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Table 1 TR-20 Schematic Information -------------------------------------------------------------- Seo IO " Area eN To Reach Information From To Sq .i "" Length-Ft x m -----------------------------------------~-------------------- 52 222.36 " 13.13 " 131.82 " 11.97 " " 43700 0.18 1.33 " 61.65 " 8.71 " " 15400 0.05 1.33 " 71.63 " 9.77 " " 42000 0.10 1.33 " 81.69 " 10.94 " " 48700 0.18 1.33 " 58.35 " 11.34 " " 36000 0.18 1.33 " " 9500 0.18 1.33 " " 9500 0.18 1.33 " " 16300 0.10 1.33 " " 25200 0.10 1.33 " " 9200 0.18 1.33 " 10 17400 0.18 1.33 " 11 10900 0.18 1.33 -------------------------------------------------------------- 11 " - A major division of flow occurs between Country Road 31 and the Pawnee Ditch crossing. The Pawnee Creek channel at this location has very limited carrying capacity. A portion of channel overflow moves overland in a southeasterly direction for about 2 miles to U.S. Highway 6 at a location southwest of Atwood. The highway and Burlington Northern Railroad redirect the flow northeast through Atwood and on toward the Pawnee Creek highway and railroad bridges. However, about a mile before the flow reaches the main highway bridge, a restricting ridge causes overflow across the highway and railroad towards the nearby South Platte River. The remainder of this flow continues on to the main highway bridge where it combines with flows from the main channel and adjacent flood plain. The main highway and railroad bridges on Pawnee Creek and the overflow bridges about 1000 ft further down the highway to the northeast toward Sterling will not accommodate the lOO-year flow reaching this point. Therefore, some water will continue to the northeast along the highway beyond the bridges towards the Riverside Cemetery. Another segment of out-of-bank flow occurs along the main channel just downstream from County Road 33. This segment of flow moves overland away from the main channel towards the northeast and eventually to the vicinity of the Riverside Cemetery. This flow combines with the residual overflow from the main channel highway and railroad bridges" The consolidation occurs at a location along U.S. Highway 6 near the Riverside Cemetery. It appears additional flood water moves across the highway and railroad at this location with some continuing on past the cemetery towards Sterling. Flows that pd"''' through tho< highway and railn,ad b."ldges on the main stem of Pawnee Creek encounter alluvial fan type topography in the vicinity of a farmstoad immediately below the railroad. A three way division of flow occurs here with about 440 cr", remaining in the channel and the balance going out-of-bank splitting to the northeast and the south. The following table, Figure 2, and Figure 3 show the location and magnitude of flood flows, including their divisions and combining, throughout the study reach. -------------------------------------------------- Location Discharge - cfs 10 yr 25 yr SO yr 100 yr -------------------------------------------------- Highway 14 Gounty il<! '.5 12200 11400 7300 6700 9600 8900 4700 4300 --------------------------------------------------