United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical

Report RMRS-GTR-240

August 2010

Post-Fire Treatment 

Effectiveness for 

Hillslope Stabilization

Peter R. Robichaud, Louise E. Ashmun, and Bruce D. Sims

A SUMMARY OF

KNOWLEDGE FROM THE
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Authors

Peter R. Robichaud is a Research Engineer with the Air, Watershed, and Aquatics Science Program at the Rocky Mountain 

Research Station’s Forestry Sciences Laboratory in Moscow, 

Idaho. He develops and implements research protocols for 

measuring and predicting post-fire runoff and erosion and 

post-fire treatment effectiveness.

Louise E. Ashmun is a Civil Engineer with the Air, Watershed, 

and Aquatics Science Program at the Rocky Mountain Research 

Station’s Forestry Sciences Laboratory in Moscow, Idaho. She 

provides technical support for research and technology transfer 

on grant-funded projects.

Bruce D. Sims is the Regional Hydrologist for the Northern 

Region of the USDA Forest Service in Missoula, Montana. 

His duties include oversight of the Burned Area Emergency 

Response (BAER) program for the Region.

Robichaud, Peter R.; Ashmun, Louise E.; Sims, Bruce D. 2010. Post-fire treatment effectiveness for hillslope stabilization. Gen. Tech. Rep. RMRS-GTR-240. Fort Collins, CO: U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station. 62 p.

Abstract

This synthesis of post-fire treatment effectiveness reviews the past decade of research, monitoring, and 

product development related to post-fire hillslope emergency stabilization treatments, including erosion barriers, mulching, chemical soil treatments, and combinations of these treatments. In the past ten years, erosion 

barrier treatments (contour-felled logs and straw wattles) have declined in use and are now rarely applied 

as a post-fire hillslope treatment. In contrast, dry mulch treatments (agricultural straw, wood strands, wood 

shreds, etc.) have quickly gained acceptance as effective, though somewhat expensive, post-fire hillslope 

stabilization treatments and are frequently recommended when values-at-risk warrant protection. This change 

has been motivated by research that shows the proportion of exposed mineral soil (or conversely, the proportion of ground cover) to be the primary treatment factor controlling post-fire hillslope erosion. Erosion barrier 

treatments provide little ground cover and have been shown to be less effective than mulch, especially during 

short-duration, high intensity rainfall events. In addition, innovative options for producing and applying mulch 

materials have adapted these materials for use on large burned areas that are inaccessible by road. Although 

longer-term studies on mulch treatment effectiveness are on-going, early results and short-term studies have 

shown that dry mulches can be highly effective in reducing post-fire runoff and erosion. Hydromulches have 

been used after some fires, but they have been less effective than dry mulches in stabilizing burned hillslopes 

and generally decompose or degrade within a year.

Keywords: BAER, contour-felled logs, hydromulch, LEB, straw mulch, PAM, wood shreds, wood strands

Acknowledgments

This synthesis project (Project Number 08-2-1-10) was 

funded by the Joint Fire Sciences Program, a collaborative 

between the U.S. Department of Interior and U.S. Department 

of Agriculture, Forest Service that supports fire research. Much 

of the research reported herein was funded wholly or in part 

by the Joint Fire Sciences Program. We are indebted to our 

reviewers: Jeff Bruggink, Chris Holbeck, Carolyn Napper, and 

Wayne Robbie. They all have wide-ranging experience on 

post-fire assessment teams, and their comments significantly 

improved this document and the companion web page (http://

forest.moscowfsl.wsu.edu/BAERTOOLS/HillslopeTrt). We 

specifically recognize and thank John Moody, who provided a 

thorough review of the draft document and made suggestions 

that greatly enhanced the focus, content, and organization of 

this synthesis.
i

Contents

Preface	............................................................................................................. ii

Scope of Post-Fire Treatment Effectiveness for

	 Hillslope Stabilization................................................................... ii

Introduction	.....................................................................................................1

Post-Fire Treatment Types...................................................................1

Post-Fire Treatment Effectiveness and Treatment Performance..........2

Post-Fire Hydrology and Erosion ....................................................................2

Factors That Impact Post-Fire Watershed Response and

	 Treatment Effectiveness.................................................................4

Post-Fire Erosion by Wind and Gravity...............................................8

Comparing Results and Scale of Measurements..................................8

Erosion Barrier Treatments............................................................................10

Erosion Barrier Performance Characteristics.....................................12

Erosion Barrier Treatment Effectiveness...........................................14

Mulch Treatments..........................................................................................15

Dry Mulches.......................................................................................16

Hydromulches....................................................................................17

Performance Characteristics of Mulches...........................................18

Mulch Treatment Effectiveness .........................................................24

Chemical Soil Surface Treatments.................................................................27

Performance Characteristics of PAM and Other Polymers................28

Effectiveness of PAM and Other Polymers .......................................29

Treatment Combination .................................................................................29

Management Implications..............................................................................30

Longer-Term Treatment Effectiveness...............................................30

Choosing Treatments .........................................................................30

Monitoring Post-Fire Treatment Effectiveness..................................33

Using the “Best Available” Treatments..............................................33

References......................................................................................................33

Appendix A: Hillslope Treatment Effectiveness and Performance

	 Characteristics Summary Table.............................................................38

Appendix B: Erosion Barrier Treatment Effectiveness Studies

	 (2000 to the present)..............................................................................39

Appendix C: Mulch Treatment Effectiveness Studies

	 (2000 to the present)..............................................................................48

Appendix D: Polyacrylamide (PAM) Treatment Effectiveness Studies

	 (2000 to the present)..............................................................................59

Appendix E: Combination Treatments Effectiveness Studies

	 (2000 to present)....................................................................................61
ii

Preface

This report is a synthesis of post-fire emergency hillslope stabilization treatment effectiveness information that 

was written to provide guidance for future post-fire treatment selection and use. It builds on an earlier synthesis, 

Evaluating the Effectiveness of Postfire Rehabilitation 

Treatments (Robichaud and others 2000) (fig. 1). Since 

that publication, the effectiveness of emergency postfire hillslope treatments have been evaluated in several 

scientific studies and treatment monitoring reports prepared by Burned Area Emergency Response (BAER) 

and Emergency Stabilization and Rehabilitation (ESR) 

teams. In addition, our knowledge of how environmental 

factors impact treatment effectiveness and the development of new post-fire hillslope treatment products and 

application techniques has grown. The objective of this 

document is to synthesize that new information in a format 

that is easily accessible by post-fire assessment teams 

and land managers.

Scope of Post-Fire Treatment 

Effectiveness for Hillslope Stabilization

This synthesis focuses on post-fire hillslope emergency 

stabilization treatments, including erosion barriers, mulching, chemical soil treatments, and combinations of these 

treatments. This is a narrow focus given the range of postfire emergency responses typically implemented by BAER 

teams (see Napper 2006 for a comprehensive review of 

post-fire treatments). However, these hillslope treatments 

are usually the most expensive post-fire treatments used, 

which makes cost effectiveness an important factor in 

their selection. In addition, recent reports synthesize the 

current information for other post-fire emergency treatments. For example, a synthesis of broadcast seeding, 

one of the first and most extensively used post-fire hillslope 

treatments (Robichaud and others 2000), is discussed in 

papers being prepared by Jan Beyers (Pacific Southwest 

Research Station), Carolyn Hull Sieg (Rocky Mountain 

Research Station), Peter Fulé and colleagues (Northern 

Arizona University), and David Pyke (U.S. Geological 

Survey). Consequently, seeding is only included in 

this report when it was used in combination with other 

hillslope treatments. Post-fire stabilization treatments for 

roads are frequently implemented to facilitate the passage 

of potentially larger post-fire water flows that may damage roadways, culverts, bridges, etc. These treatments 

and their known effectiveness have been addressed in 

A Synthesis of Post-Fire Road Treatments for BAER 

Teams (Foltz and others 2009) and are not included in 

this synthesis.

Post-fire treatments to stabilize channels or deflect 

large channel flows are occasionally recommended after 

wildfires, but there are few quantified data on treatment 

performance, and those treatments are not discussed in 

this document. However, some hillslope treatment effectiveness studies have been done on swales, hillslope plots 

that contain two convergent hillslopes that form a zeroorder channel, and small catchments that contain one or 

more low-order channels with a clearly defined outlet. In 

these studies, the measured eroded sediment is trapped 

at the base of the hillslope swale or at the outlet of the 

low-order catchment channel system and includes the 

eroded sediment from the hillslopes and channels within 

the contributing area. Those studies are included in this 

synthesis because hillslope stabilization treatments (as 

opposed to channel treatments) were evaluated.

Figure 1. Cover of RMRS-GTR-63 (Robichaud and 

others 2000). 
iii

We have synthesized the available post-fire hillslope 

treatment effectiveness research and monitoring data that 

apply to the United States. However, with few exceptions, 

the data are from studies done in the western United 

States. There are some post-fire hillslope treatment 

studies from Europe, particularly Spain and Portugal, but 

the majority of the relevant research is from the western 

United States where hillslope treatments have been 

implemented after large wildfires. Wildfires do occur in the 

central and eastern United States, but post-fire hillslope 

stabilization treatments are rarely implemented, and there 

are few or no available data on treatment effectiveness. 

Generally, post-fire recovery occurs more rapidly in these 

wetter climates than in the drier western forest. However, 

with climate change, the risk of larger and more severe 

wildfires is becoming increasingly important in areas like 

the southeastern piedmont forests (Crumbley and others 

2007). The treatment effectiveness information that has 

been generated in the western United States will likely 

apply to other areas if post-fire treatments are warranted.

