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<br />In the late 1800s, coal m1n1ng led to the development of Erie and <br />several other small communities along the banks of Coal Creek. <br />Because the coal reserves have diminished and most of the mines <br />have been shut down, Erie is now mostly commercial and residential, <br />with some agricultural development in the surrounding area <br />(Reference 1). The estimated population of Erie was 1,231 in 1980 <br />(Reference 2). <br /> <br />The average annual precipitation in Erie is 12.1 inches, and the <br />normal mean temperature is 48.60F. In 1976, the temperature varied <br />from a July average of 11.60F to a January average of 26.80F <br />(Reference 3). <br /> <br />Vegetation in the area consists primarily of native grass. The <br />soils in the area are shallow, very gravelly and stoney, and in the <br />rock outcrop-Juget-Baller Association (Reference 1). <br /> <br />The topography in the developed part of Erie is relatively flat and <br />gradually slopes toward Coal Creek. Both residential and <br />commercial development exist in the floodplain area. <br /> <br />Coal Creek flows northerly along Erie I s eastern corporate limits <br />and empties into Boulder Creek. <br /> <br />Coal Creek West Line Overflow begins where floodwaters from Coal <br />Creek overtop the Union Pacific Railroad south of Erie and flow <br />northerly independent of Coal Creek, through the fully developed <br />area of Erie, returning to Coal Creek north of the town. <br /> <br />2.3 Principal Flood Problems <br /> <br />The main sources of flooding on Coal Creek are heavy thunderstorms <br />in spring and summer. Flooding can become especially severe when <br />these thunderstorms follow either rapid snowmelt or prolonged rainy <br />weather (Reference 1). <br /> <br />Floods have occurred 1n 1876, in 1891, in June 1896, on <br />June 3, 1921, on May 26, 1935, on September 2, 1938, on <br />June 9, 1949, on May 9, 1957, and in May 1969. The estimated <br />discharges for these events at Erie are shown below (Reference 1). <br /> <br />Date of Flood <br /> <br />Discharge at Erie <br />(Cubic Feet per Second) <br /> <br />Approximate <br />FreCluencv <br /> <br />1816 <br />June 3, 1921 <br />September 2, 1938 <br /> <br />13,200 <br />1,800 <br />3,500 <br /> <br />100-Year <br />20-Year <br />5-Year <br /> <br />Amount of damage from these floods is unknown. Flood discharges <br />were estimated by the COE using the slope-area method. <br /> <br />The 1876 flood is the maximum flood of record at Erie. <br />recent flood occurred in May 1969. <br /> <br />The most <br /> <br />4 <br />