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The continuous lowering of Lake Michigan-Huron levels has caused increasing concerns. St. Clair River, which drains Lakes Michigan and Huron to Lake St. Clair-Lake Erie, appears to bear much of the blame. The three most possible causes are the erosion of the St. Clair River bed, relative change in net basin supply (NBS), and differential glacial rebound. Dredging and erosion so induced might have changed the river conveyance. In this paper, only sediment erosion will be considered. Among many other things, sand/gravel mining, sediment supply into the St. Clair River, and changes of the river cross section at some critical points may have affected the conveyance. In this study, a two-dimensional numerical code, HydroSed2D, will be used to investigate whether the St. Clair River is still eroding under current flow conditions. HydroSed2D is a two-dimensional depth-averaged hydrodynamic code with a sediment transport module. It is based on the shallow water equations. This code has been used in many engineering applications. Bathymetry data is compiled from different sources (single beam and multi-beam echo sound surveys). Sediment size distribution information is from the image analysis of under water videos. With the bed shear stresses results, the possibility of sediment movement in the St. Clair River is analyzed.

This paper describes part of the work presented in Leon et al. (2009), which presents integrated boundary conditions (BCs) for simulating free surface, pressurized, and the simultaneous occurrence of free surface and pressurized flows (mixed flows) when the free surface region is modeled using the 1D Saint-Venant equations and the pressurized region is modeled using the 1D compressible waterhammer equations. The present paper describes the results of the application of the integrated boundary conditions for modeling free surface, pressurized, and mixed transient flow conditions in two test cases. The first test case is a hypothetical test and the second is an experimental work in an oscillation tube performed by the authors of this paper. Computational Fluid Dynamics (CFD) modeling results were used as frame of comparison for the first test case and experimental results besides CFD results were used for the second one. The results show that the integrated boundary conditions can be used with good accuracy for simulating complex storm-sewer systems in free surface, pressurized and mixed flow conditions. The integrated boundary conditions are general and they can be used to simulate point and storage junctions with any number of inflowing and outflowing pipes. The integrated boundary conditions were implemented in the Illinois Transient Model (ITM), which has been used to study hydraulic transients in the Calumet system of the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). The results of the latter study are not presented in this paper.

Bubbly Creek was historically used as a drainage channel for the waste resulting from Chicago’s stockyards. Nowadays there is flow in the creek only during rainfall events resulting in Combined Sewer Overflows (CSO) and water quality is a very important issue, particularly during the summer months, when the dissolved oxygen levels are extremely low and sediment oxygen demand is expected to be large. Due to the particular flow regimes of the creek and the conditions of the benthic sediments in the bed, a special BOD-DO (Biochemical Oxygen Demand Dissolved Oxygen) water quality module was developed and implemented into the two-dimensional depth-averaged numerical model STREMR-HySedWq. The approach illustrated represents a substantial improvement to the state-of-the-art of water quality modeling methodologies. The model was able to capture the key processes and provide useful preliminary results for the two following scenarios: [1] CSO events, for which the model was coupled to a one-dimensional cross-section-averaged BOD-DO water quality model, and [2] potential “purification” solutions, such as flow augmentation and supplemental aeration, with the goal of increasing the DO levels in the creek during dry weather periods. DESCRIPTION OF BUBBLY CREEK

