Studying the soil-strength effects of vegetation for slope stabilization and erosion control along streambanks and roadside slopes

Abstract

Vegetative covers are a common solution used for erosion control and slope stabilization for a variety of applications. Studies were conducted to look at two applications of vegetation for erosion control, stream restoration and roadside slopes, by studying root traits, plant establishment, and run-off analysis. The first part of this experiment created simulated streambank microcosms in the Auburn Plant Research Center that contained live stakes of two common riparian species, black willow (Salix nigra) and silky dogwood (Cornus Amomum). The vegetation growth was monitored and various root trait were analyzed after a 4- and 8-month growing period. The results suggest that the black willow is able to develop a much larger biomass belowground that creates a stronger hydrologic effect on the surrounding soil. The dogwood develops more slowly so it had less overall biomass but the roots developed had significantly higher tensile strength than the black willow at a 90% confidence level. The second part of this experiment studied the use of vegetative covers along a roadside slope. Erosion that occurs during and after construction projects is a leading source of sediment loading in surface waters and vegetation is an easy and natural solution to decrease soil movement. This study looked at four species of plants, Parson’s juniper (Juniperus chinensis “Parsoni”), vetiver grass (Vetiveria zizaniodies), maidenhair fern (Adiantum pedatum), and hairy vetch (Vicia villosa Roth) in comparison to a control, fescue grass (Lolium arundinaceum), to monitor their establishment and growth in test plots along the NCAT test track in Opelika, AL. The maidenhair fern and hairy vetch were not able to be successfully established for the duration of this study but both the juniper shrubs and vetiver grass were able to grow successfully and decrease sediment movement in the test plots under standard roadside conditions in comparison to the fescue grass. The quantitative methods of run-off analysis proved to have large margins of error that created uncertainty in the results but the general trends showed that the juniper shrubs had the lowest sediment yield and the lowest volume of run-off coming off the plot. The vetiver grass did not perform as well but it also showed a general trend of less overall sediment yield and volume movement as compared to the fescue grass control.