The Washington times. [volume] (Washington [D.C.]) 1902-1939, 1924-03-07
By e. B. C'FARMERY DUNN.

By e. b. C'FARMER'O DUNN.
~ Copyright, 1924, by Cosmopolitan
| News Service.j
EAST ORANGE, N. j., March I.
The danger from floods in our
great rivers is passing.
It has been several years since
any serious flood has occurred.
Statistics prove beyond ques-
ton of a doubt that, owing to the
changed condition Of the climate,
the modern building Of embank-
ments and the extension Of the
levee system, the danger Of floods
is becoming less and less.
The Mississippi today is confined
to its channel by massive embank-
| ments, which in some places are
reinforced by a second or emer-
gency embankment, the latter
forms an excellent protection in
case Of break or small crevice.
Held In Check.
The water is then held in check
and seldom finds its way through
the second embankment. These
levees extend from the mouth of
the Mississippi to Carlo: the rivers
above the latter point seldom over
flow their banks.
The upper Mississippi and Mis-
souri, occasionally have ice gorges,
which impound the water, and
occur over a limited section of
the country.
The greatest inconvenience in the
- he
is drought, instead Of flood. There
Ohio and its tributaries, but the
long continuous warm weather of
the autumn and winter have so far
prevented floods. The Monongahela
and Allegheny are generally frozen
over in November, and do not
loosen up until spring.
This year there has been very
little snowfall, the precipitation be-
ing almost entirely of rain which
came frequently and heavy. and
flowed off unchecked by the cold.
Theory Refuted
For many years it was thought
that melting snow was the cause
Of the floods. 1t has been proved
otherwise. One foot of ordinary
moist snow over a square foot of
surface, when melted equals about
one-square foot Of water an inch
deep, so to create floods from melt
ing snow would require a depth Of
many feet on the ground at the
opening Of spring.
The records show that the fall
during the winter months melts or
evaporates within a very short
| time. so that at the beginning of
February throughout the upper Mis-
| sissippi and Missouri valleys, there
Is. from actual measurement on the
ground, an average of about seven
inches Of snow. while in the noun.
tain districts of the northeast the
| average Is less than half a foo1
In the New England districts this
| may be increased by three inches.
During February the depth con-
stantly diminishes and with the ris-
ing temperature of March the snow
in most sections disappears.
Rains Real Cause.
Snow then is not the principal
factor in causing floods, nor Is its
influence in producing or aggravat.
| ing flood conditions to be considered
| when, as the records show, the
| snow throughout the headwaters of
the Mississippi and Missouri rivers
disappear fully one month before
the rivers are open in those dis
| tricts
The question then arises, what is
| the cause of floods?
Shortly after the winter solstice
the low pressure storms which pass
| in from the Southern Pacific or find
a hirfhnlnon hA =
lands of the Southwest, travel
northeastward over the central to
the northeastern States and out the
st. Lawrence valley.
They are preceded and attended
by unseasonably high temperatures
and excessive rainfall. The ground
being still frozen, little or none of
this heavy rainfall percolates the
! soil, but flows off the hard surface
over the drainage system into the
| tributaries.
| The result of these heavy rains
| Is most noticeable in the noun
famous sections and is evidenced
by the February rises in the ALE.
gheny and Monongahela rivers,
| AS soon as the ground softens
sufficiently for the heavy spring
rains to percolate the ground to
any great depth, the floods in the
mountainous districts begin to di-
| minish.
AS the warmer weather is gradu.
ally creeping season by season into
more northern ATTITUDES, floods are
accordingly diminishing in number
and volume.
ADMIRAL COONTZ SPEAKS