<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Meandering of rivers is a spontaneous phenomenon that has been a challenge in the field of water resources and river engineering. The chaotic behaviour of meandering rivers causes spatiotemporal variation in the flood plains, which leads to their shifting or alteration. Structures built across the stream are rendered useless once the course of the stream shifts due to meandering. Also, certain projects that need to be planned and executed near these streams (for example, extension of an airport parallel to the banks of the meandering river), fall under the threat of being washed away or inundation with temporal variation in the stream form. Pilot channel is an artificially constructed channel to direct the main stream along the desired alignment. The present study is carried out for analysis of pilot channel concept using tractive force ratio approach for diversion of Beas River. Analysis of the pilot channel is done by HEC-RAS 4.1.0, which gives the discharge carrying capacity, sediment carrying capacity, bed degradation and aggradations etc. Finally, the validation of the new pilot channel is done with respect to its characteristic features, viz. discharge, sediment load, velocity, sediment carrying capacity and tractive force ratio (pilot channel to old river) etc.

World University root node

Center for Environmental Sciences & Engineering

Water and Energy International

Analysis of pilot channel concept using tractive force ratio approach for river diversion - A case study

Numerical model applications for sedimentation and flushing behaviour of storage reservoir - Case study

Insufficient spillway capacity has been the cause of one-third of all dam failures. An innovative and effective way of increasing the spillway capacity is to use a Labyrinth weir in the modified form of PKW having range of specific flow from 3 to 1000m3/s/m. As the flow approaches towards the PK Weir, it was observed that the Z-component of the velocity of water in lower levels increases which enhances the flushing capacity. One of the important observations is that with decrease in discharge from higher flow to medium flow; Z component velocity is getting lowered by about 14 percent. Increase in discharge from lower to medium flow Z component velocity is getting increased by about 40 percent. It indicates that at lower discharge, upward velocity component is appreciably more which may be helpful for significant amount of sediment suspension at lower discharge also. For flood flow, it was found that there has been reduction of around 25-30% of submergence depth with respect to ogee spillway. Induced flow characteristics near PKW and tractive stress exertion by flowing water in the inlet cell are capable to flush out even the coarser sand particles. © 2014 by Taylor & Francis Group, LLC.

Labyrinth and Piano Key Weirs II

Experimental study on vertical velocity and submergence depth near piano key weir

Artificial neural network (ANN) models have been developed for simulation of daily suspended sediment flux in the Subansiri River basin, which is a transboundary eastern Himalayan basin and the biggest sub-basin of the Brahmaputra River in India. Modelling was conducted on two datasets: (1) daily discharge and suspended sediment concentration data of 15 years (1993-2007) and (2) daily data of climate (rainfall, temperature) and snow cover area along with discharge and suspended sediment concentration for six years (2001, 2003-2007). The performance of ANN models has been compared with conventional sediment rating curves (SRC) and multiple linear regression models (MLR) having similar input data. ANN models were found to be considerably better than the SRC and MLR models. This paper concludes by providing discussion about how the different type of input data, length of input data and lagging of input data affects the accuracy of sediment flux estimation in a large Himalayan River basin and also provides guidance on the types of tasks for which different types of input data may be preferable. Copyright © 2013 IAHS Press.

IAHS-AISH Proceedings and Reports

Suspended sediment flux modelling in a transboundary Himalayan river basin

During the flood of 2001 in the Kosi River, a large portion of the river bank along the Western Kosi Main Canal (WKMC) between chainage 0.00 km and 4.237 km was damaged. The spur at chainage 2.25 km along the western flood embankment located near WKMC was also damaged during the flood of 2002. The Kosi Barrage Gate Regulation Committee in May 2003 inspected these sites and requested the Central Water and Power Research Station (CWPRS), Pune, to conduct model studies of Kosi River for effective river training works. This article describes the distorted hydraulic model studies conducted on the existing mobile bed model of Kosi River at CWPRS Pune with horizontal scale 1/500 and vertical scale 1/70. The results indicated that two spurs, one located at chainage 3.5 km and another at chainage 3.75 km, along the WKMC would help to deflect the flow away from the bank and reduce the flow concentration on the existing spur at chainage 2.25 km of Western Flood Embankment. © 2012 Taylor & Francis Group, LLC.

