Journal of Hydraulic Engineering

Understanding the complex flow and sediment transport on vegetated slopes is important for ecological restoration and conservation projects. This study quantifies the erodibility of sand infill through densely vegetated engineered turf on steep slopes. Flume testing was conducted on four different sand infill materials. The initially lain bed material had artificially high mobility due to the infill application method. Grains were elevated by the vegetation and protruded into the flow. Then, the bed material gradation during subsequent flows became progressively coarser. Two regimes were identified. Poorly sorted infill soils underwent noticeable changes to gradation and had decreasing mobility with increasing shear stress. Conversely, well-sorted soils had minimal changes to gradation and resulted in the expected trend of increasing sediment flux with increasing shear stress. Existing predictive formulas performed poorly, in particular for the soils with evolving gradation. An updated formulation to predict sediment flux is proposed based on a reduction to the effective bed shear stress and dimensionless parameters relating to the flow, sediment, and vegetation characteristics. The proposed modification results in greatly improved predictions for both sediment flux magnitude and trend.

Vertically assembled ring meshes serve as barriers against explosive threats, in particular when overflowing water completely covers the mesh. The author measured the flow velocity over these structures using Surface Structure Image Velocimetry and subsequently determined the water layer thickness by taking into account discharges in the range $1.0\mathrm{L}/\mathrm{s}\le Q\le 4.5\mathrm{L}/\mathrm{s}$. The water proceeds through and over the mesh and forms surface surges at lower discharges. The surges disappear for higher discharges and induce plain water curtains. Based on a momentum balance equation, a theoretical approach was derived to describe the flow dynamics. The free parameters, e.g., the surface roughness of the metal rings and the deflection angle at the rings, were analyzed and compared with the experimental data. The main finding of this study was that the flow velocity remained constant at $w\approx 0.54\mathrm{m}/\mathrm{s}$, whereas the water thickness increased linearly between 1.0 and 4.6 mm with increasing discharge. As a consequence, ring meshes should be supplied with the highest possible discharge to achieve the greatest mitigating effect against blast wave threats.

This paper presents observations on clear-water and live-bed contraction scour caused by subcritical flow along a large rectangular channel. Three contraction ratios (contraction width/approach–channel width) were used: 0.25, 0.50, and 0.75. Each ratio included a 45° transition linking the contraction to the approach channel. Contractions scour relates to three categories of contraction length: length shorter than flow-separation length at contraction entrance, length exceeds flow-separation length, and length is sufficiently long to develop uniform flow in contraction. Flow-choking was avoided. The experiments focused on the second category, herein termed intermediate-length contractions. Light detection and ranging (LiDAR) scans showed that maximum scour depths occurred at a flow vena contracta (formed within the contraction entrance), the entrance corners, and the contraction exit. The observed sour depth in the vena contracta exceeded the depths estimated using the existing HEC-18 equations for contraction-scour. The deepest scour occurred at entrance corners except for the smallest ratio, which produced a step scour.

Coanda-effect screens exclude coarse and fine debris from a variety of water intakes. Water overflows an inclined wedge-wire screen with tilted wires that shear high velocity flow from the bottom of the water column. The screens hydraulically self-clean, making them ideal for remote, nonpowered sites. Flow conditions vary widely over the length of most screens. Previous testing related flow capacity to gravitational, surface tension, and viscous forces, but the range of flow conditions was limited versus potential applications. This study tested small sections of prototype-scale screens at varying slopes, and discharge coefficients were related to Froude and Weber numbers. Tests with variable water temperatures proved that screen performance is independent of Reynolds number and viscosity, but depends strongly on surface tension. Several screen geometries (i.e., wire size, shape, and slot size) were tested, and the performance of all screens could be modeled with power curve functions of the Weber number modified by the Froude number. Individual screens exhibited some unique performance characteristics, but 10 of the 13 screens could be modeled effectively as a group.

