Traditional infrastructure often makes flooding worse, study finds

Ten years ago, a record-breaking rainfall hit southeast Michigan on Aug. 11, resulting in flooding across the region. The catastrophe led to highway closures, power outages, stranded drivers and property damage to more than 100,000 homes, costing $1.8 billion. 

Today, University of Michigan researchers have utilized data from the disaster to conduct a study of the U.S. stormwater infrastructure in order to better prepare for future severe weather events. The study, published on Aug. 27, found that decades-old stormwater infrastructure around the United States could be worsening the impacts of flooding during severe weather events. 

Researchers also found that historical infrastructure design is not efficient in mitigating flooding. Most of this infrastructure fails to account for flood connectivity — the interplay between flooding mechanisms and drainage pathways in an urban environment. The interactions between different stormwater systems and the movement of water in river channels and pipes are often unanticipated, worsening flood conditions.

Valeriy Ivanov, a professor of civil and environmental engineering at the University, is an author on the study and contributor to a policy brief on stormwater management. In an interview with The Michigan Daily, he said researchers recognized the need for a holistic approach to stormwater infrastructure design after examining the 2014 flood in southeast Michigan.

“When we looked at the 2014 flood, we noticed that none of the traditionally designed systems for motor infrastructure could have handled the event,” Ivanov said. “What we discovered through that research was that, essentially, there is interaction between different parts of the watershed as the flood is taking place. I think that there is a need to go away from this sort of local thinking or local design solutions. We need to have interactions in a system.”

Ivanov described floods as one of the most economically harmful kinds of natural disasters for a community.

“I think economically or impact- wise, in terms of dollar amount, I think it’s number one of all the natural hazards,” Ivanov said. “Everywhere, actually around the world — not only the United States — floods are the most impactful economic events.”

In an interview with The Daily, Joan Nassauer, professor in the School for Environment and Sustainability, said traditional infrastructure systems need to be updated because many of them were designed for smaller urban environments than they currently serve. Nassauer also said new infrastructure designs should use “green and blue infrastructure,” a term describing the network of natural and semi-natural systems that ultimately enhance the environmental quality of ecosystems.

“That infrastructure was originally designed often for a smaller urban footprint — when cities were smaller — and certainly before climate change,” Nassauer said. “The existing infrastructure needs maintenance and replacement, which is a huge project. I would emphasize that GBI should really be part of the system-wide approach, and that there are particular opportunities to do that in cities that have a higher proportion of open land, either planned open space or opportunities with vacant land.” 

Rackham student Yuanqiu Feng, a doctoral student in the School for Environment and Sustainability who studies under Nassauer, explained her perspective on how to mitigate flooding with the current infrastructure in place. Feng said an effective solution would use green infrastructure, which includes landscaping vacant areas with trees to act as windbreaks, absorb atmospheric carbon and increase canopy.

“What I’ve been looking at in my research is green infrastructure — basically can we make use of all that vacant land to store some of that storm water without having to revamp the entire stormwater infrastructure system?” Feng said.

Feng said she believes refurbishing existing infrastructure is an important element of addressing the impacts of flooding. 

“Can we make it such that these vacant lots are able to hold some of that stormwater and let it go into the system more slowly rather than overwhelming it in a very short period of time, which is how these problems with sewer flow happen and basement backups and so on?” Feng said.

Ivanov said in light of the study’s findings, infrastructure design must use a more holistic approach.

“We’re still using simplified solutions in design, and these solutions are not necessarily capable of taking a holistic perspective,” Ivanov said. “It is crucial to move to more sophisticated design models.”

Daily Staff Reporters Kate Levy and Alexis Spector can be reached at kjlevy@umich.edu and alexissp@umich.edu.

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