The hydrodynamics at two design discharges (85 and 15% exceedence on the flow duration curve) in the vicinity of the existing North Branch Dam are presented. A combination boat chute/fish passage is being designed for integration into the existing dam. The Dutch pool and orifice fishway has been selected for the fishway due to its relatively low flow requirement (on the order of 5 cfs for most operating heads), low velocities in the fishway, and relatively low turbulence in the fishway – all making it a reasonable option for passage of non-anadromous fish in a low-gradient waterway. The details of the hydrodynamics of this structure are being examined with a combination of a physical model study and through the performance Computational Fluid Dynamic (CFD) modeling. 1. CURRENT SCENARIO – CHICAGO NORTH BRANCH DAM Prior to installing a potential boat chute design within the physical hydraulic model, several case scenarios of the boat chute design will be considered and tested, therefore optimizing its design. Prior to developing a CFD model at prototype scale for the North Branch Dam including any boat chute/fishway design, it is necessary to simulate the current (dam alone) flow structure in the vicinity of the dam to provide a background for future comparisons. Since the aim is to have the boat chute designed and tested to cover a wide range of flow discharges (30 – 223 cfs, corresponding to a flow exceedence of 85% and 15%, respectively), it is important to obtain CFD results for these two flow conditions. Hydrologic data upstream of the dam was obtained from a USGS gaging station 05536105 – North Branch of the Chicago River at Albany Avenue. Flow data for the North Shore Channel upstream of the confluence was obtained for the USGS gaging station 05536101 – North Shore Channel at Wilmette, IL and outfall data from the North Shore Waste Water Treatment Plant operated by MWRDGC. A three-dimensional model (FLOW3D, Flow Science 2008) CFD models that solves the Navier-Stokes equations together with a model for turbulence (RNG, Yakhot and Smith, 1992), and an interface capturing method (VOF, Hirt and Nichols 1981) is applied to determine the flow 3107 World Environmental and Water Resources Congress 2009: Great Rivers © 2009 ASCE

This work is part of a long term project which aims to simulate (1) the hydrology, (2) street flows, (3) flow interception at inlets and (4) storm-sewer flows in urban areas. The present work describes the application of the model using only the first two modules. The hydrologic model (first module) transforms rainfall to runoff using the kinematic wave approximation and simulating the infiltration process with the Green-Ampt method. The street model (second module) is based on a finite volume-shock capturing scheme that solves the full conservative Saint-Venant equations and can be used to simulate subcritical and supercritical flows. The formulation of boundary conditions at the street crossings in the street model is general and can be used for any number of streets, any combination of inflowing and outflowing streets, and any flow type (e.g., supercritical flows). The model using the first two modules is fast and robust and it has several potential applications. Perhaps the most important one is that it can be used in new urban developments to identify critical zones of urban flooding (e.g., zones with high water depths and flow velocities) in order to take appropriate measures of drainage control (e.g., to increase capacity of inlets). This model can also be used in developed urban areas to locate the critical areas in case of inlet clogging. In order to illustrate the capabilities of the model (first two modules) it was applied to an urban catchment in the village of Dolton, a southern suburb of Chicago. The watershed of this village drains to the dropshaft CDS-51 in the Calumet TARP (Tunel and Reservoir Plan) system which is operated by the Metropolitan Water Reclamation District of Greater Chicago. The fact that this model is fast makes suitable its application to large urban areas.

Sedimentation Engineering: Theories, Measurements, Modeling, and Practice (ASCE Manuals and Reports on Engineering Practice No. 110) is intended to supplement ""Sedimentation Engineering: Classic Edition"" (ASCE Manuals and Reports on Engineering Practice No. 54), a seminal text on the nature and scope of sedimentation problems, methods for their investigation, and practical approaches to their solution.""Sedimentation Engineering: Theories, Measurements, Modeling, and Practice"" updates selected topics in the original manual and addresses new topics, such as the hydraulic action of flowing water in the context of rivers and inland water bodies.

Flow restrictors or rain blockers are devices installed at inlets or manholes to limit storm runoff entering a Combined Sewer System (CSS). One type of these structures is the vortex flow restrictor (VFR). Although a large number of this type of restrictor have been installed in CSSs in urban areas, the authors are not aware of any systematic study on the performance of the VFR in limiting peak flows. Herein the results of an experimental and numerical study of a VFR are presented. For the numerical study, a state-of-the-art three-dimensional Computational Fluid Dynamics (CFD) model was used. The numerical results for the discharge coefficient and rating curves show good agreement with the experimental observations. The results show that the flow discharge passing through a VFR can be reduced substantially compared to the case where no flow restrictor is in place. The results also show that the flow discharge depends strongly on the way the VFR is installed.

