FLOOD10336 ‎(2)‎

• County: Adams
• Community: Brighton, Commerce City and Thornton
• Stream Name: South Platte River
• Title: Flood Hazard Area Delineation, South Platte River, Adams County
• Date: 4/1/2005
• Prepared For: UDFCD; Adams County; Brighton, Commerce City, Thornton, Metro Wastewater
• Prepared By: CDM
• Floodplain - Doc Type: Floodplain Report/Masterplan

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0611\40892\PREP-FHAO\S3.DOC

CDIII

4/5/05 Cje

3-5

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3.4 Summary

The flows of the South Platte River in Adams County are influenced by a variety of factors, including snowmelt
from the Rocky Mountains, storm events upstream and within the Study Area, trans mountain diversions into, and
irrigation and municipal diversions out of the watershed, in addition to municipal return flows. The inherent
variability of the river's flows has been tempered significantly by construction of Bear Creek, Chatfield, and Cherry
Creek Dams. However, the estimated 100-year peak flows have not increased over time due to the construction of
upstream dams. Although Chatfield, Cherry Creek, and Bear Creek Reservoirs provide significant flooding
protection to the Study Area, flooding potential from the contributing drainage areas downstream of these facilities
remains. Flow for the SOD-year event, which were not included in the Master Plan hydrologic modeling, were
developed using upstream identified FIS SOD-year flows (U.s. Highway 85, Clear Creek, and Todd Creek) and
multiplying those flows by the ratio of the 100-year flow at the cross-section in consideration and the upstream
cross-section. Discharge profiles are shown in Appendix A.

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4/8/05

Section 3
Hydrology