The Cairo bulletin., 1910-01-30

through. forming a cutoff IS tn,
disturbs the regimen OF the ritter 70
many mile above and below the Gu
OF, il is always pre,ented when tn
funds On hand VIII provide for prol g
hank reyetmenL If not prevented tn
resulting arrangement may extern,
over a total distance OF twenty-five
miles. and it may require twenty Of
twenty I've years before tuis reach be
comes as stable as it was before Ii,
cutoff took place.
The most interesting feature to tAt
student and the most Troublesome t
the navigator are its shifting bars o.
sand and silt These not only move
horizontally. but also r.se and fat
with the stage OF the river and deter
mine the depth of the nayigable chan
mel. They DO not lie in a line at right
angles 10 the bank. but extend
diagonally across the river for q dis
lance amounting TO two or three times
the with of the river, In this way
the deep water in the upper pool eX'
tends down stream past the head OF
the next pool, and the water in pass
/ ire from one pool INTO the next passes
= over this bar in a comparatively thin
sheet of water Deep water is always
found in the bends. The bars are
the natural stream regulators. build
ing out from the convex banks, and
incidentally aiding n the erosion Of
the concaye banks
The channel becomes fairly stable
only after period OF low water AS
the river rises the bars rise. a rise OF
one foot IN the water corresponding to
about 0.j foot rise on the bars, IN
ether words. while a Stage Of four feet
on the st. Louis gauge corresponds to
ia depth OF about SIS feet on the limit
ing bars. rise of ten feet will not
give depth of 1915 feet, but only 90
or - feet on the same bar
Il the river falls slowly, the bars
viii erode al the same time and man
tain fairly good channel When the
river falls rapidly, however, the re,
suit is most disastrous as the bars
are all high aud ii takes consider
able time for the current to cut a
channel through the bars, a process
winch is aided and directed by the
hydraulic dredges now in use.
crescent Project for Improvement.
The project now in force was
adopted in 1881 and is intended 10
secure a minimum depth Of eight feet
1T STANDARD low water. which is A.
feet on the St Louis gauge. To Sc.
cure this depth it has been the plan
to confine the flow Of the river to a
width Of approximately $500 feet Up
to bank-ful stage. In other words.
the permeable pile dykes or hurdles
have Teen driven so That their tops
correspond to a stage of about 25 feet
on the St Louis gauge.
AT first willows were placed hort
zontaly between the two rows of pil.
ing, but it was soon discovered that
each hurdle soon collected enough
dritt wood to answer this purpose. so
mat waiting as it was called. was
discontinued.
Each hurdle, by checking the cur
rent, carses a deposit to take pla-e
on the down stream side, creating
bar which is gradually built up high
enough to sustain a growth OF vii,
lows. The project also provided for
the revetment Of the banks. both new
and old wherever necessary to Sc
cure permanency
a large amount Of successful work
Was done under this project but in
1896 the construction and operstjop
OF hydraulic dredges was inauguratei
on this section, AMI since the latter
date the appropria sons have been
greatly reduced and, by order of con
gress, have been Utilized almost en-.
tirely in dredging. The width of the
dredSed channel has been limited tn
TWO hundred feet, The total amount
which has been appropriated for all
purposes from the Mouth of the Mis-.
souri, River to Cairo is approximate Y
$12,7SlGa.
Complete Regulation.
Illustrated from report OF Assistant
Engineer w. NJ Penniman.J
"A system OF complete regulation
would embrace three forms of pe-ma-
hent construction, as follows:
l. SIde-Contraction. The building
OF new tanfs to the height of the
iahk-tull stage on the projected
alignment and Slope -dus securing
the contraction of the stream ne,e-.
sary to prodrce the required depth
to he accomplished by works of side
contraction Wino.,lanc mormon h,o o