- The Role of Stormwater Design in Climate Resiliency
Extreme weather has cities getting “caught in the rain”.
From nuisance floods to severe storms, most communities aren’t at all prepared for extreme weather. The climate is changing. It’s absurd to politicize it, because the climate always has been and always will be changing and humans can’t control it. Not even Al Gore-type humans. But with the vast majority of 7.5 billion humans living in cities that depend on centralized water infrastructure, the effects of extreme weather can be devastating.
Climate resilience was a fancy buzz-phrase ten years ago. It actually means something today, as 2019 marked the fifth consecutive year that the U.S. endured 10 or more extreme weather events causing greater than $1 Billion in damage each. And while the storm events that cause the most damage are newsworthy, we rarely hear about the smaller events that are occuring much more commonly. Smaller scale flooding is happening all the time in cities across the country, causing property damage and threatening the security of urban water systems.
Stormwater management is the policy, planning, engineering, implementation, and maintenance of urban water systems. It is a critical component of any city’s water infrastructure. But since these systems are conceived within the limits of expected behavior, it should come as no surprise that they are continually overwhelmed by larger storm events. From New York to Minnesota, a common theme endures: in the face of extreme weather, our nation’s stormwater infrastructure is failing.
Communities across the U.S. are responding on very different ends of the spectrum. In some cases, towns are trying to buy out flood-prone neighborhoods and turn them into wetlands. On the other end of the spectrum, officials keep their heads in the sand and do nothing. The majority of U.S. cities, however, recognize serious vulnerabilities within current infrastructure. Unfortunately, upgrading mammoth assemblages of underground plumbing and conveyance isn’t cheap, and a one-size-fits-all approach to stormwater management isn’t practical.
Remember how I mentioned that existing stormwater infrastructure in this country was conceived within the limits of what used to be expected? Federal rainfall estimates are continually being adjusted upward. As an example, a 100-year storm event in Minnesota, over the course of 24 hours, used to produce 6 inches of rain. Today that same storm is expected to produce 8 inches. In Austin, a 24 hour, 100-year rainfall event has increased by an average of 3 inches, and in Houston it’s increased by 5 inches!
Cities that commit to an evolving stormwater design philosophy will be most prepared for this type of sudden weather event. A shift from grey infrastructure – the pipes and conveyance system that moves runoff someplace else – to a more natural approach that manages stormwater right where it falls, will be critical to the future resilience of urban water systems.
- Urban Flooding doesn’t have to be the New Normal
Severe weather in the U.S. takes a hefty economic and societal toll each year. At the time of this writing in 2019, there have been 10 weather events that each resulted in losses greater than $1 Billion. Of these, 3 included severe floods and 5 included “severe storm events”.
When I think of flooding, extreme images of Houston, New Orleans, and Tohoku readily come to mind. But urban flooding in U.S. cities happens far more commonly than the mainstream news storm event, and they cumulatively take a bigger economic toll.
More recent scenes like these in New York or Spokane don’t get national attention because they’re local and not quite “natural disasters”. But flooding events like these happen more often than you’d think and they go mostly unnoticed…save for the local residents that end up dealing with the damage.
A changing climate is making these events more frequent, but it doesn’t help that our cities are caked in impervious concrete and asphalt. Up to 40 percent of U.S. cities are covered by impervious surfaces in the form of roads, parking lots, sidewalks, and other pavements. Rain and melted snow that would naturally soak back into the earth instead turns into high volume stormwater runoff. That polluted runoff is channeled to wherever the grade was designed to take it, usually far away from where it originally fell.
Under normal conditions, stormwater runoff goes to a treatment plant to be cleaned before it’s discharged into our water systems. More often than not, larger rain events completely overwhelm grey stormwater systems from the sheer volume of runoff. The result is polluted discharge spewing into our rivers or up through manholes and into the street.
Better Stormwater Management
Stormwater management is the policy, planning, engineering, implementation, and maintenance of our urban water systems. It’s a critical component of water infrastructure. The classic approach to stormwater management entails channeling water away from impervious surfaces and the structures built atop them. We’ve constructed our cities on the assumption that the water that would have been absorbed back into the land can be transported away instead.
The problem is that the policies and the engineering that support an urban stormwater management plan are conceived within the expectations of past norms. With unpredictable weather and rapid urbanization adding thousands of miles of impervious surfaces each year, designing stormwater systems with data from even five years ago is dangerous.
Unpaving the Way?
Many urban planners point to impervious surfaces as the problem. Cities like Baltimore have even begun removing thousands of acres of pavement.
But pavement reduction as the sole cure for urban flooding isn’t scalable. Urban development continues to increase and pavements (roads, sidewalks, etc.) play a critical role in the transportation of people and goods, amongst other things.