ISH Journal of Hydraulic Engineering

Experimental study on performance of spurs

Brahmaputra river system is very complex because of its braided flow pattern and high sediment load. It is one of the most braided river in the world in which the width of the river extends up to 22 km. The first part of the study includes developing a mathematical model for the river. Sediment transport capacity of the river has been done by using different method of transportation functions like Ackers-White, Yang and Engelnd-Hansen methods. The result shows that Yang's method of transportation function gives a better result for Brahmaputra River when it is compared with the other transportation functions. From these transportation functions Ackers-White method of transportation function gives high value of sediment transport capacity and high value of change in channel invert. The second part of the study is to channelize the river by putting river training structures at selected nodal points. These nodal points are selected based on the channel geometry and property in which channelization of the river can be possible. Some cross sections of the river are much braided in nature and it may not be economical to confine the flow over the whole reach of the river. Flow guide bunds are adopted as a river training structure which used to confine and guide the flow to a gentle channel. Especially these structures are constructed on the banks of the river at bridge site locations to guide and confine flow. Other structures which are adopted as channelization work are closing of secondary channels by putting bed bars, permeable spurs, porcupine screens, Jack Jetty etc.

Simulation study for channelization of the brahmaputra river in Assam

In recent years, spillway rehabilitation has increased in importance and become the subject of many projects worldwide. One solution for this problem is the implementation of a new type of labyrinth spillway, called Piano Key Weir (PK-Weir ). This is an excellent alternative for increasing the overflow capacity of existing dams. Similarly to traditional labyrinth weirs, the hydraulic capacity of a PK-Weir is a function of its geometrical characteristics. Currently, there is a lack of systematic experiments, and the existing data does not allow the proposition of a universal design procedure. This paper reviews the previous studies on the efficiency of planned and built PK-Weirs. The results are evaluated by comparing an actual PK-Weir's discharge to that theoretically obtained for a sharp-crested spillway with crest length equal to the width of the PK-Weir for a given hydraulic head. On the basis of this evaluation, a preliminary design procedure is proposed. © 2012 American Society of Civil Engineers.

Civil Engineering

(SoE) School of Engineering

Journal of Hydraulic Engineering

Discharge capacity of piano key weirs

The present work explores relations between stream power, braiding intensities and bank erosion in certain stretches of the Brahmaputra River. In this paper, an objective approach is presented to enable quantitative assessment of spatio-temporal behaviour of channel braiding process of the Brahmaputra River by using the Plan Form Index and corresponding estimation of stream power to establish a behavioural pattern of variability of potential energy expenditure. The braiding index is compared for discrete years to understand the morphological behaviour. Subsequently, a real time estimation of stream power for certain stretches of Brahmaputra River is done in order to analyse its variability in braiding intensity and bank erosion. The paper presents the dynamic behaviour of the channel pattern of the Brahmaputra River System in Assam valley of India over a time span of 18 years. The procedure addresses the selection of input parameters from digital satellite images, comprising scenes for the years 1990, 1997 and 2007 with specific dates, from Dhubri near Indo-Bangladesh Border to Upper Assam. Deployment of GIS technique has been made to extract the required parameters to derive Plan Form Indices for the entire study reach. Stream power estimation is done for corresponding latest floods and for corresponding dates of image scenes. The study indicated that due to consistent aggradation of riverbed inducing temporal declination of stream power, there is an occurrence of wide spread braiding. This in turn incurs substantial yearly land loss due to bank erosion, caused by flow concentrations due to temporal evolution of multiple channels in the Brahmaputra River. © 2011 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.