Side Bars

Side bars are the shaded boxes outside the main report 

narrative that contain unpublished treatment information 

that is more anecdotal than scientific. They are included 

to illustrate a decision-making process, describe an interesting observation, or show how environmental factors 

impacted the effectiveness of a treatment.

All photos are from the USDA Forest Service, unless otherwise noted.

The use of trade or firm names in this publication is for reader information and does not 

imply endorsement by the U.S. Department of Agriculture of any product or service.

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 1

Introduction ____________________

Wildfires continue to be amajorlandmanagement concern in the United States and throughout the world. The

number and severity of wildfires in the United States has

increasedduringthepastdecade(NationalInteragencyFire

Center2009),andtheriseislikelytocontinue,especiallyin

thewesternUnitedStateswheredrought andother effects

of climate change are exacerbating wildfire conditions

(Brown and others 2004; Flannigan and others 2000;

Miller and others 2009; Westerling and others 2006). At

the sametime,thenumberofpeople livinginthewildlandurban interface continues to grow, putting human life

and safety, infrastructure, homes, buildings, and natural

areasthatsupportlivelihoods(grazing,timber, etc.) atrisk

fromwildfire and secondary fire effectssuch asincreased

runoff, flooding, erosion, and debris flows (Stewart and

others 2003). Mitigating these fire effects has resulted

in increased use of post-fire treatments (Robichaud and

others 2000; Robichaud 2005).

Realistic and verifiable assessments of post-fire treatment effectiveness are essential if post-fire assessment

teams are to choose treatments that balance protection

of public safety and values-at-risk with justifiable, costeffective expenditures of public funds(GAO 2003, 2006).

Managersalsoneedtoknowhowandwhytreatmentswork

so they can determine the best treatment(s) for a specific

location and decide how to adapt treatments to improve

their effectiveness. For example, the formulation and

application rate of mulches can be modified to enhance

specific qualities such as longevity, adherence to soil,

interlockingofmulchstrands,etc.BurnedAreaEmergency

Response (BAER) teams and Emergency Stabilization

and Rehabilitation (ESR) teams may vary treatment

components and implementation processes (for example,

mulch type and formulation,seed content, and application

rate) in response to the specific climate, soil, vegetation,

and topography of the treatment area. Consequently, this

synthesis of post-fire hillslope treatment effectiveness

discusses treatment characteristics as they relate to the

treatment performance, as well as the effectiveness of

various treatments for emergency hillslope stabilization.

Post-Fire Treatment Types

Post-fire treatment activities are divided into three

categories—emergency stabilization, rehabilitation, and

restoration—that are differentiated by objectives, types,

and timing of the processes (GAO 2006). Emergency

stabilization treatments (such as mulching to prevent soil

erosion, installation of water bars to facilitate water passage over roads, etc.) are conducted within one year of a

fire to stabilize the burned area, protect public health and

safety, and reduce the risk of additional damage to valued

resourcessuchaswatersupplysystems,criticalhabitat,and

infrastructure.Theburnedareaassessmentandemergency

stabilization plans are implemented assoon as possible in

an effortto place treatments before the first damaging rain

events are likely to occur (Robichaud and others 2000).

Emergency stabilization activities may be followed by

years of rehabilitation and restoration activities (GAO

2006). These longer-term activities can include repair

of facilities needed for access and recreation (road and

bridge repair, fencing, and facility repair or replacement)

and mitigation of land damage that is unlikely to recover

to a desired condition on its own (tree or grass planting,

noxiousweedcontrol,andfuelreduction).BAERactivities

are restricted to assessing the need for and implementing

emergencypost-fire stabilizationtreatments “thatprovide

essential and demonstrated protection at minimum cost

while meeting emergency stabilization objectives”

(USDA Forest Service Manual 2004, Section 2523.03);

however, emergency stabilization treatments may have

long-term impacts. Treatment types that are known to

enhance, or at least not impede, natural recovery and

potential restoration effortsshould be favored when treatments are selected for emergency stabilization (Franklin

and Agee 2003). Unfortunately, there are few studies

on long-term effects of broadcast hillslope stabilization

treatments, such as straw mulch or hydromulch, despite

their growing use.

Post-Fire Treatment Effectiveness for 

Hillslope Stabilization

Peter R. Robichaud, Louise E. Ashmun, Bruce D. Sims
2 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Post-Fire Treatment Effectiveness and 

Treatment Performance

For the purposes of this synthesis, we have differentiated “treatment effectiveness” from “treatment performance.”Treatment effectiveness will describe how well

a treatment meets emergencystabilizationobjectives.For

example,ifstrawmulchwasappliedtoburnedhillslopesto

reduce peak flow rates and sediment yields, the treatment

effectivenesswouldbethereductioninthosetwovariables

that could be ascribed to the treatment. Measured peak

flow rates and sediment yields from equivalent treated

and untreated areas would be compared to make that

determination (Robichaud 2005). Differences between

the treated and untreated areas are generally expressed in

percent difference and are often described asthe “percent

reduction due to treatment.”1 In contrast, treatment performance is related to the materials used in the treatment

(for example, thickness ofstraw stalks and length of wood

strands), installation features (for example, percent cover

and depth of straw), and changes over time (for example,

movement by wind and decay rate). Treatment performance characteristics can affect treatment effectiveness,

which is why they are assessed and monitored in addition

to treatment effectiveness. However, emergency hillslope

treatment effectivenessinformation (generally, reduction

in runoff, peak flows, and/or sediment yields) can be difficult to interpret when combined with measurements of

treatment performance.

Although the need to measure treatment effectiveness

has gained acceptance, there are limited data to determine if post-fire treatments are practical and effective.

Field measurements of runoff and/or sediment yields in

burned areas require a rapid response research protocol

(Lentile and others 2007) and are generally expensive and

labor-intensive. Such studies are challenging to fund and

sustain over time. Nonetheless, quantitative treatment

effectiveness data influence treatment decisions.

1 Percent reduction can be misleading when the quantities being

compared are small relative to the units of measure. For example,

consider the following: The mean sediment yield from treated plots

was 0.001 ton ac–1 (0.002 Mg ha–1) or about 20 pounds of soil

(~one-half of a 5-gallon bucket) from an acre. The mean sediment

yield from untreated control plots was 0.01 ton ac–1 (0.02 Mg ha–1)

or about 200 pounds of soil [~5 full 5-gallon buckets] from an acre.

In this case, the percent reduction due to treatment is 90 percent—

likely a statistically significant treatment effect. However, the actual

sediment yields from both the treated and the control plots are

small and of little consequence in the context of post-fire hillslope

stabilization.

In the 1990s, contour-felled log erosion barriers(LEBs)

were applied on 69 percent of the wildfires that included

post-fire hillslope stabilization treatments. Land managers generally regarded these LEB treatments as effective

and useful (Robichaud and others 2000). Throughout the

2000s,BAERtreatment area and expendituresincreased;

yet, the use of LEBs decreased rapidly in the first two to

three years ofthe decade. LEBsrarely have been installed

since 2002. The transition away from LEBs for post-fire

hillslopetreatmentisdirectlyrelated to the dissemination

of quantitative research resultsthat verified theirlimited

effectiveness (Robichaud 2005; Robichaud and others

2000, 2006, 2008a, b; Wagenbrenner and others 2006).

Post-Fire Hydrology 

and Erosion ____________________

Forested watersheds with good hydrologic conditions

(precipitationinfiltratesintosoilandstreamflowresponse

to precipitation is relatively slow) and adequate rainfall

generally sustain stream base flow conditionsthroughout

the year and produce little sediment (DeBano and others

1998). Under these conditions, infiltration of snowmelt

and rainfall is high (≤2 percent of the rainfall becomes

overland flow) and associated erosion is low (Bailey and

Copeland 1961). Fire impacts hydrological conditions by

destroying accumulated forest floor material and vegetation that provide protection to the mineral soil and hold

sediment on hillslopes. Fire often alters infiltration by

exposingsoilstoraindropimpactandcreatingorenhancing

water-repellent soil conditions (DeBano and others 1998,

2005; Doerr and others 2006). High soil temperatures can

increase surface soil erodibility—an indication of soil’s

susceptibilitytoraindropimpact,runoff,andothererosive

processes (Moody and Martin 2009a; Scott and others

2009). With the input of energy, available sediment can

be eroded from hillslopes and channels, transported, and

depositeddownstream.Rainfall,runoff,wind,andgravity

are thedrivers(energysources)ofthese erosionprocesses;

like the forestsoil, these drivers are affected by the loss of

vegetation and forest floor material. Exposed hillslopes

have increased raindrop impact, increased runoff with

more power due to longer uninterrupted flow paths and

lesssurface roughness, and increased wind speeds.These

changes increase the amount of energy available for erosion and sediment transport (Moody and Martin 2009a).

Fire effects on hydrology can be briefly mitigated by

the presence of ash. Forest fires may leave a dry, highly

porous ash layer covering the burned mineral soil (Cerdà

andRobichaud2009).Theashlayerabsorbsrainfall,which

increasesthetimetostartofrunoffandresultsinlessrunoff
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 3

compared to areas with little or no ash cover (Cerdà and

Doerr 2008; Onda and others 2008; Woods and Balfour

2008). The effects of the ash on post-fire infiltration and

runoff are generally short-lived (weeks to months) as ash

is easily transported and is moved to valley bottoms with

the first wind and rain events. Consequently, ash effects

have little impact on the longer-term post-fire watershed

responses that are of primary concern for post-fire treatment (Cerdà and Robichaud 2009).

