FLOOD00457

• County: El Paso
• Community: Colorado Springs and Manitou Springs
• Title: Paleohydrologic Flood Investigations for Streams in Manitou Springs and Colorado Springs
• Date: 12/3/1987
• Floodplain - Doc Type: Flood Documentation Report

the stream banks is 3 feet above the streambed. This indicates recent
streamflow have not exceeded about 200 cubic feet per second.
From the switchback in the road and downstream to where the
channel is contained in a long culvert the road (age unknown) has
modified and constricted the channel. The channel since the road was
built average 5 feet in width. Recent organic flood debris and in
channel small depositional features indicate the water may not have
been much deeper than about 3 to 4 feet in the last 10 to 20 years.
This would indicate a recent peak discharge of 200 cubic feet per
second. Had flows any larger than this occurred the Cave of the Winds
road would have received substantial damage. A review of maintenance
records (if kept and available) for the road flows may provide
additional flood information. Existing hydrology indicates peak
discharges frequently exceed 200 cubic feet per second; hence, the
road, particularly in the 'narrows' would be eroded often. Has this
been the case?

Ruxton Creek
Ruxton Creek drains 17.6 square miles and is steep, particularly
in the lower third of the basin. The channel is contained in a
concrete flume in Manitou Springs upstream to the Pikes Peak railroad
station; hence paleohydrologic studies could not be done. Upstream
from the railroad station the channel is filled with many large
boulders (some as large as houses) that have rolled off the steep
canyon walls into the channel. In many reaches the low streamflow
flows under these rocks. The channel at an elevation of about 6,800
feet was moss and lichen covered except for about 2 feet above the
streambed. The channel here averages about 10 feet and the boulders
in the center of the channel are well rounded and polished smooth.
Small gravel bars occur, there is some evidence of erosion of the
channel banks, and some trees in the channel recent scars and contain
flood debris. The channel evidence suggests that recent flows had a
depth of 2 feet; hence, assuming a mean velocity of 10 feet per second
the peak discharge is estimated to be about 200 cubic feet per second.
This discharge is one that is considered to occur frequently, say once
every year or two.
At an elevation of 7,000 feet, the only significant flood
deposits that ,could be identified in any part of Ruxton Creek, are
flood deposits! consisting of boulders 12 to 18 inches in diameter on
the side of the channel and lodged against a 2-foot diameter spruce
(estimated to be about 120 years old) to a depth of 4 feet. Channel
width is 25 feet; the mean depth is 3 feet. These deposits represent
the largest flood that has occurred in Ruxton Creek had a peak
discharge of approximately 750 to 1000 cubic feet per second. (These
deposits probably were from the 1882 flood (U.S. Army Corps of
Engineers, Flood Plain Information report, Fountain Creek, 1974).
Moss and extensive lichen cover boulders in the channel to within 1-
foot of the streambed. Boulders in the channel are not very well
rounded indicating floods do not move the boulders very frequently,
nor are they abraided by sediment-laden water.

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