Caltrans Erosion Control Pilot Study

Carol L. Forrest, P.E.

Vice President, URS Corporation

1615 Murray Canyon Road, Suite 1000

San Diego, CA 92108

Phone: (619) 294-9400, Fax: (619) 293-7920

Email: <carol_forrest@urscorp.com>

Michael V. Harding, CPESC

President, Great Circle International, LLC

1202 Novara Street, San Diego, CA 92107

Phone: (619) 222-9862, Fax: (619) 222-9923

Email: <hawkeye157@aol.com>

Nancy Gardiner

Senior Project Manager, URS Corporation

1615 Murray Canyon Road, Suite 1000

San Diego, CA 92108

Phone: (619) 294-9400, Fax: (619) 293-7920

Email: <nancy_gardiner@urscorpcom>

Howard H. Chang, PhD, Professor

Civil and Environmental Engineering Department

San Diego State University

San Diego, CA 92132

Phone: (619) 594-6380, Fax: (619) 594-8078

Email: <changh@mail.sdsu.edu>

BIOGRAPHICAL SKETCHES

Michael V. Harding, CPESC

Michael V. Harding is one of the leading technical experts in the
erosion control industry. A graduate from Purdue University, Michael has
over 22 years experience in erosion and sediment control, resource
management, mined land reclamation, wildlife habitat development, and
nonpoint source pollution control both in the United States and
overseas. Michael specializes in the evaluation, research, development,
and application of cost-effective erosion control materials and
techniques. He has contributed significantly to the body of knowledge
related to the effectiveness of alternative approaches to erosion
control through field and laboratory testing programs. Michael is three
times past President of the International Erosion Control Association
(IECA) and is Chairman of the CPESC Ethics Committee. Michael is the
current Director of the San Diego State University Soil Erosion Research
Laboratory in San Diego, CA.

Carol L. Forrest, P.E*.*

Carol L. Forrest is a Vice President with URS Corporation. She has over
24 years experience in watershed management, urban runoff, and storm
water pollution. Ms. Forrest is a nationally known expert in erosion and
sediment control. She is twice past President of the International
Erosion Control Association (IECA), twice past President of the Western
Chapter of the IECA, and Chair of the CPESC Council. Ms. Forrest is a
registered civil engineer, registered geotechnical engineer, Certified
Professional Erosion and Sediment Control Specialist, and a Storm Water
Quality Specialist. She has been involved in projects related to
watershed management, erosion control, water quality, and resource
management throughout the United States and overseas.

**Nancy Gardiner**

Nancy Gardiner has more than 14 years of consulting experience
performing and managing water quality and water resource projects in
California. In recent years, her practice has focused specifically on
storm water monitoring, NPDES permitting, management, and training.
Nancy has been involved in research, pilot studies and training for
Caltrans on erosion and storm water pollution associated with highway
runoff. She is a Masters level geologist/hydrogeologist with both
management and technical experience in storm water management.

Howard H. Chang, PhD

Dr. Howard H. Chang is on the Civil and Environmental Engineering
faculty at SDSU. As a registered civil engineer, he is involved in
research and professional consulting in the areas of hydraulics,
hydrology and sedimentation. He has been active in floodplain mapping,
hydrology and watershed modeling, hydrological simulation, designs of
channels and floodwater detention basins, river channel erosion and
sedimentation. He is the author of over 100 technical papers, several
computer models for channel design and river hydraulics, and the book
*Fluvial Processes in River Engineering* published in 1988. Dr. Chang
has taught short courses on river and sedimentation engineering,
hydrology for flood control, and the use of the HEC-2 and Fluvial
programs. He has also served as a consultant for consulting firms,
local, state and federal governmental agencies, and the United Nations.

CALTRANS EROSION CONTROL PILOT STUDY

**Michael V. Harding, CPESC**

Great Circle International

**Carol L. Forrest, P.E.**

URS Corporation

**Nancy Gardiner**

URS Corporation

**Howard H. Chang^,^ PhD**

San Diego State University

**Abstract**

The objective of the Erosion Control Pilot Study was the evaluation of
alternative soil stabilization methods designed to minimize the erosion
and transport of sediment from Caltrans rights-of-way to drain inlets.
Field and laboratory programs were developed to test the candidate
erosion control measures. The field program included test plots for
measuring erosion rates from existing Caltrans cut and fill slopes under
natural rainfall conditions and test plots for monitoring the
effectiveness of sixteen different types of temporary erosion control
measures on the establishment of a native California plant community.
The laboratory test program included the measurement of erosion rates
from simulated Caltrans slopes, the measurement of erosion rates from
existing slopes with various vegetation densities and water quality
analyses on runoff from simulated Caltrans slopes that were treated with
sixteen different non-vegetative erosion control measures. All elements
of the laboratory test program were performed with typical southern
California rainfall patterns as obtained from a rainfall simulator. The
laboratory testing program was performed by San Diego State University
on a rainfall simulation facility with a tilting test bed that was
constructed for this study.

