Slope Matting: An Effective Solution for Erosion Control and Vegetation Establishment
1. What is Surface Mulch?
Surface mulch is the most effective, practical means of controlling erosion on disturbed areas before establishing vegetation. Mulch protects the soil surface, reduces runoff velocity, increases infiltration, slows soil moisture loss, helps prevent soil crusting and sealing, moderates soil temperatures, and improves the microclimate for seed germination.
2. Benefits of Organic Mulch
Organic mulch such as straw is effective for general use where vegetation is to be established. Straw mulch is most effective when it has been anchored with matting, crimping or a tackifier to prevent its movement. In recent years a variety of mats and fabrics have been developed that make effective mulches for use in critical areas such as waterways and channels. Various types of tacking and netting materials are used to anchor organic mulches. Netting is generally not effective when used alone.
3. Adhering to TN Requirements
In accordance with Tennessee’s requirements, the application of temporary or permanent stabilization must be initiated within 14 days to disturbed areas of a site where construction activities have temporarily or permanently ceased.
4. Addressing Limitations
While surface mulch provides significant benefits, it is important to recognize its limitations. Mulch is not intended to withstand the shear stress of concentrated flow; therefore, mulching a ditch must be accomplished in conjunction with other velocity reducing measures such as check dams or through the use of an engineered ditch lining material such as a turf reinforcement mat.
5. Maintenance for Long-Term Erosion Prevention
Maintenance of a good cover of mulch is one of the most effective erosion prevention measures because it helps prevent movement of the soil thereby reducing the need for sediment control measures. Maintenance of mulch can include but is not limited to applying more mulch where it has blown or washed away, securing the mulch through such actions as crimping or diverting run-on storm water from the mulched area to prevent future wash-outs.
6. Rolled Erosion Control Products (RECPs)
Rolled erosion control products (RECPs) are manufactured sheets of mulch materials (e.g., straw, coir, wood fibers, curled wood, etc.) that are bound into netting composed of either photodegradable synthetic or natural materials. They are usually delivered to a construction site in rolls which are then installed as a protective covering designed to protect soil and hold seed and mulch in place on slopes and in channels so that vegetation can become well established.
RECPs can be applied to steep slopes where erosion hazards are high and conventional seeding is likely to be too slow in providing adequate protective cover. RECPs shall be applied to cut or fill slopes of 2.5:1 or steeper with a height of 10 feet or greater in need of protection during establishment of temporary or permanent ground cover.
7. Importance of Ground Contact and Netting Considerations
Good ground contact is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion. It is preferred that loose woven netting made with natural fibers be used. Most netting used with blankets is photodegradable, meaning they break down under sunlight (not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation has established, sunlight does not reach the mesh. It is not uncommon to find non-degraded netting still in place several years after the installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting. Biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a fiber mesh and stitching which may last up to one year.
Conclusion
Surface mulch plays a vital role in erosion control and vegetation establishment. By leveraging the benefits of organic mulch, adhering to regulatory requirements, and utilizing additional erosion control measures like RECPs, we can build a sustainable approach to land management. Through careful implementation and maintenance, we can protect our environment and promote the successful growth of vegetation.
Reference:
Erosion & Sediment Control Handbook (Tennessee Department of Environmental and Conservation – TDEC)