FLOOD09316

• County: Teller
• Community: Cripple Creek
• Stream Name: Pony Gulch, Poverty Gulch
• Basin: Arkansas
• Title: Drainage Master Plan
• Date: 4/1/1992
• Prepared For: Cripple Creek
• Prepared By: GMS
• Floodplain - Doc Type: Floodplain Report/Masterplan

The recummendatioll.~ fur Upper Cripple Creek cuntained within this report
primarily focus on upgrading or replacing existing structures. It 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 not encroach
upon the flood plain, as defined by the SCS in the Flood Plain Management Study
for Cripple Creek, or make improvemenl'i 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 COll.'itructing a lined channel as shown in Figure 4 of
Appendix 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 thc most conservative recommendations as transitioning open channel flow into
a conduit crossing results insignificant headlosses and increased pipe sizes. Should
storm water runoff in Cripple Creek he collected and cnclosed in a conduit, it may
hecome pos.~ible to reduce the size of the recommended road crossing improvements.
The rollnwing recommendations are made for improvemenl~ to existing structures
within the Upper Cripple Creek basins.

1. Exisling structure no. 3 (48-ioch CMP with 5.5 foot of headwater) is
inadequate to convey runoff from the l00-year designswrm (eapaeity e quais
100 CFS, lOO-year design storm runoff equals 514 CFS). It is recommended
that lhis culvert be replaced with a 96-inch Rcr culvert complete with
wing,,:alls and headwall.. The culvert should have a minimum headwater
depth of 10 feet. Thi, new installation would have a capacity of
approximately 520CFS.

2.

Existing structure no. 4 (7'3" CMP with IO-foOl nf headwater) is a strl.ldure
which crosses Highway 67 and has an existing cap;lci:y of approximately 500
CFS. The 100-year 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-inchculvertshouldbcinstalledadjacenttothe
existing culvert with top of pipe elevations matehing.

3,

Exisling mucture no. 50 is the beginning of approximately 600 lineal feet of
existing conduit between Highway 67 and the museum. This conduit is in
extremely poor condition and must be replaced. The lOO-year design runoff
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 discussed 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 the flow will actually
overtop the roads and encroach upon prupl:rties to the ea~t and west, Even
with the improvements recommended at structure 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 staled that when Cripple Creek is developed it
should be developed based on subcritieal flnw (stahle, low velocity flow rates).
Assuming subcritical flow at this location, Cripple Creek could be confined in
a riprap lined channel (Figure 4, Appendix A) with a bottom width of
approximately!l'andaflowdepthofapproximatelyS'. As this channel is on
undeveloped property, it will he the developers' respolL'dbility to make
relluired improvemenls but until those improvements are made, Cripple Creek
will have to deal with an unmanageable flood plain in this area.

;,

Existing ~trllC1\1re nn. 104 is an inlel which inlcrccpb uverla",J n\Jw frum arClli>
which are nOI tributary to exmmg struct\]r~ no. 50 and conveys it \0 the

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