NORFOLK, Va. – Under an overpass near Norfolk’s downtown, Kyle Spencer nods to a small black box mounted on a jury-rigged tripod that is unraveling the mysteries of the city’s aging storm-water infrastructure.

The box is one of 27 low-cost monitors that wirelessly transmit readings every few minutes about water flowing through pipes beneath two of the city’s neighborhoods. For Spencer, Norfolk’s deputy resilience officer, the results have been shocking.

Sea-level rise driven by climate change and the area’s sinking land is pushing water through pipes from the Elizabeth River as much as a mile inland, sometimes flooding yards and street bypasses, even on sunny days. At low tide, the 72-inch pipe beneath his feet is half-filled with water even before it rains. During high tide, pipes in the system may be as much as 90 percent full. That dramatically diminishes the system’s capacity to drain water during storms.

“We didn’t know how much water stays in these pipes and it was very much, ‘Aha, oh my God that’s worse than we thought.’, ” said Spencer.

Storm-water systems are the soft underbelly of American infrastructure. They’re expensive to build and maintain, often costing hundreds of millions or even billions of dollars. They’re increasingly vulnerable as climate change drives “rain bombs” that dump inches of water on cities in hours, overwhelming pipes and pumps. Norfolk’s system is so old that it has terra-cotta pipes in places.

The American Society of Civil Engineers’ 2021 report card ranks storm-water infrastructure nationally as a D on an A-to-F scale. An accompanying survey of storm-water officials by the Water Environment Federation, an industry group, reported an $8.5 billion annual shortfall in funding.

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As storm-water infrastructure is failing, climate change is driving more frequent and intense rainfall. A 2019 study by University of Wisconsin researchers found in the eastern half of the United States, 100-year storms – ones with a 1 percent chance of happening in any year – were occurring almost twice as often as in 1950. In 2020, there were a record 20 storm and hurricane events each causing more than $1 billion in damages, according to the National Oceanic and Atmospheric Administration.

Storm-water runoff is also a pollutant, one that scientists increasingly realize is complex. It’s not just fertilizer, plastics, and automotive oil, but a variety of toxins. When storm water floods roads and lawns and then retreats into rivers, lakes, and ponds, it carries those pollutants with them.

What’s different about the system in Norfolk is the sensors cost a fraction of previous models, so more can be deployed. That could change how some cities manage their sewer systems and design future projects based on hard data, not soft guesses. In the past, Norfolk would create a model of the storm-water system’s capacity by using closed-circuit cameras to look for blockages, sending workers to pull manhole covers and inspect the pipes, and chronicling anecdotal flooding complaints. It’s expensive and results in what Spencer calls a “best guess” about the system.

Sensors such as the ones deployed in Norfolk and other cities, including Charlotte; South Bend, Ind.; Ann Arbor, Mich.; Kansas City and Detroit, represent a way to squeeze a little more life from aging storm-water and sewer systems, say city officials. “There’s a huge sewer value proposition that this kind of data is going to bring to the city like ours,” Spencer says.

In Norfolk, the sensors and software were installed by StormSensor, a Seattle start-up. They are funded through RISE, a Norfolk nonprofit backing climate solutions innovations. Erin Rothman, StormSensor’s founder, says the company typically installs 20 gauges in a storm sewer watershed for $100,000 the first year and then $50,000 annually to maintain monitoring. That’s a fraction of the more than $30,000 a similar sensor cost a decade ago, according to an EPA report .

Cities are leveraging the sensors in a variety of ways. Norfolk has used them to measure the intrusion of tidal waters and the true capacity of pipes in the two threatened neighborhoods. Charlotte and Mecklenburg County, N.C., began deploying 118 low-cost storm sensors in 2018 in a test funded by the Department of Homeland Security to track rising waters during storms along roadways, bridges, dams, and other vulnerable places.

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Josh McSwain, an information technology project manager with Charlotte, says the low-cost sensors increase coverage of the areas at risk to 96 percent from 46 percent.

“During the storm, emergency management can see where the water level actually is,” McSwain says, rather than trying to interpret whether a road has been overtopped or a home has been flooded.

In Detroit, another city with storm and sewer overflows, Branko Kerkez, an associate engineering professor at the University of Michigan, led a study that used information from sensors to control valves and gates during a storm. By opening and closing them at the right times, the system could handle as much as 100 million gallons more without overflows. Building storage to hold that much water would have cost the city $500 million.

“That’s wild, wild numbers,” Kerkez says, “but it shows how much you can get out of existing systems if they’re operating more efficiently.”

Smart water technology hasn’t gotten the same attention that other smart technologies have attracted, says Kerkez.

“People go, what about the risks? Couldn’t it (the system) be hacked? The answer is, like any other technology, it has pros and cons,” he says. “But there’s a risk to doing things how we’re doing them now. There’s already billions of dollars of flooding.”