New Orleans Republican. [volume] (New Orleans, La) 1867-1878, 1875-05-27

country. The shortest distance from hig
land to high land across what is usual
called the Mississippi swamp, that can
found between the Gulf and the mouth
the Ohio, is from Natchez on the easter
bank of the Missisaippi, to Harrison burg o
the western bank OF the Ouachita, a mea
ured distance Of twenty eight miles. Durin
every great over TOW the country betwee
those points is covered to an average dept
of at least seven or eight feet: this body G
water moves with strong current in d
rectiOn somewhat parallel with the cours
OF the Mississippi; cOmmingling itself i
part with the waters of the Ouachita and re
turning. portion of it by Red river to th
Mississippi. and large portion of it passin
BY the Atchafalaya toward St. Landry ant
the parishes on the Teche. Contract thi
body Of water to the width of one mile
and imagine it placed upon the river a
flood height. and you find you have in the
channel a height of water surprising tn
height of any levee ever built on tn
Mississippi.
know that those who advocate the all
sutficiency of levees alone as capable 0
atfOrding protection, dispose of call sucl
reasoning as this by their theory that Il
running water be confined, the current viii
| eventually wash out channel sutficien
for it's discharge" This doctrine is Ger
tain]y erroneous l regret to see that my
friend Mr.. King has fallen into it. have
seen this couplet somewhere:
Time but the impression deeper makes.
| As streams their channels deeper wear"
This may be tolerably fair poetry, but il
is not philosophy or science. Streams dt
not and can not be made to deepen theil
| channels through their whole extent.
| local obstruction producing q depth OF
| water less than the normal depth of the
ofr Vnou hn -.
means, restoring the proper depth of the
stream. But 1t is law of hydraulics that
streams maintain a uniform average depth.
If they could be made to cut their channels
one foot deeper than their normal average
depth, they might be made to cut them ten,
twenty, fifty or thousand feet deeper
There would be no limit to this process.
But following the law OF uniform average
depth, streams fill by deposit on their bot
toms. to the extent that their surfaces are
heightened by cOntining their waters within
their channels. Facts abound everywhere
to show that this is true. The river Tiber, at
Rome, IN ages past caused great injury by
frequently over1Owing the lower portions
OF the city, and resort was had to embank-
ments to restrain it's waters when suddenly
swollen from spreading with violence over
the fat grounds adjacent to it. My trend
who is well versed in the classics. will re-
the Odes Of Horace, where this stanza oc-
ours, commemorating the damage caused by
destructive inundatiOn Of the river that
happened shortly after the death of julius
Cesar
'Vidimus favum Tiberim, retortis
Litt0re Etrusco volenter undls
Ire dtject IN monumental Regis
Templaque vestae."
Resort was had, as already said, to build
ing levees to prevent these inundations.
Now, let US see what followed in after times
from the building of these levees to restrain
"the waves of the ruddy Tiber." In the
reign, l think, of the Emperor Titus,
gigantic system of drainage and sewerage
OF the great city was adopted. An immense
canal, called the Cloaca Maxma, was cut
throughout the entire extent of CITY in
order to discharge through it into the Tiber.
Lateral bitches and drains in every d.
rection were cut into and connected with
the main sewer. The bottoms and sides Of
this canal were constructed of solid ma
sonry, built in hydraulic cement, a solid
work. done as only the Romans did work
The bottom of that canal is there to day, as
perfect. and occupying the same level ex-
actly that it did in the days of Titus. The
bottom of the Tlber is now twenty seven
feet above the bottom of the canal. This is the
way that the channel of the Tiber was deep
eDed by constructing levees on it's banks.
Ihe river PO, in Italy, furnishes another
example. That river, after passing from its
mountainous districts, enters low, fat
country in its approach to the Mediterra-
mean, similar in some respects to our allu-
vial country. This fat country of the Pc
has always been subject to inundat:on.
Levees were resorted to, and from time to
time, instead of thereby deepening the chan
mel OF the Pc, they found it necessary to
adopt the plan of enlarging and heightening
their levees; and at the present day, at the
city of Ferara, on the Pc, their levees are
higher than the tops Of their houses. Simi-
lar results may be shown the world over,
wherever entertainments of rivers have been
made, because such results come from
natural laws and inevitable causes. What is
said by my friend in relation to the velocity
Of currents depending upon the body of wa
ter and the plane of its descent do not in the |
main object to. But all this is, l conceive,
outside of the issue. The main question re. |
ates to the capacity OF the channel tor the |
passage Of the water that is to pass through |
d. Can all the waters of the valley of the |
river that accumulate during !
4 season Of extraordinary floods be confined |
n their passage to the Gulf within the |
channel OF the Iiver2 The point make ia |
ity Of water is too vast to be restricted |
within channel having an average width
VI less than one mile. That no increased We
ocity OF the current whatever would suffice |
o pass along the channel such seas of water;
hat the higher the levees are built the
'igher the water would rise within them,
md for the want of space the water would
continue to rise until it ran over the top of
he levees and swept them Off Certainly
here is limit to the capacity of the chan.
lel for discharging water. If all the waters
+ the Gulf of Mexico were turned loose
bOve the mouth Of the Ohio and were to
low at speed OF ten miles an hour they
ould not pass off within the channel of the
liver ii 1t had embankments 100 feet high.
his is the matter to look at.
Let us not f0rget,what enormous auanti-
les Of water accumulate during a season of
eneral overflow. Let us consider what
ast volumes Of water were collected to-
ether to produce the great floods of 1913,
sl5, 1893. 1928. and especially that mon
ter flood of l779 or 1880, four feet higher
nan the highest of them. Such floods we
now have occurred. We know they may
ccur again. We know, and know it to our
,rrOw, that levees are impotent against
lem.
1t is high time to give up the notion
lat our alluvial country can be effectually
rotected by levees alone, against the great
Oods of the Mississippi. We have already
'ent money and labor enough to no profit.
is a losing game that one should
Sc up from and cease to play at any more
am pleased to know that the confidence |
eretOfore reposed in levees alone ia dimin- |
hing, and that many of our ablest en-
neers favor the idea of the auxiliary aid
outlets. TO this complexion must it
Ile at last" The sooner we realize this
nth the better What has to be done in
is direction it is PLAIN to be seen, but
hen and how it shall be done is a more
ticult problem. 1t is questionable whether
Q time is near at hand when levees
ID outlets adequate to the great 8
.ject can be accomplished. But that such ,
system should be adopted at once and