FLOOD11630 ‎(2)‎

• County: Statewide
• Basin: Arkansas
• Title: Post Flood Assessment Report - Arkansas River
• Date: 9/15/1999
• Floodplain - Doc Type: Flood Documentation Report

main stem on the south bank. These three rivers are sm~ll perennial streams in t~eir
mountainous headwater reaches, but as they progress through the foc~thills to the rolling plains,
the base flows aze depleted by diversions for urigation. The river channels widen with poorly
defined banks and low flow channels meander through the valleys. i:~e Huerfano River
confluence is at Boone about four miles south of Avondale. The Api.shapa River confluence is
just downstream of Fowler. The Purgatoire River confluence is just south of Las Animas.
Three smaller tributaries are the St. Charles River, Timpas Creek and. Horse Creek. The St.
Chazles River enters the Arkansas River from the south just downstream of Pueblo. Timpas
Creek enters from the south at Swink, about four miles downstream af Rocky Ford. Horse
Creek, enters from the north just upstream of Las Animas. The permeability of the soil and the
absence of well-defined watercourses in these tributary ~vatersheds te:nd to reduce the runoff.
5urface water discharge into the main stem is minor except in cases of extreme precipitation.
Timpas Creek has a drainage area of 496 square miles. Watershed elevations extend from 5,400
feet at the headwaters to 4,120 feet at the stream gage near Swink. Horse Creek has a drainage
area of 1,403 squaze miles. The elevation of the Horse Creek watersh.ed ranges from 6,600 feet
to 4,200 feet. There aze no significant flood control structures on the:ce tributaries. T'he St.
Charles Reservoir is just south of Pueblo, but it is not actually on the St. Charles River.
The State of Colorado has identified flood prone azeas in 267 cities ard towns am~ng all of its 63
counties. There are over 250,000 people living in floodplain azeas of the state. The value of
property, structures, and contents located in identified floodplains is estimated to be over $11
Billion (1996 state estimate). Based on property damaoe data from 1896 to 1984, the average
annual flood losses in Colorado aze estimated to be $17,600,000. Cu~ulative fload losses for the
most damaging floods in Colorado between the turn of the century and 1993 include 331 people
killed and $3.3 Billion (1995 state estimate) worth of properry damage. United St,ates Presidents
have declared a major flood disaster within Colorado in 9 out of the last 32 yeazs between 1965
and 1999 (1965, 1969, 1970, 1973, 1976, 1982, 1984, 1997, and 1999).
FLOOD OF APRIL 29,1999
A lazge regional storm produced heavy rainfall in southeast Colorado and northeast New Me~co
from Thursday Apri129, 1999 through Sunday May 2, 1999. Localized flooding occurred
throughout the region. Numerous roads and bridges were flooded or damaged. Homes were
flooded in Fountain/Manitou Springs beginning on the evening of Apr;.l 29, 1999. The unusually
large volume of runoff produced by the storm resulted in more erosion damage along Fountain
Creek than any previous flood. The Arkansas River began flooding on April 30, 1~99 affecting
homes east of Pueblo near Avondale. The flood reached a new stage of record at Avondale on
May 1, 1999. Between May 1 and 2, 1999 floodwaters sp:read downstream affectirig homes in
Rocky Ford and La Junta. Las Animas was spazed damage to homes. Trinidad Dam on the
Purgatoire River and John Martin Dam on the Arkansas River both rose to new record pool
reservoir elevations. On May 17, 1999, the President signed DR#1276 declaring the ten counties
of Otero, Bent, El Paso; Larimer, Pueblo, Las Animas, Crowley, Kiowa, Elbert, and Freemont in
Chap~`er 1 - Introduction
Post Flood Assessment Report ~ 2 l~rajt Revised Q9I09/99