FLOOD04263

• County: Statewide
• Basin: Statewide
• Title: Design of Open Channels
• Date: 10/1/1977
• Prepared By: USDA Soil Conservation Service
• Floodplain - Doc Type: Educational/Technical/Reference Information

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3-25

a. Location of projected unstable reaches, if unprotected;
bed and/or banks by stationing.

(I) Elevation of unit or units with reference to invert
level.

(2) Cause of predicted conditions, such as tractive
stress or velocity in excess of allowable or
internal seepage forces.

b. Discuss unique conditions not fitting into the
assumptions made in Technical Release 25.

2. Bed material sediment problems if these influence stability
of proposed channel improvements.

3. Effect of program installations, such as floodwater, flood-
water detention or multipurpose structures, debris basins
and grade control structures on downstream reaches.

Evaluation in the Construction Stage

Unexpected discontinuities or unaccounted variations in soil character-
istics affecting stability.may be revealed during excavations for improve-
ments. It should be standard procedure for the geologist, design
engineer and soils engineer to examine the channel during or immediately
after excavation. With the profiles at hand, the geologist should make any
pertinent adjustments in unit delineation and ~nterpretations over those
prepared during the design investigations. Any significant alterations
pertaining to stability should be immediately called to the attention
of the project and construction engineers.

Testing

Purposes of Testin~

The purposes of testing soils from channel projects are fourfold:

I. To develop design values and correlation between properties of fine-
grained soils and field evaluation and classification of erosional
activity in constructed or natural channels now in use,

2. To provide values for use in the design of stable channels in gravels
and coarse sands from the standpoint of erosional activity.

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