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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />year storm. The existing conditions of Big Dry Creek were modeled by HEC-2 for the <br />2-, 10-, and 100-year events. The plan view of the existing 100-year event is shown on <br />Drawing No.3. <br /> <br />The water surfaces and velocities for the existing conditions are shown in Table III-I. <br />As can be seen in the table, Sections 988+40, 997+15, and 1001+50 have high velocities of <br />11.7,13.2, and 12.2 feet per second (ft/s), respectively, for the 100-year event. Section <br />1002+00 is at the downstream side of 1-25 and has a supercritical velocity of 25 ft/s. <br />The existing loose cobble bed through the 1-25 bridge would probably not withstand the <br />100-year event. <br /> <br />TABLE Ill-I <br />EXISTING CONDITIONS <br />WATER SURFACES AND VELOCITIES* <br /> <br /> WSEL Velocity** <br /> (ft) (ft/s) <br />Section*** 2-year 100-year 2-year 100-year <br />960+30 148.8 150.6 2.7 4.2 <br />962+05 148.9 150.7 3.0 4.6 <br />965+90 149.0 150.8 3.0 4.3 <br />969+50 149.0 150.9 7.6 6.9 <br />976+40 150.7 152.1 4.8 6.9 <br />984+30 152.2 153.8 7.9 9.5 <br />988 +40 153.3 154.9 8.0 11.7 <br />992+60 154.3 156.4 6.3 9.5 <br />997 +15 154.8 157.8 11.3 13.2 <br />1000+45 156.6 159.4 8.2 10.8 <br />1001 +50 157.5 159.8 9.3 12.2 <br />1002 +00 157.6 161.2 8.9 25.0 <br /> (SupercriticaD <br />1003 +09 157.8 168.3 10.1 5.5 <br />1005+64 159.9 168.8 2.7 1.5 <br /> <br />* UDFCD flows only 0,650 cfs for 2-year, and 11,190 cfs for 100-year). <br />** Average channel velocity (channel flow divided by channel area). <br />*** Sections are shown on drawings. <br /> <br />111-5 <br />