Use of street trees is an important tool in an integrated stormwater management plan that can be applied to both existing and newly developing areas. It’s helpful for government officials to be aware of the many benefits trees contribute to the environment and the bottom line of the community's budget. However, fallen tree leaves contain phosphorus. If they are not picked up, the phosphorus can accumulate in local waterways. Municipalities would need to consider a leaf collection program. While there are programs and standards to reference, it is important to refer to experienced landscape architects to determine the appropriate planting strategy to implement.
As communities develop guidelines for stormwater best management practices, use of street trees should be incorporated. Key elements of ordinances include spacing guidelines for trees along new or reconstructed roads and preventing removal of existing trees along a road corridor. Boulevard sections, if used, should be sunken. Curbs and gutters should be eliminated so grass and trees can be planted.
Because streets constitute such a large portion of the impervious cover in a typical urban area, planting trees along streets to provide a canopy becomes an important part of managing urban runoff. Trees can be planted in the terrace area between the street and sidewalk or in certain boulevard sections. Trees reduce the amount of runoff by intercepting rain in their canopies and allowing it to evaporate. The United States Forest Service reported in a 1991 study that tree canopies in Chicago reduced urban storm water runoff 4 to 8 percent. (2)
addition to capturing rain and reducing the amount of runoff, street trees
also provide shade and reduce surface and runoff temperatures.
Tree Planting Schedule -- Back to
Actual spacing is dependent on the type of trees selected and their mature size. A local forester, arborist, or landscape architect can provide an appropriate tree-planting schedule that considers local climate and soil type.
Trees should also be planted in boulevard sections when possible. Besides the aesthetic value, it has been shown that properties on tree-lined streets have a higher value than those without. (3)
Boxes -- Back to Top
of Existing Trees -- Back
However, smaller trees are often removed. This becomes a problem when road builders restore the roadway and replace these smaller though established trees with very young ones that require significant maintenance.
Besides environmental costs, this process of removing trees results in increased project costs due to excess clearing, purchase and maintenance of new trees. It may be necessary to allow narrower road widths and tighter turning radii, where applicable, to preserve existing trees near the roadway. However, narrower roadways will also save on project costs and reduce impervious cover and runoff (also see Streets and Roads).
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The municipality may also develop an adopt-a-tree program where municipalities purchase trees and taxpayers or civic groups are responsible for installation and maintenance. Local conservation or natural societies may also be solicited to make donations toward planting and maintenance of street trees.
Street Trees Regulations -- Back to Top
The WDNR has no regulations for Street Trees, and
no state minimums.
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This page was created on March 26, 2003.