The Mobile River and Its Branches; Commerce of Mobile [pp. 745-748]

THE MOBILE RIVER AND ITS BRANCHES.
consideration, for, if private or individual interest is permitted
to interfere with the improvement of the river by maintaining
and keeping open those outlets, the port of Mobile will, in the
course of time, be ruined; because no river can continue to
maintain the same depth of channel, if deprived of its ancient
and legitimate supply of upland water.
The branch or outlet east of Pinto island, inasmuch as it
draws off from the main channel a considerable portion of its
water, must diminish the power and velocity of the portion
that remains; because an abatement of quantity is proportionally an abatement of force. The scouring power of a river
depends on the quantity of water flowing through it and the
slope of its surface, If, therefore, the quantity of water in the
main channel will be greater after closing up the outlet east
of Pinto island than before, the effect will be an increase in the
scouring action of the water in that channel. If that outlet
and that of Spanish river are both closed, the quantity of
water acting on the bed of the main channel and also the force
with which every proportional part does act will be increased,
the necessary consequence of which must be a deepening of
the channel.
In some countries large reservoirs are used with success for
keeping harbors open and clear, the effect being produced by
an increase in the scouring action on the bottom by the increased quantity of water introduced. Turning the water now
discharged through the several outlets into the main channel
of the Mobile river would have precisely the same effect, and
it would be gross injustice to the commerce of the city of
Mobile, and the general interests of the state of Alabama, that
the outlet east of Pinto island and that called Spanish river
should be suffered to remain, when the immense importance
of having a large commercial depot with a safe navigable harbor is taken into consideration.
The channel east of Pinto island was partially stopped up
in the summer of 1854 by three rows of piles driven across the
outlet, with brush-wood laid between them and covered with
ballast stone and brick bats, a passage way about 116 feet
wide between the piles was left for vessels of light burden.
The partial closing of the outlet was attended by an increase
of depth in the passage left open, resulting from the increased
scouring power of the current caused by the increased head
arising from the rest of the pass being closed and the vent diminished. Any further increase of depth, however, has been
prevented by covering the bottom with material too heavy for
the current to wash out, while the precaution of shoeing the
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