Thibodaux minerva. [volume] (Thibodaux, La.) 18??-1858, 1854-03-11

uO 1Ol1llS II,
only so much water as the bayou is able to dis
charge through its least dimensions, and large
enough to admit of the passage of such steam
boats as ordinarily enter it. This plan, without
doubt could be executed in such manner as
would secure the country from overflow, and
would not, at first seriously interrupt the
navigation; but in addition to the objections
which might be urged against the first plan, and
to which it is nearly equally liable, it is objec-
tionable on several other grounds. First, the
great expense of its construction and main
tenance and secondly, its effects upon the bayou
itself. There can be no doubt that this plan, if
put in execution, would cause the whole bayou
to be filed up, within limited time, by the de-
posit of sediment resulting from it's consequent
diminished velocity.
The third plan proposed is to dispose of the
surplus water by means of an outlet. This being
the measure, if any, it is supposed will be adopt
ed, have given to it the greatest possible at
tention. which the limited time allowed for this
investigation would admit, and have thoroughly
examined all the sections of the country neces-
| sary, in order to determine where this plan can
best be executed.
On the right bank of the bayou no outlet can
be made, sufficient for the purposes required,
except by the construction of several extensive
new channels, and great enlargement of bayous
of much k1gth, before the surplus water could
be discharged into any of the bays of the sea.
This great distance would so considerably dim
inish the amount of fall per mile, not to afford
| sufficient velocity to keep open the channels.
On the left bank Of Bayou Lafourche an out
let can be made with great facility, amply suf-
fcient not only to protect the country from over
flow, but if desired, so worked as would prevent
the injury resulting to the early growth of crops
by the flowing of Transportation water through
the levees and thence through the bitches in the
fields; and also requiring but little hereafter
to be expended for the maintenance Of the levees.
The best point to locate it, taking all things into
consideration, will be found about six miles
above Lockport, and at distance Of about eight
miles, discharging the water into Bayou des
Allemands, at point ten or twelve miles above
| lake Ouacha or Salvador.
The cross section of Bayou des Allemands,
shown on diagram No. Is, is equal to ten
thousand five hundred and eight square feet, and
| is q tide water bayou, with a moderate current
running either way, according to the tide. Lake
Ouacha is body Of water about ten miles wide,
and fifteen miles long, averaging about twelve
feet in depth, and may, from the great capacity
of its outlets, be considered, for this purpose,
as equivalent to the sea.
In case it shall be determined to make the
lost in commencing the work, if it is desired to
serve for protection from the high water of next
season, as about three-fourths of the channel
and levees to be made can be executed to the
best advantage with . steam excavating ma
chine, which will require some time to procure
and have ready to put in operation.
A uaste-,ceir on the bank of the bayou at the
head of the outlet will be necessary, in order to
govern the amount of water to be discharged
through it, and it will be of the utmost impor-
tance in case this work shall be ordered, that it
should be put in charge of a competent and er-
perienced Eng gineer, or else there may be great
risk of failure. Waste-weirs appear to be SIM
pie enough to the casual observer, but the OBJ
servations Of all engineers who have had much
experience OF their working, even on so small a
scale as on canals proves that the utmost eau
ton and skill must be observed in their con-
struction, or they will become undermined. If
properly constructed they admirably perform the
services required Of them, require but little ex-
pense for maintenance, and can be easily gov
erned SO as to discharge exactly the amount Of
water desired, and no more. An outlet made
without the security afforded by o waste-weir,
might very likely become unmanageanle, by
reason Of the peculiar nature of the earth COM
posing the banks of the bayou and oulet, and
also by reason of the large amount of sedimen-
tary matter contained in the water, which is
liable to be deposited under certain circum-
stances. It thus might operate so as to cause
damage by overflow, though in another locality,
to an amount equal, or nearly so, to what might
be expected to accrue in the absence of any i'm
provement.
From the data as yet obtained it is not pos
sible to estimate very exactly what will be the
amount of money required to construct chan
mel, leyees, waste-weir and bridge, such as may
be suitable to the case. Some additional data
are requisite, even before it can with safety be
determined what dimensions should be given
them. 1t is believed, however, that the sum OF
one hundred thousand dollars will be more than
sufficient. 81
The resolution calling for this investigation
requires that the causes of the formation of the
Instructions found in Bayou Lafourche shall be
reported on. The undersigned, from his resi-
dence and avoeations, has possessed favorable
means Of observing the changes which have
taken place in said bayou, during the last 2e
years. According to his observations the bayou,
during that period of time, has been gradually
: and greatly increased in its dimensions in the
upper section, and very materially diminished
in the lower section, and this change appears te
be yet in progress. @s.srs
i The primary cause was the partial closure d
the bayou about ten miles below Leckpert, II
the year 1914, by order of General Jackson, In
order to protect the country from invasion. This
obstruction consisted of trees and logs thrown
In the channel, which formed nucleus for ths
formation of the middle banks which are show1
ON diagrams Nos. 4, 5, 6, L, and 8.
The secondary and more effective cause re
suits from the constant navigation by steamboat,
, of the upper section only Of the bayou since
that time. They rarely pass below the point.
where the distractions exist In stream O
: so small dimensions IS this bayou, running
through alluvial and loose earth, generally, ths
passage Of each steamboat stirs DIP the mud OF
the bottom and sides considerably, and tn
velocity Of the current being sufficient, the mud
and earth thus loosened and put in motion, il
transported to tie lower section Of the bayou
whose banks and bottom are left undisturbed
and it is there deposited. That this process
and other minor causes, have been in constan
! operation for many years is certain, that the,
do and will continue is equally certain, and vii
eventually result in an almost or entire closur,
of the bayou between the point where steambca
navigation ceases, and the point where the tida
currents are Sufficiently active to prevent de
lposits. This work has now progressed to sucl