Improving tree root growth and reducing urban runoff by combining the use of porous pavements and structural soils

2005 | Dr. Nina Bassuk

Soils under pavement are highly compacted to meet load-bearing requirements and engineering standards.  This often prevents tree roots from growing or, if they do, they often heave the pavement.  Twelve years of research on the development of structural soils and hundreds of installation all over the country have demonstrated unequivocally that trees grow well in structural soils if they are designed carefully and proper tree selections are made.  We now want to combine the use of structural soils technology with the use of porous pavements to increase water recharge into the soil to aid in root growth while preventing storm water runoff.  Trees can play a uniquely valuable role in mitigating urban storm water runoff in our increasingly developed urban cores if a system can be designed to store water on site under the pavement and use it to benefit tree growth.

Three avenues of experimental observation detailed aspects of plant available water holding capacity in compacted stone-soil media designed for urban tree establishment in paved situations. The various compacted media provided an estimate of the plant’s available moisture content of 7%–11% by volume, comparable to loamy sand. Changes in aggregate and of soil influenced initial field capacity moisture content, but high matric potential moisture content was consistent, presumably as a reflection of the aggregate content of the designed system. A large portion of plant available moisture was weakly held in large voids, consistent with related infiltration and permeability data, and could be an influence in water storage and irrigation planning to use layers of designed soils in a layered pavement section for urban vegetation.

Year: 2005

Funding Duration: 3-5 years

Grant Program: Hyland Johns

Grant Title: Improving Tree Root Growth and Reducing Urban Runoff by Combining the Use of Porous Pavements with Structural Soils

Researcher: Nina Bassuk

Key words: structural soils; porous pavement; root growth; water runoff storage

Peer Reviewed Publications from Grant:

  • Grabosky J and Bassuk N. 2016 “Seventeen years’ growth of street trees in structural soil compared with a tree lawn in New York City.” Urban Forestry & Urban Greening Vol. 16,103-109.
  • Bassuk, NL, Denig, B, Graposky, JG, Trowbridge, PJ, Orr, D, Haffner, R. 2015 CU-Structural Soil: A comprehensive guide pp55 DOI: 10.13140/RG.2.1.2506.4721
  • Grabosky, J, Haffner, E and Bassuk,N.L. 2009. Plant Available Moisture in Stone-soil Media for use Under Pavement While Allowing Urban Tree Root Growth. Arboriculture & Urban Forestry 35(5): 271-278 View the Publication >
  • Stormwater Management: Using Trees and Structural Soils to Improve Water Quality. 2008 with Virginia Tech and UC Davis. View the Publication >
  • Grabosky, J and Bassuk, N.L 2008 Sixth- and Tenth-Year Growth Measurements for Three Tree Species in a Load-Bearing Stone–Soil Blend Under Pavement and a Tree Lawn in Brooklyn, New York, U.S. J. of Arboriculture and Urban Forestry34 (4):265-266
  • Haffner, T. Bassuk, N. Grabosky, J and Trowbridge, T. 2007. Using Porous Asphalt and CU-Structural Soil. View the Publication >

General Audience/Trade Publications:


For more information on this project, contact the researcher via TREE Fund at