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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CHAPTER 2.. FIELD SURVEYS & PLAN LAYOUT

General

Objectives of the Engineering Survey

The surveys for channel improvement work should be in sufficient detail
to:

1. Determine "the location, hydraulic properties, visual characteristics
and condition of existing channels and associated structures.

2.. Determine the needed improvements on existing channels and the
required additional channels and appurtenant structures.

3. Determine the cost of the needed improvements.

4. Prepare suitable landrights work maps for easements and working
permit requirements.

These objectives apply to both planning surveys and final design surveys
and differ only in the amount of detail and precision needed for the
respective stages of project development.

Preliminary Surveys

Information Needed

To accomplish the objectives stated above, the following information
is needed for planning channel work:

1. Drainage area at junctions of tributaries and all flow control points.
Drainage areas also should be delineated for valley sections used
for hydrologic and economic evaluations where these are needed
at locations other than at junctions of tributaries and structural
control points.

The drainage area determinations, including those needed for drainage
purposes, should be made carefully for use in both the planning
and the final design stages of the project.

Where topographic quadrangle maps are available they are usually
sufficiently accurate for delineating and planimetering the required
drainage areas, except on extremely flat land. Field surveys may
be required to determine watershed divides on flat land. Where
feasible, the delineation of drainage areas should be checked by
means of a stereoscopic study of 4-inch or 8-inch = I mile aerial
photos.

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