Agriculture Reference
In-Depth Information
from collecting and puddling, and causing a potential slipping or other
hazard. Typically, individual steps are designed with a .05 or 1 percent
slope, while the slope of a terraced landscape can vary depending on the
program conditions and the surface of the material (paved or planted).
Paved terracing with rough and irregular stone, such as shown in Fig-
ure 14.11-B, would be designed with a 1 percent slope in regions with low
rainfall such as Southern California and the U.S. Southwest (to facilitate
water percolation to recharge the aquifer). A slightly steeper slope of
1.5 percent might be preferable in wetter climates or those with heavy
snowfall such as the U.S. Pacific Northwest or Northeast.
deSiGn optionS for handLinG Storm Water
catch Basins
Catch basins are often used to collect surface water in grading situations
where swales and simple topographic modifications are not feasible.
Catch basins are set at the lowest elevation of an area that is shaped to
direct surface water to the catch basin. Catch basins can be installed in
narrow spaces (such as planting areas next to a building) or can be posi-
tioned within a large expanse of paving (such as a plaza or parking lot)
or in planted and lawn areas. Site-grading
plans that use catch basins for extensive
areas will position them in a grid pattern
rather than installing a single catch basin,
whenever possible. A single catch basin
has the initial high cost of making a con-
nection to a storm water system. The cost
can be spread out when multiple catch
basins are used.
The parking lot shown in Figure 14.12
may appear flat at first glance, when in
fact the pavement is divided into sloping
planes. The sloping pavement is formed
to create a ridge-like crown in the center
Figure 14.12
Note the catch basin next to the curb in the
middle of the photograph. Its purpose is to collect surface
water from the parking lot