Mimicking rural hydrology with green space is smart, but it is also limited by scale. Usable space in dense urban areas comes at a premium because there simply isn’t much of it. It’s why some cities questionably allow developers to build on flood plains and many other cities struggle with urban sprawl. There simply isn’t an endless supply of land area for stormwater parks, rain gardens, and vegetated swales. And where there is available space, it’s undoubtedly expensive. No question green infrastructure has a role to play in stormwater management, along with improving grey infrastructure. But to solve this issue at any meaningful scale, we need a whole new toolkit altogether.
The Future of Hardscape Infrastructure
If urban flooding can be tied to cities having too much impervious surface area and not enough green space, we can determine the huge role that permeable pavement will have in the future of urban infrastructure. Permeable pavement theoretically provides the function of normal pavement, while also playing the role of “green space” by allowing water to soak through it and into the ground below. But current market technologies are limited by their material capabilities.
Nevertheless, innovation is relentless. And it is usually driven by need. With a $103 Billion stated need for municipal stormwater upgrades, the opportunity for new technologies and approaches in the industry has never been greater.
Today there are cement and material technology startups developing the pavements of the future for on-site stormwater management. By creating permeable hardscape material that is extremely strong, with the ability to filter out contaminants in stormwater, cities will have the ability to greatly mitigate urban flooding and “future proof” themselves in ways that are actually scalable.
- Shifting the Paradigm in Water Infrastructure
“The way you can identify a broken paradigm,” says George Gilder, “is that the problem gets worse the more money you spend on it.”
George Gilder is a futurist and a technology prophet of sorts. I’m sure George didn’t have U.S. water infrastructure in mind when he made the comment above, but it certainly applies. Crumbling infrastructure and unpredictable weather events are stressing urban water systems to the brink of failure, with regulators calling for more than $700 billion in capital improvements for our nation’s water infrastructure over the next few years.
Hefty investment is needed in water infrastructure to ensure a clean, more secure water future. But simply throwing capital at larger versions of outdated solutions is bad policy. You don’t put a band-aid on a puncture wound.
The average citizen doesn’t think much about it, but pollution from stormwater runoff is arguably the most pervasive environmental issue that cities face today. Ironically, about 860 municipalities around the U.S., discharge raw sewage into clean waterways by design. These old combined sewer systems are forced to handle sewage, wastewater, and stormwater within the same arrangement. So when rainfall can’t soak into the ground, it runs off of pavements and into stormwater collection drains by design.
Relying solely on this type of water infrastructure may have been feasible decades ago and before cities were sprawling and caked with pavement. Today, our cities have urbanized to the point where non-draining, hard surfaces make up the overwhelming majority of land cover. Three-quarters of Philadelphia, for example, is impervious. So when it rains, huge volumes of runoff finds its way to stormwater drains, picking up every pollutant on the pavement along the way. The more pavement, the more polluted runoff for these combined sewer systems to handle.
Pavement is ubiquitous because it’s useful. And until Elon Musk’s Hyperloop arrives or we’re traveling like the Jetsons with Point-to-Point Aerial Transport, pavements in the form of streets, sidewalks, and parking lots will continue to be crucial for urban mobility and transporting people and goods. So perhaps we should rethink how we design stormwater infrastructure to account for this. It probably starts with an understanding that the old approach of “moving water out” hasn’t just led to mass pollution of waterways, it’s also increased the likelihood of major flooding….and worse still, large coastal cities are literally sinking as aquifers get robbed of natural recharge.
Time for a Paradigm Shift
From my vantage, there is a general feeling of cities scrambling to become more “resilient” as the climate alarm shrieks. But like any meaningful issue, the water problem can’t be solved just with politician’s logic – “we must do something. This is something. Therefore we must do this!” Because by itself, this is proving to be ineffective.
Fortunately, it’s possible to innovate our way to a cleaner, more secure water future. And while “innovation” usually connotes the latest new technologies, it’s the large governing institutions that hold the key to innovation. The key then, is for these institutions to simply embrace it.
Cities, regulators, and large institutions can be painfully path dependent when it comes to embracing new approaches. There are good reasons for this, which we won’t get into here. Fortunately, we’re starting to see progress from some cities as they make more meaningful investments in green infrastructure. We’re seeing vitality in the private sector with an array of startups advancing various software and hardware technologies for monitoring runoff and sewage overflows. There are new permeable materials being developed that can manage stormwater right on-site, returning it naturally into the ground below. And there’s even creative early stage financing arms, helping connect these innovative startups with the capital they need to provide their solutions to the marketplace.
We need more of all of this because what’s at stake is tremendous. Private companies need to continue to relentlessly innovate, capital needs to flow to the development of these ideas, and institutional decision makers need to take a shot on new technologies and approaches when given the chance. It’s time to shift the paradigm because a purported $1 Trillion dollar need for improving water infrastructure is a $1 Trillion opportunity to sustain our most valuable resource.