Uftrted
Environmental Protection
Agency
Municipal Enviroransntfl! Ftosearch EPA-SGQ/2-79-124
laboratory December 1979
Cincinnati OH 4526S
and Dwolopmwtt
Evaluation of
Selective Erosion
Control Techniques
Piedmont Region of
S.E. United States
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution-sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-79-124
December 1979
EVALUATION OF SELECTIVE EROSION CONTROL TECHNIQUES
Piedmont Region of S.E. United States
by
Herb Buxton
Frank T. Caruccio
University of South Carolina
Columbia, South Carolina 29208
Grant No. S-803724
Project Officer
Hugh Masters
Storm and Combined Sewer Section
Wastewater Research Division
Municipal Environmental Research Laboratory (Cincinnati)
Edison, New Jersey 08817
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names of commercial products constitute endorsement or
recommendation for use.
-------
FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of the environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention, treat-
ment, and management of wastewater and solid and hazardous waste pollutant
discharges from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize the adverse
economic, social, health, and aesthetic effects of pollution. This publi-
cation is one of the products of that research; a most vital communications
link between the researcher and the user community.
Loss of soil to erosive forces of wind and water is accelerated during
times when a rapidly growing population places increasing demands on the
natural environment for housing, food, and energy. This investigation
demonstrates the relative efficacies of a number of soil stabilizing and
revegetation treatments that are commercially available for short-term
stabilization of areas undergoing construction activities.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
-------
ABSTRACT
Commercially available soil stabilizers, including chemical tackifiers,
hydromulches and blanket (netting) products and combinations thereof, were
tested in the Piedmont of South Carolina. The test site was designed to
measure sediment yields to provide a quantitative assessment of treatment
effectiveness.
Following a severe rain, during the period before the establishment of
a dense grass cover, it was found that the blanket products and straw
mulches provided the soil with maximum protection from erosion. Some tack-
ifiers were effective in stabilizing the fine fraction of the soil. Some
hydromuT.ches tended-:tb be washed away and were not effective in inhibiting
soil erosion.
Each treatment contained a standard lime, seed and fertilizer mixture
to test the ability of the technique to produce a dense vegetative cover.
After 8 to 12 weeks, the straw and blanket products produced a more dense
vegetative cover than the hydromulches and tackifiers. This was probably
due to increased soil surface moisture afforded by the former as an
insulating blanket.
With time, however, as lateral rhizome .development of grasses took
place, the soil protection was more readily afforded by the vegetative cover
and all sediment yields decreased.
A cost analysis showed that some of the more successful treatments are
too expensive to be applied routinely over large areas. The results of
this study were comparable with those of other reported studies.
The report was submitted in partial fulfillment of Grant No. S-803724
by the University of So.uth Carolina under sponsorship of the U.S. Environ-
mental Protection Agency. This report covers the period May 1977 to January
1978, and work was completed as of July 1978.
IV
-------
CONTENTS
Foreword i i i
Abstract iv
Figures vii
Tabl es i x
Acknowledgments x
Section
1. Summary and Conclusions 1
2. Introduction 3
Purpose 3
Test Site 4
3. Design and Installation of the Test Facility 7
Grading and Establishing Runoff Plots 7
Design of Erosion Monitoring System 11
Treatment for Volunteer Vegetation 14
Fertility Analysis 15
4. Erosion-Revegetation Treatments 16
Treatments, Design and Analysis 16
Treatments Selected for Testing 17
Application of Treatments 19
5. Photographic Representation of Treatment
Response 24
Initial Appearance After Application
(9/25/77 through 10/1/77) 24
Treatment Response Through 10/28/77 31
Treatment Response From 10/28/77 Through
11/28/77 32
Treatment Response From 11/28/77 Through
12/15/77 33
Treatment Response From 12/15/77 Through
1/23/78 33
6. Sediment Sampling Procedures and Analysis 34
Sampling 34
Laboratory Analysis 34
-------
7. Sediment Yield Data 37
Sediment Yield Comparison 37
Treatment Efficiency as a Function
of Grain Size 43
8. Cost Benefit Analysis 46
Comparison with Sediment Yield Data
i n the Li terature 49
References 53
Appendix
Photographic representation of treatment
response from 10/28/77 through 1/23/78 55
-------
FIGURES
Number Page
1 Location and topographic map of the
test si tes [[[ 5
2 Overview of project site ........................................... 6
3a Overview of test site during preliminary
slope modification ............................................... 9
3b Overview of test site during preliminary
slope modification ............................................... 9
4 Photograph of vinyl borders used in
separating plots ................................................. 10
5 Overview of center hi 11 slope (Site B)
with vinyl plot borders installed
and final grading completed ..................................... 10
6a Photograph of sediment collecting
trough [[[ 12
6b Photograph of sediment collecting
trough [[[ 12
7 Completed erosion-runoff monitoring
system ............. ............................................. 13
f
8 Photograph of herbicide control
system [[[ 14
9 Hand weeding of plots ............................................. 15
10 Photograph of Reinco laboratory
scale hydroseeder ......... . ..................................... 21
11 Photograph of hydromulch application
12 Photograph of plot surface following
-------
FIGURES (Continued)
Number Page
14 Plot A-l on 9/25/77, following
application of jute netting 26
15 Plot A-5 on 9/25/77, following
application of Excelsior blanket 26
16 Plot B-9 on 9/25/77, following
application of Hold gro erosion
control fabric 27
17 Plot A-7 on 9/25/77, following
application of straw mulch and
Vexar net ' 27
18 Plot A-4 following application of
Si 1 va wood fiber mul ch 28
19 Plot B-17 30 hours after application
of Conwed wood fiber showing
bl eached nature '. 28
20 Plot B-12 following application
of Pulch paper hydromulch 29
21 Plot A-3 following application
of Petroset SB 29
22 Plot C-20 following application
of Crust 500 30
23 Photograph of Plot A-8; untreated 30
24a Method of sediment sampling 35
24b Method of sediment sampling 35
25 Sediment analysis lab bench 36
26 Rainfall distribution and intensity
in area of test sites during period
of study 38
27 Sediment yields grouped by treat-
ment types 47
vm
-------
TABLES
Number Page
1 List of Various Treatments Monitored for Efficiency of
Erosion Control and Revegetation on Drastically Dis-
turbed Soi 1 SI opes 18
2 Application Rates of Mulches and Tackifiers Used
in this Study 20
3 Standard Seed and Fertilizer Application Rates Used
in this Study 20
4 Sediment Yield Data for all Plots 40
5 Fine Grain Sediment Yields of Test Plots for
Each Sampling Period 44
6 Cost Analysis on Per Acre Basis 47
7 Comparison of Effectiveness of Erosion Revegetation
Treatments by VM Factor for Field Test Data 50
IX
-------
ACKNOWLEDGMENTS
The success of this study would not have been possible without the help
and cooperation of numerous people and agencies. We fully acknowledge the as-
sistance of the South Carolina Department of Corrections and the cooperation
provided by Mr. W. Leith by placing at our disposal a portion of the Wai den
facility for use as a test site. The South Carolina Land Resources Conservation
Commission, with the help of Mssrs. J. Parris and Roger Mudd, provided inval-
uable field and logistical support. Mr. J. Reynolds, formerly with L.R.C.C.,
was responsible for the coordination of study and continued to help us after
he left the project.
Special mention is necessary of the numerous companies who donated many
of the products and gave willingly of their time in assisting us in product ap-
plication and specifications. Our special thanks to Gulf States Paper, Tusca-
loosa, Alabama, for freely showing us their research facility and assisting us
in test site development.
Mr. A.P. Barnet, Agriculture Research Service, Watkinsville, Georgia, was
instrumental in formulating the design of our test site. And Mr. Bill Plass,
United States Department of Agriculture Forest Service, Princeton, West Virginia
willingly provided us with the small hydroseeder which was extremely critical
to the successful completion of the study.
Our special thanks to our field crew, Mark Williams, Nick Mike, Dave
Herting, Helen Johnson and Glen Moss, who performed their jobs superbly, at
times under adverse conditions.
Last but not least, our gratitude to Mr. Hugh Masters, who took charge
of the project during the last year and a half, and provided us with the con-
tinual support, encouragement and understanding which led to the successful
completion of the study.
-------
SECTION 1
SUMMARY AND CONCLUSIONS
This study was designed to test the effectiveness of a variety of soil
stabilizing and revegetation treatments in the Piedmont of the southeast.
The specific objectives were to:
(1) assess which of the commercially available techniques or treat-
ments were most effective in inhibiting soil erosion.
(2) determine the efficacy and time for the treatments to establish
a vegetative cover.
(3) attempt to ascertain the relative efficiencies and economic
considerations of each treatment tested.
A parcel of land having a uniform slope and constant exposure was cho-
sen within the Walden facility of the South Carolina Correctional Institute
located approximately ten miles (16km) northwest of Columbia, South Carolina.
A 15 acre (6.1 ha) site was subdivided into 24 test plots, each 30 feet
(10 m) long with 90 to 150 feet (30 to 50 m) widths. Al'1 slopes had a 13%
grade. The individual test plots were separated from each other by vinyl
borders which served to prevent water from flowing between plots. In turn,
each plot was subdivided into a demonstration portion, which would be used
for visual comparisons, and a sediment yield plot. At the base of the lat-
ter, sediment and water volume collectors were installed to measure the sed-
iment yields from each plot. All plots were hand raked to a uniform slope
and treated to discourage volunteer vegetation.
The treatments tested were (1) four hydromulches (Conwed, Superior
Fiber, Silva Fiber and Pulch), (2) three netting products (Jute, Hold gro
and Excelsior blanket), (3) eight tackifiers (Curasol AK, Terra Tack III,
Aerospray (or DCA 70), Crust 500, Dow mulch binder, Petroset SB, Perma Soil
and Genaqua), used as prescribed with a standard wood mulch, (4) straw mulch
tested with three chemical stabilizers (Curasol AK, Terra Tack II and Dow
mulch binder) and one plastic net (Vexar). In conjunction with the treat-
ments, all plots received a standard lime, seed and fertilizer mixture. Of
the remaining five plots, three were treated only with a standard lime, seed
and fertilizer mixture as a control and two were left disturbed with no treat-
ment at all.
The sites, following installation, were routinely inspected and the
sediment yields were sampled five times during the period from October 28,
1977 to January 23, 1978. The sediment yields were related to treatment
-------
effectiveness with regard to (1) soil stabilization prior to a full vegeta-
tive cover and (2) the ability of the treatment to quickly produce an
adequate vegetative cover.
During the first 8 to 12 week period, at a time when the plots were
bare and the vegetation had not become fully established, a high intensity
rainfall occurred which severely tested the treatments' ability to protect
the soil surface. It was found that some tackifiers wepg effective in
protecting the fine grained portion of the soil, while some mulches tended
to wash away. The blanket products and the straw covers gave the best
protection. Straw applied as a ground cover without a tackifier seemed to
exhibit natural ground security and did not wash away. Straw lightly tacked
with a binder performed superbly.
Initially, large quantities of sediment were derived from the plots,
but with time the amount of sediment decreased. This was due to (1) armor-
ing of the soil surface by rain drop impact, (2) sheetwash and winnowing
away of sediment source and (3) progressive development of vegetational
cover. This suggests that the treatment applied is most useful during the
early critical time when vegetation has not yet become established. After
about 12 weeks, the grass cover became dominant and with lateral rhizome
development afforded maximum soil erosion protection on all plots.
With the onset of vegetation, it was possible to assess which of the
treatments afforded the best seed germination, plant growth and vegetative
cover. It was found that the straw and blanket products provided the best
environment for the establishment of vegetation. It appears that the
failure of the hydromulches to start dense germination of seedlings was
due to the inability of these products to provide sufficiently moist condi-
tions during dry periods, the cost of blanket treatment per area basis is
comparatively more expensive than the other treatments, which places an
economic constraint on the extent of application.
Throughout the study, the trends that were initially established
continued and although there was a decrease in the amount of sediment pro-
duced from each plot, the relative efficacies between treatments continued
to be maintained.
The consistent trends which were obtained suggest that the methods of
observation used were reliable and reflected treatment effectiveness.
All data derived from this study were transcribed to VM factors (see
page 41) for comparison with results of similar studies in the literature.
