Lack of accurate data plagues geological predictions.
Whether we are assessing climate change, tropical storm probabilities, or the
significance of unseasonably warm temperatures there is only a small sample
size available. There may be semi-accurate data back as far as the early- to
mid-18th century, but one could debate that accurate data was not
available until the 1970's when the first Earth Resources Technology Satellite
was launched, now known as Landsat. A prime example of data issues is
exemplified by the 100-yr flood level.
The US Army Corp of Engineers continually strives to build
up levees and protect southern Louisiana from flooding down through New
Orleans. The ever increasing levees along with the Old River Control Structure
(ORCS), which regulates water flow from 'The Big Muddy' towards a more natural
course down through the Atchafalaya River safeguard the developed areas along
the Mississippi River Delta.
Without the 'The Big Muddy' there would be a lack of
sediment deposited on the now elongated delta, and subsidence along with tidal
erosion would wash away the City of New Orleans. The fight to keep New Orleans
safe requires a firm understanding of mathematical probabilities. The 100-yr
flood level is an elevation alongside a river bank where no structures can be
built. In lower Louisiana this law is not enforced as many urban developments
existed before such laws came into effect, and are grandfathered in.
Instead of regulating where we can build the State of
Louisiana relies on levees. Levees are built to a height that safeguards
neighboring areas with significant confidence that they can withstand normal
and even elevated river stages that are predicted to occur. Modern events suggest we are losing the battle
with 'The Big Muddy'. The St. Louis flood wall was rebuilt after the record
floods observed in 1993. The new levees are designed to contain a river stage
of 54 feet, 4.4 feet above the flood crest of 1993. On New Year's Day the Mississippi
River at St. Louis crested at its third highest level on record at 42.58 feet, and
again today we are witnessing significant flooding.
As quoted by Mark Twain, "One who knows the Mississippi will promptly aver-not aloud, but
to himself-that ten thousand River Commissions, with the mines of the world at
their back, cannot tame that lawless stream, cannot curb it or confine it,
cannot say to it, Go here, or Go there, and make it obey; cannot save a shore
which it has sentenced; cannot bar its path with an obstruction which it will
not tear down, dance over, and laugh at."
Image Credit: Wikipedia | CC BY-SA 2.0
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Re: Levees Fail Again
