The Edenville and Sanford dams in central Michigan were breached on Tuesday, May 19, 2020, following days of heavy rainfall, forcing about 10 000 residents to evacuate. The National Weather Service (NWS) has issued flash flood emergencies along the entire Tittabawassee River in Midland County on May 20, as threats of dangerous flooding continue.
Governor Gretchen Whitmer warned that downtown Midland, which was declared to be under an emergency, could be "under approximately 2.7 m (9 feet) of water" by Wednesday morning, May 20, as waters were rapidly rising after days of heavy rain.
By then, the Tittabawassee River is expected to peak at around 12 m (38 feet) by 12:00 UTC (08:00 LT)-- about 1.2 m (4 feet) higher than its record of 10 m (34 feet) set in 1986. The flood stage is at 7 m (24 feet).
NWS urged residents near the river to seek higher grounds as flash flood emergencies have been issued, as well as a flash flood watch, in what was described as "catastrophic dam failures". People were also advised to be prepared for immediate evacuations and avoid driving into flooded roadways.
About 10 000 people in the towns of Edenville, Sanford, and Midland were forced to evacuate, with downstream effects expected from Midland to Saginaw. It was the second time in 24 hours that people were prompted to flee.
The areas were drenched by rains around 102 to 178 mm (4 to 7 inches) from Sunday to Monday, May 17 to 18.
Whitmer said that while residents should take the threat seriously, they also should continue to observe safety precautions amid the COVID-19 pandemic, including maintaining social distancing and wearing masks.
"To go through this in the midst of a global pandemic is almost unthinkable, but we are here, and to the best of our ability we are going to navigate this together," she remarked.
Whitmer said that the failure of the dams is a historic event, playing out in the midst of another historic event, which is the pandemic.
Dr. Dave Petley, Pro-Vice-Chancellor of Research and Innovation at the University of Sheffield, wrote on The Landslide Blog that the cause of the failure is not clear as of present, citing a media report that the license for the dam had been withdrawn because it had insufficient capacity to handle the Probable Maximum Flood.
The Federal Energy Regulatory Commission ruling stated, "Of particular concern is the project’s inability to pass the Probable Maximum Flood (PMF) due to inadequate spillway capacity."
"Currently, spillway capacity at the Edenville Project can only pass about 50 percent of the PMF," it added. Designs for remediation of the hazard were being prepared, with construction expected around 2021 to 2023.