## BACKGROUND

The California Department of Transportation (Caltrans) conducted a
\$3.2M Erosion Control Pilot Study (ECPS) from 1998 to 2000. The
objective of the ECPS was to evaluate alternative soil stabilization
methods designed to minimize the erosion of Caltrans highway slopes and
transport of sediment to Caltrans storm drain inlets in District 7 (Los
Angeles).

Caltrans selected URS Corporation to design and manage the study, with
Great Circle International as a subconsultant. The design phase of the
ECPS employed a systematic approach to defining current Caltrans erosion
problems, and identifying candidate soil stabilization measures and
practices that will mitigate such problems. Field and laboratory
programs were developed to test candidate soil erosion control measures.

In order to perform comparative laboratory tests of erosion control
effectiveness, a rainfall simulation facility, the Soil Erosion Research
Laboratory (SERL), was designed and constructed at San Diego State
University through the Civil and Environmental Engineering Department.
The portable rainfall simulators were also used on field test plots in
Los Angeles. Other portions of the ECPS relied on the results of natural
rainfall on field test plots.

This paper presents the results of three elements of the Erosion Control
Pilot Study (ECPS):

(1) The measurement of erosion rates from simulated highway slopes that
    were roughened with different mechanical techniques;

(2) The measurement of erosion rates from existing highway slopes with
    various vegetation densities; and

(3) The evaluation of erosion rates and runoff from slopes that were
    treated with fifteen different non-vegetative, erosion control
    measures.

Erosion rates were determined by collecting all runoff and sediment and
comparing values against a bare soil (control) or untreated condition.

SAN DIEGO STATE UNIVERSITY SOIL EROSION RESEARCH LABORATORY

The SDSU Physical Plant constructed the laboratory facilities with
funding provided by Caltrans. The San Diego State University Soil
Erosion Research Laboratory (SDSU/SERL) integrates beneficial features
from three of the primary, soil erosion research facilities in the
United States. The purpose of the SDSU/SERL is to study erosion problems
associated with highway slopes. The ECPS evaluated soil losses during
single storms as well as the mean annual soil loss. Typical rainfall
intensity-duration-frequency curves for Los Angeles County, California
were employed as the basis for single storm events, including the
5-year, 10-year, and 50-year storms.

## Norton ladder rainfall simulator

The rainfall simulation device selected for the SDSU Soil Erosion
Research Laboratory is the Norton Ladder Rainfall Simulator, which was
developed at the USDA-ARS National Soil Erosion Research Laboratory by
Dr. Darrell Norton. For testing at the indoor laboratory, multiple
simulators have been installed in parallel above the soil test bed to
uniformly apply precipitation over the entire test plot area. The
simulators are also routinely taken down and transported to the outdoor,
vegetative coverage test plots.

### 

The drop former used for the Norton simulator is the Spraying Systems
Veejet nozzle, and the nozzles are spaced 1.1 meters apart. For uniform
intensity across the plot, the center of spray patterns from two
laterally adjacent nozzles meet at the plot surface. This gives a
2.25-mm median drop size, a nozzle exit velocity of 6.8 m/s, and a
spherical drop. The impact velocities of almost all drops from the
Veejet nozzle are nearly equal to the impact velocities of those from
natural rainstorms when the nozzle is at least 2.4 meters above the soil
surface. For this reason, the rainfall simulators used in the SDSU/SERL
are installed such that the nozzles are a minimum of 2.5 meters above
the soil surface. Rainfall intensity can be changed instantaneously with
the simulator in operation, and the maximum intensity produced is 135
mm/hr.

### 

## Soil test bed

The soil test bed is a 3-meter wide by 10-meter long (323 square feet)
metal frame that is supported by two hydraulic cylinders near the upper
end of the bed. These telescopic cylinders extend to tilt the test bed
from its horizontal position to a 1V:2H slope gradient. The test bed is
designed to support a 60-cm (2-feet) depth of soil, which is sufficient
to allow placement and compaction of soil and the implementation of the
various surface treatment practices to evaluate their effect on erosion
rates.

The total usable surface area of the soil bed is 3 meters by 10 meters;
however, only a portion of the treated bed, 2 meters wide by 8 meters
long, is typically delineated for evaluation by the use of metal edging.
Runoff and sediment are directed to a flume at the toe of the slope and
conveyed to collection containers placed on the floor beneath the bed.

### 

## Water treatment and storage

In order to obtain accurate results from the rainfall simulation/erosion
rate evaluations, the municipal water supply is treated by reverse
osmosis and softened to remove minerals. The water treatment system
consists of a reverse osmosis unit, preceded by one activated carbon
vessel and two softening vessels arranged in series. Treated water is
stored in a 3,785-liter (1,000-gallon) polyethylene storage tank for use
in the laboratory simulations. When the simulators are transported for
the outdoor, vegetative coverage tests, truck-mounted tanks are used to
deliver treated water for rainfall simulations.

**SOIL ROUGHNESS TESTING**

Soil roughening is the creation of a soil surface roughness by
mechanical means. Typically, the roughening is performed parallel to the
slope contours and perpendicular to the direction of runoff. The
benefits provided by soil roughening are slowing runoff, enhancing
infiltration, moderating soil temperature, trapping moisture, and
enhancing seed germination and root penetration.

