River Training Structures Research Articles

Theoretical Analysis of Wing Dike Impact on River Flood Stages

The question of whether wing dikes (bank-perpendicular river training structures or groynes) cause higher flood levels has been debated in the United States for many years. Some researchers point to empirical data that show large stage increases which are associated with wing dike construction, whereas other researchers have suggested that such increases are contrary to engineering theory. In a recent report, the U.S. Government Accountability Office (USGAO) presented this question as a priority to be resolved by engineers and scientists. As a first step to better understand the connection between navigation structures and flood levels on the Middle Mississippi River (MMR), a simplified theoretical analysis is presented to test the assertion (made in the USGAO report and elsewhere) that such increases are contrary to hydraulic theory. This analysis predicts that wing dike construction may lead to water level lowering for in-bank flows and to water level increases for out-of-bank (flood) flows. This confirms that, in principle, wing dikes may have contributed to the observed flood water level trends in the MMR. More detailed follow-up studies are required to accurately quantify the impact of wing dikes on flood levels. DOI: 10.1061/(ASCE)HY.1943-7900.0000698. © 2013 American Society of Civil Engineers.

Laboratory analysis of the hydrogeological behaviour of rock loose structures on pervious beds

Large flow interchanges occur between free surface and subsurface flows of river training structures, such as in rock loose chutes based on pervious beds. The filtering action of the base pervious layer can improve the water quality but, at the mean time, reduce the minimum vital flow discharge. This paper, hence, aims to analyse the flow interchanges between the base material and the surface flow in presence of rock loose river structures (block ramps or rock chutes). Tests have been carried out in macro-roughness conditions for slopes ranging from 0.125 to 0.25. Different seepage inlet and outlet conditions have been tested in order to asses their influence on the maximum seepage capacity of both stilling basin and ramp base material. Finally, the effect of the seepage on the energy dissipation which occurs along the ramp has been studied.

Environmental engineering of navigation infrastructure: A survey of existing practices, challenges, and potential opportunities

Navigation infrastructure such as channels, jetties, river training structures, and lock-and-dam facilities are primary components of a safe and efficient water transportation system. Planning for such infrastructure has until recently involved efforts to minimize impacts on the environment through a standardized environmental assessment process. More recently, consistent with environmental sustainability concepts, planners have begun to consider how such projects can also be constructed with environmental enhancements. This study examined the existing institutional conditions within the US Army Corps of Engineers and cooperating federal agencies relative to incorporating environmental enhancements into navigation infrastructure projects. The study sought to (1) investigate institutional attitudes towards the environmental enhancement of navigation infrastructure (EENI) concept, (2) identify potential impediments to implementation and solutions to such impediments, (3) identify existing navigation projects designed with the express intent of enhancing environmental benefit in addition to the primary project purpose, (4) identify innovative ideas for increasing environmental benefits for navigation projects, (5) identify needs for additional technical information or research, and (6) identify laws, regulations, and policies that both support and hinder such design features. The principal investigation tool was an Internet-based survey with 53 questions. The survey captured a wide range of perspectives on the EENI concept including ideas, concerns, research needs, and relevant laws and policies. Study recommendations included further promotion of the concept of EENI to planners and designers, documentation of existing projects, initiation of pilot studies on some of the innovative ideas provided through the survey, and development of national goals and interagency agreements to facilitate implementation.

Hydraulic analysis of river training cross-vanes as part of post-restoration monitoring

Abstract. River restoration design methods are incrementally improved by studying and learning from monitoring data in previous projects. In this paper we report post-restoration monitoring data and simulation analysis for a Natural Channel Design (NCD) restoration project along 1600 m of the Batavia Kill (14 km2 watershed) in the Catskill Mountains, NY. The restoration project was completed in 2002 with goals to reduce bank erosion and determine the efficacy of NCD approaches for restoring headwater streams in the Catskill Mountains, NY. The NCD approach used a reference-reach to determine channel form, empirical relations between the project site and reference site bankfull dimensions to size channel geometry, and hydraulic and sediment computations based on a bankfull (1.3 yr return interval) discharge to test channel capacity and sediment stability. The NCD project included 12 cross-vanes and 48 j-hook vanes as river training structures along 19 meander bends to protect against bank erosion and maintain scour pools for fish habitat. Monitoring data collected from 2002 to 2004 were used to identify aggradation of pools in meander bends and below some structures. Aggradation in pools was attributed to the meandering riffle-pool channel trending toward step-pool morphology and cross-vane arms not concentrating flow in the center of the channel. The aggradation subsequently caused flow splitting and 4 partial point bar avulsions during a spring 2005 flood with a 25-yr return interval. Processing the pre-flood monitoring data with hydraulic analysis software provided clues the reach was unstable and preventative maintenance was needed. River restoration and monitoring teams should be trained in robust hydraulic analytical methods that help them extend project restoration goals and structure stability.

