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Slopes are mostly natural landscape elements but can also be found in man-made structures. Highways, dams, levees, canals, and stockpiles are constructed by sloping the lateral faces of the soil because building slopes are generally less expensive than constructing walls. Many civil engineering and mining projects also include demolition and excavation, again leading to slope formation.

All slopes are subject to continuous erosion forces. Whether the slope has been recently formed as part of new development, or is in its original natural state, some form of erosion protection may be required.

Unprotected natural or constructed earthen slopes are a major point source erosion problem that can result in serious sediment flows to lower catchment sites, contamination of rivers and streams, water quality reduction, slope failure and slippage that often result in landslides, economic damage to property, and loss of life.

Erosion is basically the displacement of soil from one area to another. On slopes and embankments erosion is caused primarily by water, especially by heavy rainfall. Rain that falls onto the exposed ground dislodges soil particles which are then carried away down the slope by the flowing water. However, it is the resulting destabilization of slope that creates an even greater danger as rocks and trees roots become exposed.

There are several ways of controlling erosion on slopes and embankments.

The most effective, natural way to control soil erosion on slopes and embankments is to plant vegetation. Not only will the grass, fescue and leaves help to slow down raindrops as they fall, the roots of the plants will also help to hold the soil together, making it harder for water to wash it away.

Other than planting vegetation, there are also a variety of artificial solutions to control soil erosion on slopes. One of the cost-effective and straightforward solutions is to cover the slopes with Erosion Control Blankets (ECBs).

Erosion control blankets are also called erosion control mats depending on their specific purposes and materials. They work to fight soil erosion of several varieties and prevent any related damages while providing added soil stability. With proper placement, the mats will help keep sediment and topsoil from shifting until vegetation takes root, which naturally fights erosion.

The primary purpose of erosion control blankets is to keep soil from shifting or moving. They help stabilize soil particles and sediments, holding them in place to prevent sliding due to water, wind or other natural causes. By holding the earth still, these blankets also create an environment where new seed can take root. They keep the seed protected and covered and provide a stable area for it to begin growing while also allowing the air and water it needs.

These blankets typically come rolled like carpets, allowing developers to place and unroll them in their desired locations. Rolled Erosion Control Products (RECPs) are single or multiple layer sheets composed of natural / organic or synthetic material that is woven, sewn, bonded, or otherwise manufactured for placement on bare soil slopes. They have been described as a temporary, degradable products composed of processed natural or polymer fibers mechanically, structurally, or chemically bound together to form a continuous matrix to provide erosion control and facilitate vegetation establishment. Some of the most common materials include coconut fiber, wood excelsior, agricultural wheat straw, polypropylene blends and other synthetic fibers.

Types of Erosion Control Blankets

When it comes to erosion control, the type of mat to be used depends on the worksite and the conditions of the landscape. There are semi-permanent types made from a higher percentage of natural material, which will degrade over time. Permanent models are made with a higher density of synthetics, which are excellent for longer-term projects and applications. Blankets contain different thicknesses and blends of fibers.

1. Photodegradable Erosion Control Blankets

Photodegradable erosion control blankets typically have netting made from materials like plastic. The plastic contains UV stabilizers designed to stop functioning after a specific amount of time. After that happens, those parts of the netting break down under exposure to sunlight. The parts of the netting that are not exposed to sunlight, though, may take much longer to degrade.

2. Biodegradable Erosion Control Blankets

Biodegradable erosion control blankets are temporary and are designed to provide erosion control and assist in establishment of vegetation. These blankets are used to aid the plant’s ability to control erosion where it would be unable to do so alone. They aim to protect bare soils, mainly on slopes, from the impact of rain. While, they can also suppress weeds and can form a useful mulch layer, promoting seed germination.

Biodegradable erosion control blankets typically contain natural fibers rather than plastics. The fibers break down into the natural environment, so these blankets are an excellent choice for projects where minimal disruption to the natural environment is a high priority. Depending on their composition, biodegradable erosion control blankets may break down in a matter of months, or the process may take a few years.

3. Permanent Erosion Control Blankets

Permanent erosion control blankets provide the longest-term solution available. While the matrix may decompose, the blankets are designed not to break down at all. The common type of permanent erosion control blankets are Turf Reinforcement Mats (TRMs).

TRMs consist of various UV-stabilized, synthetics fibers and filaments processed into permanent, high-strength, 3-D matrices. Common examples include cuspated polyethylene meshes heat-bonded together, extruded monofilaments of nylon or PVC heat-bonded at their intersections, and crimped polyolefin fibers and other materials mechanically stitched between high-strength nettings. TRMs may also have supplemental degradable elements, including straw, coconut fibers, wood and other forms of natural fibers to help provide the best environment for immediate soil protection and encouraging new vegetation growth.

Though some TRMs also contain degradable components to supplement their permanent structures, all TRMs by definition have a permanent three dimensional structure with high-tensile strength that functions as a matrix for entangling plant roots, stems and soils.

Together, the TRM and vegetation form a continuous composite—a unified, living mat.

This synergism increases root systems’ lateral strength, reducing plant dislodgement under high-velocity, high-shear stress flows. The TRM’s permanent structure also functions to consolidate and protect the soils in which the plants are anchored, preventing soil from being stripped out of the vegetative cover and the resulting weakening of the root support. TRMs are often used in situations where the green alternative is preferred to hard armour.