FLOOD08449

• County: Bent
• Community: Bent County
• Basin: Arkansas
• Title: Lower Arkansas River Watershed and Flood Mitigation Plan for Bent County
• Date: 10/1/2000
• Prepared For: Bent County
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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Past Flood Mitigation Studies and Projects

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Several reports have been published regarding the Arkansas River and its tributaries within Bent County.
The)' are as follows

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1. Corps of Engineers - Las Animas Local Protection Project. Las Animas Lc\->ee, Las Animas. CO.
September 1%7.

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2. Corps of Engineers - FLOW - Damage Data. April 1994

3. Corps of Engineers - Analysis of Dcsign for John Martin Dam. April 1940

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4. Federal Insurance Administration - Flood lIazard Boundary Map. Bent County, Colorado,
Unincorporated Area. July 12. 1977.

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Rinr Sntem [,'olutioD

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In 19-1.8 the Corps of Engineers COmpldl.-d construction of John Martin Dam on the Arkansas River in
Bent County Colorado. The purpose of the dam was to prevent nooding and provide a water storage
source. In recent years and because of muhiple factors, the river belm.. John Martin dam is showing
increasing signs of capacity restrictions. This has occurred in large part because of tlow restrictions
caused by sediment buildup. agricultural and industrial encroachment. dl'Crease of wetlands, and salt
cedar overpopulation. These factors increase the risk of flooding. impact water quality. affect fannland
viability. degrade ecological health and increase erosion. For example. areas never reporting 1100d effect
have become inundated in recent years. Because of the extent of these phenomena. virtually every area
along the ri..,Cf is affccted. Recent damage has been depcndcnt upon the size of the flood event and the
surge area. I-ligh-risk river segments tend to be th05e clustered close to developed areas. where
encroachment has bt."Cn greatest. Compounding this problem is the COnlinued evolution of the rivet
caused by the effect of the dam and the uncontrolled cutting of the channel by fanners in the late 1960's.
TherefOre the problem is significantly ditTerent than just one of flooding within a natural selling. It is a
combination of factors that have inadvertently changed the conditions of the natural landscape featurl'S
and are causing incrl.'asoo \'ulnl--rability within the llood plain.

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Economic Ilazards

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In 1965. despite flood control by John Martin Dam. a flood of major proportions devastated the lower
Arkansas River basin in Colorado and into Kansas. Since this time. \'arious engint.'Cring controls have
been PUI in place. most shortly aller thai flood, In the last several years, communities along the river have
become concerned thai encroachment. agraddation. and ingrowth by salt cedar is significantly increasing
the risk of flood. The historical evolution of land use and floodplain management controls and the change
in floVli regime in water releases from John Martin Dam have not contributed to the mitigation of flood
risk. Under these conditions if a flood of similar magnitude as that of 1965 .....ere to occur, the impact
would be substantial. Estimated losses would begin with the fraction of land uses impacled ....ithin the
existing unprotecled floodplain. The actual value of this land is:
. Ag.rieuhuralland threatened has an actual \'alue of o\'er S IJ.378,9::!O.
. Residential properties threatened have an actual value ofS42,474.313.
. Commercial properties threatened have an actual value of S27.291.194.
. Total potential threatened impact is on properties with an approximate value ofS83.059, 757,

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