September, is generally a transition month between summer and fall, and brings a taming of the summer heat and thunderstorms. Normal rainfall amounts drop off from the summer maximum and the weather, more often than not, goes into more of a tranquil period before the fall storms begin to rage. But this was not the case on September 10-12th, 1986 in Central Lower Michigan into the “Thumb Region” of Lower Michigan.
Several estimates about the likelihood of such a flood like the one in 1986 were tossed about such as a “100 year flood” or a “500 year flood”. But to the people of the flood stricken area it is known as “The Flood”! A number of rain events plagued this area through September but the main one occurred September 10-12th, 1986. The flooding rains were triggered by a nearly stationary front which, like the flood area itself, stretched east-west across Central Lower Michigan. Warm, moisture-laden air from the Gulf of Mexico (enhanced by a moisture plume from remnants of a tropical system over the Eastern Pacific), streamed north and east out of the Midwest, across the stationary front into Central Lower Michigan. To the north, cooler, drier air remained entrenched over Upper Michigan. The upper wind pattern across the Great Lakes was conducive in holding the surface front nearly in place, resulting only in a slow drift to the north through the entire period. This in turn, caused any available moisture pushing north across the front to be wrung out and dumped persistently over the same general area.
An extensive area of heavy rain and severe thunderstorms with torrential rains developed just north of the front and extended west from Michigan into Wisconsin. As the moisture from the south overran the front and fell as heavy rain over Central Lower Michigan, it also traversed the same area from west to east during the two day period. This process of precipitation developing and repeatedly moving over the same area is known all too well by meteorologists and hydrologists as “train-echoing”. This was the primary mechanism for the persistent heavy rainfall during this particular flood event.
The rain began late Tuesday night, September 9th, over West-Central Lower Michigan and steadily moved east across Central Lower Michigan and into the “Thumb Region” of Southeast Lower Michigan overnight. Rainfall during the September 10-12th period over Central Lower Michigan averaged an incredible 6 to 12 inches, with even isolated reports of up to 14 inches. Much of this deluge fell in a 12 hour period on the 11th. The table below has the rainfall amounts for selected observation points across Southeast Lower Michigan. The September 1986 rainfall ranks as the wettest month for Saginaw, the 3rd wettest month for Flint and the 11th wettest month for Detroit. Here are some rain fall totals in the eastern part of the state Midland 18.35” MBS (tri city airport) 16.16” Bay City 15.86” Caro 18.16” Cass City 16.24”
In the western part of the state with 11.85” of rain it was the 2nd wettest month at Grand Rapids. Muskegon seen 13.55” of rain.
Here is some information of the flooding in the Saginaw Valley
o Tittabawassee River (Midland)
Crest: 33.89 feet, Flood Stage: 24 feet
o Saginaw River
Crest: 24.16 feet, Flood Stage: 17 feet
o Pine River (Alma)
Crest: 12.82 feet, Flood Stage: 8 feet
o Cass (Vassar)
Crest: 24.82 feet, Flood Stage: 14 feet
o Cass (Frankenmuth)
Crest: 27.52 feet, Flood Stage: 17 feet
Some of the most notable impacts from this flooding occurred with the Cass River in the town of Vassar. The river which has a flood stage of 14 feet, rose to over 10 feet above flood stage.
Vassar was one of the hardest hit areas with many flooded homes and downtown businesses, and with the river rising so quickly, some residents barely had time to get to safety.
At the end of the event, 22 counties in the state of Michigan were declared disaster areas. This occurred over an area of 14,000 square miles, with an estimated 1.8 million residents.
Total damage costs were estimated to be between $400 and $500 million dollars at the time, or around $850 million to $1 billion dollars today. Out of that total cost, approximately $120 million ($260 million today), was due to crop damage.
Unfortunately, the flood claimed the lives of at least 10 people. Those lives lost included a hunter on the Muskegon River, a woman who drove her car off a flooded road into the Cass River, two children playing near streams that were swept away, two people that drowned in boats that fell overboard, and two men who were electrocuted operating sump pumps.
In addition to those fatalities, two farmers lost their lives by suicide after seeing the damage to their crops. Injuries in the flood were an estimated 100 people.
I know that there is a lot of speculations as to what kind of winter this year will have. Here in GRR we now have had 2 winters in a row with below average snow fall. (61.1” in 2015/16 and 60.1” last winter) well going back to 1950 the longest string of below averages snow fall winters was 4 believe it or not was in the 1970’s from 1972/73 to 1975/76 when 65.5”, 64.4”, 68.9”, and 69.2” fell. The longest streak (of below average season snow fall) since 1976/77 has been two winters in a row and that has happened several times. Now So far, this September here in Michigan has been rather dry as of today GRR has only had 0.56″ of rain. Looking at past Septembers where less than 1.5″ of rain has fallen in September, I found 10 such September’s where that has happened. Of the 10 years the next winter GRR seen less snow than average in 5 of them, More snow that average in 3 and near average in 2. There was no reason as to why I picked 1950 as a starting point.