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<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.
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