FLOOD09420

• Designation Number: 6
• County: Yuma
• Community: Wray
• Stream Name: North Fork Republican River
• Basin: South Platte
• Title: FIR - North Fork Republican River
• Date: 6/1/1969
• Designation Date: 1/1/1970
• Prepared For: Wray, CWCB
• Prepared By: USACE
• Floodplain - Doc Type: Floodplain Report/Masterplan

Point velocities in congested areas may be much higher than the average
shown in the tables. Rates of rise and duration of flooding can assume
varying degrees of importance depending on the basin characteristics
and the flood plain involved. Insteepbasins,suchastheNorthFork
above ~ray storm runoff concentrates quickly and results in high rates
of rise with a relatively short duration of flooding. A flood of
Standard Project Flood proportions would rise to its peak In about
10 hours at a rate of about one foot per hour. The flood would remain
above banks for about one and one*half days. These rapid rise times
and high stream velocities would create a hazardous situation in
developed areas such as in Wray and should be treated accordingly.

would still be so dangerous to warrant extreme caution. As an indi.
cation of the velocities which could be generated by these floods,
tables 3 and 4 show average values computeo at selected locations

inWray.

Intermediate Regional Flood - Velocities
at selected locations
Maximum average velocities
(feet per second)
Left Right
Channel overbank overbank

Table 3.

Mile

ldentlficat10n

22.0
24.9
25.3
25.35
25.5
25.6
25.7

Sewage lagoon
Oownstream of C.B. & Q.
RR.brfdge
Upstream of Main Street
Upstream of Adams Street
Shoppin9Center
Upstream of U.S. Hwy 385
bridge
U.S. Hwy 34 bridge

5.46 1.15 1.86
4.69 1.27 1.38
3.87 1.52 0.86
3.73 2.00 0.93
2.59 1.26 0.23
2.31 0.93 1.10
6.89 1.71 2.33

Hazdrds of great floods. Underestimdting th~ destruc-
tive force of flood flows. especially when depths of flooding are
not extremely deep, is an obvious danger. Velocities greater than
three feet per second in combination with flood depths of three feet
or more are considered extremely hazardous. A velOCity of two feet
per second combined with depthS of two feet or more produce unde-
sirable conditions in developed areas such as would occur at Wray.

Table 4.

Standard pro~ect F100d._~__Yf:!J..ocities
at selecte locations

Potential health hazards attributable to floods normally
include the loss or pollution of drinking water and food supplies;
d~maged, destroyed, or inoperative sewage facilities; and prolonged
flooding conditions that may spread insect-borne di5eases are all
problem5 whiCh mdY be encountered during or after flood events.

Maximum average velocities
(feet per second)
Left Right
Ml1e Identification Channel overbank overbank
22.0 Sewage lagoon 6.07 1.73 2.18
l4.9 l!ownstreamof C.B. . Q.
RR. nridge 6.44 1.99 2.10
63 Upstream of Main Street 5.01 2.32 1.84
25.)5 Upstream of Adams Street 5.01 2.73 2.07
25.5 Shopp1ngCenter 3.90 1.95 0.67
25.6 Upstream of u.S. Hwy 385
bridge 3.63 1.51 1.65
25.7 U.S. Hwy34bridge 7.95 2.63 1.84

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