermining of the spillway. However, depending upon the site conditions, ski jump buckets are provided where tail water levels are even at higher levels. In such typical conditions, submerged ski jump action occurs and the efficiency of energy dissipation arrangement may get reduced. As such, the performance of these designs is to be verified by conducting hydraulic model studies, since there are no exact codal provisions existing to have a flawless design. The optimization of ski jump bucket subjected to higher tail water levels can be done by studying its performance for various discharge conditions and making necessary modifications for getting clear ski jump action, without having hydraulic jump formation or submerged ski action in the bucket region which reduces energy dissipation and undermines spillway foundation. The submerged action of ski jump would also have an effect on the scour development downstream of the spillway and in the design of pre-formed plunge pool. A case study is presented in this paper where ski jump bucket of the spillway of Punatsangchhu-II H.E.Project, Bhutan, was optimized for coping up with prevailing higher tail water levels, by hydraulic model studies conducted on 1:70 scale geometrically similar physical hydraulic model in CWPRS, Pune.

The study of flow in the vegetative channel is not new to existing concerns. The effect of vegetation in river systems with regards to its preservation is of much importance. The aquatic plants that thrive in water have been found to control the mean flow and turbulence of flow of river systems. Even the morphology of a channel can be affected by the submerged and emergent vegetation. The important parameter of any channel mainly velocity profile is influenced a lot due to the height and flexibility of submerged aquatic plants. This also impacts the transport of sediment in the channel. Apparently, the presence of plant life in a channel decreases the mean discharge and sediment load potential and leads to the accumulation of sediment in the channel due to additional drag produced by the presence of vegetation. Literature status reveals that the scope in this field is vast as not much has been contributed so far. Also, the studies mostly reveal the use of conventional methods to indicate the relationship between the different parameters. To develop models for relating the parameters and to predict future scope, soft computational techniques are used to simplify the otherwise complex equations. Studies indicate the use of neural networks in association with PSO techniques, also GA has been reported. This study has been conducted with the help of another soft-computing technique which analyses polynomial neural networks, Group Method of Data Handling (GMDH). This technique has been reported to be in extensive use in the field of hydraulics. This approach, as an advanced tool, has been modelled to predict the resistance due to flow–vegetation interaction in a submerged vegetated channel. The main aim of this approach is the development of an explicit model which optimises the parameters and predicts the unknown input–output mapping. The results generated by the model have been found to be sufficiently good. The model has been developed in the interest of predicting future outputs by capturing the related relationship of input–output mapping. It is designed so as to analyse the influence of various parameters on the velocity profile.

Detailed experimental investigations are reported in this paper to study the turbulent flow characteristics in wave-current flow over the bed-mounted ribs at equal spacing. Regular wave is generated by wave-maker at frequency f = 1 and 2 Hz which is installed at the entrance of the wave flume. The measurements were performed at the developed zone between the two consecutive ribs. The results show that mean stream-wise velocity changes significantly with the induced wave over turbulent current. Further, it is observed that the recirculation length changes slightly with a superposition of wave over current.

The lateral movement of the river channel within its Khadir over time is a universal phenomenon. Various processes of the fluvial-geomorphological environment, such as frequent occurrence of floods, deposition of sediment, the capture of lower courses of tributaries by the main channel, failure of the bank and avulsion, are predominant factors behind the channel dynamics. In this study, shifting of main course, bank-lines and the variation of the sinuosity index were computed from the year 1973–2018 within the reach Bhagalpur to Kahalgaon, in the state of Bihar, India. The area near both the banks is densely populated and has many important structures. Shifting of river banks put these structures under risk of failure and dwelling area under risk of submergence in flood seasons. It has abandoned its original course and huge sandbars have been formed in the middle of the stream. These sandbars are hindering vessel navigation too. The dynamics of channel adjustment in terms of lateral shifting can be beautifully illustrated by the application of modern geoinformatics tools, i.e., remote sensing and Geographic Information System (GIS). From the study of USGS satellite images using ARC-GIS, it has been found that the main course and bank-line has been shifted significantly during this period. The study of the width of the active channel and the position of main course indicates that both the left and right banks have changed significantly due to the erosion and deposition of sediment during monsoon period of each year. During the period 1973–2018, the river has moved toward its left bank and has become more sinuous in nature. This study highlights a significant message of immense vulnerability of the Ganga river and also points towards its geomorphological instabilities in this reach of the river.

