CHAPTER 7
CLOSING
Channel modification and channel improvement activities frequently have far reaching impacts
upstream and downstream of the project site. Channel modification activities can adversely impact channel
design features such as flood control, navigation, sediment control, and in-stream and riparian habitats.
These activities are recognized by the Environmental Protection Agency (EPA) as a major source of
nonpoint pollution. The Water Quality Act of 1987, section 101, includes the following policy statement:
It is the national policy that programs for the control of nonpoint sources of pollution be
developed and implemented in an expeditious manner.
Channel rehabilitation design should be applied not only to unstable systems that are causing
problems, but also to new project designs where it is anticipated that changes made to the existing system
will result in long-term stability problems. Because of the complexity of the channel rehabilitation design
process, it is not easily summarized as a linear sequence of steps to be followed. The systematic approach
taken by this manual is necessary for developing a workable project design that will function as intended.
The design of these types of projects requires the synthesis and integration of extensive background data
such as watershed geology, geography, sediment, hydrology, and hydraulics with analytic and empirical
design procedures.
Unfortunately, at this time, no nationally recognized set of design and performance criteria exist to
meet this mandate, nor is there a comprehensive manual that provides guidance for systematically
approaching channel rehabilitation design. This manual has been developed as a reference to be used in
channel rehabilitation training courses to be taught by the Waterways Experiment Station (WES) in
cooperation with the EPA. The manual is designed to present an organized, systematic approach to
channel rehabilitation, beginning with project planning and goal setting, through the preliminary project
design phase. Specific alternative designs for channel rehabilitation are not presented in this manual.
References for specific design information are provided in the text. The topics presented in this manual
include:
1)
The channel rehabilitation design process;
2)
Geomorphic assessment and analysis of the proposed project area;
3)
A summary of channel modification activities;
4)
Fundamental engineering design computations to support systems analysis; and
5)
Preliminary design procedures for stable channel design.
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