Results were found to be comparable to those of other studies.
-------
SECTION 2
INTRODUCTION
The loss of soil to the erosive forces of wind and water is accelerated
during times when a rapidly growing population places increasing demands on
the natural environment for housing, food, and energy. As an example, since
1974 surface mining for coal, sand and gravel has created over 4.4 million
acres of disturbed land in the United States, of which only 42% has been
adequately reclaimed (12). In addition, urban development and highway con-
struction have also been identified as major factors in .creating soil loss
conditions. Even short-term exposures of severely disturbed surface areas
of construction sites result in large soil losses. These erosive conditions
not only create situations conducive to soil destruction but, in addition,
the soil that becomes detached and transported increases the turbidity of
waterways, causes siltation of lakes and ponds, affects sedimentation of
major drainways and culverts and in some cases may blanket, bury and choke
the vegetation of periodically inundated areas.
Recently, an increasing awareness of these problems has led to the for-
mulation and design of a variety of chemical and physical soil stabilizers
that can be used to temporarily retard soil erosion while simultaneously
providing a suitable medium for the establishment of protective vegetation.
This report summarizes the results of a field study that was designed to
demonstrate the effectiveness of a variety of soil ameliorants, mulches and
tackifiers.
PURPOSE
The purpose of this investigation was to demonstrate the relative effi-
cacies of a number of soil stabilizing and revegetation treatments that are
commercially available for short-term stabilization of disturbed soil slopes.
The products under discussion are designed to initially shield the soil sur-
face from the erosive powers of rainfall and sheet runoff while promoting
the establishment of a perennial vegetative cover suitable for the permanent
stabilization of soil of the disturbed site. The specific objectives of
this study were:
(1) To demonstrate the soil stabilizing techniques or treatments that
are most effective in inhibiting soil erosion.
(2) To determine the efficacy of the treatments and the time required
to establish a vegetative cover.
(3) To ascertain the efficency and economic considerations of each
treatment tested.
-------
TEST SITE
For obvious reasons, the proposed area of study had to be of public do-
main, accessible to visitors, reasonably close to Columbia, South Carolina,
located within the Piedmont-type terrain and yet relatively secure from van-
dalism. The parcel of land that met all these criteria was found on a 15 acre
(6.07 hectare) tract of land that was made available for our use by the South
Carolina Department of Corrections. The project site is located north-north-
west of Columbia in Richland County, South Carolina (Figure 1) and borders
the southern extremity of the Southern Piedmont Province.
The site is comprised of three adjacent hills!opes with a predominantly
southern exposure (Figure 1). The slopes are moderate, ranging from 9 to 14%.
Prior to this study, the site was used primarily for pastureland and had a
well-developed grass cover. Figure 2 shows the appearance of the site in mid-
April, 1977 prior to the groundbreaking and slope modification that was nec-
essary for the study.
The soil type underlying the test site is the Herndon silt loam. This
soil is characterized by a loamy A horizon and yellowish brown and strong
brown clay B horizon that contain more than 30% silt. The A horizon is a silt
loam and averages 9 inches (22.8 cm) thick. The B horizon is a silty clay
loam, silty clay or clay containing 35 to 50% clay, more than 30 to 40% silt
and in some portions, fragments of partly weathered slate, shale or sericite
schist. The C horizon may be white with varying shades of brown and red de-
rived from the saprolite formed in the underlying slate, shale or sericite
schist bedrock. Soil development ranges from 40 to 70 inches (100 to 175 cm)
and the depth to unweathered bedrock is commonly more than 10 feet (30 m). In
some areas, 15 to 20% of the surface is covered by quartz pebbles and stones.
Although saprolite has developed to a depth of several feet, cores and frag-
ments of hard rock are common (2).
Herndon soils commonly occur on gently sloping to strongly sloping Pied-
mont uplands. Slope gradients generally range from 6 to 12% and are well
drained with medium runoff and moderate permeability. The average annual
rainfall for, the area is 46 inches (115 cm) and the average temperature is
64 F (17.8 C). Deep, well drained soils are characteristic of this area.
-------
Figure 1. Topographic map of the Broad
River Road Corrections Facility with test plot
locations, sites A, B and C.
feet
0 100 200 300
0
50
100
meters
-------
Figure 2. The project site is located within the Broad
River Road corrections facility. This photograph, taken
in mid-April before groundbreaking, is a view from the
center hillslope looking east.
-------
SECTION 3
DESIGN AND INSTALLATION OF THE TEST FACILITY
The rate of soil loss and revegetation of drastically disturbed sites is
a function of a complex interrelationship of independent parameters which in-
clude slope and soil characteristics, climate and precipitation. To assure a
valid comparative test, variations between plots were to be minimized so that
differences in measurements reflected variations in treatment effectivenesses.
Subsequently, a parameter reflecting treatment effectiveness could be identi-
fied and monitored and the efficacy of the various treatments ascertained.
To minimize variations inherent to large areas, such as soil type vari-
ability, microclimatic effects and slope orientation, it was decided to apply
the various treatments to small area plots located within one field site. In
'this manner, the soil response to each treatment could be simultaneously mon-
itored on small, contiguous and similar runoff plots as a function of precipi-
tation events. This technique permitted control of the variation among inde-
pendent parameters and test of the effect that each erosion-revegetation
treatment had on disturbed sjites.
GRADING AND ESTABLISHING RUNOFF PLOTS
In preparation of the site for treatment application, all existing vege-
tation was removed and all slopes were adjusted to a common dip. The site was
closely mowed with a standard bush hog and plowed to a depth of 5 inches (12.7
cm) with disc and chisel plows. This served to loosen the surface soil layers
and provide an initial kill of the existing vegetation. Following a prelimi-
nary survey, specific portions of the hillsides which would afford the steep-
est slopes yet still maintain uniformity of testing conditions were identified
among the three hi 11 si opes. 'Rectangul/ar sites that closely approximated the
12 to 15 per cent slope desired were staked off on each of the hillslopes.
The sites were designed to be 120 feet (36.6 m) wide with a 30 foot (9.15 m)
slope, striking North 85° East on the most easterly hillside; 150 feet (45.7
m) wide with a 30 foot slope (9.14 m) with a strike of North 60° East on the
central hillside and 90 feet (27.43 m) wide with a 30 foot (9.14 m) slope
striking North 70° East on the most westerly hillside.
Throughout all site areas, the slopes were initially formed with the use
of a hi-way motograder to approximate the 13% desired slope. A drainage di-
version ditch was dug along the top of the sites and 14-inch (35.5 cm)
-------
aluminum flashing was emplaced to fix the crest of slope. The area below the
test plots was also shaped to accommodate the installation of a network to
monitor and collect runoff (Figures 3a and 3b). During the grading process,
approximately 0.5 to 1.5 feet (15 to 45 cm) of the topsoil, along with most of
the remaining traces of previous vegetation, were removed from the sites. Fol-
lowing the grading, the ground was scarified to a depth of 5 inches (12.7 cm)
and disc-plowed again to break up the clay rich subsoil.
After the ground at each site was prepared by the procedure described
above, the sites were divided into plots 15 feet (4.57 m) wide using a 5-inch
(12.7 cm) vinyl plot border product. Each of these plots, in turn, was sub-
divided into 10 feet (3.05 m) and 5 feet (1.52 m) portions by an additional
piece of vinyl border, while maintaining a 30 feet (9.14 m) slope on each plot.
When the installation was completed, each test plot had two portions, a 5 foot
(1.52 m) and a 10 feet (3.05 m) width; each 30 feet (9.15 m) in slope length.
The edges of the vinyl plot borders were buried at precisely the desired slope
with a small border extending aboveground to prevent washover across plot
boundaries. The plots were then rototilled to a depth of 5 inches (12.7 cm)
(Figure 4). Using the vinyl plot border as a guide, the plots were hand raked
several times until the ground surface was graded to precisely the desired
slope (within a tolerance of 0.01 feet/10 feet; 0.1% grade). The hand rakings
also served to remove the large quantity of pebble to cobble sized stones from
each of the plots (Figures 4 and 5). Following this initial site preparation,
a total of 24 test plots was prepared; 8 at Site A, 10 at Site B and 6 at Site
C. At this point, each of the plots was ready for the installation of the
sediment and runoff monitoring devices.
-------
Figure 3a.
Figure 3b.
Figures 3a and 3b. Views of preliminary s\ope
modification of test sites.
-------
Figure 4. The vinyl borders, in addition to preventing
washover across plot boundaries, serve to divide the sites
into 15 feet (4.57 m) wide plots with 5"feet (1.52 m) and
10 feet (3.05 m) portions. The border was also used as a
guide in hand raking the plots to the final grade. All
plots were rototilled to a depth of 5 inches (12.7 cm).
Figure 5. An overview of the center hillslope (Site B)
with vinyl plot borders installed and final grading com-
pleted. At this site at this time, there are 10 test
plots awaiting the installation of the monitoring net-
work. Notice the gravel at the base of the plots, which
was removed from the plots by raking.
10
-------
DESIGN OF EROSION MONITORING SYSTEM
The sediment troughs to be used for the collection of surface runoff and
eroded sediment were designed to be emplaced at the base of the 5 foot (1.52 m)
wide portions of each test plot. The trough was fabricated to include a 6 inch
(15.24 cm) apron which was fixed to the lip of the trough and buried at the
base of the slope. In addition to gathering water and sediment, this lip also
served to eliminate seepage at the soil-trough boundary. This was an added
precaution in preventing runoff from bypassing the trough (Figures 6a and 6b).
In addition, the partial burial of the lip portion of the trough minimized the
erosion at the soil-trough interface. The trough had a volume of 2.5 cubic
feet (0.0708 cubic meters) which encouraged settlement of coarse material in
the trough. The overflow (i.e., when total runoff of the plot exceeded 2.5
cubic feet (0.0708 cubic meters) was forced to pass through a divisor plate
containing 5 holes of equal diameter. The divisor plate served to separate the
overflow into five equal volumes, allowing 1/5 of the total runoff from the
plot to be collected in a 35-gallon (132 liter) drum downslope. • Precise level-
ing of the plate after installation of the trough was afforded by having the
plate fastened to the trough by adjustable screws (Figures 6a and 6b).
A 3.5-inch (8.9 cm) 24-hour rainfall event, which has a recurrence inter-
val of 2 years in central South Carolina, will yield approximately 2 inches'
(5 cm) of runoff, as calculated from the S.C.S. (10,11), assuming average
antecedent moisture conditions and a disturbed untreated soil surface. Appli-
cation of treatments and the establishment of a vegetative cover should de-
crease the runoff coefficient and increase the capability of the collection
system to collect all of the runoff. Based on these anticipations, the runoff
collection system was capable of accommodating the flow'produced by 2 inches
(3 cm) of rain over the 150 square feet (13.94 m ) plot, before the 35-gallon
(132 1) barrel became full and overflowed.
A standpipe, the inlet of which could be rotated below water level, was
built into the trough in order to drain the troughs of water during the time
of sediment collection. To protect the material collected in the trough from
debris and direct rainsplash, a cover was placed over the open portion of the
trap (Figure 6b). A completed sediment and runoff collection system is shown
in Figure 7.
11
-------
Figure 6a.
Figure 6b.
Figures 6a and 6b. The troughs illustrated were installed at the bottom of
each plot. Notice the erosion due to flow under the trough (Figure 6a).
Figure 6b shows the assembled trough with apron cover and divisor plate. The
divisor diverts 1/5 of the overflow from the trough to a 35-gallon (132 1) drum
downslope, via the 1% inch (3.81 cm) pvc pipe which is connected to the center
hole in the divisor plate. Installation of the apron eliminated seepage under
the trough and assured that all of the runoff and sediment flows into the col-
lector.
12
-------
Figure 7. A complete erosion-runoff monitoring system.
13
-------
TREATMENT FOR VOLUNTEER VEGETATION
A major problem that we encountered in the simulation of drastically dis-
turbed soil conditions and which would radically affect the study results was
the natural readvancement of volunteer vegtation. In a controlled sitution,
the elimination of volunteer revegetation from the plots was critical in order
to compare the effectiveness of each soil stabilizing treatment. During the
tests, only that vegetation directly attributable to the soil treatment and
stabilization process was considered in plot evaluation.