The Chicago Waterways System (CWS) is very complex and a complete understanding of theflow and water quality phenomena is notpossiblewith current modelingtools. Amongmany interesting aspects, bi-directional flows have been observed in the Main Branch of Chicago River (MBCR) during winter time. Instead of flowing downstream into the South Branch (SB), part of the water from North Branch (NB), which usually carries runoff from a 100 square mile watershed and treated municipal sewage effluent released by the North Side Water Reclamation Plan (WRP), might flows into MBCR. This will have a huge impact on the water quality in MBCR, where the downtown Chicago is located. Physical model and field measurements of the CWS have been done to investigate the possible cause. Through these previous studies, density current has been identifiedas one of the main cause. A preliminary three dimensionalnumerical model also has been used in University of Illinois at Urbana and Champaign (UIUC) to simulate the density current. Although the bi-directional flow phenomena have been reproduced in the 3D model, the flow conditions are simplified and only very short period of time is simulated. In this paper, a three-dimensional environmental fluid dynamics code (EFDC) is used to simulate the flow in the Chicago River system (including NB, SB, and MBCR). EFDC is a public domain code which is supported by the Environmental Protection Agency (EPA) and has been widely used in many rivers and estuaries. It uses stretched or sigma vertical coordinate and Cartesian or curvilinear, orthogonal horizontal coordinate. Three-dimensional, hydrostatic, free surface, and turbulent flow equations are solved. Water quality models (such as sediment, temperature, toxics, dissolved oxygen, and biological oxygen demand) are also implemented. For this paper, the EFDC code is modified to simulate only the density current in CWS mainly due to the dissolved particles. The tests cases used in this paper are from the physical model work done in the hydrosystems lab in UIUC. The numerical model is validated and tested against the experiments. Good results have been achieved. More numerical simulations will be done to expand the parameter space. Water quality models will be activated in the future to see the environmental impact of different management strategies.

A three-dimensional numerical model was developed for the proposed primary settling tank (PST) for the Calumet Water Reclamation Plant (CWRP) in Chicago, IL. The numerical model can deal with three-dimensional multi-phase turbulent flow. Two-fluid model is used to capture the behavior of the solid-water mixture. Hindered settling was modeled by an empirical exponential relationship between the settling velocity and the solids concentration. The sludge was modeled as a Bingham plastic with parameters estimated from experiments. During the design, the most important parameters are the tank’s depth and diameter. These two parameters are also the controlling factors for the construction cost. Other parameters include the inlet/outlet structure, feed well depth/diameter, bottom slope, etc. The tank diameter is fixed due to the space restriction. The tank depth and feed well depth were analyzed by comparing different options. Once these two parameters were fixed, other parameters were fine tuned to optimize the performance of the tank. Due to the length of this paper, only the simulations for the tank depth and the feed well depth are introduced.

During the winter months, the Chicago River in Chicago, Illinois is subject to bi dire ctional flows , and density currents are thought to be responsible for the se flow variations. This paper presents detailed field measurements using three acoustic Doppler current profiler instruments and simultaneous water -quality measurements made during December 2005 . Observations indicate that the formation of density currents within the Chicago Riv er and density differences are mostly due to salinity differences between the North Branch and the main stem o f the Chicago Rive r, wh ereas temperature difference does not appreciably affect the creation of density currents. Sources of higher water temperat ure, conductivity, and salinity values should be addressed in future studies.

