Environmentally Sensitive Channel- and Bank-Protection Measures (2005)

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41 APPENDIX B GREENBANK DECISION SUPPORT TOOL USER’S GUIDE HOW THIS SOFTWARE WORKS The Greenbank Decision Support Tool assists users in selecting and learning about environmentally sensitive tech- niques for protecting transportation infrastructure located adjacent to stream channels. Specifically, Greenbank recom- mends streambed and bank erosion control measures suitable for a given site. Greenbank screens a master list of several dozen environmentally sensitive bed- and bank-protection techniques using responses the user provides to 12 to 20 questions. These questions deal with key environmental issues associated with the project, the nature of the stream reach where the project is located, key erosion processes, and cost factors. The master list of techniques is narrowed down using the responses until a short list of suitable techniques is derived. Selection criteria are based on the best available information from the literature and sound fundamental prin- ciples derived from the collective experience of engineers and scientists working with streams over many decades. The system eliminates techniques that published sources indicate are not able to withstand forces produced by design flows at the site in question. Additional queries include or eliminate techniques based on cost and on the way the tech- niques control erosion. For example, continuous measures like stone blanket typically halt erosion entirely, while dis- continuous measures like bank barbs or spur dikes deflect flows but may allow limited erosion between structures after construction until a stable, “scalloped” bank line is formed. At the end of a consultation, Greenbank provides a ranked list of the recommended techniques with explana- tory notes about each one. For each recommended tech- nique, the user may also request a list of techniques that may be combined with the recommended technique to improve the net environmental outcome. A list of all of the techniques that were not recommended is also available to the user, with notes for each technique explaining why it was not recommended. INITIAL INPUTS Environmental Attributes The user provides responses to a series of multiple-choice questions regarding the importance of various types of envi- ronmental attributes for the project in question. Each of 11 specific attributes is rated as very important (2), somewhat important (1), or not important (0). All values are initially set to 0. In order to make dialog more efficient, the user is ini- tially asked for interest in the following four categories: • Water column habitats • Benthic habitats • The riparian zone and related terrestrial habitats or water quality • Public acceptance If interest is expressed in any of the first three of these cat- egories, queries regarding the associated attributes appear: Water column habitats: • Providing instream or overhead cover for fish and other aquatic organisms • Providing and enhancing fish rearing habitat • Providing habitat for adult fish • Creation of velocity refugia • Pool and riffle enhancement Benthic habitats: • Providing or enhancing quality stream bottom (benthic) habitat • Decreasing the amount of sediment deposition occur- ring within the adjacent reach and downstream reaches • Reducing the frequency of bed movement or the sever- ity of erosion The riparian zone and related terrestrial habitats or water quality: • Riparian habitat • Water quality improvement These queries ask the user to assign a value of very impor- tant, somewhat important, or not important to each of the 10 attributes. If the user indicates public acceptance (the 11th attribute) is of interest, the program automatically assigns a value of very important to that attribute. If the user does not assign a value of very important or somewhat important to at least one of the eleven attributes, then a warning message is displayed. “You have not selected any environmental resource or attributes as important. Greenbank is designed to help you select techniques to address environmental issues. You may wish to use the back or restart buttons to revisit previous questions. However, you may continue if you wish.” Erosion processes Greenbank attempts to select bed and bank erosion control measures that address the dominant erosion processes operative

at the site in question. Through dialog with the user, the system links symptoms with causes and selects important erosion processes from a list of 13. The logic allows for the fact that one process may trigger multiple symptoms and that a given symp- tom does not always have the same cause. Furthermore, more than one erosion process may be important for a given site. The dialog begins with Greenbank requesting the user to characterize the erosion problem at the site in question as one of the following: • Development of gullies or rills • Erosion or scour by waves or currents • Bank collapse or mass failure Development of Gullies or Rills If the user selects “development of gullies or rills,” Green- bank requests the user to specify one or more of the three causes: 42 • Overbank runoff • Piping due to steady seepage • Episodic failures due to piping from sudden drawdown or return of overbank flooding to channel Erosion or Scour by Waves or Currents If the user selects “Erosion or scour,” Greenbank asks the user to classify the spatial extent of the problem as either local or general. Greenbank also asks where erosion appears to be occurring: on the bed, at the bank toe, on the middle of the bank, or on the top of the