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peak discharge of 50,000 c.f.s. Combining the flow from Chico Creek, the esti~ated peak on the
<br />Arkansas River at the town of Avondale was 102,000 c.f.s. The flooding inundated nearly
<br />165,000 acres of land; excluding the upland tributary areas that are used mostly for grazing and
<br />some dryland farming. The rainfall was so intense in these latter azeas that the entire countryside
<br />became a moving lake, farms were badly eroded, and bottomlands ~n~ere covered with deposits of
<br />silt and sand up to 6 feet in depth. The cities of Pueblo and La Junta were severely damaged, but
<br />an early flood warning and a well-organized flood fight prevented major damage at Las Animas.
<br />The peak discharge diminished downstream, yet produced a flood of record at the Catlin Dam
<br />gauge near Fowler with a peak discharge of 43,200 c.f.s. on June 18, 1965. The next day a peak
<br />discharge of 33,000 c.f.s. was recorded at La Junta and 22,100 c.f s. at Las AniIIias. Agricultural
<br />damages were extensive; transportation facilities, power, telephone, and natural gas utilities were
<br />damaged throughout the subbasin; and four lives were lost. Damages were estimated at neazly
<br />$18 million in the subbasin. That year it was also estimated that the John Martin Dam and
<br />Reservoir Project prevented downstream damages of more than $48 million.
<br />August 1965 & 1966: In August 1965 and again in August 1966, storms over the upper
<br />Arkansas River watershed caused severe urban and a~ricultural damages from floodflows on the
<br />main stem and many of the small tributaries in the reach above Pueblo. The city of Pueblo,
<br />although situated on the banks of the Arkansas River, is relatively free from floods on the main
<br />stem because of existing flood control improvements. Nevertheless, portions of ~tl~e city are
<br />vulnerable to flooding from tributaries that enter from the north.
<br />Flood of July 1997
<br />During late 3uly and early August of 1997, 13 counties in Colorado (Baca, Clear Creek, Crowley,
<br />Elbert, Kiowa, Larimer, Lincoln, Logan, Morgan, Otero, Phillips, Prowers, and Weld)
<br />experienced intense rainfall and flooding. The heavy zain, flash flooding, mudslides, landslides,
<br />and severe ground saturation warranted a declaration of a federal disaster area far these counties.
<br />Crowley, Kiowa, Otero, and Prowers counties have drainage tributaries to the Arkansas River,
<br />while portions of Baca, Elbert, and Lincoln counties aze within the Arkansas River Basin. In Iate
<br />July 1997, tropical moisture entered Colorado from the south while a large high-pressure system
<br />stalled over the central plai.ns. The clockwise rotation of the system supplied moi•e moisture to
<br />the state from the east. A cold front associated with the high-pressure system over the plains set
<br />off thunderstorms and subsequent flooding as ihe moist air masses converged over the state.
<br />On the evening of July 28, 1997 four extreme centers of precipitation occurred over eastem
<br />Colorado; Fort Collins in Larimer County, northwest of Hudson in Weld County, Elbert/Lincoln
<br />County, and rural Bent County. The centers over Elbert, Lincoln and Bent counties caused flood
<br />damages in Manzanola, Fowler, Rocky Ford, Swink, La Junta, and Las Animas. Damage and
<br />flooding was primarily 1'united to roads and bridges. The drainages that flooded in Otero County
<br />in 1997 historically had not experienced flash flooding during the surnmer months. Horse Creek
<br />entering the Arkansas River from the north just upstream from Las Animas with a drainage azea
<br />of 1,403 square miles produced an instantaneous peak discharge at the Horse Creek gage of
<br />2,236 c.f.s. This flow was over twice the previously recorded maximum discharge; of 1,030 c.f.s.
<br />Chapter 2- History of Flooding and Flood' Protection
<br />Post Flood Assessment Reporf ~ 8 Draft Revised o9/ov/99
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