Riverbed Research Articles

Free flow over and under cylindrical weir-gates with a flow extender

ABSTRACT The complex field of free flow around a cylindrical weir – gate with and without a flow extender is investigated experimentally. The effects of the gap between the channel bed and the cylinder on the discharge characteristics of the cylindrical weir-gate are studied. It is observed that the ratio of the gate to weir discharge increased non-linearly with the normalized opening height. Four triangular downstream extensions of the cylinder oriented at, θ = 0, 10, 20, and 30 degrees were tested, and the minimum underflow to overflow discharge ratio was observed for θ = 10°. The highest improvement in discharge coefficients was 16% ± 6% for extender orientation angles of θ = 10°. The effects of opening height and extender angle on flow streamlines, pressure distribution, vortex strength, turbulent kinetic energy, and Reynolds stresses were investigated. A region of negative pressure was observed near the weir crest and the peak negative pressure increased with the opening height. The size and orientation of downstream wakes were measured, and it was found that the length of wakes varies from 0.30 to 1.06 times the diameter of the cylinder. The experiments showed that for a constant normalized opening height, the vortex center point formed further downstream as the upstream water head increased.

Sedimentation Analysis of Ujani Dam

Abstract -The sedimentation is an effect of erosion on the catchment area of the reservoir and therefore, lesser the rate of erosion, smaller is the sediment load coming into the reservoir. Deposition of sedimentation in the reservoir moderately reduces the capacity of the reservoir. Both Dead storage capacity & live storage capacity gets affected due to sedimentation. Information about reduction in the storage capacity is important for the planning and operational purposes and the same can be obtained by sediment assessment surveys done at regular intervals. Various factors affect the process of erosion, transport and deposition of sediment in the reservoir. Type of soil, drainage density, vegetation, rainfall intensity and duration, shape of catchment and land use / land cover affect erosion. Sediment transportation totally depends upon slope of the catchment, channel geometry and nature of river bank and bed. Deposition is a function of bed slope of the reservoir, length of reservoir, flow patterns, inflow-outflow rates, grain size distribution, mode of reservoir operation etc Key Words: Ujani Dam, Sedimentation, Remote sensing

Impact Assessment of Flushing Flow from a Dam to Invasive Aquatic Plant Egeria densa in a Gravel-bed River

The implications of artificial water release, flushing flow, on the invasive aquatic plant Egeria densa in a gravel bed river, downstream of a dam, were investigated from the viewpoint of ecological characteristics, biomass change, open-channel hydraulics, and river engineering. To understand seasonal changes associated with Egeria densa, as well as the native species Hydrilla verticillata found within a reach, a series of surveys was conducted. A new method for assessing biomass flux during flushing flows is proposed. Our data indicated that Egeria densa biomass within the surveyed reach was reduced by approximately half following flushing flows conducted every March. Biomass flux was also evaluated using the proposed method. Our results imply that flushing flow supports native Hydrilla verticillata inhabitation within the downstream reach of a dam.

Quantifying microplastic dispersion due to density effects

An experimental study was conducted on how polymer density affects the transport and fate of microplastics in aquatic flows. For the first time, polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polyetheretherketone (PEEK), and polyvinyl chloride (PVC) were chemically stained and tested using solute transport techniques and velocities found among rivers in the natural environment (0.016 – 0.361 m/s). The movement of 3D-polymers with densities ranging from 0.9 – 1.4 g/cm³ was quantified in a laboratory flume scaled to simulate open-channel flows in fluvial systems. Except for PP, in most conditions microplastics exhibited similar transport characteristics to solutes regardless of density and established solute transport models were successfully implemented to predict their transport and fate. Mass recoveries and ADE routing model demonstrated microplastic deposition and resuspension was associated with polymer density below critical velocity thresholds ≤ 0.1 m/s. When density becomes the dominant force at these slower velocities, concentrations of denser than water microplastics will be momentarily or permanently deposited in channel beds and microplastics follow the classical Shields sediment transport methodology. This data is the first to provide microplastic suspension and deposition thresholds based on river velocity and polymer density, making a key contribution to research predicting microplastic fate and organismal exposure.