International Journal of Sediment Research

Braiding process and bank erosion in the Brahmaputra River

The change of the Brahmaputra basin characteristics has been studied covering around 620km of the River reach in Assam flood plain within Indian Territory. The changes in land use and land cover pattern in the Brahmaputra catchment instigate a significant increase in sediment inflow to the Brahmaputra River System. Land use change may influence many natural phenomena including ecological processes, soil erosion, sedimentation and variations in runoff and soil moisture conditions. Hence, understanding the morpho-dynamic behavior of the river with an extra emphasis on land cover and plan form changes is substantially crucial, so far as impact on the sediment inflow to the river system is concerned. More recently, Sharma and Akhtar (2010) studied the braiding behavior of River Brahmaputra for the discrete years 1990, 1997 and 2007- 08 using remote sensing data based analysis. Their study emphatically suggests a sharp increase in braiding intensities during the aforesaid study period. With above strategy, an objective is set in mind to study in regard to assessment and impact of the land cover changes. Which has been urgently needed for better understanding of the causative factors those influence the braiding pattern, sediment inflow as well as bank erosion phenomena. Hence, for the same discrete years, it is endeavored to study and analyze thebasin characteristics using Landsat (TM) images for the discrete years between 1989 to 2010; covering the catchment area of the River in the three riparian countries (China, India and Bangladesh). NDVI (Normalized Difference Vegetation Index) maps of the study area have been created by considering seasonal vegetation cover changes. Supervised classification was done using MLC (Maximum Likelihood Classifier) to help distinguish between various land cover classes. Change detection algorithm was implemented to determine the changes in vegetation cover in the watershed, floodplain vegetation, vegetated islands, extent and pattern of low flow channels, and exposed sand bars at selected points along the reach. For the same discrete years, a significant change in NDVI values have been registered out of the study, resulting in substantial decrease in vegetation cover and inducing severe channel migration in recent years. Another outcome of the study is that the land cover change in the watershed is not fairly uniform. The landcover change especially, change in vegetation cover surmised to be the vital contributor to the increase in sediment inflow into the Brahmaputra River and its tributaries. © 2011 ASCE.

World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress

Satellite data based impact assessment of basin characteristics for brahmaputra river system of India

<p>Piano Key Weirs are modified version of labyrinth weir with innovation to improve discharging capacity and more compatible for constructing on a existing or new spillway with lesser space requirement and structural stability. The objective of this study was to identify the Piano Key Weir in which the maximum discharge capacity at different UW with p (height of weir) could be achieved. To achieve this for different flow conditions, length magnification ratio (L/W) is taken from 3.56 to 7.40. Also, other parameters are taken in different combinations for getting optimum configuration of Piano Key Weir for better performance. With this in view, three phases of experimental campaign on eighteen Piano Key Weir models are reported in this paper. The ratio (r) of Piano Key Weir to linear weir discharge for a given head was seen to be more than one and found to increase with magnification ratio L/W upto a certain limit of h/p ratio. It was also found that performance of ratio of inlet and outlet cell width was best when two cells were of same width. The analysis of discharge coefficient variation is correlated with h/p. © 2011 Taylor &amp; Francis Group, LLC.</p>

Experimental study of hydraulically efficient piano key weir configuration

Labyrinth weirs are normally built to increase the total effective crest length for a given spillway width. They can be used to increase the discharge capacity for a given head or to decrease the head for a given discharge. As their application is sometimes difficult in rehabilitation projects due to inappropriate supporting conditions, a new concept of labyrinth spillways was mooted by Lemperiere et al. with a new shape, called Piano Key Weir. This innovative alternative of labyrinth spillway provides an increase in the stability of the structure which can be placed on the top of most existing or new gravity dams, unlike traditional labyrinth weirs. This paper focuses on the experimental results and physical modelling tests of the evacuation system of Sawara Kuddu Hydro Electric Project 110 MW located in Lower Himalayan mountain ranges of India with the Piano Key Weir and the energy dissipation structure. The physical modelling has been carried out at the River Engineering Laboratory, Water Resources Development and Management, Indian Institute of technology, Roorkee, India in the framework of the rehabilitation project. © 2011 Taylor & Francis Group, London.

Labyrinth and Piano Key Weirs - Proceedings of the International Conference on Labyrinth and Piano Key Weirs, PKW 2011

Rehabilitation of Sawara Kuddu Hydroelectric Project - Model studies of Piano Key Weir in India

Submerged vanes are submerged foils of low height and larger length, constructed in a river at an angle of attack α to the flow to modify the near-bed flow pattern and redistribute flow and sediment transport within the channel cross section. At a Froude number (F) of 0.13, the local scour development around the submerged vane without a collar was not enough to dislodge the vane whereas at F=0.25, there was a significant local scour hole around the vane and the vane was dislodged. With the introduction of a collar at the leading edge of a submerged vane, the scour depth at the leading edge of the vane was reduced to zero. A collar of circular shape was found more suitable for a rectangular vane. Recommendations for sizing collars at two values of F are given. The optimal α for a rectangular vane with a collar was found close to 40°. The study clearly indicates the advantages of using collars in case of submerged vanes and provides insight into selection of appropriate collar shapes. © 2010 ASCE.

