Forsyth MO. - For whatever reason (although I'll get into some in future
blogs), the two bodies of impounded water controlled by the Army Corps
of Engineers could just possibly get into trouble due to both recent and imminent future rainfalls. First, some factual information;
[Source – Wikipedia] 'The original purpose of the reservoir was
for flood control on the White River. The dam had been authorized a
month earlier under the Flood Control Act of September 3, 1943. The
reservoir has a fluctuation of 16 feet (4.9 m). When the
reservoir is above the maximum flood pool, excess water goes over the
auxiliary overflow spillway at the north end of the dam.
Table Rock Dam’s spillway capacity was
evaluated as a result of a dam safety program in the 1990s. Using
improved weather data and more modern technology and safety
requirements, engineers determined that the lake would rise ten feet
higher during the worst-case flood than previously calculated. An
event of this magnitude would over top the earthen embankment and
destroy Table Rock Dam with catastrophic losses in downstream areas,
including Branson. To prevent the potential loss of life and property
damages, congress approved and authorized construction of the Dam
Safety Project. After considering several options and gathering
considerable public input, an auxiliary spillway was determined to be
the best solution. The auxiliary spillway was completed in 2005 at a
cost of approximately $65,000,000.
The
worst case scenario of a
catastrophic floodwater discharge from Table Rock Lake using the
auxiliary floodgates would roughly resemble this:
At
elevation 931 Table Rock Lake is at full flood capacity. The
ten Tainter gates are opened to accommodate additional lake inflow
from the White River Basin including the James River and Beaver Lake
discharge.
At elevation 937 Table Rock Lake is 6 feet above flood capacity.
The ten Tainter gates are opened wider in an effort to stabilize
reservoir rise. Outflow from the Lake under these circumstances will
be nearing 200-300 thousand cubic feet per second (CFS).
At elevation 942 Table Rock Lake is 11 feet above flood capacity
and at its "design pool", or the maximum elevation that the
reservoir is engineered to reach, under "probable maximum flood"
scenarios. The dam’s ten Tainter gates will be fully raised to
their maximum height of approximately 30 feet letting loose 550
thousand CFS into Lake Taneycomo. This scenario would effectively
submerge and destroy the powerhouse, power transmission grid,
hatchery, and wreak serious destruction down stream.
At elevation 947 Table Rock Dam would be at its maximum capacity
and water would be at the very top of the dam. The auxiliary spillway
would be brought online, in concert with Table Rock’s fully opened
floodgates. This catastrophic or "last resort" protocol
releases 1 million CFS of lake waters into Taneycomo and deals
dreadful destruction to Branson, Hollister, Point Lookout and
possibly the Powersite Dam. At this point there is a danger of water
over-topping the concrete dam and breaching the earthen structure,
which imminently leads to cataclysmic structural failure and the
uncontrolled release of the Table Rock Lake impoundment—nearly 3
million CFS of water.
Historical facts: Table Rock Lake has a record crest of 935.47 feet, which occurred
on April 27, 2011.
In December 2015, the dam released 72,000 CFS at its peak. This is
the highest amount ever released.'
As of May 23rd, the water levels were at;
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| Click to enlarge |
Now while the smallest impounded Lake (Beaver) was doing OK, her two
downstream neighbors were carrying a bit of a load. The biggest worry
being Bull Shoals, currently at 693 feet or just two feet below flood
pool levels. Note that 'flood pool' as defined by
Law Insider reads;
30 (24) “Flood pool elevation” means the maximum water surface elevation of a reservoir, equal to the elevation of the spillway.
This is the point at which a dam would be forced to start discharging 'against the will of those in control'. (Note that the
Table Rock Dam level was at 926 feet with their flood pool set at 931 feet - That's 4 feet
away)! Also note that when were are talking about the height of a body
of water, we are referring to
msl or height above mean sea level.
So, even though the coming week of rain only equals
about an inch, the water game is certainly getting a bit dicey, to say the least!
