FLOOD11630 ‎(2)‎

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

including all engineering, design and construction supervision is $229,600 and will be fully
Federally funded under the Public Law 84-99 Levee Restoration and Repair program. Repair of
this levee will restore protection to 421 homes, 20 businesses, 1 public structure, and 57 barns,
detached garages, and sheds. The residential structures and contents have an estimated value of
$4,979,00; commercial structures and contents have an estimated value of $676,000; public
structures and contents have an estimated value of $33,000; and outbuilding structure and
contents have an estimated value of $622,000.
The floodplains for 5 event frequencies were delineated (5-, 8-, 10-, 25-, and 50-yeaz) as part of
this restoration study and justification effort. The analysis showed that under a SO-yeaz event,
the depth of water in the structures would vary from about 0.7 foot to ~.8 feet. If left un-repaired,
flood damages are expected to begin at the 5-year event. Based on the frequency of the past
flood event, the repaired project would provide protection up to the 8-yeaz event. The economic
analysis for the levee repair project resulted in a Benefit to Cost Ratio of 1.84. The economic
analysis was further evaluated eliminating 126 residences and outbuildings that wers within the
floodplain, but a considerable distance (up to a mile) upstream of the levees. The project still
resulted in a Benefit to Cost Ratio of 1.39. Finally, assuming further that 100 residences in
North La Junta are purchased or relocated out of the floodplain, the remaining economic benefits
would still produce a Benefit to Cost Ratio of 1.07. The sequence of assumptions is based on
Federal Emergency Management Agency (FEMA} program priorities to first elevate homes out
of the flood plain, second to purchase homes in the flood plain and third to relocate homes out of
the flood plain.
Las Animas: The existing Corps of Engineers levee at Las Animas performed well. Damage
was sustained at the toe of the levee in one short reach where the stream meandered into the
levee face. The channel flow was far below the capacity of the levee. Local officials expressed
interest in constructing a groin in place of the washed out berm constructed by the NRCS to
prevent the river from impinging directly on the levee. The Corps of Engineers and NRCS
worked together to design the groin. Damage to the toe of the levee will be repaired under the
Corps of Engineers Public Law 84-99 Emergency 'Levee Repair and Restoration authority. Other
than placement of a protective groin, there has been no interest expressed by local officials to
increase flood protection along this part of the river. The groin is scheduled to be constructed by
the NRCS with technical advice from the Corps of Engineers.
ALTERNATIVE FLOOD CONTROL CONCEPTS
Fountain Creek and Tributaries
As indicated earlier, a comprehensive and cooperative effort on the part of several agencies
would greatly enhance the possibility of finding viable flood control and sediment control
solutions for this watershed. A comprehensive study may reveal flood control and environmental
restoration features that provide incidental mitigation of streambank erosion and channel
aggradation problems. Further streambank erosion and downstream channel aggradation
Chapter 6- Recommendations for Futur~e Study
Post Flood Assessment Report 42 Drafr Revised 09/09/99