A very slow moving low pressure system advanced east from the central Plains. Unusually deep moisture was pushed northward into the Great Lakes region, ahead of this low. Multiple rounds of heavy rain fell in parts of northern lower Michigan on the 17th and 18th. This heavy rain targeted east central and northeast lower Michigan in particular. Rainfall amounts of 2 to 4 inches were common by the morning of the 18th in places like Tawas City, Houghton Lake, Omer, and West Branch. Further heavy rain continued, and by the morning of the 19th rainfall amounts were 8.10 in Au Gres, 7.43 in East Tawas, 7.20 in Sterling, and 7.60 near National City. Generalized flooding was widespread and considerable in that part of lower Michigan. In some spots, flooding impacts lasted for days. Runoff from this very heavy rain resulted in the catastrophic failure of Edenville Dam on the Tittabawassee River.

Flood in GLADWIN, MICHIGAN
From 18-MAY-20 12:00:00 to 22-MAY-20 12:00:00 (EST-5)
Location: GLADWIN FORTIER ARPT
Flood cause: Heavy Rain
Property damage: 11.00M
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread areal flooding developed on the 18th, and persisted for several days. Most creeks and rivers in Gladwin County rose out of their banks. Several hundred miles of roads across the county were closed at various times. The Tobacco River at Beaverton rose to a record crest of 14.32 feet on the morning of the 19th. Somewhat more than 100 residents were evacuated from their homes, including people living below the Chappel Dam on the Cedar River. The M-30 bridge across the Tobacco River where it enters Wixom Lake was destroyed.

Flood in IOSCO, MICHIGAN
From 18-MAY-20 12:00:00 to 20-MAY-20 12:00:00 (EST-5)
Location: ALABASTER
Flood cause: Heavy Rain
Property damage: 1.20M
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread areal flooding developed in central and southern Iosco County on the 18th. Many creeks and rivers rose out of their banks, including the Au Gres River system and Silver Creek and its tributaries. Many roads across the county were closed, including Meadow Road in Tawas City. Railroad tracks were also washed out in Tawas City. Townline Road in Tawas Township was washed out by Dead Creek. Flooding along the Lake Huron coastline was worsened by lakeshore flooding thanks to onshore winds.

Flood in OGEMAW, MICHIGAN
From 18-MAY-20 12:00:00 to 20-MAY-20 12:00:00 (EST-5)
Location: PRESCOTT
Flood cause: Heavy Rain
Property damage: 450.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread areal flooding developed in central and southern Ogemaw County on the 18th. Many creeks and rivers rose out of their banks, including the Rifle River system. Many roads across the county were closed. The Prescott area was especially hard hit, with some property damage due to flooding.

Flood in ROSCOMMON, MICHIGAN
From 18-MAY-20 12:00:00 to 20-MAY-20 12:00:00 (EST-5)
Location: ST HELEN
Flood cause: Heavy Rain
Property damage: 240.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Areal flooding developed in central and southeast Roscommon County on the 18th. Some creeks and rivers rose out of their banks. Many roads across the county were impacted by high water, and that included a few closures. There was some property damage due to flooding, especially in parts of Houghton Lake.

Flood in ARENAC, MICHIGAN
From 18-MAY-20 12:00:00 to 22-MAY-20 12:00:00 (EST-5)
Location: ALGER
Flood cause: Heavy Rain
Property damage: 4.40M
Crop damage: 0.00K
Reported by: Emergency Manager

Widespread areal flooding developed on the 18th, and persisted for several days. Most creeks and rivers in Arenac County rose out of their banks. Many roads across the county were closed at various times, including M-13 south of Standish. The Rifle River near Sterling reached a new record flood stage of 15.65 feet on the afternoon of the 19th. Some structures along the River River and Parmalee Creek were partially submerged. The Forest Lake area was evacuated due to rising water. Hundreds of homes were flooded in the Standish area. Flooding along the Lake Huron coastline was worsened by lakeshore flooding thanks to onshore winds.

Flash Flood in GLADWIN, MICHIGAN
From 18-MAY-20 14:00:00 to 19-MAY-20 23:00:00 (EST-5)
Location: DALE
Flood cause: Dam / Levee Break
Property damage: 6.50M
Crop damage: 0.00K
Reported by: Emergency Manager

Multiple dams on the Tittabawassee River system were in danger during and after the heavy rain event. Significant releases of water from Secord and Smallwood Dams caused periods of rapid, flash flooding downstream of those dams on parts of the 18th and 19th. Tremendous erosion of the river banks occurred, and some roads and properties were damaged. Those releases did manage to save those two dams. However, downstream, Edenville Dam was unable to be saved. That dam failed catastrophically on the evening of the 19th, releasing the contents of Wixom Lake to downstream portions of the Tittabawassee River.
Note that Edenville Dam was located just north of the Gladwin/Midland County line. The Tittabawassee River enters Midland County immediately after leaving the dam. Thus, the vast majority of the downstream flooding caused by the failure of Edenville Dam will be found in Midland County and other downstream counties. Also note that the indirect damages of the Edenville Dam failure in Gladwin County are considerable, but difficult to quantify. To just touch on one topic, there were hundreds of lakefront properties on Wixom Lake, behind the dam. That lake no longer exists, and those properties have seen loss of property value, and residents and vacationers see a lesser quality of life.