The New Orleans daily Democrat. [volume] (New Orleans, La.) 1877-1880, 1878-06-13

4 Ii
tives, Forty-fourth Congress, first session.,
upon his reconnaissance OF the Mississippi
river from Cairo to the mouth oil the HE'D
river, with O view to cheap transportation
routes To the seaboard, and his general project
for surveying and improving the river, for
which he asked aS first appropriation
the year 1876-the sum OF $2O0,0OO to begin
the Improvement, and $4,000 for surveys, u
will be found that he states that there
are thirty-five places where there is
! less than eight feet depth at low water
| twenty-five where there Is less than seven
| feet; nineteen where there Is less than six
feet, and thirteen whore there is less than nve
feet and that to obtain eight to ten feet depth
| at low water, from five to twelve miles oil
river at each Of these places must be Inn
proved, and probably other places would need
works Of Improvement or maintenance.
| That is, to obtain from eight to ten feet at
| improved, and this he stated could only be
secured at very great cost.
The report describes the bars the manner
of their formation, the general nature OF the
bed and banks of the river; the means, gener-
ally that must be resorted to to deepen the low
water channels and to maintain the depths,
and the precautions 10 be used In proceeding
with the work, lest new distractions to navi-
CATION should be created In the process OF the
Improvement A. careful peru5al OF this able
sional persons, that to obtain low-water
depth OF eight to ten feet is work OF great
magnitude and cost, and one Of great difficult
ty and to be proceeded with cautiously -care-
ful surveys and plans preceding the constitute
tlon Of dams, dykes, etc, and other work.
1t will not be dif1iult to understand that to
obtain twenty feet at low water the works
must extend over o much greater length OF
river and at much greater cost. In fact the
information does not exist upon which any
nnftpanfa no made nF fhn extent and cost
Of works necessary for O 20-feet iow-water
channel. The survey now in progress will
furnish the data for the discussion OF this and
other questions.
tion-that Is, to lower the flood level to the
natural bank suppose depth of twenty feet
at low water secured over the thirty-five bars
enumerated, the average deepening over them
must be about fourteen feet. The mean ve-
locity of the current In high water of the river
is from five TO six feet per second; In low
water about two feet per second. The mean
high-water width la about 4400 feet;
the mean low-water width Is about 9400 feet,
How much must the lOw-water widths OF the
shoal localities be reduced In order to increase
the current of two feet per second to one OF
sufficient strength to scour out the fourteen
feet Of shoal, supposing these bars to be COM
posed OF such material as TO admit OF the
securing required2 We shall find that this
reduced IoW-water width, over which the
afford too small an increase In the depth OF
the high-water area of cross section to mate
rally lower the food level of the river In the
localities improved, while to prevent the flood
overflow this level must be lowered to that OF
the natural bank throughout the whole length.
This lowering Of the surface Of the flood must
amount to not less than twelve feet as that
would be the average elevation OF the surface
Of the river in flood above the natural bank
between Cairo and Red river, IL the whole
xfpi nf flood Htunhu rDSn rAntFainad nv
levees.
If the bed of the river, to the extent of It's
mean width, 4400 feet, could be deepened, on
an average, twelve feet not only over the 300
miles Of shoals, but throughout It's entire
length, the flood surface would sink to the
natural bank.
It is not practicable to deepen materially
the whole bed of the river. Ii the width be
reduced the depth must be correspondingly
increased beyond twelve feet. Above Red
as it is below Red river; the depth Is about
one-half what ii Is below, the area OF cross
section In high water being about the same
above as below. Suppose 1t were practicable
to effect the two objects sought by reducing
the mean width of the river, and that this re-
duction of width would deepen the bed to the
extent required. This canalization would re-
quire works on both sides of the river, reach
Ing up from the bed to the high water sur
face-for the banks are composed of material
hence it's great width Throughout the whole
length to be improved. the true bed under the
moving sands and moving gravels of which
some Of the bars or their upper surfaces are
formed Is not alluvial as 1t IS at the mouth Of
the river, but according to those who are
authorities upon such subjects it is OF older
formation, belonging to periods long antece-
dent to the alluvion Of the banks formed by
the present river.
The cost of such a work OF canalization
would be enormous. Besides, we have no
facts to establish that this required work OF
deepening by the current is practicable at any
cost 1t Is known that there are In the bed
masses of gravel In place and thick strata OF
hard clay, but it has not been ascertained
what the nature of the bed Is to the depth to
which it must be ex3avated, nor what thick
ness of moving sands and moving gravels
must be passed through before reaching the
tirmer strata below.
1t Is hoped sufficient has been said to show
that there Is no reason for transferring to
other hands the charge Of the survey of the
river now going on under the Engineer De-
partment for the improvement of low-water
navigation and protection against overflow.
Very respectfully, your obedient servant,
A. A. HUMPHREYS.