When high severity fire results in poor hydrologic

conditions(most precipitation does notinfiltrate into the

soil and streamflow response to precipitation is rapid),

runoff and peak flows can increase by several orders

What to Expect—Predicting 

Post-Fire Response

Contributed by 

Nick Gerhardt, Forest Hydrologist (retired)

A year after the 2005 Blackerby Fire in north-central Idaho, a rain event (1.5 inch [38 mm] of rain in 54 min) triggered a

large hydrological response on a steep area burned at high severity. The runoff concentrated in the upper and mid reaches of

the channels in predictably high volumes, and sediment and debris (rock and some woody materials) were quickly entrained in

the flow. As the debris torrent entered the lower reaches, nearly all of the larger material (debris) was deposited, and the high

density (sediment-laden)flood flow continued down the channel.The addition ofsediment and debristo the concentrated runoff

flow increased the flow volume multi-fold. Using measured channel cross sections of the debris torrent and using models to

predict the runoff/flow volume, the proportion of water to sediment and debris was estimated (SB1-fig. 1).

Upslope from the culvert locations, cross-sectional areas were almost five times greater for the debris torrent (60.2 ft2

[5.60 m

2

]) when compared to the predicted waterflow cross-sections(12.4 ft2 [1.15 m

2

]); volume estimatesforthe debristorrent

(620 ft3s

–1 [18 m3

s

–1]) were nearly an order of magnitude greater than the flow volume estimated for water alone (SB1-fig. 2).

Protection of values-at-risk such as culverts, bridges, and stream-adjacent infrastructure is dependent on an adequate treatment

response, and in turn, treatment decisions are dependent on accurate predictions of potential post-fire response.

SB1-figure 2. Channel cross-section diagram showing the base channel 

structure, estimated cross-sectional area of water flow in the channel 

(based on hydrological modeling), and measured cross-sectional area of 

the debris torrent (water flow plus debris).

SB1-figure 1. Cross-section measurements were used to 

model the storm flow and estimate the parameters of the 

post-fire debris flow in this channel. 

of magnitude and can cause some of the most extreme

impacts faced by land managers (DeBano and others

1998; Neary and others 2005a). Post-fire increases in

flooding, channel incision, and debris flows are well

documented (for example, Curran and others 2006;

DeBano and others 1998; Lane and others 2006; Moody

and Martin 2009a,b; Neary and others 2005a). In general, the more intense the watershed response the less

effective post-fire treatmentswill be inmitigating those

responses (fig. 2) (Robichaud and others 2008b). Thus,

the factors discussed below impact both the potential

post-fire watershed responses and the effectiveness of

post-fire hillslope treatments.
4 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Figure 3. Post-fire year one event erosion rates (plotted 

on a logarithm scale) versus maximum 10-min rainfall 

intensity (I10) as measured on hillslope study plots in 

the Bitterroot National Forest, Montana (after Spigel 

and Robichaud 2007).

Figure 2. The three-dimensional chart on the left is a conceptual diagram (after Neary and others 2005b) that illustrates the 

relationships between burn severity (low to high), hydrological event (small to large), and watershed response (minor to major). 

The chart on the right uses the same vertical axis (watershed response) and adds a fourth dimension—treatment effectiveness 

(low to high)—that is represented by a cross-hatched area. Treatment effectiveness varies by treatment type but generally 

decreases as watershed response increases.

Factors That Impact Post-Fire Watershed 

Response and Treatment Effectiveness

The specific environmental characteristics that impact

post-fire treatment effectiveness have been divided into

two groups—factors that are not fire dependent (such as

topography and rainfall characteristics) and factors that

are directly related to the fire (such as soil burn severity

and the time since the fire). The cumulative effect ofthese

factors determinesthe severity of the watershed response

and, as a consequence, impacts post-fire treatment effectiveness (Reid 2010).

Factors Unrelated to Fire:

 • Rainfall characteristics, especially rainfall intensity—Intense, short-duration storms characterized

by high rainfall intensity and low rainfall amounts

havebeenassociatedwithhighstreampeakflowsand

significant erosion events after fires(fig. 3) (DeBano

and others 1998; Moody and Martin 2001; Neary

and others 2005b; Robichaud 2005; Robichaud and

others 2008a). In a recent publication, Moody and

Martin (2009b) synthesized post-fire sedimentation

rates for the western United States. Given the connection among rainfall amount, rainfall intensity,

and sediment yields, Moody and Martin derived and

mapped “rainfall regimes” in the western United

States(fig. 4). The rainfall regimes were determined

by a combination of rainfall types (based on Kincer

1919) and adjusted by the degree assigned to the

two-year 30-minute (min) rainfall intensity ( 2y r

30 I )

by the authors (table 1). Since the potential rainfall

amounts, intensities, and seasonal patterns directly

impact post-fire hillslope treatment effectiveness, it

is essential to consider the potential rainfall regime

of the burned area when selecting treatments.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 5

Figure 4. Rainfall regimes in the western United States as delineated by Moody and Martin (2009b; used with 

permission) (see table 1).
6 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

• Topography—The erosion rate generally increases

as slope and hillslope length (flow path) increase.

In addition, the drainage pattern (as determined by

geologic terrain) can concentrate or dissipate erosive

energy (Moody and Martin 2009a; Scott and others

2009). Longer flow paths and convergent hillslopes

(swales) allow overland flow to concentrate into rill

flow, which has higher erosive power and causes the

majority of surface erosion (Libohova 2004).

• Land use and management—The magnitude of a

watershed response to a hydrological event is dependent not only on naturalfactors(for example, rainfall

and topography) but on anthropogenic activitiessuch

as road building, fuel reduction, and timber harvest.

The cumulative effect of these activities and land

use can increase the severity of runoff, flooding, and

erosion following precipitation (Reid 2010).

Fire-Dependent Factors:

• Burn severity—(also referred to as “fire severity”) is a qualitative measure of the effects of fire

on ecosystem properties and is usually evaluated by

the degree of soil heating and/or vegetation mortality (Agee 2007). Several factorsthat impact post-fire

flooding and erosion response are included in the

assessment of burn severity, and higher burn severity

is associated with larger and more rapid watershed

responsestorainfall(DeBanoandothers1998;Moody

and others 2008).Forest ecologists define burn severity by the degree of overstory plant mortality, where

overstory mortality below approximately 30 percent

is considered low severity, 30 to 70 percent is consideredmoderate severity, and greaterthan 70 percent is

considered high severity (Agee 2007). Burned areas

where vegetation patches burned at high severity are

interspersed with patches burned at low severitymay

berated“moderateburnseverity”or“mixedseverity”

(Parsons and others 2010). Overstory plant mortality

influencespost-firefloodinganderosionbyimpacting

the raindrop energy hitting the soilsurface, hillslope

sedimentstorage, overland flow routing, drag forces

on surface wind, etc. However, the changes in soil

properties due to soil heating and loss of protective

ground cover (both included in “burn severity”)

are often more directly implicated in the increased

watershed responses and are categorized separately

as “soil burn severity” (Robichaud 2007).

• Soil burn severity—The fire effects of soil heating

and the consumption of organic material on the soil

surfaceandnear-surfaceleadtochangesinsoilpropertiesthatgenerallyreduce soilinfiltrationandincrease

soil erodibility (Benavides-Solorio and MacDonald

2001; Doerr and others 2006). (Other fire effects on

soil, such as changes in nutrient composition and

microbe communities, have little impact on postfire emergency stabilization treatment effectiveness

and are not discussed here.) The degree of soil burn

severity is dependent on the peak temperatures and

the duration of those temperatures within the soil.

Observablepost-firegroundparameters(forexample,

amount and condition of ground cover, ash color

and depth, soil structure, presence of fine roots, and

Table 1. Rainfall regimes, seasonal characteristics, intensity classification, and upper and lower 2-yr, 30-min rainfall 

intensity limits for each classification as delineated and described by Moody and Martin (2009b) for the 

western United States (see fig. 4).

Rainfall regime Seasonal characteristics

Rainfall intensity 

classification

2-yr, 30-min rainfall 

intensity (I 30

2yr ) 

(inch h–1 [mm h–1])

Lower Upper

ARIZONA Winter and summer wet

Spring dry

Fall moist

EXTREME

HIGH

MEDIUM

>2.0 [52]

>1.4 [36]

>0.8 [20]

3.9 [100]

2.0 [52]

1.4 [36]

PACIFIC Winter maximum

Summer minimum

HIGH

MEDIUM

LOW

>1.4 [36]

>0.8 [20]

>0.6 [15]

2.0 [52]

1.4 [36]

0.8 [20]

SUB-PACIFIC Winter wet

Spring moist

Summer and fall dry

LOW >0.4 [10] 0.8 [20]

PLAINS Winter maximum

Summer minimum

EXTREME

HIGH

MEDIUM

>2.0 [52]

>1.4 [36]

>0.7 [19]

3.9 [100]

2.0 [52]

1.4 [36]
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 7

soil water repellency) are often used to classify soil

burn severity (Parsons and others 2010; Robichaud

2007). Although increased erosion is likely on steep

slopes with moderate and high soil burn severity, the

greatest erosion occurs in areas of continuous (not

patchy) high soil burn severity (Moody and Martin

2009a;Robichaud2005;Robichaudandothers2006).

BAER teams, when evaluating the need for post-fire

stabilization treatments, are particularly interested in

the soil burn severity. The process used to produce

most post-fire burn severity maps from pre- and

post-fire satellite imagery can detectthe fire-induced

changesin vegetationmore definitively than changes

in the soil (Clark and Bobbe 2004). Since the need

for hillslope stabilization treatments is more closely

related to soil burn severity than to canopy mortality, post-fire assessment teams often need to correct

and verify the soil burn severity map (Parsons and

others 2010; Robichaud 2007). Factors that are most

often associated with post-fire treatment effectivenessstudies,such as percent ground cover,soil water

repellency, and soil erodibility, are dependent on soil

burn severity and are discussed below.