bank. Based on these responses, the user is asked to specify important processes. Allowable choices are indicated in Table B-1. Bank Collapse or Mass Failure If the user specifies that the bank problem is collapse or mass failure, Greenbank asks the user to classify the spatial Spatial extent of erosion (specified by user) Region where erosion is occurring (specified by user) Local (limited to a bank segment a few channel widths long) General (similar processes appear to be occurring for a considerable distance up- and downstream) Bed Local scour due to flow obstruction, constriction, or channel irregularities. Headcutting. General bed degradation. Headcutting. Toe Local scour due to flow obstruction, constriction, or channel irregularities. Removal of noncohesive layers or lenses in stratified alluvium. Toe erosion and upper bank collapse. Middle of bank Local scour due to flow obstruction, constriction, or channel irregularities. Removal of noncohesive layers or lenses in stratified alluvium. Middle and upper bank scour by currents. Ice and debris gouging. Top of bank Local scour due to flow obstruction, constriction, or channel irregularities. Removal of noncohesive layers or lenses in stratified alluvium. Ice and debris gouging. Navigation or wind wave wash. TABLE B-1 Possible processes involved in erosion or scour by waves or currents

extent of the problem as local (limited to a segment of bank shorter than a few channel widths long) or general. If the problem is local, the user is asked to specify one of the following three processes as primary: • Toe erosion and upper bank collapse • Headcutting • Piping If the user selects piping, Greenbank asks if the piping appears to be due to steady seepage or due to sudden draw- down or return of overbank flooding to channel. If the problem is general (similar processes appear to be occurring for a considerable distance up- and downstream), the user is asked to categorize the problem as follows: • Toe erosion and upper bank collapse • General bank instability or susceptibility to mass slope failure A user who specifies slope instability is asked to specify whether or not the instability is related to subsurface water movement. GEOTECHNICAL STABILITY CHECK If the user specifies that the main reason for bank collapse is general bank instability or susceptibility to mass slope fail- ure, then Greenbank runs a simple geotechnical stability check. First, the user is asked to specify the type of bank material: • Sand • Cohesive soil • Sandy soil • A mixture of sand and clay • Alternating sand and clay layers. • Gravelly • Noncohesive materials coarser than gravel • Resistant bedrock The user is also asked to provide the bank slope, bank height (H), angle (β), soil density (γ), friction angle (φ), and cohesion. The following steps are then used for a preliminary geotechnical stability check: If the user selects sand as the bank material type, Green- bank asks if seepage (subsurface water movement) is a fac- tor in slope instability. If seepage is not a factor, and if bank slope > 35 degrees, an advisory is added to the comments that appear at the end of the run, “There is a potential mass instability problem at the site. Possible solutions include techniques that involve flattening the slope, providing internal reinforcement, or supporting the slope with a lateral structure.” 43 If seepage or drawdown is a factor and if bank slope > 20 degrees, then the advisory reads, “There is a potential mass instability problem at the site. Possible solutions include techniques that reinforce the slope, flatten the slope, support the slope with lateral struc- ture, or improve subsurface drainage.” If the user selects cohesive soil as the bank material type, Greenbank computes an allowable bank slope angle βcrit using these relationships: Ns = H γ/c βcrit = −25Ns + 190 where Ns is the stability factor and βcrit is the square root of the angle beta. This formula was obtained by fitting a linear regression to published tabulated values.1 If the computed βcrit > β, then the following advisory appears: “You have indicated that general bank instability is one of the primary erosion processes operating on your site. How- ever, simple stability checks indicate that the bank height, slope and soil type you have described should be stable. You may continue, but you may wish to use the back or restart buttons to revisit previous questions.” If the user specifies the bank material is a sand-clay mix- ture, Greenbank follows a procedure similar to the one for clay but uses the following relationship for Ns. Ns = [0.056684+0.0048688*SQRT(β)*ln(β) −0.027777262*SQRT(φ)]−1. This relationship was obtained by fitting a nonlinear regression function to published values1. Then Hcrit = Ns(c/γ), and if H < Hcrit, then the following advisory is displayed: “You have indicated that general bank instability is one of the primary erosion processes operating on your site. How- ever, simple stability checks indicate that the bank height, slope and soil type you have described should be stable. You may continue, but you may wish to use the back or restart buttons to revisit previous questions.” If the user indicates the bank is alternating sand and clay layers then the following advisory message appears: “You have indicated that general bank instability is one of the primary erosion processes operating on your site. Green- bank normally checks bank stability using bank height, angle and soil properties. However, such simple analyses are not 1 Journal of the Soil Mechanics and Foundations Division, American Society of Civil Engineers, Vol. 97, No. SM1, January 1971, pp. 22-23.

