The NACTO Urban Street Stormwater Guide should first be commended for the sheer amount of information it compresses into a succinct guide that touches upon nearly every consideration in the planning and design of green streets. I can only imagine the amount of coordination that took place to assemble the different national green street case studies, as well as the nearly impossible task of reigning in different perspectives on streetscape design from various planning and design disciplines.
While past NACTO guidebooks have successfully focused solely on street, bikeway, or transit design, the Urban Street Stormwater Guide delivers one of the most comprehensive guides on how to combine complete street design and green infrastructure stormwater management. Having a volume like this on one’s shelf is extremely helpful to anyone who is engaged in even general streetscape planning and design, as it points out the importance of having green infrastructure integrated into the right-of-way.
Design guidebooks are always a unique snapshot in time. They highlight our current understanding of design application and what, at the moment, can be implemented. This is an important consideration for the Urban Street Stormwater Guide — it reflects our design comprehension of green infrastructure at the current moment. This too will, and must, evolve over time.
Early sections of the guide provide a powerful argument for why “Streets are Ecosystems.” Stormwater runoff is no longer treated as a waste but as a valuable resource that should be managed in the right-of-way using a green infrastructure approach. The design community, I believe, comprehends and embraces this basic premise, but there is still a lack of understanding, which is reflected in this guidebook and reverberates in today’s built green street projects.
While stormwater runoff is now not considered a waste, it is still mistakenly labeled as a source of the problem of urban stormwater management. Runoff is not the source, but a symptom and result of the larger problem that urbanization has dramatically removed natural landscape systems and replaced them with impervious area.
We now focus on treating the symptom of “too much stormwater runoff” by designing small-footprint, deep-profile “landscapes” that force water back into the ground to prevent urban flooding, reduce the burden on grey stormwater infrastructure systems, or comply with state and federal regulations.
While reducing flooding and infrastructure capacity issues are important, these approaches create a water-centric approach very much reflected in this guidebook, which dilutes the focus and urgency to address the real problem of landscape loss. The only way to address this issue is to dramatically spread the footprint of vegetation and perviousness in our built environments. Only when we advocate and create a greater balance of green space and perviousness in our cities can we then accurately label our streets as “ecosystems.”
The Urban Street Stormwater Guide provides a series of “stormwater streets” as hypothetical scenarios of different urban conditions, such as a green transitway, ultra-urban green street, boulevard, neighborhood main street, and a host of other urban contexts. These are valuable glimpses of the possibilities of introducing vegetated swales, stormwater planters, pervious paving, rain gardens, and other green infrastructure and complete street elements into urban conditions.
However, the models shown have a definite tilt towards very urban conditions with the huge rights-of-way commonly found in larger American cities. The hypothetical boulevards, transit streets, and even the neighborhood main streets green street examples in the guidebook look nothing like those that I have worked on in smaller cities. Where are the examples outside of the big city? How about strip mall or big-box arterial streets, small-town main streets with tight sidewalks and packed with on-street parking, and the ultra-wide suburban residential streets that have covered mass landscapes in this country?
I raise this question, because these latter streets are just as impervious and incomplete. They produce massive amounts of stormwater runoff, just like our big city downtown streets, but are completely forgotten in the Urban Street Stormwater Guide vernacular.
From a stormwater management perspective, I define an urban street as any street that has a curb, gutter, and sidewalk that produces excessive stormwater runoff. It appears that the Urban Street Stormwater Guide defines an urban street similarly, but focuses largely in ultra-urban downtown conditions. Perhaps there is an opportunity to follow up this guide with a “less-urban” street stormwater companion guide.
I think that this omission is largely due, again, to the “snapshot in time” effect and focuses more on examples where green streets are currently being implemented: in big cities that are trying to comply with stormwater consent decrees and/or dealing with infrastructure capacity issues. The truth is that we need green streets in all urban contexts, and those should be better represented in this guide.
As I mentioned before, the Urban Street Stormwater Guide packs in an incredible amount of information in a finite number of pages. It feels almost too dense, where some graphics and photos are reduced to a miniscule scale, and text flows as if one is simply reading a series of bullet points (albeit good bullet points). In fact, some of the very important cross-sections of types of stormwater facilities are so cryptic, with minimal or no text call-outs or dimensions, that they remind me of the pictures illustrated when one is trying to follow an IKEA shelve assembly instructions manual. When dealing with urban stormwater, cross-sections illustrating very specific horizontal and vertical layout are critical.
Lastly, I worry that many of the cross-sections, and even the built project photo examples, suggest too much hardscape in the form of vertical walls to contain landscape and soil. Excessively-engineered green street facilities go against the very principles of green infrastructure to keep things simple, shallow, cost-effective, and beautiful.
One of the most successful elements in the Urban Street Stormwater Guide is the numerous design, planning, and policy case study examples shown throughout the United States. Each case study describes the project’s goals, project overview, design details, keys to success, lessons learned, and qualitative and quantitative outcomes. There are excellent pictures of projects shown in action.
Some case projects are clearly more successful than others, but it is extremely valuable for everyone to understand what has been built and how the project is performing, regardless of its real or perceived level of success.
Another very successful piece of the guide is Section 5: Partnerships and Performance, which highlights successful green street programs and policies from around the United States, details the need for inter-agency and private-public partnerships, and outlines operation and maintenance roles and responsibilities. The discussion of operations and maintenance should take a more formative role earlier in the guide, as maintenance often defines what can be built, to what extent, and how it will perform in the long-term.
In conclusion, the Urban Street Stormwater Guide is an valuable resource to those planning and designing green street projects. It makes a very strong argument that green streets and complete streets can live symbiotically and details different examples on how to combine these design strategies.
This guide is a wonderful snapshot in time of what has been built, but the guide also shows that we still have much to learn and that green infrastructure strategies are still evolving. I again really commend the amount of information provided in the guide and the level of coordination that was needed to complete it. I look forward to the next edition of the Urban Street Stormwater Guide.
This guest post is by Kevin Robert Perry, ASLA, principal of Urban Rain Design.