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<br />Projected Future Conditions
<br />The majority of the drainage area IS currently in Adams County. The
<br />cities of Broomfield, Westminster, and Thomton may choose to annex
<br />portions of this area in the future. Long range plans include con-
<br />struction of both the W-470 and E-470 major highways and have prompted
<br />future land use planning by surrounding jurisdictions. Watershed im-
<br />perviousness under proposed future land use conditions, shown in Figure
<br />111-3, was estimated from Adams County's, Thornton's, and Weld County's
<br />Comprehensive plans; draft land use plans for Broomfield's recently
<br />annexed area; comments received from Westminster's Community Develop~
<br />rnent Department on their growth area; and the North 1-25 Corridor Study
<br />(jointly produced by Westminster and Thornton).
<br />
<br />I1I-9
<br />
<br /> TABLE IlI-4
<br /> PEAK FLOWS AT SELECTED LOCATIONS
<br /> (FUTURE WATERSHED IMPERVIOUSNESS)
<br />Stream Peak Flow (cfs)
<br />Location 10 Year 50 Year 100 Year
<br />Wadley South Mouth 450 1,000 1,275
<br /> UPRR 425 880 1,110
<br /> 144th A venue 375 750 925
<br />Wadley North Mouth 500 1,100 1,400
<br /> UPRR 380 810 1,015
<br /> Colorado Boulevard 160 300 380
<br />Short Run Mouth 475 1,030 1,305
<br /> UPRR 465 930 1,]65
<br />Elms Run Mouth 250 495 610
<br /> UPRR 170 310 380
<br />Morris Creek Mouth 540 1,200 1,530
<br /> UPRR 550 1,160 1,460
<br />Shay Ditch Mouth 980 1,950 2,450
<br /> 1-25 570 ],175 1,470
<br /> Huron Street 445 920 1,145
<br />Mustang Run Mouth 775 1,650 2,100
<br /> Washington Street 740 1,540 1,955
<br /> 1-25 720 ],450 1,800
<br /> Huron Street 360 750 935
<br />Sack Creek Mouth 915 1,850 2,320
<br /> Washington Street 135 230 275
<br /> 1-25 100 165 195
<br />Sack Creek South Confluence 450 920 1,160
<br /> Washington Street 400 775 955
<br />Preble Creek Mouth 3,175 7,020 9,240
<br /> 168th Avenue (East Crossing) 2,390 5,200 6,675
<br /> 168th Avenue (West Crossing) 1,]60 2,400 3,030
<br /> Huron Street 1,145 2,280 2,845
<br /> Zuni 580 1,035 1,250
<br />South Fork
<br />Preble Creek Confluence 820 1,650 2,060
<br /> Highway 7 860 1,630 2,010
<br /> 1-25 525 930 1,140
<br /> I1I-10
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<br />F. FLOOD FREQUENCY AND DISCHARGE
<br />Peak flows resulting from projected future development conditions were
<br />used to define floodplains and tloodways in the study area. The peak
<br />flow discharges at various locations in the study area for the I O~,
<br />50-, and 100-year flood frequencies are summarized in Table I1I-4. The
<br />peak flow profiles for the IO~ and 100-year storms are shown on Figure
<br />III -4 for each of the tributaries.
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