possible for complex stratigraphy (alternating layers of cohesive and noncohesive soils). You may wish to consult a geotechnical engineer for allowable bank heights and angles or run the ARS bank stability model after carefully studying the documentation. You may also use the back or restart but- tons to revisit previous questions.” No simple checks are run if the user specifies gravelly banks or noncohesive materials coarser than gravel. If the user specifies that the banks are resistant bedrock, the fol- lowing message appears: “You have indicated that general bank instability is one of the primary erosion processes operating on your site. How- ever, you have also indicated the banks are composed of resis- tant bedrock. It is very unusual for bedrock banks to exhibit general instability. You may continue, but you may wish to use the back or restart buttons to revisit previous questions.” ALLUVIAL STREAM TYPE AND EROSION RISK Elements of a simple stream classification system have been incorporated into Greenbank as an additional tool for assessing the likelihood of significant site erosion. Green- bank queries the user for values of several descriptive vari- ables (for example, flow habit, bed material, bank material, planform, location and size of bars, channel width, and so forth) using a series of multiple-choice questions with largely qualitative answers. These responses are used to place the candidate site in one of five stream type categories defined by Brice et al. (1978).2 If the site does not fit criteria for any of the Brice categories, it is classified as an unknown type. The five Brice stream types are used to further categorize the site as high, medium, or low erosion risk. Bed- and bank-protec- tion techniques are then eliminated if they are not judged appropriate for the erosional regime of the site. A similar approach is used to categorize the site according to the incised channel evolution model (CEM) developed by Schumm et al. (1984)3 (see Figure B-1) and Simon (1989).4 A stream reach is classified into one of five evolutionary phases or, if none of the phases seem to fit, as a reach where the CEM does not apply. Again, these results are used to clas- sify the risk of instability. CEM stages I, II, III and IV are classified as high erosion risk, while stages V and VI are low risk. Sites that do not seem to fit or that exhibit none of the symptoms of incision upon which the CEM is based are clas- sified as low risk. 44 BUDGET The user is asked to input the maximum acceptable price for initial construction. However, this input is not a dollar amount but a ratio that represents the price relative to the price for protecting the site with stone riprap blanket. The actual input is therefore a number between 0.5 and 20 that represents the price the user is willing to pay divided by the cost for riprap revetment applied from bank toe to bank top at the site in question. Maintenance effort may be measured in monetary or other terms. The user is asked to specify the maximum level of maintenance that can be provided in qualitative terms: mini- mal, moderate, or high. MISCELLANEOUS INPUTS Greenbank asks if the user wishes to compare hydraulic loading at the site with criteria for the techniques under con- sideration. Local velocity, shear stress, or both may be eval- uated, depending upon available criteria. The user is also asked if additional land loss (due to contin- uing erosion or bank grading) would be acceptable at their site. The user is asked for an assessment of the hazard, or con- sequences, of failure. Choices are extreme (almost certain loss of human life), severe (possible loss of human life and almost certain significant loss of adjacent structures), mod- erate (possible loss or severe damage to adjacent structures), and light (the probability of loss of life or severe damage to adjacent structures is very small). TECHNIQUE SELECTION The Greenbank system examines each of the techniques using the inputs described above by comparing the user- supplied values with those in a large spreadsheet, or matrix, that contains a row for each technique. Suitability of each technique is encoded within the matrix as follows: The matrix contains a column for each of the 11 environ- mental attributes and a column for each of the 11 erosion processes. Entries in the environmental attribute columns are either 0 (the technique does not contribute positively to the attribute), 1 (the technique has potential for a mild positive impact on the attribute), or 2 (the technique generally has a major, pos- itive effect on the attribute). For purposes of this selection system, simply controlling erosion generally does not con- stitute positive contribution. Entries in the erosion processes columns are either 0 (the technique does not address the process) or 1 (the technique does address the process). The matrix also contains a column giving estimated unit cost relative to riprap stone blanket. 2 Brice, J. C., et al. Countermeasures for Hydraulic Problems at Bridges. Report No. FHWA-RD-78-162, FHWA, Offices of Research and Development (1978). 3 Schumm, S. A., Harvey, M. D., and Watson, C. C., Incised Channels: Morphology, Dynamics and Control. Water Resources Publications, Littleton, CO (1984). 4 Simon, A. “The discharge of sediment in channelized alluvial streams.” Water Resources Bulletin, Vol. 25, No. 6, 1989, pp. 1177-1188.