A numerical model for local scour with free surface and automatic mesh deformation is constructed and numerical simulation is carried out to compare with experimental results. The k2 model is used to simulate the turbulent flow field. Two interfaces (water and air, water and sediment) in the domain are captured with different approaches. The free surface of the flow is captured by Volume of Fluid (VOF) scheme which is a Eulerian approach. The water-sediment interface (bed) is captured with moving mesh method which is a Lagrangian approach. The flow field is coupled with sediment transport using a quasi-steady approach. Good results have been obtained using current model. The flow field is comparable with the experiment. Scour patterns are similar to the experimental data. INTRODUCTION In this paper, a new numerical model is proposed to simulate the scour process together with free surface and automatic mesh deformation. In scour problem, there are two sharp interfaces: water-air and water-sediment. The two interfaces are captured using different methods. The water-air interface is captured by Eulerian method, namely VOF method. The water-bottom interface is captured by Lagrangian method, namely moving mesh method. In numerical simulation of open channel flow, free water surface is usually replaced by a rigid lid. This is valid only if the free surface does not change too much along the channel. There are many surface tracking or capturing method available to simulate the free surface, e.g. marker and cell (MAC) method, volume of fluid method (VOF) method (Hirt and Nicholls 1981), level set method (Sethian 1996). In this paper, a high resolution VOF method proposed by Ubbink and Issa (1999) is chosen to track the free surface. The CICSAM (Compressive Interface Capturing Scheme for Arbitrary Meshes) scheme treat the whole domain as the mixture of two liquids. Volume fraction of each liquid is used as the weighting factor to get the mixture properties, such as density, viscosity.

ASCE Manual 54 Sedimentation Engineering, edited by the late Professor Vito A.Vanoni, provides both qualitative and quantitative guidance to theoreticians and practitioners with respect to sediment issues and processes associated with the development, use and conservation of water and land resources. It describes the nature and scope of sedimentation problems, details methods of investigation, and presents practical approaches to solution and management. As a major contribution to the profession, Professor Vanoni organized, partially wrote, and edited the definitive Manual 54. As chairman of the special Task Committee, established in 1954 with the charge of writing the manual, Vanoni worked for two decades and set a high standard. Many of the sections of the original manuscript for the book were first published in the Journal of the Hydraulics Division ASCE and received considerable discussion, which was taken into account in the final manuscript. Manual 54 received worldwide recognition and widespread use in academia and practice, being recognized with the ASCE Karl Emil Hilgard Hydraulic Prize for best publication in 1976. Since the publication of Manual 54 in 1975, global awareness of sediment erosion, transport and deposition processes and of their impact on the use and development of water and land resources has greatly increased. Manual 54 remains an important reference on many aspects of sedimentation engineering, but in other aspects it has been outdated by advances in knowledge and techniques and by the emergence of new problems and issues.

This paper focuses on the formulation and assessment of a second-order accurate Finite Volume (FV) shock-capturing scheme for modeling two-phase water hammer flows using the singleequivalent fluid approximation. The FV formulation of the proposed scheme ensures that mass and momentum are conserved. For achieving a second-order rate of convergence for smooth transients (i.e., flows that do not present discontinuities), a second-order boundary condition is implemented using virtual cells and the theory of Riemann invariants, which is similar to that used for the Method of Characteristics (MOC). Since the two-phase flow governing equations when using the single-equivalent fluid approximation are the same as the one-phase water hammer equations (with exception that the pressure-wave celerity is constant in the latter case), and because analytical solutions are available for the latter case, the numerical efficiency of the proposed model is tested using the one-phase water hammer equations with constant pressurewave celerity. The validity of the single-equivalent fluid approximation and the proposed scheme herein are verified with laboratory experiments. For one-phase transient flows, numerical tests were performed for smooth and strong transients. For smooth transients, the results show that the efficiency of the proposed scheme is highly superior to the fixed-grid MOC scheme with space-line interpolation and another second-order FV scheme. For one-phase strong transient flows, the results show that the efficiency of the proposed scheme is highly superior to the MOC scheme, and significantly superior to the other FV scheme for coarse grids. For fine grids, the accuracy of the proposed scheme converges to that of the other FV scheme. For two-phase water hammer flows, the results show good agreement between experimental data and the results of numerical simulations.