To evaluate the effectiveness of different roughness techniques in
reducing erosion rates for different storm events, roughness tests were
conducted at the SDSU/SERL using simulated storm events corresponding to
the 5-year, 10-year, and 50-year storms for the Los Angeles area. All
tests were run on a 2 meter wide x 8 meter long plot, using a clayey
sand soil, on a 1V:2H slope, with three (3) replications of each test
condition.

Runoff water and sediment collected at the end of the test bed were
separated mechanically. Water volumes and sediment weights were recorded
separately for each test replicate and each storm type. Runoff water was
reported as clear (supernatant) volume in liters, and sediment was
reported as dry weight in kilograms.

Roughness types that were tested included:

-   Smooth-rolled soil: The characteristics of a smooth-rolled,
    compacted surface were simulated by placing soil in the test bed,
    tilling it to uniform consistency, compacting it with hand tools,
    and lightly raking the surface.

-   Trackwalking: The characteristics of a trackwalked surface were
    simulated by first preparing the soil to a smooth-rolled condition,
    then placing a metal template on the surface to produce the required
    roughness. Three tracks from a Caterpillar D-9 bulldozer were welded
    together to form a template for the trackwalking procedure. A small
    gasoline-powered compactor was used to compress the tracks into the
    soil surface.

-   Sheepsfoot-Rolling: The roughness characteristic of a
    sheepsfoot-rolled slope was accomplished by designing and utilizing
    hand tools to create the appropriate impression in the soil surface.
    As with other roughness techniques, the soil surface was first
    tilled and compacted by hand before application of the sheepsfoot
    tool.

-   Ripping: To simulate the effect of ripping the surface with
    bulldozer tines, the soil was first tilled and compacted by hand.
    Following hand compaction, the soil surface was ripped to a depth of
    10 cm (4 in.) using a hand pick. The ripping was done perpendicular
    to the flow of water down the slope, with each incision 30-35cm
    (12-14 in.) apart.

-   Imprinting: The characteristic pattern of an imprinter/roller was
    replicated by utilizing a hand tool designed and constructed to the
    dimensions of an actual imprinting machine. The orientation, depth,
    and spacing were monitored and adjusted for consistency of surface
    preparation.

Roughness techniques are important for permanent stabilization in three
ways:

1.  Most techniques can be accomplished with existing on-site equipment
    so finished slopes have a margin of temporary protection until
    permanent vegetation is established.

2.  Roughness techniques complement most erosion control methodologies
    (i.e., hydraulic soil stabilization) making them perform better.

3.  Roughness techniques, through increased infiltration and decreased
    runoff of water, improve vegetation establishment.

**Results**

Dry sediment weight was subjected to an analysis of covariance with
roughness treatment and storm type as treatment factors and total runoff
volume as the covariate. Storm type and roughness treatments were highly
significant, as was the interaction between the two. Thus, both storm
type and roughness treatment influenced sediment weight, with the
effects of different roughness treatments depending significantly on
storm type. The covariate effect was not statistically significant, but
was strongly related to storm type. This may reflect the fact that storm
type is affected by factors other than just runoff (e.g., rainfall
intensity) that were not specifically addressed in this study.

The weight of discharged sediment was normalized based on the unit
surface area of the test bed and rainfall volume. Overall, sediment
discharge increased more with increased storm intensity than increased
storm volume (each Type (2) storm had a lower intensity and higher
volume than the Type (1) storm for the same return period). Ripping
produced slightly lower sediment yields than the smooth-rolled
(baseline). Sheepsfoot-rolling and trackwalking produced even lower
sediment yields, and were not significantly different from one another.
Imprinting produced significantly lower sediment yields than any other
treatment considered in this experiment. The superiority of the
imprinting treatment was roughly consistent across all the tested storm
types.

When making a decision as to which soil stabilization practice to
implement on a site, it is important to compare the performance of a
particular technique over a broad range of storms that might be
encountered during the construction period (e.g., 5-yr, 10‑yr, 50‑yr).
Therefore, a practical interpretation of the roughness data is expressed
in the last column of Table 1. This column shows the average, relative
increase or decrease in erosion or runoff for a particular roughness
practice, as compared to smooth rolled, over a wide range of storm
events.

The results of the soil roughness tests (normalized erosion rate and
runoff) are summarized in Figure 1. From Figure 1, some general
statements can be made:

-   The imprinting technique appears to be the most effective practice
    in reducing erosion (76 percent decrease in soil loss);

-   Sheepsfoot-rolling and trackwalking provide a good level of erosion
    control (55 percent and 52 percent decreases in soil loss,
    respectively);

-   Ripping provides the least effective erosion control (12 percent
    decrease in soil loss), but is most effective in reducing runoff (19
    percent decrease in runoff).

    **FIELD TESTING FOR VEGETATION DENSITY AND EROSION RATE**

The purpose of the outdoor laboratory testing was to demonstrate and
quantify the inverse relationship between vegetative cover and rate of
erosion; that is, as vegetation coverage increases, soil erosion rate
decreases. Two test locations were selected within the Los Angeles
Basin. Both sites were within Caltrans' right-of-ways, with one being
comprised of a fill slope and the other site a cut slope. At each site
three replicate, 2-meter wide x 8-meter long plots were established
utilizing metal edging and flumes to differentiate the side-by-side test
areas.

