Design Methods for In-Stream Flow Control Structures (2014)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

66 A P P E N D I X F In-stream structures, constructed of rock or wood in vari- ous configurations, are often used to limit lateral migration, reduce bank erosion, and create diverse aquatic habitat (Rad- spinner et al., 2010). In-stream structures can be classified in two fundamental categories: sills and single-arm structures (Figure F-1). Sills are structures that span the entire channel width, while single-arm structures extend from one bank into the channel without reaching the opposite bank. Single-arm structures can be further subdivided into deflector, redirec- tive, and retard types, depending on the function of each structure configuration (NRCS, 2007). Proper structure design and placement are necessary to avoid channel aggradation, local bed scour, and bank erosion, all of which can result in structure failure and cause signifi- cant harm to the stream and nearby property. Furthermore, failure of these structures will accelerate the adverse effects they were initially installed to prevent, such as lateral migra- tion and infrastructure endangerment (see Table F-1). Design approaches need to incorporate the unsteady, 3-D character of the flow in the vicinity of structures and the complex inter- actions of turbulence in the water column with streambed sediments. The design guidelines in the following sections were developed with the multi-pronged approach described in Chapter 2, combining information from a comprehensive literature review (Appendix A), practitioner survey (Appen- dix B), field case studies (Appendix C), physical experiments (Appendix D), and numerical simulations (Appendix E and Chapter 3). Figure F-2 lays out the general flowchart for using the following design guidelines. Structure type is selected based on project goals and channel characteristics (Tables F-2 and F-3). An appropriate angle of orientation is selected based on the site characteristics. A vector analysis is used to map out optimum structure location. Ideally, 2-D or 3-D modeling approaches, such as VSL3D, will be used to fur- ther refine the design of the structure layout and evaluate its performance for the specific site under consideration. One- dimensional models will not provide adequate information to evaluate structure layout and, therefore, are not suggested as a tool for in-stream structure design. Three major categories of structure failure mechanism were identified: flanking (circumvention combined with aggrada- tion), local scour (which can lead to rock displacement), and rock displacement (based on hydrodynamic forces, not local scour). The practitioner survey (Appendix B) also reported winnowing (or scour between rocks) as a significant failure mode. This failure mechanism, however, was not explicitly evaluated in NCHRP Project 24-33, although the effects of this process were likely in the field case studies (Appendix C). Table F-3 compiles the evaluation of the susceptibility of each structure type to these failure mechanisms. F.1 Determining the Length of Outer Bank Protection in Meandering Channels In meandering channels, the length of bank protection can be determined for approximately sinusoidal channels by determining the tangent points to the meander (Figure F-3) and identifying a point approximately one channel width (B) upstream and 1.5B downstream from these points, as pre- sented in U.S. Army Corps of Engineers (1991) and HEC 23 (Lagasse et al., 2009). F.2 Rock Vane Design Guidelines The term “rock vane” applies to single vane rock structures that extend out from a stream bank into the flow. These struc- tures gradually slope from the bank to the bed such that, even at low-flow conditions, the tip of the structure remains submerged (Radspinner et al., 2010). Rock vanes are installed with an upstream angle to minimize erosive flow patterns near the bank by diverting high-velocity flow away from the bank (Maryland Department of the Environment, 2000; Johnson et al., 2002a; see Figure F-4). Often, rock vanes and other in-stream rock Design Guidelines for In-Stream Flow Control Structures

67 Channel Characteristics Failure Structure Type Aspect Ratio Sinuosity Slope Reasons Modes Deflector Rock vane (RV) 7–33 n/a 0.003– 0.008 Not keyed properly; rock size and shape Lateral circumvention; winnowing; local scour; aggradation J-hook vane (JH) 8.8–36 1.1–1.5 0.003– 0.02 Not keyed properly; rock size and shape Lateral circumvention; winnowing; local scour; aggradation Bendway weir (BW) 8.6–33 1.3–1.5 <0.003 Footer size; build depth Local scour Sill Cross vane (CV or CVA) 7.3– 19.6 1.1–1.5 0.001– 0.03 Faulty installation; rock size and shape Lateral circumvention; winnowing; local scour; aggradation; displacement W-weir (WW) n/a n/a n/a Faulty installation; rock size and shape Lateral circumvention; winnowing; local scour; aggradation; displacement Table F-1. Reasons and modes of failure reported in the practitioner survey published in Radspinner et al. (2010). Figure F-1. Illustrations of typical single-arm deflector structure and typical sill rock structure (from Radspinner et al., 2010). structures are installed with a secondary goals of improving aquatic habitat by creating flow diversity through the forma- tion of scour pools (Rosgen, 2006). A series of vanes installed for bank protection is intended to move scour to the middle of the channel and enhance deposition along the bank (e.g., Johnson et al., 2001; Bhuiyan et al., 2010). Rock vanes and other in-stream rock structures can reduce or eliminate the need for bank armoring on unstable banks and can improve the effec- tiveness of other erosion protection measures such as vegeta- tion restoration (McCullah and Gray, 2005). Current guidelines for placement and spacing of rock vanes, however, are based primarily on practitioner experience (e.g., Maryland Depart- ment of the Environment, 2000; Doll et al., 2003; NRCS, 2007). The Maryland Department of the Environment’s Water Management Administration included design guidelines for rock vanes in the MWCG (Maryland Department of the

Figure F-2. Design flow process for the design and layout of in-stream flow control structures. Site Characteristics Project Goals Steep Streams Low Aspect Ratio (Low B/H) Tight Meanders (Low Rc/B) Fine Bed Material (Sand) Protect Bank Toe Redirect Flow (Thalweg) Scour Pool Habitat Minimize Lateral Channel Adjustments Grade Control RV o o o o o o – o – JH o o o o o o + o o BW – – – o + + – + – CV + o o o – o + – + CVA + – o – – o + – + WW + – o – – o + – + – Not appropriate o Moderately appropriate with design modifications + Well suited Table F-2. Recommendations for in-stream flow control structure selection based on site characteristics and project goals.

