This report presents the results of a two-year field study on the performance of erosion control products under natural and artificial rainfall conditions. Vegetation, runoff, and erosion data were collected at a newly constructed roadway. Runoff and erosion data were gathered using natural rainfall events and using a rainulator to spray water onto the surface. Treatments included a wood fiber blanket, a straw/coconut blanket, a straw blanket, a bonded fiber matrix, and disk-anchored straw mulch for natural rainfall events. For the rainulator events, a bare soil treatment also was used. Biomass, percent cover, and species composition also were measured at the research site. Five runoff events from natural rainfall were measured and revealed very little difference in sediment production between the straw, straw/coconut, and the wood fiber blankets. These blankets had approximately one-tenth the erosion that was observed for the straw-mulch plots. The impact of the erosion control treatment was substantial for early season artificial events. The sediment loading rates from the blankets and bonded fiber matrix plots were roughly one hundred times smaller than the bare soil plots and 10 times smaller than the straw mulch plots. For late season events, the erosion from these products were approximately one-half of that from straw mulch treatments.
The re-establishment of native plant species has been a principle objective of managers of roadside vegetation for many years. However, the establishment of native species, especially on the near inslope of roadsides has always been problematic. Soils of inslopes are generally nutrient poor, lack organic matter, and experience extreme microclimates of heat and nearly continuous drought. This report examined the concept that application of amendments to the soil or over the soil might have the capacity to increase fertility, increase soil moisture, or moderate the harsh microclimate of the inslope. In this study three different soil amendments/treatments were used to modify inslope soils including application of erosion control materials (ECMs) and enhancing soils with organic material. The two ECMs were products capable of changing soil temperatures, inhibiting soil moisture loss and/or enhancing the moisture aspect of the soil surface microclimate. The addition of organic matter is known to increase both soil water holding capacity and fertility. Although these products and treatments performed as expected, the overall conclusion of this study was that establishment of native species within two meters of the roadside was not enhanced by these treatments. Invasion by competitive weeds and weather (e.g., severe droughty conditions) appear to control the establishment of native species in the soils very near to the shoulder of roadsides.
