…Along your Walkable Streetscape and Perimeter Block, assure that there is attractive vegetation.
__Problem-statement: Few element provide more benefits to neighborhoods and cities than street trees. But there are challenges with their placement and maintenance.__
The “SmartCode”, a form-based code developed by DPZ CoDesign, shows a number of different patterns for street trees, varying according to urban intensity or “Transect zone.”
Discussion: Sometimes the assumption about street trees is that they will march down every street, identical species at a regular spacing. But they need not have such a relentless pattern. For example, some trees might be of a distinctive species, producing a particularly beautiful flower or leaf color. The pattern of trees can also vary, sometimes alternating, sometimes grouping into natural patterns, or forming “bosques” of parallel rows.
There are other considerations for street trees as well, and one of the most important is the ability of trees to survive with low maintenance in what can be a stressful urban environment and climate. Many neighborhoods have lost huge numbers of trees due to disease (for example, Dutch elm disease). It is therefore important to pick hardy, climate-appropriate species, and mix them so that a die-off of any one species will not denude the entire street.
Street trees must also be placed to avoid interfering with overhead power lines, and with buried utilities. So-called “root guards” — barriers that force the roots to travel downward and not sideways — can protect utilities as well as concrete sidewalks. Trees that are in vulnerable locations, prone to damage.
__Therefore: Plan streets with street trees at their edges and medians, varying in species and in placement as appropriate for building frontages. Place trees to avoid conflicts with overhead power lines, and protect buried utilities with root guards if needed. Protect them with tree guards when young.__
Use street trees to create Framing of vistas. Coordinate placement of street trees with a Form-Based Code…
notes
¹ A review of benefits and challenges can be found at Mullaney, J., Lucke, T., & Trueman, S. J. (2015). A review of benefits and challenges in growing street trees in paved urban environments. Landscape and Urban Planning, 134, 157-166. A shorter overview of some of the same issues is provided by Dan Burden, at Burden, D. (2006). 22 benefits of urban street trees. Orlando FL: Glatting Jackson and Walkable Communities, Inc. Available on the Web at http://www.walkable.org/download/22_benefits.pdf
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