The New Orleans daily Democrat. [volume] (New Orleans, La.) 1877-1880, 1880-04-08
The CREVASSE.
Progress Of the Work Of the Board
Of State Engineers.
Bndeaving to Avert Disaster Which
Would Equal, at Least, the Mis-
fortune of 1863.

visited the Cr6Vass6 In the l6veeS OF JEFFERSON
parish opposite the upper portion of this city,
known now under the name Of the Sharpe Ore
vase.
In presenting his report of this abnormal
and disastrous fluent Of the Mississippi river
the reporter must apologize to the readers OF
the DEMOCRAT for again presenting substan-
TALLY matter which has already appeared Ia the
columns of this paper. 1t is necessary. how
ever SO to do to show the progress already
made In closing this dangerous breach. and to
depict the disaster dependent upon failure TO
rebuild the broken levee In the locality desfg-
mated.
On Saturday last the width of the Sharpe cre-
vase was measured by members of
THE MISSISSIPPI RIVER COMMISSION
and the results of the measurements summRr-
lied by Maior Harrod. member of the commits
sion from this State. On that day from nearest
land to land of the broken levee the distance
was sixty three feet. the greatest depth OF the
central eurrent was found to be twenty feet and
the minimum average depth estimated by our
ex- chief engineer twelve feet, On Monday last
the abrasion and attrition Of the crevasse cur
rent had cut away the ends Of the ruptured
levee and Increased the width of the breach to
about seventy.flve feet. where 1t has since re-
mained.
THE CURRENT VELOCITY,
as measured by the DEMOCRAT representative.
was yesterday q little over ten feet per second.
The volume of water therein entering was there
fore. 5000 cubic feet, G5,ooo gallons per second
In FIVE seconds Its supply was sufficient to sub
merge one acre of level land with no waste
outletsl to the depth of one foot. or to sink In
twenty four hours twelve inches under water a
tract of level land measuring little more than
Nv OF nj pf
country. provided there was no egress for the
waters from this country.
Fortunately there are numerous drains for
this enormous supply Of crevasse water to find
Its way to the sea without efYeetng more than
local damage.
THE PRINCIPAL DRAIN IS
the Bayou Barrataria. thence through des Oies
into Lake Salvador. and thence into Bayou des
Allemands, the Lafourche and other large
streams. Lower down Bayou Barrataria would
discharge portion of the surplus water
thirty miles below Haryey's canal.
Ap ass s ss by se Wasrs
this crevHsse. we're 1t left open, are the Belle
Chasse. Ste. Anne. Concession and. Concord.
which are from seventeen to twenty a sarse miles s
TO seven miles distant from aretna as the crow
flies. The first and third of these. in PLAQUE
Hds and T6omon
this city. They rank among he finest estates
in Louisiana. and enjoy the enviable distinction
of being. classed as thousand hogsheads PLAN
It is doubtful If it be matter Of interest. but
according to the formula Of Gen Barnard. Gen.
Eltet, Humphries and Abbot, and other eminent
hydraulic engineers and authorities on the
Mississippi river, the Sharpe crevasse is daily
deDositing upon
THE DELTA SOIL OF LOUISIANA
kIz I'LL
be dry after the Mississippi river falls below
the level of the del tn lands. or enough sediment
every day to make soil one foot deep on six
To repeat what has already been partially
expained before the crovasse is a break OF
about seventy five feet In width and twelve feet
Louisiana-a levee about ten feet high with
sixty or seventy feet base. An intact portion OF
An OLD LEvEE
(now rendered more Intact by Mr.. Ross. OF
Belechasse, closing the most important ada
cent break In it) is parallel with the new and
broken levee at a distance Of 600 feet. Below
the mouth of the crevasse, about one; third OF
a mile. the old leyee has been washed ne away or or
the crevaese about Two hundred yards. the old
levee has gone; but batture or sand bank has
aVerage deph o Tn6n aSo oo IN the @
vening space between the old and the new
levees. INN mediately In front Of the crevasse.
the water has an average depth Of six feet. The
water Immediately behind the crevasse In the
public road is about two feet In depth.
On either side OF the track, about $50 feet dis
tant.
WING DAM
Is being built from the new to the old levee;
These have eiightlV ennuex nnter snrfaee and
are about 600 feet long. OF course, as we have
shown by depicting the present formation or
status Of the old levee. the great volume OF
water comes into the crevasse from below.
Hence The lover wing dam T. the s ing
dams has been driven, and the steam nile
drivers are lying Idle near the ,crevasse. The
pss 1o arve9 eoM Wb
of the dams are, from outside Of pile to out
side, about eight feet. and the distance
Feet the donbe ROW Of H scsnne Is
then nailed along the sides OF the machine
piles from one end Iof the, dam to the other:
are driven at distance of two inches apart.
Thus the lower wing dam consists OF two par
allel wooden walls 600 feet long and eight feet
apart. Between these walls first hay ts thrown.
then sand bags are deposited until they rise
above the surtace Of the water. The lower dam
was completed ye! terday az midday 10 Within
200 feet Of the outer levee.
THE CHIEF PART OF THE WOODWORK
was entirely finished and 400 feet OF the straw
and earth work we're, done. BY this morning 1t
Will probably be finished unless ,underscourlng
shoal water will be easily made, as The piles are
already driven. Col. Hardee proposes. as is
customary In closing crevasses, to make q front
his wing dams, to prevent understanding and
relieve the dams of the hydrostatic pressure.
This pressure will OF course be enormouely " in
creased when the crevaese is closed, and the
wing dams will be subjected to about three
times the strain that presses against them now.
The water is now about feet deep on the out
side of the wing dams. and feet higher than
that on the inside. According to the rule first
by Torricelli, and followed by engi
neers of to-day. for every one foot altitude Of
column of water In the atmosphere there Is half
a pound pressure to the eauare inch on the
sides Of the surrounding vessel. The whole OF
these works. SO feet long and six feet high. are
therefore sui jected 10 a hydraulic pressure OF
one pound to the square inch: When they are
com pleted and there is no water on ihe inside.
there will sill be feet on the outside. The
lower works will then therefore be subjected o
the enormous pressure OF three pounds to the
square Inch.
Let the reader make the calculation and he
will be astounded to find the almost supernal
force an engineer who has 10 close an energetic
has to contend against.
Col. Hardee of course appreciates the above
stated fact. and is making preparati ms accord
ingly to meet the increased pressure from with