Abilene weekly reflector. [volume] (Abilene, Kan.) 1888-1935, 1909-04-15

bLHuub IlFcE plMSAVAOD NN
means for applying the current en-
ergy.
Dams.
Since the flood OF 1908 much agi-
tation regarding flood causes and
flood preventions in one way and an
other has been connected with dams
across streams. Here again It seems
to the writer facts are not under
stood.
The influence of dam across a
stream during mild flood certainly
| is in the direction Of causing the
river to break over its banks up
stream from the dam. This influence
however, is not so entirely an unmit-
igated evil, is an ordinary obstruc-
ton in q river channel. A tree or
bridge pier or snag checks the veloc-
ity Of water and in no degree works
recompense for 1t, so that its In
Auence is entirely bad. A dam across
water stream checks the velocity OF
water but in turn necessarily in a
measure compensates for 1t by caus-
ing the water to flow with greater
velocity as 1t passes the dam. OBJ
servations and measurements uni
yersally show that when water be-
gins rising in stream 1t rises faster
below the dam than 1t does above,
SO that when stream becomes suffi-
GENTLY high the presence of the dam
can not be told from the appearance
of the surface of the water.
Let US suppose that we have a dam
five feet high. At low stages OF
water the water level above the dam
will be five feet above the water level
below. AS a food approaches this
difference in level begins diminish
ing-first to four and one-half, then
four feet, then three and one-half
etc. A little thought will show why
this is so. Let us assume that we
have a rise of ten feet above the dam
SO that a volume of water ten feet
in depth will flow over the dam
Now, everyone knows that the watel
at and near the surface flows very
much faster than water near the
bottom of the STRAIN. The farther
the surface is removed, therefore
from the top of the dam as the food
rises the less influence the dam vii
have on this rapidly flowing water
which constitutes the main runof
of the stream. During low stages the
dam, therefore, produces its maxi
mum effect, which effect is gradual!
decreasing in percentage proportion
as the water rises.
In confirmation of the above the
oretical consideration 1t should b.
added that careful investigation O
the Kansas river valley Immediately
after the food Of 1903 failed to re
veal any material difference in dam
ages produced along the river vale!
above and below the dam at Law
renee. l had eight assistants work
ling under me examining the rivel
valley from its mouth westward Z
Junction City. These were younl
men not one Of whom was a either
of Douglas county. One OF tn
charges / gave them was to lool
carefully into this question and de
termine II possible whether or no
the dam at Lawrence produced any
appreciate effect in the volume o.
damage done by the food below thu
dam and above the dam. The unan
Iimous statement was that, so far al
Ithey could determine, by careful
observations, food damages were
lust as great below as above.
In tins of mild floods, however
dams certainly produce bad effects
hey cause the water first to breal
over the river banks above the dam
which in turn is liable to set up new
channels, and to food certain area
which otherwise would not be dis
turbed.
Spill Ways.
1t has been suggested that wher
dams are built spill-ways should b.
provided around an end Of the dan
so that during mild floods an exces
sive amount of water could flow pas
the dam without overlooking tn
banks above. This, under certail
circumstances, would be a move Il
the right direction. Its value woul
be made nil however, provided tn
channel'of the stream below the daT
was not sufficiently wide to carr
away the water as fast as it passe