69 Susceptibility to Failure Mechanism Local Scour Flanking Rock Displacement RV o + o JH + o + BW + – – CV + o o CVA + o + WW + o + – Low risk o Moderate risk + High risk Table F-3. Evaluation of susceptibility to failure mechanisms for in-stream flow control structures. (a) (b) (c) (d) Figure F-3. Extent of protection required at a channel bend for three different channels: (a) general guidelines (from U.S. Army Corps of Engineers, 1991), (b) the SAFL Outdoor StreamLab (OSL) channel with no structures, (c) VSL-G, and (d) VSL-S. Blue and red zones are associated to the regions with significant scour and deposition, respectively. Environment, 2000). Included in this document is a summary of the uses of these structures in common restoration and stabilization practices. Within this summary, applications for which rock vanes are well suited (e.g., protecting bank toe, and redirecting flows), moderately well suited (e.g., provid- ing in-stream habitat), and not well suited (e.g., stabilizing bed and use in bedrock channels) are discussed. Based on the practitioner experience reported in the MWCG, caution should be used in steep stream reaches with gradients that exceed 3%. It is also important to note that the stream bank opposite the rock vane structures should be monitored closely after installation for any increase in erosion occurring due to the presence of the rock vane and its ability to direct flow away from the outer bank, towards the center of the channel, and, on occasion, negatively affecting the opposite bank. Several structures use the rock vane as the key component and modify it for various situations. All structures from the rock vane family can be subjected to failure by lateral cir- cumvention, winnowing, local scour, aggradation, and dis- placement (Johnson et al., 2002b). In addition to the MWCG (Maryland Department of the Environment, 2000), rock vane design guidelines can be found in the USDA NRCS Stream

70 Figure F-4. Typical rock vane installation (after Rosgen, 2006 and Radspinner et al., 2010). Restoration Design National Engineering Handbook, Part 654 (NRCS, 2007). Chapter 11 of this design manual, “Rosgen Geomorphic Channel Design,” focuses on the design guide- lines for cross vanes, J-hook vanes, and W-weir structures; however, all of these structures are rock vane variations. The following section builds on existing rock vane guidance with input from the comprehensive physical and numerical experi- ments described in previous sections. F.2.1 Structure Geometry Vane Slope General guidelines suggest that the vane arm should slope from the bankfull water surface elevation on the attached bank to the bed with a slope of between 2% to 7% (Maryland Department of the Environment, 2000; NRCS, 2007), although this can vary up to 20% in channels with low aspect ratios (Doll et al., 2003). In general, longer, flatter vanes will offer greater lengths of bank protection. Vane Length Vane length is typically designed such that the vane tip is located between 1⁄4 and 1⁄3 of the bankfull width, Bbf, across the channel (Brown, 2000; NRCS, 2007), or <1⁄2 of base-flow channel width (Doll et al., 2003). For very large rivers where it is imprac- tical to extend the vane at the desired angle to 1⁄3 Bbf, shorter vane lengths are appropriate, following vane slope and angle guide- lines. The experiments and simulations considered in NCHRP Project 24-33 evaluated rock vane structures installed at 1⁄3 Bbf. F.2.2 Structure Layout Angle of Orientation By definition, rock vanes have a shallow upstream angle of between 20° and 30° from the tangent to the upstream bank. The vane tip points in the upstream direction, with 0° aligned with the bank and 90° perpendicular to the bank (NRCS, 2007; Doll et al., 2003; Maryland Department of the Envi- ronment, 2000; Brown, 2000). Results from NCHRP Proj- ect 24-33 experiments and simulations indicate that larger angles provide a greater length of bank protection across a range of channel characteristics (aspect ratio 5–30, sinuosity 1–1.5, slope 10-4 -10-3, grain size 0.5–30 mm) but also typi- cally result in a deeper scour hole adjacent to the rock vane tip. In low Rc/B channels, a rock vane installed with a 30° angle at the outer bend apex threatens the stability of the inner bank.

71 Based on NCHRP Project 24-33 results, the angle of orienta- tion for rock vanes for bank protection should be 30° from the tangent to the bank channels in typical gravel rivers and 20° from the tangent to the bank in more sinuous typical sand rivers (see Chapter 3 for more information). Vane Location and Spacing Rock vanes should be installed in series of at least two struc- tures to protect the entire region of the outer bank subject to scour (Johnson et al., 2001). Specific guidelines on vane spac- ing and vane placement are sparse. Doll et al. (2003) suggest that rock vanes should be located just downstream of where the flow intercepts the bank at acute angles. Bhuiyan et al. (2010) give an example of a circular meander with vanes spaced such that the whole bank is covered. The Maryland Department of the Environment guidelines (2000) suggest spacing of one or more channel widths for habitat considerations, depending on the pattern of scour pools, in reference reaches, or five to seven bankfull widths if the restoration goal is to initiate meandering. Chapter 11 of the NRCS manual provides empirical equations for calculating spacing based on the channel radius of curva- ture and width (NRCS, 2007; Table 12). Based on the results of NCHRP Project 24-33, a vector analysis approach is suggested, as described in the structure layout section (Section F.7). Based on the numerical results of NCHRP Project 24-33, for proj- ects where outer bank protection is the primary project goal, a rock vane structure array should begin at the meander apex in large radius of curvature channels (Rc/B > 3) to minimize the number of structures installed. For smaller radius of curvature channels, the final structure array should be shifted upstream by approximately one channel width to provide adequate bank protection and minimize the risk of structure failure due to excessive local scour or flanking. If rock vanes are installed to protect specific infrastructure in a large Rc/B or straight channel, the vane should be installed two or more channel widths upstream of the infrastructure they are designed to protect (Johnson et al., 2001; Johnson et al., 2002a) F.2.3 Construction Footer Rocks To prevent structure failure due to local scour around the rock vane base, substantial footer rocks should be installed below the stream grade. Typically, footer rocks are one to two large rocks underneath the top rock. Footer rocks should be downstream of the top rock to minimize structure failure by rocks falling into a downstream scour hole (Doll et al., 2003). Gaps between footer rocks up to 1⁄3 of the stone diameter can enable interlocking (Brown, 2000). Footer rock size should be at least three times the protrusion height of the vane. This depth should be doubled for sand-bed streams (NRCS, 2007). Based on the numerical results from NCHRP Project 24-33, footer rocks should be installed at an elevation that is 1 to 1.5 times deeper than the maximum scour along the outer bank of the channel (ScMAX). Johnson et al. (2001) suggest the use of geotextile fabric or well-graded material to mitigate structural porosity. Doll et al. (2003) recommend that geotextile fabric always be used for any rock vane or modified rock vane structure. Rock Size Rock vanes are typically constructed from rock much larger than the rock size for other redirective flow training structures such as bendway weirs or stream barbs. Rocks in bendway weirs and stream barbs are commonly sized using riprap sizing equations with a factor of safety (i.e., NRCS guidance suggests two times the median grain size, D50, for stream-bank riprap). The rock used to construct rock vanes is typically much larger than riprap equations suggest as the rocks are not interlocking. One method for sizing individual boulders is based on a balance of the forces on an individual rock (Fischenich and Seal, 2000); however, these equations also undersize the rock. The rock size needs to be large enough to withstand local scour around the base of the structure. Many other guidelines suggest large rock sizes regardless of local stream-channel characteristics (i.e., 1 to 2 tons, Doll et al., 2003; or >200 lbs, Maryland Department of the Environment, 2000). Rosgen (2006) provides a general reference for mini- mum rock size based on a limited number of rivers. ( )= τ +min 0.174 0.6349D Ln where t = bankfull shear stress in kg/m3. This relationship results in a much larger rock size than other rock-sizing methods. Rock shape depends on local availability but typically should be flat to allow interlocking, and vane rocks should be touching (Doll et al., 2003; Maryland Department of the Environment, 2000). Large rocks and boulders can be placed on the downstream side of the structure to enhance stability (Maryland Department of the Environment, 2000). For rock vanes, rocks placed at the tip of the structure are subject to forces that are approximately 1.5 to 3 times the force on rocks closer to the stream bank. This is compounded by the fact that the deepest scour occurs near the structure tip. Therefore, rocks placed at the tip of the structure need to be large enough to account for the forces exerted by the turbulent flow. Sills (Bank Key) Sills consisting of two to three large rocks built into the stream bank can help mitigate erosion behind rock vanes, especially on new channels (Maryland Department of the Environment, 2000; NRCS, 2007). Experimental and numerical results from