The precise prediction of the depth-averaged velocities, lateral shear stresses, and boundary shear stresses are necessary to access the flow capacity and flow variations related to flood events in meandering channels. The accurate assessment of the distribution of velocities, conveyance, and bed shear stress distribution is significant for flood management schemes, bank protection studies, and sediment dynamics on meandering channels. This work proposes a new approach for assessing the depth-averaged velocities laterally across a meandering compound channel. The experimental evaluation was done in Hydraulic Laboratory in the National Institute of Technology Rourkela (NITR), Odisha, India. The apex section was considered for estimating the boundary shear stress through experimentation. The meander cross-section is split into five distinctive panels for studying the flow phenomenon for overbank flow. The results indicated that the boundary shear stress causes a notable change in the secondary flow coefficient (K). The new model provides the variation of depth-averaged velocity ( $${U}_{d})$$ U d ) across the cross-section of the meandering compound channel, which includes the bed-generated friction, secondary flows, and lateral shear turbulence.

A trapezoidal labyrinth weir is characterized by a broken axis in the plan to increase the crest’s effective length. Labyrinth weirs provide an increase in crest length for a given channel width, thereby increasing flow capacity for a given upstream head. A physical or experimental study based on the design and analysis of trapezoidal labyrinth weirs is presented in this study. Hydraulic model tests of the weir showed that the behavior of the labyrinth weir was convenient and that the discharge capacity presented a good agreement with theoretical calculations. It is the purpose of this paper to present a satisfactory developed physical model of labyrinth weir flow and provide engineers with a model capable of dealing with a variety of labyrinth weir configurations and flow conditions. The preliminary hydraulic calculations results indicated that hydraulic jump with estimated low Froude numbers (Fr1), of about 2.7–3.0, is supercritical at its downstream, and it enhances with the slope of the weir. This study of labyrinth weir is performed between head to crest ratio, apex width, vertical aspect ratio, approach, and conveyance channel conditions that increased the discharge capacity of labyrinth weir and design of trapezoidal labyrinth weir.

Vegetation is a crucial element of the river system. In open channel hydraulics, vegetation has a significant effect on flow structure; it offers resistance to the flow and responsible for flood level increase by reducing the carrying capacity of the flood. Researchers throughout the globe have analyzed the resistance provided by vegetation with a theoretical and experimental study. Many flow and channel parameters affect the flow resistance. Out of all these parameters, vegetation is an influential one in vegetative channels. It alters the velocity profiles in an open channel, which affects the roughness coefficients. The roughness coefficients in vegetative channels vary with the flow depths and sections. Therefore, due to the complex structure, it is tedious to come up with a flow model based on previous research. Though it is challenging to determine directly from a field exercise, a laboratory study has been carried out in emergent vegetation at Hydraulics Engineering Laboratory, NITR, to explore the vegetation influence. The Shiono Knight Method (SKM) has been applied to calculate the boundary shear stress and depth-averaged velocity distribution in an open channel flow. For this purpose, three calibrating coefficients, namely bed friction (f), dimensionless eddy viscosity (λ), and transverse gradient for secondary flow (Γ), have been incorporated to modify the existing SKM. A mathematical model was formulated to find the calibrating coefficients in the channel and compared with the SKM.

In this research, long term daily variation in daily water flow and sediment flow of Lower Godavari Basin is focused. The records of water discharge as well as suspended sediment concentration are collected from six hydrological stations located on Lower Godavari Basin for different time periods of 1969–2015. For analysis, the daily mean values of water discharge Q (m3/sec) and suspended sediment transport rate Qs (t/day) are used. The daily mean water discharge and sediment discharge series were analysed for auto correlations prior to apply trend test. The nature of trend is analysed by using Mann–Kendall test, Sen’s slope estimator test at the significance level of 5%. The test results revealed that out six stations five stations reported decreasing trend in water discharge and two stations (Jagdalpur and Nowrangpur) show significant decreasing trend and remaining one station (Konta) shows increasing trend. Similarly, for sediment discharge, results indicate that all the six stations that reported decreasing trend with three stations (Nowrangpur, Perur and Polavaram) show significant decreasing trend. The abrupt change analysis is carried out at 5% significance level for water discharge and sediment discharge time series. The significant abrupt change occurs from year 1995 for Jagdalpur and Nowrangpur station. Significant decline in sediment discharge is observed for station Jagdalpur, Nowrangpur and Polavaram in year 1994, 1994, 1995, respectively. The significant increasing or decreasing trend is indication of increased human activities and Climatological variations in the catchment area of Lower Godavari Basin.

