The New York herald., 1878-03-08
HARBoR BARS.


urai Force without tho Aid OF Jettes, the Eject OF
Which to Reduce the BED Bottom OF tho River and
the Tendency TO Floods" 1t would be hard to sxag.
gorate the importance OF the subject treated for
well known TO all engineers Of every country there 10
no moro serious problem known 10 commerce than
the proper treatment OF harbor bars. No nation with
seaports fails to appreciate this fact aud millions OF
dollars are annually spent In executing the different
projects OF engineers who have made . study OF tho
subject. As example OF this IL Is only necessary
to point to The recently constructed jetues at the
mouth OF the Mississippi River, which the
government has employed Captain Eads 10 build. AZ
10 we'll known the Of this costly experiments 70
anxiously looked for by all commercial nations. and
while It Is claimed by many that this success has al
ready been demonstrated experienced men arc wait.
ing TO see the permanent effect before declaring a.
much.
Mr. Knapp advances what 10 believed TO be an en-.
treiy new theory 10 the formation OF these bars,
and together with this theory propounds simple
remsoy for tho existing difficulty. He proposed IA
explain method BY which harbor bars and shoals
might b. 80 moJ,nsd as 70 prevent htsle. # auy,
obstacles TO tho res and easy entrance Of harbors BY
the larger class o vossels
CLASSIFICATION OF BARS.
Then referring to tho common designation or the
different OF bars delta, DRIFT and waves the
author maintained that treatment Of tho question
shat gives primary importance TO delta or DRIFT bars
Is indirect and irrelevant the real OF lorna.
ton, which claimed Is solely wavc action. He
said:-Ths theory Of deepening channel ny narrow
Ing by jettes has probably been adopted because OF
arsumsn, and belief that tho OF bar formation
IL by reason Of the mouth of tho stream spreading
aud dusng itself where enters the sea- ana IN
consequence this diffusion II s SAID that II loses m
velocity aud drops It's sediment, held Ia Suspension
In accordance with It's velocity ut the mouth, aud
thereby iorms bar. This theory he claimed was =
grand error and bad been Tho means OF causing tho
expenditure oil millions with positive failure ts
results whore II nas been tried ON DELTA
certain whether 1t IL = failure u result. HIS own
theory IL that two contrary forces always exist at
the mouth u river dischargng into tho sea-one 10
cut out ana the other up II either removed
tho other must unimpeded action and river
viii be- closet up or tne osr s, ~ 20
being only an indication or measure bstweon tho two
opposing iorces
WHAT CAUSES BARS.
Tho force that causes bur aud shoal formations,
he continued, Is duo entirely 10 tne peculiar wave
action OF the and when can contr0. this wuvd
action 10 our purpose then affect tneso bars
and shoals ~ we desire and deepen the entrance
VIVA. il may 10 above Inc bar ino author tnsn
gave length his reasons for believing that narrow.
ts results and then explained ut still greater length
the msIh0d IN when particles vi sand and othef
solid matter are drfted by the wavo action. There.
fore, he continued, wave action being the cause VI
bar formation the upheaval Of sand IN the mouth
OF river, It Is only necessary TO check The undulaons
wnat In higher would be called interisrsnce
HOW OVERCOME DIFFICULTY
TO carry theory into practice Tor the prevention
OF the formation OF harbor bars, we'll TO cut
down th0se already formed, whcn do on tue theory
Of obstrucon, said tue speaker otherwise CONSTRUCT
q barrier, directly across the mouth OF river or
nsroor on the outside Of It's bar In depth OF water.
twsny 10 tnirty icet above tho bed 5ottom otnorwsa
apex snail be submerged twenty to thirty iesh
according the depth OF water desired the bar.
