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Posted on September 7th, 2018 in Forests and Street Trees, Urban Forestry | No Comments »

A recent study at the University of British Columbia noted that a single tree along an urban street can help alleviate winds, shade pedestrians, and decrease wind pressure on nearby buildings. For both homes and businesses, the presence of trees can help decrease costs associated with maintaining indoor temperatures.

flickr.com, photo credit: Kris Arnold

Photo credit: Kris Arnold, flickr.com

Researchers used remote sensing technology to create intricately detailed computer models of a neighborhood that included each tree, garden, and structure. The models were able to elucidate how various scenarios (no trees, bare trees, full-leaf trees) influence airflow, thermal patterns, and overall radiant heating and cooling throughout the streets of the neighborhood. Resultant data indicated trees at various stages can decrease wind speeds by as much as a factor of two. For example, a strong 30km/h wind could be reduced to a comfortable 15km/h breeze.  The results also showed trees reduced the strain caused by wind pressure on building spaced closely together and farther apart. Close examination of the data indicated wind pressure causes up to a third of the costs associated with energy consumption and increased costs up to 10% in winter and 15% in summer. Using data gleaned from over a decade of measurements (from a monitored wind tower), they discovered even leafless trees are beneficial in winter months to regulate air flow and wind pressure on buildings.

This modeling effort represents the first of its kind to simulate actual neighborhood conditions using an existing neighborhood recreated in great detail as a model. Further work of this kind can be used to predict storm effects on structures and pedestrian movement. These data can assist engineers and city planners in the creation and layout of buildings, streets, and greenery while limiting energy losses and help evaluate proposed effects of weather forecasts throughout the neighborhood.

flickr.com, photo credit Rob Young

Photo credit: Rob Young, flickr.com.

References:
M.G. Giometto, A. Christen, P.E. Egli, M.F. Schid, R.T. Tooke, N.C. Coops, M.B. Parlage. 2017. Effects of trees on mean wind, turbulence and momentum exchange within and above a real urban environment. Advances in Water Resources, 106: 154 DOI: 10.1016/j.advwatres.2017.06.018

University of British Columbia. Trees can make or break city weather. Science Daily, 26 July 2017.

Resources:
Tree Selection for the “Un-natural” Environment, The Education Store – Purdue Extension’s resource center
Planting Your Tree Part 1: Choosing Your Tree (Youtube video),  Purdue Extension-FNR
Tree Installation: Process and Practices , The Education Store
Tree Planting Part 2: Planting a Tree (Youtube video), Purdue Extension-FNR
Top 5 List for Tree Selection and Planting, Got Nature?, Purdue Extension-FNR
Indiana’s Urban Woodlots, The Education Store

Shaneka Lawson, USDA Forest Service/HTIRC Research Plant Physiologist/Adjunct Assistant Professor
Purdue University Department of Forestry and Natural Resources



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