ENVIRONMENTAL - International Erosion Control Association

Using an Erosion Model for Designing Roads That Reduce Soil Losses in the Forest
Figures 4 and 5 illustrate the equipment used to collect runoff and sediment from slopes for the
portion of the research conducted in the Talladega National Forest in Alabama, USA. This study
examined the effect of native and exotic vegetation and a Rolled Erosion Control Product for controlling
erosion and on the road slopes. The plastic pipes collected all the runoff and sediment from
each of four plots, located on the slopes at each site, and directed it to the blue storage containers. The
researchers measured the amount of runoff and sediment collected in each container.
Figure 4. Photo Credit: Johnny M. Grace, III.
researchers measured sediment and
runoff amounts from 164-ft. (50-m)
long sections of the road following
eight storm events over a 12-month
period. Precipitation for each of the
storms ranged from .1 in. to 5.5 (2.5
mm to 140.2 mm).
WEPP predictions of sediment
yields for the simulated storms were
consistent with measurements made at
the study sites. “The results indicate a
strong, but not a one-to-one, relationship
between predicted and observed
sediment yield for the road sections,”
Grace says. “However, predictions of
runoff yields were not nearly as good.
This is likely due to the inability of
adequately describing the effective
hydraulic conductivity and soil texture
to optimize sediment and runoff
yields predictions simultaneously.”
That, in turn, indicates the need
for additional field data and studies,
he notes. “We want to take a more detailed
look at some of the factors that
may be affecting runoff yields, such
as hydraulic conductivity and how it
differs with different road surfaces,”
Grace says. “Studies by the Forest
Service’s Rocky Mountain Research
Station in Colorado indicate that hydraulic
conductivity may be considerably
higher than previously thought.”
Figure 5. Photo Credit: Johnny M. Grace, III.
The Next Step
After confi rming the ability of
WEPP to predict sediment and runoff
in the two forests involved in this
project fairly accurately, Grace is now
looking at applying it to other forests
in the Appalachian Mountains,
coastal plains and piedmont areas of
the Southeast.
The Rocky Mountain Research Station
has done a lot work in validating
WEPP for conditions in the western
United States, he notes. His research
will help fi ll in a knowledge gap concerning
its validity in the Southeast.
“Assuming WEPP is valid in these
areas, forest managers will be able to
use it compare different erosion control
scenarios before designing and
building roads.”
Grace’s technical paper is available
at www.ieca.org > Information > Proceedings
2007 to present.
24 • ENVIRONMENTAL CONNECTION