72 NCHRP Project 24-33 indicated that a large amount of sedi- ment was transported and stored upstream of rock vanes. This additional sediment may lead to bank overtopping and flank- ing of the structure as sediment deposition becomes vegetated under low flows, increasing local roughness and redirecting flow around and behind the structure. F.2.4 Maintenance and Monitoring To ensure proper structure performance, installed struc- tures need to be monitored for signs of structure failure, particularly after the first large flood event. The following suggestions are included based on the results from NCHRP Project 24-33 for monitoring and maintenance of rock vanes. • Structures should be monitored for local scour, particu- larly near the tip of the structure where the large hydro- dynamic forces could combine with undermining of the footer rock to shift rocks at the structure tip. • Structures should be monitored for signs of excessive depo- sition and potential flanking following large flow events. Over time, vegetation can begin to grow on this deposited material, shifting flow around the outside of the structure. • The opposite bank should be monitored for signs of un- acceptable scour well downstream of the structure (>5 chan- nel widths). F.3 J-Hook Vane Design Guidelines J-hook vanes are a variation on the single-arm rock vane that includes a hook that extends from the tip of the vane approximately perpendicular to the flow (Figure F-5). Similar to the rock vane, the vane portion of these structures gradually slopes from the bank to the bed such that, even at low-flow Figure F-5. Typical J-hook vane installation (after Rosgen, 2006).

73 conditions, the tip of the structure remains submerged ( Radspinner et al., 2010). J-hook vanes are also installed with an upstream angle to minimize erosive flow patterns near the bank by diverting high-velocity flow away from the bank (Maryland Department of the Environment, 2000; Johnson et al., 2002a). Often, rock vanes and other in-stream rock struc- tures are installed with a secondary goal of improving aquatic habitat by creating flow diversity through the formation of scour pools (Rosgen, 2006), and J-hook vanes are expected to provide additional in-stream habitat enhancement in the form of a mid-channel scour pool (Maryland Department of the Environment, 2000). Current guidelines for placement and spacing of J-hook vanes are similar to those developed for rock vanes, based primarily on practitioner experience (e.g., Maryland Department of the Environment, 2000; Doll et al., 2003; NRCS, 2007). Applications for J-hook vanes are similar to those for rock vanes, with the exception that J-hook vanes are expected to provide better in-stream habitat in the form of a deep scour hole (Maryland Department of the Environment, 2000). Limitations of J-hook vanes are similar to those of rock vanes. These structures should not be used in steep stream reaches (greater than 3%). With any flow-redirection structure, the stream bank opposite the structures should be monitored closely after installation for any increase in erosion occurring due to the presence of the structure. All structures from the rock vane family can be subjected to failure by lateral circum- vention, winnowing, local scour, aggradation, and displace- ment (Johnson et al., 2002b). J-hook design guidelines can be found in the MWCG (Maryland Department of the Environ- ment, 2000) and the USDA NRCS Stream Restoration Design National Engineering Handbook, Part 654 (NRCS, 2007). Chapter 11 of this design manual, “Rosgen Geomorphic Channel Design,” focuses on the design guidelines for cross vanes, J-hook vanes, and W-weir structures. The following section builds on existing J-hook vane guidance with input from the comprehensive physical and numerical experiments from NCHRP Project 24-33. F.3.1 Structure Geometry Vane Slope See Structure Geometry section (Section F.2.1) for guidelines. Vane Length J-hook vane length is typically designed such that the vane tip is located between 1⁄4 and 1⁄3 of the bankfull width, Bbf, across the channel (Brown, 2000, NRCS, 2007) or <1⁄2 of base-flow channel (Doll et al., 2003), and the hook portion of the J-hook vane extends to no greater than 2⁄3 of the channel width. For very large rivers where it is impractical to extend the vane at the desired angle to 1⁄3 Bbf, shorter vane lengths are appropriate, following the vane slope and angle guidelines. F.3.2 Structure Layout Angle of Orientation By definition, J-hook vanes have a shallow upstream angle of between 20° and 30° from the tangent to the upstream bank (NRCS, 2007; Doll et al., 2003; Maryland Department of the Environment, 2000; Brown, 2000). In general, larger angles provide greater bank protection across a range of channel characteristics (aspect ratio 5–30, sinuosity 1–1.5, slope 10-4–10-3, grain size 0.5–30 mm), but 20° angles pre- sent significant risk to the inner bank. Based on the experi- mental and numerical results from NCHRP Project 24-33, 30° from the tangent to the bank is an appropriate angle of orientation for J-hook vanes in typical gravel rivers, and 20° is appropriate for more sinuous sand rivers (see Chapter 3 for more information). Vane Location and Spacing When used for meander bend protection, J-hook vanes should be installed in series of at least two structures to protect the entire region of the outer bank subject to scour (Mooney et al., 2007). Specific guidelines on vane spacing and vane placement are sparse. Similar to rock vanes, the Maryland Department of the Environment guidelines (2000) suggest spacing of one or more channel widths for habitat consider- ations, depending on the pattern of scour pools, in reference reaches, or 5 to 7 bankfull widths if the restoration goal is to initiate meandering. Chapter 11 of the NRCS manual provides empirical equations for calculating spacing based on the chan- nel radius of curvature and width (NRCS, 2007; Table 12). Based on the results of NCHRP Project 24-33, a vector analy- sis approach is suggested as described in Section F.7. Based on the numerical results of NCHRP Project 24-33, for large radius of curvature to width ratio channels (Rc/B > 3), where outer bank protection is the project goal, the structure array should begin at the meander apex to minimize the number of structures installed. For smaller radius of curvature chan- nels, the final structure array should be shifted upstream by approximately one channel width to provide adequate bank protection and minimize the risk of structure failure due to excessive local scour or flanking. If J-hook vanes are installed to protect specific infrastruc- ture in a large Rc /B or straight channel, the vane should be installed two or more channel widths upstream of the infra- structure they are designed to protect.

