FLOOD07072

• County: Statewide
• Stream Name: South Platte
• Basin: South Platte
• Title: Water and Related Land Resources Management Study Volume IIIC - Appendix A
• Date: 7/14/1980
• Prepared For: South Platte and Tributaries
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

.

Table 6
South Platte River Travel Times

From Chatfield Dam

Elapsed Time
(hours)

To Denver Gage
To Henderson Gage
To Kersey Gage
To Weldona Gage
To Balzac Gage

9
15
33
45
60

The routings were done on a mean daily basis. The longest period

averaged was a 2-day mean. .The routed holdout values were used

to adjust the natural flood peaks using a mean discharge-peak

relationship. Holdouts were based on a reservoir system release

criteria which assumed that reservoir outflow would be shut down

to zero when the Denver gage indicates a flow of 5,000 cubic feet

per second. This theoretical operation of the South Platte reser-

voir system affected peak flows occurring in 1912, 1914, 1921, 1933,

1935, 1942, 1947, 1949, 1957, 1965, 1969 and 1973. The adjustments

are illustrated on plates 18 through 20 where the magnitude of the

actual event is plotted at the frequency occupied by the modified

flow. Although these studies indicated an apparent controlling

effect at the gaging stations downstream from Kersey, it was so

slight that it was considered negligible and no gaging station

flows were adjusted past that point.

DISCHARGE-PROBABILITY CURVES

Discharge-probability curves were developed from the adjusted

gaging records discussed above. Although the statistical techniques

used varied somewhat from station to station, they were all based

on a log Pearson Type III distribution. A top half analysis was

.

32