where
GSi = transport rate for size class i
V = average flow velocity
D = effective depth of flow
Se = energy slope
Be = effective width of flow (width of portion of cross section which
is transporting bed material sediment)
de = effective particle size for the mixture
ρs = density of sediment particles
Gsf = grain shape factor
ds = geometric mean of particles in size class i
ib = fraction of size class i in bed
ρf = density of fluid
T = temperature of fluid
Of particular interest are the groupings of terms: hydraulic parameters (V, D,
Se, Be), sediment particle parameters (de, ρs, Gsf), sediment mixture parameters
(ds, ib) and fluid properties (ρf, T).
Not all listed parameters are used in all sediment transport functions. In
SAM.sed, the specific gravity of sediment defaults to 2.65, and the particle shape
factor defaults to 0.667. However, these defaults can be over-ridden.
Procedure for Calculating Sediment-Discharge Rating
Curve
The steps in calculating a sediment-discharge rating curve from the bed-
material gradation are:
1. assemble field data (cross sections and bed gradations)
2. develop representative values for roughness coefficients, geometry,
and bed gradation from the field measurements
3. calculate the stage-discharge rating curve accounting for possible
regime shifts due to bed-form change
4. calculate the bed-material sediment-discharge rating curve using
hydraulic parameters from the stage-discharge calculation.
SAM.sed can be used for step 4. The input information required by SAM.sed,
from step 3, can be obtained from SAM.hyd or HEC-2.
51
Chapter 3
Theoretical Basis for SAM.sed Calculations
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