Experiments were conducted to study burial of cylinders placed on a sandy bed under combined waves and currents. The burial of a finite-length cylinder was determined by local scour around the cylinder and by a more global process associated to the formation and evolution of ripples and sandwaves. Experimental tests covered cylinder Reynolds wave numbers and Keulegan-Carpenter numbers within the ranges 10 ≤ Re ≤ 9.1x10 and 2 ≤ KC ≤ 26, respectively. Observations indicate that existing semiempirical formulae for prediction of equilibrium burial depth for pipelines are not completely suitable for the case of a cylinder having a finite length. In these experiments burial depth shows a strong dependency on both the Shields parameter (θ) and the Keulegan-Carpenter number (KC) combined. Introduction The dynamics of the interaction between objects and movable beds in a wavecurrent combined flow is very relevant having, in nature, an intrinsic strong complexity at the same time. Multiple applications, from military to civil can be associated to this particular phenomenon (Voropayev et al., 1998, 2003; Bennett, 2000). Cokgor (2002) studied the behavior of the lift and drag coefficients around partially buried cylinders on a rigid bottom exposed to combined waves and currents for low Keulegan-Carpenter (KC) numbers (here, D T U KC w m / = , where Um is the maximum value of the undisturbed orbital velocity at the bed, Tw is the wave period, and D is the cylinder diameter). Both coefficients, lift and drag, seem to be governed primarily by KC for both, waves alone and combined flow. Other studies on combined flows, in the laboratory and in the field, have also shown that both the ultimate scour depth and the time scale of the self-burial process of short cylinders are primarily functions of the Keulegan-Carpenter number (KC) and the Shields parameterθ (Bayram and Larson, 1998; Sumer and Fredsoe, 2001). The same parameters also affect the scour around vertical piles in the field subject to combined waves and currents (Sumer and Fredsoe, 2001). Additionally, they showed that the scour depth increases as the current velocity increases and is essentially unaffected by the direction of wave propagation. Earlier, Voropayev et al. (1999) studied the dynamics of disk-shaped objects placed on a sandy Copyright ASCE 2005 EWRI 2005 2 bottom under an oscillatory flow and showed that the burial depth of the cobble does not depend on the specimen’s density. Similar results were obtained for the case of a cylinder horizontally placed over a sandy bed (Sumer and Fredsoe, 2001). More recently, Voropayev et al. (2003) have investigated burial of finite-length cylinders over a sandy floor with a sloped bottom under shoaling waves. Such study showed that the final burial depth depends of both the KC number and the Shields parameter while the length of the scour hole depends mostly on the KC number. Additionally, Voropayev et al. (2003) showed that the cylinder may undergo periodical burial depending on the ratio of cylinder diameter to the height of migrating ripples. Similar observations were reported later by Catano and Garcia (2004) for the case of a zero sloped bottom under combined waves and currents. Systematic experimental research coupled with mathematical modeling that can incorporate the interaction of environmental forces on a cylinder under coexisting flows, considering different properties for both specimen and sediment are still needed (Friedrichs, 2001). Burial and scour processes induced by the hydrodynamic forces acting over the cylinder, coupled with fluidization of muddy bottoms under strong storms, are of particular interest since they convey a more rapid burial process (Admiral and Garcia, 2000; Sumer and Fredsoe, 2002). In this study, laboratory results were analyzed and a new predictive formula relating the burial depth to the KeuleganCarpenter number and the Shields parameter has been developed through basic curve fitting. The main goal of the present work is to contribute to enhance the current understanding of the processes responsible for the burial of finite-length cylinders under the action of waves and currents In this paper, we present results of experiments on the cylinder-burial process for several combinations of wave amplitude, wave length, and period, and constant water depth set to 56 cm. Three dimensional mapping of the evolution of bedforms and scour patterns around cylindrical models under waves alone and combined flow show the influence of both local scour and global bedform evolution on the final relative burial depth and net vertical displacement of the object. Sandwaves are shown to control the vertical displacement of the specimen after they form. It is seen that the vertical displacement of the cylinder does not longer coincide with the burial depth. This is primarily due to the more or less exposition of the specimen to the flow action according to its relative position over the bedforms as they migrate. Experimental setup and test conditions Experiments were conducted in a tilting water flume that is 49 m long, 1.83 m wide, and 1.22 m deep (Figure 1). The longitudinal slope of the flume was set to zero. The floor of the flume is made out of steel while the side walls are made of Plexiglas. A current was achieved by recirculating water in the flume with the help of a constant head tank and a pump. A piston type wavemaker was used to generate regular waves. The wavemaker consists of a flat, vertical steel plate equipped with wooden wipers to prevent leakage around the plate, and is driven by a hydraulic ram that is capable of producing either periodic or random motion. The paddle of the wavemaker moves according to a prescribed sinusoidal motion as given by, ) 2 ( t f Sin S S w o π = (1) Copyright ASCE 2005 EWRI 2005 3 Where So is the paddle stroke that ranges from 0 to 30.48 cm (half the total distance it travels).

