TURF REINFORCEMENT MAT (TRM)
Turf reinforcement mats (TRMs) are synthetic, non-degradable soil and seedbed covers of variable thickness designed to provide short-term protection against raindrop and wind erosion, permanent support for vegetation on slopes, and permanent armoring and vegetation support for ditches, swales, and channels. They are composed of UV stabilized, synthetic fibers, filaments, nettings and/or wire mesh that are processed into three dimensional reinforcement matrices, a design that serves permanent and critical applications where site conditions exceed the limits of mature natural vegetation. TRMs provide sufficient thickness, strength and void space to permit soil filling and/or retention and the development of vegetation within the matrix. TRM manufacturers are also providing flexible growth media integrated into the mat.
TRMs, like erosion control blankets, are part of the larger group of rolled erosion control products. TRMs are used to provide temporary cover for bare soil, long-term support for vegetation, and permanent armoring against shear stress caused by flowing water. TRMs share many attributes with erosion control blankets, but are non-degradable, erosion protection aids. After installation, vegetation and soil provide shielding from the sun and the elements, preserving the synthetic components and maintaining the structural integrity of TRMs.
TRMs can be used to prevent erosion and support vegetation on a wide variety of site slope and drainage features. They are typically used in conjunction with grass and other seed on steep slopes, in higher velocity ditches and channels, along shorelines, and for scour prevention and armoring at culvert outlets. Some of the thinner TRMs are designed to be placed directly over seeded bare soil areas, while some thicker open-celled/open weave products may be staked down first, then seeded, and then covered with a thin layer of topsoil. Because of the many different types of products, manufacturer’s specifications regarding use, installation, anchoring device selection, and maintenance must be followed precisely.
TRMs are used to support permanent vegetation on longer, steeper slopes (e.g., more than 100 feet and 3H:1V) and in steeper, higher velocity ditches and channels (e.g., more than 10H:1V; velocities of up to 15 feet per second, and shear stress of up to 10 pounds per square foot). They are typically used when slope and channel conditions exceed the capabilities (e.g., manufacturer’s requirements) of erosion control blankets, but are not severe enough to justify terracing or retaining walls in slope applications, or harder armoring (e.g., articulated block, riprap, pavement, etc.) within channels.