Generation of synthetic seasonal hydrographs for a large river basin

Summary This paper describes a methodology for the generation of synthetic seasonal stage hydrographs with a number of flood waves for a large braided river basin based on statistical analysis of the historical stage records. The synthetic seasonal hydrographs in a river is required for different purposes such as assessing the hydraulic performances of various river training structures, morphological predictions, environmental impact analysis. The typical stage hydrograph of such a river has two components: flood waves and seasonal (monsoonal) response. Using historical stage records, flood waves in a seasonal stage record were identified and their characteristics were approximated using Maxwell distribution. The extracted characteristics of flood waves such as time of occurrence and successive flood lifts were analysed with various probability distribution function to find out their best distribution. The frequency analysis of the annual maximum flood lift was carried out. Beside this, seasonal responses were also approximated using Maxwell distribution. A relationship between the seasonal lift and total monsoonal rainfall was established. For a given total seasonal rainfall and return period of annual maximum flood wave lift, synthetic seasonal hydrograph is generated by superimposing both seasonal response and flood waves. The generated hydrographs are evaluated by comparing the cumulative frequency function of river stage and relative frequency of daily stage changes (rise/fall) for three seasons with different flood wave return periods, at two river gauging stations for the river Brahmaputra, India.

Causes for the decline of suspended‐sediment discharge in the Mississippi River system, 1940–2007

AbstractBefore 1900, the Missouri–Mississippi River system transported an estimated 400 million metric tons per year of sediment from the interior of the United States to coastal Louisiana. During the last two decades (1987–2006), this transport has averaged 145 million metric tons per year. The cause for this substantial decrease in sediment has been attributed to the trapping characteristics of dams constructed on the muddy part of the Missouri River during the 1950s. However, reexamination of more than 60 years of water‐ and sediment‐discharge data indicates that the dams alone are not the sole cause. These dams trap about 100–150 million metric tons per year, which represent about half the decrease in sediment discharge near the mouth of the Mississippi. Changes in relations between water discharge and suspended‐sediment concentration suggest that the Missouri–Mississippi has been transformed from a transport‐limited to a supply‐limited system. Thus, other engineering activities such as meander cutoffs, river‐training structures, and bank revetments as well as soil erosion controls have trapped sediment, eliminated sediment sources, or protected sediment that was once available for transport episodically throughout the year. Removing major engineering structures such as dams probably would not restore sediment discharges to pre‐1900 state, mainly because of the numerous smaller engineering structures and other soil‐retention works throughout the Missouri–Mississippi system. Published in 2009 by John Wiley & Sons, Ltd.

Two-dimensional depth-averaged model simulation of suspended sediment concentration distribution in a groyne field

Summary River-training structures, such as spur dikes, are effective engineered methods used to protect banks and improve aquatic habitat. This paper reports the development and application of a two-dimensional depth-averaged hydrodynamic model to simulate suspended sediment concentration distribution in a groyne field. The governing equations of flow hydrodynamic model are depth-averaged two-dimensional Reynold’s averaged momentum equations and continuity equation in which the density of sediment laden-flow varies with the concentration of suspended sediment. The depth-averaged two-dimensional convection and diffusion equation was solved to obtain the depth-averaged suspended sediment concentration. The source term is the difference between suspended sediment entrainment and deposition from bed surface. One laboratory experiment was chosen to verify the simulated flow field around a groyne, and the other to verify the suspended sediment concentration distribution in a meandering channel. Then, the model utility was demonstrated in a field case study focusing on the confluence of the Kankakee and Iroquois Rivers in Illinois, United States, to simulate the distribution of suspended sediment concentration around spur dikes. Results demonstrated that the depth-averaged, two-dimensional model can approximately simulate the flow hydrodynamic field and concentration of suspended sediment. Spur dikes can be used to effectively relocate suspended sediment in alluvial channels.

