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<br />TABLE 1 . DRAINAGE AREAS
<br />
<br />Area ~S1. mi.)
<br />1, 10
<br />11,090
<br />10,900
<br />496
<br />
<br />floods also occured in 1921, 1923, 1936, 1942, 1955 and 1965; see
<br />Table 2 for peak discharges and dates (Reference 9).
<br />Information on the eat"lier histot"ical floods that have occut"red
<br />in the study area is very limited because streamflow t"ecords were
<br />not being: made pt"iot" to 1894, eye.witness accounts are not
<br />available, and contemporary t"ecords at"e pt"actica11y nonexistent.
<br />Reg:at"ding mot"e recent floods, town recot"ds, newspaper accounts,
<br />and eye-witness accounts ft"om long time n.sidenta of the area
<br />wet"e sout"ces of infot"mation for this t"epol:'t.
<br />According to a few of the longtime citizens of Rocky Ford, the
<br />bt"idge on Highway 71 was washed out in the flood of 1921. U.S.
<br />Geologic Survey Watet" Supply Paper No. 1455-A indicates that this
<br />bridge washed out again in 1955 (Reference 8). Also water was
<br />remembered to have been at a depth of 2 or I[\ore feet in the
<br />railroad yat"d at LaJunta, Colorado during the 1921 flood. In
<br />1965, the Swink underpass on Highway 50 was completely flooded
<br />due to high water on Timpas Ct"eek.
<br />
<br />Table 1 shows appt"oximate drainage areas at vat"ious points along
<br />the At"kansas.
<br />
<br />Location
<br />LaJunta - Downstream Study Limit, Arkansas River
<br />Rocky Ford - Upstream Study Limit, Arkansas River
<br />Fowler - Upstream Limit of Arkansas River
<br />Swink - Timpas Creek
<br />
<br />Obstructions to floodflows within the study reaches include
<br />natural obstructions such as thick brush and other types of
<br />vegetations growing along the streambanks, and manmade
<br />obstructions such a8 bridges and diversion dams. There are 11
<br />bridges within the study reaches, with 6 spanning the Arkansas,
<br />and 5 crossing Timpas Creek. During floods, these bridge
<br />obstructions impede floodflows and cause backwater conditions
<br />that may increase the flood heights upsteam of the obstructions,
<br />and velocities downstream of the ob$tructions.
<br />
<br />The floods of 1921
<br />in the study area.
<br />destruction:
<br />
<br />and 1965 heavily damaged bridges and highways
<br />The following pictures show examples of such
<br />
<br />Brosh washed out during floods 16 carried downstream and may
<br />collect at bridges and in culverts, thus creating a damming
<br />effect and overbank flow. As flood flows increase, masses of
<br />debris m.ay break loose and cause a wall of water and debris to
<br />surge downstream until another obstruction is encountered. In
<br />some instances, debris may collect to the point where structural
<br />capability is exceeded and a bridge is destroyed or abutments and
<br />approaches eroded and roadbeds damaged.
<br />
<br />The Arkansas
<br />flooding, the
<br />
<br />River and Timpas
<br />earliest flood of
<br />
<br />Creek
<br />record
<br />
<br />have II
<br />occuring
<br />
<br />lon~ history of
<br />in 1694, Large
<br />
<br />
<br />.
<br />
<br />- -....
<br />
<br />""" .,
<br />
<br />-
<br />
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<br />~'-:'t*"S:~"7-".'.j':f.tj .
<br />,,,~..-,.,~,,,,,..,'-"~_: ", ,;
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<br />',~:<li,'r)' ~
<br />,-".1.,; .-
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<br />
<br />There are no existing or authorized flood control structures in
<br />the study reach however, the Corps of Engineers has prepared a
<br />flood control protection study for La Junta (Reference 3). There
<br />are two irrigation canal diversion dams near the downstream limit
<br />of the study reach of the Arkansas River near La Junta and one
<br />near the upstream limit, near Fowler. These downstream
<br />structures divert ...ater from the Arkansas to the Fort Lyon Canal,
<br />and the upstream structure diverts water from the Arkansas River
<br />to the Otero Canal. However, during periods of very high runoff,
<br />diversions to the canal are often curtailed; consequently, any
<br />reduction of the flood peaks is uncertain and unlikely. The
<br />U.S. Buresu of Reclamation constructed Pueblo Dam on the Arkansas
<br />River, approxiamtely 6 miles upstream from the Gity of Pueblo,
<br />and approximately 70 miles upstream of La Junta. The dam ...ill
<br />control Arkansas River flows up to 87,000 ch, originating from
<br />the upper basin, but the reservoir ...ill have only limited effect
<br />on flood flows in Otero County (Reference 7).
<br />
<br />IV. HISTORY OF FLOODING
<br />
<br />,7-
<br />
<br />"'"est Bridge to North La Junta, looking northwest from
<br />Santa Fe Railroad Yards, 1921 Flood (County Road No. 28)
<br />
<br />,8-
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