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<br /> <br />.. <br /> <br />, <br /> <br />.. <br />.. <br />'... <br /> <br />. <br />\-. <br />~t <br /> <br />,." <br /> <br />n <br /> <br />1 <br /> <br />r <br /> <br />f" <br />1 <br /> <br />... <br />, <br /> <br />.---._------~-'-~_._.-- <br /> <br />IV. PAW1'o"EE CREEKlPA\VN'EE CREEK OVERFLOW <br /> <br />Existing Flooding Conditions <br /> <br />This smdy includes the reach along Pa1-\nee Creek from its confluence 1-\ith the South Platle River 100, <br />year floodplain upstream to CR. 29, a distance of about 7,5 miles, Areas of cor:cem include locations <br />where potential floodwaters exceed the existing Pawnee Creek channel capacity and damaged <br />fannlands, county roads, and houses, ,-'l.iso of concern is the Pav-mee Creek Chernow where flood <br />water overtops the channel to the ;10rth 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 spJit flow areas to the south were not evaluated for this smdy, <br /> <br />Historically, Pawnee Creek has proven to be the most significant nooding source for the City of <br />Sterling, Flooding in the City of Sterling from Pawnee Creek has occ:.uTed rr:ain1y as a result of <br />insufficient channel capacity, roadway crossing strucnrres, and the bridges at HWY 6 and the L'PRR, <br />A floodplain analysis was completed by the Soil Conservation Service (SCS) in April of J992 which <br />de:ermined the IOO-year 1100dplain for exisring basin ,lOd channel conditions, A floodpiain map was <br />prepared which delineated the IOO-year floodplain for Pawnee Creek through this ,mdy reach. Based <br />on the SCS Report, a description of the existing flood potemial is presented below: <br /> <br />SOUlh Plane River to l;PRRiHIVY 6 ,- Flooding in this reach is limited by ,he capacity, of the existing <br />bridge srrucrures, However. the flooding can be severe and inundate much of the highway and railroad <br />:lS shov,T1 on the photo in Figure /, This event occW7ed in 1935 and a similar rainstorm occurred again <br />in 1965, As sho1-\ll on Sheet 1 of 4, located in the map pocket in the back of this report. flows split <br />do\\nstrearn of the UPRR bridge causing a very wide (approximately 4,500 feet), shallow floodpiain <br />to the contluence with the South Platte River, Two resjdenc~s are potemiaily flooded in this reach: <br />One res; :~flce is located in the ] OO,year floodplain and is on the florth bank of Pav,nee Creek adjaceflt <br />to the railroad: and the other residence is locmed further d01-\nstrearn on a higher plateau which could <br />be impacted by potential shallow flooding, <br /> <br />C:PRR/HV';'," 6 to CR, 35 ,- Flooding in this reach is basically caused by: Ii) Insufficient capacity, of <br />the briGges at HWY 6 and the DPRR: (::) insufficient channei capacity on ?awnee- Creek: and (3) <br />stormwmer draining from the Town of Atwood. which is a result of flow spiirs from the uppe, reaches <br />of the basin, The greatest impact of flooding occurs along HW1' 6 to the north, Fiood flows <br />exceeding the capacity of the bridges travel along HWY 6 damaging farmlands. inundating the <br />Riveside Cemetery, and eventually spreading out to the northwest into the City of SterLing, T:~is area <br />is referred to as the Pawnee Creek Overflow. and is the driving force for the City of Sterling to make <br />flood im~rovements along Pawnee Creek. <br /> <br />2:: <br />