Apron and macro roughness as scour countermeasures downstream of block ramps

ABSTRACT A block ramp is a grade-control structure commonly used to stabilize the river bed with a high efficiency of energy dissipation. This study investigates the effects of using macro roughness and a downstream apron as scour countermeasures on the maximum scour depth downstream of block ramps in straight rivers. All the experiments have been carried out in a horizontal channel and in clear water conditions (no sediment transport). A wide range of hydraulic conditions including densimetric Froude numbers, water drop heights, and tailwater depths for three different rough ramp slopes (1 V:3 H, 1 V:5 H, and 1 V:7 H) was tested. The results have been compared with the results from a smooth ramp (no roughness), which has been considered as a reference. Results show that both macro roughness on the ramp and downstream aprons work well as scour countermeasures while as a comparison, using macro roughness (big-size stones) on the ramp is more effective than downstream aprons to reduce the scour depth. The other finding of this study shows that increasing the downstream apron decreases the length of the scour hole, consequently decreasing the volume of eroded material.

Sewage/Flood Overflow Monitoring and Alerting System

Flooding is a natural calamity that is becoming increasingly frequent and has a severe impact on people's quality of life. This study highlights the use of IoT and Arduino to develop a flood monitoring system that can track the conditions near a reservoir [1]. The system utilizes compatible sensors such as level, temperature, humidity, and flow, which are accurately measured and displayed on an LCD screen. The data is then transmitted via a Wi-Fi module (ESP8266) to an IoT web application, where it is stored in a private channel. In the event of a flood, the web application alerts the relevant authorities and people [5]. Flood are well-known natural disasters that can cause significant destruction in the surrounding areas when water levels suddenly rise in dams and river beds. The damage caused by floods can have a devastating impact on both the environment and living beings. It is critical to receive emergency alerts regarding water level situations in various conditions in the river bed to minimize the damage caused by floods [9].

Сопоставление эффективности использования современных геодезических методов в изучении последствий бобровой деятельности на малых реках

Multiple increase in the beaver population on the East European Plain has led to the appearance of a large number of beaver dams and ponds on small rivers. At present, the problem of regulating small rivers in this region remains poorly studied due to the above circumstances. This study presents the results of a comparison of modern geodetic methods obtained using an electronic total station, GNSS equipment and UAVs. The small river Morkvashinka, flowing along the northern tip of the Volga Upland, was chosen as the object of the study. The spatial coordinates and altitudes measured by the GNSS receiver generally agree well with the tacheometric survey data. The height difference is 0.5 cm (standard deviation – 0.07). However, the main disadvantage of an electronic total station, which limits its use for surveying linearly elongated objects and small river valleys, is the lack of direct visibility of the objects being photographed from the device due to the highly dissected territory, the tortuosity of the river and dense vegetation. Using orthophoto and digital terrain models obtained from unmanned aerial vehicles, it is not always possible to accurately determine the border of the coastline, as well as the absolute heights of the dam, floodplain, terraces, water edge, channel marks (pond depth) due to dense vegetation. However, the river bed and floodplain, beaver dams and ponds are clearly visible on them.

Distribution of river flow in the river bed

The article investigates the fractional and chemical composition of the river flow in the “Sokhsoy” riverbed and their potential applications. The main factors considered are the fractional and chemical composition of fluids flowing along with water in the channel and their changing proportions in water along the length of the channel. The primary components of the fractional composition of suspended solids in the river are particles with diameters of 1.0 - 0.05 mm and 0.05 - 0.001 mm, which account for an average total share of 22.64% and 5.78% in the entrance and exit parts, respectively, for the former, and 3.48% and 5.78% in the entrance and exit parts, respectively, for the latter. The chemical composition of the river discharges is found to be rich in nutrients necessary for plant development, making it a potential source of crop field nutrients. The results suggest that regulating the amount of chemical compounds is possible by controlling the distribution of river flows in the river, as well as the fractional and chemical composition of the flow.