• Amount of bare soil—The amount of bare soil is an

important factor used to map burn severity (Key and

Benson 2006) and has been positively related to postfireerosionrates(Benavides-SolorioandMacDonald

2005; Curran and others 2006). In addition, there is

evidencethatpost-fireerosionisreducedwhennatural

mulch,suchasconiferneedlecast,providesprotective

post-firegroundcover(PannkukandRobichaud2003)

or when hillslope treatments, such as straw mulch,

provide immediate ground cover, thereby reducing

raindrop impact and shortening overland flow paths

(Wagenbrenner and others 2006).

• Soil water repellency—Fire-inducedsoilwaterrepellency has been directly linked to soil burn severity

(DeBano2000;Doerrandothers2006;Robichaudand

Hungerford 2000) and to reduced infiltration (Cerdà

and Robichaud 2009; Robichaud 2000). Although

the presence of fire-induced soil water repellency is

generally confined to the top few inches of the soil,

thepresenceanddegreevarywidelyacrosstheburned

landscape. In addition, the effects ofsoil water repellency can vary overtime, depending on soilmoisture,

withwaterrepellency beingmost pronounced during

dry conditions and reduced or absent following prolonged wet conditions (Doerr and others 2009). The

amountofwettingneededtoreduce or eliminate soil

water repellency varies with burn severity as well

as with soil type and degree of water repellency that

exists priorto wetting (Doerr and others 2009). Since

soil water repellency can be assessed more easily

than infiltration rates, post-fire soil water repellency

is often used to estimate the potential reduction in

infiltration rates.

• Soil erodibility—The ability ofsoilsto resist erosion

is based on many factors but predominantly on soil

texture,structure, and organic matter content (Hillel

1998). Soil texture refers to the relative proportions

of the inorganic soil particles by size (sand, silt, and

clay) and is usually unaffected by fire (DeBano and

others 2005). Based on differences in particle mass,

sand, sandy loam, and loam textured soils tend to be

less erodible than silt, very fine sand, and certain clay

textured soils. Soil structure is the arrangement of

primarysoilparticlesintoaggregates.Intheuppersoil

(at the duff-upper A-horizon interface),soilstructure

is highly dependent on the organic material (humus)

to “glue” soil particles together to form aggregates.

Thus, when the organic material in the upper soil is

consumed by fire, the soil can become disaggregated and, as a result, more erodible. In addition,

the collapse in soil structure decreases both total

porosity and pore size, which reduces infiltration

rates (DeBano and others 2005). Generally, soils

with greater infiltration rates, higher levels of

organic matter, and improved soil structure are

less erodible.

• Time since the fire—Natural recovery of native

vegetation reduces erosion over time. The greatest

erosion usually is measured during the first post-fire

year, and the second post-fire year and subsequent

years can be an order ofmagnitude lower(Robichaud

andBrown1999;Piersonandothers2001;Robichaud

and others 2008a). However, recovery rates vary by

climate and vegetation type. For example, post-fire

recovery in the Colorado Front Range is longer than

those reported above; the typical intense summer

convection storms can produce large sediment yields

for several years after a fire due to the highly erodible granitic soils, sparse vegetative cover, and steep

topography (Pietraszek 2006).

The factors discussed above are interrelated, and

changes in one factor are often reflected in changes of

others. For example, immediately following a wildfire,

areas burned at high severity will have little ground cover

(other than the ash layer), and the amount of exposed bare

soil will be high. As time since the fire increases, the

ground cover will increase and the amount of bare soil

will decrease; thus, time since the fire isindirectly related

to amount of bare soil exposed.
8 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

In a study of post-wildfire sediment yieldsin thewestern UnitedStates,Moody andMartin (2009b) determined

that soil availability is a dominant factor in predicting

post-fire sediment yields. Soil availability is dependent

on soil erodibility, ground cover, and the amount ofstored

sedimentonhillslopes andinchannels.Wildfiresincrease

soil erodibility and remove the vegetation and forest

floor material that hold soil in place and protect the soil

from forces of raindrop impact and overland flow. Thus,

wildfires make more soil available for detachment and

transport. Post-fire sediment yieldsreflect the amount of

protective ground coverlost, the magnitude ofthe erosion

drivers(rain, wind, and overland flow), the change in soil

physical propertiesrelated to erodibility (for example,loss

of organic material and disaggregation of soil particles),

and the amount of accumulated sediment in hillslope and

channel storage areas.

Post-Fire Erosion by Wind and Gravity

Wind-driven erosion is generally an issue in arid climates and in areas with prevailing drought conditions.

Increased wind erosion following wildfires in grasslands

and rangelands is well documented (see introduction in

Sankey and others 2009). Although less pervasive than in

arid landscapes, the occurrence and rate of wind erosion

cantemporarilyincreaseafterwildfiresinhumid,forested

areas as well (Scott and others 2009; Whicker and others 2006). Ravi and others (2006, 2009) have shown the

presence of fire-induced soil water repellency increases

wind erosion rates. Although some post-fire treatments,

such as wood mulches and hydromulches, are known

to resist displacement by wind, little attention has been

given to the use of post-fire treatments to mitigate wind

erosion. Post-fire wind erosion is likely to become more

of a concern, particularly in the southwestern and Great

Basin areas of the United States where climate models

predict continued drought and increased wildfire potential (Brown and others 2004; Flannigan and others 2000;

Westerling and others 2006).

Dryravel,or gravity-drivenerosion, generallyoccursin

steeplandscapeswhere surface soils are coarseorgravelly

and soil particles are pulled downhill by gravity (Scott

and others 2009). In the United States, dry ravel is commonly associated with chaparral landscapes in southern

California where most of the known wildfire effects on

dry ravel have been studied (for example, Krammes 1960;

Wells andothers1979).Destabilizedhillslopes are created

whenwildfires consume plantroots and ground coverthat

hold soil on hillslopes and can result in large increases

in dry ravel the first post-fire year. The material that is

transported as dry ravel generally is deposited in channels

where it becomes a sediment source for water-driven

erosion in subsequent wet season rains (Scott and others

2009). Many post-fire hillslope stabilization treatments

applied in southern California are intended to mitigate

dry ravel and, thereby, decrease the sediment availability

for debris flows during the following winter wet seasons

(Wohlgemuth and others 2009).

Comparing Results and Scale of 

Measurements

In recent years, direct measurements of watershed

processes (for example, runoff, peak flows, and sediment yields) have been made to assess post-fire treatment

effectiveness in many areas of the western United States.

It can be challenging to compare the results of different

fieldstudiesgiventhehighvariabilityinrainfall,soiltype,

topography, and other relevant variables. Site variability

is often problematic within a single field study, and comparisons between studies compound that variability. In

addition,thegeneralpracticeofnormalizing,orconverting

erosion rates and sediment yields to common units (for

example,tonsper acre [tonac

–1]ormegagramsperhectare

[Mg ha–1]), can be misleading as erosional processes do

not scale-up in a simple way.

Erosion rates can be expressed assedimentflux rates—

the mass of sediment transported across a unit hillslope

contour (feet [meter]) per unit time (day) or per rain event

(Moody and Martin 2009b). However, most post-fire

treatment effectiveness studies have measured runoff

and/or sediment yields at the base or outlet of a study

area. The spatial extent of these study areas can range

over several orders of magnitude. For example, we have

used hillslope plots (200 to 350 ft2 [20 to 30 m

2

]) (fig. 5),

swales (0.25 to 1.25 ac [0.1 to 0.5 ha]) (fig. 6), and small

catchments (2.5 to 25 ac [1 to 10 ha]) (fig. 7) for post-fire

treatment effectiveness studies (Robichaud 2005). Field

measurements are generally normalized (converted) to

mass of eroded sediment (tons [megagrams]) or depth of

runoff(inch [millimeter]) per unit area (acre [hectare]) per

unit time (year) or per rain event or rain amount (inch [millimeter]). Extrapolating runoff and sediment yields from

the smaller scale measurement units (lb ft–2 [ kg m

–2]) to

larger scale normalized units (ton ac

–1 [Mg 

ha–1]) makes it

easier to compare results from different studies that were

done at various locations and scales of measurement. However, the various types of water erosion (interrill or sheet

erosion, rill erosion, and channel and gully erosion) functiondifferently acrossspatialscales. Erosion at the plotscale

usually is limited to interrill and rill components, while

erosionmeasuredatthescaleofswalesandsmallcatchments

includesthose two processes aswell as channelized flow.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 9

Figure 7. Cleaned-out 

sediment basin at the outlet 

of a catchment study site 

on the 2002 Hayman Fire 

in Colorado. 

Figure 5. Hillslope plot with a contour-felled 

log and a silt fence at the base for sediment 

collection on the 2000 Valley Complex Fires 

in Montana. 

Figure 6. Hillslope plot that 

incorporates a swale with a 

double silt fence at the base 

for sediment collection on 

the 2000 Bobcat Fire in 

Colorado.
10 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Figure 8. A contour-felled log erosion barrier with soil end 

berms to increase sediment storage capacity. 

Channelized flow—including deposition within the

study area rather than at the outlet where the sediment

yield is measured—becomes a more dominant process

as the contributing area increases (Moody and Martin

2009b; Pietraszek 2006).

Ingeneral,runoffdecreasesashillslopelengthincreases,

which islargely attributed to spatial variability in infiltration (for example, Gomi and others 2008; Joel and others

2002). However, after large wildfires, this trend may not

always hold as lower infiltration rates (due to fire effects)

may be fairly consistent over large areas burned at high

severity.Similarly,sedimentyieldstendtodecreaseasarea

of measurement increases. The scale dependency ofsediment yield has been attributed to the deposition of eroded

sediment in hillslope sediment sinks before reaching the

base of the research plot where it would be measured (for

example,Wilcoxandothers1997).However,this explanation is likely too simplistic; other explanations have been

suggested by researchers (for example, Parsons and others 2004, 2006) but have not been universally accepted.

