FLOOD05940

• Designation Number: 325
• County: Teller
• Community: Cripple Creek
• Stream Name: Pony Gulch, Poverty Gulch
• Basin: Arkansas
• Title: Drainage Master Plan - Cripple Creek, Final Report
• Date: 4/1/1992
• Designation Date: 7/1/1992
• Floodplain - Doc Type: Floodplain Report/Masterplan

The reeommendation.~ for Upper Cripple Creek contained within this report
primarily focus on upgrading or replacing existing structures. ft is intended that the
remainder of Cripple Creek be left in Its native condition until such time as
developers of adjacent properties commence development. At that time, it will be
the developer's responsibility to limit development such that it does nO! encroach
upon the flood plain, as defined by the SCS in the Flood Plain Management Study
for Cripple Creek, or make improvemenl, to the existing channel which will confine
the storm flows and reduce the limits of the flood plain. Improvements to the
channel may include either con.~tructing a lined channel as shown in Figure 4 of
Appcndix A or intercepting the flow and enclosing it within a conduit. The
improvements recommended at existing structures are based on the scenario that
Cripple Creek will be left in its native state or channelized. This assumption results
in the most conservative recommendations as traositioning open channel flow into
a condl.lit crossing results insignificant headlosses and increased pipe sizes. Should
storm water runoff in Cripple Creek be eollected and enclosed in a conduit, it may
hecome pos.~ible to reduce the size of the recommended road crossing improvements.
The rollowing recommendations are made for improvemenl~ to existing structures
within the Upper Cripple Creek basins.

1. Existing structure no. 3 (48-ioch CMP with 5.5 foot of headwater) is
inadequate to convey runoff from the l00-year de,ignstorm (capacity e quais
100 CFS. 100-year design storm runoff equals 514 CFS). It is recommended
that this culvert be replacel.! with a 96-ineh Rcr culvert complete with
wing,,:alls and headwalls. The culvert should have a minimum headwater
depth of 10 feet. This new installation would have a capacity of
approximately 520CFS.

2.

Existing structure no. 4 (7'3" CMP with IO-foOl of headwater) is a strl.ldure
which crosses Highway 67 and has an existing cap;lcilY of approximately 500
CFS. The 100-ycar design storm runoff at this location is 550 CFS. therefore,

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the culvert is not quite capable of adequately conveying the full lOO-year
design storm runoff. To adequately convey the fulllOO-ycar design storm
runoff,anadditionaI36-inchculvertshouldbcinstal1edadjacenttothe
exi,ting culvert with top of pipe elevations matching.

3.

Existing muelUre no. 50 is the beginning of approximately 600 lineal feet of
existing eonduit between Highway 67 and the museum. Thi, conduit is in
extremely poor condition and must be replaced. The loo-year design runuff
in Cripple Creek at this location is 553 CFS. It is recommended that an
11'5"x7'3" arch culvert with headwall, winb'Walls and a minimum headwater
depth of8 feet be installed at this location. Once flow has entered the pipe,
the pipe size can be reduced as will be discus>ed in Item 6 below.

4.

Between existing structure no. 4 and no. 50 Cripple Creek does not flow in a
clearly defined channel but rather spreads out between Fifth Street (Highway
67) and Bison Street. During periods of intense storms thc flow will actually
lJvertop the roads and encroach upon propl:rties to the ea~t and west. Even
with the improvement, reeommeoded at ~tructure no. 4 aod no. 50 the city
will have to deal with an unmanageable flood plain until such time as flow is
channelized. The SCS has stated that when Cripple Creek is developed it
should he developed based on subcritical flow (stable, low velocity flow rates).
Assuming subcritical flow at thi, location, Cripple Creek could be confined in
a riprap lined channel (Figurc 4, Appendix A) with a bottom width of
approximately!l'andaflowdepthofapprnximately5'. As thisehannel is on
undeveloped property. it will be the developers' n:spolL'dbility to make
n::lluired improvements but until those improvements are made, Cripple Creek
will have to deal with an unmanageable flood plain in this area.

;.

Exi'ling strucmre no. 104 is an inlet which inlereepb over1...",J fl\Jw from area.-.
which are oot tributary to exmmg struct\Jre no. 50 and conveys it to the

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