The Centennial Way project and the issues of shade in downtown Phoenix

The DVC will be dealing with issues of the City of Phoenix‘s proposed “Washington Street Centennial Way Project and Shade Aspect Recommendations” at tomorrow’s meeting. Local architect Taz Loomans’ column blow is directly related to this initiative.  In it, she makes the case for NATURAL shade in the urban core.

[Source: Blooming Rock]

A great example of engineered shade used in conjunction with trees at the Civic Space Park. Shade structure designed by Architekton. Photo from Arch Daily.

As I’ve discussed in the previous weeks on the Wednesday Phoenix Tree and Shade Masterplan series, the first step outlined in the Masterplan to restore our urban forest is Raising Awareness.  The second is Preserve, Protect and Increase.  Today I’ll be talking about the third and final step towards the Masterplan’s 2030 goal of a 25% canopy coverage in Phoenix – Sustainable, Maintainable Infrastructure.

The goal of this step, according to the Masterplan, is to “Treat the urban forest as infrastructure to ensure that trees and engineered shade are an integral part of the city’s planning and development process”.  When I think of infrastructure, I think of roads, storm water drains, and power lines, but I’ve never thought of trees and engineered shade as infrastructure.  But the definition of infrastructure, according to Wikipedia is:

Infrastructure is the basic physical and organizational structure needed for the operation of a society or the services and facilities necessary for an economy to function.

As I discussed in a previous post, a healthy urban forest is essential to the well-being of our city.  It is, indeed, essential for our society and economy.  And therefore, it’s not a leap to consider our urban forest and engineered shade as part of our city’s infrastructure.

Today is the first day I’m mentioning engineered shade in this Wednesday series on the urban forest.  Engineered shade is basically a man-made shade structure.  When it is not possible to put shade trees in an area, engineered shade becomes a good option.  Engineered shade can be attractive, artistic, and of course, it helps shade the city which adds comfort to being outdoors and also mitigates the heat island effect.  It can also act as a substructure for solar panels.  Certainly engineered shade is a solution multiplier.

However, I think it is important to note that engineered shade does not solve as many problems as trees do.  In fact, it is a poor substitute to nature’s solution to shade, improving the air quality, and reducing storm water runoff.  So whenever possible, it is best to plant a shade tree instead of building engineered shade, which does consume energy and resources in its manufacturing, whereas trees immediately contribute to the environment without ever asking for much in return.  Don’t get me wrong, engineered shade on and around buildings is appropriate whereas trees are not, and in that case, it is beneficial and necessary.

This brings me to the point of why people would opt for engineered shade, a more expensive up-front cost, over planting shade trees in open areas.  The first and foremost reason is that they might be afraid that they can’t maintain those trees over time.  That perhaps trees do ask too much in return.  This is where the final recommendation of Sustainable, Maintainable Infrastructure comes in.

Here are the challenges cited in the Masterplan with the current system in terms of maintenance:

  1. Currently, regulations in the City Code and Zoning Ordinance pertaining to vegetation maintenance in city right-of-way are difficult to enforce, and do not have any tree protection/preservation requirements following Certification of Occupancy.
  2. The city has generic tree inventory and salvage standards that are unclear and difficult to implement.
  3. There is a lack of consistent maintenance standards, as well as new tree planting specifications. Several valuable mature trees are lost each year due to improper planting and maintenance.

Some solutions to the maintenance challenge are:

  1. Tree Permitting – this would insure the tree is planted correctly in the first place, insuring its survival
  2. Planting and Irrigation Standards
  3. Landscape standards based on concepts of Right Tree, Right Place

Another reason one might opt for engineered shade over planting a shade tree is that a shade tree will consume too much water, a precious resource in the desert.

Some solutions to the water challenge are:

  1. high-efficiency irrigation systems
  2. use of drought-tolerant plant material
  3. strategic placement of shade corridors
  4. continued education

Remember that there are 30 to 40 trees available to us that are appropriate to our climate that would not consume an inordinate amount of water.  So let’s not use water consumption by trees as an excuse to deplete our urban forest.

Understandably the City might be shy about adding trees to their load at the moment, considering their slashed budgets.  They may be tempted to suggested engineered shade over shade trees for fear that they can’t maintain them.  But the City must first and foremost lead by example.  If the City expects private property owners to take care of their trees and plant new ones, the City itself must do so first, especially on showcase projects like Centennial Way, a State-funded project involving improvements on Washington Street between Central and and the State Capitol.  Installing engineered shade in lieu of shade trees, as suggested by some in the City, would be a very short-sighted, knee-jerk reaction to solving a problem that needs level-headed creative thinking.  Shade trees on Washington will become a long-term legacy to the City of Phoenix in a way that engineered shade alone will not.

As I mentioned in last Wednesday’s post, we can establish something like a Tree Fund or  tap into other community-based resources to help plant and maintain new shade trees along Washington and we will be giving a tremendous gift to future generations of Phoenicians.  Engineered shade should be used in conjunction with shade trees, not instead of them, as there is a need and a place for both types of solutions on the project.  Let’s not be blinded by the urgency of balancing the current Parks and Recreation budget and make rash decisions that will effect generations to come.

Note:  Don’t forget, there is a Tree Planting event this coming Saturday morning (the 11th)!  Click here for more details.

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