FLOOD11751

• County: Statewide
• Basin: Statewide
• Title: Floods in Colorado
• Date: 1/1/1948
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Front Range some precipitation, even' in winter is caused by moisture
from the Gulf. In general, however, the snowfall is heaviest on the
western ranges, and its mclting in June has a greater effect on the
flow of the streams in that region than the melting of the snow over
the eastern ranges has upon the streams draining the Front Range~
In late spring, precipitation not only along the Front Rfinge but also
farther west sometimes augments the melting snow sufficiently to
cause floods.
Precipitation in the plateau region is so light during the summer
that floods rarely oreur. East of the Front Rfinge general precipita-
tion is rarely sufficient to cause floods

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FLOODS

OCCURRENCE OF

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AREAS SUBJECT TO FLOODS

From observation of the effect of topography on precipitation it is
evident that floods occur most frequently on the eastern slope of the
Front Range both in the South Platte and the Arkansas River BasinS.
In the mountains farther west precipitation is insufficient to cause
floods, except during the period of melting snow in June. At that
time the severity of the resulting floods is dependent not only on the
rainfall but also, and to a greater degree, on the depth of snow cover
and the rate of the seasonal rise in temperature. Hence, only floods
caused by rainfall on melting mountain snow occur simultaneously
throughout the greater part of the State. The most severe floods of
record on the Rio Grande, South Platte, Colorado, and Gunnisou
Rivers have resulted from this cause, as have the outstanding floods
that occurred before gaging-station records began. During the storm
of June 2-7,1921, the combination of melting snow alld rainfall caused
severe floods on all the major ri\'ers except the Arkansas. Over the
Arkansas River Basin the storm, influenced by the topography, was
concentrated in a series of cloudbursts in the foothills just east of
Canon City. These cloudbursts caused the most severe flood on the
Arkansas River ever recorded, and at a tin).e when the water from
melting snow from the higher areas was insignificant in amount.
, The tributary streams in the South Platte and Arkansas, River
Basins are subject to heavy rains of cloudburst intensity which cause
the cloudburst type of flood, the peak discharge of which is greater
than that caused by rainfall, during the period of melting snow.
Whenever heavy rain occurs along the Front Range; particularly in
the lower foothills, it is usually concentrated in cloudbursts at various
points. The cloudburst flood flowis of such short duration, the peak
lasting only a few minutes, and the total quantity of water during the
flood is so small, that when it re!1chesa largerstream, channel storage
quickly reduces it toa stage which is not a serious flood. ,This is
well illustrated by the typical stage hydro graphs shown in figure 2.

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I

e FLOODS IN COLORADO
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