New Orleans daily crescent., 1866-02-01
PROTECTION AGAINST FOUNDATION.

An vve stated IN an article few days ago, Gen.
umphreys, in his admirable, and we may almost
" his exhaustive, report on the Mississippi river
scusses and analyses the various plans which
ave been proposed for protecting the riparian
,nds from inundation. These various plans are |
II embraced in three general systems: Frst'
to modify the actual relations existing between
he accelerating and retarding forces III the ehan
sel in such a manner as to enable the former to
carry off the surplus food-water without SO great
rise in tho surface as they now require 10 THIS
svstem belong eut-offs. Second, to reduce the
ma x;mum discharge of the river. To this system
h.,ono diversion of tributaries, artificial reser-
unirs and artificial outlets. Third, to coniue the
water to the channel, and allow it to regulste its
own discharge"
The nractical effect of cut-offs in single bend
Of the Mississippi may be determined by an ex-
animation of the history and results Of the Red
River and Raccourci cut-offs. 1t is remarkable
that the disastrous consequences OF those works
were predicted by P. 0. Hebert, afterwards Cover.
nor, and then State Engineer He demonstrated
against the scheme, but his warnings were un-
headed. The subsequent drafts on the State
Treasury proved the wisdom of his opposition and
the folly of refusing to listen to the deductions oil
science. Gen. Humphreys after minute and
careful examination of the eqeestion comes to the
conclusion that cutoff raises the surface OF the
river at the foot of the cut, nearly as much as II
depresses the water level at the head. The coun
try above is therefore relieved from the floods
only at the expense of the country below. More
over, if series of cutefs were made, extending
to the mouth of the river, the principles educed
show that the height of the foods would be re-
gularly decreased from a point near midway Oh
the SERIES to the upper end, and regularly III
creased from the same point to the lower END.
The system, therefore, is totally inappcable to the
Mississippi river.
The first proposed application of the system OF
"diyertinr tributaries" beginning at the Nofth,
is on the Upper Missouri, which stream, 1t IS sug
eested might be turned into the Red River of the
North. In the first place the project IS impractl-
o,b1o IN account of the immense cost of exc
cutino the required work. But even feasible the
enterprise would be useless, because the floods
from this part of the Missouri are little to be
feared below the Ohio, and have no dangerous in
fuence even at ST. Louis.
The next tributary to which it is proposed to
apnlv this plan is the Arkansas. 1t has been sug-
rested that the foods of this stream be turned
into Bayou Bartholomew or Bayou Macon. This
plan likewise would be costly; but it would un-
doubtedly relieve the country between Napoleon
and Red River Landing. As at.the latter point the
foods would again make their appearance, of
course the relief would be only partial and local.
But besides the danger of injuring the navi-
cation Of the Arkansas, the plan would afford
protection only against certain classes OF floods,
to-wit: those in which high water in the Misss-
sippi and high water in the Arkansas are stimuli
taneous. In the great July flood of 1858, which is
the basis of Gen. Humphreys argument, the Ar
kansas was low ,and its diversion would have given
relief only to the extent of 1000 cubic feet pei
second, whereas a diversion of zoe, 900 cubic fee
was required. The works necessary to guart
against such food as that of '5S would be sufi
cient protection against any probable combination
Of foods in the two rivers.
In the case of Red River the same apply witt
the modification that the prospective advantage
are materially less and the inevitable difficulties
much greater. To close Old River would be dis
astrous Generally the Atchafalaya serves directl,
or indirectly, as apeficient outlet for the foods
the Mississippi. The discharge of Red River a
its mouth in foods caused by its own drainage i
225 900 per second, while the discharge of tn
Atchafalaya is only 100000 cubic feet per second
If, therefore, the entrance of Red River to TIL
Mississippi should be closed the Red River valley
the settlements along the Bayou de Glaize, and tn
Atchafalaya basin would all be deeply inundate
at the recurrence of every Red River food.
In regard to the reservoir system the deductio
is that this, too, is inappcable to the Mississippi
The pretensions of the system are, by means O
| reservoirs which must be situated in the uppe
mountain region, to protect the whole delta, an
the borders of every stream in it, primary or trbu
tary," against inundation. Now, to effect this OBJ
iect say during the great June flood Of 1858, no
more than 1,o5O,O00 cubic feet per second SHOULD
have been allowed to enter the head of the allu
vial region. But during the thirtysix days from
May 25 to June 20 inclusive, the amount of water
passing the latitude of Columbus exceeded by
648 liz 500 900 cubic feet, the amount resulting
from discharge per second of 100000 cubic
feet Consequently the reservoirs relied on would
have had to keep back this enormous mass o
water during single month. An examination O.
the monthly rainfall in the mountain region shows
moreover, that the drainage area required woulG
be 80, 900 square miles, extent far larger thar
the whole mountain region drained by the Ohio.
To conclude this branch of the subject it is shown
that to protect the alluvial region alone by this
system would require an expenditure, on the est
mate of Mr.. Ellet, its most distinguished supporter
of s2l5 100000.
As to the outlet system, the conclusion is inevi
table that SO far as the river itself is concerned
they are of great utility" But this solves only
portion of the difficulty The water taken from
the river still remains to be disposed Of Crevasse
solve this problem by discharging the water int
the swamps. These natural drains, however, ar
insufficient, and the back water gradually rise
until the country is submerged up to the rive
banks. To make the plan practicable, an outlet t.
the Gulf must be prepared, and as this difficult.
can hardly be overcome, the system is of compar
atively little efficacy for protecting Louisiana
against overflow. As to the natural outlets on tn
right bank, the Atchafalaya, Plaquemine and La
fourche the cost of sufficiently enlarging then
would be so great that the project is virtually i'm
practicable On the left bank, to be of any avail
stream mile and a half in width would hav
to be opened to Lake Pontchartrain Such an out
let would be IS 400 feet wide, its discharging ca
pacity 800 900 cubic feet per second, and the mea
velocity of the water3.0 feet per second. 1t woul
have to be well leyeed for the whole distance, an
would be very costly work. Moreover, it woul
absolutely ruin Lake Pontchartrain as a navigabl
sheet of water. In the of time by the deeper
ing of its bed, the new outlet would become q lo'
water, as well as high water branch of the Miss