Enhancing utility of submerged vanes with collar

The submerged vanes are vortex generating device which function through generation of secondary circulation for bringing about desired sediment redistribution within the channel cross-section. Strength of vortex is important for the comparison of strengths of different vortices. Evaluation of torque is little more complicated than the evaluation of moment of momentum. Therefore, instead of evaluating torque, moment of momentum can be evaluated as the strength of vortex. All the three components of velocity can be measured using Acoustic Doppler Velocimeter. Grids across the flume in vertical plane can be considered for the measurements of components of velocity. Moment of momentum depends on wide range of variables. The dimensionless moment of momentum can be considered for the evaluation of strength of vortex. © 2010 Taylor & Francis Group, LLC.

Aspects of moment of momentum for vortex strength

The applicability of Lacey's equations is tested for the river Brahmaputra. It is found that the river follows the structure of Lacey's regime equations. The perimeter and the area coefficients found in the modified regime equations are much higher than the corresponding coefficients in Lacey's original equations. Similarly, the velocity coefficient for the river Brahmaputra is considerably smaller than the coefficient in Lacey's corresponding velocity equation, whereas the coefficients of the equations for the hydraulic radius are of the same order. © 2008 International Association of Hydraulic Engineering and Research.

Journal of Hydraulic Research

Lacey regime equations for river Brahmaputra

This paper presents the results of a trialling of the use of Indian Remote Sensing (IRS) satellite imagery for mapping the geomorphology and physical habitat of the Brahmaputra River in Assam, India. The study was undertaken on a 110 km reach as the river emerges out of the Himalayas; a reach with a complex braid pattern and high levels of channel instability. Image analysis on four sets of IRS data encompassing a period of 13 years (1990-2002) was undertaken to detect basic changes in the extent and pattern of low flow channels, vegetated islands, exposed sand bars and floodplain vegetation. Simple unsupervised classification techniques were applied to the images. The water surface of the low flow braided channel network, however was mapped more accurately using the GROW facility within ENVI 4.1; a technique based upon mapping areas within a given number of standard deviations in terms of pixel values within a training area. Subsequent to this unsupervised classification of the water surface area allowed classification of the water in to three water types based on depth and separation of isolated pools and backwaters from the channels conveying flow. Overall classification accuracies of 82.5% were achieved in relation to mapping physical habitat; varying between 86 and 95% for the four different dates. Analysis of the nature of channel planform and habitat change showed that there has been a 3.7% increase in the active channel area consisting of exposed sediment and water within the river corridor. This substantiated a general awareness of an increase in the width and reduction in depth of the Brahmaputra River over the last few decades. The analysis also depicts the occurrence of a major avulsion and the highly dynamic nature of the braided channel network and sand bars. Overall the study demonstrated that simple classification methods when applied to satellite data, capturing imagery in the visible and near infra-red, can be used to measure important changes in the geomorphology and physical habitats that make up the fluvial system of the Brahmaputra River. The approach may also be more widely applicable to large river systems comprising a mosaic of water, exposed sediment and spectrally different vegetation communities. Copyright © 2008 John Wiley & Sons, Ltd.

River Research and Applications

Quantifying channel planform and physical habitat dynamics on a large braided river using satellite data - The Brahmaputra, India

Tapered submerged vanes are installed in Wapsipinicon river bend in the USA and outside a new water intake in Nepal. Taper angle is the angle made by leading edge of vane with horizontal in vertical plane. A tapered vane also induces something called the vortex lift (at high angles of attack) which is a secondary lift caused by a reattachment of the flow due to a spanwise leading edge vortex. The aptitude of the vane/ foil to form this leading edge vortex is highly dependent on the shape of the leading edge, generally a sharp leading edge will form a strong vortex whilst a rounded leading edge will form a weaker vortex (with the vortex centre further downstream). In this paper, the effect of taper angle variation within a range 33.7° to 45° on moment of momentum (MOM) has been investigated and it is observed that for a given optimal angle of attack as 40°, MOM can be further increased by keeping the taper angle as 33.7°. © 2007 International Association of Hydraulic Engineering and Research.

