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<br />developments appear to be many years from actual construction. All earthwork <br />was performed in accordance wi th FEMA guidelines and was accomplished in order <br />to produce a na rrower lOO-yea r f loodp lai d.. Compac tion tE!S ts for the ea rthwork <br />are included in the Appendix. In addltion, all disturbed areas are being <br />protected by appropriate erosion control methods. <br /> <br />LOCATION AND DESCRIPTION OF STUDY AREA <br /> <br />The study reach for Cherry Creek through the lliver Run sI te is located In Sec- <br />tions 29 and 32, Township 5 South, Range 66 W"st of the Sixth Principal Neri- <br />dian in the County of Arapahoe, State of Colorado (see Vicinity Map, Figure 1, <br />Appendix). This reach of Cherry Creek has an average channel width of 50 to <br />250 feet and ranges from 2 to 10 feet Jeep. The channel bed has an average <br />slope of 21 feet per mile (0.4%). The channel. is alluvial, flat bottomed and <br />follows a meandering course. <br /> <br />Happy Canyon Creek, a major tributary to Cherry Creek, enters the main channel <br />approximately half way through the study area. <br /> <br />Historically, the principal cause of flooding within the Cherry Creek drainage <br />basin has been intense thunderstorms during the late spring and early summer <br />months. Runoff from melting snow doe,; not contribute to a major flooding <br />problem due to the low altitude. During the period from Nay to August, warm <br />moist air from the Gulf of Mexico combines with cool dry air along eastern <br />plains causing a deflection upward where the unstable air is cooled and pre- <br />cipitates over the front range. These ~;torms are charac,terized by high rain- <br />fall intensities of short duration which produce high pe,ak flows and moderate <br />volumes of water. The largest flood events occur when severe thunderstorms <br />occur on land areas previously saturated by h"avy rains. <br /> <br />The history of flooding along Cherry Creek dates back to Indian accounts of <br />debris left by the falling waters in the top of cottolllJOods on the banks of <br />the ha rmless looking gu lly. The ea rl ies t recorded even t occu rred on ~lay <br />19-20, 1984, five years after Denver was settled. ether m"jor events have <br />occurred in May l876, May 1878, July 1835, July 19l2, July 1922, August 1933, <br />July 1946, and June 1965 (References 3 and 4). <br /> <br />The June, 1965 flood is the largest flood to have occurred in the Cherry Creek <br />b"sin this century. On June l6, 1965, a major storm centered over the Plum <br />Creek and Cherry Creek basins produced l:ainfa 11 amounts of up to 10 inches in <br />a 3-hour period. The recorded flows along the upper Cherry Creek basin in- <br />cl.uded l,OOO cfs upstream of Franktown, 39,000 cfs near Melvin and 58,000 cfs <br />at Cherry Creek Dam. The heavy runoff caused major flooding along the main <br />stem of Cherry Creek from the vicinity of Franktown to Cherry Creek Reser- <br />voir. About 2,720 acres was reportedly flooded. Most of the bridges across <br />Cherry Creek we re damaged or des troye,j. F'lood damag,;g to ta led $l, 306,000 <br />(Reference 4). <br /> <br />No major flood protection structures exist upstream of the study area in the <br />Cherry Creek basin. The Soil Conservation Service has completed constructions <br />of 32 floodwater retarding structures a., part of the IOF:ranktown-Parker Tribu- <br />ta ries of Cherry Creek Wa tershed" and "",Jes t Cherry Creek Wa tershed" projec ts. <br /> <br />- 2 - <br />