Overran or burst?
If they had alot of rain, don't they open up those dams so they don't overrun or burst? Not saying it was on purpose, but it could be.
https://www.michigan.gov/dnr/0,4570,7-350-79136_79236_80249-80301–,00.html
Michigan Water Management
https://www.michigan.gov/egle/0,9429,7-135-3313_3684_3723—,00.html
https://damsafety.org/michigan