Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1881-02-03
HYDRAULICS.

1t is to be regretted that many persons
who undertake to discuss the present
food visitation should have failed to ac-
quaint themselves in the first place with
the laws which govern the phenomena.
Captain Eads, in his report on the Sacra
mento, observed truthfully, san inteili-
gent Judgment cannot be formed as to
''the proper means of relief, without some
general knowledge of the natural laws
" controlling the waters of all sediment
bearing rivers Z and he proceeds to in
dictate what these laws are, and how they
operate. As this report is accessible to
all, and as it embodies the most valuable
and authoritative statements extant on this
subject, it might have been thought that
journalists, at least, would have taken the
trouble to master the principles laid down
IN it before proceeding to dogmatize on
the question. 1t is, however, evident
that this trouble has not been taken by
those of our contemporaries who have ex.
pressed their opinions on the present situ-
alton, and fair example of the self
sufficient ignorance which obtains in this
connection is offered by the San Francisco
Chronicle of yesterday. The writer of the
article referred to challenges criticism by
observing that he has made long and
81 careful study of the subject, aud then
proceeds to demonstrate what his long and
careful study is worth by gravely deliver
ing the opinion that either the levees on
% both sides (of the Sacramento) must be
raised five or six feet higher than they
'now are, or that The carrying capacity Of
"he yicer must be increased by setting
''hem back, so as to ,riden its channel to
"dou5le its present ,cidth." Now, the
proposition italicized by US proves con-
clusiveIy that the critic does not under
stand the primary laws which control the
action of sediment-bearing rivers, and that
his ''long and careful study has been
thrown away by failure to learn the true
character of the phenomena he has OBJ
served.
1t is a law Of nature which applies to
the flow of rivers as to all else, that the
work done cannot exceed the force ex-
pended. Whatever opposes resistance to
the force which moves water diminishes
that motion. Sediment bearing streams
have to overcome the friction of their
beds and of the sediment which they hold
in suspension. If the friction of their beds
checks their velocity, they at once seek to
recover it by depositing part of the sedi-
ment which they hold in solution. The
result of this deposit is to raise the beds,
thereby increasing the surface slope, or as
it is commonly called, the fall per mile. :"
The most important element of resistance
is the friction of the channels through
which the water moves. II this friction is
reduced the discharge of the floods is facil-
itated The form of channel which offers
the lenst resistance is semi.cy cylindrical,
" and, says Captain Eads, in proportion
8" as the channel departs from this form,
"widens and becomes fiatter, this resist
90 ance increases, and the surface slope has
Z" to be steepened to produce the same ve-
locity of current. This steepening of the
slope is the direct cause of the over
" flows" Friction is increased not only
by widening and fattening the channels,
but by their subdivision. Captain Eads
illustrates this by reference to Steamboat
lougl and Butte slough, and he continues:
With such evidences of the increase OF
slope which Immediately follows The
widening of the surface over which
the floods pass, or the subdivision
of the main channel into smaller ones, if
seems astonishing than anyone can Sc
riously propose to give permanent pro-
" lection against overfows by multiplying
I" the channels through which the floods
now struggle to reach the sea. Men who
advocate such measures of relief have
"yet to learn two or three of the greatest
but simplest laws controlling the motions
&c of matter throughout every part of the
universe. They have got to learn first,
90 that no atom of water or sand in the
rivers, or planet in space, can have mo-
I" ton except through the influence Of
&c force second. that matter in motion
must encounter the resistance of some
:" other force or forces and, third, that
| 4ba ,aIoc:y,, Of W, 4+ar f1a1ards uDo1s ~, q
+" force carrying it onward, and the amount
4" of resistance retarding its progress Eric
" ton being the chief element of resistance,
" and this being greater and greater in pro-
"portion as the water is subdivided, the
advocates of drainage canals and other
outlets propose to increase the velocity
of discharge by increasing the friction
(which retards the velocity or, in other
words, they propose to reverse the laws
"of nature" The application of these
principles to the present situation is clear
and plain. 1t is proposed to increase the
velocity of the current at Sacramento by
increasing the friction of the channel
That is the Chronicles suggestion, and it is
grave proposal to 'reverse the laws Of
nature, as Captain Eads says.
The idea of protecting town from over.
flow by increasing the FRACTIONAL resistance
of the river which flows by it is unscientifc
enough, but not more so than the widely
prevalent belief that rivers are relieved by
opening artificial or natural outlets in theil
banks dallowing part oftheirwaterst to flow
off. Whoever has followed the preceding
argument realizes that the velocity OF the
current depends on the force which impels
it, and must see that since the volume Of
river is one of the elements of this force
whatever diminishes its volume must at
the same time lessen its force. When a
break occurs part of the force goes out
at it, and as the ratio of FRACTIONAL resist.
ance must increase in proportion to what
remains, it is evident that diminution Of
velocity must follow. This diminution Of
velocity instantly produces deposition Of
sediment by the river. The well-knowr
fact that bar always forms below break
illustrates this process. The tendency