No further appropriations having been made
for carrying, on this work, the small balance left over has been expended
during the last fiscal year in caring for the snag-boat and property belonging
to this work, and in preparing the map and report herewith submitted.
As stated in my last annual report, a small
surveying party was detailed to accompany the snag-boat Thomas Trunnel on her snagging trip in this river, to bring back
some definite information relative to the stream, and, if possible, to prepare
a plan for its permanent improvement. It was expected that the progress of the
boat would be slow enough to allow of a continuous survey of the stream being
made, but the unusual amount of high water and the severity of the winter made
her operations so rapid and irregular as to preclude the possibility of
accomplishing this object. It was also impossible to make the examination at
low water, which is necessarily of the greatest importance in so small a
stream. A map of the river, derived partly from instrumental surveys and partly
from pilot-house sketches, was constructed, and a tracing there of is submitted
herewith.
From the information brought back by the
party, it appears that the alluvial portion of White River ends about 20 miles
above Jacksonport, which town is situated at the mouth of Black River. From
this point up, the stream rapidly assumes the characteristics of a mountain torrent,
the slope increasing rapidly and the valley becoming narrower. This latter is
skirted by high bluffs, which, in some places above Batesville, are not more
than half a mile apart. The numerous shoals are composed of gravel and coarse
sand in the lower portions of the stream, while loose bowlders and rock in
place form the principal obstructions above Batesville. Two miles below the
latter place high-water mark reaches the top of the bank for the last time;
above there the banks are 10 or 11 feet above this level. Floods are sudden and
violent, and the high-water current is very strong, enabling the stream to move
heavy gravel with facility. The low-water discharge is very small, and the current
is too feeble to cut a channel through the gravel bars, which therefore remain
as permanent dams, the current in the intermediate pools being sluggish. At
some of these shoals, more especially those which contain rock, the great
velocity of the current at low water is more of an obstacle than the actual
lack of depth, some of them being, from this cause, almost impassable for the
small class of boats used in the navigation of the stream. In the space of 130
miles from Jacksonport to the head of Buffalo Shoals, 63 shoals are reported,
the minimum depth being 6 inches, and the minimum width of channel 50 feet.
Between Jacksonport and Batesville, 39 miles, 19 shoals are reported, only 2 of
which, however, approach the minimum dimensions stated above. As will be seen
from the map, they become very numerous as Buffalo City is approached, and the
slope becomes very heavy, upwards of5 and 6 feet to the mile, the bottom being
generally of rock. Buffalo Shoal is the worst, and is a very formidable
obstruction. It must be improved before the upper portion of the river will be
accessible at low stages. The low-water depth is only 6 inches, the bottom
being of rock, covered with loose bowlders, and the shoal is a little over a
mile in length. The very small volume of water available, and the serious
nature of the obstacles to be encountered, renders it imperatively necessary
that a careful continuous low-water survey should be made before plans or
estimates can be prepared with any confidence. It is especially necessary that
a continuous line of levels should be run, to enable a low-water profile of the
stream to be constructed. An estimate for this survey is submitted herewith.
It is plainly evident that the plan of
concentrating the discharge of the stream by spur or longitudinal dikes, with a
view to scouring a low-water channel through the flood-deposits, is entirely impracticable
here. The gravel is brought down by the floods in more than sufficient quantity
to fill up annually any artificial channels made, and I do not think that the
concentrated low-water discharge would be sufficient to scour through one of
these bars, even if it could act for several seasons without further accretions
to the deposit. Moreover, the rock could not be moved by this process, and the
general effect would probably only be to increase the velocity of the current
already objectionably great, with little or no increase of navigable depth. It
therefore seems to me that the only method available is to leave the bars
alone, and to seek merely for an increase of depth over them by diminishing the
local slope.
The profile of the low-water surface of this
river will undoubtedly show a series of nearly level reaches, separated by
short and abrupt descents over the shoals. The average slope is probably not
excessive, and, if, maintained throughout, would give a good and deep channel;
but there are many objections to seeking this result by cutting down the crest
of the bars, even if the plan were otherwise feasible. These shoals form natural
dams behind which the water is stored up during low water, and if they did not
exist the stream would probably run dry at its lowest stages. The only plan practicable
is, therefore, to flood the shoals at low stages to a navigable depth and
width.
Of the various methods of accomplishing this
object, the most obvious one is to create slack-water navigation by locks and
dams, but this system, in addition to its costliness, has the disadvantage of
rendering the stream impassable for boats which are too large for the locks,
until the water rises sufficiently to let them go over the dams, or, roughly
speaking, the river must rise more than is necessary for free navigation by
about the height of the dams. In addition to this, the gravel brought down at
high-water would eventually All up or seriously shoal the pools above the dams,
rendering frequent dredging necessary to keep up the proper depth. I have not
the necessary data for submitting an estimate of the cost of improvement by
this method, but it would necessarily be great.
Another method which would effect the same
result is that of locks and movable dams, a system which has found much favor
among French engineers, and has been recommended for several of our own
streams. This system provides locks as in the ordinary slack-water navigation,
but the dam, instead of being a permanent obstruction to the stream, can be
removed in part to allow the passage of large boats, or can be entirely removed
to permit the free discharge of the river in floods. Many of the objections to the
first method are therefore removed in this one, but its costliness and the
expense of operating it renders it unsuitable for any stream, the value of
whose commerce is not considerable.
