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Design Methods and Guidelines for New Technology, Low Cost Bank Stabilization Features Also Used for River Restoration

Project ID: 8819
Principal Investigator: Drew Baird
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2008
Keywords: None

Research Question

* What are the engineering and hydraulic performance properties of new methods of bank stabilization in both a fixed bed bend model and a mobile bed flume?

Need and Benefit

New methods of bank stabilization such as bendway weirs, root wads, J-Hooks, engineered log jams, stone toe protection, and deformable bank lines are being used in lieu of traditional riprap revetments for their cost saving and habitat benefits. In addition to bank protection, numerous applications for these structures exist. For instance, bendway weirs and spur dikes are also used for reducing sediment deposits in front of fish screens, intake structures, and bypass structures. These types of structures are also used in river restoration actions because they create variable velocity and depth flow conditions. Rootwads and engineered log jams also create fish cover. Existing design methods rely upon anecdotal information, individual professional experience, or incomplete methods that do not account for the near bank flow processes. Thus, many of these structures have been constructed without knowledge of engineering performance properties and as a result fail to perform their intended purpose and/or require frequent expensive repairs.

Reclamation engineers designing or maintaining in-stream water delivery structures, protecting river side facilities, or performing river restoration with these structures lack design guidelines based upon predictable engineering and hydraulic performance criteria. Reclamation personnel are tasked with implementing these type of structures on many rivers throughout the Western United States, including, but not limited to, rivers found in the Rio Grande Basin, the Columbia and Snake River Basins, the Sacramento River Basin and the Lower Colorado.

To address the lack of reliable methods and standards the Albuquerque Area Office began a physical hydraulic model study in fiscal year (FY) 2001 at Colorado State University (CSU), to measure the engineering and hydraulic performance properties of these structures in both a fixed bed bend model and a mobile bed flume. From FY 2001 to the present, the physical model has been used to measure performance of these structures relative to channel hydraulic properties, structure geometry, and spacing. The laboratory work uniquely represents near bank flow processes for bendway weirs, spur dikes, and native material features. Native material features include rootwads and engineered log jams placed sequentially along the outside bankline of bends. After CSU began model testing, the U.S. Army Corps of Engineers (Corps) Engineering Research and Development Center approached Reclamation about teaming up to combine physical modeling, field investigations, documented experience throughout the U.S., and literature review to develop design guidelines based upon predictable engineering performance criteria. The Corps has an excellent set of design criteria and methods for traditional flood control riprap revetments, yet they recognized that current design methods have the same limitations given above and that design methods and criteria need to be developed for these new methods applicable to smaller, lower cost flood control and restoration projects (Meg Jonas, and David Biedenharn Research Hydraulic Engineers, Corps, Personal Communication, Engineering Research and Development Center, 2005, 2007).

The National Engineering and Design Center of the Natural Resources Conservation Service (NRCS) also recognizes the need and is also conducting field performance surveys. The NRCS also recognizes that current design methods are incomplete and inadequate, leading to failure of these structures and/or high maintenance costs (Jon Fripp, Personal Communication, NRCS, 2006, 2007). The design guidelines will utilize hydraulics from a one -dimensional (1D) model such as HEC-RAS, and be easy to use with low design costs. Additionally, a benefit of this research is that Reclamation engineers and managers will have design guidelines based upon documented and predictable engineering performance to provide bank stabilization and river restoration.

Contributing Partners

None

Research Products

Independent Peer Review

The following documents were reviewed by qualified Bureau of Reclamation employees. The findings were determined to be achieved using valid means.

Methodology for Predicting Maximum Velocity and Shear Stress in a Sinuous Channel with Bendway Weirs using 1-D HEC-RAS (interim, PDF, 3.6MB)
By Mr. Paul Sclafani
Report completed on July 09, 2010

Transverse features create two zones of flow. First a zone of high velocity and shear stress near the tip and channel center. Second a low velocity and shear zone near the bankline between structures. a 1-D HEC-RAS model was developed together with physical model data to predict the velocity and shear stress decrease along the bankline between structures and the higher velocity and shear stress zone at structure tips
Keywords: transverse features, velocity, shear stress, physical models

Methodology for Calculating Shear Stress in a Meandering Channel (interim, PDF, 7.5MB)
By Kyung-Seop Sin
Report completed on October 05, 2010

