Soil erosion is evident in so many landscape situations and the environmental impact can be significant. When a Landscape Architect encounters a channel, stream or drainage ditch, sediment control becomes an important feature, especially in the face of current Clean Water Act regulations. Rolled erosion control products (RECPs) can be a cost-effective way for contractors to handle soil stabilization until vegetation establishment, or to enhance the strength of the native soil. One critical factor the Landscape Architect must predict is the time needed for vegetation establishment.

Installation of erosion control materials is fairly straightforward. The manufacturers and distributors of these products offer a wealth of information about installing these products. Contact them and use their expertise liberally during installation. It is in their best interest to give you sound advice on proper installation techniques on the erosion control products that they manufacture. Their advice may also save the owner money.

Tools of the Trade - Rolled Erosion Control Materials Defined

What are rolled erosion control products (RECPs)? Rolled erosion control products consist of either organic or synthetic materials fabricated into a mat or blanket designed to be rolled over a prepared surface and fastened to the soil. RECPs hold soil in place while vegetation is established. There are four basic types of rolled erosion control products:

Erosion control nettings (ECN) – A planar woven natural fiber or extruded geosynthetic mesh used as a component in the manufacture of RECPs or separately as a temporary degradable RECP to anchor loose fiber mulches.

Open-weave textiles (OWT) – A temporary degradable RECP composed of processed natural or polymer yarns woven into a matrix and used to provide erosion control and facilitate vegetation establishment.

Erosion-control blankets (ECB) – A temporary degradable RECP composed of processed natural or polymer fibers mechanically, structurally or chemically bound together to form a continuous matrix. Netting types can be matched to the job site requirements.

When installing a RECP in a channel, the RECPs should be unrolled in the direction of water flow. First the RECP is deployed in the channel bottom. It is desirable to minimize the number of seams that are placed on the bottom of the channel.

Turf reinforcement mats (TRM) – A long term non-degradable RECP composed of UV stabilized, non-degradable, synthetic fibers, nettings and/or filaments processed into three dimensional reinforcement matrices designed for permanent and critical hydraulic applications where design discharges exert velocities and shear stresses that exceed the limits of mature, natural vegetation. TRMs provide sufficient thickness, strength and void space to permit soil filing and/or retention and development of vegetation within the matrix.

RECPs work by holding soil in place while seed germination and vegetation establishment occurs. The length of time a RECP will work depends upon product composition, geographic location in which it is used and the amount of sunlight, rain and climatic conditions the product is exposed to.

Staples and Stakes

The second material choice that needs to be made is what type of staple is appropriate for the project (see chart on page 24). The standard anchoring device for temporary degradable RECPS has been 11 gauge wire staples. Soil, site conditions and type of RECP being installed will affect which staples should be used. In sandy soil conditions longer, wider staples may be necessary to provide sufficient fastening of the RECP to the ground. Staples typically range from six inches to 24 inches in length with a one-inch to two-inch crown.

Long term non-degradable RECPs are usually used on sites requiring more aggressive soil erosion control and reinforced root systems. Hence, these materials usually require a stronger anchoring system. Wire staples, metal pins with washers, plastic pegs, rebar, and wooden stakes are often used in these instances. When using wooden stakes, pressure treated wood should be used in applications where longevity is required.

Specifying the type of RECP that should be used is another topic entirely. Proper installation of RECPs is critical for a successful project. Even the best products will not work properly if not installed correctly. Just how easy is the installation of erosion control materials? This article will provide directions on the ease with which rolled erosion control materials can be installed in channels.

Channel Step One – Site Preparation

The first step in installation of RECPs in channels is site preparation. Be sure the site is properly prepared before laying down any RECP. The site should be fine graded to a smooth profile and relatively free from all weeds, clods, stones, roots, sticks, rivulets, gullies, crusting and caking. Fill any voids and make sure that the channel is compacted properly.

Channel Step Two – Seeding

The second step in the installation process of RECPs on channels is to seed the area to be vegetated. Select a seed mix for vegetation adapted to the local geographical area taking into consideration site-specific soil conditions.

Always match the seed to site soil conditions for optimum germination, root system development, vegetation density, and long term functionality. Prior to RECP installation if the prepared seed bed becomes crusted or eroded, or if eroded places, ruts or depressions exist for any reason, the contractor should rework the soil until it is smooth and re-seed such areas which are reworked.