Particle clogging mechanisms in hyporheic exchange with coupled lattice Boltzmann discrete element simulations

The clogging of a stream bed has a significant impact on the exchange of water between a river and groundwater, known as hyporheic exchange. Clogging issues in orifices influenced by fluid flow have long been a concern, particularly in understanding clogging mechanisms and particle dynamics. This study focuses on investigating the behavior of poly-dispersed particle systems in the Shanghai soft soil using a coupled lattice Boltzmann method and a discrete element method (LBM-DEM). A particle-orifice model was developed based on LBM-DEM to study the clogging problem. Three different orifice diameters with the same particle size distribution were set at a microscopic scale. The simulation results indicate that the primary form of clogging is the formation of particle domes, exhibiting distinct characteristics depending on orifice size. As the orifice size increases, clogging becomes more challenging. Interestingly, the flow rate of fluid passing through clogged orifices is quite complex, as it does not decrease significantly. The formation process of the particle structure shows significant randomness, posing challenges for quantitative analysis and experimental validation. This study provides insights into the initial stages of clogging formation, leading to a better understanding of hyporheic exchange phenomena in stream bed ecosystems.

A mathematical model for predicting the deformation of the hydraulic model of the dynamics of water flow and morphological parameters of the riverbed in small mountain rivers

In this article, the changes of the bed of the Govasoy river, which is one of the small mountain rivers, due to the influence of constructions and the formation of the sedimentation layer are studied on the basis of field studies. The mathematical model of predicting the deformation of water flow dynamics and the processes of the bed, and the experimental results are compared with numerical solutions. Information on the territorial division of irrigation networks and water consumers in the Govasay river basin, as well as their digital maps, was created on the basis of geo-information technology. The program was developed to ensure the rapid management of water resources.

INFLUENCE OF THE SMALL HYDROPOWER STATIONS ON THE HYDROLOGIC PROCESSES IN THE SERET RIVER (LEFT TRIBUTARY OF THE DNISTER RIVER)

Sources of the Seret River are located near Ratyshchi village in Ternopil region. The river has the length of 248 km, the catchment area is about 3,900 km2. During the last 15 years seven small hydropower stations (SHPS) have been constructed in the Seret riverbed (Zahidhydroenergo, Velykohaivs’ka, Lux-2, Yanivs’ka, Chortkivs’ka, Bilche-Zolotets’ka, Bilche-Zolotets’ka-2, and Kasperivs’ka). Since all the SHPS are situated in the Seret riverbed and have a dam which decelerate water flow velocity, they influence the water runoff, sediments runoff, and water quality. After their building the cases of flooding of villages, overgrowing of the river bed reservoirs by algae plants became more often, and the long-term dynamics of the water and sediments runoff changed. To assess the water and sediments runoff changes in the catchment and to ascertain correlation between these changes and the SHPS the monitoring data sets of the Hydro-Meteorological Survey of Ukraine and the Carpathian Hydrological Observatory were analyzed. Recently the observations on the water runoff are implemented at two gauging stations: Velyka Berezovytsia village and Chortkiv city. The sediments runoff data are collected by the Chortkiv gauging station. The assessment of the water and sediments runoff changes in the Seret River in the period 1948–2022 and ascertaining of the role of water regulating by dams and reservoirs of small hydropower stations in the riverbed have been carried out. We also carried out a comparison of the sediments runoff module for the Seret River and the neighbouring Koropets River.

Reinforced soil wall with gabion facing – a case study of water front structure

The increasing demand for utilities infrastructure and development projects has become a key factor in providing feasible and economical solutions in recent decades. There is a need of the day, to utilize locally available resources while designing such projects. The Reinforced Soil Wall (RSW) with Gabion Facing provides a flexible modular environment-friendly structure that is proven to be suitable for waterfront structures, and feasible with available boulders in the vicinity. This paper showcases a case study of RS wall with Gabion Facing for the diversion of Ulwe River - a part of Navi Mumbai International Airport (NMIA) Project. A roughly 3.2km long river diversion has been widened, moreover, an approximately 90 mt high hill was flattened to pave the way for NMIA, adjacent to Panvel Creek. The proposed channel dimensions of the diversion river were increased after studying the data for the last 100 years of rainfall, so that the heavy rainwater can be discharged without flooding. The composite solution of the RS wall with metal gabions as a facia has facilitated the diversion of the Ulwe River to divert water flow up to Panvel Creek. The geogrids were installed with the stone–filled metal gabions, along with connector rods to form a positive connection. To prevent the scouring of the non-rocky river bed at RS wall base, the Gabion mattresses were provided.

