August 2023 - Parks & Recreation - 40

DESERT
Beyond cooling surfaces and ambient
air temperatures, shade helps
to keep moisture in the ground,
decreasing irrigation needs while
increasing the efficiency of irrigation
systems. In landscaped areas,
tree shade canopy networks can be
combined with passive stormwater
management techniques to hold
more moisture and promote robust
canopies. When done well, shade
structures and living trees can work
together to create a cool and inviting
park environment.
Understand the
Competition for Space
One critical factor for all trees, but especially
native Sonoran Desert trees, is
room to grow. Urban desert park spaces
with program requirements heavy
on amenities often mean stiff competition
for space. Wide pedestrian walkways
and programs like food truck
events and festivals constrict available
planting area. Our desert trees are sensitive
to planting area, as their natural
growth habits tend to be more shrublike
with vase-shaped forms and low
canopies. These growth properties
often are in direct conflict with urban
requirements, such as canopy clear
heights, clearances from sidewalks,
room for event tents, etc.
While we
consider
available
space during tree selection, we must
continue to push for more space for
trees and their roots. One of the best
ways to promote native trees in the
urban desert environment is to give
them space to be successful rather
than force them into compromised
conditions that limit their beauty,
functionality and lifespan.
Get Creative With Water
Designing parks in desert environments
goes beyond simply considering
total water usage. Our work involves
investigating alternative water
sources and finding ways to integrate
them into the design strategy. This
may include collecting water from
buildings, reusing and reclaiming
non-potable water, and exploring
various water-efficient design options
to passively or mechanically direct
water on the site to collect, feed
and supplement the features that
contribute to shade and cooling.
Sometimes,
the
strategy is
as
simple as working with the topography.
In the desert, trees in particular
respond in a noticeable way,
both in size and health, to additional
water, even if periodically. At the
gently sloped Civic Space Park in
Downtown Phoenix, you can see
the verdant pops of life where the
(albeit limited) stormwater runs.
The shade trees at the bottom of
that slope quickly have grown taller
than the ones at the top of the
hill - the same species, planted at
the same time, but with the added
benefit of just a bit more water.
Other times, the solution is more
creative. In Scottsdale Civic Center,
on both the east and west plazas,
we utilized structural soil for better
water retention and perforated the
site drainage pipe that ran under the
area. Think of the perforated drainpipe
like a straw with holes punched
in it that has been slid through structural
soil, which is like a Rice Krispies®
bar,
where the trees are planted.
With each storm event, the trees'
root systems get an extra boost of
water. With this solution, we passively
routed stormwater to the trees
in a way that didn't add to the cost
or maintenance requirements and
created long-term benefits to the
park functionality.
This simple, powerful and largely
invisible solution allowed for more
shade trees to be integrated into
the design while keeping the hardscape
on the surface flat enough for
events. This is one of a variety of
different water collection and redistribution
techniques used on the
site. The more water we save, collect,
reuse, capture, share or reduce
from other uses, the more we can
budget for long-term tree and landscape
infrastructure that can cool
spaces, reduce urban heat island effects,
create safe and inclusive microclimates,
and offer comfortable
activity centers for social interaction
and public health.
After 15 years, the
goal of shading the
hardscape surface area
at Civic Space Park by
75 percent has been
met.
40 Parks & Recreation | A UGUS T 2 0 2 3
| PARK S ANDRECRE AT ION . OR G
Protect Your Legacy (Trees)
When it comes to working within
an existing urban park, heritage
parkland trees can offer immense
PHOTO COURTESY OF ROBB WILLIAMSON
August 2023 - Parks & Recreation

Table of Contents for the Digital Edition of August 2023 - Parks & Recreation
