Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1880-09-04


cubic feet passing a given point per second. Ii
the first instance we md 20 grains of seci
m nj 20 pass given point mas =ccud at I'll
la%er velocity We found grains of sedimen
passing the same point in the same time
Therefore, at the higher velocity there wert
tive times more in amount of sediment car
RED than az the slower rate, thus showing thu
relation between the velocity of the water
and the amount Of sediment held in suspen
sion. 1t is not proposed TO build regular
dams or put in screens at all points where We
wish to form depositing basins, but in some
places TO put along rows of brush where they
do not grow naturally, and thus arrest tbs
velocity of the water and cause the sediment
to fall. Much of the work of filing by sedi
ment where desired along the Mississippi
was accomplished by simply planting willows
upon the shoals, and thus retarding the cur.
rent and causing the sediment to be deposited
There would probably need to be some
account of the velocity of the cur.
rent. That would be required where
the water is very rapid in its flow.
Q.-After you have thus retained all the
detritus that may be carried in the water,
there viii still be some of the fine sediment
held in Suspension left TO flow down the river.
What general treatment below these cams
Will be necessary?
A.-When we come to the treatment of The
channel with view to its correction, the
two elements of slope of surface and friction
of the bed constitute the most important fac
tors in the problem. 1t is well-estabhshed
TACT chat the ratio of friction to the volume
of water decreases with the increase of vol
une. That is to say, stream with twice
the volume of water flowing in it viii have
very much less FRACTIONAL resistance, in pro-
portion, than one with but single portion,
or half the quantity. If you examine the
present condition of the river in food time.
you ind that Is waters are escaping over the
banks or through the levees in y great many
places. If these waters could all be re-
tanned in one channel, the river would take
2 much lower slope, for the reason that the
same velocity Of current would be produced
with less elevation. or surface slope. The
surface slope is the line which determines
the hight of the levees. It is the food line Of
the river. Evidently anything which will
tend to lower the slope or lower this
food line will make the levees so much
less necessary. 1t must be evident that the
main channel of the river must discharge all
the sediment which the tributaries pour into
it, otherwise it would gradually fill Uphill
its bed up still higher, overflow its banks still
more. Therefore tie velocity of the current
is absolutely necessary to enable the water to
discharge this sediment. Now suppose the
Sacramento river to be capable of discharging
all its food-waters and all this sediment
through one channel without OVERLOOKING its
banl,s-in Hood time being simply banks full,
it is evident that the fall is sufficient to over
come the friction and produce the necessary
velocity. But suppose we should build
wall right through the center Of the channel
and divide the water into two parts. IS it not
plain that we would add that much FRACTIONAL
surface to the water-the two faces Of the
wan, and the river must then have a sleeper
slope to increase the velocity, to balance or
overcome the additional friction. IL you
subdivide the water you increase the friction,
simply because the smaller the stream tie
greater the ratio of friction. The moment
you begin 20 decrease the size Of the
,treatn you increase the friction, and
therefore every drop OF water you
draw of or divert. or allow to leave the main
channel, you decrease the ability Of the
stream to protect itself from further filling
10 and perform the work Of securing cut
-he present deposits. The work of correct
ing the channel should be commenced at the
-ower end OF the river. 1t will not do to
at the top, and entirely let 90 the
matter further down the stream. That was
one of the causes leading to The disastrous
Effects Of the food at S2egedin. The river
above the city had been treated, and It's
carrying capacity increased BY cut-offs and
other improvements, which had not been
provided and carried cut below the city,
and the channel below was unable to
discharge the food waters as fast as they came
Town from the upper portion OF the river
In the case of the Sacramento river the
division of the water at Grand island has in
,reased the friction, and consequently the fall
II slope OF the bed Is greater there than from
sacramento down TO that point, This diyis-
on Of the current there held the water back
.bove that point and made the river fill up
md caused the river-bed to be higher at the
Ipper end of the island than it would be If
he veto 3ity was not retarded.
Q.-Win you give US an idea of what would
De necessary for US to do to overcome the
present condition Of the defects you mention
A-Y ouwant to get this water all into one
;hannel as fast as you can, and you can do it
jTst by Strengthening your levses and the
work could be hasteued by putting on dreg-
ying machines to sid in deepening and cor
-ecting the channel. There is another phase
If this question Of friction which You must
lot forget. The nearer 8 true circle the form
If the bed of the channel, the less viii be the
riction from the water flowing through, and
he deeper the channel the less the friction.
If you hatten out the channel and give
,reater width, you increase the friction. If
ne river has too great width it is necessary
% narrow 1t up by winrowinZ with willows
soross or upon the dry shoals where the river
8 too wide.
Q.-Then to correct the condition of the
liver at Grand Island you would probably
eek to coufne the water IN a single chan
Eel. Which one would you keep open and use
or that purpose?
Ayes; the water Of the river then
hould be brought into one channel as soon
Is chat may be done, and Steamboat slough
3 the best one to keep open. It is, first.
he shortest channel, and, secondly, has les s
lope Upon explanation being made that the
'hauDel Of Old river was much larger than
hat of Steamboat slough, Captain Eads said
hat future examination OF the two channels
night induce hin TO review his judgment as
o which should be closed. That if the
han,el of Old river was very much
ar2er than that Of Steamboat slough, it
night be judicious to keep open the larger
haunel, since the object of closing either
hannel was to Increase the carrying CAPACITY
f the other. 1t might, therefore, be deemed
rest TO keep open the one that possesses the
argest capacity. a more careful examina-
ion Of the matter also led to the conclusion
nat the closing Of the channel Of Steamboat
Tough would facilitate the reclamation Of
he lands lying vest Of the slough and on the
main bank Of the river. MIR. Eads promised
ipon his return to make more thorough ex
OF the condition of the two chan
.els under consideration.
Q,-Whae would be the effect upon the
liver above Grand Island, IN food time, by
his treatment which you propose at that
Ioint would it effect the river at Sacra-
aento?
Al have no doubt that when Steamboat
Tough is once open and the Old river closed
p, the hoad-leyel here at Sacramento
7onld be reduced from Is to 20 inches.
{ you gradually enlarge the carrying ca
acity Of the river by its own force | have no
oubt but you will decrease the food level
ere, in time, from four to fye feet
ct has been suggested by the press OF
an Francisco that the securing out of the
ivera by this process would necessarily shoal
p the bay Of San Francisco, viii this be the
ase?
Al think but small amount of the
ediment which il removed from the channel
1iH be lodged there, for the reason that as
on bring the river to comparative uui-
ormity in width it establishes comparative
Of depth, and there are nov
reat many desp pools and sboal places in the