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<br />CHAl'ttR V
<br />HYDROLOGIC ANALYSIS
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<br />A. FloodCl1aucteristics
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<br />Flooding along Dry Creek No.1 is most likely to occur du~ing the
<br />May through August period. Major flooding will result from intense thunder-
<br />storms which produce heavy rainfall OVer relatively small areaS. A IOO-year
<br />flood i. "xpeeted to rise to its peak flow within 2 to 3 hours from the most
<br />intense pa~t of the storm and recede within 6 to 8 hours afteT the initial rise.
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<br />The hydrologic analysis required extensive hydraulic computations
<br />to determine peak flo~" at locations ~here the flood water was divided.
<br />Diversion of flows at road crossings, particularly at State Highway 119,
<br />had a significant effect on theoretical peak flows downstream. The
<br />methods used in the hydraulic analysis are explained in the follo~ing
<br />Chapter.
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<br />B. Method of Analysis
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<br />The hydrologic analysis established theS-, 10-, SO-, 100-, and
<br />SOO-year frequency flood discharges along the Dry Creek No.1 study reach.
<br />These discharges ~ere developed based on existing basin development Con-
<br />ditions. The projected flood discharges for the year 2000 ~ere also
<br />predicted for the stream reach downstream from S.H. 119. The future
<br />discharges were based on anticipated densities of development at th~l
<br />time.
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<br />Oischarge - frequency relationships were developed using the Environ-
<br />me"tal Protectio" Agency's "Storm Water Management Model," (SWMM) ~o"'puter
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<br />30
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