Each 2-meter x 8-meter plot was planted with 33 containerized plants of
*Myoporum sp.* *Myoporum* was chosen because its rapid growth
characteristics were well suited for the testing time frame and because
it is typically used for re-vegetation along Caltrans rights-of-way. The
plants were irrigated and grown to 100 percent coverage. Over a period
of 10 monoths, the plots were systematically pruned to cover percentages
of 35, 50, 65, 80, and 95 percent. Immediately following each pruning,
the rainfall simulators from the SDSU/SERL were used to rain on the
plots. Runoff and sediment was collected from each test and transported
to the SDSU/SERL for analysis.

This portion of the ECPS evaluated the effect of percent cover on
erosion rate and runoff volume under one test storm type (the 10-year
(2) storm for the Los Angeles area). Runoff water and sediment collected
at the end of each test plot were separated mechanically. Water volumes
and sediment weights were recorded separately for each test plot, each
site and for each vegetative cover percentage. Runoff water was reported
as clear (supernatant) volume in liters, and sediment was reported as
dry weight in kilograms.

**Results**

### 

Means and standard deviations of normalized erosion rate in kg/m^2^/mm
and runoff for the outdoor *Myoporum* tests are presented in Figures 2
and 3. The total weight of sediment recovered from each test was
measured in the SDSU/SERL. Sediment results were normalized by plot size
and rainfall depth. For the cut slopes, the data indicates a trend of
decreasing erosion rate with increased percent cover. The data for the
fill slope show less of a trend, decreasing at first (between 35 and 50
percent cover), then exhibiting a slight increase in erosion rate with
increasing cover. The reason for this difference is due to the effects
of gopher activity on the fill slopes.

Runoff amounts and sediment weights were subjected to analyses of
variance using slope type (site) and percent cover as treatment factors.
From the data, it appears that percent cover significantly influenced
runoff, but slope type (cut or fill) did not. Both percent cover and
slope type significantly influenced sediment weight. The interaction
between the two factors also significantly influenced sediment.

**SOIL STABILIZATION MEASURES**

This part of the ECPS addressed the erosion control effectiveness of
alternative erosion control products. The soil stabilization measures
provide a second step (after soil roughening) in the process of
establishing permanent erosion control vegetation. The 15 soil
stabilization measures that were evaluated are typically used in the
early stages of slope stabilization. Since vegetation takes time to grow
and may not provide effective erosion control for several months to
years, the soil stabilization measures provide interim erosion control,
and provide a nurturing environment for seeds and plants to become
established. Data collected during this portion of the study were
evaluated to establish a rank order of erosion control effectiveness
under the conditions of the test.

## Erosion rate tests 

The erosion rate tests on 15 soil stabilization measures were performed
at the SDSU/SERL indoor laboratory on a 1V:2H slope of clayey sand soil,
using the 10-year (2) storm event for the Los Angeles area. The plot
configuration consisted of three (3) replicate plots within the
simulator test bed, each 0.66 meters wide x 8 meters long

These measures included the following:

-   Bare soil (BARE)

-   Bonded fiber matrix (BFM)

-   Coconut blanket (CB)

-   Coir blanket (COIR)

-   Compost (COMP)

-   Curled wood fiber blanket (CWFB)

-   Gypsum treatment (GYP)

-   Paper mulch with psyllium (PMG)

-   Paper mulch with polymer (PMP)

-   Wheat straw incorporated (RS)

-   Straw blanket (SB)

-   Straw-coconut blanket (SCB)

-   Wood fiber blanket (WFB)

-   Wood mulch with psyllium (WMG)

-   Wood mulch with polymer (WMP)

During the test, all sediment and runoff were collected in containers at
the end of the test bed and separated mechanically. Water volumes and
sediment weights were recorded separately for each test replicate.
Runoff water was reported as clear (supernatant) volume in liters, and
sediment was reported as dry weight in kilograms.

**Results**

Results of the erosion rate study with respect to normalized erosion
rate and percent change in runoff for the soil stabilization measures
that were tested are shown in Figure 4. Overall, the table illustrates
that all of the erosion control products tested greatly reduced the
amount of soil loss.

The range of erosion control performance in this study was consistent
with what has been observed in previous rainfall simulation testing at
both the Utah Water Research Laboratory (UWRL) and the Texas
Transportation Institute (TTI):

-   Erosion control effectiveness of most rolled erosion control
    products (RECPs) is in the 90-100% range;

-   Hydraulic applications of bonded fiber matrix (BFM) perform in the
    same range of effectiveness as RECPs; and

-   Hydraulic applications of mulch (wood fiber or paper) are notably
    less effective in controlling erosion, although in this study their
    performance appears to be substantially enhanced by the addition of
    a binder (psyllium or polymer).

Based on the results of this laboratory study, each of the treatments
was rated according to its effectiveness in reducing erosion rate
(Figure 5). Figure 6 illustrates the increase or decrease in runoff from
the plots tested as compared to runoff from the bare plots. Six of the
products resulted in a decrease in runoff, with the largest decrease
(approximately 90 percent) coming from the coconut blanket (CB) plot.
Eight of the products resulted in increased runoff.