As outlined'previously, 6 to 18 inches (15 to 46 cm) of soil
from the slopes during the grading process in order to expose the
zons and shape the hillside to the desired slope. This procedure
eliminate the remnants of vegetation; however, where the depth of
limited to 6 inches (15 cm) some vegetation tended to reappear.
were removed
subsoil hori-
did much to
excavation was
To correct this problem and surpress the volunteer vegetation, each of
the 24 test plots was treated with Round Up, a contact herbicide, at an appli-
cation rate of 2% gallons (9.46 1) of a 1% solution per plot. The
herbicide was sprayed evenly over each test plot whether or not vegetation was
present (Figure 8).
Figure 8. Two and one half (9.46 1) of a 1% solution*
of Round Up contact herbicide were applied to each
test plot' using a 3-gallon (11.35 1) capacity pump
sprayer.
14
-------
Upon contacting the leaves, the herbicide is absorbed by the plant and
after 7 to 10 days the plant is killed. In the soil, however, the herbicide
is readily dissipated and eventually degrades to innocuous levels. After the
10-day degradation period, a team of from two to five people covered each
plot and removed all plant remnants by hand weeding and raking (Figure 9).
Figure 9. All traces of grass above ground as well as
roots were removed by hand weeding and raking.
FERTILITY ANALYSIS
. The variation in fertility between plots was tested by analyzing nine
soil samples collected from a random grid pattern on each major hillside plot.
The samples were analyzed by the Clemson Agricultural Extension Service and
the results showed that the soil underlying the study site had low to average
contents of phosphorus and potassium ((3 to 30 pounds/acre (0.53 to 5.5 kg/ha)
phosphorus and 12 to 140 pounds/acre (2.2 to 25.7 kg/ha) potassium)). The cal-
cium content was consistently low for all test plots ((100 to 400 pounds/acre
(18.4 to 73.4 kg/ha)). Soil pH ranged from 4.6 to 5.3 and pH buffer from
6.40 to 7.25. Amendments of a 5-10-10 fertilizer at a rate of 500 pounds/acre
(91.78 kg/ha) and agricultural limestone at a rate of 2,000 pounds/acre (367
kg/ha) was deemed sufficient to compensate for the variability in fertility
and this mixture was applied to each plot during the treatment application.
15
-------
SECTION 4
EROSION-REVEGETATION TREATMENTS
TREATMENTS, DESIGN AND ANALYSIS
Soil stabilizing and revegetation treatments have a two-fold purpose;
first, short-term stabilization and protection of disturbed land and secondly,
to create an environment for the rapid establishment of a natural vegetative
cover. Most of the erosion treatments that were tested can be categorized into
three major types:
(1) mulch treatments
(2) chemical stabilizers
(3) blanket products
Each of these categories and their functions in soil stabilization are described
below.
Mulches
Mulch treatments serve mainly to absorb the erosive energy of rainfall
impact, the primary mechanism for soil detachment, and to reduce sheetwash, the
primary agent of transport (14). Mul.chps are also used and found effective in
increasing infiltration, reducing runoff, replenishing deficient soil mositure
and insulating the soil surface from extremes in temperature. Recent studies
showed that the application of a mulch to a soil cover results in the genera-
tion of a more thermally moderate and moist environment at the soil surface,
which encourages faster germination of seedlings (3,4).
Many materials have been used as mulches, including straw, hay, leaves-,
sawdust, wood shavings, manure, bagasse, paper scraps, cotton refuse and hard-
wood bark chips. At the present time, much work is being done in further
developing and refining suitable hydromulches from wood and paper fibers and
hardwood bark. Hydromulches are applied as a slurry with lime, fertilizer,
•seed, water and a tackifier (if used). A major advantage of hydromulches is
their ease of application. Modern hydroseeders with capacities of 3,000 gal-
lons (11,355.1) can apply mulches and treatments to cover more than 5 acres
(2.02 hectares) in about 30 minutes.
Chemical Stabilizers
The composition of chemical stabilizers varies from an asphalt emulsion
to a polymer latex or organic resin derived from plant gum or seaweed. Many
16
-------
of these products have an appearance and response similar to household glue.
Chemical stabilizers are used as a soil binder in lieu of mulch treatments and
as a tackifier in conjunction with mulch material. As a soil binder, these
treatments coat and penetrate the soil surface, which increases the cohesion
between soil particles. This surface bond not only reduces erosion by rain-
splash and sheetwash, but also serves to retard dust and wind erosion as well.
When used as a tackifier, these chemicals are employed to secure mulch material
in place by securing contact points between mulch particles and between the
mulch and the soil. In both methods of application, chemical stabilizers are
also designed to reduce moisture loss from the surface soil layers (3,4).
Blanket Products
Blanket products are broad surfaced materials or nettings that are sup-
plied in rolls and are applied in overlapping strips down the slope face and
stapled to the ground with 6-inch (15 cm) pegs. Most blanket products consist
of a type of netting that is interwoven with a mulch made of either paper, wood
shavings or some other suitable material incorporated in the webbing. Blanket
products afford the soil surface with all of the favorable attributes of a
mulch treatment and, in addition, are more stable and difficult to disturb if
properly installed. The blanket products, however, are more expensive to pur-
chase and the method of application, requiring manpower to roll and staple the
material, increases the total cost of installation.
TREATMENTS SELECTED FOR TESTING
Nineteen soil stabilizing and erosion control treatments were tested at
the specially prepared field sites. The soil treatments included: Four hydro-
mulches applied without a tacking agent, four netting products, eight chemical
stabilizers applied with a small amount of wood fiber mulch and four of the
stabilizers applied as tackifier on straw (Table l). Of the chemical stabi-
lizers used in this study, only one was an organic resin; the remainder were
of the concentrated liquid polymer emulsion type.
On each of the three hillslope sites one plot was selected as an un-
treated standard to serve as a control and a basis of comparison. On these
control plots, only the standard lime, fertilizer and seed mixture was applied.
In addition, two plots were left in the disturbed state and were not treated in
any way. The sediment yields derived from these control plots were used:
(1) to appraise the severity and degree of the erosion problem simulated
in the test.
(2) as a baseline of comparison with which to ascertain the relative
effectiveness of each of the treatments, and
(3) to check for variations in erosion rates among the three hillslopes
that may be attributable to inherent variations in soil types,
microclimatic environments and slope characteristics.
The study was designed so that the sediment yields derived from each
plot could be used to assess the comparable effectiveness of similar products
produced by different manufacturers as well as the relative efficacies of the
different types of erosion control and revegetation treatments.
17
-------
TABLE 1. LIST OF VARIOUS TREATMENTS MONITORED FOR EFFICIENCY OF
EROSION CONTROL AND REVEGETATION ON DRASTICALLY DISTURBED SOIL SLOPES
Item # Plot # Treatment
4 hydromulches
1 B-17 Conwed
2 A-6 Superior fiber
3 A-4 Silva fiber
4 B-12 Pulch*
3 netting products presently available
5 A-l Jute netting
6 B-9 Hold gro
7 A-5 Excelsior blanket
8 tackifiers presently available, used as pre-
scribed with a standard wood fiber mulch
8 B-10 Curasol AK and wood fiber mulch
9 B-18 Terra Tack III and wood fiber mulch
10 A-2 Aerospray (or DCA 70) and wood fiber mulch
11 C-20 Crust (500) and wood fiber mulch
12 C-22 Dow mulch binder and wood fiber mulch
13 A-3 Petroset SB and wood fiber mulch
14 B-13 Perma soil and wood fiber mulch
15 B-ll Genaqua and wood fiber mulch
Straw mulch tested with 3 chemical stabilizers
and 1 net stabilizer
16 A-7 Vexar plastic net over straw
17 C-21 Curasol AK and straw
18 C-19 Terra Tack II and straw
19 B-15 Dow mulch binder and straw
20 A-8 Untreated standard
21 B-14 Untreated standard
22 C-24 Untreated standard
23 B-16 Control
24 C-23 Control
*Effective January, 1978, this product, designated in this report as
"Pulch", has been renamed by Rumose Products Company as "Spra-mulch",
18
-------
APPLICATION OF TREATMENTS
In order to insure valid comparisons of the variety of materials and tech-
niques, the application of the selected treatments to the respective test plots
had to be done in accord with the application rates prescribed by the manufac-
turer. In addition, a reliable technique for application of each treatment to
the test plots had to be assessed. The necessary information and guidelines
for application were obtained from representatives of each product company. Re-
quests were made for:
(1) a detailed price listing for a comparative cost analysis
(2) recommended application rates for the conditions at the test site
(3) necessary special instructions for dilution, mixing or application
Based on the data provided by the companies, the following guidelines for appli-
cation rates were formulated.
Application Rates
Application rates for the selected treatments were needed which would
suitably test the efficacy of each treatment while applying neither too much
nor too little. At the same time, the rate selected should produce ranges of
sediment yields between treatments that are sufficiently large so as not to be
seriously affected by the small errors in sampling and data analysis. Further,
by designing treatments in accord with optimum application rates, the cost of
materials and application will be realistic and could be used to assess treat-
ment efficiency as a cost-benefit analysis.
Rates of application were devised that considered both the cost per acre
treated and the rates recommended by the manufacturers. The application rates
chosen for testing are listed in Table 2. Also, each treatment was applied
with standard lime, seed and fertilizer amendments in accord with the specifi-
cations listed in Table 3.
Application Technique
Hydroseeding—
2 Due to the relatively small size of the test plots (450 square feet; 41.8
m ), a conventional hydroseeder with a 500 to 800 gallon (1,890 to 3,028 1) '
capacity and a fire hose-type nozzle capable of broad application patterns
could not deliver the materials with the precision required for this study and
was deemed impractical. Further, because of the residual that remains in the
tank after each application, the amount of products that would be applied as
a slurry would be very difficult to measure if the large hydroseeders were used.
To accommodate the needs and requirements of applying small volumes of
treatments in precise manners, a precision laboratory hydroseeder was borrowed
from the United States Department of Agriculture Forest Service at the Forest
Products Marketing Laboratory, Princeton, West Virginia (Figure 10). This hy-
droseeder had an 8-gallon (30.28 1) capacity wedge-shaped chamber seated over
a gasoline powered pump. The pump serves not only to drive the slurry through
a fan-type nozzle, but to recirculate the slurry through the chamber to assure
19
-------
TABLE 2. APPLICATION RATES OF MULCHES AND TACKIFIERS
USED IN THIS STUDY
MULCH COMPARISON
1,200 Ibs/acre ((220 kg/ha)(12.4 Ibs/plot))
TACKIFIER COMPARISON
Liquid binders
50 gal/acre ((76 l/ha)(0.52 gal/plot))
Over either (1) wood fiber mulch at 500 Ibs/acre ((91.78 kg/ha)(5.17
Ibs/plot))
or (2) straw mulch at 3,000 Ibs/acre ((550.7 kg/ha)(31
Ibs/plot))
Solid binders
-Terra Tack II-
45 Ibs/acre ((8.26 kg/ha)(0.47 Ibs/plot))
Over straw mulch at 3,000 Ibs/acre ((550.7 kg/ha)(31 Ibs/plot))
-Terra Tack III-
40 Ibs/acre ((7.34 kg/ha)(0.41 Ibs/plot))
Over wood fiber mulch at 500 Ibs/acre ((91.78 kg/ha)(5.17 Ibs/plot))
TABLE 3. STANDARD SEED AND FERTILIZER APPLICATION RATES
USED IN THIS STUDY
Seed Mixture
Kentucky 31 fescue
Bermuda (Common)
Bahia (Pensacola)
Rye Grass (Annual)
Fertilizer (5-10-10)
Lime
Per Acre
Per Hectare
Per Plot
50 Ib.
15 Ib.
15 Ib.
10 Ib.
500 Ib.
,000 Ib.
9.18 kg.
2.75 kg.
2.75 kg.
1.84 kg.
91.78 kg.
367.1 kg.
0.52.1b
0.16 Ib
0.16 Ib
0.10 Ib
5.17 Ib
20.66 Ib
20
-------
mixing of the product and amendments and the uniform distribution of each in the
slurry. In trials off the test area, we found that a 4 to 6 per cent solids
slurry could be easily accommodated by the hydroseeder. However, before the
treatment mixture could be recirculated, it was necessary to thoroughly hand mix
the product for uniform response characteristics. Because of the high dilution
rates and to insure correct application rates, each plot was treated with 3 to
6 loads of the hydroseeder. Each load was applied over equally subdivided plots
with some overlapping to assure uniform dispersion of products. A plastic drop
cloth was placed along the sides of the plot to prevent splash onto the adjacent
plot and to insure that a treatment was confined to each plot (Figure 11).