74 F.3.3 Construction Footer Rocks To prevent structure failure due to local scour around the J-hook vane base, substantial footer rocks should be installed below the stream grade. Typically, footer rocks are one to two large rocks underneath the top rock. Footer rocks should be downstream of the top rock to minimize structure failure by rocks falling into a downstream scour hole (Doll et al., 2003). Gaps between footer rocks up to 1⁄3 of the stone diameter can enable interlocking (Brown, 2000). Footer rock size should be at least three times the protrusion height, and this depth should be doubled for sand-bed streams (NRCS, 2007). Based on the numerical results from NCHRP Project 24-33, footer rocks for J-hook vanes should be installed at an elevation that is 1.5 to 2 times deeper than the maximum scour along the outer bank of the channel (ScMAX; see Chapter 6). Rock Size J-hook vanes are typically constructed from rock much larger than the rock used for other redirective flow training structures such as bendway weirs or stream barbs (see the Rock Size subsection in Section F.2.3 for more information). Excessive gaps between rocks can lead to winnowing and subsequent failure of the structure. Johnson et al. (2001) suggest that field procedures such as the use of geotextile fabric or well-graded material be used to mitigate structural porosity. Doll et al. (2003) recommend that geotextile fab- ric always be used for any rock vane or modified rock vane structure. Alternatively, grouting structures can help them survive high-flow events. NCHRP Project 24-33 evaluated structures where gaps between rocks were limited to the tip of the hook portion of the vane. Gaps in the hook were found to significantly alter sediment transport through the structure. For J-hook vanes, rocks placed at the tip of the structure are subject to forces that are approximately 4 to 5 times the force on rocks closer to the stream bank. This is compounded by the fact that the deepest scour occurs near the structure tip. Therefore, rocks placed at the tip of the structure need to be large enough to account for the forces exerted by the turbulent flow. Sills (Bank Key) Sills consisting of two to three large rocks built into the stream bank can help mitigate erosion behind rock vanes, especially in new channels (Maryland Department of the Environment, 2000; NRCS, 2007). Experimental and numer- ical results from NCHRP Project 24-33 indicated that a moderate amount of sediment was transported and stored upstream of J-hook vanes. This additional sediment may lead to bank overtopping and flanking of the structure as sediment deposition becomes vegetated under low flows, increasing local roughness and redirecting flow around the structure. F.3.4 Maintenance and Monitoring To ensure proper structure performance, installed struc- tures need to be monitored for signs of structure failure, particularly after the first large flood event. The following suggestions are included based on the results from NCHRP Project 24-33 for monitoring and maintenance of rock vanes. • Structures should be monitored for local scour, particu- larly near the tip and on the hook of the structure. Large hydrodynamic forces could combine with undermining of the footer rock to shift rocks at the structure tip or displace the rocks that form the hook part of the structure. • Structures should be monitored for signs of excessive depo- sition and potential flanking following large flow events. Over time, vegetation can begin to grow on this deposited material, shifting flow around the outside of the structure. • The opposite bank should be monitored for signs of un- acceptable scour well downstream of the structure (>5 channel widths). F.4 Bendway Weir/Stream Barbs The terms “bendway weir” and “stream barb” refer to single-arm rock structures extending from the bank that are submerged in all but low flows and are designed to mitigate erosive flow patterns through weir mechanics (Derrick, 1998; Evans and Kinney, 2000; see Figure F-6). Several state agen- cies have published technical notes and case studies for bend- way weir use under a variety of stream characteristics (e.g., NRCS, 2010). Stream barbs are designed to protect the bank by disrupting velocity gradients in the near-bed regions, deflecting currents toward the tip of the weirs (Matsuura and Townsend, 2004). F.4.1 Structure Geometry Weir Slope and Weir Height Bendway weirs are typically installed with a nearly flat (Lagasse et al., 2009) or slightly sloping weir slope. The trans- verse slope along the centerline should be no steeper than 1V:5H (1 vertical to 5 horizontal); however, care should be taken that the slope does not redirect flow toward the bank to be protected. The flat weir section normally transitions into

75 the bank on a slope of 1V:1.5H to 1V:2H. The height of the weir should meet the following criteria (Lagasse et al., 2009): • Between 30% and 50% of the mean annual high-water level (or bankfull level) (NRCS, 2007), • Below the normal or seasonal mean water level, • Equal to or above the mean low-water level, and • Of adequate height to intercept a large enough percentage of the flow to produce the desired results. Weir Length Suggested weir lengths range from 1⁄10 to 1⁄4 of the channel width, not to exceed 1⁄3 of the channel width (NRCS, 2007; Lagasse et al., 2009). F.4.2 Structure Layout Angle of Orientation Guidelines for the angle of orientation for bendway weirs vary greatly from 20° to 80° from the tangent to the outer bank (e.g., NRCS, 2007; Lagasse et al., 2009). NCHRP Proj- ect 24-33 found that the optimum angle should be selected by evaluating the combined effect of multiple structures and longer vane length. Results from this project suggest that a moderate angle of 50° balanced the length of bank protection provided by longer weirs with the smaller cost of installation of higher angle (shorter weirs). Weir Location and Spacing The furthest upstream barb should be placed near or just upstream of the area first affected by erosion and should not be placed downstream of 3⁄4 of the turn length ( Castro and Sampson, 2001). Based on numerical simulations from NCHRP Project 24-33, placing the first bendway weir at the meander apex sufficiently protected the toe of the bank on the outer bank of the meander. Typical bendway weir spac- ing should range from 5 to 10 times the effective struc- ture length, and ideally 4 to 5 times the effective length (NRCS, 2007; Lagasse et al., 2009). A vector analysis (e.g., NRCS, 2007; described in Section F.7) provides guidance into bendway weir structure spacing around a meander. In this type of analysis, lines are projected from the tip of the upstream structure to the bank to determine where to place the second structure. Figure F-6. Typical bendway weir installation (after NRCS, 2007 and Radspinner et al., 2010).

