Fundamentals of Engineering Design
Actively aggrading and degrading channels can go through a complex cycle of response,
which may exhibit large departures from normal hydraulic geometry relationships. For
example, a channel in the earlier stages of active incision may be abnormally narrow.
The use of all three charts does not permit explicit selection of roughness and allowable
velocity or shear stress. An alternative hybrid approach involves determining channel
properties using three relationships: a) the top width-discharge relationship of Figure 5.34;
b) the Manning formula with roughness estimate based on guidelines or experience; and c) an
allowable velocity or shear stress.
HYDRAULIC DESIGN PACKAGE FOR CHANNELS (SAM)
Thomas et al. (1994) developed the Hydraulic Design Package for Channels (SAM). SAM is a
computer program available through the USACEWES. The program was developed to provide the
designer with a tool to assist in sediment transport calculations and the design of stable flood control
channels. SAM is organized into three major modules: 1) sediment transport calculations, 2) sediment
yield calculations, and 3) hydraulic calculations. Additional information on the capabilities of SAM and
availability can be found on the website http://chl.wes.army.mil/ software/sam/.
188.8.131.52 Sediment Transport Calculations
The sediment transport module of SAM computes sediment transport rate as a function of known
hydraulic parameters. Currently there are 19 sediment transport equations incorporated into SAM.
Typically sediment transport is calculated based on the probabilistic distribution of multiple grain size classes
in the bed material. However, some of the equations calculate sediment transport using a single
characteristic grain size (D50). The sediment transport equations included in SAM are listed:
Meyer-Peter and Mller
Meyer-Peter and Mller, D50
Einstein total load
Toffaleti-Meyer-Peter and Mller