The only method which seems feasible here is
to break up the local slopes and distribute them over such distances as will
reduce them to reasonable limits. This can generally be done by curving and
thereby increasing the length of the channel, low dikes being run out
alternately from each bank so as to concentrate the water pouring over the
crest of the bar and hold it up until the requisite level is reached. These
dikes will not increase the velocity of the current but rather diminish it, and
as the flood will soon deposit gravel above and below them, it is believed that
the curved channel-way thus set up will be reasonably permanent and reliable.
Of course, in time it will be necessary to raise the dikes and perhaps to
extend them, but at any rate the system will not simply result in transferring
the bar from the head to the foot of the system of dikes, as almost invariably
results when spur-dikes, designed simply to increase the scouring action of the
current, are used. For want of definite information the estimate submitted, herewith
is necessarily only a rough approximation, but I think it is at least large
enough, and a carefully-matured plan based on a proper survey would very
probably reduce it. We were unable to obtain the extreme low-water discharge of
White River, but from such observations as we have, I infer that it is
approximately 1,000 cubic feet per second at Jacksonport, above Black River.
This should enable us to maintain a channel having 75 feet available width and
2½ feet in depth, provided the velocity be reduced to 3 miles an hour, or 4.4
feet per second. The proper slope to give this velocity will vary according to
the nature of the bottom, and the amount of curvature of the channel-way; it
must be determined experimentally, but it will, I think, be found to
approximate 18 inches to the mile.
Above Batesville, our information concerning
the discharge is too meager to be depended on, but I apprehend that it would
hardly be safe to count on more than 18 inches depth of channel-way with a
width of 60 feet from the head of Buffalo Shoals to Sylamore, the velocity
being increased to 4 miles per hour. From Sylamore to Batesville we can
probably obtain a channel 2 feet deep and 60 feet wide, with the same velocity
of 4 miles per hour. These minimum depths, it must be remembered, will be at
extreme low water only and for probably only a few weeks in each year.
Below Batesville the dikes should be built
of brush and stone, anchored with piles. All the material would have to be
moved some distance, and the depth of water in which some of the dikes would be
located is considerable. Above Batesville, rock would generally be alone
needed, and could in most cases be procured on the spot; the depth of water,
too, would be less.
I have, therefore, assumed that a linear foot
of dike below Batesville would cost $8, while above that place the cost would
be $5.50.
The following list gives the various places
where work will probably be needed, together with the number of linear feet of
dike deemed necessary at each place, and the estimated cost of the same: From
Jacksonport to Batesville.
From this it will be seen that the cost of
improving the river from Jacksonport to Batesville is estimated at $218,800;
from Batesville to Buffalo City, $282,837.50, and for Buffalo Shoals, $20,350.
Adding 25 per cent, to these sums to cover engineering contingencies, they
become respectively $273,500, $353,546.87, and $25,437.50. To this must be
added the cost of necessary surveys, which will be $2,925 from Jacksonport to
Batesville, and $6,825 from Batesville to head of Buffalo Shoals, or $9,750 for
the whole distance.
There will, moreover, be needed at least
twelve months7 labor of a snag-boat in removing snags and other obstructions,
which, at $3,500 per month, would amount to $42,000, and, allowing $6,000for
necessary repairs, $48,000.
The total cost of improvement would,
therefore, be as follows:
RECAPITULATION.
From
Jacksonport to Batesville............................................$273,500.00
From
Batesville to Buffalo City..............................................353,546.87
For
Buffalo Shoals ....................................................................25,437.50
From
Jacksonport to Batesville, (for surveys)………………...$2,925.00
From
Batesville to head of Buffalo Shoals, (for surveys)………6,825.00
9,750.00
For
twelve months’ work of snag-boat, &c .....................................48,000.00
Total....................................................................710,234.37
As regards the necessity for this
improvement, it may be said that the country bordering on this portion of White
River is almost entirely dependent on water transportation, which, from the
difficult character of the navigation, is very uncertain and costly. If the
facilities for transportation and communication were increased, there would no
doubt be a considerable emigration to this country, which embraces much
valuable cotton and mineral lands. This is especially true of, the section from
Jacksonport to Batesville, to which it would probably be advisable to confine
the improvement at first.
The amount of the estimate for surveys and
snag-boat work, viz, $57,750, could profitably be expended during the first
season.
Money statement.
Amount
available July 1, 1875………………………………………………… $7,771.26
Amount
expended during fiscal year ending June 30, 1876..................................7,771.
26
Amount
appropriated by act approved August 14, 1876 .....................................10,000.00
Amount
(estimated) required for completion of existing project………………710,234.37
Amount
that can be profitably expended in fiscal year ending June 30, 1878…..57,700.00
References:
1876 Chief’s Annual Report of the Chief of Engineers to the
Secretary of War for the Year 1876: Appendixes to the Report of the
Chief of Engineers. Page 622
– 62.
Government Printing Office, Washington D.C. https://usace.contentdm.oclc.org/digital/collection/p16021coll6/id/1824/rec/15.
No comments:
Post a Comment