FLOOD09306

• Designation Number: 204
• County: Larimer
• Community: Fort Collins
• Stream Name: Spring Creek
• Basin: South Platte
• Title: Major Drainageway Planning - Spring Creek, Fort Collins, Larimer County, Colorado
• Date: 8/1/1980
• Designation Date: 1/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

3,

~fidisturbed \.ater surtace e levdtlofi is rea I ized.
Regulation of the flood fringe area (as idel'ltified in tllis report} re-
quiring elevation of structures a minimum of 1 foot above the loo-year
floodway water surface elevation.
Adoption of regulations requiring future develO~l"Sto provide open space
to safely convey the lIl1detained lOO-year flood event (Table 14) ina
f]oodway cl1annel meeting design standards recorrrnended by the City of
Fort Collins and meeting minimum right-of-way as defined in Tabl e14.
Adoption of a policy by the City of Fort Collins to obtain through de .
dication floodproneprooerties. orto obtain sufficil>nt right-rot_way tn
al1awforchannel improvements that may becor<Je cost effective.

The improvements for th; s a 1 tern,l-t i ve a re further described ill t.~e to 11 0\\'1 ng:
GroupA-Channel improvements to convey the 100-yearflowweremade through-
out these reaches. Improved culverts were designed for Timberline
Road, the Colorado & Southern Railrwd, at Welch Street, and at the
cruss i ng upst ri!am of Le~lay Avenue. A series of berm> were des i gned
for the area downstream of the Union Pacific Railroad, South of
EdoraRoad, upstream of Welch Street and just upstream of LeMay
Avenue. A concrete lined channel with vertical side slopes was de-
signed for an area of approximately 320' downstrNm of Stover Street
to reduce the riqht-of-way required. An improvedgrass.lined
channel was designed for the remainder of the reaches downstream to
theCachela Poudre River. Design discharges ranged from4800cfs
to5000cfs.
GroupB-Aconcrete-linedchannelwithvertical side slopes was designed for
theareabetweenStoverandStuartStreets,inordertorninimizethe
necessary right-of-way. Flows were conveyed from Stuart Street to
just oownstreanlofCol1eqeAvenue indn improved qrass-lined channel.
Just downstream frOln College Avenue a cuncrete~ 1 ined channel is aqa in
used to minimize the right~of-way required. A new crossing structure
is required at RemingtonStnoet. A grass-lined channel was designed
through the mobile home pdr~ upst~,lm of College Avenue to approxi-
matt"ly600' east of Arthur's Ditch. This channel was designed for
dlOO-yeareventan<iinclu<iesanewClJlvertatBayRoadandatrhc
Colorado dnd Southern Rdilroad. A gdbion drop structure was also
required upstream of College Avenue. Berms were placed downstream
of ArtlllJr' s Ditdl, illorlg 5nl!ely Dr iv~. ~nd downs It"Cdm of Shie Ids
Street alongtneSouth bank Of Spring Creek. I\r: i:nprovedcanal
crossing is requiredatArthur's;:litch. The design discharge in
these reaches varied from 3100 cfs to 4500 cfs.
.50-

.,

5,

This alternative prevents an increJse in average annual damages that might be expect-
ed from future floodplaindeveloprr,ent, and will serve to decreaseexi,ting i1verage
annua I <Jdrndge~ over a long period of t iIT!2.

Alternativet2
The undetainedlOO-year flood event for fully developed basin con ditionswasthe
design flO';,chosenforthisalternative. Areas of existing detention including the
ponding sites behind tile Taft Hill lloademb,ll1klfli'nt, the Colorado a ndSouthernRail-
road embankraent urstreal11 of College AVf'nuf', ~nrl the Colorado and Southern Rai 1 road
upst~am of Timberline Road were eliminated by increasing the flow capacities
through thcs.e embankml!nts.

This al ternative 'lias chosen becduse of the uncertainty in relyinq on inadverten~
<.:e:elllion b~hind roadway and railroad /lfIlMnkrof'nts. By designing for thp. undetalnetJ
flow, ccncern~ for ,afety of tr.e embankment under loadings ar.d concerns. for the
pI'eservatiorl and maintenaltce of the embank~l<:mt ilre avoided.

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