Agriculture Reference
In-Depth Information
The designer would then select the arrows going from the quad-
rant corners (A) to the catch basin, indicating direction and percentage
of slope (see Figure 12.10-C). Start-
ing with a slope of 1 percent, the
elevation of the catch basin would
be established. To check to see if 1
percent is too steep, calculate the
percent of slope from the midway
points of the watershed outline
to the catch basin. The calculated
slope should be less than 2 percent.
If it is more, then reduce the slope
from the corners to the catch basin
as low as .5 percent slope (paved
areas in a plaza-like situation can
work with .5 or 1 percent slopes).
The consideration for setting
the catch basin elevation is to start by creating a .5 or 1 percent slope
along the longest diagonal from the corners to the catch basin. If the
slope along the longest diagonal is 1 percent, the shorter distances from
the watershed outline to the catch basin will be slightly steeper. In order
for the surface to appear “flat” or level—which would be an appropriate
design intent in a plaza situation—the pavement where surface water
travels the least distance should not be greater than 1 or 1.5 percent. If
the slopes for the shorter distances are steeper than 1.5 percent, then
revise the longest diagonal to less than 1 percent, say, to .5 percent of
slope. In this example, the perimeter elevation is 102.0´, and the catch
basin rim elevation is 101.7´.
A
B
B
A
A
B
B
CB
101.7'
A
C
102.0'
Figure 12.10-C
Step Three
creatinG a ScuLpted Landform
Site grading can be guided by practical considerations as well as the
aesthetic goals of the designer. Successful site-grading solutions pay
