The rains are coming. Metro Detroit is not prepared
Water engineer Jeff Bednar clutches a soil map in his Macomb County Department of Public Works office, which shows most of the southern, most developed half of the county in shades of purple and red.
The colors symbolize soils that are mostly clay and poorly drained. It’s one reason the Clinton River and surrounding areas in Macomb County are so flood-prone.
But Bednar, the environmental resources manager for the county, is excitedly pointing to a differently colored area in the county's southwest corner.
“See this area down here,” Bednar exclaims. “That's blue!”
Those sandy blue soils drain well. They’re part of the remnants of an ancient shoreline beach ridge formed when the Great Lakes covered part of the county more than 10,000 years ago. And they are critical to a plan county officials are hatching to get ahead of flooding in one of the state's most densely populated watersheds: the Red Run, a tributary to the Clinton River.
The Red Run is perhaps one of the most abused waterways in the state. It spans 142 square miles and is home to more than 550,000 people. It’s nearly 50% impervious – rooftops, roads, and pavement cover nearly every square foot of the landscape, shunting rainfall off to the nearest creek or ditch, then to the Clinton River and Lake St. Clair.
During heavy rains, the Red Run also gets swamped with partially treated stormwater mixed with sewage from the George W. Kuhn Combined Sewer Overflow Control Facility in Madison Heights. In 2021, the facility released 3.1 billion gallons of the stuff into the Red Run.
Like most older urban communities in Metro Detroit, the Red Run has combined sewers – pipes carrying raw sewage and stormwater runoff. These aging systems are ill-equipped to handle the massive volumes of stormwater runoff that we’re now seeing – and will continue to see more of – due to climate change.
Warming temperatures have already caused an increase in the frequency and intensity of rainfall across the region – and it’s expected to get worse. The 100-year storm (a storm so large that it has only a one percent chance of occurring in any given year) has increased in frequency by about 14% since 1960 in the Detroit area. Statewide, annual precipitation has shown an upward trend since 1995.
The situation is urgent, advocates say. In 2021, $1.2 trillion in federal appropriations under the Infrastructure Investment and Jobs Act (IIJA) went to pay for things like stormwater pipes. But they’re not being designed using accurate rainfall data, according to the nonprofit research group First Street Foundation.
A Southeast Michigan Council of Governments analysis shows rainfall volume for a 10-year storm event in Metro Detroit is expected to increase by 67% by mid-century and 138% by the end of the century.
Today, the sewers in Warren, where the eastern part of the Red Run flows, have about half the capacity to handle the 10-year storm based on historical rainfall data, much less any increases.
Officials across the region are beginning to recognize the situation's urgency.
“Apparently, these storms have become our new normal," Macomb County Public Works officer Candice Miller said following an August storm that inundated the county’s combined sewer system and required emergency bypass measures to avoid basement flooding. It was the third time the system, installed in 2017, had been used.
The Great Lakes Water Authority, which manages drinking and wastewater for the Metro Detroit region, created a new internal team this year dedicated to climate resiliency. It’s also embarking on a multi-year effort funded by the U.S. Army Corps of Engineers to develop a long-term strategy for climate-driven heavy rainfall. In the meantime, it’s worked on shoring up electrical equipment at existing pump stations, expanding the pump station at Conner Creek on Detroit's east side, and cleaning debris from sewer pipes.
“This is a challenge for the region,” said GLWA’s chief executive officer, Suzanne Coffey. “This is going to take a while, and it's going to take the municipalities, it's going to take utilities, it's going to take the region to come together to plan for the future.
But even if local agencies step up their leadership, collaborate, adopt updated rainfall data and funnel billions in infrastructure projects into the region, it's unclear whether it will be enough to stem future flooding and loss of life and property.
“Our stormwater infrastructure isn’t sized to handle these extreme rain events, but we also can’t rebuild all of this infrastructure,” said Kelly Karll, the Southeast Michigan Council of Governments Environment & Infrastructure Group manager. “What we can do is work together to make those major storm events less damaging by building resilient infrastructure – a combination of both green and gray – to slow down the runoff and reduce flooding impacts.”
