An erosion control blanket is a temporary protective covering designed to stabilize exposed soil and encourage the establishment of vegetation. These blankets are typically made from organic fibers held together by a mesh netting, creating a structure that shields the soil surface from the physical impact of rain and wind. Their primary function is to mitigate soil loss and sediment runoff, particularly on steep slopes, newly graded areas, or along drainage channels where the soil is highly susceptible to erosive forces. By maintaining soil moisture and moderating surface temperatures, the blanket provides a protected microclimate that significantly enhances seed germination and promotes healthy root development.
Selecting the Right Blanket for Your Site
Blanket selection is determined by the site’s characteristics, specifically the angle of the slope and the expected velocity of water flow. Temporary blankets are composed of natural fibers like straw, wood excelsior, or coconut coir, each offering different longevity and strength. Straw blankets are suitable for gentle slopes (3:1 or milder) and typically degrade within 12 months. Excelsior (wood fiber) or coir blankets provide greater tensile strength and resistance to shear stress, making them the appropriate choice for steeper slopes up to 2:1 or areas with moderate to high water flow velocity.
The blanket’s construction, specifically the netting, further indicates its performance capabilities. A single-net blanket, featuring a mesh only on the top side, is the lightest and is best for flat ground or very mild slopes with low runoff. Double-net blankets sandwich the fiber matrix between two layers of netting, which significantly increases the blanket’s structural integrity and its ability to withstand higher forces. For the most severe applications, such as very steep hillsides or high-flow channels, a 100% coir blanket or a permanent turf reinforcement mat (TRM) is generally required due to their multi-year lifespan and superior durability.
Preparing the Ground Surface
Effective installation begins with preparation of the underlying soil, ensuring a smooth surface for the blanket to contact fully. All debris, including large rocks, tree roots, vegetation clumps, and construction materials, must be removed. The soil should then be finely graded to eliminate rills, gullies, or abrupt changes in contour that could prevent the blanket from lying flat against the earth.
A smooth surface is necessary to prevent water from flowing beneath the blanket, which could cause undermining and localized erosion. Before the blanket is unrolled, the entire area must be uniformly seeded and fertilized according to the chosen vegetation mixture. The blanket holds these seeds securely against the soil, protecting them from displacement by wind or water and retaining the moisture necessary for germination. This pre-seeding step allows the vegetation to establish immediately under the protective cover.
Step-by-Step Installation Process
Installation must begin with a secure anchor trench at the top of the slope or treatment area. This trench should be excavated six inches deep and six inches wide along the crest to prevent water from running over the top edge and eroding the soil beneath the blanket. The leading edge of the blanket is laid into the trench, secured with staples, and the excavated soil is then backfilled and firmly tamped down.
Once the anchor is set, the blanket is unrolled straight down the slope, following the direction of water flow, maintaining continuous contact with the prepared soil surface. The blanket must be relaxed and not stretched during unrolling to avoid tension that could lift it off the ground, a condition known as bridging. If the blanket does not conform to the soil’s contours, water can flow beneath it, rendering erosion control ineffective.
When multiple rolls are required, precise overlapping is necessary both end-to-end and side-to-side to create a continuous protective layer. Adjacent rolls should overlap by four to six inches along the sides, with staples driven through the material to bind them. The end-to-end overlap must be installed in a shingle-style manner, where the uphill blanket overlaps the downhill blanket by four to twelve inches. This arrangement ensures water flows smoothly over the seam, preventing penetration and erosion underneath.
The final step involves securing the entire blanket with metal staples or biodegradable wooden pegs to ensure firm contact with the soil. For the main body, staples should be inserted at a density of two to three per square yard, or every two to three feet in a staggered pattern. This density must be increased significantly along all seams, edges, and in high-flow areas, requiring staples every 12 to 18 inches to resist hydraulic lift and sheer force. Staples should be driven flush with the surface, holding the protective matrix tightly until the vegetation’s root system stabilizes the soil.
Post-Installation Monitoring and Maintenance
After the blanket is fully secured, immediate maintenance involves an initial watering to settle the material onto the soil and activate the pre-applied seed and fertilizer. This initial moisture allows the fibers to swell slightly, which enhances the blanket’s ability to retain water and protect the underlying seed bed. Continuous monitoring of the installation is necessary, especially after significant rainfall events, until the vegetation is fully established.
Inspections should focus on the integrity of the anchor trench and the placement of the staples throughout the blanket’s body. If heavy rain causes water to undermine the blanket, or if staples have lifted, the affected area must be immediately repaired by re-tamping the soil and driving new staples. Any areas of significant erosion, such as rills forming beneath the material, require lifting the blanket, filling the void with new soil, re-seeding, and then firmly re-securing the blanket to maintain its continuous protective seal.