The matrix contains a column entitled “Level,” and each technique is rated as follows: Level I—well established and widely used, well docu- mented (good performance and monitoring data avail- able), reliable design criteria based on lab/field studies, numerous citations and case studies in technical litera- ture, cost data available from variety of sources. Level II—used often but lacks the level of detail, qual- ity of information, and reliability that characterizes 45 Level I, little or no long-term monitoring, fewer case studies and citations in technical literature, cost data scarce or less certain. Level III—emerging, promising technique. Does not have the track record and level of information charac- terizing Level I or II. No field or laboratory design or test data, no long-term monitoring or performance data, very few literature citations or case studies, no reliable cost data. Figure B-1. Schumm’s Channel Evolution Model

Table B-2 summarizes the attributes of the three levels. The matrix contains a column indicating the potential for additional bank erosion occurring after the technique is installed. For example, intermittent techniques like bend- way weirs or bank barbs often create “scalloped” banklines due to local erosion between structures. Values of 0, 1, or 2 are assigned for no, moderate, or strong potential, respec- tively. Values of –99 are found in rows for techniques where this aspect is controlled entirely by site-specific characteristics. The matrix also contains columns for allowable shear stress and velocity. An adjacent column provides the source for these data (numbers for literature citations in a numbered reference list). If no critical velocity or shear stress values were found in the literature, the entries are –99. Values of 3.5 m/s and 2.5 m/s appear in rows corresponding to structures built with angular and rounded stone, respectively. Clearly these values depend on the size of the rock used, but these values were adopted as 46 they correspond to the largest size material commonly used for stream and river bed and bank erosion control.5 The matrix also contains a series of columns for several key reach characteristics as follows: The matrix contains columns for each of nine key vari- ables describing reach morphology and other site character- istics. Each technique is given an integer score for each vari- able. The nine variables are shown as headings in Table B-3, which also provides an explanation of what the integer scores in the matrix mean. Treatment Level Assignment Criteria I II III Frequency of Use Widely and frequently Occasional and more limited use Infrequent use in very limited areas Availability and Reliability of Lab/ Field Test Data Good... abundant and reliable data Fair... more limited and less reliable Poor... little or no data available, mostly anecdotal Performance and Monitoring Info Good... long term and well documented Fair... short term and less reliable Poor... little to none available Literature Articles and Case Studies Many... in well regarded journals and agency publications Some... few if any case studies Few... mostly fugitive and obscure publications Availability and Reliability of Cost Data Good...detailed unit costs from several different sources and locations Fair... less detailed and fewer sources Poor... little available and of limited applicability used TABLE B-2 Treatment levels 5 D50 = 0.75 m using approach of Maynord (1993) in Escarameia (1998) p. 40. Maynord, S. T., “Corps Riprap Design Guidance for Channel Protection.” In River, Coastal and Shoreline Protection: Erosion Control Using Riprap and Armourstone, C. R. Thorne, S. R. Abt, F. B. J. Barends, S. T. Maynord, and K. W. Pilarczyk. (eds.). John Wiley & Sons, Ltd., Chichester, U.K. (1995) pp. 41-42. Escarameia, M., River and Channel Revetments. Thomas Telford, Ltd., London (1998).

