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<br />cD <br /> <br />· The width of flow down the ditch along 1-25 containing the Soxelder overflow that <br />comes in south of Vine was delineated by Mannin~i's 'n' calculations and not by <br />HEC-2 modelling. <br /> <br />· Flow from Cooper Slough spreads out at the railrolld and overtops the railroad at <br />several places. Ir addition to the Cooper Slough flow, !two inflows from Soxelder <br />Creek pond at, a~d eventually overtop, the railroad. One flow originates just <br />south of Vine and travels south along the frontage road to the railroad. The other <br />flow comes under 1-25 at the railroad, These overfll:lWS are not contained by the <br />low area just north of the railroad but overtelp the rctilmad, Field inspection of the <br />railroad indicates that the railroad does have a low point, but the almost level <br />grade would allow the Soxelder overflows teJ sheetfjow elver most of the railroad <br />between the frontclge road and where the CeJoper Slough overtops the railroad. <br /> <br />· Previous mapping presented had shown an island area south of the railroad <br />tracks along the eiastern edge. However, based on the field ins pectic," indicating <br />sheetflow over most of the railroad, it was decided to cclnsider this entire area as <br />shallow flooding. There are several areas where small islands may be present <br />but the areas considered islands would be too small to develop and were <br />therefore not defined. <br /> <br />· At sections E, F and G the Cooper Slough elvertops its bank and flow is lost to <br />the east. This overtopped flow spreads out and joins with the Soxelder Creek <br />railroad overtoppi~g waters. The split flow does not retLlm to the 100-year <br />floodplain until section C. <br /> <br />· Culverts at Highway 14 are assumed 25 percent blocked based on fiE~ld <br />inspection. <br /> <br />· Locations and amounts of overflow at Highway 14 wem detemlined by <br />considering State Highway 14 as a weir and rating the flow through the culverts. <br /> <br />'I Just west of the Celoper Slough, Highway 14 is overtopped in the 500-year event <br />only. Otherwise flow either goes through the culverts or overtops Highway 14 at <br />the easternmost side of the Highway by 1-25. <br /> <br />41 A 100-year SoxeldH Creek overflow of 300 cts crosses 1-25 at Highway 14. <br />Highway 14 is significantly higher in elevation than the land just north, thus a <br />large area of back"vater is created. This backwater joins with the split flow and <br />railroad overtoppinlls to create one continuous zone of shallow flooding from the <br />railroad to Highway 14. <br /> <br />" The floodway south of the railroad has been confined to the main channel <br />because the zone crt shallow flooding has nel defined flow path. <br />