When it rains in cities, where does all the water go?

 For Kian Bagheri, an ARCS Foundation Scholar supported by the San Diego ARCS Chapter, that question has become the focus of his doctoral research at San Diego State University and UC San Diego.

“In the broadest terms, my research investigates stormwater management in urban areas,” Bagheri explained. “I look at how cities manage rainfall, what challenges come from that management—whether it’s flooding or pollution—and how these systems are likely to change in the future as the climate shifts, sea levels rise, and infrastructure continues to age.”

Bagheri’s work zeroes in on combined sewer systems, which are older systems that carry both stormwater and wastewater together to treatment plants. While common on the East Coast and in the Great Lakes region, some cities on the West Coast also rely on them.

“The challenge is that when large rain events happen, the treatment plants can’t handle the volume. Cities are then required to discharge some of this untreated waste directly into waterways. That’s happening all over the world,” Bagheri said.

Using numerical modeling, Bagheri studies how these systems respond now and predicts how they’ll perform in the future. He has conducted projects for cities including San Francisco, Bremerton, Washington, and even Tijuana, Mexico, where wastewater overflows affect Southern California’s coastal communities.

“I hope my research helps government agencies better understand the impacts of climate change on their systems,” he said. “And I want residents to know how city design affects water quality on their beaches and even flooding in their neighborhoods. The more we understand, the better we can prepare.”

Bagheri’s path to this work began with a love for the environment.

“I started in environmental engineering because I wanted to understand how human activities impact natural systems,” he said.

During his undergraduate years, he earned his scientific diving certification, assisted in oceanography and ecology research, and saw firsthand how human activity was harming coastal environments.