Figure 10. A Reinco laboratory scale hydroseeder was used
for application of the treatments. It has an 8-gallon
(30.28 1) wedge-shaped chamber over a gasoline powered pump
used for propulsion and recirculation.
21
-------
Figure 11. Applying hydromulch to a test plot in 4 ap-
plications of the hydroseeder. Notice the plastic drop
cloth at the plot border to prevent splashover and con-
tamination of the adjacent plot.
Straw and Blanket Products—
Application of straw and blanket products was done manually to insure an
even distribution of material over the test plot. The lime, fertilizer and
seed were applied using a drop seeder, which assured an equal distribution of
material (as seen in Figure 12).
•In the application of the blanket products, the material was rolled over
the plot, overlapped and stapled as per directions (Figure 13). The straw
mulch was dispersed by hand over the lime, seed and fertilizer. Subsequently,
the tacking agents were applied over the straw, using the hydroseeder.
22
-------
Figure 12. Lime and fertilizer were applied using a man-
ual drop seeder to insure even distribution.
Figure 13. Application of excelsior blanket to the test ,
plot on the standard lime, seed and fertilizer application.
23
-------
SECTION 5
PHOTOGRAPHIC REPRESENTATION OF TREATMENT RESPONSE
INITIAL APPEARANCE AFTER APPLICATION (9/25/77 THROUGH 10/1/77)*
All treatments were applied during the six-day period from September 25,
1977, to October 1, 1977. Photographs of a representative group of the treat-
ments at the time of application are shown in Figures 14 through 23. Figures
14, 15, and 16 show the three blanket products just after application. Care
was taken during application to secure staples firmly to the ground to provide
good ground coverage.
Figure 17 shows Plot A-7, which contained a straw mulch covered by a plas-
tic net. It was found that hand dispersal of the straw mulch at a rate of
3,000 Ibs/acre (550.7 kg/ha) was sufficient to achieve a good and even ground
coverage. When the straw was tacked with Dow mulch binder and Curasol AK, there
were distinct broken contact points between straw fibers when separated. This
effect, however, was not found with the Terra Tack stabilizer. The Terra Tack
product used in this study came as a powder with two components. It is pos-
sible that the two components were not sufficiently mixed in the laboratory
scale hydroseeder, which prevented the full activitation of the components.
Plots A-4, B-17, and B-12 (Figures-18, 19, and 20) were treated with hy-
dromulches. The wood and paper fiber hydromulches have a rich green color
which at the time of application delineates and identifies the treated areas
and is very useful during application when trying to achieve an even and com-
plete coverage. As little as 30 hours later, however, the colors had been sig-
nificantly bleached by the sun (Figure 19). The degree of uniformity of cover-
age afforded by a 1,200 Ibs/acre (220.3 kg/ha) application rate of the tested
hydromulches using the laboratory scale hydroseeder is evident in these figures.
Plots A-3 and C-20 (Figures 21 and 22) show only two of the tackifiers
used which were tested at a rate of 45 gal/acre (68.8 1/ha) with 500 Ibs (226.8
kg) of wood fiber mulch per acre (the initial appearances of all eight plots
*In some cases, the dates will be numerically depicted in order to facil-
itate photograph identification which incorporates a similar date format.
24
-------
testing tackifiers were identical). When the ground dried after application of
these treatments, only a faint yellow tinge betrayed the presence of the treat-
ment. When dry, these tackifiers formed a crusty layer at the soil surface.
The three untreated plots were left in a slightly disturbed condition af-
ter application of the standard lime, fertilizer and seed mixture and a vigorous
hand raking (Figure 23). In addition, two control plots were vigorously hand
raked and received no treatment or seed of any kind.
25
-------
Figure 14. Plot A-l on 9/25/77, following application
of jute netting.
Figure 15.. Plot A-5 on 9/25/77, following application
of Excelsior blanket.
26
-------
Figure 16. Plot B-9 on 9/25/77, following application
of Hold gro erosion control fabric.
Figure 17. Plot A-7 on 9/25/77 following application
of straw mulch and Vexar net.
27
-------
Figure 18. Plot A-4 following application of Silva wood
fiber mulch.
Figure 19. Plot B-17 following application of Conwed
wood fiber mulch approximately 30 hours later after the
sun had dried and bleached the mulch.
28
-------
Figure 20. Plot B-12 following application of Pulch
paper hydromulch.
Figure 21. Plot A-3 following application of Petroset
SB chemical stabilizer and wood fiber mulch at a rate
of 500 Ibs/acre (91.78 kg/ha). The treatment is ex-
tremely difficult to see after it dries.
29
-------
Figure 22. Plot C-20 following application of Crust 500
chemical stabilizer and wood fiber mulch at a rate of
500 Ibs/acre (91.78 kg/ha). It is very difficult to see
any trace of the treatment.
•'• " •«;£-•- ' -*??-,*•"- -f' >WV'
--•••'•%v.:^l,---.'^
N -fe^;^-.-^ \
*&$%^£'^~^^:
Figure 23. Plot A-8 is an untreated plot. Only the stan-
dard lime, fertilizer and seed mixture were applied to
the untreated plots.
30
-------
TREATMENT RESPONSE THROUGH 10/28/77
Although seedlings appeared on all plots two to three weeks after the ap-
plication of treatments was completed, they appeared first, and with greater
abundance, on the plots treated with straw and blanket products. This was prob-
ably due to the heavier ground cover afforded by the treatments which retained
surface moisture to a greater degree during the periods between rainfall.
An unusually large amount of rain fell during the period between October
1 to October 28, 1977. During this time, it rained on eight days ((with a total
precipitation of 4.83 inches)(12.27,cm)). The most significant storm was a 3.83
inch (9.73 cm) rainfall in 36 hours. It was during this period, just after ap-
plication of the treatment and before establishment of .a suitable vegetative cov-
er, that the soil was most susceptible to erosion. During this time, the treat-
ments were taxed to their limit in terms of protecting the soil from the erosive
forces of wind and water and underwent their most rigorous test.
The photographic documentation of the response of the test plots during
the entire test period is shown in Appendix A. In this graphic array, the plots
are shown in order, plots A-l through A-8 in Plates 1 through 8; B-9 through
B-18 in Plates 9 through 18 and plots C-19 through C-24 in Plates 19 through 24.
The photographs shown in each plate labeled a, b, c...depict the plots at dif-
ferent times during,the test period.
Photographs on Plates la, 5a, and 9a show the plots that were used to test
the three blanket products; jute, Excelsior blanket and Hold gro. The jute
blanket (Plate la) was affected by shrinkage due to repeated wetting and drying
from rain. This continous shrinking put a strain on the ground staples, which
pulled apart and left gaps of exposed soil between strips. In these plots,
the vegetative growth was 'found to be rather thin and concentrated only in low
spots where seed and moisture may have accumulated. The Excelsior blanket
(Plate 5a), in contrast, shows no obvious shrinking effects due to the rain and
has a good stand of grass. The Hold gro blanket (Plate 9a) initially enhanced
the start of a good vegetative cover, but through time this product tended to
be lifted off the ground by the growing seedlings. Prior to the heavy down-
pour (3.83 inches in 36 hours) which occurred on the 25th and 26th of October,
an estimated 30 to 40 per cent of the blanket area was held off the ground
by the underlying grass. The intensity of the rain, however, drove parts of
the blanket back to the ground. In spite of this beating down by the rain,
small patches of this tenting effect were still visible after the rainfall
event (Plate 9b).
The straw mulches in general showed the capability of initiating a good
vegetative cover. No displacement of the straw mulch by the high rainfall in-
tensity was discerned on any of the straw test plots, whether tacked by Vexar
net (Plate 7a) or chemical stabilizer (Plates 15a, 19a, and 21a). The straw
mulch tacked by Terra Tack II still showed no cemented contact points between
straw fibers and the fact that this straw was not disturbed after the intensive
rainfall of October 25 and October 26 indicates that the intertwining of straw
fibers is sufficient in itself to stabilize the mulch on moderate
31
-------
slopes (such as in this test). Some volunteer growth of rye grass was derived
from seedheads inherent in the straw mulch. This is intrinsic and is to be
expected when using straw. This volunteer growth is detrimental only from an
aesthetic standpoint when selective seeding is required for locations designed
for special appearance or visual effect.
The results of the four hydromulches tested are shown in Plates 4a, 6a,
12a and 17a. The vegetative cover developed on these plots was relatively poor
and was concentrated mostly in slight depressions where seed and moisture tend-
ed to collect. The hydromulches applied alone (with no tacking agent) did not
adhere to the soil surface and were easily dislocated during the intense rain-
fall of the period in discussion. Agglomerations of the fiber mulches were
found oriented transversely to the slope where the mulch had washed or rolled
down the slope and collected on pebbles and small stones (Plates 4b and 17b).
The Pulch paper mulch, in addition to the dislocations, was also washed out,
with large amounts found 10 to 15 feet (3 to 5 m) beyond the plot.
The plots which tested the response of the 8 chemical stabilizers showed
very poor development of vegetation during this period. Plates 2a and 2b show
the Aerospray test plot. An inadvertent blockage in the drainage diversion
ditch above the test plots caused water to spill over and erode a gulley
through the demonstration portion of the test plot (fortunately, the sediment
collection system was not affected). Upon closer inspection, a thin crusted
layer 1/16 to 1/8 inch in thickness was observed to have formed where the
tackifier had penetrated the soil, producing a hard surface layer resisting
erosion. Similar crusting was found to have been developed in the other plots
that were stabilized with tackifiers (as seen in Plates 3a, 20a, and 22a).
When the tacking agents were added to the mulches,there was a smaller
downs!ope transport of the mulch. Some, however, still migrated to the base of
the test plots (Plates lOa and lla), and in some cases to a greater extent
(Plate 13a).
The three plots that were seeded, limed and fertilized but untreated
showed only traces of seed germination (Plates 8a, 14a and 24a). Erosion was
most severe on the plots that showed the development of minor channelization
of flow, which effectively increased erosion in several locations within that
area.
TREATMENT RESPONSE FROM 10/28/77 THROUGH 11/28/77
During this one-month period, there was much less precipitation. The
vegetation developed quite rapidly on the plots where straw treatments or
blanket products had been applied. However, for the plots that were treated
with mulch and chemical stabilizers, the vegetative cover was more sparse.
This becomes especially apparent when comparing the plots treated with Aero-
spray (Plate 2b) and the Crust 500 (Plate 20b) chemical stabilizers with the
more successful plots treated with either Hold gro (Plate 9c), Excelsior blan-
ket (Plate 5b), or any of the straw mulches (Plates 7b, 15b, 19b or 21c).
During this period, development of the vegetative cover took place pri-
marily through further growth of the small seedlings which had sprouted ear-
lier. An absence of new germination was apparent. This was best documented
32
-------
by observations of the plots where sparse vegetation had matured, leaving large
areas unprotected. In these cases, the seedlings grew bigger and, with the ex-
ception of taller stands of grass, no new ground cover developed.
TREATMENT RESPONSE FROM 11/28/77 THROUGH 12/15/77
During this 17-day period, very little precipitation took place, with to-
tal rainfall accumulation of 1.9 in. (4.83 cm) coinciding with the shortest
observation period. The total vegetative cover development still follows the
established trend of better cover for the plots treated with blanket products
and straw treatments; however, the plots treated with mulch and chemical sta-
bilizers showed increased vegetative cover through lateral rhizome development.
During this period, the sparse vegetative cover spread laterally over the inter-
vening bare areas and began to develop a more uniform blanket cover. This can
be noticed especially for Aerospray (Plates 2b and 2c), Petroset (Plates 3b and
3c) and Genaqua 743 (Plates lib and lie).
TREATMENT RESPONSE FROM 12/15/77 THROUGH 1/23/78
During this 6-week period, the test plots received the largest accumula-
tions and highest intensity rain of the entire period of investigation. The
established vegetation continued to develop laterally, causing less and less
variation in vegetative cover between the plots with varying treatment types.