Tsunamis are among the most destructive natural disasters. Recent major tsunamis in Indonesia (2004), Chile (2010), and Japan (2011) resulted in significant loss of human lives and damage to coastal structures. Damages to lifeline infrastructure caused by these disasters have highlighted the need for much more attention from the engineering community to the investigation of tsunami interactions with coastal bridges. Therefore, developing resilient infrastructure that can withstand and remain operational against tsunami bores will significantly improve the postdisaster recovery of the affected areas. In this study, a series of experiments have been conducted in a 15 m long, 1.2 m wide, and 1.2 m deep wave flume equipped with an automatic gate to generate a tsunami bore in order to quantify tsunami-induced loads on a deck girder section bridge. The results of the experiments carried out with a bridge model to investigate the effects of the bridge deck skewness on the tsunami wave-induced forces and moments are presented. The bore height, bore velocity, resulting forces, and moments were measured. It was found that the skewed bridge deck is subjected to additional force and moment components, namely the lateral force ($F_y$) and the rolling and yawing moments ($M_x$ and $M_z$). These components are nonexistent for the unskewed bridge deck. Based on the experimental results, equations were proposed for estimating the tsunami horizontal, lateral, and uplift forces for a deck girder section bridge.

Marine outfalls discharge wastewater on the inner shelf and are designed to encourage rapid effluent mixing sufficient to maintain a submerged wastefield. A high-resolution nonhydrostatic Regional Ocean Modeling System (ROMS) model was used to resolve concomitantly the intermediate- and far-field submarine plume development. ROMS simulations were validated with cross-flow laboratory experiments. Generally, results showed that the nonhydrostatic high-resolution ROMS is capable of resolving plume dynamics in typical cross-flow conditions. Top-of-plume elevation was quantified and found to be highly variable. The ROMS model is relatively insensitive to changes in horizontal effluent input parameterization. Multiple grid resolutions were tested, and good model–data agreement was achieved in low to medium cross-flow experiments. Additional resolution improved high cross-flow results. This intermediate- and far-field three-dimensional nonhydrostatic model resolves plume development over multiple spatiotemporal scales and can include natural oceanic processes currently absent in many plume models. Integrated outfall plume and marine process modeling will advance future wastewater management.

A drag reduction method by polymer additives was tested for the first time in a large scale open-channel watercourse. Ten and a half tons of a water soluble polymer were injected during 15 consecutive hours in the upstream section of an irrigation canal in steady state, leading to a 20 ppm concentration of polymer in the water. The evolution of the water depth was measured every 10 min for 18 h along ten sections further downstream, up to a distance of 26.3 km from the injection section. The water depth at all sections remained constant until the arrival of the polymer, at which time it strongly decreased, sometimes with a slight water-depth increase beforehand; the depth then remained constant as long as the polymer injection remained. A maximum water depth reduction of 26 cm (i.e., 17%) was measured at the first cross section (2 km downstream from injection). The water depth reduction decreased to 10% and 3% at 10 and 20 km downstream from the injection, respectively. However, further downstream, at a distance of 26.3 km, the water depth increased by 5%. This paper also discusses the environmental impacts of polymer injection through analysis of samples taken from the water and bed material before and during the experiments.

The validation of numerical models for large lakes is difficult because of sparse field observations. In this study, a Froude-Rossby scaled physical model of Lake Ontario, North America, is used to support numerical simulations. Experimental data are consistent with available field observations and provide a more comprehensive view of lake-wide features that include, in the absence of wind, strong eastward flows along both northern and southern shorelines, a large cyclonic gyre in the Rochester basin, and smaller midlake cyclonic eddies. With a west wind (most common direction), a well-defined westward flow in the middle of the lake separates an anticyclonic gyre in the north from a cyclonic gyre in the south. A review of numerical models shows that most models can capture general features of these observed patterns but do not always reproduce all details, especially in nearshore regions. A numerical model based on the Environmental Fluid Dynamics Code (EFDC), with a 200-m resolution in nearshore regions, is developed.

