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Infrastructure Week 2019: The future of green infrastructure

May 14, 2019

By Bernadette Callahan

Stormwater management systems shouldn’t be buried under other infrastructure priorities—and green infrastructure can help build resiliency

Stantec’s Green Infrastructure Sector Leader Bernadette Callahan takes a look at the current state of green infrastructure (GI) in American cities and what we can expect in the future. This Q&A blog is part of a 5-part series for Infrastructure Week 2019.

What is your perspective on the poor marks from the American Society of Civil Engineers on city infrastructure, and the current state of green infrastructure?

Funding is a major issue for stormwater management and green infrastructure in particular. It hasn’t really been a priority for tax dollars. One issue is that most of our systems are buried, and you don’t see them, so it’s not perceived by the public to be at the forefront of our infrastructure needs.

When storm systems were originally designed across the county, standard practice was to collect rainfall in pipes and convey it to the nearest waterway. Now, many of these systems are aging and undersized since they were designed for a different ultimate population and precipitation intensity. When an area is developed, more water runs off from the impervious surfaces (e.g., parking lots, buildings, etc.) and drains into the storm system. As a result of some of the more significant storms we’ve been seeing, storm systems have been backing up and flooding—they just can’t handle the intensity and frequency of the storms.

With a growing concern of water quality in our waterways, regulations have been put in place to reduce the pollutants associated with stormwater runoff. This is an opportunity to take a step back and see what makes sense in terms of repair and replacement. Green infrastructure—introducing vegetation to naturally reduce water runoff into our sewers—can be a great solution to compliment and extend the life of our gray infrastructure, which is what we have now.

What are our burning priorities on infrastructure investment, from your perspective?

As we look at trying to build a more resilient system, we need to find multi-benefit solutions that reduce the financial burden of upgrading and replacing storm systems. We also need to look at what future storm conditions might be, considering sea level rise and changes to precipitation intensity, and use a conservative approach in resizing our systems to make them more resilient to bounce back from those storm events.

Even with limited funds, green infrastructure can provide secondary benefits that help to justify the funding—looking at a triple bottom line.

Green infrastructure projects are typically built on a much smaller scale than gray infrastructure, allowing you to adapt the design strategy as you go. In Philadelphia, for example, we’ve been working on the Green City, Clean Waters Initiative for the last seven years. At the onset, we were managing for 1 inch of runoff, but we’ve since found that the variable cost associated with designing for 2 inches isn’t much more expensive and it builds a lot more capacity in the system.

We need to think about what types of projects are appropriate for a given site and how they can be adapted over time, ensuring we’re getting multiple benefits whenever possible. That includes both retrofitting older developments and implementing zoning requirements into newer developments.

Green infrastructure can be incentivized with expedited review times or zoning bonuses. In Philadelphia, for example, certain zoning districts allow for a greater building density, such as an additional building level or height, if the building includes a green roof.

A rain garden installed at Nebinger Elementary School in Philadelphia reduces impervious surface runoff.

Is there a model out there for what we should be doing in your sector (good financing models, specific projects, etc.)?

Good places to start the conversation about green infrastructure are local entities like the parks or public works departments, school districts, etc., to get a sense of what their goals are in terms of upgrading their facilities. This can include increasing vegetation and determining how stormwater management can be integrated and dovetail with those priorities, accomplishing several goals at once.

We recently worked on the Jose Manual Collazo Playground with the non-profit Trust for Public Land, working toward a reality where everyone has access to a park within a 10-minute walk of their home. In this case, the Trust pursued the grant funding to create a new park space to include handball courts, a spray ground, and a community gathering space. A portion of their funding came from the Philadelphia Water Department to manage stormwater runoff from the public right-of-way on the site, demonstrating that above all, we need to be creative in how we approach green infrastructure. It’s not just stormwater management funds that we should be looking at, but rather using triple bottom line philosophy to leverage resources across the board.

Many municipalities have been looking at ways to manage stormwater where it falls—in public spaces and in the public right of way—to meet their stormwater goals while making best use of public space. In this way, you can build additional capacity into the existing storm system while making improvements to the public realm. The goal is to install a new system directly upstream from existing stormwater infrastructure to reduce the load in a rainfall event.

Sketch of a rain garden, which is a potential green infrastructure solutions as part of a municipal vulnerability study in Somerville, Massachusetts.

What can we be doing to build GI now?

Pilot programs are a great way to start to build green infrastructure. These types of programs help us to figure out what works for a municipality and how to tailor an ecologically sensible solution to fit that area.

In Somerville, Massachusetts, for example, we’re working on a municipal vulnerability study with grant funding to examine what green infrastructure can do for the City in terms of water quality and water quantity. Our GIS-based analysis showed that while the drainage areas to the existing catch basins were relatively large, green infrastructure footprint areas were limited due to driveway locations, buildings, utilities, large urban trees, and other constraints.

In the Gentilly neighborhood of New Orleans, Louisiana, we’re working on a large-scale green/gray infrastructure project to reduce flooding and to improve water quality. This area has a very flat topography with catch basins everywhere, so capturing a large drainage area can be a challenge. Developing pilot studies like these will help municipalities understand their constraints and how systems can be adapted to help solve their unique environments.

How do you see GI in the future? Say 2030?

I’m already seeing more cities develop these green infrastructure solutions to address more stringent water quality and water quantity regulations. They want a multi-benefit solution, not just a tunnel. Even with limited funds, green infrastructure can provide other benefits that help justify the funding—looking at the triple bottom line. 

I believe that green infrastructure will become the new normal for all new development. Through public education and civic engagement, we can help our neighbors understand the importance of stormwater management. For example, a rain garden in a school yard can be an educational tool where students sample the soil or the water, inventory the plants, and learn what they do. It’s about educating for the future and communicating why it matters.

Renderings of a corner stormwater bumpout (left) and tree trench (right) being proposed as part of the Green City, Clean Waters program in Philadelphia.

How do you see Smart Cities and technologies fitting into green infrastructure?

Smart Cities and technologies can be used to optimize our investments in green infrastructure. For example, a smart outlet could be used to dewater a stormwater pond if the weather forecast calls for rain, providing additional storage volume to treat the oncoming storm. As another example, real-time performance monitoring could be used to promote the benefits of green infrastructure and to track the effectiveness of a system during different conditions.

Other blogs in this series:

Infrastructure Week 2019: Brownfield development is the future of the US urban landscape

Infrastructure Week 2019: Parks as infrastructure—providing resilience and quality of life

  • Bernadette Callahan

    Bernadette is a senior water resources engineer, experienced in land development and green stormwater infrastructure design for almost two decades. She works to address the challenges and opportunities in sustainable urban water management.

    Contact Bernadette
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