Agriculture Reference
In-Depth Information
slopes are mathematically expressed as being
positive. The converse of going up a slope is
going down one, and a trail where a hiker is
working his or her way down a mountain is
described as a negative slope (see Figure 9.5-
B). Water, of course, flows downhill, there-
fore the slope might be described a negative
(or minus), say, 5 percent. When a contractor
is studying a grading plan and sees -2% or
just plain 2% on a walk or parking lot, the
contractor knows that the walk or parking
surface needs to slope downhill so that the
water flows in the direction the slope arrow
is pointing. Where a +2% is shown on a grading plan, the contractor knows
to slope a surface uphill. The use of + and - may seem confusing at first, but
the use of these symbols is one of the common conventions in landscape
architecture and civil engineering. The use of the plus or minus symbol
becomes mathematically important when preparing drawings in the design
of roadways or bicycle trails. The convention when using slope arrows in
grading plans is that the arrow is pointing in the direction the designer
wants surface water to flow (see Figure 9.6).
Figure 9.4-B
Trail with slopes varying from 1% to 12%
Figure 9.5-a
Positive slope
going uphill: +15%
Figure 9.5-B
Negative slope
going downhill: -15%
Figure 9.6
Note the use of arrows with percent of
slope indication in this preliminary grading plan. In
all cases the arrow is pointing in the direction the
designer intends surface water to flow.
Courtesy of sAdik ArtunC
