WSP07081

• File Number: 8101
• Description: Arkansas River Basin Description
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 6/1/1960
• Author: Unknown
• Title: Watershed Work Plan - Fishers Peak-Carbon Arroyos Watershed - Las Animas County - Colorado
• Water Supply Pro - Doc Type: Report/Study

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SECTION 2

INVESTIGATIONS, ANALYSES, AND SUPPORTING TABLES

INVESTIGATIONS AND ANALYSES

Project Formulation

The principal objective of this project is to reduce floodwater,
sediment, and erosion damages to an area in and adjacent to the City
of Trinjdad, Colorado. This involves the control of large volumes
of flooawater, resulting from summer storms of high intensity.
Consideration was given in the preliminary investigations to enlarging
the channel capacities through Trinidad, including the closed
conduits, in combination with floodwater-retarding structures. The
extremelY high cost for the channel improvements dictated that the
most economical method of providing the desired degree of control
was by the floodwater-retarding structures. Alternate floodwater-
retarding structure sites downstream from those sites selected
were studied and rejected primarily because of unfavorable spillway
locations and long distances to borrow materials. The level of
flood protection to be provided the damage areas was mutually
agreed upon; however, special studies were made to determine if the
level of protection was adequate or excessive. These studies indicated
that the proposed plan provides adequate level of protection and
optimum benefits.

A reconnaissance soil survey and a range site and cover
condition class survey were made of the watershed. These surveys were
used by Work Unit and Watershed Planning Party personnel to determine
soil classification, slopes, land use, erosion conditions, and
hydrologic characteristics of the watershed. This information
provided the basis for the determination of the kinds and amounts
of land treatment measures needed. The land treatment measures
proposed include only such kinds as listed in technical guides of
the Purgatoire Soil Conservation District.

"

The problem location map was used to determine structur~l needs
and locations. Engineering, hydrologic, geologic, and economic
investigations and analyses were made to determine the physical and
economic feasibility of the proposed structures. A combination of two
floodwater-retarding structures, one diversion, and channel improve-
ment was found to give the optimum degree of damage reduction to the
area of most intensive damage.