Entry in matrix Flow habit Channel width Flood plain widtha Bed material Bank material Braiding Stage of incision Maintenance requirements Erosion risk 1 < 15 m < 2Wb Silt to sand Cohesive to noncohesive sandy Not suitable for a braided stream No incision Low Suitable only for sites with low erosion risk 2 Ephemeral or intermittent < 50 m More than 2W but less than 10W Sand to gravel Cohesive to noncohesive gravelly Possibly suitable for a braided stream Stage VI or no incision Moderate Suitable for sites with low to moderate erosion risk 3 Perennial or no limitations < 500 m > 10W Gravel to cobble Cohesive to noncohesive materials coarser than gravel Suitable for a braided stream Stage V, VI or no incision High Suitable for all sites without respect to risk 4 > 500 m > 2W Cobble to boulder No limitations Stage IV, V, VI or no incision 5 > 15 m Silt to gravel Stage III, IV, V, VI or no incision 6 No limitations Gravel to boulder 7 Sand to cobble 8 a Area flooded by 50 to 100 year event. b W = active channel width. No limitations No limitations TABLE B-3 Explanation of matrix scores for site description variables. The Greenbank master matrix contains a row for each erosion control technique. Each technique is given an integer score (shown in first column of this table) for each of the site variables (bold faced in this table). Cells shaded dark gray represent integer scores that do not appear under the given heading

EVALUATION OF A GIVEN TECHNIQUE Each of the techniques contained in the Greenbank master matrix is assigned a numerical score that represents the suit- ability of the technique for the user’s project. Initially, all scores are zero. For each technique the system computes a score as follows: If an environmental attribute rated as very important or somewhat important has a score in the matrix > 0, the system adds (the entry in the matrix/importance of the attribute) to the score of the technique. Matrix entries are 0, 1, or 2, while importance values are 1, 2 or 3 as shown in Table B-4. If the maximum relative cost specified by the user is greater than or equal to the relative cost in the matrix, the sys- tem adds the quantity (1/relative cost) to the score. If the rel- ative cost is more than the user-specified maximum, then the system adds the quantity (budget − relative cost), which will be a negative number, to the score. If an erosion process that the user rated as important has an entry of 1 in the matrix, the system adds 5 points to the score of the technique. If an erosion process rated as impor- tant has a value of 0 in the matrix, the system subtracts 100 points from the score. If no additional land loss is acceptable and if the technique is likely to allow some additional erosion to occur after it is installed, the system subtracts 100 from the score. If addi- tional land loss is acceptable and if the technique will require slope flattening to create a slope more gradual that the max- imum recommended slope for the technique, the system sub- tracts 10 points from the score to separate techniques that require bank shaping from those that do not. The system asks if the user would like to compare the hydraulic loading for the site in question with published 48 allowable values for the techniques under consideration. A worksheet is available that provides computational assistance in generating velocity and shear stress esti- mates. After this, the system asks for either the design shear stress or velocity. If the input shear or velocity exceeds the tabulated value in the matrix, 100 is subtracted from the score. Therefore the score for the ith technique is given by: where Si = score for the ith technique. EEi,k = score indicating effectiveness of the ith technique in enhancing the kth environmental attribute (either 0, 1, or 2). EIi,k = score indicating the user-specified importance of the kth environmental attribute at the site in question (either 1, 2, or 3). Bi = term based on the unit cost of ith technique relative to unit cost for ripap blanket. Bi = 1/relative cost if the relative cost is less than the user’s budget. If the relative cost is more than the user’s budget, Bi = budget − relative cost. EPi,k = score indicating the effectiveness of the ith tech- nique in addressing the kth erosion process. If the erosion process has been rated as important by the user and if the ith technique addresses that process, EPi,k = 5. If the ith tech- nique does not address the kth process and it has been rated as important, EPi,k = −100. AEPi = score indicating if the ith technique may result in additional land loss due to bank shaping or erosion after con- 1 9∑+ + = , H SFi i k k S EE EI B EPi i k i kk i i k k = ⎡ ⎣⎢ ⎤ ⎦⎥ ⎡ ⎣⎢ ⎤ ⎦⎥ + + = = ∑ , , , 1 11 1 11∑ + +( * )AEP AEA Hi i TABLE B-4 Values added to technique score based on environmental attributes of interest and the effectiveness of the technique in addressing the given attribute (shaded area) Value in matrix for effectiveness of technique a Importance of environmental attribute Importance score 0—no effect on this attribute 1—mild positive effect 2—major positive effect Very important 1 0 1 2 Somewhat important 2 0 1/2 1 Not important 3 0 1/3 2/3 a Values are computed by dividing the value in the matrix by the importance score.

