7087 - Laserfiche WebLink

Home Browse Search

Deerlodge Park was 16,500 ft~/s and the 1983 instantaneous peak discharge was 23,400 ft3/s. In 1983, the flood plain at Deerlodge Park was inundated by floodwater for several days during the peak runoff. Recurrence intervals of annual maximum daily mean discharges were estimated for the 1982 and 1983 streamflows at Deerlodge Park using the 43 years of streamflow record, and a Log Pearson Type III analysis (U.S. Water Resources Council, 1981). The 1982 peak daily mean discharge had a recurrence interval of about 3 years, and the 1983 peak daily mean discharge had a recurrence interval of about 20 to 25 years. The combined long-term mean annual streamflow of the Yampa River near Maybell and the Little Snake River near Lily is 1.5 million acre-ft/yr (U. S. Geological Survey, 1982). In 1982, the combined annual streamflow of the Yampa River near Maybell and the Little Snake River near Lily was 1.9 million acre-ft, and in 1983 it was 2.3 million acre-ft. A flow-duration curve is a cumulative frequency curve that shows the percentages of time specified discharges are equaled or exceeded during a given period. It combines into one curve the flow characteristics of a stream throughout a range of discharge, without regard to the sequence of occurrence (Searcy, 1959). Historical streamflows at station 09251000 Yampa River near Maybell and station D9260000 Little Snake River- near Lily were examined to determine an appropriate period of record for estimating the long-term flow-duration curve at station 09260050 Yampa River at Deerlodge Park. Flow-duration curves calculated from 10-year increments were compared for each site. In the decade of the 1920's, days when discharge was very low occurred much less frequently than in other decades. By contrast, in the decade of the I930's, days when discharge was very low occurred much more frequently than in other decades. streamflow of the decades since 1940 has been relatively uniform and has had a greater effect on the present channel morphology than has streamflow from earlier in the century; therefore, only discharge data recorded since 1940 was used in streamflow analysis. Along-term (1941-1983) flow-duration curve for Deerlodge Park was computed from the daily sums of daily mean discharges recorded at the Maybell and Lily gaging stations. This curve is presented in figure 6. SEDIMENT TRANSPORT AT DEERLODGE PARK The relation between water discharge and sediment discharge at Deerlodge Park was used to quantify the amount of sediment entering the Yampa River Canyon. The total sediment load of a river can be divided into two compo- nents: (1) Suspended-sediment, which is the relatively fine material (clay, silt, and some sand-size material) transported in suspension; and (2) bedload which is coarser material (sand, gravel, and cobble sizes) that moves by rolling or bouncing along the bed. Measurements of both suspended sediment discharge and bedload discharge were made at the Deerlodge Park study reach during the spring and summer of 19$2 and 1983. Supplemental streamflow and sediment data were collected in 1983 at two additional sites (fig. 3). Suspended-sediment measurements were made at station 09260000 Little Snake River near Lily to provide additional information an sediment entering the Yampa River. Also, discharge measurements were made and sediment samples were 11