The seeding types may vary based on the water conditions expected immediately after installation. The types of seeds planted above the anticipated water line may differ from the seed planted below the anticipated water line.

Channel Step Three – RECP Deployment in the channel bottom.

When installing a RECP in a channel, the RECPs should be unrolled in the direction of water flow. First the RECP is deployed in the channel bottom. It is desirable to minimize the number of seams that are placed on the bottom of the channel. It is also necessary to prevent a seam from going down the center of the channel bottom or in areas of concentrated water flow.

When installing two RECPs side by side in a waterway the center of the RECP should be centered in the area of concentrated water flow. Install adjoining RECP’s away from the center of the channel bottom. When abutting RECP panels, follow the manufacturer’s recommendations. If the manufacturer recommends overlapping the RECP, the overlap will generally be two to four inches. Install a row of staples at two-foot minimums along the length of the offset center overlap.

The RECP must be secured at the beginning of the channel. The anchoring method recommended in the Federal Highway Administration’s proposed FP-03 Specifications is a six-inch by six-inch check slot dug perpendicular to the direction of water flow across the entire width of the channel. The RECP is laid in the check slot with 30 inches of the RECP extending upstream of the check slot. Stake or staple the RECP in the check slot on 12-inch centers. Backfill the anchor trench and compact the soil. Place seed over the compacted soil if necessary. Cover the compacted soil with the remaining 12 inches of the terminal end of the RECP. Staple or stake terminal end down slope of the anchor trench on 12-inch centers.

Channel Step Four - Check Slots

Check slots are recommended in the Federal Highway Administration’s proposed FP-03 Specification to be placed perpendicular to the flow direction across the entire width of the channel at 25-foot intervals and at the terminal end of the channel.

The check slots placed at 25-foot intervals can be done in one of two ways, depending upon the Engineers discretion and/or the manufacturer’s recommendations. One type of check slot is constructed by installing a double row of staples or stakes staggered and spaced four inches apart. Place the first row of staples or stakes four inches on center.

The second option is to put in a check slot six-inches wide by six-inches deep, secure the RECP in the upstream side of the check slot with staples or stakes on 12-inch centers. Flip the RECP roll on the upstream edge. Back fill the check slot and compact the soil. Continue rolling the RECP down stream over the completed check slot.

Channel Step Five –RECP Deployment on the Side Slopes.

Continue to roll the RECP along the channel bottom and side slopes in the direction of the water flow. As the RECP is installed from the channel bottom up the slope a shingle type installation is recommended with the up-slope RECP overlapping the lower RECP approximately two inches to four inches. Anchor the RECPs with a minimum staple pattern of one staple every 24 inches across the width and one staple every 36 inches down its length.

If the RECP needs to be spliced, be sure the RECP is "shingled" with the up-stream RECP overlapping the down-stream RECP. There should be four inches of overlap in a splice. Use a staple check slot to secure the overlap. Anchor the RECP placed at the top of the channel slope by rolling the RECP two feet past the toe of the slope. Secure with staples or stakes one foot on center across the RECP.

Channel Step Six – Terminal End

Secure the RECP at the terminal end of the channel with a check slot similar to the one made at the beginning of the channel.

Alternative Channel Installation

The RECPs on the slope can be installed vertically and installed approximately three feet onto the flat of the channel bottom. A check slot will be constructed in areas of concentrated water flow. On the slope allow for a two-inch to four-inch shingle type width overlap upstream to downstream.

On wet channel bottom and wet side slope applications a portion of the horizontal RECP at the toe shall be installed up onto the channel side slope approximately a minimum of three feet above the high point of scour. The RECP installed from the crest down the slope should be installed over the toe of the side slope to allow shingle type protection. An additional row of staples should be placed every 24 inches at the side slope junction along the length of the installation.

You may have already be using some of these materials and may have used trial and error to make them work. If you haven’t used RECPs in the past, contact any of the members listed as Directing Members on the ectc.org website. They will be happy to get you up and running in this field.

The need for expert installation cannot be over stressed. The products will work only as well as they are installed. Chose your Contractors carefully and ensure that they have experience installing these materials successfully.