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All About NACTO’s Urban Street Stormwater Guide

The National Association of City Transportation Officials (NACTO) is a coalition of America’s largest cities committed to building safe, sustainable transportation systems and active cities through better street design and transportation policy. NACTO has established itself as a leader in changing the way our streets operate for people regardless of transportation choice and has assembled a series of design guides for practitioners, policy makers, academics and advocates (Urban Street Design Guide, Urban Bikeway Design Guide and Transit Street Design Guide) that focus on improving our cities’ transportation network for the 21st Century.

Inspiring our streets and public rights-of-way to do more than just move cars, NACTO has just released its newest design guide, the Urban Street Stormwater Guide, which focuses on how cities can integrate sustainable stormwater systems to manage stormwater runoff and protect natural resources while considering infrastructure resiliency and climate change. According to NACTO’s website, the new guide:

“provides cities with national best practices for sustainable stormwater management in the public right-of-way, including core principles about the purpose of streets, strategies for building inter-departmental partnerships around sustainable infrastructure, technical design details for siting and building bioretention facilities, and a visual language for communicating the benefits of such projects. The guide sheds light on effective policy and programmatic approaches to starting and scaling up green infrastructure, provides insight on innovative street design strategies, and proposes a framework for measuring performance of streets comprehensively.”

NACTO’s previous design guides filled a much-needed gap for transforming urban streets, with the Urban Street Design Guide, endorsed by the U.S. Department of Transportation and Federal Highway Administration (FHWA), providing cities a sort of “permission to innovate” by building on the design flexibilities in AASHTO’s Policy on Geometric Design of Highways and Streets (Green Book). What’s exciting about the Urban Street Stormwater Guide is that as a “first-of-its-kind collaboration between city transportation, public works, and water departments” it focuses on another key statement in the Green Book, which states that streets should “serve as a catalyst to environmental improvement” and that landscaping should “mitigate the many nuisances associated with urban traffic.”

I talked to Corinne Kisner, NACTO’s Director of Policy and Special Projects, who oversaw the development of the new Urban Street Stormwater Guide to learn more:

NACTO member cities span the spectrum of geographic location and climate. Was it challenging to convince the NACTO board and/or member cities that NACTO was the appropriate organization to fill a gap in developing design guidance for sustainable stormwater management in the public right-of-way?

That’s an interesting question. While each of NACTO’s member cities has its own unique challenges related to stormwater conditions (drought, flash flooding, snow, etc), all cite climate change and the need to build more resilient transportation infrastructure as driving their search for new or improved strategies. Cities are on the front-line planning for those impacts and we heard from member cities and board members who were interested in thinking about stormwater and transportation within the same street.

Stormwater concerns vary across the country based on permitting requirements, type of sewer systems and other climate impacts, but cities are finding the demand for change is also coming from residents, who are increasingly asking for improved livability and aesthetics from their streets. So the motivations range widely. One of the things NACTO was well positioned to do was facilitate a new vocabulary that was necessary for us all to share to be able to consistently integrate all of these solutions to create high performing streets.

Can you share a few examples of typical issues confronting NACTO member cities that are addressed by the design guide?

A very common issue is the limited amount of space that is available within a street to manage several competing needs. Urban streets must function for a variety of uses (traffic, parking, street furniture, trees, utilities, landscaping, etc.) and users (people driving, taking transit, walking, and biking) – often within a constrained space. Whether the street is 60-feet or 20-feet from curb to curb there are constant challenges for how to best utilize this space. As managing stormwater becomes a more common need for cities to comply with permit requirements (e.g. EPA’s NPDES permit program and Combined Sewer Overflow Control Policy), agencies are increasingly looking at strategies to incorporate multiple things within the physical fabric of the street and better utilize available space. This guide provides a framework for doing that.

Another typical issue with this type of infrastructure is maintenance. With this guide, we went beyond design to discuss the partnerships, performance measures, policies, and programs that will make projects successful over time, and not just when they are first built. Seattle and Philadelphia are two member cities who participated in the development of the guide that stand out for having extensive maintenance systems in place for asset management.

The guide was developed by a team of transportation and stormwater engineers/planners. What did you find most surprising (unexpected) working with these two groups during the development of the guide?

It was a fascinating process working with these two groups. The development of this guide came on the heels of NACTO completing the Transit Street Design Guide, which was a collaboration between traffic engineers and transit agencies to find common ground and prioritize transit on the street, so NACTO staff was somewhat familiar working with specialists in two different fields. However, while transportation and stormwater engineers have a lot of shared goals they speak very different languages and their work can often be siloed in different departments.

What became apparent with this process was the need to develop the tools and language to show how each party could get more from their streets and find shared ground. In determining the need for this guide, it was clear there was an abundance of resources for stormwater engineers, but very few designed for a collaborative audience of city practitioners that must work together to solve these complex challenges. Thus, we wrote the guide to help spark interdepartmental conversations within city departments and we hope it will result in an evolution from single pilot-scale projects to citywide programs.

Are there topics or content people might expect to find in the design guide that were not included?

This guide is not meant to be a technical guide as there are a lot of technical resources for the design and maintenance of green stormwater infrastructure. What you will find is technical information about how different green stormwater elements fit within the public right-of-way and within a multimodal corridor. For example, how a bioswale can be used to not only manage stormwater runoff but also be located within a curb extension to shorten the distance for a pedestrian crossing the street or buffer a protected bike lane from vehicular traffic.

What was the most interesting thing you learned during your involvement in developing the design guide?

I learned a lot about how flexible green stormwater infrastructure is and how much thought and experience it takes to design effective systems. However, what was so great about the steering committee and the process we went through to develop the guide was learning how creative and solution-oriented the cities are at incorporating green stormwater infrastructure to better streets.

One critical value I was pleased to learn is how cities are finding green stormwater infrastructure can perform better over time. There are very few infrastructure assets that appreciate in value over time, but as vegetation establishes, these facilities can treat and infiltrate more stormwater runoff, making the systems a good investment in both the short and long term.


As a civil engineer practicing in the field of urban transportation and stormwater management it is exciting to see this new guide becoming available. It will be an invaluable resource to agencies, planners and engineers across the country who are looking to integrate green stormwater infrastructure into their transportation corridors.

The full version of the web based guide will go live on June 29th. NACTO is also hosting two webinars to introduce the new guide, one on June 29th with Island Press and River Network and a second on July 10th with the National Complete Street Coalition.


Nathan Polanski is a civil engineer with MIG | SvR.

Ashley BischoffCC BY-NC 2.0

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