The record-union., 1896-03-26

vember %, 1895. A survey, including
Steamboat Slough, was in progress at
that time, and has since been COM
pleted, and the recommendations made
herein are partly based upon the re-
suits of this survey.
A description of Steamboat Slough is
included in Lieutenant Deakyne's re-
port, forwarded by Major Heuer on No
vember %, 1895. 1t ferns the west
channel of the Sacramento River
around Grand Island. The other
branch, known as Old River, is eighteen
miles in length. Steamboat Slough is
twelve miles in length The upper por-
ton of the slough is narrow and deep.
with high banks. The lower portion is
broad and shallow, with low banks 1t
was formerly the navigable channel of
the river, but was abandoned about
twenty years ago on account of shoal-
ing, Old River since that time being the
main channel. Just below the junction
of Old River and Steamboat Slough is
the mouth of Cache Slough, which is the
outlet of what is known as the Yolo
Basin, the. great west side depression of
this portion of the Sacramento Valley
This slough discharges at flood stages
enormous quantities Of water previ-
ously poured into Yolo Basin by the
overflow from the Sacramento River
above Sacramento and by the drainage
from the Coast Range on the west.
| The survey recently completed shows
that a navigable channel commensurate
in size with the balance of the river
can be created by dredging at a cost Of
about $4,000. 1t involves the removal
of about 100000 cubic yards of ma
terial making a channel nowhere less
than eight feet deep and $50 feet wide.
| An Improvement 10 a similar depth in
CID River under present conditions can
| be made by spur dikes, similar to others
already used in the river, at a cost of
about $45, 900. The imp ovement in Old
River, however, would probably be per-
manent; that in Steamboat Slough
might be only temporary AS far as can
be seen, the same forces and conditions
which caused Steamboat Slough to
shoal are still in existence, and the
| deepening of the channel by dredging
could only result in temporary benefit,
since present conditions would doubt
less soon be restored. Present indica-
tionS, however, are that the channel is
to a certain extent securing out. This
result is probably due to the fact that
i'll the last three or four years the lower
end of the slough has been leveed, and it
| is possible that the Improvement may
continue until it fills present require
mentS of navigation. In any event in
q stream carrying so much silt as the
Sacramento River, ultimate conditions
will depend upon causes modifying the
flow of water, and Will rot be much in
ftuenced by the dredging of deposited
material
An improvement of the lower end of
the slough might be made with spur
dikes, if the requirements of naviga-
ton demanded it. A fair estimate of
these requirements is shown by the
amount of traffic that now seeks the
slough at the medium and high stages
of water, when the conditions are about
as favorable as they would be at low
water were this slough improved. AT
present the through passenger boats
carrying the mails never go through
Steamboat Slough at ALL fruit and pro-
duce- carrying boats navigate Old River
habitually, but occasionally go down
the upper half of Steamboat Slough and
return; towboars occasionally use the
slough on the up trip, and on one occa-
sion have used it on the down trip
when without barges. 1t therefore ap-
pears that the present requirements of
navigation are slight, and in view of
| the uncertainty of the permanence of
the Improvement, consider that as far
as navigation is concerned Steamboat
Slough is unworthy Of improvement by
the United States.
| AS to the increase of capacity for flood
discharge, it may be said that the en-
largement of this slough is intimately
connected with, and q most important
factor of, the entire drainage system of
! the Sacramento Valley, a subject I'M
doubtedly of great Importance but one
which has not heretofore been consid-
cred by the Government in connection
with river and harbor improvements
| The fall at low water from the head of
Grand Island to the foot is % feet, and
on account of the shortening of the dis
| tance the discharge capacity of the
| river would doubtless be greatly aug
mented if Steamboat Slough were the
main or only channel of discharge. At
present the average cross section Of
| this slough at high water, assuming the
slough to be bank full to the top of the
| levees, is about II 900 square feet; the
| increase in cross section caused by the
dredging necessary for navigation pur-
poses is less than 200 square feet, so
that the increase in discharge capacity
incidental to Improvement for naviga-
ton is trivial and may be neglected.
If Steamboat Slough were widened
and deepened and it's upper end given
form to facilitate the entrance of water,
it is by no means certain that it would
become the main channel of the river.
1t is a we'll authenticated fact that fire.
quently at flood stages the water rushes
out of Cache Slough at higher stage
than water in either Steamboat Slough
or Old River, practically acting as a
dam to the free flow of these waters,
and forcing a considerable portion of
the discharge of the Sacramento River
across low swamp lands toward the San
Joaquin. 1t is probably this directing
influence that has caused the improve
ment of the upper part of Old River and
the shoaling of Steamboat Slough, and
with YoIo Basin and Cache Slough in
their present condition, the same result
would probably occur again. 1t will
thus be seen that the control of the
waters flowing into Yolo Basin must
be considered in connection with the
improvement of Steamboat Slough for
drainage purposes, and this brings in
the entire problem of drainage of the
Sacramento Valley, complicated as it
| is by the very slight grade of the valley
land the flow of detritus from hydraulic
4 p7i,,ipo apd from ma af11ra1 erosion in tha