Nonetheless, it is clear that erosion rates are influenced

by the scale at which they are measured, and erosion rates

measured at one scale should not simply be extrapolated

to larger scales (Parsons and others 2006).

Little work has been done to examine the scaledependency of post-fire runoff, peak flow, and sediment

yield measurements. However, some scaling effects on

sediment yields were documented in a two-month study

thatexaminedscaleeffectsonpost-firetreatmenteffectiveness (reduction in sediment yields due to treatment with

LEBs) on an area burned at high severity (Gartner 2003).

A set of paired catchments were established to measure

treatment effectiveness at four spatial scales—plot (10

to 50 ft2 [1 to 5 m

2

]), hillslope (~4,300 ft2 [~400 m

2

]),

sub-catchment (2.5 to 12 ac [1 to 5 ha]), and catchment

(~40 ac [~16 ha]). The study areas were nested such that

the largest areas(catchments) contained the smaller areas

(sub-catchments, hillslopes, and plots). At the smallest

scale (plots), where interrill processes dominated, no

effect from the LEBs could be detected. At the hillslope

and sub-catchment scale, LEBs generally were effective

forthe low intensity rain events observed during the study

period. At the catchment scale, no treatment effect was

observed, but the authorsuggested that these results were

likely related to inexact pairing rather than scale or LEB

treatment effects (Gartner 2003).

Erosion Barrier Treatments _______

Erosion barriers, made from natural and engineered

materials, have been used for decades to mitigate postwildfire runoff and erosion (Robichaud and others 2000).

These structures are designed to slow runoff, cause

localized ponding, and store eroded sediment. When the

erosion barriers function as designed, they can decrease

the erosive energy of runoff, increase infiltration, and

reduce downstream sedimentation (Robichaud 2005).

Common post-wildfire hillslope erosion barriers include

contour-felledlogs(LEBs)(fig.8),strawwattles(10inches

[0.25 m] diameter, 13 to 20 ft [4 to 6 m] long nylon mesh

tubesfilled with straw) (fig. 9), contour trenches(hand or

machine dug trenches), and straw bales (blocks of straw

bound with twine) (fig. 10). To eliminate long uninterrupted flow paths, erosion barriers are generally installed

in staggered tiers with the center of each erosion barrier

directly downslope from the gap between the two erosion

barriers above it.

Prior to 2000, LEBs were widely used for post-fire

hillslope stabilization, as most forest fires leave dead

trees that can be felled and limbed for this use. Managers

assumed that hillslope installations of LEBs increased

surface roughness and slowed runoff, allowing runoff to

pond in the storage areas behind theLEBs.Thisincreased

infiltration, reduced the amount and flow velocity of the

runoff, and resulted in reduced erosion (Robichaud and

others 2000). Although there was little quantitative evidence for these assumptions at the time, Wagenbrenner
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 11

Figure 9. A recently installed straw wattle erosion 

barrier. 

Figure 10. A set of straw bale erosion barriers installed in a burned swale 

on the 2002 Hayman Fire in Colorado. 

and others(2006) did measure greater infiltration ratesin

the disturbed areas immediately upslope of an LEB than

in surrounding, less-disturbed burned areas.

Strawwattles have been used as a reasonable alternative

to LEBsin burned areas where logs were scarce or poorly

shaped (for example, in the chaparral areas of southern

California, asseen in fig. 9). Straw wattles are permeable

barriers that detain surface runoff long enough to reduce

flowvelocity and provide forsome sedimentstorage.Like

LEBs,straw wattles can be laid out in staggered tiers on a

hillslope (fig. 11) but are flexible and conform to the soil

surface so that gaps rarely occur. The disadvantages of

straw wattles include the expense of manufacturing and

shipping,andthepotentialforthestrawfilltobeasourceof

non-native seed and an attractive food source for animals.

When Robichaud and others (2000) surveyed land

managers with post-fire treatment experience, 65 percent

reported that LEB installations were “good” or “excellent” at reducing post-fire erosion. Most of these positive

responses were based on observations ofsedimentstored

behind the LEBs on treated hillslopes (McCammon and

Hughes 1980; Miles and others 1989). Although the

amount of sediment stored by LEBs on a hillslope could

be used as a measure of treatment effectiveness, a more

relevant measure is a quantitative comparison of post-fire

runoff, peak flow, and/or sediment yield from equivalent

treated and untreated areas, as in the studies presented in

Appendix B.
12 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Erosion Barrier Performance 

Characteristics

To differentiate and clarify the two types of sediment

measurements—sedimentheldbytheerosionbarrieritself

and sediment yields at the base of the hillslope—we use

the concept of “erosion barrier performance” (Robichaud

and others 2008a). Erosion barrier performance can be

quantified by comparing the amount of sediment held by

the erosion barrier(s) to the total amount of sediment that

was mobilized. Thus, erosion barrier treatment performance, EBPERF (%), would be

EB CS

EB

PERF M M

M

EB 100

where MEB isthe dry weight (lbs[kg]) ofsedimentstored

by the erosion barrier(s), and MCS is the dry weight (lbs

[kg]) of collected sediment or sediment flux below the

erosion barrier treatment (Robichaud and others 2008a).

Hillslope plots with one of three post-fire erosion barrier

treatments (LEB, straw wattle, or hand-dug trench) or

no treatment were installed with sediment fences at the

base to determine erosion barrier performance as well as

the treatment effectiveness (see Appendix B-Study III).

Robichaud and others (2008a) measured EBPERF over

three sediment-producing rain events during the first

post-fire year. After the first sediment-producing storm,

mean EBPERF was 87 percent for contour-felled logs,

Figure 11. Straw wattles installed in a staggered layout on a burned 

hillslope. 

83 percent for straw wattles, and 72 percent for contour

trenches. However, the barriers captured little additional

sediment after that first storm, and their performance

declined as additional rain events occurred (fig. 12). In

general, EBPERF decreases over time as more hillslope

erosion takes place and the proportion of MCS compared

to MEB increases (Robichaud and others 2008a).

Another erosion barrier performance measurement

compares the actual volume of sediment stored behind

an erosion barrier to the total sediment storage capacity

of that erosion barrier (fig. 13). The sediment-trapping

ability of any erosion barrier installation is dependent

on the site characteristics (for example, slope and soil

type), the individual erosion barrier features (such as

diameter, length, accuracy of contour placement, and

seal between the barrier and the ground), and the density

and pattern of erosion barriers over the landscape. When

LEB installations have been examined to determine how

much sediment-holding capacity is used, the mean sediment storage performance of the barriers is around 60 to

70 percent (Robichaud and others 2008a, b). Robichaud

and others (2008a) qualitatively evaluated erosion barrier performance over three natural rain events. In 13 of 29

observations, runoff and sediment flowed over the top of

thebarrier,yetonly3ofthe13barrierswerefilledtocapacity

and 5 barriers were at or below 50 percent full. Overland

flowpatternsandLEBshapesoftenresultinunevenfilling

of the sediment storage area above the LEB that leaves

a portion of sediment storage capacity unused (fig. 14).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 13

Figure 12. Mean erosion barrier performance (EBPERF [%]) for three successive natural 

rainfall events in post-fire year one as measured on hillslope study plots established on 

the 2000 Valley Complex Fires in western Montana. The date, total rainfall amount, and 

maximum 10-min rainfall intensity are listed for each event (Robichaud and others 2008a). 

Figure 13. Schematic of measurements made on a contourfelled log to calculate the sediment storage capacity of the 

erosion barrier (from Robichaud and others 2008a). 

Figure 14. A partially filled LEB with unused 

sediment storage capacity indicated. 
14 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Consequently, even when an erosion barrier installation

provides adequate capacity to hold predicted sediment

yields, the actual volume held is usually less than full

capacity, and observed runoff that goes over the tops and

around the ends of the LEBs carries entrained sediment

(Robichaud and others 2008a).

Erosion barrier treatment effectiveness (the reduction

in sediment yield at the base of the hillslope) is impacted

by the erosion barrier performance. Erosion barrier performance is highest when barriers are new and have little

or no sediment stored behind them. Not surprisingly,

post-fire LEB hillslope treatments are most effective for

the first few sediment-producing events, with effectiveness declining over time. As a corollary, erosion barrier

treatment effectiveness can be improved by increasing the

performance of the installation. EBPERF can be improved

by adding soil berms to the ends of LEBs (or turning the

endsofthestrawwattleupslope)tocreatea“smile-shaped”

barrier, which increases the sediment storage capacity of

erosion barriers by 10 percent or more (Robichaud and

others 2008a). Increasing the erosion barrier density on

the hillslope also increases the sediment storage capacity

ofthe installation.Sedimentstorage capacity is dependent

on careful installation to ensure that erosion barriers are

accuratelyplacedalongthehillslopecontoursandsecurely

anchored, with gaps between the erosion barrier and the

ground completely sealed. In post-fire field installations,

with hundreds of barriers installed by crews of varying

skill and supervision, it is likely that some of the barriers

will be poorly installed. In a study of LEBs installed by

field crews in Colorado, an average of 32 percent of the

barriers from seven sites and as many as 70 percent of

the barriersfrom a single site were off-contour and/or had

incomplete contact with the ground (Wagenbrenner and

others 2006). Improving the quality of an erosion barrier

installation may improve performance, but it will also

increase the time and labor costs for installation.

Erosion Barrier Treatment Effectiveness

Recent research efforts in which hillslope runoff and/

or sediment have been measured have provided insight

as to effectiveness and limitations of erosion barriers

(see Appendix B). The consensus among these studies is

that erosion barriers, and LEBs in particular, may reduce

runoff and sediment yields for low intensity rain events,

but they are unlikely to have a significant effect for high

intensity rain events.