Evaluation of the change in the runoff of the treated plots compared to
the bare soil (control) condition yielded the anticipated results; that
is, the more physically stable materials (i.e., RECPs, BFM, incorporated
straw) were more successful at decreasing runoff.

There were, however, some notable exceptions:

-   The coconut blanket (CB) performed at a higher rate than expected.
    This is possibly due to retention of sediment and water at the toe
    of the plot. This phenomenon, observed in many field applications,
    creates a "pillow" of water and sediment behind the closely-woven
    fibers of coconut at the downslope portion of the blanket where it
    is trenched in or heavily stapled.

-   The paper mulch with polymer binder (PMP) reduced runoff at a much
    higher rate than similar hydraulic applications. From the material's
    historic performance in similar tests (USWRL/TTI) one would have
    expected an increase in runoff similar to the paper mulch with
    psyllium (PMG), wood mulch with psyllium (WMG), and wood mulch with
    polymer (WMP) plots.

### **CONCLUSIONS**

The objective of the ECPS was to evaluate alternative permanent soil
stabilization methods designed to minimize the transport of sediment
from cut and fill slopes within Caltrans District 7 rights-of-way to
storm drain inlets. The basic assumption of the pilot study was that
erosion of slopes can be reduced by increasing the percentage of
vegetative cover on cut and fill slopes to provide soil protection from
wind and water.

## Evaluation of slope roughness

Soil roughening is complementary to most soil stabilization techniques,
such as hydraulic mulches that can be applied over the surface roughness
treatment. The surface roughness provides a permanent slope surface
configuration that works in conjunction with the short-term soil
stabilization and permanent vegetation to provide an effective erosion
control system.

Five surface roughness techniques were evaluated as part of this study:
smooth rolling, sheepsfoot-rolling, ripping, trackwalking, and
imprinting. The five soil roughness techniques were evaluated against
one criterion, erosion rate. The five techniques were rated with respect
to how they performed during the erosion rate testing.

**Vegetative Cover**

Low percent cover (less than 50%) of *Myoporum* leads to large amounts
of runoff. Higher values of percent cover (greater than 50%) lead to
lower amounts of runoff; however, values of percent cover (65% or more)
do not differ appreciably in their ability to reduce runoff. The pattern
is different for sediment loss. High values of percent cover (90% or
greater) lead to low sediment losses, intermediate values of percent
cover (65% to 85%) lead to intermediate sediment losses, and low values
of percent cover (50% or less) lead to high sediment losses.

**Soil Stabilization Measures**

The soil stabilization measures tested in this study can be ranked in
accordance with the criteria that were evaluated as part of the ECPS
testing program, such as erosion rate and runoff volume. However,
testing of these materials does not indicate approval or disapproval of
a particular method. At this time, Caltrans does not hold any method or
material to a numerical standard of performance, since there are other
evaluation criteria that should be considered when selecting an
appropriate erosion control measure for a given set of site conditions.
Examples of other selection criteria include:

-   Long-term cost (maintenance)

-   Environmental compatibility

-   Regulatory acceptability

-   Availability

-   Durability

-   Longevity

-   Feasibility

-   Public acceptability

-   Risk/liability

-   Suitability for the site

These site and project-specific criteria can be added to the numerical
quantification of erosion control performance obtained from the ECPS.
Field and design engineers thus have a wealth of new information on
which to make sound decisions when selecting from a diverse group of
erosion control materials and methods.

