FAQ

General Questions

Is soil in-filling necessary with any of North American Green’s RECPs? No. North American Green recommends surface application of all the RECPs we manufacture. A layer of soil atop an erosion control blanket or matting does nothing more than expose the in-filled soil and seed to erosion. Surface application provides immediate erosion control by protecting the underlying soil and seed against erosion in a single application. Surface applications also eliminating the need for heavy equipment movement over the matting for soil placement, which may potentially damage the matting.

What type of fastener and fastener pattern should I use for RECP installation? North American Green produces fasteners made of steel, biodegradable plastic (Bio-STAKE™), and hardwood (Eco-STAKE™), each in differing lengths, for securing our erosion control products during installation. The type of fastener you need and the pattern at which it is applied, will depend on specific site conditions. North American Green’s ECMDS will specify the correct staple pattern to use based on the information you input for a specific slope or channel. The matrix below is a generalized guide to fastener selection. 4” BioSTAKE 6” BioSTAKE 6”EcoSTAKE 12” EcoSTAKE 100% biodegradable plastic. For use in ecologically sensitive areas or other areas where staple degradation is preferred in less three years. Use with cohesive soil types. 100% biodegradable plastic. For use in ecologically sensitive areas or other areas where staple degradation is preferred in less three years. Use with less cohesive, loose soils and sand. 100% biodegradable hardwood. For use in ecologically sensitive areas where functional longevity of 3-5 years is required. Use with cohesive and hardpan type soils. 100% biodegradable hardwood. For use in ecologically sensitive areas where functional longevity of 3-5 years is required. Use with very loose soils and sand. 18” EcoSTAKE 24” EcoSTAKE 6” Steel Staple 8” Steel Staple 100% biodegradable hardwood stake. For use with the SedimentSTOP biodegradable sediment control product to secure the product in normal applications. Use with cohesive to slightly loose soils and standard 9” diameter roll sizes. 100% biodegradable hardwood stake. For use with the SedimentSTOP biodegradable sediment control product. Use where larger than normal (>9”) rolls are being installed or soil condition are very loose and/or sandy. Manufactured individually and in cartridge form. Cartridge staples are for use with the SureLock staple installation tool to reduce installation time. Use in areas where soils are not excessively hard or rocky. Manufactured individually for use in more extreme conditions than the 6” wire staple. Packaged loosely, no specialized installation tools needed. Use with somewhat loose soil.

What is a Composite Turf Reinforcement Mat (C-TRM) and how does it differ from a traditional TRM? A C-TRM is a type of mat incorporating a permanent three-dimensional net structure along with a matrix of randomly oriented fibers. The fiber matrix may be a degradable or non-degradable material such as coconut fiber, agricultural straw, polyporopylene, or a combination of materials. This fiber matrix increases the mat’s ability to provide immediate erosion control after installation while regulating moisture, heat and other plant growth factors at the soil surface to promote rapid vegetation establishment. As vegetation establishes through the matting it will be reinforced by the matting’s permanent three-dimensional net structure to provide permanent erosion protection. « Top

ECMDS Questions

What type of operating system does ECMDS utilize? North American Green’s ECMDS Version 4.3 is compatible with Windows 98 and higher operating systems.

Are CAD diagrams of installation procedures included within the software package? Computer-Aided Drafting (CAD) diagrams of slope, channel, and shoreline installation procedures and staple pattern guides can be viewed or installed from the main menu of ECMDS, the CD-ROM, or they can be downloaded from the Installation section of this web site. (View Slope Installation, Drainage Channel Installation, Shoreline Installation)

Using ECMDS, how do I select the most appropriate rolled erosion control product for my application? Both the Channel and Slope Modules of ECMDS offer a Quick Pick mode and a User Defined mode. In the Quick Pick mode the software will automatically pick the most suitable temporary (unvegetated) erosion control product given the design information about the slope or channel. You can also design using the User Specified mode which allows you to specify a permanent form of erosion protection (vegetation, reinforced vegetation, rock or concrete). The User Specified mode requires the input of more design variables concerning the type of vegetation to be established, developmental stages of the vegetation, permanent protection using a turf reinforcement matting, soil type, and composite channel linings.

Does ECMDS analyze temporary erosion control blankets in a vegetated state? No. Temporary erosion control blankets are designed to provide temporary erosion protection and assist in vegetation establishment through their functional life. Because of this, the software analyzes all the temporary blankets in an unvegetated state only.

After selecting the appropriate temporary protection for a slope or channel, do I need to conduct any additional analyses? Yes. In addition to analyzing a material for temporary slope or channel protection, you must also analyze a permanent type of erosion protection, such as established vegetation or reinforced vegetation. This is done by choosing Established Vegetation or the appropriate turf reinforcement matting as the permanent material type and then entering the required information concerning vegetation type, density, soil type, etc. If established vegetation or reinforced vegetation are not stable as permanent erosion protection changes in the channel’s design parameters may be needed.

What is the difference between a Material specification and a Project specification? The Material specifications are available to view or print at anytime, while the Project specifications may be viewed only after an analysis is completed. Material specifications provide information on the construction materials and process and physical properties (Supplemental Spec.). Project specifications contain unique information, such as potential soil loss and the type of material chosen, about the specific slope or channel for your design.

