FLOOD04360

• County: Bent
• Community: Las Animas
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Interim Report on Review Survey for Flood Control
• Date: 8/1/1963
• Prepared For: Las Animas
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

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and then turn east to follow the same al igmnent as the Plan _A levee..
The rai Iroad grade would not have to be raised but the highway grade
would be raised 5 feet. This plan would provide protection to an
additional 850 acres of irrigated land and 550 acres of dry farm,
grazing, and other lands.

c. Plan C.- Plan C would further increase the area protected:
by 520 acres of irrigated farmland and 230 acres of dry' farm;'grb'zini, .
and other lands. The south bank levee wou Id be 9.6 mi les in length
and begin on high ground at U.S. Highway 50 about 5t mi I,es west'.oflas
Animas.' From this point, the levee would extend north across:f:l'1e rail-
road and continue northeast to fol low the same al ignment as Plan B:
The' highway grade wou I d not requ ire chang I ng but the ra I I road grade"
wou I d have to be ra i sed 6 feet. A compar I son of benef its and costs of
the th.ree plans, as shown on plate 3, indicates that PlanC woul,9'pro-
duce a greater excess of benefits over costs than Plans A and B.. C~rves
have been plotted, also as shown on plate 3, of the annual benefits.and
costs of var I at ions of P I an C I f constructed to prov i de protect Ion
aga I nst different discharges on the Arkansas River. As ind'icafedby
these curves, the annual charges increase sharply beyond 140,QbOc.t.s.
because of the necess i ty for ra i sing the ra I I road br i dge' across -'the
Arkansas River and extensive grade changes in the approach to 'the
br i dge, but the annua I benef its I ncrease at a more, constant rate, The
maximum excess of benef its occurs at about 140;000 c .f.s. In'viey, of
the forego i ng, P I an C constructed to prov i de protect i on aga i nst d'l s":
charges u'p to 140,000 c.f.s. was selected as the most logical solution
to the flood problem at Las Animas and vicinity and .has been ,designated
as the Las An i mas Loca I Protect i on Project. ,.

86. SELECTED PLAN OF I MPROVEM: NT . - The se I ectedp Ian of improve-
ment consists of 9.6 mi les of levee on theright bank of the Arkansas .
River and one mi Ie of levee on the left bank. Appurte'nailt works' Lnc lude
levee protective measures; an interior drainage system consisting of
outlet structures, a ditch, and ponding areas; a sewage pumping plant;
and intake structures for i rr i gat ion cana I s. 'Pert i nent projed "d:ata '
andeng i neer i ng features of the Las An i mas Loca I Proted Ion Project,
are given in table 5 and the plan is depleted on plate 2.

87. The levees would average 12 feet in height on the right bank
and I I feet on the left bank, al lowing a minimum freeboard of 4 feet
above th,e computed water surface prof i Ie of 140,000 c.f.s. The levee
would have! on2 side; slopes and a crown ~idth of 12 feet which would
permit access f,or maintenance equipment. The 'right bank levee would
be topped with a 6-inch grave I course to provide a lll9intenance rOad.
Borrow mater i a I wou 1 d be obta i ned from the dra I nage ditch, 'from, I oca~ '
t ions whe.re channe I clear I ng and stra i ghten I ng are requ i red ,and from
other designated borr'ow areas. The overbank areas under and between
the ra i I road and highway br i dges wou I d be. cleared to Improve the hy-
draulic characteristics of the channel. Flexlble~typebank 'protection
wou I d bel P I aced a long the toe of the I,evee through reaches vu I nerab Ie
to 'scoLlr. . ,

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R 1/28/64