Figure 1\
RESULTS OF RAINFALL SIMULATION TESTING FOR ROUGHNESS

<table>
<colgroup>
<col style="width: 11%" />
<col style="width: 18%" />
<col style="width: 11%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 11%" />
</colgroup>
<tbody>
<tr class="odd">
<td rowspan="2">Treatment</td>
<td rowspan="2">Measurement</td>
<td rowspan="2">Statistic</td>
<td colspan="6">Storm</td>
<td rowspan="2"><p>Average</p>
<p>Increase (+)</p>
<p>Decrease (-)</p></td>
</tr>
<tr class="even">
<td>5-yr (1)</td>
<td>5-yr (2)</td>
<td>10-yr (1)</td>
<td>10-yr (2)</td>
<td>50-yr (1)</td>
<td>50-yr (2)</td>
</tr>
<tr class="odd">
<td rowspan="6">Smooth</td>
<td rowspan="2">Normalized Erosion Rate (kg/m<sup>2</sup>/mm)</td>
<td>Mean</td>
<td>0.06</td>
<td>0.07</td>
<td>0.16</td>
<td>0.09</td>
<td>0.12</td>
<td>0.09</td>
<td></td>
</tr>
<tr class="even">
<td>St. Dev.</td>
<td>0.03</td>
<td>0.07</td>
<td>0.04</td>
<td>0.01</td>
<td>0.02</td>
<td>0.02</td>
<td></td>
</tr>
<tr class="odd">
<td></td>
<td>% of Smooth</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td><strong>0%</strong></td>
</tr>
<tr class="even">
<td rowspan="3">Runoff (L)</td>
<td>Mean</td>
<td>255.7</td>
<td>364.4</td>
<td>419.2</td>
<td>470.3</td>
<td>422.3</td>
<td>611.0</td>
<td></td>
</tr>
<tr class="odd">
<td>St. Dev.</td>
<td>11.9</td>
<td>35.1</td>
<td>19.6</td>
<td>9.7</td>
<td>10.6</td>
<td>20.3</td>
<td></td>
</tr>
<tr class="even">
<td>% of Smooth</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td>100%</td>
<td><strong>0%</strong></td>
</tr>
<tr class="odd">
<td rowspan="6">Imprinted</td>
<td rowspan="3">Normalized Erosion Rate (kg/m<sup>2</sup>/mm)</td>
<td>Mean</td>
<td>0.03</td>
<td>0.02</td>
<td>0.03</td>
<td>0.02</td>
<td>0.03</td>
<td>0.02</td>
<td></td>
</tr>
<tr class="even">
<td>St. Dev.</td>
<td>0.03</td>
<td>0.19</td>
<td>0.11</td>
<td>0.12</td>
<td>0.04</td>
<td>0.05</td>
<td></td>
</tr>
<tr class="odd">
<td>% of Smooth</td>
<td>49%</td>
<td>26%</td>
<td>18%</td>
<td>25%</td>
<td>22%</td>
<td>19%</td>
<td><strong>76% (-)</strong></td>
</tr>
<tr class="even">
<td rowspan="3">Runoff (L)</td>
<td>Mean</td>
<td>222.3</td>
<td>415.6</td>
<td>380.8</td>
<td>446.6</td>
<td>464.4</td>
<td>501.8</td>
<td></td>
</tr>
<tr class="odd">
<td>St. Dev.</td>
<td>13.3</td>
<td>96.1</td>
<td>49.4</td>
<td>84.0</td>
<td>21.1</td>
<td>37.8</td>
<td></td>
</tr>
<tr class="even">
<td>% of Smooth</td>
<td>87%</td>
<td>114%</td>
<td>91%</td>
<td>95%</td>
<td>110%</td>
<td>82%</td>
<td><strong>4% (-)</strong></td>
</tr>
<tr class="odd">
<td rowspan="6">Ripped</td>
<td rowspan="3">Normalized Erosion Rate (kg/m<sup>2</sup>/mm)</td>
<td>Mean</td>
<td>0.04</td>
<td>0.07</td>
<td>0.12</td>
<td>0.08</td>
<td>0.15</td>
<td>0.06</td>
<td></td>
</tr>
<tr class="even">
<td>St. Dev.</td>
<td>0.18</td>
<td>0.03</td>
<td>0.07</td>
<td>0.04</td>
<td>0.01</td>
<td>0.09</td>
<td></td>
</tr>
<tr class="odd">
<td>% of Smooth</td>
<td>66%</td>
<td>99%</td>
<td>75%</td>
<td>88%</td>
<td>121%</td>
<td>71%</td>
<td><strong>12% (-)</strong></td>
</tr>
<tr class="even">
<td rowspan="3">Runoff (L)</td>
<td>Mean</td>
<td>154.2</td>
<td>276.3</td>
<td>387.3</td>
<td>416.3</td>
<td>373.5</td>
<td>443.4</td>
<td></td>
</tr>
<tr class="odd">
<td>St. Dev.</td>
<td>75.6</td>
<td>17.0</td>
<td>29.8</td>
<td>24.7</td>
<td>7.0</td>
<td>79.2</td>
<td></td>
</tr>
<tr class="even">
<td>% of Smooth</td>
<td>60%</td>
<td>76%</td>
<td>92%</td>
<td>89%</td>
<td>88%</td>
<td>73%</td>
<td><strong>19% (-)</strong></td>
</tr>
<tr class="odd">
<td rowspan="6">Sheepsfoot</td>
<td rowspan="3">Normalized Erosion Rate (kg/m<sup>2</sup>/mm)</td>
<td>Mean</td>
<td>0.03</td>
<td>0.03</td>
<td>0.02</td>
<td>0.05</td>
<td>0.06</td>
<td>0.04</td>
<td></td>
</tr>
<tr class="even">
<td>St. Dev.</td>
<td>0.03</td>
<td>0.14</td>
<td>0.06</td>
<td>0.03</td>
<td>0.04</td>
<td>0.03</td>
<td></td>
</tr>
<tr class="odd">
<td>% of Smooth</td>
<td>58%</td>
<td>46%</td>
<td>14%</td>
<td>56%</td>
<td>51%</td>
<td>46%</td>
<td><strong>55% (-)</strong></td>
</tr>
<tr class="even">
<td rowspan="3">Runoff (L)</td>
<td>Mean</td>
<td>361.3</td>
<td>374.8</td>
<td>525.1</td>
<td>511.8</td>
<td>503.3</td>
<td>584.4</td>
<td></td>
</tr>
<tr class="odd">
<td>St. Dev.</td>
<td>11.9</td>
<td>71.3</td>
<td>26.7</td>
<td>22.5</td>
<td>26.0</td>
<td>24.3</td>
<td></td>
</tr>
<tr class="even">
<td>% of Smooth</td>
<td>141%</td>
<td>103%</td>
<td>125%</td>
<td>109%</td>
<td>119%</td>
<td>96%</td>
<td><strong>12% (+)</strong></td>
</tr>
<tr class="odd">
<td rowspan="4">Trackwalked</td>
<td rowspan="3">Normalized Erosion Rate (kg/m<sup>2</sup>/mm)</td>
<td>Mean</td>
<td>0.04</td>
<td>0.04</td>
<td>0.05</td>
<td>0.04</td>
<td>0.04</td>
<td>0.07</td>
<td></td>
</tr>
<tr class="even">
<td>St. Dev.</td>
<td>0.11</td>
<td>0.05</td>
<td>0.08</td>
<td>0.06</td>
<td>0.09</td>
<td>0.04</td>
<td></td>
</tr>
<tr class="odd">
<td>% of Smooth</td>
<td>80%</td>
<td>60%</td>
<td>30%</td>
<td>40%</td>
<td>30%</td>
<td>80%</td>
<td><strong>52% (-)</strong></td>
</tr>
<tr class="even">
<td rowspan="3">Runoff (L)</td>
<td>Mean</td>
<td>218.7</td>
<td>448.3</td>
<td>460.7</td>
<td>468.5</td>
<td>410.6</td>
<td>579.9</td>
<td></td>
</tr>
<tr class="odd">
<td></td>
<td>St. Dev.</td>
<td>48.0</td>
<td>26.8</td>
<td>35.5</td>
<td>38.4</td>
<td>49.7</td>
<td>36.0</td>
<td></td>
</tr>
<tr class="even">
<td></td>
<td>% of Smooth</td>
<td>86%</td>
<td>123%</td>
<td>110%</td>
<td>100%</td>
<td>97%</td>
<td>95%</td>
<td><strong>2% (+)</strong></td>
</tr>
</tbody>
</table>

