Agriculture Reference
In-Depth Information
the StepS for eStaBLiShinG Spot
eLevationS on a SLopinG Surface
In Figure 10.20 is a paved surface that is to be constructed with a 2 per-
cent slope, sloping down from point A to point B. From the information
contained in the figure it is possible to calculate the spot elevations for
many points on the paved surface. We will begin by determining the
spot elevations of points A and C.
To start, ask yourself: What do I know to apply to the formula
S = V / H?
Slope is 2 percent, as indicated by the line drawn between points A and C.
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Using 40 scale measure the horizontal distance from A to C.
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The elevation where the 34' contour intersects the slope line indicated
between points A and C is 34. (point E)
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The elevation of point A would be higher than points E and C
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Let's continue: Switch to Figure 10.20-B to calculate the spot eleva-
tion of point A. What we know is that point E is at the intersection of the
diagonal slope line with the 34-contour. The elevation of E is 34'.
Measure the horizontal distance between points A and E = 20 feet.
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We know the percent of slope is 0.02.
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S = V / H
.02 = V / 20' V = .02 × 20'
V = 0.4"
Point A elevation = 34' + 0.4' = 34.4
The elevation of point C can be calculated considering that we now
know the elevation of point A, and we know the surface is sloping down
at 2 percent toward point C. Now measure the horizontal distance from
point A to point C, which let's say is 68'.
S = V / H
.02 = V / 68'
V = .02 × 68'
V = 1.36'
Point C elevation = 34.4' - 1.36' = 33.04