Robichaud and others (2008b) completed a multi-year,

multi-site study of the effectiveness of LEBs for reducing post-fire runoff, peak flows, and sediment yields(see

Appendix B-Study IV). The study involved six paired

watershedsitesinthewesternUnitedStatesthatwereestablished immediately afterwildfires on areas burned at high

severity. At each site, two small, comparable watersheds

had sheet metal head walls with overflow weirs installed

at the outlet. One watershed was treated with LEBs and

one was left untreated as the control. Event runoff and

sediment yields were measured at the base outlet and

correlated to rainfall characteristics overseveral post-fire

years(Robichaudandothers2008b).Thesemeasurements

are listed by site in tables AB-4 to AB-9 in Appendix B.

High intensity rainfall (maximum rainfall intensity for a

10-minute period [I10]≥two-yearreturn period) produced

most of the measured runoff and sediment yields, except

in the southern California site where long-duration rain

events produced most of the runoff and erosion (fig. 15).

Runoff,peakflows,andsedimentyieldsweresignificantly

smaller in the treated watersheds for smaller rain events

(I10 < two-year return period). However, and perhaps more

importantly, no treatment effects were measured for rain

events with larger return periods—the events that produced most of the measured runoff and sediment yields

(Robichaud and others 2008b).

These results are similarto otherstudiesin which LEBs

were evaluated at smaller scales and/or shorter times.

Wagenbrenner and others (2006) found LEBs were ineffective in large storms but could be effective for small

events given sufficient sediment storage capacity (see

Appendix B-Study I). Gartner (2003) found that LEBs

generally were effective for low intensity rain events

observedduringthetwo-monthstudyperiod(seeAppendix

B-Study II). Robichaud and others (2008a) compared

three types of erosion barriers—LEBs, straw wattles,

and hand-dug contour trenches—using a relatively low

intensity (I10 < two-year return period)simulated rainfall

(1 inch h–1 [26 mm h–1]) with added overland flow (13 gal

min–1 [48 L min–1]). The LEBs and straw wattlesreduced

total runoff, and all three erosion barrier treatments

reduced peak flow rates; however, only the straw wattles

significantly reduced sediment yields compared to the

controls(table AB-3 in Appendix B) (Robichaud and others 2008a). In the subsequent three years,sediment yields

from natural rainfall were measured, and there were no

treatment effects associated with 10 sediment-producing

rain events. In addition, sediment yields increased with

increasing total rainfall and rainfall intensity. The erosion barrier treatment effectiveness measured during low

intensity simulated rainfall (even with added inflow) did

notapplyduringhigherintensitysummerstormstypicalof

westernMontana (seeAppendixB-Study III)(Robichaud

and others 2008a). Given that high intensity rain events

produce the largest post-fire event sediment yields, the
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 15

lackoftreatment effectivenessforthese stormsis a serious

consideration in treatment choice.

There is some evidence that the installation of erosion

barriers may cause enough soil disturbances to increase

sediment yields in the first few rain events following

installation (Robichaud and others 2008b). In one of six

sites,firstpost-fireyearsedimentyieldsintheLEB-treated

watershed were greater than in the control watershed, but

the treated watershed had lower sediment yields in postfire years two and three (see table AB-5 in Appendix B).

In another two of the six sites, sediment was measured

in the treated but not the control watersheds for the first

two sediment-producing rain events(see tables AB-4 and

AB-7 in Appendix B).

Post-fire rehabilitation treatment decisionsinvolve balancingtheneedtoreduce thepost-fire riskofdamagefrom

increased runoff and erosion with the predicted effectiveness, availability, and installation costs of the treatments

selected for use in the burned area. The labor-intensive

installation, which involves the skilled, and relatively

hazardous,felling ofstanding burnedtimber, andthe need

for quality control make most erosion barrier treatments

expensive given their limited reduction of erosion risk. In

areas where high intensity rainfall is common, treatment

decisions do not favor the use of erosion barriers for hillslope erosionmitigation.However, erosion barriers can be

combined with other treatments, such as mulches and/or

seeding, and may contribute to the overall effectiveness

of the treatment (Dean 2001; de Wolfe and others 2008).

Another consideration formost erosion barriertreatments

istheirlackoflongevity.Overtime,performancedecreases

due to loss ofsedimentstorage capacity and breakdown of

barrier installation (such asloss of ground-barriersealing

and movement ofthe barrier) and the erosion barrierslose

effectiveness. If burned hillslopes will be vulnerable to

erosion for more than one or two years, an erosion barrier

installationmay notretain enough capacity to be effective

for even small rain events.

Mulch Treatments _______________

Mulch is materialspread over the soilsurface to protect

it. In agricultural uses, mulches are applied to modulate

soil moisture and temperature, control weeds, reduce

soil sealing, and, in the case of organic mulches such as

compost, improve soil structure and nutrient content.

Mulch is increasingly applied as an emergency post-fire

treatment to reduce rain drop impact, overland flow, and

erosion (Bautista and others 2009).Becausemulching can

be effective ground coverimmediately after application,it

is an attractive choice for post-fire hillslope stabilization.

It is often used in conjunction with seeding to provide

ground cover in critical areas and to increase the success

of seeding by improving moisture retention. Due to the

cost and logistics of mulching, it is usually applied where

there are downstream values at high risk for damage such

as above municipal water intakes, heavily used roads,

Figure 15. Rainfall intensity versus sediment yield (logarithm scale) from 

a paired watershed study that involved six sites and data from up to six 

post-fire years in the western United States (Robichaud and others 2008b).
16 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

and stream reaches that are critical habitat for

protected species.

Mulchhasbeenshowntoincreasesoilinfiltration capacity, moisture content, and aggregate

size while decreasing surface compaction and

temperature (Bautista and others 1996, 2009).

Changesinmicroclimatic conditions andwater

availability in the surface soil can improve

natural vegetative recovery and benefit seeded

species, which in turn can positively impact

runoff and erosion (Bautista and others 1996;

Dean 2001; Wagenbrenner and others 2006).

The mulches used in post-fire treatments are

generallydividedintotwogroupsbasedonhow

they are applied. Wet mulches, usually referred

to as hydromulch, are prepared by mixing the

components with water to form a slurry that is

applied to the soil surface. Dry mulches, such

as agricultural straws and wood materials, are

applied without water.

Dry Mulches

Strawmulchwasfirst used for post-fire treatments in the 1980s (for example, Gross and

others 1989; Miles and others 1989), but it was

not widely used until 2000 when the number

of large, high soil burn severity fires began to

increase.Milesandothers(1989)gavemulching

a “high” efficacy rating, butthe installation rate

was“slow.”Duringthepastdecade,aerialapplication techniquesforstraw mulch have made it

possible to apply mulches more efficiently and

to treat inaccessible burned areas, making it a

viable treatment alternative for the large fires

that occur in the mountainous western United

States. Straw mulching has been the primary

hillslope treatmentfollowing some recent large

fires, including:

	 •	 the 2002 Rodeo-Chedeski Fire in Arizona

where more than 18,000 ac (7300 ha) were

treated with straw mulch (Richardson

2002);

	 •	 the 2002 Hayman Fire in Colorado where

7700 ac (3100 ha)were strawmulched (and

more than 3000 ac [1200 ha] were hydromulched)(Robichaudandothers2003);and

	 •	 the 2006Tripod Fire inWashington where

more than 14,000 ac (5700 ha)were treated

with straw mulch (USDA Forest Service

2006).

Mulch Impacts Soil Temperature

Contributed by Greg Kuyumjian

Forest Hydrologist

Okanogan-Wenatchee National Forest, WA

Post-fire mulch treatments can provide benefits beyond erosion reduction. Soil temperatures measured afterthe 2000Cerro Grande Fire in New

Mexico showed that the dry straw mulch treatment had shaded the soil

surface and reduced soil temperatures. Lower soil temperatures increase

available moisture, which can be an advantage forrevegetation afterforest

fires, especially in dry, arid environmentslike theSouthwest.Temperature

data were averaged for a four-day period (July 22 to 25) for each of the

first three post-fire years (table SB2-1). On the untreated site, the average

maximumdaily temperature ofthe soil(taken at 1 inch [2.5 cm] depth) was

alwaysgreaterthantheaveragemaximumdailytemperatureoftheambient

airfor each ofthe three years.On themulched site,itwasthe opposite—the

average maximum daily temperature of the soil was less than the average

maximum daily temperature of the air for each of the three years.

Table SB2-1. Maximum ambient air temperatures and maximum soil 

temperatures at 1 inch (2.5 mm) depth were measured on two 

sites—one with straw mulch treatment and one without mulch. 

Data for July 22 to 25 are shown for post-fire years one, two, and 

three (2001, 2002, and 2003). The average differences between 

maximum air temperature and maximum soil temperature by year 

are shown. 

 Day

No mulch

Pueblo Canyon

Mulch

Pajarito Canyon

Air temp. 

(°F) [°C]

Soil temp. 

(°F) [°C]

Air temp.

(°F) [°C]

Soil temp. 

(°F) [°C]

2001

July 22 77 [25] 77 [25] 79 [26] 70 [21]

July 23 82 [28] 86 [30] 83 [28] 75 [24]

July 24 81 [27] 86 [30] 80 [27] 75 [24]

July 25 77 [25] 83 [28] 87 [31] 72 [22]

Average 

difference 

soil temp. was 4 [2] degrees 

greater than the air temp.

soil temp.was 9 [5] 

degrees less than the 

air temp.

