FLOOD07093

• County: Otero
• County: Pueblo
• Community: Otero, Pueblo Counties
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Arkansas River Channel Capacity and Riparian Habitat Planning Study
• Date: 8/1/2001
• Prepared For: CWCB
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

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ARKANSAS RIVER FROM OTERO/PUEBLO COUNTY LINE
TO JOHN MARTIN RESERVOIR
CHANNEL CAPACITY AND RIPARIAN HABITAT PLANNING STUDY

1. INTRODUCTION

The channel capacity of the Arkansas River in Problem Areas 1,2 and 3 above John
Martin Dam, has decreased significantly over time. When Pueblo Dam was completed in 1975,
the channel capacity was estimated to be 15,000 cubic feet per second (cfs). By 1965, channel
capacity had decreased to about 10,000 cfs due to encroachment on the floodway by
development and vegetation (USACE 1983). During the spring of 1999, reported flood flows
revealed that the channel was not able to convey flows of even 3,000 cfs, due to decreased
channel capacities and caused backwater effects, including a high water table and subsurface
damage to crops in many areas of the flood plain.

In an October 1, 1999, letter to the U.S. Army Corps of Engineers, Albuquerque District
(Corps), the Colorado Water Conservation Board (CWCB) formally requested Section 22
planning assistance for restoring hydraulic capacity and riverinelriparian ecosystem values in the
Arkansas River above John Martin Dam. A Planning Assistance to the States (Section 22)
agreement (50/50 cost share) was signed on December 10, 1999.

1.1 STUDY AUTHORITY

This channel capacity and riparian habitat planning study was performed under authority
of the U.S. Army Corps of Engineers, Albuquerque District, Planning Assistance to States
Program. The program's authority stems from Section 22. of the Water Resources Development
Act of 1974 (Public Law 93-251), as amended. Section 22 authorizes the Secretary of the Army,
acting through the Chief of Engineers, to assist the states in the preparation of comprehensive
plans for the development, utilization and conservation of water and related land resources of
drainage basins, watersheds, or ecosystems. Section 22 studies are undertaken for planning, not
design and construction, purposes.

1.2 STUDY PURPOSE

The study's purpose is to develop and evaluate long-term maintenance 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. Investigation of changes to the
current reservoir operation plan was not a study objective.

1.3 STUDY REACH AND TYPICAL PROBLEM AREAS

This study will focus on three specific problem areas within the reach of the Arkansas River
between the Otero/Pueblo county line and John Martin Reservoir. Two primary problems have
been identified within these three problem areas: high groundwater table and reduced channel
capacity. This study involved a cooperative effort between the CWCB and the Corps to analyze

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