FLOOD02324 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I channel with the Union Pacific railroad embankment immediately to the east of the channel and a narrow wedge of undeveloped land between the channel and Steele Street an the west. The Sauth Platte River backs up this channel during flood stage; therefore, any channel improvement to handle the Niver Creek flows is unwarranted. A de- tailed determination of the coincidence of Niver Creek and South Platte River floods along with the resulting backwater effect of the South Platte flood flows on the Steele Street culverts is beyond the scope of this study. From the limited data available, however, it appears that a 50-year flood on the South Platte River, wi II not affect the Steele Street culverts while l00-year flood flows will have a minor effect. Niver Creek flows greater than the 50-year flood flow will overtop Steele Street; therefore, a more detailed study is unnecessary. Steele Street to York Street - Plates 111-3 and 111-4 Channel Design The existing channel in this reoch is within the right-of-way owned by Adams County. The sail in the area consists of a 5 to a foot strata of sandy clay (Cl) underlain by fine grained sand (SM). The channel in this reach has been relocated from its historic path at some time in the past resulting in an increased gradient. The channel at present is unlined, steep-banked, essentially straight and has a drop of approximately 31 feet in 2,300 feet, or 14 percent. This reach was badly damaged during the Way 5, 1973 flood (approximately a-year frequency flood). The Colorado Agri- cultural Ditch siphon crossing and four drop structures were washed out and extensive damage to the channel banks and invert occurred during that storm. The damage appears to be the beginning of meander patterns which could result in encroachment on the present right-of-way limits and COJld threaten the York Street bridge foundations if unchecked. 111-2