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<br />DESCRIPTION OF STUDY ARE~
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<br />At the time this study was initiated, the flow paths were not all
<br />known. As a result of these investigations, it was determined
<br />that a segment of flow will move to the vicinity of Atwood.
<br />Mapping was not done in this area; therefore, specific details of
<br />flow depth, etc. were not made for this segment of tlow.
<br />Another significant segment of flow departs from the channel at a
<br />location just below County Road 33. The tlow moves overland away
<br />trom the main channel towards the northeast and eventually to the
<br />vicinity of the Riverside Cemetery. Water surface prOfiles were
<br />not eomputed for this reach because of the unpredictable
<br />meandering flow pattern through farmland; however, a probable
<br />flow path was sketched on the flood plain maps.
<br />Natural and Beneficial Flood Plain Values
<br />The flood plain_along Pawnee Creek, within the study limits,
<br />generally contalns cottonwoods and willows along the channel,
<br />irrigated cropland adjacent to the channel, and grasslands
<br />interspersed with the cropland. The channel does a considerable
<br />amount of meandering which enhances the visual aesthetics and
<br />wildlife habitat values in the area.
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<br />Basin Characteristics
<br />
<br />Pawnee Creek drains an area of approximately 645 square miles
<br />above U.S. Highway 6 near Atwood, see Fig 1. The basin incluc
<br />areas in Logan as well as Weld Counties. The mouth of Pawnee
<br />Creek is located several miles southwest from Sterling along,
<br />Highway 6 and the Burlington/Union Pacific Railroad tracks. ~
<br />elevation Of Pawnee Creek at this location is about 3980 ft al
<br />sea level. The elevation of the upper end of the basin is nee
<br />5400 ft. The well-known Pawnee Buttes are in the upper reachl
<br />of ,the basin at an elevation of about 5375 ft. I
<br />The major tributaries to Pawnee Creek are Raymer Creek, Southl
<br />Pawnee Creek with its tributary Wildhorse Creek, North pawneej
<br />Creek with its tributary Igo Creek, Cottonwood Creek, Horseta
<br />Creek, and Spring Creek. These streams are basically intermit
<br />with some accumulations of live water, particularly in south
<br />Pawnee Creek.
<br />
<br />The soils in the basin are predomin~ntly loams and cl~y lo~ms
<br />with sandstone, shale, and siltstone outcroppings. They fit
<br />primarily in hydrologic groups "C" and "B". Hydrologic curve'
<br />numbers are in the range of 77 to 79 with the primary vegetat1
<br />being native range with some winter wheat and a significant ;
<br />amount of irrigated cropland in the lower part of the basin. !
<br />The mean annual precipitation for the basin ranges from 14 t01
<br />inches. The mean annual precipitation for Sterling, nearest -I
<br />with weather data, is 14.96 inChes with a mean annual tempera-j
<br />of 48.5 degrees Fahrenheit. I
<br />StudY Limits
<br />The area of interest in thlS study includes locatlons where f
<br />waters from Pawnee creek damage farm lands and county roads aj
<br />the lower reaches of the basin. Also of concern is Pawnee Cr,
<br />overflow whiCh inundates portions of the city of Sterling. I
<br />Since this basin is so large, the study limit was confined to
<br />lower reach from County Road 29 to u.S. Highway 6. The totall
<br />study length is about 7.6 miles which includes the main stem
<br />Pawnee Creek and the overflow area between Pawnee Creek and t
<br />Riverside Cemetery along U.S. Highway 6. A number of out-of-
<br />conditions occur with segments of flood waters departing over
<br />away from the main channel. It was attempted herein to track
<br />these floodwaters to locations where they combine again and p
<br />a flood threat to the Town of Sterling.
<br />
<br />The flood plain supports a variety of wildlife species such as:
<br />cottontail, squirrel, prairie rattlesnake and a variety of birds
<br />including the burrowing owl, Swainson's hawk, prairie falcon,
<br />meadowlark, horned lark, lark bunting, and pheasant. Notable
<br />predators inclUde the great horned owl, bald and golden eagle,
<br />coyote, kit fox, badger, and skunk. White-tailed and mule deer
<br />and antelope are common to the area.
<br />In the fall and spring, multitudes of migratory birds pass over
<br />LOgan county_
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