Morphodynamic numerical modelling of bridge pier erosion induced by downstream check-dam partial collapse

The paper presents a case study in which a severe bridge pier erosion effect was triggered by a partial collapse of a downstream check-dam, due to a flood event in June 2020. The area under study is about 30 km east from the city of Udine (Italy), along the river Torre, which is the main tributary of the river Isonzo. In particular, it is 1 km downstream of the confluence between river Torre and its main tributary, river Natisone. The hydrodynamic complexity of the reach is further exacerbated by the presence of two bridges, close to each other and almost parallel (the new one is just upstream and it is under construction, although almost finished, while the old one is still in service). The result is that there are many bridge piers in the riverbed, determining some interference effects also increasing local erosion. The presence of a check-dam 600 m downstream of the old bridge had a stabilizing effect in this sense, although it was originally designed as a grade control structure of the river. The flood event determined a partial collapse of such structure, whose central portion was progressively excised by tipping. The backward propagation of the erosion reached the area of the bridges, determining a progressive general lowering of the river bed. As a consequence, many bridge piers of the old bridge were excavated, determining severe conditions for the stability of the structure (the traffic was interrupted). The paper presents the methodology adopted and the main results obtained by hydrodynamic and morphodynamic numerical analyses, which were conducted through a two-dimensional, finite volume, shallow water model able to determine the hydrodynamic fields (water depth and flow velocity) and the evolutionary trends of the river bed, allowing to identify the best retrofitting strategy for the design phase.

Assessment of Land Use changes and its impact on environment in the least populous district of Haryana through Remote Sensing methods (2001-2021)

In today’s world, almost every accessible piece of land today is being utilized for some or the other purpose directly affecting human needs. Not only is the land being used intensively, but is also evolving and changing with time. The rapid and intensive changes in land use and land cover (LULC) have created the need to quantify these changes in numbers and maps, so that we can understand this information to the best use possible. Thus, this paper aims to examine Panchkula district focusing upon the relationship of land use land cover (LULC) and the consequent changes in environment. Three annual LULC maps (2001, 2011 and 2021) were prepared with the help of satellite images. The change detection showed that built-up area has increased by approximately 268% in two decades with a total area of 10261.9 ha area in 2021, thus indicating that water bodies and barren land were converted into settlement for managing the population across the district and introducing infrastructure for the same. However, the forest and river bed area has increased by 19 % and 78.02 % respectively, while agricultural land was noticed to be increased by 55.62 % with a significant increase during 2001-11 and a slight decrease after 2011. The open scrub land has increased by 56 %. Thus, the present study can help with identifying areas experiencing significant changes in ecosystems and natural resources in the district. It can also provide valuable insights into the expansion of urban areas, changes in infrastructure and the encroachment on natural and agricultural lands, thereby contributing to urban planners to understand urban growth patterns, assess the impacts and make informed decisions regarding land zoning, infrastructure development and resource allocations.

Оценка загрязнения почв и грунтовых вод малой реки Локнаш в Московской области

The purpose of the study was to assess the level of contamination of soils and groundwater in the catchment area of a small river. For this purpose, the territory was zoned according to the intended purpose of the land and four categories were identified: agricultural lands, water fund lands, forest fund lands, and rural settlement lands. To assess the impact of each category on soil and water pollution, cross-sections were identified along the small river bed. The study determined physicochemical and microbiological parameters. Research results have shown that due to excessive anthropogenic load, groundwater is polluted with elements such as phosphates and nitrates. In addition, an increased level of phosphorus content is observed in the soil, and a general pattern is observed – the content of nitrogen, phosphorus, potassium, as well as the total number of soil microorganisms decreases from source to mouth.

Oxide Analysis of River Bed Sediments from Lower Reaches of River Forcados along Patani and Environ

Oxide Analysis of River Bed Sediments from Lower Reaches of River Forcados along Patani and Environ

An Increase in the Energy Efficiency of Vortex Micro HPP with a Flexible Outlet Siphon by Self-Adjustment of Flows in the Pressure Chamber

