FLOOD07039

• County: Summit
• Community: Breckenridge
• Stream Name: Blue River
• Basin: Colorado Mainstem
• Title: Breckenridge Community File
• Date: 1/1/2001
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Community File

The Master Drainageway Planning shows a Peak at Col fax of 2400 cfs. Based upon the
hydrographs mentioned . above, this flow can be assumed to be from local drainage only.
Since this study is later ffild more up to date, this Q is assumed to be the local flow.
:Jwever, the Q from Kelly Road Dam is only SO cfs in this study, and the existing out-
let Q from Kelly Road Dam (at this location) is 2800 cfs. This is still larger than
the new inflow Q of 2400 cfs, so use 2800 cfs here.

Monteview Boulevard - Stapelton local inflow controls and is larger than the Q from
Kelly Road Dam, which has nD effect use Q's from master drainageway planning report.

10-Year

Assume same hydrograph configuration as that of the 100-year:

1. Local inflow will net effect Q from Kelly Road Dam. Lag time between two
peaks will be large if not larger than 100-year since flows will be smaller.

2. The peaks fom the hydro graph portions from the pond when routed downstream,
will be reduced or remain the same like that occuring during the laO-year.

Based upon these assumptions, since in the Flood Hazard Delineation, the total peaks
increase substantially from the peak at Kelly Road Dam, they must be due to local flow.
Therefore, Kelly Road Dam has no effect from Colfax to the mouth and the peaks in the
Master Drainageway Planning Report can be used since these peaks are the most up to
date.

SO - Year

This was not brought up
channel is to be 3' above
the 01 d box.

in the construction drawings but was field verified.
the invert of the new channel and will carry away the

The old
cap of

Was interpolated on log probability paper using the location above Stapel ton and the
Jtal Q below Stapelton.

SOD-Year

At Colfax the SOO-year will be the same as at Kelly Road Dam. And at all locations
downstream to Stapelton the SOD-year is the same. The local inflow is assumed to not
exceed the 5500 cfs outflow. The reasoning is because the SPF is constant or decreas-
ing below the dam, meaning local inflow is not controlling for extremely low frequency
even ts.

Special Areas

Below Stapel ton Airport - Due to the improved channel upstream of Stapelton, the
natural detention storage in the area may change. However, the constructed channel
does not vary enough from that shown in the Master Drainage Plan to effect the outlet
Q. Use discharges in Master Drainage Plan.

Reduced Channel Q at Monteview - The construction drawings on schedule 1 and II show
a reduction in Q to 1000 cfs. This is probably due to the old stom sewer is carrying
some of the flow (500 cfs)