In current study, flow turbulence statistics generated around a circular bridge pier placed in a rigid bed channel for different flow discharges under constant flow depth are presented. Experimental work in the laboratory flume included measurement of velocity distribution around bridge pier using three-dimensional Micro-Acoustic Doppler Velocimeter to estimate the bottom Reynolds shear stresses, Velocity spectra, and Turbulence Kinetic Energy near the bed and mid flow depth. Power spectra analysis depicted that dominant of Reynolds shear stress, in the present study, is $$uv$$ uv plane than other two planes at flume centerline. The strength of wake vortex is doubled for 27L/s vis-a-vis 22L/s.

Excessive scouring around the bridge pier is a threat to the stability of the bridge. It is vital for human life and bridge safety that some countermeasures against scouring need to be developed. This paper encompasses an experimental investigation on the collar and combination of the slot with a circular and square collar for reducing scour depth around the circular bridge piers. An experimental study was carried out for six different collar and slot arrangements by varying Froude number values under laminar flow conditions. The present study concluded that with the increase in the Froude number depth of scouring increases, increasing the size of the collar plate depth of scouring decreases. The combination of the circular collar and slot gives the minimum scour depth among all the arrangements.

Scour around bridge piers is one of the main reasons for bridge failures. Previous researchers reported that pier shape is an important parameter since it affects the flow field and then scour formation. This study aims (i) to find the effect of pier shape on local scour in comparison with the circular pier shape and (ii) interference effect of different shaped piers placed in tandem arrangement on local scour. Experiments are conducted in a rectangular glass-walled flume with sand of d50 = 0.56 mm, under clear-water, and steady flow conditions. Two modified piers are prepared (P2 and P3) with the area equivalent to the area of the circular pier (P1). P1 is a circular pier with diameter D (=5 cm), P2 is a combination of semi-circle and triangle in which pier is oriented to flow direction in either ways (P2a and P2b), and P3 has a groove with projection on semi-circular face of P2. The results showed that compared to P1 the scour depth reduced by 23.5%, 50%, and 55% for P2a, P2b, and P3, respectively, thereby reducing the need for scour countermeasures. From the results of tandem arrangements, it is observed that P1 as front pier and P2a as a rear pier with a clear spacing of 1.0D and P3 as front pier and P1 as a rear pier with the clear spacing of 1.75D given less scour. These observations can be helpful to construct a new bridge adjacent to an existing bridge.

Open channels have a wide range of applications directly or indirectly in our day-to-day life. Irrigation canals, waste water channels, sewers etc. are some of the practical examples of free-surface flow channels. Study of the hydraulic properties of open channel is a prime part of river engineering. This article presented a novel approach to model the two energy correction coefficients (kinetic energy and momentum coefficients) by collecting experimental data sets on rough asymmetric channels. In the present work, two sets of experiments were conducted on a compound asymmetric channel having two types of roughness material on the flood plain (plastic mat and gravel). To develop the models a wide range of data sets has been considered which includes asymmetrical compound channels with smooth or differential roughness cases. For the current work, multivariate regression analysis was used to develop ameliorated models to anticipate error-free values of the energy correction factors. Multivariate regression analysis is used to predict dependent variables from a number of independent variables. In this present study, for implementing multivariate regression analysis, the two correction factors (Energy correction factor α and momentum correction factor β) were chosen as dependent variable and aspect ratio (δ = b/h), roughness ratio (γ = nfp/nmc), Reynolds No. (Re) and Froude’s No. (Fr), width ratio (α1 = B/b), relative depth (Dr = (H − h)/H) are taken as independent variable. Error analysis was performed to determine the accuracy of the present models.

In present study, hydraulic geometry equations are developed for middle Tapi river, India to assess the variation in hydraulic parameters at Bhusawal, Padalse, Sukhwad, Gidhade, and Sarangkheda stream gauging stations on decadal basis while considering the mean annual discharges of respective periods for the analyses. The insignificant variations in water surface width with the discharge has indicated box shaped cross-section at Sarangkheda stream gauging station. On other hand, large variations in water surface width with the discharge at Padalse station indicated dish shaped cross section at the same stream gauging station. The nature of hydraulic geometric equations has indicated higher stream powers (higher m/f values) at upstream gauging stations, i.e., Bhusawal and Padalse, vis-à-vis downstream gauging stations, i.e., Sukhwad, Gidhade and Sarangkheda stream gauging stations. Present study would be useful in planning appropriate river training structure and design of efficient hydraulic structures in the respective river.