76 F.4.3 Construction Footer Depth Bendway weir structures should be installed during low- flow periods, with rock placement beginning at the upstream end of the structure (Castro and Sampson, 2001). Footer rocks installed in the streambed need to be at least D100 or 2.5 times the exposed rock height for gravel and 3 to 3.5 times exposed rock height for sandy streams. Based on the numeri- cal results from NCHRP Project 24-33, footer rocks should be installed at an elevation that is 1 to 1.5 times deeper than the maximum scour along the outer bank of the channel (ScMAX; see Chapter 6). Rock Size Rock size is typically determined using riprap sizing crite- ria for turbulent flow (NRCS, 2007; West Lane method). In addition, the following criteria should be met (Lagasse et al., 2009; NRCS, 2007): • D50, stream barb = 2 × D50, as determined for stream bank riprap. • D100, stream barb = 2 × D50, stream barb. • Dmin = 0.75 × D50, as determined for stream bank riprap. • Rock in the barb should be well graded in the D50 to D100 range for the weir section; the smaller material may be incorporated into the bank key. The largest rocks should be used in the exposed weir section at the tip and for the bed key (footer rocks) of the barb. • The Isbash curve (NEH-650.16; NEH = National Engineer- ing Handbook) is not appropriate for sizing rock for stream barbs since it results in sizes too small for this application. • Stone should be angular, and not more than 30% of the stones should have a length exceeding 2.5 times their thickness. • No stones should be longer than 3.5 times their thickness. • Typically, the size should be 20% greater than computed from nonturbulent riprap sizing formulas. • The minimum rock size should not be smaller than the D100 of the streambed. Sills (Bank Key) Bendway weirs/stream barbs have a relatively low risk of flanking from overbank flows compared to rock vanes or J-hook vanes. However, guidelines suggest that bendway weirs should be keyed into the bank at least 1.5 times bank height (NRCS, 2007). More specific bank key guidelines based on a 20° angle of expansion can be found in HEC 23 (Lagasse et al., 2009) and are listed as follows. When the channel radius of curvature is large (Rc > 5B): = −tan (20)LK Vs Le where: Vs = spacing, LK = length of key, and Le = effective length of weir. When the channel radius of curvature is small (Rc < 5B): ( )( ) ( )= 2 0.3 0.5LK Le B Le Vs Rc F.4.4 Maintenance and Monitoring To ensure proper structure performance, installed struc- tures need to be monitored for signs of failure, particularly after the first large flood event. The following suggestions are included based on the results from NCHRP Project 24-33 for monitoring and maintenance of bendway weirs. • Structures should be monitored for local scour, particu- larly near the tip of the structure where the large hydro- dynamic forces could combine with undermining of the footer rock to shift rocks. • Structures should be monitored for signs of excessive depo- sition and potential flanking following large flow events. Over time, vegetation can begin to grow on this deposited material, shifting flow around the outside of the structure. • The opposite bank should be monitored for signs of un- acceptable scour well downstream of the structure (>5 chan- nel widths). F.5 Cross Vane Design Guidelines Cross vanes are low-profile, channel-spanning structures designed to provide grade control, divert flow away from unstable banks, and create scour pools for aquatic habitat (Maryland Department of the Environment, 2000). Cross vanes have also been installed upstream of bridge piers to reduce scour. There are two types of cross vanes. The first is a U-shaped structure, which has two arms angled upstream at 20° to 30° from the banks that slope downward to the stream- bed cross piece (Figure F-7). The second type, an A-shaped structure, is a modified cross vane with a step located in the upper 1⁄3 to 1⁄2 of the arm. This step is designed to dis- sipate energy, thereby reducing footer scour and protecting the structure from failure (Rosgen, 2006). Cross vanes are well suited for use in moderate- and high-gradient streams and should be avoided in bedrock channels, streams with unstable bed substrates, and naturally well-developed pool–

77 Figure F-7. Typical cross vane installation (after Rosgen, 2006). riffle sequences (Maryland Department of the Environment, 2000). Cross vane design guidelines can be found in Rosgen (2006), the MWCG (Maryland Department of the Environ- ment, 2000), and the USDA NRCS Stream Restoration Design National Engineering Handbook, Part 654 (NRCS, 2007). Chapter 11 of this design manual, “Rosgen Geomorphic Channel Design,” focuses on the design guidelines for cross vanes, J-hook vanes, and W-weir structures. F.5.1 Structure Geometry Cross Vane Step Two variations of cross vane were tested in NCHRP Proj- ect 24-33: a standard U-shaped cross vane, and a cross vane with a step (a A-shaped cross vane). A stepped, A-shaped cross vane should be used to provide additional protection for the upstream rocks; however, an A-shaped structure poses a greater risk to the stability of banks immediately downstream and should not be used if bank protection is the project goal. Vane Slope See Structure Geometry section (Section F.2.1) for guidelines. Vane Length Vane length is typically designed such that the vane tip is located between 1⁄4 and 1⁄3 of the bankfull width, Bbf, across the channel (Brown, 2000, NRCS, 2007), or <1⁄2 of base-flow chan- nel (Doll et al., 2003), and the cross portion extends over the middle 1⁄3 of the channel width. For very large rivers where it is impractical to extend the vane at the desired angle to 1⁄3 Bbf, other structure configurations, such as a W-weir, could be considered. F.5.2 Structure Layout Angle of Orientation By definition, cross vanes have a shallow upstream angle of between 20° and 30° from the tangent to the upstream bank (NRCS, 2007; Doll et al., 2003; Maryland Department of the Environment, 2000; Brown, 2000). Results from this research indicate that larger angles provide greater bank protection across a range of channel characteristics (aspect ratio 5–30, sinuosity 1–1.5, slope 10-4–10-3, grain size 0.5–30 mm), and smaller angles present significant risk to the banks down- stream of the cross vane structure. Based on these results, the angle of orientation for cross vanes for bank protection should be 30° from the tangent to the bank. Cross vanes with

