Year: 1876

crevasse has occurred during


high water in the Bayou, the fal


occasioned above that opening


has been only temporary and wa,


soon recovered, whilst below tht


fall occasioned thereby remained


permanent.


The history of the MOreau Gre


vase in 1874 is cited as an exam


pie. When that break occurred


the Bayou was full-the water


running over the levee in many


places from DonaldsOnvillc to the


points below at which levees


cease.


A few days subsequent to that


crevasse the LafOurche was as


high above that breach as it was


previous to the occurrence, al.


though for twenty-five miles the


fall had been from one to twenty


inches whilst below, the sudden
fall which took place remained
until the water went down in the
Summer.


The survey made by the United
States Engineer Department dis,
closes the fact (Which is percepti-
ble to the naked eye) that the
capacity Of egress in the Bayou
opposite the plantation of Messrs.
Harang, is about one-third less
than is the inlet at Donaldsonville.
Now, how can the waters escape
when the natural outlet is mar.
rOwed down SO far below the ca.
pacity of the Inlet through which
they enter +! So long as the stream
is not full above, its waters will
pass out because the outlet, at
that point, is still equal to the
space occupied by the in.flowing
current.


The fact is selfevident that
when the Mississippi becomes full
so as to throw Il current of water
into the Lafourclle, equal to it's
full capacity OF reception that the
egress at Harang's will be INSULT
cient to pass it through, and,
operating as Il dam, will back the
water np Oh this portion of the
stream, until it overtiows the
levees, or, in it's rage. bursts them
i'll sunder and seeks an outlet over
the fields of rice and sngar-cane.


Now as regards the MOrean
CrevaSse and the fact above speci
fed in its history


The Bayou from a point some
five or six miles above that breach
did rise up to point equally as
high as it had attained previously
But this proves another fact That
break had no effect whatever up.
on the quantity of water that
found an entrance ut Donaldson
vile, and the fact that the Gre
vase had hut little influence
above, only goes to establish the
assertion that a requisite outlet
of the in flowing waters was all
that was necessary.


With a four.foOt levee for TWEEN
ty miles, the waters were res.
trained in the stream, because at
no one point was the capacity OF
the stream less than it was at the
inlet. Now, if the outlet at Mo-
reau's had been at Lafourche
Crossing, does any one suppose
that the Bayou above would not
have been sufficient to carry off
all the waters which entered a.
bove 7 and if it been at Raceland,
would not the same result have
been witnessed because the capaci
ty of the stream Is ut no point
above less than it is at its ii.let 7
If then a "crevasse," instead of
being made Oh the banks, should
be made in the channel of the
stream of a capacity, at uo one
point less than it is at the entrance,
why would not the waters escape
without forcing an outlet through
the leveesg The advocates of
high levees seem to ignore the
TACT that the cause of overfows.
and crevasses between Harang's
and Labatlieville is found in the |
fact that the outlet, being too
small to carry off the waters, oper
ates as a wall, holding them back |
and causing them to flow over or |
burst through the levees.


At Harang's the levees are on.
y about five feet high and from
above that is about !
the average, whilst between these
points levees of double that height |
are inadequate to sustain the
pressure Of the water when the
Mississippi discharges currents
INTO the Bayou equal to its receiv |
ing inlet.


At Harang's the stream can
rise no higher because tn e tides |
)t the Cult in their ebb and flow
lraw off the surplus, and the
same effect would be produced |,
we're the egress at that point |