Shear stress in meandering channels is a key parameter to predict bank erosion and bend migration. Physical model studies conducted at CSU on a representative study reach of the Middle Rio Grande in New Mexico provide shear stress distribution in a meandering channel. Preston tube, and other methods of estimating shear stress were evalauted. Preston tube measurements were determined to most accuratly represent channel shear stress and to compare approach shear with max bank line shear
Keywords: meandering channel shear stress, preston tube, adv measurements

Bendway Weir Design-Rio Grande Physical Model (interim, PDF, 392KB)
By S. Michael Scurlock, Drew Baird, Dr. Amanda Cox and Dr. Christopher Thornton
Report completed on April 03, 2012

Bendway weirs are transverse instream structures designed to p[ass flow over the weir crest at annual mean flow level, disrupt secondary currents, improve navigation, and redirect flow from the outer bank of a bend toward the center of the channel. Weir design guidance primarily focuses on state parameters consisting of crest elevation, width, length, profile angle, plan form angle, and spacing ratio. Design recommendations are summarized and applied to the physical model for measurements.
Keywords: bendway weir design, physical models

Quantification of Shear Stress in a Meandering Native Topographic Channel Using A Physical Hydraulic Model (interim, PDF, 2.7MB)
By Michael Ursic, Dr. Christopher Thornton, Dr. Amanda Cox and Dr. Steven R. Abt
Report completed on July 09, 2012

Current guidelines for predicting increases in shear stress in open-channel bends were developed from prismatic cross section investigations. This study shows increased shear stress relative to approach flow conditions and maximum bank line shear stress resulting from planimetric and topographic geometric features. Results of the Preston tube, and medthods of estimating shear stress form the ADV are presented and a relationship representing downstream shear stress increases are presented.
Keywords: native bed topography shear stress, physical models, preston tube, adv

Preston Tube Calibration (interim, PDF, 10.4MB)
By Dr. Christopher Thornton, Dr. Amanda Cox and Mr. Paul Sclafani
Report completed on July 02, 2014

Erosion control and river restoration measures need to be designed knowing the shear stress of the flowing river channel. Direct measurement of shear stress is usually not practical. For laboratory situations Preston (1954) suggested that a pitot-static tube be used to measure velocity at the boundary. This velocity at the boundary is liniearly related to boundary shear stress (Preston, 1954). This report describes a series of physical model measurements to develop a linear correlation.
Keywords: boundary shear stress, preston tube, calibration

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Transverse instream structure analysis: Maximum and average velocity ratios within the prismatic channel (interim, PDF, 1.5MB)
By S. Michael Scurlock, Dr. Amanda Cox, Dr. Christopher Thornton and Dr. Steven R. Abt
Report completed on August 13, 2012

Physical model measurements were made of spur-dikes, vanes and submerged spur-dikes in a two bend sequence physical model representing hydraulic and channel conditions found on the Middle Rio Grande. A set of influential structure design parameters were identified, organized into dimensionless ratio's and arranged for regression analysis. A series of predictive equations describing the ratios of maximum velocity and bend averaged velocity for all structures types using multivariate regression.
Keywords: physical modeling, spur-dikes, vanes, bank line velocity reduction

Native-Topography Dataset Evaluation Summary (interim, PDF, 2.8MB)
By S. Michael Scurlock, Dr. Christopher Thornton, Dr. Amanda Cox and Dr. Steven R. Abt
Report completed on August 22, 2012

A native topography bed was constructed within the trapezoidal 2 bend physical 1:12 scale model of the representative bends on the Middle Rio Grande. Velocity and boundary shear-stress patters and distributiosn were measured, examined, and are presented in this report. Comparisons with other physical model studies reported in the literature were made. All previous reports on this physical model are summarized in this report.
Keywords: physical model, velocity, shear stress, transverse structures

Assessment of Equations for Predicting Flow Velocities Associated with Transverse Features using field data from the Bernalillo Site on the Middle Rio Grande (final, PDF, 2.3MB)
By Dr. Amanda Cox, S. Michael Scurlock, Dr. Christopher Thornton and Dr. Steven R. Abt
Report completed on August 22, 2012

Using physical model measurements equations were developed to predict the ratios of maximum or average flow velocities along a channel with installed transverse features to bseline (pre-structure installation) cross-sectional average velocities. Reclamation constructed a series of bendway weirs in 2007 to mitigate lateral channel migration at the Bernalillo Priority Site of the Middle Rio Grande. Velocity ratio's measured at the Bernailillo site were compared to the predictive equations.
Keywords: field velocity measurements, prototype comparison to laboratory, transverse structures

This information was last updated on September 18, 2014
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