Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1891-01-03
Profile of me South Pass Delta Of the Nss~spp Rive.


carrying capacity with equal slopes would
be far greater; and the greater uniformity
OF How would give far more regular and
In every way superior channel.
The maintenance of the river and its
banks would properly be assumed BY the
General Government and the character OF
the necessary dikes or levees and other i'm
provements would be vastly improved.
rendering secure from overflow the present
and prospective Inhabitants of the reclaimed
lands and ensuring the safety and perma-
nence of their investments.
The proposed Improvements at the outlet,
in the upper reaches of the river, and in the
tributaries all come under general law to
wit: the law of controlled velocities. The
proposed changes may be generally stated as
follows: where less than normal, the velocity
should be eaugmented where above normal, the
velocity should be diminished Where the
river admits of permanent works, i.e at the
outlet, the works should of course be perma-
nent; when the discharge conditions vary
between extreme limits permanent works can
affect the velocity at one stage only and are
worse than useless at all other stages; there
fore the works in such places must be NOV.
able so that they can be adapted to varying
stages of the river and control the velocity
at all times that such action may be desir-
able.
A river flowing between banks of proper
contour, with suitable cross sections, will
have suitable regimen; its constructive
and destructive actions will balance, and
the banks and channel will be permanent.
If in such river bar or shoal be formed
at any point, the current above the shoal is
retarded, the constructive action is aug
mehted, and the shoal will grow from year to
year; while below the shoal the current will
be accelerated, the destructive action is aug
mented, the banks and bed will be washed
out, and all the conditions will favor the
growth of a second shoaI below the swift
current caused by the first shoal. If now the
velocity be sufficiently augmented by art
over the crest of the first -shoal, the said
shoal will be washed out, the banks and
bed below its site will cease to be destroyed,
the normal velocity will be restored, the
constructive and destructive actions will
again be in equilibrium, and the river will
neither build shoals in its channel nor wash
out its banks.
If in a river which it is desired to i'm
prove the discharge be uniform or vary
within moderate limits, permanent con-
traction works, changing the cross section to
a form offering less friction will be success
ful, because such permanent works will at
all times control the velocity of the current,
and so come under the general law above
stated. If in such q river the discharge
vary in extreme limits. permanent contrac-
tion works are not applicable, and works
must be designed adaptable to varying dis
charge conditions; or dredging must be re-
sorted to. 1t is evident that the commonly
received statement of the jetty principle, to-
wit: "a method of controlled dimensions"
can apply to successful works only when
they fall under the first stated law of con-
trolled yelocities. By the operation of this
law it is proposed to improve the non-tidal
portions of the Mississippi, and its tribu-
taries. By converging the current upon
the shoals and bars and washing a deep
channel through them, continuing the ac-
ton from year to year, the bed of the river
can be finally secured down to the desired
slope and depth, the banks can be estab-
lished with the grades necessary for safety,
and the country rendered we'll drained and
safe from overfows and washouts.
Intelligent supervision will easily. main
tain what has been created; and at the first
sign of trouble the evil will be attacked In
its seat--the shoals at the heads of the bends
The first step in this Improvement should
be the rectiication of the channel by cut
offs, which would improve the carrying
capacity of the river, shorten sailing dis
tances and reduce the first cost and main
tenance. Ten or more cut-offs are desirable.
and five should be made by man in the best