WSP06131

• File Number: 8149.911
• Description: Miscellaneous Small Projects and Project Studies - SE Needs Assessment and PSOP
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 8/1/2001
• Author: US Army Corps of Eng
• Title: Arkansas River From John Martin Dam To The Colorado-Kansas State Line Channel Capacity and Riparian Habitat Planning Study
• Water Supply Pro - Doc Type: Report/Study

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., 7 GA.RKANSAS RIVER FROM OTERO /PUEBLO COUNTY LINE
1 ~l TO JOHN MARTIN DAM
CHANNEL CAPACITY AND RIPARIAN BABITA T PLANNING STUDY

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Prepared for the
Colorado Water Conservation Board
by the
U.S. Army Corps of Engineers, Albuquerque District
under the authority of the Planning Assistance to States Program

August 2001

SUMMARY OF FINDINGS AND RECOMMENDATIONS

The channel capacity of the Arkansas River above John Martin Dam has decreased
significantly over time. In the early 1900's the channel capacity for Problem Areas 1,2 and 3
was 15,000 cubic feet per second (cfs). By 1965, channel capacity had decreased to about
10,000 cfs and since the 1999 flood flows the channel capacity is now between 1,000 and 3,000
cfs due to ellcroachment on the f100dway by development and vegetation and sediment. Other
studies also showed a problem with high water table resulting in subsurface damage to crops in
many areas of the flood plein.

In October, 1999, the Colorado Water Conservation Board (CWCB) requested planning
assistance from the U.S. Army Corps of Engineers, Albuquerque District (Corps) for restoring
hydraulic capacity and riverine/riparian ecosystem values in the Arkansas River above John
Martin Dam. A Planning Assistance to States (Section 22) agreement (SO/50 cost share) was
signed by the CWCB and Corps in December 10,1999.

This study's purpose is to develop and evaluate plans which, when implemented, can
improve channel capacity for flood flows and restore riverine and riparian habitat along the
Arkansas River above John Martin Dam. Changes in current reservoir operation plans were not
a study objective. .

The Arkansas River study reach extends between the OterolPueblo county line and John
Martin Reservoir. The CWCB and Corps coordinated with local and state interests to identify
three specific problem areas to investigate, totaling approximately 1 1 river-miles. The three
areas selected for study do not include all known problems within the reach upstream of John
Martin Reservoir, nor are they necessarily the most crucial. Rather, they were selected 88
examples of typical problems within the reach.

A geomorphological Bssessment, which included the study reach was completed in 1997
by the U.S. Army Corps of Engineers Waterways Experiment Station and provided an overview
of the geologic, climatologic, and hydrologic forces influencing the Arkansas River during the
past century. The Albuquerque District conducted all hydraulic and ecological investigations.

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