Degradation Rates of Woven Coir Fabric Under Field Conditions

Woven coir fabric is a biodegradable erosion control product that has become widely utilized in stream bank stabilization and soil bioengineering. Its primary advantages over non-woven coir, jute, or straw erosion control products are a high tensile strength and increased longevity, while still remaining cost-effective and easy to install. Fabric tensile strength provides initial bank stability while installed vegetation provides long-term resistance to erosional forces as fabric decomposes. Because woven coir fabric is often used on sites that experience high tractive forces that may also be difficult for vegetation establishment, the longevity of woven coir fabric is critical. Since little published data exists on actual rates of fabric degradation under field conditions, a study was undertaken in 1996 investigating installed longevity of 700 and 900 g/m² woven coir fabric. Samples of woven coir and qualitative site data were collected from 20 bioengineered stream banks projects constructed between 1989 and 1995. These samples were submitted to an independent geotextile testing laboratory for standardized ASTM tensile strength testing. To generate approximate degradation rates, tensile strengths of collected samples were then compared to test values of "new" fabric samples submitted by several coir suppliers.