Rolled Erosion Control Products

Each year, many communities in the U.S., Clark County included, experience torrential rainfalls and flooding. The resulting natural runoff of "stormwater" has an impact on the land and environment, and can sometimes cause significant damage. A major contributor to runoff problems is the "hardening" of our landscape. Impervious sidewalks, streets, parking lots and roofs increase runoff volume so much so that it exceeds the capacity of existing drainage systems. Unfortunately, many of man's attempts at managing storm water and controlling erosion have led to more problems.

It was once thought that "hard armor" materials such as rock riprap, concrete and asphalt were suitable for channels exposed to high water flows. This is not the case any longer. These materials have been found to inhibit water infiltration, reduce filtration of sediment and other potential pollutants, and increase runoff volumes. As a result, more water feeds into over-burdened streams and reservoirs at a faster pace.

What is rock riprap?
It is a blanket of graded rock placed on a shaped streambank surface which provides structural slope protection so that erosion can be slowed or stopped. This allows for the eventual recovery of natural vegetation.

Riprap, concrete and asphalt are also not very aesthetically pleasing, and in today's world of urban sprawl, aesthetics are becoming more important. Our "greenways" are becoming scarce, and this, in conjunction with a greater public environmental awareness and stricter water quality legislation, has engineers re-thinking the materials used to stabilize drainage channels. Although rock is a completely natural material, its appearance is hard like manmade pavements.

The need to replace the "hard armor" with something "softer" led to the manufacturing of rolled erosion-control products (RECPs) designed to drastically reduce the effects of wind, water and drought on newly reclaimed sites such as ditches, slopes and shorelines, and to provide long-term soil stabilization through the establishment and maintenance of vegetative cover.

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.
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.

How do you install a Rolled Erosion Control Product?

The length of time a RECP will work depends upon product composition, the location in which it is used, and the amount of sunlight, rain and climatic conditions the product is exposed to. The first step in installation is to consider those factors and decide which RECP fits:

Temporary degradable - A RECP composed of biologically, photochemically or otherwise degradable materials that temporarily reduces soil erosion and enhances the establishment of vegetation.

Long term non-degradable - A RECP composed of non-degradable materials that furnishes erosion protection and extends the erosion control limits of vegetation for the design life of a project.

After determining the RECP, the site is prepared. Weeds, clods, stones, roots, and sticks are removed and the land is graded to a smooth profile. This ensures full contact between the blanket and the soil surface.

The second step in the installation process of RECPs on slopes is to seed the area to be vegetated. The seed mix used should be for vegetation adapted to the local geographical area. The seed must also be suitable for the soil type.

Depending on the location in which it is being installed - in a channel, along a shore, or on a slope - the installation process of the RECP varies. Generally, however, the RECP is rolled out over the area and stapled to the ground with steel staples or wooden stakes. The seed and topsoil is therefore immediately protected from a large rainfall or drought.

Until the vegetation grows through the mats, the finished site should be inspected periodically, especially after significant rains, and any damaged materials repaired or replaced. When conditions are right for germination, the vegetation will grow through the mats, reducing or eliminating maintenance.

For more information on rolled erosion control products, visit these links:

Erosion Control Technology Council (ECTC)

International Erosion Control Association

North American Green

 

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