The record-union., 1895-04-15
HYDRAULIC MINING AND NAT
URAL EROSION.

URAL EROSION.
The river channels and the bays and
harbors into which they discharge their
waters receive in all settled countries
large quantity of detritus due to natural
erosion. This is permanently true of a
mountainous country like California.
The breaking of the natural sod on the
Hide hills and steep precipices of the
Sierra Nevadas and Coast Range by
sheep, whose paths make an escarpment
up the slopes they travel, and which
paths become cutters for the water, start
ing the erosion, places the earth on our
mountain and foothill sides at the mercy
of the heavy rains.
Sixty miles east of the city of Sacra-
mento the American River has its source
at an altitude of 5000 feet. The torrential
character of the stream may be inferred
from this fact Even the plains, by the
breaking of the sod and the stirring of
the soil, lose annually part of the NOV
able earth, and what they lose is carried
into the bay system by streams. These
facts have been used in the defense of hy-
draulic mining. The denudation of the
forests of California by cutting on the
side of the hills and the attempted culti-
vation of the slopes, where by reason Of
the stirring of the soil it washes into the
canyons below,-these things are of them
selves a menace to the perpetuity of the
navigability of the rivers and bays of CAL
ifornia
terial. It is only the soils which have
absorbed plant food which are carried
off by natural erosion. This light ma
terial is deposited on the margins of the
tidal reservoirs of our bay system
Nature has provided a means of taking
care OF the results OF natural erosion.
1t is true that eventually this natural
process will greatly diminish the tidal
reservoirs OF the bay system which con-
Etitute the outlet of the rivers of Califor-
MIA. 1t is true that the navigability OF
the rivers will be menaced by this natu-
raj process. It is true that the valleys
receive annually an imposition of soil
washed from the hills and are constantly
raised up by that process; but these
natural processes are slow and prepara-
tions to meet them can be made effect
lively.
This natural process of moving the
superficial earth into the channels of the
the bay system at the mouth of these
streams does not need reinforcement
The fact that natural erosion is inevitable
ia the strongest possible argument agains
its reinforcement by artificial process
But the most cogent consid Grafton agains
hydraulic mining Is that it moves coars
material which by successive stage:
from floods is moved into the channels o
the streams below the sleeper grades o
the foothills. The currents which com
down the channels of the rivers unit
they strike the level of the plains pos
sessss a highly torrential character
This velocity is Stacked by the ney
gradient, and the result is that all tn
matter held in suspension by the curren
in excess of that which the velocity vii
move is deposited in the channels of tn
streams after they debouch from the foot
hill. At low water they remain in th
channels, but the securing capacity Q
flood condition moves them still farthe
down.
Tho mining detritus now being de
posted in the upper courses of th
streams will not reach the valleys fo
some two or three years. 1t will requir
three or four years to move them int
Suisun Bay. as soon as they strike th
slack waters of the bay they cease to
moved, because the material itself
course and heavy. It is not the result
natural erosion. 1t cannot be held i
suspension by tidal currents and d.
posted evenly over the margins of th
great bays of San Francisco and Sa
Pablo. 1t is process of building up rive
channels which will eventually extend tt
channel of the San Joaquin and Sacri
rnent Rivers to the Straits of Carquine
making the western outlet of the strai
the mouth of these two rivers. AS is Il
case with the mouths of all rivers empty
ing into bays or oceans, bar will