plot above the stability curve will result in degradation, and combinations below
the curve will result in aggradation. The greater the distance from the curve, the
more severe the instability.
Constraints on this wide range of solutions may result from a maximum
possible slope, or a width constraint due to right-of-way. Maximum allowable
depth could also be a constraint. Depth is not plotted in Figure 2.10, but it is
calculated for each slope and width combination determined. With constraints,
the range of solutions is reduced.
Different water and sediment discharges will produce different stability
curves. First, the stable channel solution is obtained for the channel-forming
discharge. Then, stability curves are calculated for a range of discharges to
determine how sensitive the channel dimensions are to variations in water and
sediment inflow events.
The stable channel dimensions are calculated for a range of widths on either
side of a prescribed median value. If no median value is prescribed, the program
assigns a value based on the hydraulic geometry equation proposed in EM 1110-
2-1418 (USACE 1994).
B = 2.0 Q0.5
Equation 2-56
Figure 2.10. Graph of a family of slope-width solutions.
44
Chapter 2
Theoretical Basis for SAM.hyd Calculations
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