Etalin Hydroelectric Project (3097 MW) is a run-of-the-river scheme upstream of 3000 MW Dibang Multipurpose Project, utilizing the waters of Dri and Tangon rivers in Dibang Valley of Arunachal Pradesh. Dri limb diversion structure consists of a 101.5 m high and 213.7 m long concrete gravity diversion dam. An orifice spillway has been provided to pass a design flood (PMF) of 11,811 m3/s along with Glacial Lake Outburst Flood (GLOF) of 1,170 m3/s. A ski-jump bucket is provided for energy dissipation. Hydraulic model studies were conducted at CWPRS, Pune, to determine the efficacy of orifice spillway and energy dissipator for various ranges of discharges and reservoir water levels. The original design of the orifice spillway was found to be suitable in terms of discharging capacity of the spillway and performance of the energy dissipator. However, pressures on the spillway were not found acceptable while passing the low discharges for the gated operation of the spillway. The fluctuating upper nappe was intermittently hitting the trunnion of the radial gate for the design flood. Flow conditions in the bucket were violent due to strong swaying rooster tails generated at the end of piers for higher discharges. Based on the findings from the model studies, the design was modified by raising the crest by 5 m and extending the pier length up to the lip of the bucket to improve the overall performance of the orifice spillway. Modified design helped in finalizing the trunnion elevation of the gate, improving the pressures on the spillway surface and flow conditions in a ski-jump bucket. A need for providing a pre-formed plunge pool was also identified by analyzing the scour profiles. The location and size of the plunge pool were suggested based on the extent of scour observed downstream of the ski-jump bucket. Hydraulic model studies played a very important role in assessing and optimizing the hydraulic performance of spillway and energy dissipator of Dri dam spillway.

From the past, management of municipal solid waste has been a serious environmental issue of concern. Unhealthy waste disposal practises pave a way for air, water, soil and land pollution. Scientific landfills are a great solution for this. Scientific landfills are engineered means of confining waste to a small area and covering it with daily layers of earth and compacting it to reduce its volume. Our paper focuses on an unscientific dumpsite located in the outskirts of Guwahati, Boragaon, that proposes the calculation of area for different heights for the same site in a scientific manner. The calculation is done for a period of 20 years (2019–2038) by finding out the future expected population, per capita waste generated and the total municipal solid waste (MSW) generated for the entire city. The term municipal solid waste for the study area refers to the waste which is obtained from domestic, commercial establishments, hotels, restaurants, parks etc. As per our calculation, the total area available for the landfill site is 88,315.26 $${\mathrm{m}}^{2}$$ m 2 and as per the guidelines, in India only 30% of the MSW is recycled and the remaining 70% is deposited in the landfill site, which is being followed in our design. In the design adopted, with the values of density, the loose mass and daily compacted volume is calculated. This is then followed by the calculation of the annually compacted volume. The work includes after the deposition of the daily waste, a layer of soil is provided as a cover so as to prevent the odour problems that occur in the landfill. In the method adopted, volume of cover material is taken to be equivalent to 20% of the volume of recently compacted waste. By adding on the values of annually compacted volume and cover material, volume of sanitary landfill is obtained. The total area required is calculated by assuming factor of increase in the additional area required for the access roads, border setback areas, control buildings, sanitary facilities and manoeuvring yards. The factor of increase in the additional area is taken as 25% of the total area to be filled in this case study. The scientific landfill in Boragaon for the 20 years is divided into 4 plots in which each plot is filled within a span of 5 years. The study shows that the proposed area will be filled within the span of first five years and this area is very less as compared to the area for the waste to be accommodated by the year 2038.

Dam break analysis provides important input on infrastructure development in any area. Surat city having a population of about 50 lakhs is situated in the lower Tapi basin. Further, important industries such as ONGC, Reliance and Kakrapar Atomic Power Station are situated in the said basin. The effect of the Ukai dam break flow in the lower Tapi basin along with Surat city has been carried out in the present study. The inflow hydrograph coming into the said reservoir has been considered as the upstream boundary, while tidal level at the Arabian Sea has taken downstream boundary conditions to carry out the dam break analysis. Total 190 cross sections are used to model 128 km long Lower Tapi River in the 1D hydrodynamic model (MIKE 11). The developed model has been calibrated for the flood of the year 1998 and validated for 2003 and 2006. The dam break flood hydrograph having peak discharge 2,57,885.9 m3/s is obtained and stage-discharge relationship at different locations is derived. The stage-discharge curve shows the water level 36.3 m above mean sea level at Surat for aforesaid peak flow. The derived stage-discharge curve, flow velocity, arrival time of flood and its duration were obtained from dam break analysis which can be utilized to prepare flood hazard and risk map of Surat city and the surrounding area.

