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30 TECHNICAL MANUAL Procedure 2.--Computation of flood characteristics of streams in mixed- population flood areas (see pages 43 and 44). 1, Compute basin and cl imatic parameters separately for parts of drain- age area lying in Mountain and lower flood regions, 2. Compute flood characteristics for Mountain Region using regression equations in table 2. 3. Compute flood characteristics for lower region using regression equations in tables 1, 3, or 4. If study site is above 6,500 ft in elevation, (8,000 ft in Arkansas River basin), reduce flood discharges by factor ob- tained from figure 11. 4. From 2 and 3 above, select larger of two flood discharges for each recurrence interval for use as design flood values. 5, As a general rule, select larger depth for each recurrence interval from 2 and 3. At points near the region boundary, an averaging or smoothing process may be required. Appl ication of this procedure is ill~strated in Example 7, Examp I e 7. --Mixed-Popzdat'l:on Plood Area Flood discharges and depths for the jO-, 50-, 100-, and 500-year recur- rence-interval floods are required for TrOublesome Creek at confluence with Bear Creek in Kittredge (lat 39038'45", long 105018'19", SW~ sec. 35, T, 4 S., R. 71 W,), Map coverage: Evergreen and Squaw Pass quadrangles, scale Denver quadrangle, scale = 1 :250,000. 1 : 24,000 Using figure 2 and the topographic maps, Troublesome Creek I ies in the Plains and Mountain Regions. Procedure 2 described above should be used for computing flood characteristics for this site, The equations for flood discharges and depths for the Plains and Mountain Regions are obtained from tables 1 and 2, respectively, The equations require that the following basin parameters be computed: A =drainage area, in square miteS, SB=basin slope, in feet per mile, SS=strea~bed slope, in feet per mile, P =rean annual precipitation, in inches, and R =reductfon factor for site elevation from figure 11. .~.~, ,..n. , '.~~ ,"'_,_~_~~_,__~