Evening star. [volume] (Washington, D.C.) 1854-1972, 1882-12-22

cred q very interesting lecture last evening be-
lore the Washington branch OF the Naval Insti-
tute, in the old Navy department building. His
subject was the channel Improvement of the
washington navy yard. In the opening he said
that this channel does not, in its present cOndi-
ton, satisfy the requirements of the station.
and SO the yard cannot satisfy the requirements
OF the service
: The channel through which once foated the
Minnesota, and even ships of 81 feet drau%ht, i'm
iront of the yard and for some distance below.
now has mean maximum depth of 20 feet and
minimum depth of Is feet Whatever be the
causes that have produced these results il is in
dispQ.able that they are still active; and unless
some effective means are provided for arrestng
these causes. and for cnlargin.c and preserving
this charmed the few of our vessels of war which
can still reach the yard will be shut out and no
craft larger than
YAwI. OR A FL.ATEOAT
will enter the Eastern branch
The numerous shops and valuable plant accu-
INFLATED at immense cost. and so efficiently EN-
P'oyed in the past in producing the best ma
terials for the Use Of the navy and which might
De, and ought to be. employed in building the
Kew navy. will become useless and well nigh
valueless- At the present time, only by the re-
moval of no less than a million of cubic yards of
silt. could channel dimensions commensurate
with the Immediate needs ana purposes of the
station be attained. That, however. would at
lord but temporary relief for unless some other
means are devised for maintenance this naya-
gable track can only be kept open by cOntinu-
Gus dredging at an annual expenditure of
large sum The difficulty of obtaining yearly
appropriation for that purpose is apparent and
attested 10y the present condition OF the Chan
mel.
The Eastern branch partakes more of the ma
tpre OF long inlet or estuary than of q river
Owing to limited watershed. of about 115
tTf..AIn nh no al
partmeEt has an ordinary flow of only 100 cubic
leet per second. and may be denOminatcd
small creek In the lower portions its volume
nuctuates with and is mainly due to the action
OF the tides.
THE DEPOSITION OF SEDIMENT
Il largely due to the action of the tides and I'M
less the existing physical conditions are modi-
ned with view TO turn to advantage what is
now serious evil. the river will be hopelessly
lost for the purposes of navigation. except
through a judcious and expensive system of
dredging), and as consequence. the tidal por-
ton of the stream will be converted at no dis
tant day into pestileltal swamp a receiving
basin of nauSeous sewer deposits and a nui-
sance of equal proportions and not inferior in
its malarial developments to the one west of the
city now in process of eradication at an euor-
nous expenditure OF public money
Iide-gauge observations ut the navy yard for
= period of over nine months show the mean
range of the tide to be 8 feet. and the mean
duratioii Of the food tide five hours and thirty
fve minutes. while that of the ebb flow is six
hours and forty-nne minutes. Ii is evident
that the water moving out through GIVEN sec
nona area at each ebb tide is equal i'm amount
to that flowing in with the preceding flood plus
the discharge of tie river above the tidal COM
partment during the c5b and flood I'm the
present case the latter amount is but o 006 of
the former; consequently the mean velocity of
The flood current opposite the navy yard must
De greater than that OF the ebb in the propOr-
ton of the duration OF the tidal flow or as I21
1s to loo: and as the securing power of the cur
rent increases as the square of the velocity tht,
amount of sediment transported up stream by
the flood must he greater than that carried doW,
0y the ebb. a fact which may he accepted as a
marked Indication that there is a constant demo-
dtiOn OF material tending to silt up the stream
The amount OF material referred to as being
transported or deposited is dependent on the
quantity of setiineltary matters held i'm mecf,an-
cal suspension by the waters which i'm the present
case are obtained from two distinct but similar
sources. and are due to two causes The sources
are the Potomac river and the Eastern branch.
the waters of which are being constantly inter-
mixed and moved up and down the streams by
the tidal oscillations. The causes are first the
force of the current in those streams due to bot h
the tides and land floods and its power to hold
m suspension and transport earthly matter: and
second. the drainage of the two Watersheds
Unless the present regimen and conditions of
the river are modified. the process of sitting will
continue and water communication with the
yard will be greatly impaired or practically clx
on within limited period.
Mr.. MENOCAI-s PLAN TO SAVE THE CHANNEL
The method proposed by Mr.. Menocal for the
Improvement Of the chancellor its permanent
snlargement-is based on a concentration of the
1oOd-waters in a securing BASIN embracing a
superficial area of 5G2. 165 square feet or 66
per cent of the total tidal portion of the river
and then to discharge the stored waters at a
high velocity during the ebb tide through a
channel where they may flow with the least fric-
o0nal resistance and possess a securing energy
much greater than that of the f1Ood-tide moving
ynrOugn the whole estuary. sufficient. it is be-
Ieyed. 10 scour and carry forward the sedim,.r-
tary matter composing the bed of the river so
forming deep and wide channel. and an eGlii-
hbrium established between the current and the
material. It is proposed that the nayigable
channel shall be confined on its southern margin
by longitudinal dixie or hukhead of sheet
piling. extending from point above the navy
yard to the end of the bend at Buzzards' point
and on the north side by the ward wharyes and
py snort sections OF bikes connecting projecting
points IN the banks
lit is to be regretted" he said .that the pres
ent tortuous channel cannot be rectified by cut
ting off its sharp bends and establishing instead
. more direct passage from the yard to the Po-
tOmac- Such radical change cannot however
be made without serious interference with the
riparian rights of lands abUtting. nor without
interfering very materially with the propagation
Of the flood tide"
THE FLUSHING OR SECURING BASIN
will be bounded by the dixie on the south side
ofthe channel to point opposite the saw-mill
wharf, and from this point by line of gates to
Poplar point At the upper end Of the dixie
above che yard, the channel will be in commu-
nication with the basin so as to permit the flow
of the waters in the main channel at all times
moderate amount of water confined i'm a well
proportional channel will be found quite ample
20 produce a current sufficient in bottom en-
srgy to effect the object in view. A velocity OF
one foot per second will suffice to remove the
Hight material composing the bed Of the stream.
but the current should be as uniform as posi-
BILE, otherwise its effect might prove Injurious
instead Of beneficial.
II Is the object, therefore to leave the basin
a permanently open to the channel both for the
infiuent and effiuent waters; or i'm other words
the channel will be an integral part of, and NAV
be regarded as an extension of, the BASIN By
the flood tide the whole basin of the Eastern
r branch above Poplar point will be filled as now