UM-CEE Professor Glen Daigger was the principal investigator on the six-person independent panel examining Metro Detroit’s historic flooding in Summer 2021. The goal of the recently-issued report is to provide infrastructure solutions to address short-, medium-, and long-term flooding problems in local communities. A second U-M faculty member, Johanna Mathieu, Associate Professor of Electrical Engineering and Computer Science, also served on the panel.
The final report–released last week by the Great Lakes Water Authority (GLWA) with support from engineering consulting firm AECOM regarding the June 25-26, 2021, and the July 16, 2021, rainfall events–determined that future devastating flooding could be reduced if the Metro region follows a proposed series of actions to help local communities address infrastructure issues.
“It was a pleasure to work with the AECOM team on this important assignment,” CEE’s Daigger said. “The outcomes are particularly important in that the report addresses not only how the existing system can be used more effectively, but the larger changes that are needed in the Detroit metropolitan region to address future flooding issues that will be more intense than in the past.”
If enacted, the recommendations of the GLWA report can work toward improving the quality of life of Detroit-area residents and keep communities safer in the event of heavy rainfall events by reducing the likelihood of catastrophic flooding.
The GLWA report noted, “The intensity of the rainfall (last summer) far exceeded the designed capacity of the wastewater system and, as a result, some level of both surface flooding and basement backups was unavoidable.”
Although some pumps failed to work, the intensity of the rain in such a short period of time was a key factor that resulted in the flooding. The overall report suggests that “conveyance capacity in the collection system, not pumping, was the primary cause of flood risk and additional pumping capacity would not appreciably reduce the risk of surface flooding and basement backups. Rather, a strategic assessment of conveyance improvements, inlet controls and in-system storage is warranted.”
“The investigation concluded that even if every bit of piping and equipment in the regional system had worked in an ideal manner, flooding would still have occurred in the GLWA system, or any other collection system designed to today’s standard,” GLWA interim CEO Suzanne Coffey said. The GLWA report’s recommendations generally “focused on measures to improve availability and reliability of existing infrastructure, medium-term measures to retrofit and improve infrastructure performance, and long-term measures to investigate and develop policies and direction to maximize level of service. Many measures can be undertaken by GLWA internally.” Some highlights of the recommendations include:
- starting generators during anticipated heavy rains so they are ready to act if needed
- making improvements to the vacuum priming system at Conner Creek
- keeping the Connor Creek storage gates and relief gates at the CSO Basins in good working order
- reviewing existing studies with consideration of flooding and water quality objectives
- conducting additional studies to understand flooding and water quality level of service and optimizing system operations using “real-time” data
- considering different operating procedures for extreme storms
- buying out homeowners in flood-prone areas
GLWA officials say they have also installed three new transformers at the Freud Pump Station and converted its power supply to three independent DTE Energy feeds, installing devices to give advance notice of power outages and establishing better communication with east and west side communities. Ultimately, GLWA recommends fostering regional coordination to address future potential flooding situations.
GLWA is also working to find funding for a Flood Risk Mitigation Study for southeast Michigan that would identify more complex long-term steps, such as deep tunnel systems, that could relieve pressure on the region’s system.