...A Thumbnail Sketch of a Great Flood in Southeast Michigan... By: Bill Deedler, Weather Historian, WFO Detroit/Pontiac Mi
September, being somewhat of a transition month between summer and fall, generally brings a taming of the summer heat and thunderstorms. Normal rainfall amounts drop off from the summer maximums 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 the "Thumb Region" of Southeast Lower Michigan.
In the worst flood devastation in 50 years, total damage was estimated between 400 and 500 million dollars. Of that total, around $120 million was crop damage, since the flood came near harvest time. The entire flood area covered generally a 60 mile wide band across the central portion of Lower Michigan. The central axis of the flood area extended from north of Muskegon, near Rothbury, east across all of Central Lower Michigan to near Port Sanilac, in Southeast Lower Michigan's "Thumb Region". Some major cities in Southeast Lower Michigan affected by the flood included Saginaw, Bay City and Midland. It is interesting to note that the city of Flint actually experienced more severe flooding in September 1985 than it did in September 1986.
Several estimates about the likelihood of such a flood like the one in 1986 were tossed about such as, it was a "100 year flood" or even 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 heaviest band of rain over Southeast Lower Michigan for the two day period extended from the Alma area, east across Saginaw into Vassar. As a result of these monsoon-like rains, several rivers surged over their banks and established record heights (see table below).
|River||Flood Stage||Crest (date)||(old) Record (date)|
|24||33.94 (9/13/1986)||29.70 (3/28/1916)|
|19||*24.16 (9/15/1986)||*24.90 (3/30/1904)|
|8||12.82 (9/12/1986)||10.81 (3/13/1948)|
|14||24.82 (9/12/1986)||20.80 (3/30/1948)|
|* Saginaw River at Saginaw did not establish a new record height|
The Cass River at Vassar with a flood stage of 14 feet, rose to an unprecedented (and almost unbelievable) 24.82 feet, or better than 10 feet above flood stage! This level of nearly 25 feet is even more astonishing, when you consider the normal height of the river is about 4.5 feet. Likewise, the Cass River at Frankenmuth rose to around 10 feet above its flood stage with a 27.52 feet reading (flood stage is 17 feet). Coincidentally and interesting to note, the Cass River at both Frankenmuth and Vassar has had record (or near record) flooding every 10 years since 1976.
Like many locations in and near rivers and drainage areas, the flooding in the town of Vassar was a nightmare! It was definitely one of the hardest hit areas with all the downtown businesses and about 50 homes being flooded. The flood waters reached to the intersection of Main and Huron St. on the northwest side of the Cass River and extended to the intersection of Huron and East St. on the southeast side. The river rose so quickly and forcefully, that some people barely had enough time to get out. Several people awoke in Vassar to find their streets and cars covered in rushing water as the raging river surrounded their homes and businesses. But further downriver on the Cass, at Frankenmuth, vigorous sand bagging on top of permanent levees protected the downtown area from any serious flooding.
Several people lost their lives either directly or indirectly due to the flood. Looking through newspaper articles and related storm reports, at least 10 people died. The body of a hunter was found on the bank of the Muskegon River, a woman who drove her car off a flooded road into the Cass river, two children playing near flooded streams were swept away, two more people drowned while in boats, falling overboard; and another two men were electrocuted while using sump pumps in flooded rooms. Sadly, the flood also took its toll on human life in another, devastating way. Two farmers, after seeing all their crops under water, committed suicide. Close to 100 people were injured in the flood, whether it be during preventive flood procedures or during cleanup activities. Across Central Lower Michigan, 22 counties were declared disaster areas. This encompassed nearly 14,000 square miles and where 1.8 million people lived. Even though damage was estimated between 400 to 500 million dollars, it hard to put a dollar figure on the huge amount of personal items these people lost and also, the emotional scars some still carry with them. To give an idea the volume of water that fell over Saginaw River basin, it was estimated by the state hydrologist (at that time) that if that water could be drained into Lake St. Clair, it would raise its level 10 feet! The Bay City Times, in retrospect, summed up "The Flood" well by telling their readers to just scan the "D" listings in the dictionary,"its all there, Downpours, Drenching, Devastation and Disaster"!
Two key elements that contribute to flash flooding are rainfall intensity and duration. Other factors that play important roles include soil conditions, topography and ground cover. Flash floods cause more deaths each year in the United States than either lightning, tornadoes or hurricanes! In the 20 year period from 1972-1991, on an average, 146 people were killed every year from flash flooding. Lightning claimed 80 lives per year during the period, tornadoes 69, and hurricanes 17.
The National Weather service issues Flash Flood Warnings when flash flooding is occurring or imminent. Remember the following when you are in a flood situation...
1) Get out of areas subject to flooding, including terrain low spots, dips, canyons, washes, etc. 2) Avoid already flooded and high velocity flow areas. Do not attempt to cross flowing streams 3) If driving, be aware that the road bed may not be intact under flood waters. Turn around and go another way. NEVER drive through flooded roadways! 4) If your vehicle stalls, leave it immediately and seek higher ground. Rapidly rising water may engulf the vehicle and its occupants and sweep them away. 5) Be especially cautious at night when its harder to recognize flood dangers. 6) Do not camp or park your vehicle along streams and washes, particularly during threatening weather conditions. 7) Do not let children play around high water, storm drains rivers or creeks. 8) If advised to evacuate, do so IMMEDIATELY! 9) Move to a safe area before its access it cut off by high water. 10) Monitor NOAA Weather Radio, television or radio for the latest warnings and information.
I wish to thank my fellow employees Mr. Jeff Boyne and Mr. Dick Wagenmaker of the National Weather Service, Pontiac/Detroit and also, Ms. Ann Tomcho, a cooperative weather observer in Akron, Michigan for their contributions to this article.