>>>>>It's a mean old levee, cause me to weep
and moan
>>>>>It's a mean old levee, cause me to weep and
moan
>>>>>Gonna leave my baby, and my happy home
The lyrics to the 1929 blues classic "When the Levee
Breaks" (the original recording can be found on the web) refer
to the cataclysmic flood that began when heavy rains pounded the
central basin of the Mississippi River in summer 1926. Swollen to
capacity, the Mississippi broke out of its levee system in 145
places, flooding 17 million acres, and affecting an area the size
of New England. Nearly a million people were displaced.
The levee failures in New Orleans during Hurricane Katrina are,
of course, fresher in the American mind.
>>>>>If it keeps on rainin', levee's goin' to
break
>>>>>If it keeps on rainin', levee's goin' to
break
>>>>>And the water gonna come in, have no place to
stay
The challenge is to change that tune: to develop the technology
to quickly seal a levee breach and reduce floodwaters through the
opening within four to six hours of detection - before the water
can do major damage.
Enter Wil Laska of the Science & Technology Directorate
(S&T), the research arm of the Department of Homeland Security.
Laska has sought out innovative technologies from industry,
academia, and government to meet this challenge. Any proposed
system, he dictated, had to not only be capable of quickly closing
breaches, but also be suitable for scenarios in which the breach
may be difficult or impossible to reach with conventional
construction equipment.
"The thing is," Laska deadpans, "there's an effective structural
material that's readily available during
floods…water."
He found four technologies that met his requirements, and on
Nov. 9, 2009, all of them passed their second test at the U.S.
Department of Agriculture's Agriculture Research Service, Hydraulic
Engineering Research Unit in Stillwater, Okla. The facility is used
by the Army Corps of Engineers to test hydrology equipment and
study water flow, dams and levees.
The largest technology, proposed by the Army Corps of Engineers
Engineering Research and Development Center in Vicksburg, Miss., is
a large balloon or tube - light enough to be transported by
helicopter and flexible enough to adapt to a wide range of
environmental situations. When launched or dropped, the engineers
hypothesized, the tube would in quick succession fill with water,
float on the flood currents to the breach, and adhere to the breach
in the earthen berm or levee that had failed.
It worked.
Dubbed the Portable Lightweight Ubiquitous Gasket (PLUG),
the tube of non-stretch fabric is dropped into the floodwaters and
an attached pump rapidly fills it to 80 percent capacity - a bubble
of air inside keeps the tube from sinking beneath the waters.
Positioned upstream, flood currents pull it toward the breach. The
incompressible nature of water and the unyielding fabric turn the
tube into a rigid plug that conforms to the breach and seals
it.
Monday's PLUG demonstration was about 30 per cent larger than
the ¼ scale model that was first successfully tested in
September 2008. The Stillwater site is currently the only facility
that can provide the water flows needed - 125 cubic feet per second
for several minutes.
While the PLUG system is designed specifically for narrow, deep
breaches, several other solutions tailored for other types of levee
breaches were also tested on Nov. 9:
*A smaller version of the PLUG–designed to prevent the
over-topping flow of a long, shallow breach.
*The Rapidly Emplaced Protection for Earthen Levees (REPEL) -
designed to protect against erosion during the intentional
overtopping of levees, mitigating erosion from the back slope of a
levee which over time could cause a deep breach.
*The Rapidly Emplaced Hydraulic Arch Barrier (REHAB) - an arched
tube designed to hold back a surge of water during a levee breach
repair, to seal breaches obstructed by debris or other structures,
and to be used as a rapidly emplaced surge or flood gate.
>>>>>Oh cryin' won't help you, prayin' won't
do no good
>>>>>Oh cryin' won't help you, prayin' won't do no
good
>>>>>When the levee breaks, mama, you got to
lose
Engineers could be on their way to writing a less bluesy version
of a 90-year-old song:
>>>>>When the levee breaks, mama, you may need
a PLUG.
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