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<br />I. INTRODUCTION <br /> <br />Summary <br />On the morning of July 30, 1997 the CWCB was advised by Logan County residents that an <br />intense rainstorm had occurred over the Pawnee Creek watershed on July 29, 1997. The <br />resulting flood flow elevations in Pawnee Creek were reported to be "higher than the flood of <br />1965." State and local officials were immediately concerned for the life and safety of residents, <br />motorists, and visitors in the Pawnee Creek floodplain downstream of the rainstorm area, In <br />particular, the communities of Atwood and Sterling, Colorado were in the direct path of flood <br />flows or flood overllows from Pawnee Creek. This memo summarizes the key elements of the <br />flood event of 1997. <br /> <br />Purpose, <br />The purpose of this report is to document the flooding of July 29-31, 1997 in the Pawnee Creek <br />watershed. The documentation will provide area residents, others affi~cted by the flooding, and <br />agencies and entities involved in post-flood study and mitigation with basic information about the <br />flooding and its impacts. In addition, the report will contribute to preliminary decisions about flood <br />hazard mitigation. <br /> <br />II. STUDY AREA DESCRIPTION <br /> <br />Community Description <br />The study area for this report includes portions of Logan and Weld Counties, which are located <br />in northeastern Colorado. In addition to the unincorporated county areas, affected communities <br />include Sterling and Atwood. The City of Sterling, the county seat of Logan County, is located <br />approximately 125 miles northeast of Denver. Sterling is the largest community in Logan <br />County, and has a population of about 11,000 (1995 estimate), The total population within <br />Logan County is about 19,000 (1995 estimate). <br /> <br />Watershed Description <br />Pawnee Creek is a left bank tributary to the South Platte River and drains an area of about 700 <br />square miles. The watershed is located in extreme northeast Colorado mainly within Logan <br />County and Morgan County. The mouth of the creek is located about 5 miles southwest of <br />Sterling and about 1 mile northeast of Atwood in Logan County. The watershed elevation ranges <br />from about 3,980 feet to 5,400 feet. The soils in the basin are mostly loarns and clay loarns, with <br />sandstone, shale, and siltstone outcroppings. Land use consists of open range land and a <br />significant amount of irrigated cropland in we lower part of the basin. The mean annual <br />precipitation for the basin ranges from 14 to 16 inches. <br /> <br />Although Pawnee Creek itself is not located in or adjacent to Sterling, the U.S. Highway 6 and <br />the BurlingtonlUnion Pacific Railroad embankments are major obstmctions which divert flow <br />from the main channel toward the northeast. Figure 1 presents a vicinity map of the Atwood and <br />Sterling area. <br /> <br />I <br />