struction. If there is potential for some additional erosion, AEPi = −100, otherwise, AEPi = 0. AEA = score indicating if additional land loss is acceptable at the site in question or not. If so, AEA = 0, if not AEA = 1. Hi = score indicating the capability of the ith technique to withstand design hydraulic conditions. If the system contains an estimate of allowable velocity or shear for the technique and if the design shear or velocity for the site in question exceeds the allowable, then Hi = −100. Otherwise, Hi = 0. SFi,k = score indicating the suitability of the ith technique for application to sites with conditions specified by the kth site factor, as described in Table B-3 above. If the technique is not suitable for the specified site condition, then SFi,k = −100, otherwise, SFi,k = 0. Reporting Results For each technique with a total score > −100,000, the fol- lowing formula is used to adjust the total score so that it falls between 0 and 10: Adjusted score = 10*(total raw score) / [(2*(number of environmental issues of interest) + 5*(number of significant erosion processes) +5)] The denominator of the right hand side of the above expression represents the maximum score a technique can receive. The first term allows for the fact that 2 is added to the total raw score for each important environmental issue that is fully addressed by the technique (Table B-4). The sec- ond term allows for the fact that 5 is added to the score for each significant erosion process that is fully addressed by the technique, and the last term represents a maximum increase that can occur in total raw score due to cost factors. 49 A similar approach is used to obtain an adjusted score for the environmental performance of each technique. Adjusted scores are converted to letter grades using the scale in Table B-5. All techniques with grades of D or better (based on total score) are added to a list of recommended techniques. The list is sorted from highest-scoring techniques to lowest. If no techniques receive scores greater than F, the system displays a message, “Based on the information you have provided, Greenbank is unable to recommend any environmentally sensitive channel- or bank-protection techniques. You may wish to reconsider some of your responses. You may inspect and change your inputs by clicking on the back button. Press OK to end this run.” If one or more techniques receive grades higher than F, the system displays the name and a brief description of the highest-scoring technique. The brief description includes the letter grades awarded to the technique and its unit cost rela- tive to riprap blanket. The user is then given four choices: 1. See next highest-scoring technique, 2. See a list of techniques suitable for combination with the recommended technique, 3. See a list of all recommended techniques, or 4. See a list of all of the techniques that are not recom- mended. Selection of option 1 produces the name and a short description of the next technique, along with a listing of the same four choices unless there are no other techniques in the list of primary recommendations. Option 2 is provided because best practice usually involves a combination of erosion control techniques. Green- bank suggests primary techniques that address the important erosion processes and address environmental issues of inter- TABLE B-5 Relationship of adjusted scores to letter grades Adjusted Score Range Letter Grade > 8 8 > adjusted score > 6 B 6 > adjusted score > 4 C 4 > adjusted score > 2 D < 2 A F

est. However, other techniques that are compatible with the primary technique may be applied at the same site in order to enhance the net environmental outcome. For example, lon- gitudinal peaked stone toe is effective in controlling toe ero- sion by current or waves, but aquatic habitat may be enhanced by adding spurs or vanes to the toe protection. If the user requests a list of techniques suitable for combi- nation, another large matrix is searched. This matrix is used in a fashion very similar to the first selection matrix, but the procedure differs in three important ways. First, erosion processes are not considered, because it is assumed that the primary technique will provide erosion control. Second, costs are not considered. Third, the matrix contains additional columns that indicate which techniques are compatible. How- ever, most of the site variables (for example, channel width and bank material) are considered. Each row in the matrix represents a technique and there are also columns for each technique. A small excerpt from the matrix is shown in Table B-6 above. Primary techniques are shown as column heads, 50 while techniques that might be added to the primary technique for superior environmental performance are shown in the first column. Entries of 1 indicate compatibility, and entries of 0 indicate incompatibility. These entries were composed based on experience and professional judgment. Table B-6 shows that vegetated earthen spurs might be added to coir rolls to improve overall environmental effect, but they are ruled incompatible with vanes (they are too similar to vanes). Selection of option 3, “See a list of all recommended tech- niques,” provides the most complete set of information. Many of the key inputs are echoed, along with Greenbank’s evaluation of the Brice alluvial stream type and erosion risk. A short description of each recommended technique sorted from highest to lowest score is provided. Links are provided to additional information screens. For example, all tech- niques that involve vegetation are linked to screens giving information about soil compaction, plant handling, propaga- tion, and irrigation and to a document providing information about effects of plants on channel flow conveyance. Secondary technique Vegetated earthen spurs s Vanes Bendway weirs Large woody debris structures Weirs or check dams Longitudinal dikes with toe spurs Longitudinal peaked stone toe Coir rolls Vegetated gabion basket Vegetated earthen spurs 0 0 0 0 0 0 0 0 1 1 Spur dikes 0 0 0 1 1 1 Vanes 0 0 0 1 1 1 Bendway weirs 0 0 0 1 1 1 Large woody debris structures 0 0 0 0 1 0 Weirs or check dams 0 0 0 0 1 1 Longitudinal dikes with toe spurs 0 0 0 1 0 0 Longitudinal peaked stone toe 0 0 0 0 0 0 Coir rolls 1 1 1 1 0 0 Vegetated gabion basket 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 Spur dikes TABLE B-6 Excerpt from matrix used by Greenbank to suggest secondary techniques to combine with primary recommendations