78 large angles (generally greater than 30°) have shown indi- cators of partial and full failure in field investigations (U.S. Department of the Interior, Bureau of Reclamation, 2009). Vane Location and Spacing While it is suggested that cross vanes can be used to protect unstable banks, very little information exists on the optimal placement of vanes to meet this goal. Based on the results from NCHRP Project 24-33, sill structures should be installed a minimum of two channel widths upstream of bridge piers or other infrastructure due to scour immediately downstream of these structures. For A-shaped cross vanes, this should be extended to 2.5 to 3 channel widths. An alternative would be to install structures in series to minimize the dimensions of the scour hole immediately downstream of a cross vane. A sill structure raises or maintains the bed elevation, so it is normally installed within a section of little or no turbulence for larger streams or at the head of a riffle for smaller streams (Doll et al., 2003). The Maryland Department of the Envi- ronment guidelines (2000) suggest spacing depending on the pattern of scour pools in reference reaches. F.5.3 Construction Footer Rocks, Rock Size, and Sills See Construction section (Section F.2.3) for guidelines. Footer rocks should be large enough to resist movement from shear stresses during the design flow. Long and flat rocks tend to perform better in the field (U.S. Department of the Interior, Bureau of Reclamation, 2009). F.5.4 Maintenance and Monitoring To ensure proper structure performance, installed struc- tures need to be monitored for signs of failure, particularly after the first large flood event. The following suggestions are included based on the results from NCHRP Project 24-33 for monitoring and maintenance of cross vanes. • Structures should be monitored for local scour, particularly downstream of cross members of the A- or U-shaped cross vane where the large hydrodynamic forces could combine with undermining of the footer rock to shift rocks. • Structures should be monitored for signs of excessive depo- sition and potential flanking following large flow events. Over time, vegetation can begin to grow on this deposited material, shifting flow around the outside of the structure. • The bank within two channel widths downstream should be monitored for signs of scour as the scour hole down- stream widens. Additional bank protection may be required in this zone. F.6 W-Weirs Like cross vanes, W-weirs are low-profile, channel-spanning structures designed to provide grade control, direct flow away from unstable banks, create scour pools for aquatic habitat, and protect downstream bridge piers (see Figure F-8). W-weirs are similar to a double cross vane and are typically applicable in larger channels (>12 m or 40 ft in width). They are well suited to protect the bank toe, redirect flow, create flow diversity, and stabilize bed and lateral channel adjustments in chan- nels with highly erodible and steep banks, high design veloc- ity, flashy flows, and high-bedload transport. With proper support, W-weirs can be used with rigid or fixed banks with limited backwater effects. W-weirs are not suited for slow- flow or pooled reaches with silt or fine sand bed (Maryland Department of the Environment, 2000). W-weir design guide- lines can be found in Rosgen (2006), the MWCG (Maryland Department of the Environment, 2000), and the USDA NRCS Stream Restoration Design National Engineering Handbook, Part 654 (NRCS, 2007). Chapter 11 of this design manual, “Rosgen Geomorphic Channel Design,” focuses on the design guidelines for cross vanes, J-hook vanes, and W-weir structures. F.6.1 Structure Geometry Vane Slope See Structure Geometry section (Section F.2.1) for guidelines. Vane Length Vane length is typically designed such that the vane tip is located 1⁄4 of the bankfull width, Bbf, across the channel (Brown, 2000, NRCS, 2007). The middle V portion of the W-weir extends across the middle 1⁄2 of the channel width unless an asymmetri- cal W-weir is being designed for a specific project goal. F.6.2 Structure Layout Angle of Orientation By definition, W-weirs have a shallow upstream angle of between 20° and 30° from the tangent to the upstream bank (NRCS, 2007; Doll et al., 2003; Maryland Department of the Environment, 2000; Brown, 2000). Results from this research indicate that larger angles provide greater bank protection across a range of channel characteristics (aspect ratio 5–30, sinuosity 1–1.5, slope 10-4–10-3, grain size 0.5–30 mm), and smaller angles present significant risk to the banks down- stream of the W-weir structure. Based on these results, the angle of orientation for W-weirs for bank protection should be 30° from the tangent to the bank. Channel-spanning structures, including cross vanes and W-weirs with large angles (generally greater than 30°), have shown indicators

79 of partial and full failure in field investigations (U.S. Depart- ment of the Interior, Bureau of Reclamation, 2009). Vane Location and Spacing The downstream end of the riffle zone and the glides lead- ing into the riffles are the most desirable locations since those areas will offer minimal interference with sediment transport capability (Bhuiyan et al., 2010). Results from NCHRP Proj- ect 24-33 indicate that W-weirs performed similarly in these locations; however, sill structures installed at the downstream end of a riffle zone resulted in greater interference with the meander bend mechanics and altered the bed topography in this region. The Maryland Department of the Environment guidelines (2000) suggest spacing depending on the pattern of scour pools in reference reaches or desired step pool spacing. Sill structures should be installed a minimum of two channel widths upstream of bridge piers or other infrastructure to be protected. An alternative would be to install structures in series to minimize the dimensions of the scour hole immedi- ately downstream of a W-weir. F.6.3 Construction Footer Rocks, Rock Size, and Sills See Construction section (Section F.2.3) for guidelines. Footer rocks should be large enough to resist movement from shear stresses during the design flow. Long and flat rocks tend to perform better in the field (U.S. Department of the Interior, Bureau of Reclamation, 2009). Johnson et al. (2001) suggest that field procedures such as the use of geo- textile fabric or well-graded material be used to mitigate structural porosity. Doll et al. (2003) recommend that geo- textile fabric always be used for any rock vane or modified rock vane structure. Figure F-8. Typical W-weir installation (after NRCS, 2007).

80 F.6.4 Maintenance and Monitoring To ensure proper structure performance, installed struc- tures need to be monitored for signs of structure failure, particularly after the first large flood event. The following suggestions are included based on the results from NCHRP Project 24-33 for monitoring and maintenance of W-weirs. • Structures should be monitored for local scour, particu- larly downstream of the W portion of the weir. • Structures should be monitored for signs of excessive depo- sition and potential flanking following large flow events. Over time, vegetation can begin to grow on this deposited material, shifting flow around the outside of the structure. • The bank within two channel widths downstream should be monitored for signs of scour as the scour hole down- stream widens. Additional bank protection may be required in this zone. F.7 Structure Layout for Single-Arm Structures Using a modified vector analysis commonly employed for bendway weirs or stream barbs (Lagasse et al., 2009; NRCS, 2007), the following guidelines are suggested to determine Figure F-9. Example layout for first structure at apex, second structure (top), and third structure (bottom) in two different channels. the optimum structure layout for each in-stream flow control structure array described in Sections F.2 to F.6. 1. Project a line tangent to the bank at the meander apex. Set this line at 0° (horizontal). 2. Place the first structure at the apex. The angle of orienta- tion should be such that it intercepts flow from upstream. This angle is dependent on the sinuosity and curvature of the meander where the structures are being installed (see Figure F-9). a. Rock vanes and J-hooks: Greater angles protect more channel length in larger radius of curvature streams, and smaller angles protect more bank in smaller radius of curvature, more sinuous channels. b. Bendway weirs/stream barbs: An angle of 50° was determined to be the optimum between cost (length of structure) and length of bank protected. Greater angles may provide greater bank protection, but at the cost of decreased structure stability. 3. Draw a horizontal line parallel to the first line from the tip of the structure. Draw another line with an offset angle from the parallel line. Where this line intersects the bank, the next structure should be located. The offset angle is a function of stream radius of curvature and channel width (Table F-4; see Chapter 3 for specifics).