European Practice for Bridge Scour and Stream Instability Countermeasures

FHWA, AASHTO, and TRB sponsored a scanning review of European practice for bridge scour and stream instability countermeasures in October 1998. The review involved a panel of representatives from six state highway agencies (California, Illinois, Maryland, Minnesota, Oregon, and South Carolina), FHWA, two universities, and the private sector. The review included visits to hydraulic research laboratories, highway research institutes, and field sites in four countries—Switzerland, Germany, the Netherlands, and the United Kingdom. Findings during the scanning review can be classified as general observations and observations of specific countermeasures. General observations of European practice include design philosophy, risk analysis, environmental policy, river geomorphology, scour prediction, modeling, and inspection and monitoring. Observations of specific countermeasures include riprap design and construction, filter design and construction, river-training structures, riverbed degradation countermeasures, bioengineering, and flow-altering devices. These observations are contrasted with U.S. practice. The panel’s recommendations for modifying U.S. practice on the basis of the European experience and findings that deserve further evaluation are also presented.

FAILURES OF RIVER TRAINING MEASURES

ABSTRACT Guide bunds, sloping revetments, spurs, cut-offs, flush bunds, bottom panels, studs etc. are generally used as river training works. These structures if designed properly, may become very effective both functionally and structurally. If they are not located or oriented properly and/or designed appropriately, they may fail functionally. These river training structures would also require some maintenance. Launching aprons if laid at higher levels may act as side berms and under certain conditions may get undermined due to progressive scour at the toe of the structure, which ultimately would lead to structural failure. Similarly, if proper filter is not provided below the launching apron, it may sink down due to removal of soil particles through the voids at the toe thereby leading to failure of the structure.

Habitat rehabilitation on the upper Mississippi River

AbstractUpper Mississippi River ecological integrity has been severely compromised by human activity during the last 50 years. In response to the continuing decline of natural resource values, two approaches for protecting and improving the Upper Mississippi River‐floodplain ecosystem have been used. Habitat rehabilitation and enhancement projects are being constructed at 54 locations to provide site‐specific rehabilitation. The projects are designed to counteract the adverse ecological effects of sedimentation through (1) flow introductions, (2) the isolation of backwaters; and (3) flow diversions and wave breaks. Channel maintenance projects are being re‐evaluated in an attempt to construct or modify existing river training structures that are environmentally sympathetic. The latter approach works with the river's energy, whereas the former attempts to overcome riverine processes. Both approaches have significant limitations because they affect limited areas. A proposal is presented that restores some ecosystem integrity by re‐establishing occasional low river stages that occurred before the implementation of the Upper Mississippi River Navigation System.

Performance of alternative methods of bank protection

The durability of several common bank protection methods used as less expensive or environmentally acceptable alternatives to toe-trenched angular rock riprap has been documented during the 1980s at seven typical bank erosion sites in British Columbia. Since the sites were uncontrolled examples of actual river training works in operation, natural events hindered a precise comparison of each scheme with toe-trenched angular rock riprap protection. However, of the four alternatives investigated – gravel dykes, tree revetments, riprap with toe apron, and semi-round riprap – all but semi-round riprap performed less than satisfactorily over the years of observation. Documentation of performance is sufficient to conclude that on steep gravel-bed rivers, gravel dykes do not endure; tree revetments require constant maintenance and will not endure large floods, unless extremely well-constructed; toe aprons are not as reliable as toe trenches for the same volume of rock; and well-placed, large semi-round rock performs well under moderately severe attack. Key words: erosion, bank protection, channel stability, river training structures, gravel-bed.

Development of Bottom Panels in River Training

Two new specific projects show the development of the panels as permanent river training structures. New information and references concerning 6 yr. of progress in theory, scale models and experiments in situ are presented herein. The works on the Loire River in France are linked with the cooling system of a nuclear power plant; on the Chao Phya River, the project deals with the improvement of navigation over a 100-km long reach. After 14 yrs. of experiments on large and wide waterways in Africa and Asia, followed by training works on medium wide reaches in France and Thailand, the scope of bottom panels on alluvial river with a gentle slope has been broadly investigated. This comparatively inexpensive method has been quite well controlled, however, the feasibility of panels must always be studied very carefully under new hydraulic and economic conditions.