FLOOD05827

• County: Boulder
• Community: Boulder
• Stream Name: Boulder Creek
• Basin: South Platte
• Title: Boulder Creek Phase B
• Date: 12/1/1979
• Prepared For: Boulder
• Prepared By: UDFCD
• Floodplain - Doc Type: Floodplain Report/Masterplan

SECTION III
HYDROLOGICAL SUMMARY

using the Environmental Protection Agency's Storm Water Management Model

(SWMM). Historical stream gaging records were used to check the result

obtained from the SWMM. The results of the restudy revised the estimated

100-year discharge at Boulder from 7,400 c.f.s. to 12,000 c.f.s.

The development of a drainage basin master plan must be based on factual

information concerning the volume of storm runoff as well as the magni-

tude of peak rates of flow. Sound, adequate and thorough hydrological

studies must be undertaken to furnish this information in order to first

determine the flood problem, and second to suggest and evaluate possible

solutions to these problems.

The final hydrology study accepted by both the Urban Drainage and Flood
Control District and the City of Boulder is contained in Water and

Related Land Resources Management Study; Metropolitan Denver and South

Platte River and Tributaries; Colorado, Wyoming, and Nebraska; Volume V,

Supporting Technical Reports and Appendices; Appendix H, Hydrology. The
discharge frequency curve and Probability Discharge Profile for Boulder

Creek, extracted from this report, are presented in Figures 111-1 and

I I 1-2 respectively. The 100-year hydrograph for Boulder Creek is

presented in Figure II i-3.

A flood may be defined by a peak flow rate and an exceedence interval.

The exceedence interval is defined as the average interval of time

between peak flow rates that equal or exceed a specific magnitude given

a sufficiently long period of time. The total period of time under

consideration must exceed 1,000 to 10,000 years before the 100-year

exceedence interval flood magnitude can be expected to be exceeded on an

average of once for each 100 years.

In the aftermath of the May 1969 flood, the Corps of Engineers prepared
a Flood Plain Information Report for Boulder in August of 1969. The
hydrology of the Boulder Creek basin was studied during the preparation

of this report and the lOO-year discharge was estimated at 7,400 c.f.s.

using regional stream gaging records and statistical metnods.

In 1977, the Corps of Engineers prepared a draft report on Boulder Creek

for the Metropolitan Denver and South Platte River Study. The hydrology

of the Boulder Creek basin was restudied in conjunction with this report

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