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Point velocities in congested areas may be much higher than the average shown In the tables. Rates of rise and duration of flOOding can ass~me varying degrees of importance depending on the basin characteristics and the flood plain involved. Insteepbasins,suchastheNorthFork above Wray 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*ha1f days. These rapid rise times and high stream velocities would create a hazardous situation in developed areas sych as in Wray and should be treated accordingly. woyld 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 computed 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 Identification 22.0 24.9 25.3 25.35 25.5 25.6 25.7 Sewage lagoon Downstream of C.B. & Q. RR.br1dge Upstream of Main Street Upstream of Adams Street Shopping Center 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 O.g) 2.59 1.26 0.23 2.31 0.93 1.10 6.89 1.71 2.33 Ha~drds 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 ha~ardous. 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. hble4. 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; damaged. destroyed, or inoperative sewage facilities; and prolonged flooding conditions that may spread insect-borne diseases are all problems whiCh may be encountered during or after flood events. Maximum average velocities (feet per second) Left Right Mile Identification Channel overbank overbank 22.0 Sewage lagoon 6.07 1.73 2.18 l4.9 l!ownstreamof C.B. . Q. RR. IJridgc 6.44 1.99 2.10 63 Upstream of ~in 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 24 "