2002

July 22 73 [23] 83 [28] 74 [23] 73 [23]

July 23 70 [21] 74 [23] 71 [22] 69 [21]

July 24 79 [26] 84 [29] 81 [27] 73 [23]

July 25 84 [29] 78 [26] 84 [29] 72 [22]

Average 

difference 

soil temp. was 3 [2] degrees 

greater than the air temp.

soil temp. was 6 [3] 

degrees less than the 

air temp.

2003

July 22 87 [31] 90 [32] 89 [32] 78 [26]

July 23 86 [26] 84 [29] 88 [31] 73 [23]

July 24 89 [32] 91 [33] 90 [32] 79 [26]

July 25 87 [31] 93 [34] 88 [31] 78 [26]

Average 

difference 

soil temp. is 2 [0.5] 

degrees greater than 

the air temp.

soil temp. was 12 [6] 

degrees less than the 

air temp.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 17

There are on-going post-fire treatment effectiveness

studies within these burned areas. Although few studies

have been published, preliminary data indicate that dry

mulchingcanbe ahighlyeffectivepost-firehillslope treatment. Data showing successful erosion mitigation using

dry mulch have encouraged increased use of post-fire

mulching and the development of new mulch materials

and application techniques.

Mulch isfrequently applied to improve the germination

ofseededgrasses,andacombinationofmulchingandseeding has beenmore effective than seeding alone atmultiple

locations(BadiaandMarti2000;Bautistaandothers2005;

Dean 2001). The mulch cover enhancesseed germination

and growth by increasing soil moisture and protecting the

seeds from being washed downslope (fig. 16). However,

some studies have shown that combined mulching and

seeding does not increase vegetative cover over mulching

alone (for example, Kruse and others 2004; Rough 2007).

Agricultural straw mulches often contain non-native

seed species that can persist and compete with the

re-establishment of native vegetation (Beyers 2004;

Robichaud and others 2000). BAER teams and land managers prescribe certified “weed free” straw for post-fire

mulching, but it is not always available in the locations

and quantities needed. This problem occurred following

the 2002 Hayman Fire in Colorado when the straw that

wastrucked into the burned area for post-fire application,

despite being certified “weed free” in its state of origin,

contained seeds of cheat grass (Bromus tectorium), an

invasive grass in Colorado (Robichaud and others 2003).

This has likely contributed to the establishment of cheat

grassinportionsoftherecoveringlandscapeoftheHayman

Fire (P.R.Robichaud,field observations,July 2006).Rice

straw is less likely to bring in noxious weeds since rice is

grown in moist habitats, and successful weeds from rice

fields are unlikely to germinate or spread in dry forest

environments (Beyers 2004). However, when rice straw

was applied with and without barley seed on burned forest

land in northern California, the mulch-only quadrant had

significantly higher non-native species, and all mulched

quadrantshadsignificantlyreduceddensityandfrequency

of conifer seedlings (Kruse and others 2004).

Although wood mulching is less common than straw

mulching, wood chips, wood shreds, and wood strands

(thin wood strips manufactured from non-merchantable

timber or production waste, such as WoodStrawTM) are

increasingly being developed and used for post-fire treatment. As we look at post-fire stabilization effects over a

longertime frame, new approachesthatfit into ecological

restoration schemes are gaining interest. The use of wood

mulchesdevelopedfromlocal,site-specificforestmaterials

(wood chips or wood shreds manufactured on site from

burned trees, shredded debris from forest-clearing or

post-fire logging, etc.) for post-fire erosion control is an

emergency stabilization treatment that fits into a broader

ecological restoration context (Bautista and others 2009)

(fig. 17). Forestry equipment manufacturers are adapting

wood chippers and shreddersto handle burned timber and

aredevelopingapplicationtechnologiesfortheoutputfrom

these devices.Usingmaterialsfromthe local environment

reducesthe cost and time fortransportingmulchmaterials

to the treatment areas.

Hydromulches

Hydromulches are combinations of various short,

bonded, organic fibers (wood shreds, paper, cotton,

flax, etc.), tackifiers, suspension agents, seeds, etc., that

are mixed with water and applied to the soil surface.

Hydromulchisausefulrehabilitationtreatmentforerosion

control on road cut-and-fill slopes and areas of bare soil

at construction sites, and it is increasingly being used for

post-firehillslopestabilization(Napper2006).Thematrix

formed by the hydromulch holds moisture and seeds on

steep slopes, which fosters seeded plant germination

while holding the soil in place. Since hydromulch binds

to the soil surface, it is very wind-resistant; however, the

smooth, dense mat has little resistance against the shear

force of concentrated flow. Consequently, hydromulch

mitigates water erosion more effectively on short slope

lengths where concentrated flow and rill erosion are not

as likely as on longer slopes (Napper 2006).

Figure 16. Following the 2000 Cerro Grande Fire near Los 

Alamos, New Mexico, areas were treated with aerial seeding 

and mulching. After three growing seasons, the ground cover 

in the mulched and seeded area (background) is much greater 

than in the seeded only area (foreground). 
18 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

There are numerous tackifiers, bonded fiber, seeds,

etc., that can be included in hydromulch mixes.

Generally, the tackifier (“glue” that bonds the fiber to

the soil), mulch material, and seeds are selected separately and mixed with water just prior to application.

The selection of the tackifier is particularly important

as the environmental impacts, performance characteristics, availability, and cost vary widely. Selection is

complicatedbythe largenumberof choices anddifficulty

in knowing the chemical composition of the tackifier

when formulations are covered by proprietary rights

and are not disclosed. Both organic (polysaccharides

derived from plants such as guar, plantago, and corn)

and synthetic (polyacrylamide [PAM], polyacrylates,

and co-polymers of these two base chemicals) materials are sources for the long-chained molecules used in

tackifiers(Etra 2007).The specific types and proportion

of hydromulch components as well as the application

rates have varied in post-fire hillslope stabilization

projects; thus, hydromulch performance measured to

date may not be indicative of the potential performance

of new components, combinations, or application rates.

Performance Characteristics of Mulches

The amount of bare soil exposed, or, stated conversely,

the amount of ground cover is related to watershed

response and to the treatment effectiveness of post-fire

hillslope mulching treatments whose basic functional

feature is coverageofbare soil(Burroughs andKing 1989;

MacDonald and Robichaud 2007; Robichaud and others

2000;Wagenbrenner andothers2006).AccordingtoFoltz

and Copeland (2009: 785), “... the percentage of cover is

more important than the type of erosion control material

[applied]. Cost effectiveness, long-term durability, and

impacts on revegetation become controlling factors in

erosion control material selection.” Generally, post-fire

mulch treatments need to provide 60 to 80 percent ground

coverto reduce hillslope erosion (Napper 2006; Pannkuk

andRobichaud 2003).However,Foltz andWagenbrenner

(2010) reported that a 50 percent cover of wood shreds

significantly reduced sediment yields nearly as well as

70 percent cover. The percent ground cover of any mulch

installation is dependent on application rates and techniques. Aerial application of mulch is constantly being

Figure 17. Woody mulch made from forest debris. Photo by S. Bautista.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 19

refined to accommodate various types of mulch and

to improve the consistency of mulch thickness and bare

soil coverage across a burned landscape. In addition, the

lengthoftimethatmulchcaneffectivelymitigateerosionis

dependent on the length oftime the ground stays covered.

Thus, longevity of the mulch material and its propensity

to stay in place are also directly related to mulch treatment effectiveness. The length(s) of the mulch fibers and

its impact on post-fire revegetation are also important

performance characteristics.

Ground Cover Amounts and Application Techniques—

Straw mulch can be applied by hand, with blowers, or

fromaircraft.Groundapplicationispreferredforrelatively

smallareaswhere100percentofthegroundcanbecovered

by a thin, even mulch layer. However, hand application

requires large crews to get the mulch cover in place in a

timely manner (fig. 18). Trailer- or truck-mounted blowers, although faster than hand distribution, are limited to

areas above and below roads or other drivable areas such

as fire lines (fig. 19). Helicopters were first used to apply

Figure 18. Hand application of post-fire straw mulch treatment (photo 

from Napper 2006: 28) 

Figure 19. Post-fire straw mulch treatment being applied downslope from a road using a 

trailer-mounted blower pulled by a tractor on the 2007 Cascade Complex Fires in Idaho. 
20 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Figure 20. Aerial application of postfire straw mulch treatment using 

a cargo net suspended below a 

helicopter; the cargo net is released 

over the target area (photo from 

Napper 2006: 25). 

Figure 21. Wood shred coverage 

after aerial application on an 

experimental watershed site 

established on an area burned at 

high severity on the 2007 Cascade 

Complex Fires in Idaho. The PVC 

pipe frame (39 inches [1 m] on a 

side) is strung with twine to form 

100 intersection points and is used 

to sample ground cover. 

straw mulch in 2001, and this method has become more

common asit allowslarge areasto be treated quickly and

efficiently at a lower costthan hand application.The straw

bales break apart as they fall from a suspended cargo net

and spread further upon impact (fig. 20) (Bautista and

others 2009; Napper 2006). Underideal conditions, aerial

applicationcanprovideanevendistributionofstrawmulch

overthe ground; however, depending on wind conditions,

steepness of the hillslopes, number of standing trees,

experienceofthehelicopterpilot, andthemoisture content

of the mulch, application can be uneven and can require

ground-based workersto break up clumps and smooth out

the mulch (Santi and others 2006).