During the latter part of this period, winter temperatures killed the es-
tablished grass cover. With this consideration in mind, and with the fact that
the period for observing the most sensitive differences in vegetative cover at-
tributable to the treatments had passed, any further observations would be a
reflection of the natural development of vegetation and not of treatment re-
sponse. In addition, those plots that had a poor initial germination and con-
tained sparse vegetation would be expected to produce additional vegetational
growth due to lack of competition (in a relative sense) between plants already
established. In contrast, the plots with a good grass cover would be expected
to produce additional vegetative growth at a lesser rate due to competition of
existing plants for food and moisture. Hence, through time the visual differ-
ences between each plot would become less apparent and eventually more uniform
in cover. For these reasons, the visual assessment of plot response was ter-
minated during the early part of 1978.
33
-------
SECTION 6
SEDIMENT SAMPLING PROCEDURE AND ANALYSIS
SAMPLING
The sediment yield monitoring network was designed and installed to func-
tion with a minimum of maintenance. Sediment yields were monitored and meas-
ured after each rainfall event which was deemed to cause a significant and meas-
urable amount of erosion. Following a rainfall event, a team would visit each
plot and inspect the ground surface for a visual appraisal of the treatment's
response to the rainfall. Appropriate field notes were made and annotated for
inclusion in an evaluation of overall treatment response. In addition to the
field inspection, the team also examined the sediment troughs and runoff bar-
rels to see how much each had become filled with sediment. At a time when it
was felt that the next storm event would overflow the collection chambers, the
sediment yield from each plot was collected and measured by the following tech-
nique:
(1) the coarse sediment which had accumulated in the trough was scraped
from the trap and collected in a sample bucket (Figures 24a and 24b).
(2) the runoff containing the fine grained sediment and which accumulated
in the barrel positioned downslope of the trap was agitated and a
depth integrated sample of at least 12 'fluid ounces (300 ml) was col-
lected.
(3) the depth of water collected in the barrel was measured by a dip
stick to determine the volume of water.
(4) the barrel was emptied and the monitoring network reassembled in
preparation for the collection of sediment yield of the next rain-
fall event.
LABORATORY ANALYSIS
The coarse sample fraction collected from the trough was dried and weighed
in the laboratory (Figure 25). The dip samples collected from the barrels were
analyzed for suspended solids using the standard United States Geological Sur-
vey method outlined in T.W.R.I. (7). Basically, an aliquot of sample was fil-
tered through a preweighed 0.45y Millipore filter. The filter was then dried
and weighed to measure the weight of suspended material that was filtered from
the aliquot of sample. By noting the volume of water contained in the barrel,
the weight of sediment filtered from a volume of water could be easily trans-
lated to yeild of fine grained sediment produced by each plot in response to
a particular rainfall event.
34
-------
Figure 24a.
Figure 24b.
Figures 24a and 24b. Water is drained from the trough by
gradually lowering the standpipe (a). The sediment is
then scraped from the trough and collected (b).
35
-------
Figure 25. The laboratory was equipped for analysis of
suspended sediment samples with Millipore filtering ap-
paratus. The laboratory was also equipped with a large
oven and large laboratory scales for measuring dry
weight of coarse sediment scraped from traps.
36
-------
SECTION 7
SEDIMENT YIELD DATA
SEDIMENT YIELD COMPARISON
As discussed previously, the frequency and interval of sediment sampling
was dictated by the frequency and duration of rainfall. The plots were contin-
ually inspected during the field visits and the sediment collection troughs were
routinely examined to determine if a measurable amount of sediment had accumu-
lated in the traps. When a sufficient volume of sediment had accumulated, a
collection phase was planned.
During the initial part of the study and immediately following application
of the treatments, the soil surface was at the most disturbed condition and only
the protective and/or bonding effects of the treatments protected the soil sur-
face from erosion. Consequently, it was during this critical time that each
soil erosion treatment was subjected to its most severe test. Accordingly, the
sediment yield data gathered during the first several months reflects best the
efficacy of the treatment in preventing surface soil erosion. As outlined in
the first part of this report, the soil treatments are designed to afford the
soil with a protective coating while at the same time providing a suitable en-
vironment for vegetation germination and growth. Initially, the treatments af-
ford maximum protection. Through time, however, the vegetational cover even-
tually takes over and provides the ground cover for perpetual soil stabilization.
In some cases, the vegetational development is accompanied by soil amelioration
or mulch deterioration (in the products which will degrade with time).
The initial collection phases described below were made during the time
predating the full establishment of vegetation and reflect conditions under
which the soil was stabilized only by the treatment. Although some germination .
and vegetational growth had occurred during this period, the interfingering -
root network had not yet developed and, for all intents and purposes, did not
afford the soil surface with a fully protective cover.
The first sediment sample collection was performed on October 27, 1977,
approximately 4 weeks after application. A total of 4.83 inches (12.27 cm) of
rainfall had fallen during the period, including a high intensity of 3.83 (9.73
cm) in a 36-hour period on October 25 and 26. (Figure 26). The sediment yields
for this period are summarized in Table 4. As can be seen, erosion from the
untreated (U) and untouched control plots (X) were rather significant, with
yields ranging from 3.25 to over 4.0 tons/acre (1,191 to 1,466 kg/ha) for the
period. When projected to annual sediment yields, these quantities seemingly
represent sizable sediment losses. However, it must be kept in mind that this
37
-------
3r
CO
OD
h-
c_> i
u '
10 20
OCT
SAMPLED DAYS
K
10 20
NOV
Jl
To ~Td
DEC
75 - 25
JAN'
10
FEB
(M
UJ
Figure 26. Rainfall intensity and distribution occurring in area of
test plots. Days during which sediment samples were collected are also
indicated.
-------
sediment yield was derived from the plots during a 27-day period, with the vast
majority of erosion and sediment yield taking place during the two days of high
intensity rainfall.
A number of treatments were very successful in limiting the amount of ero-
sion. The blanket products (code B), as well as the straw treatments (S), were
shown to be quite effective in preventing soil erosion. Also, plots treated with
several chemical stabilizer treatments showed good results. While some plots
treated with chemical stabilizers did relatively poorly; with sediment yields
ranging from 0.8 to over 2.2 tons/acre (293 to 806 kg/ha). The plots treated
with hydromulches had sediment yields around 0.9 tons/acre (329.9 kg/ha) with
one anomalously bad reading. In these high sediment yield cases, hydromulches
were used with no tacking agents (Table 4).
Following a heavy rain, a large amount of the untacked mulches were found
to have been washed from the plots and collected in the sediment traps. This
was the most obvious deficiency for the paper confetti hydromulch used in this
study. The wood and paper fiber hydromulches were also found in large quantities
in the traps and distinct evidence of the downslope movement of these mulches
was found in the transverse ribs of mulch that were formed against pebbles and
ground irregularities (as discussed in the previous section). Based on these
observations, it is recommended that hydromulches be used in conjunction with
a tackifier to obtain maximum slope protection and stability.
The next sediment collection was performed on November 11, 1977, only two
weeks later. Precipitation during this period totalled only 0.84 inches (2.13
cm), with 0.27 inches (0.69 cm) falling on October 28 and 0.36 inches (0.91 cm)
on November 5 (Figure 26). The sediment yields for this period (Table 4) are
at least an order of magnitude lower than the previous sampling period. Al-
though this is in part attributable to the lesser amount of rainfall and lower
intensities, sediment yields were expected to reduce drastically due to a de-
pletion in the amount of soil readily available to erosion as the surface be-
came compacted and reworked by rainfall. In addition, the stabilizing effects
of the establishment of vegetation were becoming more apparent. By this time,
a substantial grass cover had developed on the straw and blanket product plots,
and the mulch and tackifier test plots had begun to show a much more even dis-
tribution of young seedlings than was apparent on October 28, 1977.
Although the total sediment yields were much lower than the previous
sampling period, the relative sediment yields from each plot showed the same
proportions. The treatments which had the least stabilizing effects during the
initial sampling period continued to show the highest sediment yields.
Sediment samples were again collected on December 19, 1977. The total
precipitation for the period from November 11 through December 19 was 2.60
inches (6.6 cm) with the majority of the rain falling on November 29 ((0.90
inches)(2.29 cm)) and December 5 (((0.63 inches)(1.6 cm)(Figure 26))). In
spite of increased rainfall, the total sediment yields for this period (Table
4) were yet still lower, most probably due to the advancing and continued
growth progress of the revegetation. There is a noticeable decrease in the
variation of sediment yields for this sampling period, which may be due to the
39
-------
TABLE 4. SEDIMENT YIELD DATA FOR ALL PLOTS
SEDIMENT YIELD (TONS/ACRE)* TOTAL YIELD
CODE PLOT 10/27/77 11/11/77 12/19/77 2/10/78 (TONS/ACRE)* VM FACTOR**
B A-l 0.388 0.028 0.016 0.023 0.455 0.110
B A-5 0.302 0.016 0.008 0.032 0.358 0.086
B B-9 0.524 0.022 0.020 0.071 0.637 0.147
T A-2 0.953 0.103 0.098 0.403 1.557 0.378
T A-3 1.095 0.120 0.075 0.200 1.490 0.361
T B-10 0.318 0.030 0.036 0.126 0.510 0.118
T B-ll 0.238 0.022 0.013 0.065 0.338 0.078
T B-13 1.479 0.071 0.048 0.053 1.651 0.381
T B-18 2.261 0.144 0.091 0.129 2.625 0.607
T C-20 0.992 0.076 0.056 0.294 1.418 0.226
T C-22 0.806 0.061 0.056 0.243 1.166 0.185
M A-4 0.897 0.066 0.040 0.095 1.098 0.266
M A-6 2.376 0.239 0.087 0.182 2.884 0.699
M B-12 0.979 0.054 0.046 0.132 1.211 0.280
M B-17 0.814 0.049 0.040 0.115 1.018 0.235
S A-7 0.375 0.020 0.011 0.050 0.456 0.110
S B-15 0.057 0.004 0.007 0.023 0.091 0.021
S C-19 0.567 0.025 0.016 0.070 0.678 0.108
S C-21 0.514 0.029 0.022 0.059 0.624 0.099
U A-8 3.468 0.270 0.127 0.257 4.122 0.999
U B-14 3.252 0.185 0.093 0.088 3.618 0.877
U C-24 3.745 0.321 0.872 - 4.938 0.785
X B-16 3.516 0.180 0.133 0.500 4.329 1.000
X C-23 4.038 0.309 0.664 1.276 6.287 - 1.000
CODE: B-blanket products; T-tackifiers; M-hydromulches; S-straw; U-untreated, but seeded
with lime and fertilizer; X-no treatment or seed (untouched).
PLOT: Letter signifies hillslope and number, plot.
*To obtain kilograms/hectare, multiply these values by 366.5.
**VM factor is the ratio of sediment yield from the test plot to the sediment yield from
the control plot; the lower the ratio, the more effective the treatment. X(A); the
yield of sediment from the control plot A was estimated from Figure 27 to be 4.124
tons/acre.
-------
lateral development of the grasses in the initially poor test plots, as noted
previously.
Precipitation increased drastically in the following weeks, with several
events of high intensity and significant accumulations, including two storms
with 2.5 inches (6.35 cm) of precipitation. Total rainfall for the 8-week pe-
riod was 9.14 inches (23.22 cm) and the new sample collection'was done on Feb-
ruary 10, 1978. By this time, however, revegetation had become well established
and the more successful treatments had produced a formidable vegetative protec-
tion for the soil. Sediment yields were only slightly higher than the previous
sampling period which had a much lower rainfall and erosion potential. The data
from samples collected on February 10 also show much lower sediment yields than
the first sampling period which also had a lower rainfall erosion potential.
The lower sediment yield with time is due to a decline in the availability of
sediment as compaction of the soil takes place and the winnowing out of fines,
leaving a coarse layer, which armors the surface. This can best be exempli-
fied by comparing the control plots (X); B-16 and C-23 for the first (10/27/77)
and last (2/10/78) sampling periods (Table 4). Note, however, that the trends
in sediment yield (reflecting the efficacy of the various types of treatments)
continue to retain similar patterns with time. Consistently, the plots with the
straw and blanket products had the lowest sediment yields and the plots treated
with mulches and tackifiers were progressively less successful. These trends
support the contention that treatments which are initially effective in reducing
erosion are also more effective in establishing a lush vegetative cover and
permanent soil stabilization.
