Stormwater runoff from highways can contain pollutants such as suspended solids, nitrogen and phosphorus, organic material, and heavy metals. Growing awareness leading to regulatory requirements reflects the need to protect the environment from highway runoff effects. The management practice discussed in this study is the use of vegetated roadsides. The primary objective of this research is to document the potential treatment values from vegetated roadsides typical of common rural highway cross sections in two Texas cities: Austin and College Station. Three sites in each city were examined in this study over a 14-month monitoring period. No significant difference between the edges of pavement pollutant concentrations were observed at any of the research sites in the two study areas. This allowed for direct comparisons of the vegetated roadsides and their associated site characteristics such as annual daily traffic (ADT), dry period, and rainfall intensity. The scatter plots of College Station data show that concentrations of total suspended solids (TSS), total Pb, and chemical oxygen demand (COD) in runoff are dependent on the antecedent dry period and decrease with longer dry periods. The results show that pollutant concentrations are not highly dependent on ADT. However, the results show that the number of vehicles during the storm (VDS) was evaluated and accepted as a satisfactory independent variable for estimating the loads of total Pb and TSS. The results of correlation analysis show that the concentrations of total Pb and chemical oxygen demand are significantly correlated with TSS levels. The findings indicate that nitrate concentrations in runoff is most dependent on the average daily traffic using the highway during the preceding dry period as well as the duration of that dry period. Sites 2 and 3 in College Station are steeper but outperformed Site 1 which has much flatter slopes. This could be accounted for by the poor vegetative cover (brown patches) at Site 1. In the Austin sites, the permeable friction course appeared to have a significant impact on the quality of runoff leaving the road surface. On the whole, the results of this study indicate that vegetated roadsides could be used as a management practice for controlling and treating stormwater runoff from Texas highways.

Stormwater runoff from highways can contain pollutants such as suspended solids, nitrogen and phosphorus, organic material, and heavy metals. Growing awareness leading to regulatory requirements reflects the need to protect the environment from highway runoff effects. The management practice discussed in this study is the use of vegetated roadsides. The primary objective of this research is to document the potential treatment values from vegetated roadsides typical of common rural highway cross sections in two Texas cities: Austin and College Station. Three sites in each city were examined in this study over a 14-month monitoring period. No significant difference between the edges of pavement pollutant concentrations were observed at any of the research sites in the two study areas. This allowed for direct comparisons of the vegetated roadsides and their associated site characteristics such as annual daily traffic (ADT), dry period, and rainfall intensity. The scatter plots of College Station data show that concentrations of total suspended solids (TSS), total Pb, and chemical oxygen demand (COD) in runoff are dependent on the antecedent dry period and decrease with longer dry periods. The results show that pollutant concentrations are not highly dependent on ADT. However, the results show that the number of vehicles during the storm (VDS) was evaluated and accepted as a satisfactory independent variable for estimating the loads of total Pb and TSS. The results of correlation analysis show that the concentrations of total Pb and chemical oxygen demand are significantly correlated with TSS levels. The findings indicate that nitrate concentrations in runoff is most dependent on the average daily traffic using the highway during the preceding dry period as well as the duration of that dry period. Sites 2 and 3 in College Station are steeper but outperformed Site 1 which has much flatter slopes. This could be accounted for by the poor vegetative cover (brown patches) at Site 1. In the Austin sites, the permeable friction course appeared to have a significant impact on the quality of runoff leaving the road surface. On the whole, the results of this study indicate that vegetated roadsides could be used as a management practice for controlling and treating stormwater runoff from Texas highways.

Exotic plant species can be a serious threat to native ecosystems and the human economy. They have often been found to grow in greater abundance along roadsides, and seem to use them as corridors of invasion into the surrounding habitats. This study sought to determine whether there were any relationships between the distribution of exotic plant species and adjacency to roads in southern Illinois. To test this question, I conducted two research projects. For the first project, I ran transects from active and abandoned roadsides into adjacent forest interiors to collect data on the presence and abundance of exotic species. Along most roads, exotic species richness declined with increasing distance from the road. In most cases, abandoned roads were more likely than active roads to have a high abundance of Lonicera japonica and Rosa multiflora. For the second project, I collected geographical data for exotic species from field studies, herbaria records, and literature records, and compared them based on distance from the nearest road, family composition, and life form composition by both number of species and number of records. On average, herbaria records were farther from the road than field studies. Composition of families and variety of life forms were not significantly different when comparing by number of species, but were significantly different when comparing by number of records.

Non-point source pollution caused by erosion from road construction poses hazardous environmental effects. Percolation and infiltration of nutrients into groundwater can also be detrimental to the surrounding environment. In addition, annual roadside maintenance budget exceeded $14 million in 2011 for Mississippi. Objectives of this research were to evaluate rapidly established short-statured species in an effort to prevent erosion, combat non-point source pollution, reduce mowing cost, and provide quick cover following propagation. Factors evaluated were rate of establishment, plant cover, and mowing requirement. MDOT’s standard seed mix was evaluated along with Pennington’s SlopeMaster product and different combinations of selected plant species. Visual and image analysis showed oilseed radish plants established the quickest and provided the most cover. All sod treatments provided instant cover while Pennington’s Slopemaster product, as well as mixes that contained bermudagrass or bahiagrass, provided sufficient cover, but not in a timely manner.

I investigated percent coverage, plant height, species richness, and woody stem density in plant communities in ten study plots during spring and fall (2010-2012) within 3 different treatments (continual mowings, one fall mowing, and one fall mowing with native wildflower seeds) on highway 25 right-of-way in Oktibbeha and Winston counties, Mississippi. I recorded 277 plant species including native and non-native forbs, legumes, grasses, rushes/sedges, and woody plants. Non-native agronomic grasses exhibited greatest coverage greater than 90 percent occurring in all treatments. Percent coverage of plants less than 0.46m height category exceeded 100 while, greater than 0.46m plant height categories averaged 55 percent. Woody stem density ranged from 7,772 year 1 to 10,025 stems/hectare year 2. I detected no significant differences in plant height or woody stems among treatments. One mowing per year retained agronomic plant cover for erosion control and annual cost savings up to 75 percent for roadside maintenance.