Agriculture Reference
In-Depth Information
Then, of course, grading is required for roads, trails, and walkways.
Each has its unique design metrics, including considerations for safety,
mode of transport (such as motorized or
nonmotorized vehicle or bicycle), handicap
access, and design speed. In this chapter
we will look at a variety of grading design
situations. Keep in mind that the formula
S = V / H will be universally handy in solv-
ing most grading matters. The formula
will be useful in creating slopes for paved
areas or drainage elements such as swales;
establishing critical spot elevations for
paved and unpaved surfaces, as well as
wall heights (elevations); and for the spac-
ing of contours for creating desired land-
forms and pavement slopes.
A
B
D
C
98
99
100
101
Figure 13.1
Four common-site grading operations that
can be used singly or in combination, depending on the
site design features
GradinG of paved SurfaceS:
WaLKS and rampS
Paved surfaces such as the one shown in Figure 13.2 can be thought of
as monolithic slabs of concrete, asphalt, or modular elements that might
be generally level or designed with a slight to moderate pitch or slope
to direct surface water to either side and away from the paved areas.
In the case of a walkway, plaza, or parking lot, the paved surface often
has a main slope, and in the case of a walkway or driveway it may have
a secondary slope called a cross slope to modify the main direction of
water flow to one side, generally into a landscaped area or storm water
structure. You can see in Figure 13.2 that the main slope is 4 percent and
generally directs the flow of surface water downslope along the direc-
tion of the paved walkway. At the same time, the walkway was given a
1 percent cross slope so as to direct the water flow off to one side of the
walkway into an adjacent planting area. You learned in an earlier chap-
ter that water flows perpendicular to the contours, but, when there is a
