FLOOD03324

• County: Logan
• Community: Sterling
• Stream Name: Pawnee Creek
• Basin: South Platte
• Title: Flood Hazard Mitigation Feasibility Study
• Date: 3/1/2001
• Prepared For: Logan County
• Prepared By: ICON Engineering, Inc.
• Floodplain - Doc Type: Project

URS Greiner Woodward Clyde for the Federal Emergency Management Agency, Region VIlI, A copy
of Ibis rejJ<.lrt is localcd inthc Appendix.

Table 2. Peak Di~cha,>:cs Alon~ Pawnee Creek Main Channel Under Existin~ Conditions

Locatio!!

,JO-Year.'
(Cfs)
1517
1517
2945
3264

.";.505l;~ar'~.-
~_.";(ef.~,,,.,
2026
202
5434
6729

~100-Yean"
'<' (cfs)'1i:<""
2226
2226
6645
8611

*Moutb (South Platte River lOO-YearFloudplain)
.Upstream HWY 6
'Upstream CR. 33
'UpstreamCR.31
'SplLtllowseau,ereduoeddl<ch11l"gemthema\nchannel

V, FIELD REPORTS

On July 30111, 1997, an intense r.linstorm oecurR-d in the Pavmee Creek ba..~in. Personnel from the
CWCB were informed of the stonn and traveled to Sterling before floodwaters began moving into the
city limits. Their observations and subsequent analysis and evaluation of the !loud is summari...oo in a
report titled, "Pavonee Crcck, Logan County, Colorado, Flood of July 1997" and located in the
Appendix. Tbe CWCB also authorized the preparation of an overview report of the 1997 flood season
for the emire state. A document titled "Colorado's 1997 Flood Season in Review" was published in
August 1998 and prepared by Riverside Technology. lnc, The portion of this document that pertain~ to
LoganCoUllty is located in thl." Appcndix,

VI. ALTER.."IATlVE EVALlJATlO]'l;
n'____

l3ased una review of the existing repol1S and discussions with the project spunsors and local eiti7<:lls.
six alternative improvement projects were selected for further study. A conceptual desi~n of all of the
proposed projects was completed io su!lieient detail !Odctcrmilleretativeeon~truetionquantities, cost
estimates, and exp<x:ted benefits. Approximate locations of the alternatives are shown on Figure 8.
Each Alternative, with the exception (If the "No ActiQn" Alternative, protects varying lengths of the
area surrounding th<e lower pUl1i,lrls of Pawnee Creek, and the Pawnee Creck overflow, Common to
cach alternative (except for Alternative No. I the "No Action" Alternative), but not discussed in detail
are flood warning system8 and maintcn,mee programs. The altemative.~ studied are as I<lllows:

Alternative No. I: "No Action" ::dtemative, A series of seven public meetings with landowners and
concerned citi?.cn~ were held between December 1997 and January 1998. Tbis alternative was
unifunnly notuceeptable given the past scries ofseriolls 1100dcven tsandsllbsequentdamages,

Alternoti~" No.2: This alternative will restrict the lOO-year Hood flows fwm \lVerllowing into the
left overbank floodplain near where the Pawnee Creek crosses HWY 6. Protection would be provided
to agrieultutallands and !.he City of Sterling. Thi8 alternative wa~ the rcr;ornmcmkd altcmativc frum
d,e "Ciiy of Sieriillg uwinage ami Flood C'<,niroi impicmcmalion Pian" daced illlle 1997. LIIl'
:dtemativc is ~h(}wn on Figure C) and consists ofa system ofl100d contIollcvce~, In general. the levee:;
"'<lulu [0110'" along the nonh ,ide of Pawnee Creek hcgi'llIing up~trcam ofeR. 29 and continuing east
to HWY 6, Sine{' the levees would be de8igned [m the IOO-year storm, they w'lUld I>c required to have
3 feet of freeOOm! b)' FEMA. TIle existing bridges at HWY 6 would be improved lo convey the 100-
year discharge under the bridges. For the southboundlan<:s, the existing concrete bridge would be

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