Figure 2\
RESULTS OF RAINFALL SIMULATION TESTING ON MYOPORUM TEST PLOTS

  --------------- -------------- ----------------- ----------- -----------
  Percent Cover   Measurement    Statistic         Cut Slope   Fill Slope

  35              Normalized\    Mean              0.015       0.0078
                  Erosion Rate\                                
                  (kg/m^2^/mm)                                 

                                 *Std. Dev.*       *0.0019*    *0.0079*

                  Runoff (L)     Mean              303.7       96.9

                                 *Std. Dev.*       *80.7*      *6.0*

                                 As % of Rainfall  44%         14%
                                 Volume                        

  50              Normalized\    Mean              0.0049      0.0026
                  Erosion Rate\                                
                  (kg/m^2^/mm)                                 

                                 *Std. Dev.*       *0.0019*    *0.0019*

                  Runoff (L)     Mean              195.8       144.1

                                 *Std. Dev.*       *11.6*      *15.5*

                                 As % of Rainfall  28%         21%
                                 Volume                        

  65              Normalized\    Mean              0.0019      0.0007
                  Erosion Rate\                                
                  (kg/m^2^/mm)                                 

                                 *Std. Dev.*       *0.0008*    *0.0003*

                  Runoff (L)     Mean              144.3       105.7

                                 *Std. Dev.*       *40.2*      *19.8*

                                 As % of Rainfall  21%         15%
                                 Volume                        

  80              Normalized\    Mean              0.0029      0.0012
                  Erosion Rate\                                
                  (kg/m^2^/mm)                                 

                                 *Std. Dev.*       *0.0024*    *0.0006*

                  Runoff (L)     Mean              122.7       149.6

                                 *Std. Dev.*       *19.9*      *15.0*

                                 As % of Rainfall  18%         21%
                                 Volume                        

  90              Normalized\    Mean              0.0003      0.0024
                  Erosion Rate\                                
                  (kg/m^2^/mm)                                 

                                 *Std. Dev.*       *0.0002*    *0.0015*

                  Runoff (L)     Mean              40.4        104.4

                                 *Std. Dev.*       *14.8*      *8.8*

                                 As % of Rainfall  6%          21%
                                 Volume                        

                                                               
  --------------- -------------- ----------------- ----------- -----------

![](media/image1.wmf)Figure 3\
NORMALIZED EROSION RATE FROM MYOPORUM PLOTS BY PERCENT PLANT COVER

Figure 4\
RESULTS OF EROSION RATE TESTS FOR SOIL STABILIZATION MEASURES
(NORMALIZED SEDIMENT DATA)

  --------------- ----------------- --------------- ----------- -- --------------- ----------------- --------------- -----------
  **Treatment**   **Measurement**   **Statistic**   **Value**      **Treatment**   **Measurement**   **Statistic**   **Value**

  Bare            Normalized        Mean            0.116          Paper Mulch     Normalized        Mean            0.045
                  Erosion Rate                                     with Psyllium   Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

                                    *Std. Dev.*     *0.038*        (PMG)                             *Std. Dev.*     *0.016*

                  Runoff (L)        Mean            153.9                          Runoff (L)        Mean            195.7