Acoustic doppler technique is widely used in both fields and laboratory facilities to compute the mean water velocity and to characterize the turbulence of a flow. In general they provide the three dimensional components of flow velocity in a measurement volume in the water body with fairly good spatial and temporal resolution for engineering applications. The most sophisticated devices can even gauge a velocity profile measuring the water velocity in several measurement volumes along a line. However, these devices are semi int rusive which might have, depending on the experimental setup, substantial consequences in the measurements obtained due the flow perturbation created by the probe. The goal of this paper is to explore experimentally and numerically the wake effect of the p robe on the measurement volume in order to validate the measurements provided by this kind of instruments or incorporate some corrections if needed. A computational fluid dynamic (CFD) model is used to simulate an open channel flow where the model was validated with previous experimental results. In the other hand, the laboratory measurements were conducted in an open channel flume located in the Ven Te Chow Hydrosystems Laboratory of the University of Illinois. The measurements were done using particle image velocimetry technique (PIV) producing two dimensional velocity fields around the acoustic probe measurement volume with and without the presence of the probe. The numerical and experimental ranges of Reynolds numbers (Re) tested were 3x10 6 to 1x10 7 and 1x10 4 to 5x10 4 respectively. Non dimensional contour plots showing the difference between the flow velocity and turbulent quantities with and without the probe are built. Both results show that the errors are less than 10 percent around the probe. This methodology is still under development, however it provides more insight for experimental setups and it could be applied to other acoustic doppler instruments such as the ADV (Acoustic Doppler Velocimeter) and ADCP (Acoustic Doppler Current Profiler) among others.

The Acoustic Doppler Velocimeter (ADV) signals are affected by Doppler noise which is intrinsic to the Doppler measurement technique. It has the c haracteristics of white noise and its integral effects must be subtracted from some turbulence parameters. New tools are introduced in this paper to evaluate the relative importance of the noise energy on the total energy as well as to define the characteristic frequency in the measured energy spectrum where noise energy is more important than turbulent energy (flat plateau). To develop these tools a model for the power spectrum is adopted which allows the analysis of a range of flow conditions. Results sho w that noise energy can have an important contribution on the total measured energy, mainly in low energy flows. However in those cases, the noise energy level can be defined from the spectrum because the characteristic frequency is smaller than the Nyquist frequency. After the noise energy level is defined, corrections to the rest of the turbulent parameters (length and time scale, convective velocity, etc) must be performed.

This paper presents experimental evidence regarding the behavior of bubble plumes in two tanks of different size, under non -stratified conditions. The smaller vessel has been geometrically scaled down from the larger one with a relation 1:10. Velocity measurements were performed in both tanks with acoustic sensors (ADVs) and timeaveraged velocity profiles obtained at both scales were compared. Th is comparison was used to support a methodology to scale vertical and horizontal (radial) distances in bubble plumes, while allowing for the simulation of portions of the reservoirs . The bubble-slip velocity and a length scale D were determined as the relevant scales in the analysis. Previous scaling of bubble plumes, based on the preservation of the number H M (Asaeda and Imberger, 1993) and the use of the ratio diffuser

This paper presents laboratory experiments on pool-riffle sequences designed to provide 3D velocity data of high-resolution -in space and time- for different flow conditions, in order to analyze the implications for the physical habitat in low-gradient streams. Two different configurations were studied. The first one has the pools located on the channel centerline, in an effort to minimize the possibility of scour near the banks. This design is suitable for restoring streams in heavily urbanized areas, where the channel planform alignment is constrained by the existing infrastructure and bank erosion is unacceptable. The second configuration is more representative of natural pool-riffle sequences, with alternated pools located close to the banks. Both configurations where compared with data on flat bed uniform flow.