River bank erosion due to unstable banks and high flow variability is usually controlled using permeable and impermeable structures, which are not studied much yet and also cannot solely provide desired velocity reduction. These structures, along with a combination of porcupine screens followed by geobag (i.e., Hybrid layout), are investigated using CCHE3D model for emerged, transition, and submerged flow conditions with respect to porcupine height. An optimum hybrid layout showed velocity reductions of 35% in submerged and 70% in emerged conditions, which further increased with multiple porcupine screens.

This paper presents the experimental investigations of effect of bend on scour and deposition patterns around causeways. Data have been collected in a re-circulatory open channel flow system on three causeway model slabs for two discharge values, i.e., 2.5 and 7.0 l/s. The causeway model slabs were made of cement concrete with 0.75 m length, 0.2 m width, and 0.20 in overall depth. To critically observe the effects of presence of bend on scour and deposition, three locations of causeway slabs were used. The first one is provided in a straight reach in the test channel, the second one is just after the first bend normal to flow, and the third one was an oblique slab provided between the inner and our curvature of the second bend downstream of the first bend. Data of scour and deposition were recorded after the end of the run. Also photographs were taken. It is concluded that for each discharge, scour and deposition occur in all cases, but at low flow the scour in straight reach is less pronounced. However, scour occur in second and third causeways due to the presence of bends. At still high values of discharges, scour and deposition both are significant in all the causeways. Since first causeway is straight and normal to flow, there is uniform scour and deposition along the edges of the causeways. The scour and successive deposition occur in other two causeways with high magnitudes, but the location of maximum scour depth shifted. Photographs also support the findings in this investigation.

Patna has been facing acute drainage problems due to its topography. In the recent past, Patna was heavily flooded and there was severe waterlogging in the years 1990 and 1997 in the town. Small boats could be seen on the roads. Urbanization, inadequate and choked drainage system adds to the severity of the problem. Efficient drainage and pumping are the only means to dispose of the rainwater of the town. The study presented in the paper simulates stormwater runoff through the drainage networks of Patna town using the hydrodynamic storm water management model (SWMM). The input to the model was extracted from different maps prepared in GIS environment. The digital elevation model (DEM) prepared for the study area was divided into 50 sub-catchments depending on the topography, existing drainage network and the land use pattern of Patna. Satellite data was used for land use classification of Patna. Annual daily maximum rainfall data from 1975 to 2007 were used for the analysis of design storm of Patna town. Extreme value (EVI) distribution was used to find the design storm for 2 to 100 years return periods. The simulation results were calibrated with the observed hydrograph at different outlets of the drains. After calibration, the model was simulated with the existing geometry of the drainage network without any blockage which yielded inadequacy of drainage system to dispose of the runoff even for 2-year return period storm and caused flooding and waterlogging. The dimension of the drains was modified mainly with respect to depth without disturbing the existing network and the model was simulated for return periods from 2 to 25 years as well as for the severe storm observed from 1975 to 2007 till no spilling of the drains were observed.

In this present work, a hydraulic study was done on the expansion section of the Kaskaskia river, Illinois (USA) (Nani G. Bhowmik). The set of flow variables was collected from the Kaskaskia river, on Reach-1. Investigation on loss coefficient was done on the two expansion sections of Kaskaskia river (1-2 and 13-15) with the diverging angle of 0.50° and 0.17°, respectively. This study was done to understand the effects of the flood on non-prismatic diverging channels. The ANSYS-FLUENT software was used for four different turbulence models, like k-є, k-ω, LES (large eddy simulation) and RANS (Reynolds-averaged Navier–Stokes equation) on the expansion section of Kaskaskia river. Among all the models, LES gave the best result. The predicted velocity was found nearly equal to the observed velocity.

