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<br />United States Department of the Interior
<br />GEOLOGICAL SU~YJ;:Y
<br />BOX 25046 M.S, ~
<br />DENVER FEDERAL CENTER
<br />DENVER, COLORADO 80225
<br />
<br />RECti."
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<br />NOV28.'89
<br />...;()LOHAOO WAr_ .., .
<br />CONseRVA'I'IOfj
<br />BOARD
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<br />IN REPLY REFER TOI
<br />
<br />September 6, 1989
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<br />MEMORANDUM
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<br />TO: The Record
<br />
<br />FROM: R,D. Jarrett, WRD, NRP, Lakewood, CO
<br />
<br />SUBJECT: Flood Deposits in Jim Creek near Winter Park, Colorado
<br />
<br />On August 8, 1989 at a meeting at Colorado State University, Dr. Mike
<br />Harvey, Water Engineering and Technology, Fort Collins, mentioned that he
<br />had seen some moderate-size flood deposits in Jim Creek near Winter Park,
<br />COlorado, at an elevation of 9,400 feet. Dr. Harvey had been conducting
<br />hydrologic investigations in Jim Creek associated with US Forest Service
<br />studies of the effects of channel diversions on Jim Creek channel
<br />morphology. Mike is aware of my extensive interdisciplinary studies
<br />(analysis of streamflow and precipitation data and paleohydrologic
<br />investigations) that have indicated a lack of significant rainfall
<br />flooding in streams above 7,500 feet in Colorado. On September 2, 1989 I
<br />conducted a preliminary onsite investigation of the deposits in Jim
<br />Creek. One of the main goals of the site visit was to determine if the
<br />deposits were from a waterflood or a debris flow. Following is a summary
<br />of my observations. I spent about 4 hours hiking upstream along the
<br />channel.
<br />
<br />JIM CREEK BASIN
<br />Jim Creek is a 5.5 square mile basin at it's confluence with the Fraser
<br />River at Winter Park. From 1907 to 1910 streamflow records were
<br />collected at Jim Creek at Winter Park (streamflow-gaging station number
<br />09023000) located near the confluence with the Fraser River. No peak-
<br />flow data are available because peak-flow data were not collected. The
<br />elevation of the gage was about 9,200 feet. The highest point in the
<br />basin is 13,391 feet at Parry Peak. Vegetation below treeline, at an
<br />elevation of about 10,800 feet, consists of. aspen, spruce, and willows,
<br />with a dense natural grass ground cover. Above treeline, little
<br />vegetation grows on the steep bedrock slopes. The basin is located on
<br />three USGS 7 1/2 minute topographic maps; Fraser, East Portal, and
<br />Empire.
<br />
<br />DESCRIPTION AND INTERPRETATION OF FLOOD DEPOSITS
<br />My first stop was at the highway crossing of US 40 opposite the entrance
<br />to Winter Park ski area. There were no significant flood. deposits
<br />located here. The channel averages about 15 feet in width and the
<br />channel gradient is about 2 percent. There was only a trickle of water,
<br />because the Fraser River Diversion canal, about 0.5 miles upstream from
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