The article aims to increase the energy efficiency of the vortex micro-power plant, which would be achieved due to its compatibility with the terrain. In particular, the inlet channel connected to the water intake of the pressure chamber and the water collector placed in the upper pool by transverse joints, and the flexible siphon connected by vertical and horizontal joints to the diffuser of the same chamber with a telescopic end. The boundary conditions were selected with parameters such as the water flow acceleration according to the river bed’s slope angle and the inclination angle of the upstream channel near the vertical pressure cone chamber. The level difference between the upper and lower pools was adjusted. Inside the pressure chamber, the inclined guides of the small wings were hinged to its wall and were adjusted by ballasts. The reactive forces generated by the upward reflection of the incoming flow from the surfaces on the inclined small guide wings of the pressure chamber were a factor in curbing the said flow (compensating for the insufficient volume flow) and ensuring the continuity of the water supply to the turbine in shallow water. The mentioned circumstances allowed for improving the synchronization of incoming and outgoing flows. As a result of the above improvements, an increase in the energy efficiency (i.e., annual electricity generation) of 15–20 % was achieved.

AN INNOVATIVE APPROACH TO CALCULATE THE CRITICAL DEPTH IN A TRIANGULAR SHAPED-CHANNEL

This paper focuses on a procedure for the dimensioning of the triangular-shaped channel at critical flow, which is important in the practice of the hydraulic engineer. The proposed approach, which explores the potential offered by heuristic methods for solving complex optimization problems, is based on the use of an analytical method that is presented and applied for the calculation of the critical depth y<sub>c</sub>, which is governed by a cubic equation with no second-order term. The resolution of this equation is essentially based on Cardan's theorem. This method takes into account, in particular, the effect of the absolute roughness ε, the effect of the kinematic viscosity ν through the Reynolds number Re, and the effect of the channel bed slope S through the friction factor f. These parameters are easily measurable in practice. In this research, we relied mainly on the application of two universally accepted relations of Darcy-Weisbach and the Colebrook formula in a state of critical flow. Explicit relations are deduced that govern the critical depth, y<sub>c</sub>, by a particular examination of two cases; one is a turbulent flow over a smooth surface and the other is a flow over a rough surface.

Open channel velocity field investigation for hydrokinetic power generation

The paper presents an experimental study of a velocity field in an open channel. The study of water flow in an open channel is complicated due to the influence of various factors and different variables. Some of the variables affecting the flow parameters include the height of the water column, the width of the channel, the length of the channel, the slope of the channel, and the conditions of the channel bed. The investigated open channel is used for experimental research of kinetic turbines, and the flow speed in the channel is in the range of 0.1-0.3 m/s. The low velocity values in the channel are driven by the operation of the kinetic water turbines in real-world conditions. When describing the test channel, the influence of several boundary conditions has been taken into account, such as protrusions between the measurement sections, the water level, and disturbing effects. Results for the velocity fields determined in five sections of the test open channel are given. A turbine and an electromagnetic probe were used for the experiments. A comparison between the results obtained with the two measuring instruments under the same flow conditions in the test channel is made. The results for the velocity variation in the test sections for the maximum velocity in the channel are presented. At this maximum water velocity, the test channel maintains a water level of approximately 150 mm. The experimental data is also illustrated graphically, along with the velocity fluctuations along the channel centreline. The results obtained provide an idea of the expected velocity fields in the measurement open channel and the relative magnitude of the fluctuations in the different measurement sections.

Экспериментальные исследования устойчивости откосов мелиоративных осушительных каналов

The article presents the results of experimental studies of the stability of slopes of reclamation channels. Experimental studies were carried out on the Grand Channel of the Laboratory of Sprinkler Machines and Hydraulic Drive of the Department of Organization and Technologies of Irrigation and Reclamation and Construction Works of the Institute of Land Reclamation, Water Management and Construction named after A.N. Kostyakov. The work of the reclamation drainage system is accompanied by the appearance of sediments, siltation of herbaceous and shrubby vegetation at the bottom and slopes of the channel. For the normal functioning of the reclamation drainage system, it is necessary to maintain the design dimensions of the channels during the entire period of their operation. To clean drainage channels, special channel cleaning machines of periodic or continuous action on caterpillar or pneumatic wheels are used, and general construction excavators with widened buckets are also often used. The operation of all these machines with a large operating weight has a peculiarity, which consists in their movement in the process of cleaning along the channel along the berm sections close to the edge. Such a situation can lead to a violation of the stability of the slopes, which in turn disrupts the capacity of the channel bed and its design geometric dimensions. The study of slope instability from the loads of channel cleaning machines allows you to correctly design the channel section and form a cleaning technology.