As height OF this barrier IS tho only quality
essary produce tho required interierence to wave
action, ths thickuess or wdth need only be measured
by the required solidty necessary 10 Withstand tho
force Intended to detract from the waves,
which soliuy Will PROBABLY bc lar less than would az
nrst appear. This barrier propose build It. Will
not Gner the slightest impeachment 10 the irco dis.
enafx. ., Inc waters .no n.,s Tue ss,, Du. s. oA
charge. Neither will IL offer the least imped-
iment 70 vessels passing 10 aud ou. AZ all times II
would DO that tho sund after building up an incline on
the outside Of the artificial barrier would wash over
II deep wator tho inside. Concerning this
he said lit evIdent thut the whole space between
the bsrricadc tho bar built up level with
tho apex Of tho barricade bcfors the bar will COM
mence TO DO built up again. This will be slower tnan
there will DC long level limo that the
waves must pass over, which viii use up the small
amount Of friction remaining water SO that by
the the force has reached the bar there villa
b. M ,9 @ DO o. los Iane I PSrss
complete the obvious remedy will be u repeat the
original operation and build another artificial
iarther OUT
ADAPTABLE REMEDIES
The remedy he proposes he claims is especially
adapted 10 channel ports whore srong
Iittoral currents and tideways, such as Bouiognet
Disppe and Rotterdam. Placed before canals hl
claims that would be beneficial be-
sand, but canals have NO outward How or current V
erode and carry OUT me sediment the success would
Amsterdam canals he CLAIMS that It would save the
immense that now have to be spent IN dredging.
VI this he says:-At the Amsterdam Canal, having
made o close examination, Gun speak most decidedly
as the benefit DO derived from the application or
shis system, and do not doubt that tho circumstances
aI Port Said will be found very favorable though with
doubt the method applied 10 the New Sus NJ Rot.
tsrdam would give at least live Of than
could be got al tho Amsterdam Canal. 1t was stated
short time In o the prints nat the coast a P0rs
ssid was advancing At the rate o. ai.y yards year.
year BY ycsr, 937, 900 cubic yards having been 70.
moved in 1875 against 16l cubic yarus In 1871
TINS TACT itself should sufficient TO the i.
practtcabity Of building the Fort ST. Philip Canal
the Mississippi River for tho purpose OF securing =
deeper entrance than tho mouth Of the river
oilers. But 10 this, " add tbe experience lately
gained by American engineers OF the unstable bottom
OF that locality, where u twonty pound weight will snk
many feet Il certainly Ioors 70 get iouu-
daon for tho msssve masonry required Tor the ocks
OF such WORK at tina, place. Neither Golfer dam
casson would enable II 10 no built and even
II built n would certainly silt up far more rapidly and
to lar greater extent than any natural ot The
river.
RESULTS OF DEEPENING.
As to the result which would follow the proper
ton OF the height of the bed bottom inside tho river
or harbor-Mr Knapp quoted as follows from Ar.
Thomas Stevens0n:-"Iho Preservation OF the dcptn
Of harbors ut level than that OF the Original
bottom involves bOtn uncertainty and expense. =
When II forms bar outside OF tho entrance the posi-.
bility OF maintaining greater depth permanently be-
comes very doubtful Tho efficacy Of tue scour, 50
long a. II Is mpsded BY enlargement OF the chan,
mel may be kept up Tor great distance, but soou
comes to q end alter II meets the sea-"
As to the height OF the bed bottom inside tho har.
bora the author claims that II pen entirely
on tne height OF bar, and when that Is reduced
the ebb dow Of watcr will soou sweep
away the mud and sand TO dopth approxmating thas
oi the bar. This he claims, will have sanitary
value
Referring TO the favorto "dead angle theory" OF
bar formation, which Is held by many promine ent en-
gineers, who SEQ no way OF overcoming the Diff
Guilty and consequently oppose oil plans OF harbor
provsments ne explained the theory quoted from
Major General Humphreys, U. s. A., aua IRON Mr..
Roocrt Stephenson, wno support II, and said This
~ certainly solid Endorsement Of the theory, and it
would be egottstical, as well absurd not TO givo 10
due consideration M factor OF the trouble. loo 80.
and n, Is s the sole or only part OF the Of bar