Soil conservationists now employ a new parameter in the Universal soil
loss equation, the VM factor (13). The VM factor represents a vegetative or
maintenance erosion control practice and is a total soil loss ratio expressed
as a decimal. Values range from 0.0 to 1.0, where a value of 0.0 means the
erosion control practice has eliminated all erosion and a VM factor of 1.0
means the practice has done nothing to reduce the erosion from that of a dras-
tically disturbed condition.
To compare the effectiveness of treatments, all total sediment yields
shown in Table 4 were converted to a VM factor. This factor is calculated as the
ratio of the sediment yield of the test plot to the sediment yield for the un-
treated and untouched control plot (coded X) on that hillslope. These conver-
sions served to filter out the minor variations in soil, insulation or weather-
ing conditions among the hillslope test sites. In addition, the VM factors
could be used to facilitate comparisons of treatment effectiveness among the
test plots and compare the results of this study to other similar investigations
performed under different soil and climatic conditions (discussed in a later
section.
To discern variations in sediment yield from each hillside, the total
sediment yields derived from each treatment were plotted with respect to the
hillslope on which that test plot was located (Figure 27). The plots treated
with blanket (B) and straw (S) products still show the best results. The plots
treated with hydromulches (M) produced more sediment than most of the plots
treated with chemical stabilizers (T). When compared to the untreated (U) and
41
-------
ro
5.0
a
4.0
c
o
UJ
>3.0
LLJ
5
LU
2.0
1.0 -
0.0
EXPLANATION
B = Blanket products
T = Tackitiers
M = Mulches
S = Straw
U = Control plot with seed,
lime and fertilizer
X = Disturbed; untreated plot
B
A
A
B
B
B
A
B
B
B
fi
8
A
B
M
A
B
A'
B
HILLSLOPES
A, B &C
U
Figure 27.
TREATMENT CODE
Sediment Yields Grouped by Treatment Types
-------
control plots (X), however, all treatments had some beneficial effect in sta-
bilizing the soil.
An evaluation of the sediment yields for the untreated and control plots
(Table 4 and Figure 27) derived from the three hillslopes shows a consistent
variation that reflects a heterogeneity of soil types underlying the three sites.
Soil losses from the plots located on the C hillslopes were consistently greater
than those on the A and B hillslopes. This was due to the higher clay content
soil underlying the C hillslope and was reflected by an increase in soil erosion
and sediment yield. During a field inspection, we noted that the attempts to
revegetate the untreated test plot at hillslope C were not successful. It ap-
peared that following a rain, most of the seed had washed away and that little,
if any, ground stabilization had taken place. However, for the treated plots
very little, if any, difference in sediment yields is discernible for similar
treatments on the A and B hillslopes (Figure 27). This similarity in sediment
yields shows that the treatments were effective in stabilizing the fine grained
component of the soil horizons and retaining this portion on-site.
TREATMENT EFFICIENCY AS A FUNCTION OF GRAIN SIZE
Due to the nature of the monitoring facilities, all sediment collected in
the runoff barrel downslope was segregated from the coarse fraction by a mech-
anism common to each plot. Consequently, the concentration of fine sediment
found in each of the runoff barrels provided a relative assessment of the ef-
ficiency of the treatments in protecting the fine grained fraction of the soil.
Table 5 shows the concentration of fine sediment derived from each plot
as it was collected in the runoff barrels. The trend in the fine grain sediment
yields collected from each plot decreases significantly with time as the vege-
tation forms a protection for the soil surface. The fine grain sediment col-
lected on October 27, however, was derived from plots that did not yet have the
fully developed vegetational cover and were protected only by the treatment that
was applied. In essence, then, the data summarized in Table 5 reflect the
treatments' ability to protect the fine soil fraction and provide a good indi-
cation of the relative soil stabilization efficiencies of each.
As would be expected, runoff from the untreated and control plots (U and
X) had high concentrations of suspended material, with the control plots lo-
cated on hillside C having the highest; most likely attributable to the higher
clay content of the soil found at this location (discussed in previous sec-
tion). Several of the plots treated with tackifiers, including Curasol AK (B-10)
and Genaqua (B-ll) yielded low concentrations of fine grained material. The
Crust 500 (C-20) and Dow (C-22) treated plots also yield low concentrations when
considering the plot locations to be on the C hill slope and in a slightly finer>
material. The Terra Tack (B-18) did not afford good protection and the plot
with this treatment yielded a very high concentration of fine grain material.
As indicated previously, the Terra'Tack was not properly agitated in the hydro-
seeder and quite probably the necessary mixing required to form a bonding mate-
rial did not take place. Notice that the straw treatment tacked with Dow
mulch binder (B-15) produced the lowest recorded fine grained sediment concen-
tration, yet the straw tacked with Terra Tack (C-19) produced much higher con-
43
-------
TABLE 5. FINE GRAIN SEDIMENT YIELDS OF TEST PLOTS
FOR EACH SAMPLING PERIOD
FINE SEDIMENT CONCENTRATION (ppm)
CODE
B
B
B
T
T
T
T
T
T
T
T
M
M
M
M
S
S
S
S
U
U
U
X
X
CODE: B-blanket products; T-chemical stabilizers
and tackifiers; M-hydromulches; S-straw pro-
ducts; l)-untreated (application of standard
lime, fertilizer and seed mix only); and X-
untreated.
PLOT
A-l
A- 5
B-9
A- 2
A- 3
B-10
B-ll
B-13
B-18
C-20
C-22
A-4
A- 6
B-12
B-17
A-7
B-15
C-19
C-21
A- 8
B-14
C-24
B-16
C-23
10/27
2,618
2,750
3,351
2,291
3,520
778
739
3,123
6,094
1,764
1,520
3,433
7,817
3,164
1,182
4,723
225
2,255
• —
5,591
2,251
6,522
5,730
6,371
11/11
362
252
1,314
1,041
1,169
197
444
606
1,096
648
833
— -._
6,899
410
425
CLEAR
514
638
1,932
1,190
4,246
___
—
12/2
78
57
CLEAR
235
469
645
130
502
231
156
152
348
519
—
—
116
CLEAR
67
92
1,158
931
—
723
3,036
12/19
98
137
116
250
482
48
67
545
635
315
257
136
244
80
280
163
CLEAR
80
76
434
1,004
3,520
422
3,096
1/23
150
286
178
1,189
956
210
225
109
413
1,267
1,202
681
1,183
120
204
210
114
523
186
810
170
4,238
841
—
44
-------
centrations. Straw tacked with a netting (A-7) yielded fine grain concentra-
tions comparable to the untreated plots.
The plot treated with mulches gave varying results. Conwed wood fiber
mulch (B-17) produced a low fine grain sediment concentration, while the plot
treated with Superior Turfiber ((A-6)(cardboard fiber)) produced the highest
recorded fine grained sediment concentration. The plots covered with blanket
products produced average to high concentrations of suspended material.
Due to the wide range of values and the expected natural variations in
minor grain size distribution from site to site, coupled with differences in
runoff rates, conclusions based on the suspended sediment data are, at the most,
tenuous. It appears, however, that some chemical stabilizers did succeed in
binding the fine soil particles and, to some extent, were effective in signif-
icantly reducing the erosion of the fine fraction component of the soil.
45
-------
SECTION 8
COST BENEFIT ANALYSIS
Maximum effectiveness of soil stabilization is a primary concern when
choosing an erosion control treatment for a specific problem area. However,
the reclamation effort must be economically feasible as well as environmentally
sound. In cases such as strip mines, sand and gravel pits and large construc-
tion sites, the areas to be reclaimed may be on the order of hundreds of acres,
and the cost-benefit ratio becomes a necessary consideration in deciding upon
a particular treatment application.
The costs for implementing various erosion control-revegetation treatments
can be broken down into two major categories; cost of materials and installation
costs. Costs for materials are listed in Table 6, prorated by application rates
used in the test. It is very difficult, however, to calculate a reliable esti-
mate for application of such treatments, with such variables coming into play as
a crew's experience with a product, labor rates, site location, time and season
of application and the size of the job. It is expected, though, that treatments
that can be applied with the greatest ease will, in a sense, be the least expensive
to employ. With this in mind, a relative degree of difficulty in treatment ap-
plication is reflected in Tables. An "A" listing signifies the easiest and
probably most inexpensive application technique. As an example, seed, fertil-
izer and treatment can be applied in a slurry in one application with a hydro-
seeder. This reduces the time spent on the site as well as application time.
The hydromulches also have the lower cost for materials. However, the chemical
stabilizers with mulches cost approximately double, due to the slightly higher
per acre cost for the material itself as well as the additional cost of the
added wood fiber mulch.
The straw treatments were given a "B" rating for expense in application,
due to the additional step required to blow the straw onto the site. Although
the straw mulch costs only $120 per acre ($48.50 per hectare), an additional
cost is incurred by the application of the tackifier over the straw. In the
case of the straw tacked with Vexar net, there is an even larger cost increase,
due to the labor required to manually apply the netting product and the cost of
the net and staples. All of the blanket products reflect this increase in la-
bor for manual application and stapling and so were all given a "C" rating. The
costs for these materials were much more expensive than any other treatments.
By considering the effectiveness of these products with respect to the
expense for treatment, an analysis of the most advantageous treatment for spe-
cific conditions can be discerned. The blanket treatments are the most effec-
tive in controlling erosion and have a much greater stability due to the staple
46
-------
TABLE 6. COST ANALYSIS OH PER ACRE BASIS*
Product Total Cost Relative Expenses
Tested Materials (per acre)** for Application***
Blanket
Excelsior $1,597 C
Hold gro $2,129 C
Jute $1,228 C
Hydromulches
Conwed $120 A
Silva $111 A
Turfiber $115 A
Pulch $84 A
Chemical Stabilizers
(with 500 Ibs/acre
at $50)
Curasol AK $225 A
Genaqua 743 $220 A
Aerospray 70 $242 A
Dow Mulch Binder $157 A
Petroset SB $200 A
Terra Tack III $166 A
Straw with Tackifiers
(Straw at 3,000 Ibs/
acre at $120)
Straw (Vexar net) $604 C
Straw (Curasol AK) $295 B
Straw (Terra Tack II) $231 B
Straw (Dow Mulch Binder) $227 B
*Based on 1977 price quotations.
**To obtain cost per hectare, multiply these values by 0.404.
***Expense for application is presented as a relative degree of difficulty in
installing treatment. "A" requires the easiest technique for application,
where lime, seed, fertilizer and treatment are installed with the hydro-
seeder. "B" requires the additional step of blowing the straw,'and "C" re-
quires very involved manual application of the treatment.
47
-------
method of tacking. Yet the expense makes utilization on a large-scale basis
uneconomical. Under such circumstances, these blanket products could be used
most economically in problem areas where slopes are very steep and unstable or
where poor water management has resulted in confined flow.
The straw treatments are almost if not just as effective as the blankets,
but are much more economical. The straw mulch can be applied to large areas
and on moderate slopes and needs no tackifier. Also, a straw mulch, when tacked
with a plastic net, such as Vexar, could be used in a situation where a blanket
product must be used for comparable effectiveness, but for a much lower cost.
The hydromulches and chemical tackifiers have the lowest application cost
per acre treatment and are the easiest to apply. However, the results of the
tests showed that they were not as effective in controlling soil erosion as
originally anticipated.
Hydromulches that were applied to test plots alone were easily dislodged
by heavy rains and washed downs!ope. The chemical stabilizers which were
tested in conjunction with only 500 pounds of wood fiber mulch per acre did not
have the capability of preserving moisture at the soil surface. Larger quan-
tities of mulch were required for soil moisture retention and to promote faster
germination and more rapid vegetational growth.
Additional testing is needed for a variety of combinations of amounts of
hydromulch and chemical stabilizers with cost of materials ranging from $200
to $300 on a per acre ($80 to $120 per hectare) basis. The formulation of
an optimum blend of each component, which takes advantage of the merits of.each
treatment would be a valuable and economical treatment for erosion control.
