FLOOD05212

• County: Larimer
• Community: Fort Collins
• Stream Name: Boxelder Creek, Spring Creek, Dry Creek
• Basin: South Platte
• Title: Flood Control for Boxelder Creek at Fort Collins
• Date: 2/1/1993
• Prepared For: Fort Collins
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

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REAL FSTATE SECTION

The Real Estate inkrest used for this study was fee title for the diversion
channel with a 15-foot-widc temporary work area easement running along each side
the proposed channel. The proposed tOO-year diversion channel will require the
acquisition of 35.17 acres of fee title and 3.21 acres of temporary work area
easements. The diversion channel alignment runs through. four different lOnings and
will affect 18 landowners. The wnings within the corridor and the acreages within
each zone are commercial (3.16 acres of fee title and 1.82 acres of casements),
industrial (3.77acres olfee title), residential (12.2Sacres of fee title and O.67acres
of easements) and agricultural (15.99 acres of fee title and 0.72 acres of easements).
There is only one residential dwelling that will require relocation beneflts under
Public Law 91-646 for both the I()().year and 3D-year diversion channel plan. The
total estimated Real Estate cost for the tOO-year diversion channel project is
$463,201. Real Estate cost estimate and typical fee title and temporary work area
easement agreements are presented in Appendix D.

The proposed JO..year diversion channel will require the acquisition of 29.02
acres of fee title and the total estimated Real Estate cost is S360,000.

The alignment for the IOO-year and 3o-yea.r diversion cl1annels are virtually the
same, with only the width varyin/!:.

No acreage or value has been included for a dump site for wasting e~ccss
e~cav~tion material.

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fl.OODlNG IMPACTS

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With the l()().yearpJan in place, Dry Creek dischargeS would be significantly
m:luccd from Uuimcr and Weld Canal to it's confluence with the Cache La Poudre
River. Tahie 6-1 shows a comparison of discharges for existing conditions and with
diversion of flows. The water surface profiles for Dry Creek also reflect a reduction
in stage from Uuimer and Weld Canal downstream to the mouth for the with-
diversion channcl COIldition. Plates 9 and 10 show the nood profiles for uisting
conditions with the lOO-)'ear channel diversion and plates 11 and 12 show the
without-channel diversion, beginning at the mouth and ending at Larimer and Weld
Canal.
To determine the effocts of floods greater than !he lOO-yearevent on the 100-
year plan, the splil.flow option was utifu.ed to determine the amount of discharge
that would pass over the diversion weir and into Larimer and Weld Canal during a
5oo-)'ear event. II was determined that approximately 1,550e.f.s. of the 9,420 c.f.s.
500-year discharge would pass over the weir and into Larimer and Weld Canal, while
7,870e.f.s. would pas~ down the diversion channel. It was assumed that the 1,550
c.f.s. ovcrflow from the SOO-year evcnt would breach Larimer and Weld Canal and
now downstream. Thcre would be little induced flooding from the Soo.year event
along the diversion channel downstream from Willox Lane because thc majority of
the flow would be contained within thc channel or frcel>oard wne. The profiles alson
show that the ]OO-yt'<tf c:h~nn..l (\;vf:'r~i(lf! rrofl!e~ WQ'21<! ~~V:rb: wi:..': :'':c cx::~:;r.g

Dry Creek profiles about ISoo feel upstream from the location where Dry Creek
flows would eflter the diversion channel.

With the IOO-yearchannel diversion plan, the residual flood damages from Dry
Creek between J..ar:mcr and Weld Canal and CoUcge Avenue could be reduced or
eliminaled throu~h localized channel improvements. ineluding channd d.."nnlll atId

6-6

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