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<br />DESCRIPTION OF THE RAINFALL AND FLOOD EVENTS e
<br />Rain began falling on April 28, 1999 over many areas of the state, and continued intermittently
<br />through May 2. Heavy rain on saturated soils caused flooding in two major geographic areas:
<br />Northeastern Colorado along several tributaries to the South Platte River, and southeastern
<br />Colorado along the Arkansas River, Fountain Creek, and some of their tributaries. Initially, 5
<br />counties received a Presidential Disaster Declaration as a result of significant flood, erosion, and
<br />mudslide damage. Seven additional counties were added to the list shortly following the
<br />disaster. The 12 declared counties were listed in the section above.
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<br />Meteorological conditions in Colorado beginning on April 28 were for ideal for creating a flood
<br />disaster. A large amount of moisture was being funneled into the state from the Gulf of Mexico;
<br />heavy general rains resulted over a several day period. As much as 12 to 14 inches ofrain fell in
<br />the heart of Colorado Springs over the storm period. Many other areas reported storm totals of at
<br />least several inches.
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<br />The worst flood damage in the state occurred in unincorporated Otero County, specifically in the
<br />community of North La Junta. Floodwaters from Fountain Creek and other tributaries caused the
<br />Arkansas River to peak at nearly 22,400 cfs near La Junta, A levee along the Arkansas River
<br />broke through or was overtopped in several places, allowing a large volume of water to engulf
<br />the small community of North La Junta. Approximately 250 homes and businesses were
<br />flooded, and numerous other damages were sustained on agricultural lands, irrigation facilities,
<br />and public infrastructure. Amazingly, the flood event was only considered to have a frequency
<br />of approximately a 10-year flood event. For comparison, the June 1921 flood event on the
<br />Arkansas River had a discharge of 200,000 cfs - many, many times greater than the 1999 event. ..
<br />The Board's lOO-year flood discharge at La Junta, Colorado is 92,000 cfs. Currently, a housing -
<br />buy-out program has been implemented by a cooperative multi-agency effort, and other
<br />mitigation strategies have been requested or planned by the County.
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<br />The monsoon season started on July 5, 1999, which came early, compared to Colorado's average
<br />beginning date of July 12, Rains throughout much of the state have occurred on an almost daily
<br />basis through September 3rd, which resulted in the state having an extremely high antecedent
<br />moisture condition - See map no. 2. This has been one of the longest and wettest monsoonal
<br />seasons on record. Colorado experienced one of its highest relative humidity readings for the
<br />monsoon season on record. These high relative humidity readings and moderate temperatures
<br />were the reason for the daily/weekly rains during the summer. The heavy rainfall resulted in
<br />statewide flooding, landslides, rockfalls, debris flows, and crop damage. In 1999, the state
<br />experienced a number of heavy rainfalls at high mountain elevations - See map no. 3 and table
<br />no 2.
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<br /> TABLE NO. 2
<br />Cre,ek Date of RainfaU Rate Divide Rain Shadow
<br /> Rain/Flood Upper Elevation
<br />Dallas Creek near July 31, 1999 3 inches in 3 hours 9,000 ft 9,000 ft.
<br />Ridgeway
<br />Clear Creek @ July 28, 1999 3 inches/hour 13,574ft, 12,000 ft.
<br />Bakersville
<br />Saguache Creek July 26, 1999 7.5 inches in 1.5 11,719 ft, 11,000 ft.
<br />~of Saguache hours
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