Geomorphic Assessment of Channel Systems
Their data are separated into three groups based on the composition of streambed and
streambanks. This eliminates the need for computing bed, bank or silt factors needed for
previous equations. Simons and Albertson's (1963) equations are referred to as the Modified
Regime Equations.
The U.S. Army Corps of Engineers (USACE, 1994) provides guidance on channel
design. Their recommendation is to use locally or regionally developed equations for channel
design. However, when this is not possible, relationships are given to provide rough
estimates for width, depth, and slope of a channel given the channel-forming discharge and
bed material.
3.1.3.5
Summary of Empirical Channel Design Methods
This brief review of empirically-based channel design procedures shows that each of
these methods is limited by at least one of the following two constraints:
C
the empirical data set is representative of a limited amount of data for the wide
range of stream and watershed types, and is not applicable outside the range of
data for which each relationship was developed; or
C
the concentration of sediment being transported is small, less than 500 ppm, and
the method requires that bed and bank materials are static.
While these methods are applicable within the limits for which each was developed, the two
primary constraints listed dictate that empirical methods have limited application for natural
streams.
3.1.4 Computational Design Methods for Channel Design
Two computer programs that can be used to aid in the design of stable channels are
SAM (Thomas et al., 1993) and HEC-6 (USACE, 1993). SAM allows for channel design
utilizing extremal hypotheses methods, and HEC-6 provides a method for computing bed
stability of alternative channel designs.
3.1.4.1 SAM
Thomas et al. (1993) developed SAM, a computer program to calculate the width,
depth, slope, and n-value for stable alluvial material. SAM is capable of determining stable
channel dimensions, calculating the bed material discharge, and calculating the sediment yield
of a stream. SAM is a relatively simple and quick computational procedure that allows
preliminary screening of design alternatives, and, in some cases, is suitable for final design or
performance monitoring.
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