Finding more capacity in a stressed system
Bednar sees an opportunity in those sandy soils in the Red Run. He wants to find ways to increase the sewer system’s capacity by helping stormwater bypass the combined sewer system altogether – by directing it to filter into the ground in unpaved places.
“You’ve got to figure out ways to get to [the soil],” Bednar said. “How do you build in the infiltration trenches? How can you get that water to go down?”
For the past several years, Bednar has participated in a SEMCOG task force to study the impact of climate change on the region’s sewer infrastructure – and how to increase the system’s capacity for handling it.
There’s a lot of uncertainty – SEMCOG issued guidelines in 2022 calling for a 20% increase in sewer design capacity, while the State of Michigan recently issued draft guidance calling for a 10% increase. So far, local governments have not adopted any new standards to increase capacity.
“We’re not there yet,” Karll said, noting more study is needed.
But ready or not, the rains are coming, and Metro Detroit will be one of the most impacted high-population areas in the country, according to an analysis by First Street Foundation. It shows the region now faces what was once a 100-year storm every 34 years. In 30 years, that will increase to every 16 years.
Current 100-year flood maps prepared by the Federal Emergency Management Administration don’t accurately reflect the risk because they don’t consider floods driven by rainfall, according to Jeremy Porter, First Street Foundation’s head of climate implications. Instead, they focus on river and coastal flooding.
As a result, the maps, which determine if homebuyers with federally backed mortgages must purchase flood insurance, miss a lot of risk.
“In Detroit, we find 36,990 properties at risk of flooding during the 100-year flood event; however, only 4,162 properties in Detroit are actually in the FEMA 100-year flood zone,” Porter said. “Most of this is because there is significant flood risk from rainfall-driven flooding, which is not taken into account in the FEMA model.”
The cost to insure those properties against flood damage is substantial. FEMA updated its internal model to price flood insurance in 2021, incorporating additional “flood risk variables.”
As a result, 90-100% of existing single-family home flood insurance policies in the Grosse Pointes and Dearborn increased by $10 per month between May 2020 and May 2021. The overall flood insurance rate for Wayne County increased by about 8%, from $675 to $725 per year. It increased 8.7% in Oakland County, from $602 to $654. In Macomb, it increased 32%, from $764 to $1,007.
Still, the Great Lakes region remains better off than most areas. The Texas coast, inland Louisiana, and coastal northern Florida saw the highest growth in the value of flood insurance claim payouts over the past 20 years, according to Loretta L. Worters, vice president of media relations for the Insurance Information Institute.
But that doesn’t mean there’s no risk. According to First Street Foundation’s Risk Factor, 433,525 properties in Michigan have greater than a 26% chance of being severely affected by flooding over the next 30 years – 17% of all properties in Michigan.
“Many people don’t believe they are at risk for flooding,” Worters said. “The human and economic tolls associated with flooding can be massive. Families, businesses, and communities can take years to recover from a single event.”
An ‘order of magnitude’ more investment needed
Upgrading infrastructure to reduce flooding will require massive amounts of money.
“Many communities are at the precipice of disaster,” Sanjiv Sinha, Ph.D., CEO for consulting group Corvias Infrastructure Solutions, LLC. and coauthor of a report outlining how cities across the Great Lakes are unprepared for increased rainfall.
Sinha believes metro regions across the Great Lakes need to think “big” about flooding now, not in a few years. He points to the Milwaukee region, where the regional water utility leverages its strong credit rating and state revolving funds to fund green infrastructure projects that may cost over $1 billion between 2020 and 2035, He said the situation in Southeast Michigan – especially Detroit – will likely require a similar scale investment.
Karll said the region must invest $1 billion annually in upgrading its storm sewers just to bring its existing pipes up to good or fair condition – not even accounting for features to address flooding. According to Coffey, GLWA spends about $350 million yearly on capital projects. That means Metro Detroit is investing “much less and likely an order of magnitude less than is needed,” Karll said.
“We have a long way to go,” she said. “This is a job for the next generation of civil engineers.”