48
-------
COMPARISON WITH SEDIMENT YIELD DATA IN THE LITERATURE
Many other field tests, in addition to the test discussed in this report,
have been conducted in recent years comparing the effectiveness of numerous
soil erosion prevention and revegetation treatments. Although a significant
amount of sediment yield data in response to various treatments exists in the
literature, it has been very difficult to analyze these data in a comparative
sense. In most cases, test conditions differ drastically, including climate,
precipitation, soil types and slope characteristics, making test results dif-
ficult to evaluate.
One manner of comparison is to reduce all sediment yield data to a common
base which would facilitate the evaluation of treatment effectiveness. The
common base which was used is the VM factor discussed previously. VM
values of 1.0 indicate that the treatment had no effect on stabilizing the soil
or inhibiting erosion. The lower the VM value (expressed as a decimal), the
more effective the soil stabilizing treatment.
The results of each field test found in the literature included at least
one control plot of similar character but which had no treatment. From this
relationship, it was possible to calculate VM factors for all the test data by
taking the ratio of sediment eroded from the treated plot to the sediment yield
of the control. The values are shown in Table 7 and can be used to compare the
results derived from this study with those reported in the literature.
In general, the blanket products show consistently low VM values (i.e.,
effective soil stabilizers) and have the lowest values among the treatment
types tested. However, the high initial cost and the increased installation
time make these products unsuitable for large-scale reclamation tasks. These
blanket treatments are especially suited for trouble spots where an unusually
severe erosion problem is expected from a limited area; for example, drainage
ditches or areas characterized by large runoff volumes.
The results show that the straw mulch treatments had the lowest VM values.
Treatment rates of 1.5 to 2 tons of straw per acre (181 to 733 kg/ha) seemed to
be quite sufficient to control erosion, either with or without an additional
tacking agent. The next best treatment process involved the use of hydro-
mulches, and the effectiveness had a mean VM value of about 0.237. Straw, how-
ever, is much less expensive than the hydromulches, which allows the straw to
be applied at higher rates and with a tacking agent for a comparable lower cost.
Although the study found that straw mulch only really needs a tackifier to re-
sist high winds and runoff on very steep slopes, it did not, as was observed
with wood and paper fiber hydromulches, tend to wash downslope in a tumbling
fashion in large rainstorms, creating ridges of mulch and leaving behind large
unprotected areas.
The plots treated with hydromulch and tackifier combinations show consis-
tently higher VM values. The amount of hydromulch applied in these combination
tests was reduced to compensate for the additional cost and expected effects
of the tackifier. The plots treated only with chemical stabilizers produced
49
-------
TABLE 7. COMPARISON OF EFFECTIVENESS OF EROSION
REVEGETATION TREATMENTS BY VM FACTOR FOR FIELD TEST DATA
Reference
Number
1
1
2
*
*
*
*
2
1
2
1
1
1
1
2
3
2
2
2
5
*
5
*
1
*
4
5
Treatment
HYDROMULCHES
wood fiber mulch
wood fiber mulch
Conwed wood fiber
mulch
Conwed wood fiber
mulch
Silva wood fiber
mulch
Turfiber
Pulch
Hardwood bark
CHEMICAL STABILIZERS
Aquatain
Aquatain
Aerospray 70
Curasol AK
Petroset SB
Terra Tack
Terra Tack
Crust 500
Genaqua 743
M-145
M-145
BLANKET PRODUCTS
Hold gro
Hold gro
Excelsior
Excelsior
Excelsior
Jute
Jute
Jute
Rate
(per acre)
1,000 Ibs
1,400 Ibs
1,000 Ibs
1,200 Ibs
1,200 Ibs
1,200 Ibs
1,200 Ibs
27 cu yd
10 Ibs
20 Ibs
480 gal
55 gal
72 gal
18 gal
Rate
(per hectare)
VM Factor
183.6 kg
256.9 kg
183.6 kg
220.3 kg
220.3 kg
220.3 kg
220.3 kg
20.6 cu m
0.050
0.010
0.169-.304
0.235
0.266
0.655
0.280
0.169
1.84 kg
3.67 kg
735 1
84 1
110 1
27 1
mean=0.237
0.680
0.168
0.940
0.300-.480
0.400-.660
0.660
0.659
0.005
0.235
0.270
0.675
mean=0.470
0.013
0.147
0.102
0.086
0.040-.100
0.110
0.037-.104
0.215
mean=0.092
50
-------
(Continued)
TABLE 7. COMPARISON OF EFFECTIVENESS OF EROSION
REVEGETATION TREATMENTS BY VM FACTOR FOR FIELD TEST DATA
Reference
Number
6
6
5
*
2
*
*
*
4
Treatment
STRAW MULCHES
Straw, asphalt
Same treatment on
four soil types
Straw, mixed
Same four soil
types, respec-
tively
Straw, Vexar net
Straw, Vexar net
Straw, Curasol
Straw, Curasol AK
Straw, Dow
Straw, Terra Tack
Straw, Terra Tack
Rate
(per acre)
2 tons, 450 gal
2 tons
2 tons
1.5 tons
1.5 tons, 40 gal
1.5 tons, 45 gal
1.5 tons, 45 gal
1.5 tons, 45 Ibs
—
Rate
(per hectare)
734 kg, 689 1
734 kg
734 kg
550 kg
550 kg, 61 1
550 kg, 69 1
550 kg, '69 1
550 kg, 69 1
—
VM Factor
0.112
0.540
0.195
0.420
0.075
0.078
0.083
0.270
0.023
0.110
0.034
0.099
0.021
0.108
0.013-.030
mean=0.138
HYDROMULCH AND TACKIFIER COMBINATIONS (wfnpwood fiber mulch)
2
2
*
2
*
*
*
*
*
*
*
Aerospray 70 wfm
Aerospray 70 wfm
Aerospray 70 wfm
Curasol wfm
Curasol AK wfm
Petroset SB wfm
Genaqua 743 wfm
Perma Soil wfm
Terra Tack wfm
Crust 500 wfm
Dow wfm
40 gal, 800 Ibs
80 gal , 800 Ibs
45 gal, 500 Ibs
40 gal, 800 Ibs
40 gal, 500 Ibs
45 gal, 500 Ibs
45 gal, 500 Ibs
45 gal, 500 Ibs
40 gal, 500 Ibs
45 gal , 500 Ibs
45 gal, 500 Ibs
61 1, 147 kg
122 1, 147 kg
69 1, 91.7 kg
61 1, 147 kg
69 1, 91.7 kg
69 1, 91.7 kg
69 1, 91.7 kg
69 1, 91.7 kg
61 1, 91.7 kg
69 1, 91.7 kg
69 1, 91.7 kg
0.287
0.930
0.378
0.051
0.118
0.361
0.078
0.381
0.607
0.226
0.185
mean=0.327
REFERENCE NUMBERS LISTED IN TABLE 7
* Data collected in this study
1 Utah Water Research Laboratory, 1976
2 Plass (1973)
3 Haines (1977)
4 Gaskin et. ai. (1976)
5 Gulf States Paper (1977)
6 Barnet et. al. (1976)
51
-------
the worst test results, but in most cases, the application rates were delib-
erately low in order to keep the treatment cost economically comparable with
the other methods used. In another study, where Crust 500 was applied at a
rate of 480 gal/acre (751 1/ha), the test results were excellent. Such a
large application rate, however, is only feasible for small areas and for
special dust control or fine grained soil stabilization purposes. Thus, to
properly evaluate the performance of each treatment, it is necessary to con-
sider the rate of application as well as the cost of materials, installation
costs and sediment yield data.
52
-------
REFERENCES
1. Barnet, A. P., E. G. Diseker and E. C. Richardson. Evaluation of
Mulching Methods for Erosion Control on Newly Prepared and Seeded High-
way Backslopes. Agriculture Journal, Vol. 59, 1967. pp. 83-88.
2. Ellerbe, C. South Carolina Soils and Their Interpretations for Selected
Uses. South Carolina Land Resources Conservation Commission, Columbia,
SC, 1974.- 289 pp.
3. E.P.A. Erosion and Sediment Control: Surface Mining in the Eastern U.S.
Vol. I Planning-Technology Transfer Seminar Publication, 1976a. pp. 38-
41.
4. . Erosion and Sediment Control: Surface Mining in the Eastern
U.S. Vol. II, Design-Technology Transfer Seminar Publication, 1976B. pp.
81-87.
5. Gaskin, D. A., W. Hannel and L. E. Stanley. Results of the 1974-1975
C.R.R.E.L. Terrain Stabilization Research/Demonstration Study. Technical
Note, Dept. of Army Corps of Engineers, 1976. 44 pp.
6. Gulf States Paper. Report of the Sediment Yield Tests with Hold gro
Erosion Control Fabric and Competitive Products. Special Report,
Technical Services Division, Tuscaloosa, Alabama, 1977. 17 pp.
7.. Guy, H. P. Laboratory Theory and Methods for Sediment Analysis. U.S.G.S.
Techniques for Water Resources Investigations, Book 5, Chap. C-l, Supt.
of Documents, Washington, D.C., 1969.
8. Haines, L. H. Personal Communication, U.S.D.I., Bureau of Reclamation.
9. Plass, Bill. Chemical Stabilizers for Surface Mine Reclamation.
National Research Council Special Report, Highway Research Board,
Washington, D.C., 1973. pp. 118-132.
10. S.C.S. National Engineering Field Manual for Conservation Practices.
Chap. 2, Estimating Runoff. Engineering Branch, Hydrology Branch,
Washington Advisory, Eng. 67, Supt. of Documents, Washington, D.C.,
1971a. pp. 2.1-2.71.
11. S.C.S. Engineering Handbook. U.S. Dept. of Agriculture, Sect. 4, Hydrol-
ogy, Chap. 10, Estimating Direct Runoff from Storm Rainfall. Supplement
A. Supt. of Documents, Washington, D.C., 1971b. pp. 10.1-10.21.
53
-------
12. S.C.S. Status of Land Disturbed by Mining as of January 1, 1974 by
States. U.S.D.A. Interagency Memo, 1974. 6 pp.
13. Utah Hater Research Laboratory. Erosion Control During Highway Con-
struction. Majiual of Erosion Control Principles and Practices, Vol. II.
Utah State University, Logan, Utah, 1976. 93 pp.
14. Young, R. A. and 0. L. Hiersma. The Role of Rainfall Impact in Soil
Detachment and Transport. Water Resources Research, Vol. 9, No. 6,
1973. pp. 1,629-1,636.
54
-------
APPENDIX
PHOTOGRAPHIC REPRESENTATION OF TREATMENT RESPONSE
FROM 10/18/77 THROUGH 1/23/78
PLATE 1
PLOT A-l; JUTE NETTING
Plot A-l. (a). Jute netting was tested on plot A-l. Alternate wetting
and drying caused netting shrinkage and produced gaps along the side-
laps (October 28, 1977).
(b). Appearance^of plot on November 28, 1977.
55
-------
PLATE 1 (Continued)
PLOT A-l; JUTE NETTING
(c). Appearance of plot on December 15, 1977,
(d). Appearance of plot on January 23, 1977.
56
-------
PLATE 2
PLOT A-2; AEROSPRAY (DCA-70) AND WOOD FIBER MULCH
Plot A-2 (a). A breach in the drainage diversion plate caused advanced
erosion to take place in the demonstration portion of the plot. However,
the soil had formed a crust with the tackifier and severe erosion was
prevented (October 28, 1977).
(b). Appearance on November 28, 1977.
57
-------
PLATE 2 (Continued)
PLOT A-2; AEROSPRAY (DCA-70)AND WOOD FIBER MULCH
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1977.
58
-------
PLATE 3
PLOT A-3; PETROSET SB WITH WOOD FIBER MULCH
Plot A-3 (a). Plot was treated with Petroset SB tackifier over wood
fiber mulch. Some soil crusting was noticed which inhibited severe
erosion at the base of the plot (October 28, 1977).
(b). Appearance on November 28, 1977.
59
-------
PLATE 3 (Continued)
PLOT A-3; PETROSET SB WITH WOOD FIBER MULCH
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1977.
60
-------
PLATE 4
PLOT A-4; SILVA FIBER
Plot A-4 (a).
(a). Appearance on October 28, 1977.
Notice the concentration of
seedlings in the upper left-
hand portion of the plot.
