FLOOD09727

• County: El Paso
• Community: El Paso County
• Stream Name: Dirty Woman Creek
• Basin: Arkansas
• Title: Dirty Woman Creek and Crystal Creek Drainage Basin Planning Study
• Date: 6/1/1992
• Prepared For: El Paso County
• Prepared By: Kiowa Engineering Corporation
• Floodplain - Doc Type: Floodplain Report/Masterplan

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VI. DEVELOPME!';T OF AL TERNA llVES AND RECOMMENDED PLAN
The concepts which are available of handling: stonnwater runoff within the Dirty
Woman and Crystal Creek ba,ins have been pre<;emed and di'iClIssed in the previous
chapter, The process of combining the various channelrre;llmem options and roadway
crossingslrucrurcs imoacontiguous plan for all of the reaches lsprese ntedinthis
chapter of the report, As a reslllt of the evalualion of tile flood control, habilat, open
space. operations and maintenance, and water qualilY COlll-eroS within the basins. the
fol1owing concepts weTe identified as having sufficient feasibility to warrant further
evaluation and review:

outside bends of the drainageways and the audet, o~ roadway bridges or culverts which
cross the drainageway would be the area~ primarily su':ljectto selective improvements,

Channel Concepts:

Channe1Altematives
Presented on Table 6-1 is a matrix of channel allemativeswhich wereevaiuated.
All reaches of Crystal Creek and Dirty Woman Creek had at least three alternative,
aoalyzed,Forthechannelizationandselectiveimprovementconcepl.>.acostcomparison
has been completed. Presemed on Table 6-2 is a comparison of the total channei cost and
unit cost per fool for each concept. The costs do not include an allowance for land
acquisition for channel improvements, or for the telocation of uti I ities associated with the
conSllUctionofehannclimprovemenlS.

AoodplajnPreservation
Channelization. 10. or IOO-year
SelCClivelmprovements
Channel Concepts: The channel concepts listed above have been evaluated
with respect to the parameters listed in the previous chapter. A concept's feasibility
depends upon its impact, positive or negative, upon the evaluation parameters. The
Floodploin preservolion concept has been considered to be the same as the "do.
nothing" alternative. The floodplain preservation concepl would involve the regulation
of the floodplain limits, gencrally as depicted on the effective and EI Paso County Flood
InsuranceRaleMap.~andasfurtherrefinedinthisdrainagebasinplan, Regulation of the
tloodplain SO that future encroachments are minimized and the floodproofing of
structures which are currently within Ihe lOO-ycar floodplain would pre,umably be tht:
rneth<XIs \lsed '" actrlress the tlood hazard concerns along tht: drainageways.
Channeliwti,m would involve the lining of the Creek into a more confined flow area.
and could be done for either the lOO.yearorlO.ye(lrtlood di:;<;harges. Several typical
channel concept, have been presented. The primary bank lining material would probably
be riprap. Grade control andlor drop structures would be required in a channelization
concept so that the tlood velocitiescOl,ld be controlled to a levell'equiring medium to
heavyriprap. The prcservationofinvert vegetation llpStTeam of grade controls or checks
would help to minimize the amount or invert ,il'l'apl'injl. for the channel concept.
Rcvegetation would occur wherever the native vegetation was disturbed by the channel
construction_ Willows at the toe of the riprap banks would be a minimum replacement.
Selecti~e iml'rol'emen( concept would involve the construction of grade contTob. drop
structures. bank lining", low tl(lW challllel linings. and storm i>C\\'er outlet controt
structures >elcctively sited to resist stream erosion or to RXIuce potential f1(,odinl"
damage~ while minimizing habitat impacts, Areas of future concern ,uch as at the

Cu\vertAltematives
Throughout the Dirty Woman and Cr)'stal Creek drdinageways, roadway
crossings have been constructed. In some locations such as at the major roadway
crossings, Ihe existing crossings are of lOO-yearcapacity. In many other locations,
particularly within the Woodmoor sutx1ivi~ion, the existing culverts are very small, most
having less than a lO-year fiow capacity. The crossings with inadequate capacity
culverts generally have a wide floodplain upstream of the rO<ldway embankment. In
addition to wide tloodplains. wetland and riparian zones exist which could be negatively
impacted by mcreasing the capacity of the roadway culvert, At all roadway cro\~ings
various size culverts were eva\uated_ Presenle-donTahle6-3i~acomparison of culverts
for all roadways crossings over a delineated reach. The primary crittria ill sckcting ~
culvert crossing wastlood hazard, habitat disturbance importance of the roadway with
respect to emergeney access, and conslructability crileria,

lmoact UDon Hahitat
For each of the channel alternatives eV<lluated an estim<lte of each alternative's
potential for dbturbanee of the habitat was made. The acreages presented on Table 5-3
summarized the acreages associated with wetland and riparian areas. mainl)' lying within
the floodplain of the drainageways, Since it i~ the goal of the planning proces, to
identify concepts which will avoid disturbances to the existing habi tatwhereverprJ.clical,
alternative, which would have a greatct le\'el ofdismrbancc compared 10 unothermust
have pn>visions for mitigating the disturbance, Typical dismrbances cau,ed by
channelizution would include lossot'native toeandlorbankvegetati oll.fillingofhistoric
f100dpiains which may contain wetland or riparian habitat, or dcgmdation ot' water