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<br />Colorado Flood Hazard Mitigation Plan -1999
<br />
<br />trast, annual precipttation on
<br />the plains east of Denver,
<br />Colorado, and in the South
<br />Park area in the southwest
<br />part of the basin, ranges from
<br />5 to 7 inches, Most of the pre-
<br />cipitation on the plains occurs
<br />as rain, which falls between
<br />Aprii and September,
<br />
<br />Rangeland is present across
<br />all areas of the basin except
<br />over the high mountain for-
<br />ests, Agricuttural land is re-
<br />stricted mostly to the plains,
<br />Urban or built-up land is pre-
<br />sent primarily along the Front
<br />Range urban corridor in Colo-
<br />rado,
<br />
<br />1999 Flood Event Greatest Impact Areas Fig. 2.5
<br />
<br />La Junta
<br />Otero County
<br />. Weather reports indicated
<br />that eight inches of rain
<br />occurred over a three-day
<br />period.
<br />. The Arkansas River broke
<br />the dikes near North La
<br />Junta, flooding 200 resi-
<br />dences and businesses.
<br />
<br />EI Paso and
<br />Pueblo Counties
<br />. The flooding that occurred
<br />along Fountain Creek and
<br />the Arkansas River was
<br />significant and will be con-
<br />sidered the worst flooding
<br />event since 1965.
<br />
<br />The Storm Affected these Additional Areas
<br />Bent, Crowley, Custer, Elbert, Fremont, Kiowa, Las Animas,
<br />otero, and Weld counties.
<br />
<br />Phillips County and parts of
<br />Lincoln and Elbert Counties
<br />have drainage tributaries to
<br />the Republican River, The
<br />Republican River is, in turn, a
<br />tributary to the Kansas River
<br />in Kansas, The Republican
<br />River Basin in Colorado consists primarily of rangeland
<br />with some farming and ranching communtties scat-
<br />tered throughout the basin,
<br />
<br />The Arkansas River Basin is very similar to the South
<br />Platte River Basin in topography, geology, and hydrol-
<br />ogy, Annual mean temperatures are slightly higher
<br />than the Platte River Basin, Annual rainfall amounts
<br />average between 7 and 15 inches, except in the moun-
<br />tainous areas of the Basin, Land use is similar as well
<br />and consists mainly of agricutture,
<br />
<br />Crowley, Kiowa, otero, and Prowers counties are
<br />drainage tributaries to the Arkansas River, In addttion,
<br />portions of Elbert, Lincoln, and Baca counties are
<br />within the Arkansas River Basin,
<br />
<br />A very small part of the incident area lies wtthin the
<br />Cimmaron River Basin, The southern portion of Baca
<br />County has drainage tributaries to the Cimmaron
<br />River. The Cimmaron River fiows from Colorado into
<br />Kansas and then into Oklahoma where tt ultimately
<br />joins the Arkansas River in Tulsa. The Cimmaron River
<br />Basin is similar in topography and climate to the Ar-
<br />kansas River Basin.
<br />
<br />1999 - Flood Event Description - The three-day rain-
<br />fall event occurred on April 29-May 1, 1999, Heavy
<br />rain and saturated soil caused flooding in two major
<br />areas along the Front Range: Northeastern Colorado
<br />along the South Platte River and some of its tributar-
<br />
<br />ies; and Southeastern Colorado along the Arkansas
<br />River and some its tributaries,
<br />
<br />Rainfall totals of up to 13 inches were recorded in the
<br />Cheyenne Mountain region of Colorado Springs, The
<br />La Junta region recorded approximately 8 inches over
<br />the same three-day period The Arkansas River broke
<br />the dikes near North La Junta, flooding approximately
<br />200 residence and businesses, The stormwater runoff
<br />from the three-day general rain resulted in large flood
<br />inundation and erosion in the Arkansas River and
<br />Fountain Creek watersheds,
<br />
<br />These rainfall totals are large, but not extreme in com-
<br />parison to the largest storms experienced in Colorado.
<br />What made this storm so interesting (and the flood
<br />flows so large) was the fact that rainfall was so wide-
<br />spread that most of the affected basins were receiving
<br />heavy rainfall basinwide, This is not the "norm" for
<br />Colorado, Also, rain on snow is generally not a great
<br />problem in Colorado, but sizeable areas of the Front
<br />Range foothills did receive heavy rain on top of several
<br />inches of saturated snowpack, The mett rate of this
<br />snowpack was low, but additional water was added to
<br />the runoff,
<br />
<br />The flooding that occurred along Fountain Creek and
<br />the Arkansas River was significant and will likely be
<br />considered the worst fiooding event since 1965, How-
<br />ever, the storm affected Bent, Crowiey, Custer, Elbert,
<br />EI Paso, Fremont, Kiowa, Larimer, Las Animas, otero,
<br />
<br />Chapter 2 - 6
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<br />12/2319910,00 PM
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