FLOOD05175

• County: Summit
• Community: Breckenridge
• Stream Name: Blue River
• Basin: Colorado Mainstem
• Title: Technical Addendum Floodplain Information Blue River
• Date: 12/1/1974
• Prepared For: Summit County
• Prepared By: Leonard Rice Consulting Water Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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DESCRIPTION OF FLOODING

The following paragraphs discuss flooding factors in each
reach of the BI~e River through the ~town.

Goose Pasture Tarn to Broken Lance Road (U/S)

The flood plain in this reach is largely undeveloped except in
the area near Broken Lance Road (U/S) and the Highway 9 cross-
ing area. Floods are generally confined to the channel and
adjacent lowland area. A flood through this area will collect
considerable natural debris which may cause plugging of the
two crossing structures.

The Highway 9 crossing structure is adequate for both SPF and
IRF flows. The bridge structure for Broken Lance Road up-
stream crossing has an adequate capacity to pass the IOO-year
flood. There will be, however, a very high velocity and scour
is possible downstream of the structure. There is also the
potential of eating away or erosion at the banks upstream. To
protect against the SPF the road approaches to the bridge could
be raised approximately ~ to one foot which would contain the
SPF flows to the channel. The bridge also has the capacity to
pass the SPF flood, but again structural damage due to the high
velocities could occur. A house built adjacent to the river
channel upstream of Broken Lance Road (U/S) could be subject to
flood damage.

Broken Lance Road (U/S) to Broken Lance Road (D/S)

The IRF flood flows are confined to the channel and immediate
lowland area. The SPF is overland due to the upstream bridge
crossing. There is no development within the path of the SPF
flood, however, One dwelling is surrounded by SPF floodwaters
but appears high enough to be relatively safe. Prolonged over-
land flow could cause erosion of the bank upon which the dwell-
ing is situated.

The Broken Lance Road downstream crossing consists of two 6
foot diameter reinforced concrete pipe culverts. The capacity
of these culverts with no plugging by debris, is adequate for
the IOO-year flood, although some flooding due to backwater
will occur upstream. This structure, because of its upstream
location and limited waterway area, has the potential for being
plugged up with natural debris and tree limbs in the event of a

~ Leonard Rice Consulting Waler Engineers. Inc.