Draft Technical Memorandum

• Description: Prepared for States of Colorado, Nebraska, and Wyoming related to Platte River Endangered Species Partnership ‎(aka Platte River Recovery Implementation Program or PRRIP)‎
• State: CO
• State: WY
• State: NE
• Basin: South Platte
• Water Division: 1
• Date: 2/6/2002
• Author: Parsons Engineering Science, Inc. Simons & Associates, Carter Johnson
• Title: Draft Technical Memoranda - Platte River Channel Dynamics Investigations
• Water Supply Pro - Doc Type: Report/Study

PARSONS
. DRAFT TECHNICAL MEMORANDUM
RESULTS OF TASK Al -- EVALUATION OF CURRENT
MORPHOLOGY AND STABILITY OF THE PLATTE RIVER
CHANNEL
•
INTRODUCTION
Platte River Channel Dynamics Study
A team composed of representatives of several Federal agencies currently is preparing
an Environmental Impact Statement (EIS) for the Platte River in the States of Colorado,
Wyoming, and Nebraska. The EIS is being completed in order to address issues related
to the preservation and restoration of critical habitat for threatened and endangered
species in the central reach of the Platte River, from Kingsley Dam to Mormon Island, in
Nebraska. In January 2001, the Platte River EIS team issued two draft technical reports
entitled "Platte River Channel: History and Restoration" (Murphy and Randle, 2001a)
and "Platte River Sediment Transport and Riparian Vegetation Model" (Murphy and
Randle, 2001b), prepared jointly by the U.S. Bureau of Reclamation and the U.S. Fish
and Wildlife Service.
After reviewing the draft reports, representatives of various agencies in the three
affected States had concerns regarding some of the assertions, assumptions, and
conclusions presented in the reports. As a consequence of their concerns, a coalition of
interested parties, including the States of Colorado, Wyoming, and Nebraska, retained a
team headed by Parsons Engineering Science, Inc. (Parsons) to:
• provide a critical review of the assertions, assumptions, and conclusions presented
in the draft reports;
• evaluate the methods used by the EIS team in conducting their investigations into
conditions on the Platte River;
• evaluate the technical information on which the conclusions of the reports were
based; and
• where appropriate, develop alternative hypotheses to explain some or all of the
changes that have occurred in the morphology, hydrology, and hydraulics of the
Platte River system.
The technical evaluations completed by the Parsons team were conducted as a series of
14 complementary investigations divided into five categories that would address general
issues identified during review of "Platte River Channel: History and Restoration"
(Murphy and Randle, 2001a) and "Platte River Sediment Transport and Riparian
Vegetation Model" (Murphy and Randle, 2001b). The following issue categories were
identified:
• A. Questions Regarding Channel Narrowing or Deepening
SAES \WP\PROJECTS\3- States\A1 Final Tech Memo.doc
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