FLOOD07306

• County: Weld
• Community: Greeley
• Stream Name: Cache La Poudre River
• Basin: South Platte
• Title: Cache La Poudre River General Investigation Study, Greeley, CO
• Date: 5/1/2005
• Prepared For: Greeley
• Prepared By: USACE, Omaha, NE
• Floodplain - Doc Type: Project

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study can be enlarged if desired, to include tributary flood issues, channel stability and
other issues that surface during the first part of the feasibility study effort,

More details on the proposed study effort, and the specific tasks to be performed by each
member of the team, are provided in the Project Management Plan Appendix A.

1.2,2 FLOOD DAMAGE REDUCTION
The flood situation in Greeley has been studied in recent years, and the results from those
earlier reports will be used in the plan formulation effort, Geographic Information
Systems (GIS) information will be used as available, When useful, existing data will be
updated with new information that has been collected in the past few years, A major
flood in 1999 provided additional focus to alleviating the flood threat. A goal ofthis
proposed study effort will be to determine the economic feasibility of a flood control
project at Greeley, Hydrologic and hydraulic models will be developed that allow
detailed analysis of alternatives by routing historical floods and floods of various
frequencies through Greeley and evaluating stages at specific locations and available
flood storage against flood volumes. The adequacy of any existing levees in the city will
be evaluated so that decisions can be based upon their potential service during a major
(100 or 500-year) flood.

The existing floodway mapping will be used when analyzing flood reduction alternatives.
Both structural and non-structural flood mitigation methods will be considered, If a
structural flood damage reduction measure is selected, a Conditional Letter of Map
Revision (CLOMR) will be developed and submitted to FEMA, in order to expedite the
process of having the Greeley flood insurance maps revised to reflect the reduced
potential flood damages.

1.2.3 ECOSYSTEM RESTORATION
Recognizing the relative rarity of riparian ecosystem on the high plains of eastern
Colorado, feasible alternatives will be identified that can lead to improvements in wildlife
habitat, native ecosystems and water quality in the Greeley area, A goal of this study will
be to identify means by which the riparian ecosystem can be improved, When feasible,
ecosystem restoration goals will be pursued in conjunction with the flood control effort,
An example is the establishment of greenways where the floodway is widened,
Ecosystem restoration alternatives will be formulated from different mixes of
environmental restoration measures, Measures are expected to include restoration of
river meanders, side channels, oxbows wetlands and riparian vegetation and habitat.
Where possible, invasive species will be replaced with native vegetation, The Corps will
also prepare the NEP A / Environmental Assessment, and related reports as required for
the flood reduction and ecosystem restoration measures that are selected.

1.3 Services to be Provided
The Corps will assist the local Sponsor in identifying flood control, water resource and
ecosystem problems within the reach of the Cache la Poudre River in and around City of
Greeley, Colorado, evaluate possible solutions to correct the problems, and recommend a

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