The southern press. [volume] (Washington [D.C.]) 1850-1852, 1850-07-26
I the mouth Of the Ohio, and yet is two hundred

at the mouth of the Ohio, and yet is two hundred
feet deep from Fort Jackson to New Orleans.
AT the Balize the current is arrested by the waters
of the Gulf, and the velocity is not sufficient to
lift the fine particles Of clay deposited in the bed
At the mouth Of the Ohio, and above the velocity,
is such that it sweeps along coarse sand which is
deposited before it reaches New Orleans, where
the current, although the velocity is not sufficient
to take along coarse sand, has power to lift and
carry forward the fine impalpable particles Of
clay which constitute the whole bed of the river
at and below that city. s Re0
These principles being established, it follows
that if we straighten the river, the velocity will
be so much increased that the current must bring
down great bodies of coarse sand, which will be
deposited in the channel, which in the first place
would be cut down much below what it now is,
and then filled up by the large deposite of heavy
sand brought from above,--the effect would be
to divert the channel into the softer material, on
one or the other side Of the river, which, in obe-
dience to the laws which govern its course, would
cut for itself meandering bed. 1t is therefore
impossible to confine the river within straight
channel and lift were possible, the current would
be so rapid rs to prevent its navigation, until ii
brings down so large deposite of coarse sand
as to elevate the bed, so as to give the channel
mcandering course. The same results would in
a corresponding degree be produced by opening
one or more outlets into the Lake above New
Orleans. The volume of water which is now
discharged into the Gulf through channel of
one hundred and sixty miles in length would in
that ease be discharged into the Lake, on the
same level with the Gulf through channel of
five miles in length, and there would necessarily
be a corresponding increased velocity. This
,,a,,, obopnol xunuld ha u,ada fhrouo, fba dano
sites of fine clay, similar in all respects to the fine
clay which constitutes the bed of the river at
and below New Orleans; and it requires no argu-
ment to show that if the current with its present
velocity has dug channel two hundred feet deep
at New Orleans, the power of the current in the
new channel would be such as to turn the whole
river into Lake Ponchertrain. In that case the
present bed of the river below the outlet would
soon become Lake, and the communication be-
tween New Orleans and the Mississippi river and
the sea, be cut off by the filling up of both ends
of that great Lake.
So much as to the effect to be produced on
the city of New Orleans by a new outlet 1t
remains for us to sec what effect this new outlet
would have on the channel, As the land rises
above the waters of the gulf, it produces first,
grass, then growth of cane and willows. As
we proceed up the river, we find cane and larger
trees and under brush, with, in many places,
thick growth of PUSHES The grass rushes,
canes and under growth lining the shores of the
river act as flterers and by arresting the flow of
the current, cause whatever is held in suspension
to be deposited at or near the banks Of the river.
At the mouth, the deposit is fine clay, further up
it is coarse sand. This deposit thus made, has
raised the banks Of the river, while that which
lies back from it, remains as it was first formed,
slightly increased by the depostes of the light
particles borne by the overhowing water through
the vegetable filterers on or near the banks.
We have seen that Il velocity of eight inches
per second will lift coarse sand,-we know that
as the current acting under like circumstances
produces the like effect, the time must have been
when the bed Of the river at New Madrid must
have been as deep as it now is at New Orleans.
Yet, it is not now in low water more than an
average of ten feet Mt and above New Madrid,
while it is near or quite two hundred feet deep,
at and below New Orleans,--and we now see
why this is so: the strong current from above
has wrought down so much coarse sand as to fill
up the deep bed Of the river, once as deep at
New Madrid as it now is ut New Orleans, by fill
ling up the channel with sand so coarse as to re-
sist its further action. Each successive overflow
has carried the coarser sands and lighter clays
into the back lands, until they too have been ele-
waited in a corresponding degree. 1t follows
that if we open an outlet into the lake, and thus
produce a corresponding increased velocity in
the current above, the river will dig out its bed,
and bring down large deposites of coarse sand,
filing up the lake first, and then the bed Of the
river until it will have established for itself pre-
cisely the same regimen that it now has, when it
will overflow its banks precisely as itnow does.
1t follows that opening new outlet is tempo
rary expedient, which, by increasing the velocity
of the current, will bring down the coarse sand
much more rapidly, and thus fill up the bed of
the river with Il permanent material, when the
overflow will be as great as it now is-nnless the
current, driven by the resistance of this heavy
sand deposited in the channel shall cut for itself
new beds in the lighter clay. In that case, the
river will resume a meandering course, and no
one can tell where it may GO a n
Ii remains for us to see what the effect of en-
bankments will be, and here the fact cited by Pro-
lessor Robinson, that the addition of two streams
of nearly equal volume Gone in 1000 and the
other in l720) instead of filing up the bed or
causing it to overflow its banks, has deepened
the channel of the Pc, and drained several large
marshes which had been for ages under water, |
seems to be conclusive. But matter of so
much Importance, effecting the interests of so
many individuals, should be carefully examined
in all its bearings.
We have seen that Professor Robinson's
Theory of Rivers "rests upon few fixed, known
laws-we know that the overflow depends upon
the capacity of the channel--we have seen that
the channel at New Madrid, which was once two
hundred, is now but ten feet deep, in low water
and we now know that this channel has been re-
ducedto ten feet, by heavy sand brought from
above by an increased velocity of the current, and
it requires no argument to show that as the chan
mel of the River from the mouth Of the Ohio to
the Balize, is one inclined plane, and the velocity
of the current depends upon the declivity-that
velocity must increased if we diminish the length
of the-and that there will be corresponding
diminished velocity if we increase the length of
the plane. To open an outlet above New Or
leans would diminish the length of the plane,
and by increasing the velocity, bring down the
heavy sand now deposited in the upper part of
the river; whereas, by elevating the banks and
confirming the whole volume of water within the
same channel, we would increase the length of
the plane, and at the same time enable the cur
rent to cut out for itselfa deeper channel, and by
arrestiug the velocity of the current above cause