The New Orleans daily Democrat. [volume] (New Orleans, La.) 1877-1880, 1877-11-10
IMPROVING THE MISSISSIPPI.
TWO PLANS FOR THE WORK.
That of the United Statss Engineers ana
That Of Capt. Eads.

tent, ana Wnen once maze secure, their taxable
value and productiveness will be immensely in
creased.
Two plans for the reclamation of these lands
are now definitely before the country. One Is
known as that of the United States Engineers,
and the other as that OF Capt. Eads, the engineer
Of the jetties. The first plan is explained In
the report OF a commission authorized by Com
gress in 1874, of which Gen. G.. X. Warren was
president and Gen. Abbott q member. The re-
by the full Endorsement of Gen A. A. Hum
phreys. Chief of Engineers of tue Army. Capt.
Eads' plan is the very. opposite of the United
directly contrary to theirs, that one or the other
party must be greatly in error.
rest upon the correctness of what is known as
report in the following words: THE plan con-
ing by separate channels to the gulf such
volume of the flood discharge as shall be suffi-
s e to n beng ssniqo d9 b, the bt to sm hsgat
new outlets. 81; but says: 'FThsy ars eorrest Ii
struction exist" It. accordingly rseommends
the keeping open of all existing. natural out
let's. and especially Bayou : 'hmafalaya. m whtch.
now not only discharges nearly all the waters OF
waters Wat SGT Of the @ MssissppIP The Commission
closure of the crevasses. and the com pletion OF
the entire levee system from ape Girardeau.
Mo-, to the lower end OF the river and the ex-
tension of the leyees up the mouths Of the tribu-
taries and down the bayous far enough to
guard against backwater.
The commission assumes that the retention
Of all the flood waters between the leyees. when
the crevasses are closed will ncr"a "ase the height
OF the water, and thus require the levees to be
ent ones. It says: If we guard against the
crevasses by raising. and strengthening our
leyees. an elevation Of the high water mark. ex-
actly proportioned to the increased volumes
will be sure to occur. To co tain a quart OF
water, vessel must have exac ly the requisite
number OF cubic inches, and a like principle
applies with equal force to water in motion"
To, meet this Increased elevation of the high
water mark, it dec ares that it will be necessary
to build up the entire system from three to
eleven feet higher than the great food Of 1858.
Sever al hundred miles Of the leveess must be-
The cost of this entire system of works Is essi-
mated by the commission at s46,oOO.ooo.
Capt Eads published q. review of the commits
the theories and assump ons On which its plan
is based are un1uestionaby err oneous,, Hede-
ciares that every bayou and outlet Of the river.
and, ind ed every river in the world that flows
through bed formed by its own deposits,
prove that the outlet system" is not correct
its slope increases, and, abstracting part OIL
the flood volume will, therefore, inevitably pro.
repeats the same theories and assumes the ex.-
istence of the same conditions in rhe river that
were advanced to support the predicted failure
system for improving the mouth Of the river;
| and that not one Of these theories Is supported
the fats the have aeye9psd H. s
his views at considerable length. in the Mer--
chants Exchange, upon the levee gu sstion, and
success he has already secured at tne jetties will
give much weight @ to his opinions on this sub sub
hd We W presfebf f bia as bsey as possible
| Clpt Eads declares: l. That the great mass
Of sediment annually discharged into the sea IL
pended by the action of the current, and that it
| is OF pushed along the bottom Of the river. Q.
That the quantity upheld depends upon the ve..
the water. 3. That the quantity Of sediment an
nually discharged into the sea and over the banks
be, during any long period Of years, about equal
to the amount poured into the trunk by its trib-
ntaries during that period. II II discharged less
charged more the difference would have to be
taken from IT'S BED whereas there Is g. no 70 proof
mel during many % Years " III TSe scn Current RI mt mnst
therefore be so regula ed by the river that it
will discharge no more nor no less than the
From these facts Capt Eads declares that al
terations from the normal velocity OF current
produce deposit and scour, he normal velocity
being assumed as that rate which will uphold
and carry forward the sediment without loss or
increase OF quantity. BY the action OF deposit
| velocity when from any cause 1t has been dis
/ turbed. 1he aluvial basin being composed
wholly OF matters deposited by the current. it
can again remove them from the channel by
scour If the current be too rapid or add to them
by deposit il too slow.
|
river bed, is the chief element retarding the
current The inclin alton. Or slope of the sur
face of the stream. determines the intensity OF
rent rem thus, 4 the friction be e greater at at one
place than At another, and an equal current be
where the friction is greater than where it IS less.
| The normal current being absolutely necessary
to maintain the capacity of the channel unater-
| localities than others, we must expect to see
great diversity In the slope or inclination OF
the food lin line Of the river These diyersIties dc
| exist. The lowest slope exits In the 100
leans, where :, it is less than an inch and
| lists in the river from Cairo to Memphis, where
| it averages nearly five inches. and thes Bayou
Atehafalaya, where it is about six inches. As
especially from Cairo to Red river. bends caving
in. and cut offs forming, it follows that the
river must possess some means of establishing
and Altering these various slopes to regulate
the current so that through all these changes
| it shall maintain the capacity or size Of the
by scour and deposit. Too much el7city in-
ereases the snspending power Of the water. and
it takes up Eni the material OF which the bed Is
a deepen ing Of the chan mel and lowering Of the
surface slope, AS this is lowered rhe current falls
to toe nqrnal PEI rate and the scour ceases II the
burden; a portion falls and builds up the bot
tom: tom: T This A is called deposit AS the bottom
becomes more rapid until fina ly 1t flows SO
fast that the normal speed is established aad
deposit ceases. Raising the slope necessitates
raising the levees. Jus as the 81 pc can be
lowered can leyees be dispensed with. What
ever increa- es the resistance to the flow Of the
water makes sleeper slopes and higher levees
inevitable Friction of the bed OF he stream
does this to much greater extent than all the
other rearding influences combined. This is
least where the stream is narrowed, and it is
lessened in ratio as the volume is increased.
For instance, from Red river to the Passes, S0
miles the steep is about one and three quarter
ri giH
two equal streams. this slope would be much
sleeper in each and tn levees would have
to be higher Bayou Atchafalaya. at
Red river. takes oil abouF one tenth OF the
volume to the sea with a slope of
six inches per mile. II it took off half of it the
slope OF the main river wruId have TO be sleeper
than it is or it would dry up an Atchafalaya
would become larg' and fatt r, Ii the waters
OF the whole river were equally divided with