Quantifying the Potential for Non-Point Source Pollution in Model Urban Landscapes

Abstract

The contribution of non-point source pollution to degrading surface water quality is considerable throughout Virginia and beyond. While research on agricultural best management practices in nutrient management and nutrient and soil stabilization has made progress in reducing agricultural contributions to nutrient and sediment loading of watersheds, little is known about how land covers of different vegetation representative of urban areas (e.g., bare soil versus turfgrass lawns versus urban forest) influence the potential for non-point source pollution. Ambient rainfall volumes were manipulated to provide 50%, 100%, and 150% of natural precipitation to plots with landscape covers of bare soil, shredded wood mulch, turfgrass, and simulated urban forest (complete pin oak canopy with shredded hardwood leaf mulch). Precipitation amounts, runoff volumes, and eroded sediment masses for ten rain events between July and December 2004 were measured. Runoff was analyzed for nitrate and orthophosphate concentrations for three rain events. Turfgrass was found to be the most effective of the land covers tested at reducing components of non-point source pollution from stormwater. Turfgrass plots produced, on average, the least runoff and sediment, and lower nitrate concentrations in runoff water as compared to the other land covers tested. Results from urban forest plots apparently reflected the disturbance of tree planting, even six months later. This study contributes to a sparse body of knowledge about the influences of urban landscapes on water quality, and will inform land use policy and urban Best Management Practices.