(b). The mulch appeared to move down-
slope and gathered in ribs ori-
ented transverse to the slope.
These ribs formed as the mate-
rial was washed and became
caught in pebbles and small
stones (October 28, 1977).
Plot A-3 (b).
61
-------
PLATE 4 (Continued)
PLOT A-4; SILVA FIBER
(c). Appearance on November 28, 1977.
(d). Appearance on December 15, 1977.
62
-------
PLATE 4 (Continued)
PLOT A-4; SILVA FIBER
(e). Appearance on January 23, 1978.
63
-------
PLATE 5
PLOT A-5; EXCELSIOR BLANKET
Plot A-5 (a). Excelsior blanket applied to plot A-5 provided a good
initial grass cover. Seedlings on this plot appeared 50% taller than
on any other test plot. Note the excelsior blanket is still IV (3.8 cm)
thick and so hides the shorter seedlings from view (October 28, 1977).
(b). Appearance on November 28, 1977.
64
-------
PLATE 5 (Continued)
PLOT A-5; EXCELSIOR BLANKET
(c). Appearance on December 15, 1977,
(d). Appearance on January 23, 1978.
65
-------
PLATE 6
PLOT A-6; SUPERIOR TURFIBER
Plot A-6 (a). This plot treated with Superior Turfiber shows devel-
opment of a sparse vegetative cover (October 28, 1977).
(b). Appearance on November 28, 1977.
66
-------
PLATE 6 (Continued)
PLOT A-6; SUPERIOR TURFIBER
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
67
-------
PLATE 7
PLOT A-7; STRAW MULCH WITH VEXAR PLASTIC NET
Plot A-7 (a). Straw mulch stabilized with Vexar plastic net (October 28,
1977).
(b). Appearance on November 23, 1977.
68
-------
PLATE 7 (Continued)
PLOT A-7; STRAW MULCH WITH VEXAR PLASTIC NET
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
69
-------
PLATE 8
PLOT A-8; CONTROL FOR "A" HILLSLOPE
Plot A-8 (a). This plot was treated only with the standard fertilizer,
lime and seed mixture. Severe gullying and pedestal erosion was noted
(October 28, 1977).
(b). Appearance of control plot on November 23, 1977.
70
-------
PLATE 8 (Continued)
PLOT A-8; CONTROL FOR "A" HILLSLOPE
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
71
-------
PLATE 9
PLOT B-9; HOLD 6RO
Plot B-9 (a). On October 28, 1977, this plot appeared to have the most
dense seedling development. Some tenting (uplifting of the blanket
cover by new vegetative growth) can be seen in the areas pointed to by
arrows.
(b). Close-up view of tenting phenomenon (October 28, 1977)
72
-------
PLATE 9 (Continued)
PLOT B-9; HOLD GRO
(c). Appearance on November 28, 1977.
(d). Appearance on December 15, 1977.
73
-------
PLATE 9 (Continued)
PLOT B-9; HOLD GRO
(e). Appearance on January 23, 1978.
74
-------
PLATE 10
PLOT B-10; CURASOL AK AND WOOD FIBER
Plot B-10 (a). Plot treated with Curasol AK'and wood fiber (October 28,
1977).
(b). Appearance on November 28, 1977.
75
-------
PLATE 10 (Continued)
PLOT B-10; CURASOL AK AND WOOD FIBER
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
76
-------
PLATE 11
PLOT B-ll; GENAQUA 743 AND WOOD FIBER MULCH
Plot B-ll (a). Genaqua 743 was applied over wood fiber mulch (October 28,
1977).
(b). Appearance on November 28, 1977.
77
-------
PLATE 11 (Continued)
PLOT B-1U GENAQUA 743 WITH WOOD FIBER
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
78
-------
PLATE 12
PLOT B-12; PULCH
Figure B-12 (a).
(a). This plot treated with Pulch
hydromulch showed a sparse
vegetative cover on October
28, 1977. Significant amounts
of the mulch were found to be
washed as far as 10 feet (3 m)
out of the demonstration por-
tion of the plot.
(b). Close-up of appearance on
October 28, 1977.
Figure B-12 (b).
79
-------
PLATE 12 (Continued)
PLOT B-12; PULCH
(c). Appearance on November 28, 1977.
(d). Appearance on December 15, 1977.
80
-------
PLATE 12 (Continued)
PLOT B-12; PULCH
(e). Appearance on January 23, 1978.
81
-------
PLATE 13
PLOT B-13; PERMA SOIL AND WOOD FIBER MULCH
Plot B-13 (a). The downslope transport of the wood fiber mulch used
in the tackifier test was most noticeable on this plot; October 28, 1977.
(b). Appearance on November 28, 1977.
82
-------
PLATE 13 (Continued)
PLOT B-13; PERMA SOIL AND WOOD FIBER MULCH
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
83
-------
PLATE 14
PLOT B-14; CONTROL FOR
•B" HILLSLOPE
Plot B-14 (a). This plot was kept as a control for the "B" hillslope
and only the standard fertilizer, lime and seed mixture was applied.
Gull eying and pedestal erosion were found (October 28, 1977).
(b). Close-up of severe erosion exhibited on this plot (October
28, 1977).
84
-------
PLATE 14 (Continued)
PLOT B-14; CONTROL FOR "B" HILLSLOPE
(c). Appearance on November 28, 1977.
(d). Appearance on December 15, 1977.
85
-------
PLATE 14 (Continued)
PLOT B-14; CONTROL FOR "B" HILLSLOPE
(e). Appearance on January 23, 1978.
86
-------
PLATE 15
PLOT B-15; DOW MULCH BINDER AND STRAW
Plot B-15 (a). This plot was treated with a straw mulch and Dow binder.
On October 28, 1977, this plot had achieved one of the most advanced
vegetative covers during this period.
(b). Appearance on November 28, 1977.
87
-------
PLATE 15 (Continued)
PLOT B-15; DOW MULCH BINDER AND STRAW
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
88
-------
PLATE 16
PLOT B-16; UNTREATED
Plot B-16 (a). This plot was designated as a control for the "B"
hill si ope. The soil was disturbed and no treatment, amendments,
or seed was applied.
(b). The almost total absence of vegetation at this point demonstrates
the effectiveness of measures taken to eliminate regrowth of volunteer
vegetation on the test plots (January 23, 1978).
89
-------
PLATE 17
PLOT B-17; CONWED AND WOOD FIBER MULCH
Plot B-17 (a). On October 28, 1977, this plot showed that the thin
vegetative cover had developed more in the slightly lower lying areas
in the center of the plot.
(b). The mulch showed a strong tendency to wash downslope and collect
in ribs. Close-up of this characteristic on October 28, 1977.
90
-------
PLATE 17 (Continued)
PLOT B-17; CONWED AND WOOD FIBER MULCH
(c). Appearance on November 28, 1977.
(d). Appearance on December 15, 1977.
91
-------
PLATE 17 (Continued)
PLOT B-17; CONWED AND WOOD FIBER MULCH
(e). Appearance on January 23, 1978.
92
-------
PLATE 18
PLOT B-18; TERRA TACK III AND WOOD FIBER MULCH
Plot B-18 (a). This plot was treated with Terra Tack III. Appearance
on October 28, 1977.
(b). Appearance on November 28, 1977.
93
-------
PLATE 18 (Continued)
PLOT B-18; TERRA TACK III AND WOOD FIBER MULCH
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
94
-------
PLATE 19
PLOT C-19; TERRA TACK II AND STRAW
Plot C-19 (a). This plot was treated with straw and Terra Tack II, which
we believe was not sufficiently mixed to become effective. In spite of
this malfunction, the distribution of straw was not severely affected
(October 28, 1977).
(b). Appearance on November 28, 1977.
95
-------
PLATE 19 (Continued)
PLOT C-19; TERRA TACK II AND STRAW
(c). Appearance on December 15, 1977.. -•,••
96
-------
PLATE 20
PLOT C-20; CRUST 500 WITH WOOD MULCH FIBER
Plot C-20 (a). This treatment, following application, caused the surface
of the plot to become encrusted, whereby all of the soil particles were
bound together. Appearance on October 28, 1977.
(b). Appearance on November 28, 1977.
97
-------
PLATE 20 (Continued)
PLOT C-20; CRUST 500 WITH WOOD MULCH FIBER
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1977.
98
-------
PLATE 21
PLOT C-21; CURASOL AK AND STRAW
Plot C-21 (a). This plot exhibited good seedling distribution (October 28,
1977).
(b). Close-up of ground coverage afforded by straw and seedling distri-
bution (October .28, 1977).
99
-------
PLATE 21 (Continued)
PLOT C-21; CURASOL AK AND STRAW
(c). Appearance on November 28, 1977.
(d). Appearance on December 15, 1977.
100
-------
PLATE 21 (Continued)
PLOT C-21; CURASOL AK AND STRAW
(e). Appearance on January 23, 1978.
101
-------
PLATE 22
PLOT C-22; DOW MULCH BINDER WITH WOOD FIBER MULCH
¥y*fr-^ff£r* ^'-.-V" "«*£="ft K^I
Plot C-22 (a). Following application, we noticed that a crust had formed
on the soil surface.
(b). Appearance November 28, 1977.
102
-------
PLATE 22 (.Continued)
PLOT C-22; DOW MULCH BINDER WITH WOOD FIBER MULCH
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
103
-------
PLATE 23
PLOT C-23; UNTREATED
Plot C-23 (a). Appearance of plot on December 15, 1977.
designated as an untreated and unseeded control.
This plot was
(b). A small quantity of seed was spilled at the base of the plot during
application on an adjacent plot. All the vegetation growing on the plot
can be attributed to the spill. This further substantiates the effective-
ness of measures taken to eliminate growth of volunteer vegetation.
104
-------
PLATE 24
PLOT C-24; CONTROL FOR
"C" HILLSLOPE
Plot C-24 (a). This plot was chosen for the control on the "C" hillslope.
Only the standard lime, fertilizer and seed mixture was applied. Of all
the control plots, this one exhibited the most intense gulleying (October
28, 1977).
(b). Appearance on November 28, 1977.
105
-------
PLATE 24 (Continued)
PLOT C-24; CONTROL FOR "C" HILLSLOPE
(c). Appearance on December 15, 1977.
(d). Appearance on January 23, 1978.
106
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA-600/2-79-124
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
EVALUATION OF SELECTIVE EROSION CONTROL TECHNIQUES
Piedmont Region of S.E. United States
5. REPORT DATE
December 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Herb Buxton
Frank T. Caruccio
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of South Carolina
Department of Geology
Columbia, South Carolina 29208
10. PROGRAM ELEMENT NO.
1BC822; SOS #2; Task 19
11-
NO.
S-803724
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory—Gin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final Report 5/77 - 1/78
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
'Project Officer: Hugh Masters, (201) 321-6678; (8-340-6678)
16. ABSTRACT
Commercially available soil stabilizers, incl uding chemical tackifiers, hydro-
mulches and blanket (netting) products and combinations thereof, were tested in the
Piedmont of South Carolina. The test site was designed to measure sediment yields to
provide a quantitative assessment of treatment effectiveness.
Following a severe rain, during the period before the establishment of a dense
grass cover, it was found that the blanket products and straw mulches provided the
soil with maximum protection from erosion. Some tackifiers were effective in stabili-
zing the fine fraction of the soil. Some hydromulches tended to be washed away and
were not effective in inhibiting soil erosion.
Each treatment contained a standard lime, seed and fertilizer mixture to test
the ability of the technique to produce a dense vegetative cover. After 8 to 12
weeks, the straw and blanket products produced a more dense vegetative cover than the
hydromulches and tackifiers. This was probably due to increased soil surface moisture
afforded by the former as an insulating blanket.
With time, however, as lateral rhizome development of grasses took place, the
soil protection was more readily afforded by the vegetative cover and all sediment
yields decreased.
A cost analysis showed that some of the more successful treatments are too ex- '
pensive to be applied routinely over large areas. The results of this study compared
h
rose or oter reporte sg§OSANDDOCUMENTANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Erosion control, Sediment transport,
Hydrology, Construction, Land development,
Cost effectiveness, Soil erosion
Piedmont of South Carol in
Soil stabilizing and re-
vegetation treatments,
Sediment yields
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport}
UNCLASSIFIED
21. NO. OF PAGES
117
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
107
------- |