Bubbly Creek is the historical name given to the West Fork of the South Branch of the Chicago River (SBCR). Even though its base flow is small, during extreme storm events Bubbly Creek becomes an important tributary to the Chicago Area Waterway System (CAWS). During extreme storm events, combined sewer overflows (CSOs) discharged by the Racine Avenue pumping station (RAPS), located at the head of the creek, can result in large flow velocities, potentially entraining into suspension bottom sediments, which contain abundant organic muck and buried waste. Under normal storm flow conditions, the flow discharge from Bubbly Creek flows first into the SBCR and then is conveyed by the Chicago Sanitary and Ship Canal (CSSC) towards Lockport, Illinois. However, during extreme rainfall events the conveyance capacity of the CSSC is exceeded, so there is a flow reversal, and Bubbly Creek water and sediments flow north, along the SBCR and then towards Lake Michigan via the Chicago River controlling works (CRCW). Due to lack of field observations during storms, the entrainment, transport, and fate of sediments from Bubbly Creek during reversed-flow conditions, cannot be easily assessed. This motivated the use of numerical modeling to evaluate the erosion, transport, and deposition of sediments from Bubbly Creek on the CAWS. The public-domain three-dimesional (3D) environmental fluid dynamics code (EFDC) was used to simulate hydrodynamics and sediment transport for two storm events with normal and reversed flow directions and high CSO discharge. Results show that RAPS discharge picks up sediment from Bubbly Creek, causing high-suspended sediment concentrations due to high rates of bottom material resuspension. In the September 2008 storm, approximately 8% the sediment reached CRCW and went into Lake Michigan during flow reversal, while 83% of the sediment went south along the CSSC towards Lockport, Illinois. Herein, the novelty is in shedding light on applying a 3D cohesive sediment module to evaluate the erosion, transport, and fate of organic muck and cohesive sediments originating in Bubbly Creek along the CAWS. The flow and sediment partitioning, bed morphology, and its potential impact on the system could be analyzed under normal and reversed flow conditions for both recently deposited as well as legacy sediments accumulating since RAPS went into operation almost a century ago. Capping of legacy sediments together with periodic dredging of sediments deposited after a CSO event could be an alternative worthwhile considering for urban streams like Bubbly Creek, where flow only takes place after extreme rainfall events.

The aim of this technical note is to present methods that allow for direct computation of the bed roughness due to sediment transport based on a formula developed in the literature for cases involving current or waves separately. The methods result in approximate nondimensional expressions for the exact solutions in terms of polynomials determined by least-square fits, where the accuracy of the polynomials is high. Using the present methods may significantly reduce calculation times of roughness due to sediment transport in numerical models of morphological change.

Dam operators often do not know whether an auxiliary spillway will fail until it is loaded, which can be infrequent. Such failures have the potential to result in overall dam failure, leading to loss of life and substantial property damage. The purpose of this paper is to develop a screening technique to identify potentially risky auxiliary spillways. The paper uses the National Inventory of Dams (NID) data and analyzes a sample of 400 earthen dams with auxiliary spillways. The main innovation of the paper is to employ code to create multiple input files and analyze them in the Windows Dam Analysis Modules (WinDAM) C software. This technique is more efficient than the current functionality of WinDAM C, which evaluates one dam at a time. The proposed method serves as a quick screening and decision-making tool for multiple embankments for extreme flooding events by identifying potentially risky auxiliary spillways that may require in-depth analysis. The results of this screening found 75% of spillways are likely to sustain heavy damage. Additionally, heavy damage was related to narrower spillway widths.

There exist many bed-load functions in the literature to calculate bed-load transport rates, but none of them fit data from low to high shear stress conditions. This research presents a generalized bed-load function based on empirical data. Specifically, the classic power law in high shear stress conditions is extended to low shear stress conditions by applying a complimentary error function (or logistic function) and using Coles’ mathematical idea for the wake law in turbulent boundary layer velocity distribution. The resulting generalized bed-load function agrees well with the classic data sets; it reduces to Huang’s $5/3$ power law in the very low and the high shear stress conditions, and it is numerically close to Paintal’s 16th power law in the transitional regime. It is found that the maximum turbulence-induced lift force and the minimum critical shear stress in the Shields diagram correspond to the inflection point (in terms of logarithmic scale) in the Einstein bed-load diagram, resulting in the most efficient bed-load transport rate. After that, this paper discusses the effects of turbulence-induced lift force, critical shear stress, viscosity, nonlinearity, and uncertainty on bed-load transport. Finally, an example with uncertainty analysis is illustrated for applications.