Performance evaluation of tapered vane

Free-flow spillways are simpler and safer than gated ones, but the low specific flow of their traditional shapes requires high spilling nappe depths and thus huge losses of storage (100 × 109m3 worldwide). A newly evolved shape of free-flow spillway (the "Piano Key weir") has the potential to increase the specific flow as high as fourfold at lower discharges. It could substantially increase, at low cost, the safety and the storage and/or the flood control efficiency of many existing as well as new dams. It is thus very advantageous to increase the specific flow as much as possible. Some tens of existing spillways have been designed accordingly as vertical walls on a flat bottom, with a trapezoidal labyrinth layout which is much longer than the spillway length (often four times). They usually double the specific flow of an Ogee Spillway. Piano-Key Weir derives its name from its plan-form shape which looks like a 'piano-key'. It is configured as polygonal walls such as to provide a much longer crest length than the conventional ogee spillways. This paper presents experimental data analysis on this new (not patented) solution in order that: Increasing the storage of many irrigation dams is justified by the increased needs or due to the sedimentation of reservoirs. Increasing the spillage capacity is often justified by a better knowledge of hydrology. Improving flood mitigation by existing dams may be very cost effective. Positive outcome of this study will be very much relevant for dam safety concerns worldwide in the context of adverse hydrological consequences due to ongoing global warming phenomenon.

Association of State Dam Safety Officials - Dam Safety 2007

The piano key weir: A new dam safety solution for enhanced spillway capacity

Submerged vanes are submerged foils of low height (H) and higher length (L) structures, which are constructed in river at an angle of attack to the flow to modify the near-bed flow pattern and redistribute flow and sediment transport within the channel cross-section. The aspect ratio of submerged vane is defined as H/L. The aspect ratio of submerged vane is one of the most important parameters which influences the generation of strength of vane induced secondary circulation. At 2.5H downstream of vane, dimensionless moment of momentum MOM*, MOM**, MOM*** increase with the reduction in aspect ratios of submerged vane. The strength of vortex induced by vane among three values of aspect ratios such as 0.25, 0.33 and 0.50, is maximum at lowest aspect ratio 0.25. At lowest aspect ratio, the maximum value of vane-induced strength of vortex led to the increased deposition of sediments (dike). Generation vortex starts right from the leading edge and it is amplified till it reaches the trailing edge of submerged vane due to increase in vane length.

Performance evaluation of aspect ratio of submerged vanes

At optimal angle of attack, vanes have the maximum strength of secondary circulation. For the same hydraulic condition, the maximum strength of vane induced secondary circulation also depends on their shapes. Optimal angle of attack in case of rectangular submerged vane with collar is very close to 40° where as in case of double curve vane type I, double curve vane type II, J1 type and J2 type vane is very close to 45°. Strength of vane induced secondary circulation in terms of moment of momentum depends upon various parameters. A dimensional analysis approach has been attempted to get dimensionless moment of momentum. The maximum strength of vane induced secondary circulation in terms of dimensionless moment of momentum is greater in case of rectangular vane than that in case of curved vanes in the same flow conditions and same height and length of vanes. © 2006 Taylor & Francis Group, LLC.

Vorticity with different shapes of submerged vanes

The forecast of a hydrological time series has been one of the most complicated tasks due to wide range of data, uncertainties in the parameters influencing it and lack of adequate data. Feed forward multilayer neural networks are widely used as predictors in aquatic fields of applications. The paper demonstrates the potential of artificial neural network (ANN) models for simulating and forecasting daily river stages at Pandu, Pancharatna and Dhubri gauging sites of the river Brahmaputra. Back propagation method has been chosen. The main purpose has been the modelling of the river Brahmaputra. in àmulti gauging station catchment and real time forecast of daily stage downstream. Model efficiency of all the networks override the conceptual idea of use of the ANN has been clearly articulated.