Can ECMDS be used to analyze the use of SedimentSTOP on slopes, in channels or along shorelines? Currently, ECMDS Version 4.3 is not capable of analyzing applications involving the SedimentSTOP sediment control material. « Top

Channel Design Questions

After running an analysis of a partially or fully vegetated channel, why are there two lines of data displayed under “Liner Results” on the output screen of the Channel Module? The program will analyze the stability of both the vegetation and the underlying soil. The upper line of data is reflective of the vegetation’s stability, whereas the lower line reflects the underlying soil’s stability. For instance, the analysis may show that while the underlying soil is stable, the established vegetation is unstable. In this case, should the design discharge occur, the vegetal parts (leaves, stems) above the soil surface or TRM may be broken and/or shredded by the flow but the underlying soil will not be excessively eroded (greater than 0.50 in (1.27 cm) soil loss). Likewise, the root system and regenerative parts of the plant will most likely remain functional as long as the soil around them is not washed away. The inverse condition can also occur. If the underlying soil is more erodible than the vegetation’s resistance to flow, or if the plants are widely spaced leaving areas of soil exposed, an unstable condition will be reported for the underlying soil while the vegetation will be displayed as stable. Should the design discharge occur under these conditions, the underlying soil is likely to be eroded away with the flow eventually undermining and removing the vegetation. In this instance, a three-phase analysis of reinforced vegetation with a product such as the SC250, C350, or P550 C-TRM should be performed.

The input screen of the Channel Module asks for a Manning’s ‘n’ value. What value should I use? If the Manning’s ‘n’ (roughness coefficient) box is left blank (recommended), ECMDS will automatically calculate a Manning’s ‘n’ for the given application. When the analysis is run, the appropriate Manning’s ‘n’ value will be determined by ECMDS and displayed in the liner results section. However, if you have a specific value you would like to use, simply input the value in the box. The pre-programmed roughness values will vary depending on the application, the products being analyzed, the height and density of vegetation, the depth of flow in the channel, and other factors. The roughness values for North American Green’s unvegetated products are derived from laboratory testing and cannot be altered by the user, whereas the roughness values for vegetation and rock are taken from the FHWA’s Hydraulic Engineering circular #15 and USDA’s Agriculture Handbook #667 and can be altered at your discretion. You will need to enter a specific value when you choose to analyze concrete.

How does ECMDSTM determine Manning’s “n” for various channel liners? Manning’s “n” is the roughness coefficient for the selected channel liner. It has been determined for all of North American Green’s temporary products through extensive laboratory testing and calculation. For permanent channel liners it is determined through Manning’s equation and Ven Te Chow’s iterative process. In calculation, the software will continuously run scenarios until the flow depth, discharge, velocity, channel geometry, vegetation retardance class, vegetation type, density, and roughness are in conjunction with the supplied inputs for the channel.

What is a Composite Channel Lining? ECMDS allows you the option of analyzing a channel lining with one type of liner in the bottom of the channel and another type on the side slopes—a composite design. A channel only needs increased protection against flow along its wetted perimeter (portion of the channel’s cross-section subject to flow). For example, if you have a channel with 6 foot long side slopes and your normal flow depth extends 2 feet up these side slopes, a turf reinforcement matting (TRM) may be necessary in the channel’s bottom and extended to the appropriate free board flow depth. The remaining area of the side slopes, above the TRM and water line, may be adequately protected with a temporary erosion control blanket. Using a composite channel design can bring significant cost savings while effectively controlling erosion and channel scour.

I am designing a channel around a 100 year, 24 hour storm. Should I input 24 hours as my peak flow period when analyzing this channel with ECMDS? Even though the storm you are designing around may last 24 hours, the channel will likely experience peak flow for a much shorter time. Peak flow is best determined by examining a hydrograph for the design storm (see graph). The peak flow period is represented by the crest of the hydrograph and only occurs for a short time (minutes). North American Green recommends using a design peak flow period representing 10% to either side of the hydrograph’s peak. For more information on hydrology and hydrographs, North American Green’s Technical Services Department, the U.S. Geological Survey, and the U.S. Army Corps of Engineers are excellent resources. Hydrograph for an Intermittent Channel « Top

Slope Design Questions

Is the annual R factor used in the slope module the annual precipitation impacting the area? Not exactly. The “Annual R Factor” is the rainfall/runoff factor from the Revised Universal Soil Loss Equation (RUSLE). The R factor is representative of both the amount of rainfall and the intensity of rainfall as summarized on an annual basis. Depending on what month is input for the “Beginning Month”, the software will calculate an “Adjusted R Value”. This adjusted value is reflective of the amount and intensity of rainfall occurring during the designated design period for a given location. Since the soil is most vulnerable to erosion immediately after being graded, the adjusted R value takes into account the effect of increased or decreased rainfall during a specific month.

Does the “Total Slope Length” input in the Slope Module refer to the horizontal or vertical length of the slope? The dimension needed here is the linear distance from the crest to the toe (top to bottom) along the slope face as shown in this diagram.

What is a segmented slope? For cost saving purposes, a slope can be designed as a segmented slope—using more than one material to cover different sections of the slope while ensuring the entire slope is protected. Because erosive forces are greater at the toe of the slope, a higher performance material may be needed in this section although a more modest material may be used on the upper sections of the slope. ECMDS allows you to experiment with differing slope length sections to find the most suitable combination of materials for your application.

Is the trenching described in the Installation Guide necessary for a correct installation? Yes. The trenching described in the Installation Guide is designed and recommended to prevent any migration of water beneath the RECP and the subsequent undermining that may ensue. Trenching is also very important to prevent strong winds from pulling the blanket or matting from the ground.

Why are there so many different RECPs manufactured by North American Green? Each site has unique design parameters including topographic relief, soil characteristics, and climatic variances affecting the rate and type of potential soil erosion. Some applications may need an RECP to stay in-place for only a short time, whereas other areas require permanent protection. North American Green manufactures 14 different RECPs, each designed to negate various levels of erosive force. The Erosion Control Materials Design Software (ECMDS®) is designed to assist in the selection the appropriate material for a particular slope or channel application. « Top