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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 />.' <br />I <br />. <br />I <br />I <br />I <br />I <br />I <br /> <br />10 <br /> <br />Flooded Areas and Flood Damages <br /> <br />U.S. 85 as well as the Union Pacific Railroad and the Fulton <br /> <br /> <br />Ditch. These facilities provide limited flood conveyance capacity <br /> <br /> <br />and thus give rise to spreading of flood runoff across the flat <br /> <br /> <br />terrain and diversion of waters into the Third Creek drainage <br /> <br /> <br />area. The resulting shallow flooding encompasses agricultural <br /> <br /> <br />land as well as two farms on East 132nd Avenue near Tucson Street. <br /> <br /> <br />The new diversion structure on the Fulton Ditch at Second Creek <br /> <br /> <br />does not provide sufficient capacity to pass the future 100-year <br /> <br /> <br />flood event across the ditch. Through this reach, approximately <br /> <br /> <br />60 percent of the flood peak is diverted north to Third Creek. <br /> <br />The 100-year flood plain limits and water surface profiles are <br /> <br /> <br />shown on the attached Flood Hazard Area Delineation Maps. The <br /> <br /> <br />computed 100-year flood elevations at each reference point are <br /> <br /> <br />tabulated in Tables 5 and 6 for both of the streams. A <br /> <br /> <br />description of the extent of flooding is discussed in the <br /> <br /> <br />following paragraphs. <br /> <br />Second Creek - The flood plain limits and flood profiles for <br />Second Creek are shown on the Flood Hazard Area Delineation <br />Maps, Drawings SCP-l through SCp-5 and SC-l through SC-34. In <br />the lower reaches of the study, the flood profile drawings have <br />been separated from the flood maps to provide better coverage <br />of the wide flood plains. <br /> <br />Upstream of Tucson Street in the reach extending to 1-76, <br />Drawings SC-6 to SC-IO, the flood plain is more confined by <br />natural ground contours. The lOO-year flood plain encompasses <br />almost totally agricultural land in addition to some farm' <br />buildings near Tucson Street. During the 100-year flood event, <br />124th Avenue, Potomac Street, and 120th Street will be overtopped. <br /> <br />In the flood plain reach from the South Platte River to U.S. 85, <br />Drawings SC-l to SC-3, the flood plain encompasses agricultural <br />land. Some farm buildings in this reach adjoin the flood plain <br />fringe. The Henderson-Brighton Road would be overtopped under <br />the potential 100-year storm event. The Second Creek flood plain <br />becomes a part of the South Platte River flood plain approximately <br />1,500 feet downstream of the Henderson-Brighton Road, although <br />little trace of a flow channel exists in this area. <br /> <br />The flood plain from 1-76 to Chambers Road, Drawings SC-IO to <br /> <br /> <br />SC-14, inundates farm land but is obstructed by 1-76, the <br /> <br /> <br />Burlington Northern Railroad, the Burlington Ditch, and the <br /> <br /> <br />O'Brian Canal. Flood waters will overtop the interstate high- <br /> <br /> <br />way and divert water east along the highway beneath the 4th <br /> <br /> <br />Avenue overpass. The Burlington Northern Railroad crossing <br /> <br /> <br />structure will pass the flood flow with excess capacity. Both <br /> <br /> <br />the Burlington Ditch and O'Brian Canal will intercept flood <br /> <br /> <br />flows and divert the water along the irrigation ditches. This <br /> <br />The reach from U.S. 85 to Tucson Street, Drawings SC-3 to SC-6, <br /> <br /> <br />encompasses the primary problem areas on Second Creek. The flood <br /> <br /> <br />plain obstructions through this part of the flood plain include <br />