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<br />ern and southern portions of the county, cross the county in a <br />northwest-southeast direction. The remaining northeastern part of <br />the county is composed of rolling hills, which taper off to what <br />might be called the far western edge of the Great Plain area to <br />the east. Elevations within the couni:y vary from approximately <br />5,000 feet 1n the northeast to over 10,000 feet in the southwest. <br /> <br />Jefferson County lies within the South Platte River drainage <br />basin. The major streams originate in the mountains in the west <br />and flow generally to the east toward the South Platte River, <br />which forms the southeast border of the county. <br /> <br />East of the foothills, the climace is concinental. The general <br />feacures are low relaCive humidity; an extensive amounC of <br />sunshine; lighC rainfall, confined largely Co the warmer half of <br />che year; moderately high wind movement:; a large daily range in <br />Cemperature; high day cemperacure in summer; and generally, in che <br />w1ncer, a few protracted cold spells. <br /> <br />The average yearly rainfall is 14.59 inches. <br />ature in July 1S approximately 75*F, whereas <br />(Reference 4). <br /> <br />The average temper- <br />in January it is 30*F <br /> <br />2.3 Principal Flood Problems <br /> <br />Past flooding along most of the streams in che county is not well <br />documented. On many of the small ungaged streams there are no <br />available data regarding flood magnitude or damage. There are <br />some records available for the larger streams in and near <br />Jefferson County, and it is reasonable to assume that floods <br />occurred simultaneously on the smaller streams as well <br />(References 5-8). Such records that do exist include: <br /> <br />Bear Creek Flooding occurred along the creek in 1876, <br />1894, 1896, 1957, 1965, and 1969. The 1896 flood was the largest <br />exper1.enced. Twenty-seven lives were lost., and severe property <br />damage was reported from Evergreen to the mouth. The discharge at <br />the Morrison gaging stat10n was 8,600 cubic feet per second (cfs) <br />( Re ference 9). <br /> <br />Clear Creek Past floods on Clear Creek have been 1nfrequent and <br />more severe in the upper reaches (Reference 10). ll.ajor flooding <br />occurred in Golden in 1888 (8,700 cfs) and 1956 (5,250 cfs), and <br />in Derby in 1965 (5,070 cfs). <br /> <br />South Platte River - Large floods were reported in 1844, 1864, <br />1867, 1876, 1894, 1921, 1933, 1942, 1965, and 1973. The largest <br />and mos t dsmaging of these occurred June 16 and 17, 1965, when a <br />discharge of 40,300 cfs was computed at U.S. Geological Survey <br /> <br />6 <br />