A Thumbnail Sketch of a Great Flood in Southeast Michigan; Sep 10-12th, 1986

I was well into my career when this took place with much of the
activity taking place over the NWS Flint's jurisdiction of 
Southeast Lower Michigan. However; the NWS Forecast Office in 
Ann Arbor and NWS Detroit also aided the region with river warnings
and radar information.   
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)
17 27.52   (9/12/1986)
23.30   (5/22/1996)
22.83   (3/6/1976)
*  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      
10) Monitor NOAA Weather Radio, television or radio for the
      latest warnings and information.
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian 

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