FLOOD10000

• County: Bent
• Community: Las Animas
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Las Animas Local Protection Project Design Memo Number 1 Hydrology
• Date: 9/1/1967
• Prepared For: Las Animas
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

9-03. Planning studies have not progressed to the point of firm
levee alignments. As a result, the study to locate and size the in-
terior drainage structures and ponding areas mu~t be deferred. Data
on these items will be detailed in the g3neral design mamorandum.

9-04. Existing inte~op ~inaqe pattern.- The proposed levee
on the left bank would extend about one mile upstream from the U.S.
Highway SO bridge. The levee would be south of and parallel to Co)~-
rado Highway 194. The state highway is elevated 4 to 5 feet above
natural ground and water ponds on the north side of the highway em-
bankment. These ponding areas ext~nd north about 500 feet where a
steep bluff limits their areal extent. Three small culverts are used
to conduct flows under the state highway to the Arkansas River. With
the proposed levee in place, it will be necessary to collect the out-
flows from these three culverts and convey the combined flow to an out-
let through the levee.

9-05. On the right bank, the interior drainage areas lie within
the flood plain and are bounded by the Arkansas River on the west,
north, and east, and by the AT&SF Railway embankment on the south.
The Las Animas Town Ditch and the Consolidated Ditch are elevated 3
to 4 feet above natural ground. The June 1965 flood rendered the in-
take structure of the Las Animas Town Ditch ineffective. This ditch
now shares the same intake structure as the Consolidated Ditch by use
of a connecting lateral. The irrigation ditches and field borders are
barriers to storm runoff. Jones Ditch is located at the base of the
foothills south of Las Animas and intercepts storm runoff from the
foothills. The ditch has a capacity of about 250 c.f.s. and is formed
by a downhill levee to facilitate runoff interception. Jones Ditch
does not have a history of breaching from storm runoff. Storm runoff
exceeding the ditch capacity would spill onto the downhill farmland
and be confined to the south of U.S. Highway SO and the AT&SF Railway
embankment. This runoff would flow in an easterly direction toward
the Purgatoire River and would not be intercepted by the levee system
of the proposed project.

9-06. The storm runoff for the city of Las Animas is presently
conveyed by five ditches. Two of these ditches empty directly into
the Arkansas River, two empty into an abandoned gravel pit just south-
east of the U.S. Highway 50 bridge, and one empties into the Purgatoire
River. As shOWn on plate 19, the two ditches that empty into the Ar-
kansas River are located parallel to and just west of the approach to
the U.S. Highway SO bridge. Another ditch is located on the east side
of the approach to the bridge and drains into an abandoned gravel pit.
The ditch that drains the northeast section of the city also empties
into the gravel pit. Drainage from th~ southern section of the city
is collected into a ditch that runs east, parallel to and south of
the AT&SF Railway to the Purgatoire River.

29