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Last modified
1/25/2010 7:06:59 PM
Creation date
10/5/2006 1:49:07 AM
Metadata
Fields
Template:
Floodplain Documents
County
Logan
Community
Sterling
Basin
South Platte
Title
City of Sterling Drainage and Flood Control Implementation Plan
Date
6/1/1997
Prepared For
Sterling
Prepared By
ICON Engineering, Inc.
Floodplain - Doc Type
Floodplain Report/Masterplan
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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 />IV. PAWNEE CREEKlPA WNEE CREEK OVERFLOW <br /> <br />Existing Flooding Conditions <br /> <br />This study includes the reach along Pawnee Creek from its confluence with the South Platte River 100- <br />year floodplain upstream to CR. 29, a distance of about 7.5 miles. Areas of concern include locations <br />where potential floodwaters exceed the existing Pawnee Creek channel capacity and damaged <br />farmlands, county roads, and houses. Also of concern is the Pawnee Creek Overflow where flood <br />water overtops the channel to the north and eventually inundates portions of the City of Sterling. In <br />addition to the Pawnee Creek Overflow, there are areas adjacent to and upstream of CR. 31 where. <br />flows overtop the channel to the south and eventually flow into the Town of Atwood. Improvements <br />for confining split flow areas to the south were not evaluated for this study. <br /> <br />Historically, Pawnee Creek has proven to be the most significant flooding source for the City of <br />Sterling. Flooding in the City of Sterling from Pawnee Creek has occurred mainly as a result of <br />insufficient channel capacity, roadway crossing structures, and the bridges at HWY 6 and the UPRR. <br />A floodplain analysis was completed by the Soil Conservation Service (SCS) in April of 1992 which <br />determined the 100-year floodplain for existing basin and channel conditions. A floodplain map was <br />prepared which delineated the 100-year floodplain for Pawnee Creek through this study reach. Based <br />on the SCS Report, a description of the existing flood potential is presented below: <br /> <br />South Platte River to UPRRIHWY 6 -- Flooding in this reach is limited by the capacity of the existing <br />bridge structures. However, the flooding can be severe and inundate much of the highway and railroad <br />as shown on the photo in Figure 7. This event occurred in 1935 and a similar rainstorm occurred again <br />in 1965. As shown on Sheet I of 4, located in the map pocket in the back of this report, flows split <br />downstream of the UPRR bridge causing a very wide (approximately 4,500 feet), shallow floodplain <br />to the confluence with the South Platte River. Two residences are potentially flooded in this reach: <br />One residence is located in the 100-year floodplain and is on the north bank of Pawnee Creek adjacent <br />to the railroad; and the other residence is located further downstream on a higher plateau which could <br />be impacted by potential shallow flooding. <br /> <br />UPRR/HWY 6 to CR. 35 -- Flooding in this reach is basically caused by: (I) Insufficient capacity of <br />the bridges at HWY 6 and the UPRR; (2) insufficient channel capacity on Pawnee Creek; and (3) <br />storm water draining from the Town of Atwood, which is a result of flow splits from the upper reaches <br />of the basin, The greatest impact of flooding occurs along HWY 6 to the north. Flood flows <br />exceeding the capacity of the bridges travel along HWY 6 damaging farmlands, inundating the <br />Riverside Cemetery, and eventually spreading out to the northwest into the City of Sterling. This area <br />is referred to as the Pawnee Creek Overflow, and is the driving force for the City of Sterling to make <br />flood improvements along Pawnee Creek. <br /> <br />22 <br />
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