WSP05537

• File Number: 8443.100
• Description: Narrows Unit - Project Description
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 1/1/1967
• Title: Report on the Narrows Unit Colorado South Platte Division Missouri River Basin Project part 1
• Water Supply Pro - Doc Type: Report/Study

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Pro;ject Lands

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moderately steep. Portions of the uplands in the western part of
the project have sand-dune type of topography.

The river terraces and flood plains comprise 58 percent of the
service area. The terraces make up the greatest portion of the
valley, but they are not continuous throughout the project. Occasion-
ally, they are present only on one side of the river. The width of
the terraces ranges from about one-quarter of a mile to more than
10 miles and, except for minor areas adjacent to side drains, the
terraces are smooth and nearly level, In most instances, the
terraces rise 10 feet or more higher than the flood plains but
occasionally there is no distinct topographic break between the
flood plains and the terraces, The higher terraces are about 10
to 80 feet above the flood plains,

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The flood plains extend out on both sides of the river channel
to distances ranging from approximately one-tenth to one-half and
rIse 6 to 12 feet above the riverbed. The flood plains considered
in their entirety are quite flat, but the microrelief displays a
distinct hummocky condition whch is characteristic of intermittently
flooded areas with sandy soils. Lands within the flood plains
classed as irrigable are very minor--generally limited to areas
adjoining the terraces where there is no pronounced topographic
separation,

SOILS

The soils of the Narrows Unit area have developed under a
temperate, semiarid climate. The native vegetation consists of
short grasses interspersed occasionally with low growing shrubs.
These conditions have resulted in soils that are somewhat immature
and have only moderate amounts of organic matter,

The materials from which the major soil bodies have developed
are alluvium, aeolian deposits, and shales. The alluvium underlies
all of the South Platte Valley within the project area and ranges
in thickness from a few inches to more than 200 feet. Normally,
the alluvium is composed of a heterogeneous mixture of clay, silt,
sand, and gravel.

In the upland part of the service area, the soils have developed
either from aeolian deposits or are residual soils developed directly
frum shale. The aeolian deposits consist of a heterogeneous mixture
of clay, silt, and fine sand, The residual soils in some areas have
developed on Brule shale and in others on Pierre shale.

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