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How to create resilient, functional and beautiful landscapes in an urban desert environment

First, let’s state the obvious: it’s hot out here. And it’s only getting hotter. From April through October, the Phoenix region gets little respite from the punishing heat of the sun. We’re averaging between 104 and 106 degrees every day in the summer. When you factor in urban heat island effect — which increasingly is becoming a public health crisis in the summer — and our average of about five days total of rainfall between April and September, the job of designing and maintaining our parks is that much more challenging — and important.

All conversations about landscape design in this environment come back to water. While the region has made enormous strides in conservation since the 1970s when 80 percent of Arizona residents had lush turf front and back yards (that figure is down to 9 percent), the city also has experienced the largest population increase in the nation between 2010 and 2020. These conditions compel us to consider the highest and best use for our precious resources.

In dense urban environments, city parks often are the only green space people have access to on a regular basis. They mitigate urban heat island effect and support our public health infrastructure. What’s more, they are one of the last remaining places where everyone — regardless of age, income, creed or color — can come together, interact, socialize and play. The function parks serve must be deeply considered against and alongside best practices for resource use.

So, what does it mean to be a good steward when designing parks in modern urban desert environments? While there is no magic formula for a perfect balance, there is a framework for initiating the right conversations in the planning and design process.

Prioritize Shade

In the urban desert, shade is the difference between a park that offers respite and one that is utterly uninhabitable in the summer. While water use and shade creation may seem at times to be in conflict, we see shade — whether vegetative or mechanical — as a vital part of the solution to efficiently use our water resources to create usable public space. 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 shrub-like 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.

Protect Your Legacy (Trees)

When it comes to working within an existing urban park, heritage parkland trees can offer immense shade creation and cooling value in an urban desert environment and must be acknowledged and integrated into the new design concept wherever possible. Any design choice should consider the location, longevity and maintenance requirements of existing trees, balancing their benefits with succession planning. This process typically includes not just planting new trees, but also diversifying species with consideration for their expected longevity.

The Scottsdale Civic Center Park redevelopment included two inherited large banyan trees in the center of the park. The goal of preserving and enhancing the shade impact of these trees became a key design feature. To that end, the design envisioned a 360-degree shade structure circling the trees, which expanded the shade to create a centrally located community gathering place. Half living, half mechanical, it is an island of shade that allowed the design team to program the space with performance infrastructure.

Keep It Cool

Given the imperative to ensure an urban desert park remains usable as much of the year as possible, we must look at all possible opportunities to create the proper microclimates for different activities at different points in the day — whether that’s play areas or a yoga lawn. While numerous factors contribute to cooling ground plane — from mulch types to pavement colors and permeability versus impermeability — we will touch on turf use, as it is often associated with creating large open programmable space in these urban park settings.

While live turf provides significant benefits in urban heat island mitigation, the maintenance aspect and water requirements have municipalities rethinking the extents of its use. Artificial turf is a low-water-use alternative, but it still necessitates some water usage for cleaning and cooling purposes. It also can become incredibly hot and contribute to the urban heat island problem (not to mention the environmental consideration of per- and polyfluoroalkyl substances [PFAS]). As a result, we must factor in the cost of adding shade to ensure artificial turf remains usable.

Once again, the solution is often a combination of surface materials. At Scottsdale Civic Center, we limited the turf areas to specific areas for programming — everything else is low-water-use landscape. The design achieved a total reduction of half the turf area that was previously onsite, equating to a savings of almost 6 million gallons of water per year. The design team strategically used artificial turf in areas where maintenance of live turf would be a challenge and where folding tables and chairs would be moved in and out on a regular basis.

Balance Year Three With Year 30

Working with nature teaches you to plan for the future. As landscape architects, we’re always planning for what a site will look like on day one and how it will fill in, change and grow over decades.

Here in the desert, that future planning is even more crucial as we’re acutely aware of the risks of a warming world on an already challenging landscape. Every decision we make must account for long-term impacts, water availability and maintenance constraints. We’re no longer thinking about design as one-and-done. We’re looking at more comprehensive, successive planting plans that consider the growth and development of a site over time and best equip our clients with the tools they’ll need to ensure the landscape thrives long term.

Ultimately, the most important thing we can do as designers and communities is to be resourceful, creative and holistic in our approach. By reframing the conversation about water, shade and resource use on a site in a more comprehensive way, we can create landscapes that are both functional and beautiful, that both respond to our environment and allow for intense programming. Looking at all the options in our toolkit, there is opportunity for all the systems and design features in an urban desert environment to work together — now and for years to come.

Brandon Sobiech, PLA, ASLA, is Principal and Co-Founder of Dig Studio.