Tapi, the second-largest westward draining river in India, originates at Multai reserve forest in Betul District, Madhya Pradesh, at 752 m. It runs westward for 724 km until discharging into the Arabian Sea via the Gulf of Khambhat. The basin is located between latitudes 20° 5' and 22° 3' north, and longitudes 72° 38' and 78° 17' east. The study aims to better understand the hydrodynamics of the tidally impacted river Tapi and estimate river discharge owing to rainfall at the ONGC bridge in Surat, which is about 14 km from the Arabian Sea. In order to achieve the goals, a two-dimensional hydrodynamic model was created using the Delft3D modelling scheme. The numerical model’s offshore ocean boundary is forced with tidal constituents, while the upstream river boundary is forced with discharge estimated using HEC-HMS (hydrological modelling software). The model estimated tide-induced currents are validated using observed field datasets, and it shows a good correlation. The model results indicated the tidally varying hydrodynamic behaviour during the year’s pre and post-monsoon seasons.

This paper presents an experimental study in which a series of measurements were carried out to investigate the hydraulic characteristics of a wide compound open channel having high width ratio and dissimilar roughness in the main channel and flood plain boundary by using pitot tube point-wise velocity measurements. Furthermore, in order to understand the effect of differential roughness (the ratio of base Manning’s n value of floodplain surface roughness to that of the main channel) on the distribution of depth-averaged velocity and distribution of flow in the experimental channel, cases with different flow rates were studied. The contour plots of 2D iso-levels were drawn using SURFER software. As the channel is symmetric, half of the width is considered for point velocities. The variation of point velocities is considered along width-wise direction of the channel in order to study the depth-wise velocity profile distributions. The lateral variation of depth-averaged velocities was observed in the compound channel flow for different differential roughness (γ) and the variation of flow rate in main channel is also studied with the increase in differential roughness.

During flood, water from the river inundates the floodplains causing mass destruction of human lives and properties. Thus, it is more essential to evaluate flow in the floodplains. The instant study is performed to understand the flow distribution in main channel and floodplains of a compound channel having symmetrical diverging floodplains due to difference in geometry and flow properties. Numerical experimentation is performed for diverging compound channel of different geometric and hydraulic conditions using ANSYS-fluent to study the effect of geometry and flow parameters on the flow distribution of such channels. Depth averaged velocity data obtained from the numerical experimentation for different sections have been taken to compute the discharge in that section for main channel and floodplain separately. Different numerical method like , LES model, k-model is utilized for the modeling test. Among these three models, LES models provided quite good agreement with the experimental data. Hence, by taking LES model, more different diverging channel configuration has been performed and the respective flow is simulated. Using the results of LES, more data sets are extracted and a model has been developed for the computation of the proportion of rate of flow in both main channel and flood plain for various relative flow depths and for different diverging angles. The applicability of the model is proved with the observational data sets of other researchers and found to provide less error in the subsection discharge computations of a non-prismatic compound channel. The reason for higher accuracy by LES prediction has been discussed and recommended for use in non-uniform open channel flow.

With the development of computation capability and readily available computer programs, flow inundation modelling-based flood hazard mapping is widely practiced. For such analysis, digital elevation models (DEMs) are necessary to define the river topography and terrain variability. Fine resolution DEMs are also used to extract the river cross sections that are subsequently utilized in flow model setup. But the availability of fine resolution DEM is the major constrain, especially in hilly and inaccessible terrains, etc. The satellite-based DEMs like SRTM, ASTER, CARTODEM, etc. are the alternative sources in such cases and have been used in several flow modelling studies. In this paper, dam break analysis of a small dam located in Uttarakhand in Kumaon Lesser Himalayas is reported. The various scenarios of flooding due to dam breach of the concrete face rockfill dam on Dhauliganga, a tributary of Kali river by routing flood waves in the downstream reach to compute flood inundation, time of occurrences, etc. are discussed. The hydraulic model for the river reach of about 30 km is developed in MIKE 11 using surveyed river cross sections and 10 m resolution digital elevation model of the study area generated using CartoDEM provided by NRSC, Hyderabad. Three cases of flooding are simulated: (i) flooding due to PMF in the river causing dam break condition; (ii) flooding due to PMF without dam break; and (iii) sunny day failure condition (dam failure with nominal inflow when the reservoir is full). It is observed that the time of travel of the peak flood from the dam site to the major settlement area at Dharchula, about 20 km downstream location, is 42 min for the critical case of dam failure. The maximum flood level and time of travel of the peak flood at the important locations are estimated. However, no settlement/village areas are under inundation for these conditions. The extent of flood hazards for various cases of flooding is estimated by superimposing the inundation map over Google Earth for a detailed description of inundated areas and affected infrastructures.