Streamflow-rating curves showing the relation between water-surface stage and the flow discharge have been a widely used tool in hydrology for over a century. Despite their wide- spread application, several problems with stage-discharge ratings have been recognized, resulting in development of many empirical methods to adjust or shift the rating to improve the agreement between ratings and measurements. Among these are methods to account for looped ratings during unsteady flow, stage-slope-discharge ratings to account for variable downstream backwater conditions, and shifts to account for changes to the "control" for the rating. Although these methods have been commonly applied to compute discharge records for streamflow- gauging stations for over half a century, they have achieved only a limited degree of success because of simplifying assumptions on the flow hydrodynamics. Most of these methods are not widely known or understood, other than by those actively applying them to streamflow gauging stations. Furthermore, the underlying physics and scientific justification for these methods has not been examined. Examination of the simplifying assumptions that these methods apply to the momentum and continuity equations clearly illustrates the reasons for the limited success of these methods. In this presentation, methods to shift or adjust stage-discharge ratings are described from the viewpoint of the fundamental hydrodynamics of unsteady nonuniform flow. The simplifying assumptions inherent in these methods are presented and conditions for which the error introduced by these assumptions becomes significant are discussed. Introduction: Accurate data describing the rate of flow of water (discharge) are used for many purposes, including operational decision making, input for hydraulic and hydrologic models, records for litigation about water rights or damages, calculation of "loads" and transport of sediment and other water-quality constituents, and for design of water-control and conveyance structures. Because of the dynamic nature of hydrologic systems, the information typically needed for most hydrologic analyses is a time-series record of the discharges. However, direct measurement of discharge in open channels is time consuming and costly. Therefore, most discharge records for streamflow-gauging stations are developed using a calibrated stage-discharge rating to estimate the discharge from the measured water stages, which permits a fast and relatively inexpensive means to determine the discharge (Rantz et al., 1982). Rating curves are established by concurrent measurements of stage, y and discharge, Q and the results are fitted graphically or statistically to yield the rating curves. The stage-discharge rating has been described as "the most important part of a velocity-area current-meter station" (Herschy, 1999).

Sand ripples develop spontaneously in an oscillatory flow over a movable sediment bed. The mechanics of sediment suspension in the presence of ripples is complex and its direct observation is complicated unless a technique can be used to capture the flow field and particle motion above and around the ripples. This work presents the results of an exploratory study conducted in a U-tube. The goal of the study was to use Particle-Image-Velocimetry (PIV) to capture the interaction between turbulent flow structures, suspended particles, and ripples and other bed instabilities. The PIV technique was chosen because of its potential to simultaneously determine the fluid velocity and the solid-particle velocity fields. Exploratory measurements indicate that the mechanisms responsible for the resuspension of bed particles in the presence of ripples are more complicated than anticipated. As water flows past each ripple, separation takes place at the crest of the ripple. Vortical structures generated downstream of the crest entrain sediment particles into the flow. When the flow reverses direction, each structure, along with the sediment it has suspended, is carried away from the ripples and into the outer flow field. As the structure dissipates, the sediment suspended in it is released. The PIV techniques implemented in this study provide information about velocity, vorticity, and turbulence distributions, helping to explain this complex flow field.

This paper presents a study whose purpose is to help in the understanding of the characteristics of the flow through and downstream of a series of abrupt 3D contractions/expansions, seeing them more from the fluid mechanics point of view, rather than from the hydraulic perspective. These contractions/expansions comprise cross-sectional area changes in plan and side views in an open channel. An existing model, built to optimize the design of canoe chutes, was considered as suitable for this endeavor. The device included up to five “drop” structures, and flow variables were observed in one of them. Measurements of the three-dimensional velocity field and of the geometry of the free surface were performed. This paper describes and analyzes those measurements, as well as the feasibility of using acoustic sensors for measuring the location of the free surface.

