Urban Landscape Management Practices as Tools for Stormwater Mitigation by Trees and Soils

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Virginia Tech

As urban land expands across the globe and impervious surfaces continue to be used for constructing urban infrastructure, stormwater treatment costs and environmental damage from untreated stormwater will rise. Well designed urban landscapes can employ trees and soils to reduce stormwater runoff flowing to streams and treatment facilities. Typical urban soil, however, is compacted and restricts tree growth via high soil strength and inadequate gas exchange. A site preparation method that deeply incorporates compost and includes trees for long term carbon input and pore development was evaluated in the urban setting of Arlington, Virginia. Three species were used in that study of 25 streetside plantings. The site preparation affected soil at 15 30 cm by lowering soil bulk density by 13.3%, and increasing macro-aggregate-associated carbon by 151% compared to control plots, and resulted in 77% greater tree growth during the first year after transplant. In a second experiment, rainfall simulations were used to evaluate common landscape mulch materials for their ability to prevent compaction from traffic as well their affect on surface runoff before and after traffic. When plots were subjected to heavy rainfall, (>97 mm/h) mulches were found to reduce sediment loss 82% and 73% before and after traffic, respectively. Runoff rates from wood chips were only 0.19 ml/s faster after traffic while rates from bare soil and marble gravel with geotextile increased 2.28 and 2.56 ml/s, respectively. Management of soils, trees and landscapes for stormwater benefit could reduce cost of wastewater treatment for municipalities and can prevent environmental degradation.

mulch, urban soil, stormwater management, green infrastructure, urban trees, runoff, urban forest