81 Primary Goals Outer Bank Protection Enhanced Habitat Diversity/ Scour Pools Grade Control Se co nd ar y G oa ls Outer bank protection BW, RV RV, JH — Enhanced habitat diversity/ scour pools JH, RV JH, CW, WW, RV CV, WW Grade control — CV, WW CV, WW Table F-5. Project goal matrix for single-arm rock structures. Bed material (D50) Non-Cohesive Sand, 0.7 mm Slope 7 x 10–3 Sinuosity 1.3 Radius of curvature (Rc) 5.7 m Width (B) 2.7 m Depth (H) 0.3 m Bankfull discharge (Qbf) 0.28 m3/s Maximum velocity (outside of meander) 0.6–0.8 m/s Table F-6. Site characteristics for Design Example 1, small meandering stream. 4. Shift array upstream if necessary (see Chapter 3 or Sec- tions F.2 to F.6). F.8 Design Examples F.8.1 Design Example 1: JHs in a Small Meandering Stream Step 1. Define Project Goals and Channel Characteristics For this example, the project goals are to (1) create scour pool habitat, and (2) protect the outer bank of a meandering stream. For this project, there is a significant buffer between the outer bank and a road, so outer bank protection is selected as a secondary goal. Based on these criteria, J-hook vanes are selected from Table F-5. Site characteristics for this project are listed in Table F-6. This is a low-gradient meandering sand-bed stream. The project site is a sharp meander. Bed topography data were collected to map out the length of bank erosion and the apex of the meander and to calculate the slope and radius of cur- vature, Rc (see Figure F-10). Additional data were collected to define the maximum scour (ScMAX) around the outer mean- der bank (Figure F-11). Step 2. Structure Selection Based on the site characteristics and project goals, JHs were selected for this project (see Tables F-2 and F-3 for more information on selection criteria). Step 3. Angle of Orientation Based on the moderate sinuosity and low Rc/B ratio, this is a sharp meander bend; therefore, a smaller angle of orienta- tion should be selected for JHs. An angle of 20° is selected. Step 4. Layout Vector analysis is used to map out the optimum structure location based on the channel characteristics and structure type. This process is described in Figure F-12. Step 4a. Numerical Modeling (Recommended) Fine-tune structure layout design and verify site-specific performance using 2-D or 3-D numerical modeling. Select a model that will allow for examination of flow paths. The VSL3D model developed in this work can serve this pur- pose. The goal of the modeling is to verify that this struc- ture layout will shift the high-velocity core away from the outer bank. Step 5. Evaluate Potential for Structure Failure and Create Monitoring Plan Footer rock depth should be 1.5 to 2 times ScMAX (Fig- ure F-13). The rocks in the hook portion of a JH structure are subject to the largest hydrodynamic forces and are most susceptible to undermining from excessive scour. Therefore, monitoring plans for JHs should include a stability analysis focused on the hook portion of the structure. In addition, JHs have a moderate potential for flanking based on sediment Structure Type 2nd Structure Offset (Degrees) 3rd Structure Offset (Degrees) RV –5 to 5 20 (if needed) JH –5 to 5* 20* (if needed) BW 5 25 to 30 *For JH structures, the second structure offset begins at the first JH vane tip for sharp meanders and at the second structure hook tip for the third structure offset. For other meanders, the second structure offset begins at the first JH hook tip (see Section 3.2 for more information). Table F-4. Offset angles for additional structure placement based on the intersection of the shear layer of the first structure with the outer bank.

82 Figure F-10. Bed topography for Design Example 1 for a small meandering stream. Flow is from left to right. Figure F-11. Example cross section for Design Example 1 for a small meandering stream. Dotted line is average bed elevation calculated from field data. ScMAX is the difference between the maximum scour depth and the average depth. deposition upstream of each structure. Monitoring should also be focused here, especially if vegetation begins to grow on this sediment. Footer rocks: 1.5 to 2 times ScMAX = 0.36 m - 0.46 m F.8.2 Design Example 2: BWs in a Meandering River Step 1. Define Project Goals and Channel Characteristics Primary goal: Bank protection for an eroding bank on the outside of a meander. Site characteristics are listed in Table F-7. Step 2. Structure Selection Based on the site characteristics and project goals, BWs were selected for this project (see Tables F-2 and F-3 for more information on selection criteria). Step 3. Angle of Orientation An optimum angle of 50° will be selected for the BW. Step 4. Layout Vector analysis will be used to map out the optimum structure location based on the channel characteristics and

83 Figure F-13. Example of footer rock depth, Design Example 1 for a small meandering stream. Figure F-12. Example layout for Design Example 1 for a small meandering stream. Steps A through H are described in the following. A. Draw a line tangent to the outer bank at the meander apex. Orient the layout so that this line is 0°, or horizontal. B. Draw the first JH structure at an angle of orientation of 20° to the tangent to the bank. The structure length is selected so that the vane effective length, Le, is equal to 1⁄3 B. The hook part of the structure is another 1⁄3 B so that the entire Le is 2⁄3 B. C. Extend a line from the vane portion of the first JH at an angle of -5° from horizontal. D. Place the second JH where this line intersects the outer bank. This structure should be 20° from the tangent to the bank, with Le = 2⁄3 B. E. Extend a line from the hook portion of the second JH at an angle of 20° from the horizontal. F. Place the third JH where this line intersects the outer bank. G. Because this is a sharp meander, JHs function better if shifted a channel width, B, upstream. Shift the entire array upstream by B. H. Finalize JH dimensions according to Figure F-5. The angle of orientation for each structure should be 20° from the tangent to the bank, with Le = 2⁄3 B (vane Le = 1⁄3 B). Bed material (D50) Non-cohesive sand, 0.4 mm Slope 3 x 10 -4 Sinuosity 1.4 Radius of curvature (Rc) 36 m Width (B) 12 m Depth (H) 1.0 m Bankfull discharge (Qbf) 27 m3/s Table F-7. Site characteristics for Design Example 2 for a meandering river. Figure F-14. Schematic of the placement of the second BW. Place the first BW at the meander apex. Set location of second BW with 5 offset from horizontal. Bendway Weir Top slope 0% Side slope 1:2 Slope at the tip Top width Bottom width 2H + D100 Max. height of structure H/2 Effective length span B/4 Single rock size (D100) 2D100 Ø 0.569 m Table F-8. Geometrical characteristics of BW structures based on design guidelines provided in Section F.4. B, H, and f in the table are river width, flow depth, and rock’s angle of repose, respectively. structure type. An array of at least three BWs is needed for most channels. The general steps are as follows: 1. Install the first BW with a 50° angle of orientation at the apex of the meander [on the outer bank of the meander (Figure F-14)]. 2. Install the second BW with a 50° angle of orientation with a 5° offset from a horizontal line drawn from the first BW tip (Figure F-14). 3. Install the third BW with a 50° angle of orientation with a 30° offset from a horizontal line drawn from the second BW tip (Figure F-15).