This paper presents an analysis of measurements of mean flow and turbulence statistics in bubble plumes conducted in a large experimental tank (digester) at a wastewater treatment plant. Profiles of dissipation rates of turbulent kinetic energy are presented for the first time, together with distributions for the turbulent kinetic energy and Kolmogorov length scales. Dissipation rates obtained from time velocity series and SCAMP measurements are also compared.

Channelization limits the geomorphological and biological diversity of many urban streams. Whenever the existing infrastructure prevents re-alignment of the channel planform, in-channel structures of the pool-riffle type offer an alternative means to provide some degree of variability in the flow pattern. This paper presents mean flow and turbulence measurements obtained on a physical model of pool-riffle structures designed to restore low gradient streams in heavily urbanized areas. The data collected include high-resolution 3D velocities as well as water surface elevations for different flow conditions. The results show that the flow is highly threedimensional, and that the effect of the structures is more important for low flow conditions. Also, flow patterns resemble that of natural pool-riffle sequences. Implications for sediment transport, bed and bank morphology and aquatic habitat are analyzed.

This paper presents an exploratory study of flow-particle interaction in a small water tunnel. Images are recorded following the Particle Image Velocimetry technique. The frames are analyzed in order to get information on flow turbulence and particles carried by the flow. The turbulence of the flow is considered in terms of the coherent structures that developed essentially in the wall region. The methods investigated allow the detection and quantitative description of these structures. Concerning the solid phase, two kinds of methods were considered: one to locate particles on the frames, and the other to track the particles. The methods are tested with simple experiments performed in a small water tunnel. Results concerning the fluid and solid phases are analyzed together. They show two kinds of particle behavior: particles that travel following coherent structures and particles that do not follow any particular turbulent structure.

Bedforms often are present on the bed of alluvial sand-bed rivers. Bedforms, such as dunes, impact the flow field. In this field st udy, velocity and suspended-sediment concentration measurements were made longitudinally along a dune field in large (5-15 meters deep) alluvial sand-bed rivers. The velocity and suspended-sediment concentration data was collected using an acoustic Doppler current profiler, acoustic Doppler velocimeters, an optical backscatter sensor, and two sediment intakes. This paper presents a description of these measurement devices and techniques for the collection of this data. Some preliminary results observed at the Missouri River at St. Charles, Missouri are presented.

A canoe chute is a series of rapids and pools creating a gradual descent from the elevation of the upstream pool of the dam to the elevation of the pool at the toe of the dam. Each rapid forces a surface jet that causes a hydraulic jump when it enters the slower water of a pool. Most engineering designs have considered the hydraulic jumps formed in canoe chutes to be approximately the same as the hydraulic jumps formed at abrupt drops in the channel bottom. The jumps commonly observed at abrupt drops are A-Jumps formed at high tailwater conditions, waves formed at intermediate tailwater conditions, and B-Jumps formed at low tailwater conditions. Sets of equations have been developed by different authors to describe the A- and B-Jump types that occur at abrupt drops. In a canoe chute, however, there is also a simultaneous horizontal expansion in the channel in addition to an abrupt drop in the channel bottom. Thus, the momentum equations that describe two-dimensional flows at abrupt drops need to be modified to account for the three-dimensional flow caused by the additional horizontal expansion. A 1:7 scale Froude model of one rapid of the canoe chute was constructed in the Ven Te Chow Hydrosystems Laboratory at the University of Illinois. Depth and flow data collected from the physical model were compared against both the original and the modified momentum equations. An empirical method for predicting hydraulic jump behavior was developed. The empirical method is advantageous in that it involves either known or easily measured flow conditions.

Dimensional analysis and numerical modeling are combined to obtain a simple expression for estimating the capacity of vegetated open channels to transport suspended sediment under equilibrium conditions. The numerical model consists of a two-equation closure scheme of the k-s type, with parameters calibrated using laboratory observations in an open channel with simulated vegetation. A simple power-type expression is found to provide a very good collapse of all the experimental data involving the Rouse number, the relative submergence, the particle Reynolds number and the dimensionless plant density as independent variables.