FLOOD00927

• Designation Number: 216
• County: Logan
• Community: Sterling
• Stream Name: Sand Creek and Pawnee Creek Overflow
• Title: Floodplain Information and Drainage Plan - Sand Creek and Pawnee Creek Overflow
• Date: 5/1/1983
• Designation Date: 7/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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V. fLOOD PLAIN INFDRMAT1DN

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Extent of Flooding Under Existing Conditions
Combined flooding by the lOO-year Pawnee Overflow and Sand Creek Flood
events are shown in Plates 2 through 19.!I Maximum flooding south of Highway
14 results primari1y from Pawnee overflows. North of Highway 14. the
highest lOO-year flood depths and inundated areas are produced for the most
pdrt by Sand Creek. lna few locations (see Plate 12J, the indicated
maximum flood elevations should be checked against those presented in the
comprehensive report. These areas are so noted on the maps.

The 5-, 10-, 25-, 50-, 100-, and500-year flood events were the
frequencies selected for the comprehensive analysis (leaf and Resource
Consultants, Inc.,1983). Accordingly,theinformationcontilinedinthis
report will be useful not only for regulation purposes, but also for Federal
Emergency MdnagementAgency Flood insurance ratestttdi'lis and other floodplain
rTl<lnagementactivities.

Floodway
A designated f100dway is not shown in Plates 2 through19. Much of the
flooding is not along an established natural stream, but occurs as imported
water (Pawnee Overflow) and water which is bac~ed up by highway or railroad
embankments. The 1-footrise flood',;ay concept is not applicable to the Sand
Creek and Pawnee Creek Overflow floodplains located in the northern section
of Sterling. The-flood conditions for these flood areas are generally shallow
depths and low velocities.

5~, 10-, 25- !..3Ind 50-year year Events
A knowledge of floods of these magnitudes is important for future
engineering studies and land use planning related to drainage, sub-
divisions, highway construction, Channel improvements, parkS and recreation.
andagricu1tural1ands. Oesign and planning based on floods Of this
rTl<lgnitude should be made only when the hazard to life is non-existent. The
reader is referred to the comprehensive report for a co~plete presentiltion of
the magnitude and extent of these floods.
lOO.=learsyJ'!l.L
Aside from the design of civil works projects, the most importilnt use of
the 100-year flood event lies in designation and regulation of the flood
plain as set forth in state and federal statutes. InCo1orado,floodplain
regulations are based on the 100-yearevent. Participation in the National
Flood lnsurance Program also requires that the jurisdictional authority
designate and ~anage the lao-year flood plain.
lJpon off; cia 1 a pprova 1 0 f the comprehens i ve repo rt and th i s s U"~n4 ry
report by the CO 1 orado Water Conserv~ tion Boud, the area subject to inundation
by the lOO-year flood can be desigllated a flood plain and regulate daccordingly
by Logan County and the City of Sterling. The lOO-yearflood profiles
(Figures P-1 through P.7) may be used on occasions where there is uncertainty
as to flooding depths. Since the profi1es show flood elevations and distances
from a known ~oint, high water marks can be located on site to correct any
discrepancies on the base maps which follow.
500-yearEvent
This flood event is the selected limit of flood risk whiCh is used in
floodplain rTldnagement and flood insurance activities.
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Flood Insurance
The National Flood Insurance Program is the result of federal legislation
"hich enii~les property owners to buy flood insurance at gOl'ernment subsidized
premiums. To be in compliance with the program, local juriSdictions must zone
the flood plain dnd regulate future development in order to minimize damages.
lJndertheprogram,developmentispermittedincertainareilsoftheflood
plain as long as structures are elevated above the lOO-yearwater surface
elevation, or other acceptable flood-proofing measures are taken.
Flood insurance through the Flood lnsurancc Program is available to
all residents of Logan County and the City of Sterling under the regular
program. Both Logan County dnd the City of Sterling have entered the
emeruencyphaseoftheNationa1 Flood lnsurance Program. LoqanCounty
came in on J~nuary J, 1977 and the Ci ty of Sterl i n9 on August 4, 1977.
Insurance coverage and rates ~s of 1986 under the emergency and regu1 ar
programs areas follows:

Y The reader is referred to the comprehensive report for ~peciflc areuS
subject to inundation from each source.

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