                                    *Std. Dev.*     *0.3*                                            *Std. Dev.*     *10.8*

                                    \% of Rainfall  30%                                              \% of Rainfall  39%
                                    Volume                                                           Volume          

  Bonded Fiber    Normalized        Mean            0.000          Straw Blanket   Normalized        Mean            0.002
  Matrix          Erosion Rate                                     (SB)            Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

  (BFM)                             *Std. Dev.*     *0.000*                                          *Std. Dev.*     *0.000*

                  Runoff (L)        Mean            130.8                          Runoff (L)        Mean            126.0

                                    *Std. Dev.*     *34.8*                                           *Std. Dev.*     *24.7*

                                    \% of Rainfall  26%                                              \% of Rainfall  25%
                                    Volume                                                           Volume          

  Coconut Blanket Normalized        Mean            0.000          Straw-Coconut   Normalized        Mean            0.004
  (CB)            Erosion Rate                                     Blanket (SCB)   Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

                                    *Std. Dev.*     *0.000*                                          *Std. Dev.*     *0.002*

                  Runoff (L)        Mean            17.5                           Runoff (L)        Mean            157.1

                                    *Std. Dev.*     *4.9*                                            *Std. Dev.*     *6.8*

                                    \% of Rainfall  3%                                               \% of Rainfall  31%
                                    Volume                                                           Volume          

  Coir (COIR)     Normalized        Mean            0.007          Wood Fiber      Normalized        Mean            0.002
                  Erosion Rate                                     Blanket (WFB)   Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

                                    *Std. Dev.*     *0.002*                                          *Std. Dev.*     *0.000*

                  Runoff (L)        Mean            153.5                          Runoff (L)        Mean            182.7

                                    *Std. Dev.*     *20.2*                                           *Std. Dev.*     *14.3*

                                    \% of Rainfall  30%                                              \% of Rainfall  36%
                                    Volume                                                           Volume          

  Compost (COMP)  Normalized        Mean            0.071          Wood Mulch with Normalized        Mean            0.058
                  Erosion Rate                                     Polymer         Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

                                    *Std. Dev.*     *0.024*        (WMP)                             *Std. Dev.*     *0.008*

                  Runoff (L)        Mean            173.9                          Runoff (L)        Mean            226.6

                                    *Std. Dev.*     *23.6*                                           *Std. Dev.*     *8.1*

                                    \% of Rainfall  34%                                              \% of Rainfall  45%
                                    Volume                                                           Volume          

  Curled Wood     Normalized        Mean            0.011          Wood Mulch with Normalized        Mean            0.015
  Fiber           Erosion Rate                                     Psyllium        Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

  Blanket (CWFB)                    *Std. Dev.*     *0.003*        (WMG)                             *Std. Dev.*     *0.003*

                  Runoff (L)        Mean            157.6                          Runoff (L)        Mean            182.4

                                    *Std. Dev.*     *26.1*                                           *Std. Dev.*     *8.5*

                                    \% of Rainfall  31%                                              \% of Rainfall  36%
                                    Volume                                                           Volume          

  Gypsum          Normalized        Mean            0.027          Wheat Straw     Normalized        Mean            0.005
                  Erosion Rate                                     Incorporated    Erosion Rate                      
                  (kg/m^2^/mm)                                                     (kg/m^2^/mm)                      

  (GYP)                             *Std. Dev.*     *0.005*        (RS)                              *Std. Dev.*     *0.004*

                  Runoff (L)        Mean            165.7                          Runoff (L)        Mean            112.7

                                    *Std. Dev.*     *14.5*                                           *Std. Dev.*     *12.6*

                                    \% of Rainfall  24%                                              \% of Rainfall  22%
                                    Volume                                                           Volume          

  Paper Mulch     Normalized        Mean            0.029          Note: Gypsum                                      
  with            Erosion Rate                                     (GYP) erosion                                     
                  (kg/m^2^/mm)                                     rate was tested                                   
                                                                   as part of the                                    
                                                                   Soil                                              
                                                                   Stabilization                                     
                                                                   for Temporary                                     
                                                                   Slopes study                                      
                                                                   that was                                          
                                                                   performed                                         
                                                                   between                                           
                                                                   September and                                     
                                                                   December 1999.                                    
                                                                   Specific                                          
                                                                   results for                                       
                                                                   that study were                                   
                                                                   presented in a                                    
                                                                   *Field Guide*                                     
                                                                   and supporting                                    
                                                                   *Guidance                                         
                                                                   Document*,                                        
                                                                   dated November                                    
                                                                   30, 1999.                                         

  Polymer (PMP)                     *Std. Dev.*     *0.003*                                                          

                  Runoff (L)        Mean            94.6                                                             

                                    *Std. Dev.*     *8.2*                                                            

                                    \% of Rainfall  19%                                                              
                                    Volume                                                                           
  --------------- ----------------- --------------- ----------- -- --------------- ----------------- --------------- -----------

Figure 5\
PERCENT EROSION REDUCTION FROM BARE SOIL

![](media/image2.wmf)

Figure 6\
PERCENT CHANGE IN RUNOFF FROM BARE SOIL

![](media/image3.wmf)