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Changes in the cross-section for the potentially impaired reaches are measured to determine width, depth, slope, and calculated velocity. Shear stress and unit stream power are calculated using equations (Equation V-2) and (Equation II-11):
(eq. V-2) Y = 1.7 + 40 X (Lower 1/3 position)
Where:
Y = Sediment yield (tons/acres of road)
X = Road Impact Index
Unit stream power or power per unit of streambed area ( ) is defined as
(eq.II-11) 
where:
 is defined in Equation II-2 (below), and
u is mean velocity
(eq.II-2) 
where:
 is the specific weight of the fluid,
D is the mean depth, and
S is the water surface slope.
The RIVERMorph program may also be used to simulate width, depth, slope, velocity, and discharge for a wide range of stages (hydraulic geometry). This information is used to determine changes in unit stream power for the same discharge or for increased or decreased discharge. The purpose of this data is to provide basic channel hydraulic data to predict channel response to imposed sediment load, change in flow, and/or change in distribution of energy due to channel change. The model determines aggradation, stability or degradation, depending on the nature and extent of the channel change. The departure is compared to reference or stable condition.
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