84 Figure F-15. Schematic of the placement of the third BW. Set location of the third BW with 30 offset from horizontal. Step 4a. Numerical Modeling (Recommended) This arrangement should provide the maximum protec- tion with the least number of structures for this channel. The effectiveness of this layout should be verified using a 2-D or 3-D numerical flow model to verify that the structures redirect the high-velocity core away from the outer bank and disrupt the helical flow paths around this meander (the mechanism for outer bank scour in meandering channels). Step 5. Evaluate Potential for Structure Failure and Create Monitoring Plan BWs have the least risk of flanking, smallest hydrodynamic forces, lowest backwater effects, and smaller scour holes than the other single-arm structures. Therefore, maintenance is expected to be minimal. Monitoring, however, should be con- ducted to ensure performance, and should be done specifically for scour between structures or signs of structure instability. F.9 Appendix F References Bhuiyan, F., Hey, R. D., and Wormleaton, P. R. (2010). “Bank-Attached Vanes for Erosion Control and Restoration of River Meanders.” Journal of Hydraulic Engineering. 136(9), 583–596. Brown, K. (2000). Urban Stream Restoration Practices: An Initial Assess- ment. U.S. Environmental Protection Agency, Office of Wetlands, Oceans, and Watersheds, Region V. Ellicott City, MD. Castro, J., and Sampson, R. (2001). “Incorporation of Large Wood into Engineering Structures.” Natural Resource Conservation Service Engineering Technical Note No. 15, USDA, Boise, ID. Derrick, D. L. (1998) “Four Years Later, Harland Creek Bendway Weir/ Willow Post Bank Stabilization Demonstration Project.” Proc., 1998 Int. Water Resources Engineering Conf., ASCE, Memphis, TN. Doll, B. A., Grabow, G. L., Hall, K. L., Halley, J., Harman, W. A., Jennings, G. D., and Wise, D. E. (2003). Stream Restoration: A Natural Channel Design Handbook. NC State University, Raleigh, NC. Evans, J. L., and Kinney, W. (2000). “Bendway Weirs and Rock Stream Barbs for Stream Bank Stabilization in Illinois.” Technical Presenta- tion for 2000 ASABE Int. Meeting, ASABE. Fischenich, C., and Seal, R. (2000). “Boulder Clusters.” EMRRP Technical Notes Collection (ERDC TN-EMRRP-SR-11), U.S. Army Engineer Research and Development Center, Vicksburg, MS. www.wes.army. mil/el/emrrp. Johnson, P. A., Hey, R. D., Brown, E. R., and Rosgen, D. L. (2002a). “Stream Restoration in the Vicinity of Bridges.” J. Am. Water Resour. Assoc., 38(1), 55–67. Johnson, P. A., Tereska, R. L., and Brown, E. R. (2002b). “Using Techni- cal Adaptive Management to Improve Design Guidelines for Urban Instream Structures.” J. Am. Water Resour. Assoc., 38(4), 1143–1152. Johnson, P. A., Hey, R. D., Tessier, M., and Rosgen, D. L. (2001). “Use of Vanes for Control of Scour at Vertical Wall Abutments.” Journal of Hydraulic Engineering. 127(9), 772–778. Lagasse, P. F., Zevenbergen, L. W., Schall, J. D., and Clopper, P. E. (2009). “HEC 23, Bridge Scour and Stream Instability Countermeasures.” FHWA HEC-23, U.S. DOT, FHWA. Maryland Department of the Environment. (2000). Maryland’s Water- way Construction Guidelines. Water Management Administration, Baltimore. Matsuura, T., and Townsend, R. D. (2004). “Stream-Barb Installations for Narrow Channel Bends—A Laboratory Study.” Canadian Jour- nal of Civil Engineering. 31(3), 478–486. McCullah, J., and Gray, D. 2005. NCHRP Report 544: Environmentally Sensitive Channel and Bank-Protection Measures. Transportation Research Board of the National Academies, Washington, D.C. Mooney, D., Holmquist-Johnson, C., and Holburn, E. (2007) Quali- tative Evaluation of Rock Weir Field Performance. Bureau of Reclamation, Technical Service Center, Sedimentation and River Hydraulics Group, Denver, CO. NRCS (2000). “Design of Rock Weirs.” Oregon Technical Notes Engi- neering No. 24, USDA NRCS, Portland, OR. NRCS (2007). Stream Restoration Design National Engineering Hand- book, Part 654. United States Department of Agriculture, National Resource Conservation Service, Washington, D.C. NRCS (2010). “Design of Stream Barbs for Low Gradient Stream.” Minnesota Technical Note No. 8, USDA NRCS, St. Paul, MN. Rosgen, D. L. (2006). Cross-Vane, W-Weir, and J-Hook Vane Structures. Wildland Hydrology, Pagosa Springs, CO. Radspinner, R. R., Diplas, P., Lightbody, A. F., Sotiropoulos, F. (2010). “River Training and Ecological Enhancement Potential Using In-Stream Structures.” Journal of Hydraulic Engineering. 136(12), 967–980. U.S. Army Corps of Engineers. (1991). “Hydraulic Design of Flood Control Channels.” EM 1110-2-1601, Army Corps of Engineers, Department of the Army, Washington, D.C. U.S. Department of the Interior, Bureau of Reclamation. (2009). “Quan- titative Investigation of the Field Performance of Rock Weirs.” U.S. Department of the Interior, Bureau of Reclamation. SRH-2009-46. Denver, CO.

Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S.DOT United States Department of Transportation