Ken Anonymous
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Wetlands restoration will produce an unstable Miss - 2007/10/28 21:54
Wetlands restoration will produce an unstable Mississippi River?
LA Speaks Draft Master Plan will not work because a river
environmental disaster will occur with the plan as proposed
A shipping terminal has fallen in the river in the past (1974-75? near
Plaquemine, La.) from high velocity water but I am sure the terminal
was designed to meet government regulations with respect to piling
depth...etc. After this event several diversions were added to the
river and this has added piling undercutting capability to the river
due to added velocity. Adding more diversions in the future may be the
straw that breaks the back and, I believe, more shipping terminals
will fall into the river. There should not be any added diversions
that increases river velocities except for diversions close to the
mouth of the river. Diversions close to the mouth of the river
essentially do not increase river velocities and do not decrease the
resistance of the river. But any diversions above the mouth of the
river decrease the resistance of the river by creating a parallel run
with the river. This parallel run starts at the point of the river
diversion and continues downstream to the Gulf. These added diversions
will decrease the downstream resistance and river velocity north of
the diversion will be higher than before the diversions are added.
"A combination for shipping terminals to fall into the river"
I believe there is nothing that can be done to stop the added erosion
power of the river from undermining shipping pilings. Also I believe,
grading, armoring the river bank with stone, and installing concrete
matt on the river bank will not stop the erosive power of the river,
from higher velocities, undermining the levee at peak meander points.
And this undermining of the levee will send a destructive tidal wave
into Southeast Louisiana.
The Mississippi River Master Plan diversions will only work if:
· All future diversions are close to the mouth of the Mississippi
River.
· Or the total flow of the bird foot delta area is decreased by the
added upstream diversion flows.
A magnitude example of possible diversions
The Third Delta Conveyance Channel may well destroy Southeast
Louisiana because the levee above Donaldsonville, Louisiana will be
undermined. Higher river velocities above Donaldsonville will be
generated by the Conveyance Channel flow because the flow will
decrease the river resistance below Donaldsonville. These higher
velocities will undermine peak meander points of the river above
Donaldsonville and in turn the levee will be undermined and collapse
sending a tidal wave south.
Please see below article that shows stream channelization increase
flow velocity.
I believe one can safely conclude:
· Stream channelization reduces the resistance of a stream and this is
why the stream has faster velocities.
· For the Mississippi River, approximate 1/3 of the river diverted by
the Third Delta Conveyance channel will reduce the resistance of the
river and as a result the velocity and the erosive power of the river
upstream of the diversion will increase.
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...Because overall stream behavior is maintained in dynamic equilibrium,
changes in one of several variables such as flow, velocity, or
streambed substrate will result in compensating changes in the other
variables. Channelization and armoring (rip-rapping) of a stream
section will cause permanent changes, removing the dynamic nature of
not only the altered section, but also affecting the adjoining stream
sections further downstream than might initially be anticipated.
Stream channelization often increases stream velocity, thereby
increasing the erosive power of the stream. Durable protection or
armoring is then required to ensure the stability of the engineered
modification through all flow events....
http://www.fws.gov/midwest/KalamazooNRDA/documents/IChap_8.pdf
Page 5
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Please visit the below site to save Louisiana's wetlands.
This site is the Master plan site.
Louisiana Speaks
http://laspeaks.blogspot.com
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Post edited by: wetlandsrst, at: 2007/10/28 21:00
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