Likestrawmulch,wood-basedmulchescanbespreadby

hand, ground-based machinery, and aircraft. Wood chippers and shredders may be fitted with blowersthatspread

the mulch asit is produced. Aerial application techniques

are being developed to distribute chipped, shredded,

and manufactured wood mulch materials at a rate that

provides 50 to 60 percent ground cover. After the 2005

School Fire in southeastern Washington, manufactured

wood strands were applied by helicopters with suspended

cargo netsthat delivered themulch overthe treatment area

(heli-mulching), resulting in 54 percent average wood

strand cover. In 2007, following the Cascade Complex

Fires in Idaho, a study was initiated on a 5-ac (2-ha) area

burned at high severity that was heli-mulched with wood

shreds. The wood shreds spread into an even, but thin

mulch cover(37 percent)in the treated watershed (fig. 21),

leaving about 50 percent bare soil exposed compared to

the 77 percent bare soil exposed in the control watershed.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 21

Hydromulch components are transported as drymaterials and mixed with water in large truck-mounted tanks

to form a slurry that is sprayed or dropped on the soil

(fig. 22).Some hillslope applications have been completed

using truck-mounted sprayers; however, the effective

range of truck-mounted hydromulch sprayers is about

120 ft (40 m) on either side of roads. These ground-based

hydromulchtreatmentsaremostlyusedforsmallareasand

to stabilize and seed burned-over forest road cut-and-fill

slopes. Aerial application methods have made it possible

to apply hydromulch over large burned areas (fig. 23).

The hydromulch slurry is transferred from the mixing

tank into aircraft-mounted tanks at a staging area. While

flying over a target treatment area, the slurry tanks are

openedtoapplythemulch.Giventhelimitedcapacityofthe

tanks, many tripsto and fromthe staging area are needed,

which makes aerial hydromulching expensive even when

compared to other mulching treatments (Napper 2006).

In areas where the application rate is large enough, the

hydromulch slurry dries to form a continuous mat that

Figure 22. Trailer-mounted sprayer used to apply hydromulch from the road 

as a post-fire hillslope treatment on the 2002 Hayman Fire in Colorado.

Figure 23. Large-capacity helicopters fitted with slurry tanks are used to apply hydromulch 

as a post-fire hillslope treatment on the 2002 Hayman Fire in Colorado. 
22 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

covers and adheres to the soil (fig. 24). An application

rate of ~1 ton ac

–1 (~2 Mg ha–1) of dry mulch material

(prior to being mixed with water) is needed to obtain at

least 70 percent hydromulch ground cover (Bautista and

others2009).However,thecalculatedapplicationrateshave

not always attained the target cover amounts—especially

when aerial application is used. For example, after the

2003 Cedar Fire, the hillslope application of hydromulch

was targeted for 70 percent coverage but only 56 percent

coveragewasachieved(Hubbert,unpublishedpaper2005).

Residual canopy and standing trees on burned hillslopes

may interceptsome of hydromulch during the application

process, reducing the actual ground cover and potential

treatment effectiveness. For example, in one of the first

post-fireaerialapplicationsofhydromulch,1450ac(590ha)

weretreatedwithhydromulchafterthe2000CerroGrande

Fire in Los Alamos, New Mexico. It was estimated that

in burned areas that were heavily timbered, as much as

40 percent of the application was intercepted by standing

trees(G.Kuyumjian,personalcommunicationasreported

in Napper 2006: 15).

Mulch Impacts on Post-Fire Revegetation—

Optimizing the thickness of post-fire mulch is a balance

between soil protection and the potential suppression

of revegetation and establishment of seeded species

(Bautista and others 2009). Thick layers of mulch can

prevent sunlight from reaching the soil surface and can

physically obstruct seedling emergence (Beyers 2004).

Figure 24. A small piece of the aerially-applied hydromulch mat (exposed 

surface is brown) has been lifted off the burned soil (black) and flipped over 

to expose the underside of the mat (black and green). The pocket-sized 

field notebook is included for scale.

Robichaudandothers(2000)reportedthatshrubseedlings

were more abundant at the edge of mulch piles where the

strawmulchmaterialwaslessthan1inch(2.5cm)deep.The

suppression of post-fire vegetation isseen as an advantage

whenmulchesreduce encroachment of undesirable plants

into the burned area. However, vegetation suppression is

a significant disadvantage when mulches inhibit natural

recovery. Beyers and others (2006) reported that none

of the studied post-fire treatment mulches (wood chips,

hydromulch, and rice straw mulch) increased vegetation

cover;andwoodchipmulchinginhibitedvegetationrecovery more than other treatments while providing the most

total ground cover and greatest reduction in erosion for

several years. It is widely assumed that mulch thickness

impacts post-fire revegetation, but the optimumthickness

for post-fire mulch treatments has not been established.

Debatsandothers(unpublishedreport2008)foundthat100

percenthydromulchcoverage reducedinitialplantdensity

on post-fire hillslopes in southern California chaparral.

They compared their findings with Hubbert and others

(unpublished report 2005) who reported no apparent

vegetation suppression due to the 51 percent coverage of

hydromulch on similarly burned landscapesfollowing the

2003 Cedar Fire in southern California.

Longevity or Durability—The amount of time mulch

remainsinplaceonahillslopemayimpacttreatmenteffectiveness. Residence time of mulches varies depending on
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 23

Mulch Effects on Post-Fire Revegetation

Contributed by

Jan Beyers, Research Ecologist, USDA Forest Service, Pacific Southwest Research Station 

A study was conducted on the 2002 Indian Fire on Prescott National Forest in Arizona to determine the effectiveness of three

mulch treatments—wood chips (SB3-fig. 1), rice straw (SB3-fig. 2), and pulverized rice-straw and PAM pellets (SB3-fig. 3). In

addition to the sediment yield data (see Appendix Y-Study VI), ground cover and vegetation data were taken on the mulched

research plots immediately after installation (June 2002) and twice each year through post-fire year three. Rice straw pellets

disintegrated as designed and did not appear to inhibit vegetation establishment. Post-fire vegetation recovered more slowly on

straw and wood chip treated slopes (SB3-fig. 4). Wood chip mulch retained the greatest ground cover over time (SB3-fig. 5)

and had the lowest sediment production compared to the control.

By 2007, five years after the fire, no difference in vegetation recovery was observed among treatments (SB3-fig. 6) (Beyers,

personal communication).

SB3-fig. 1. Wood chips used for post-fire hillslope 

treatment. Note that wood chips that were entrained 

in the overland flow are piled at the outlet of the swale.

SB3-fig. 2. Rice straw applied as post-fire hillslope 

treatment.

SB3-fig. 6. The same swale (treated with wood chips) 

shown in SB3-fig. 1 is pictured here in 2007—post-fire 

year five.

SB3-fig. 3. Pellets of pulverized rice straw and granular 

PAM were applied dry and compressed and are shown 

here after a rain expanded the pellets. The insert in the 

upper right corner shows the small rice straw fibers more 

closely (felt tip pen inserted for scale). 

SB3-fig. 4. The mean percent cover that is live vegetation is 

shown by treatment and by post-fire year.

SB3-fig. 5. The mean percent bare soil is shown by treatment 

and by post-fire year.
24 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

the type, size, and amount of the mulch material applied.

Rice strawisstouter and,thus,more durable thanwheat or

barley straw, which can increase itsresidence time on the

ground but makes the application more time-consuming

and costly than other agriculturalstraws.Woody mulches

are decay resistant—wood strands were clearly visible

seven years after application on the 2002 Hayman Fire

in Colorado (P.R. Robichaud 2009 field observation).

In contrast, hydromulch generally decays within a few

months to a year (Bautista and others 2009). The rapid

decay of hydromulch may result in much less ground

coverthan deemed necessary for hillslope stabilization in

the first and second post-fire years. Hubbert(unpublished

report 2005) reported that the hydromulch that had been

applied on the Cedar Fire in southern California was

greatly reduced following the first winter rains and was

completely gone from the site following the heavy winter

rains of the second year.

Wind Redistribution—The light weight of agricultural

straw mulch makesitsusceptible to strong windsthat can

blow it off-site, leaving unprotected bare soil and deep

mulch piles that inhibit seed germination. After the 2003

GrandPrix/OldFireontheSanBernardinoNationalForest,

strong Santa Anna winds blew the straw mulch into thick

piles,leaving large areas of exposed soil(Hubbert, unpublished report 2005). The flooding events that occurred

in conjunction with the Christmas Day Storm (25 Dec

2003) were partly attributed to the loss of effective straw

coverin some treatedwatersheds.Wind displacement can

be minimized by increasing the mulching rate (>1.5 ton

ac

–1 [3 Mg ha–1]), pushing the straw mulch into the soil

(crimping), adding a tackifier to “glue” the mulch strands

to one another and to the soil, or felling trees on top of the

mulch at a right angle to the prevailing winds to hold it in

place (Bautista and others 2009; Napper 2006).

Woodmulcheshavegreaterresistance towinddisplacementandprovidegreaterwinderosionreductionthanstraw

mulch.Inwind tunnel testing,wood strandmulch resisted

wind velocities of up to 40 mi h–1 (18 m s

–1), while wheat

strawmulch moved at wind speeds of 15 mi h–1 (6.5 m s

–1)

(Copeland and others 2009).

Hydromulch can resist wind displacement during the

first 6 to 12 months after application but likely loses this

capacityasthe tackifierdegrades(Etra2007).Inanareaof

burned-oversand dunes, hydromulch was applied tomitigate potential “brownouts,” situations in which sands are

blown over a highway, causing severely reduced visibility.

Tice (2006) reported that soon after the hydromulch had

been installed, wind speeds of over 50 mi h–1 (80 km h–1)

occurred with little or no wind erosion from the dunes

treated with hydromulch; however, the article did not say

how effective the treatment was over time.

Strand Length—Faucette and others (2007) compared

the hydrological function of mulch materials to the litter

and humus components of the natural forest floor; the

larger mulch particles (analogous to forest floor litter)

function primarily to reduce sediment yield, while the

smaller mulch particles(analogousto forest floor humus)

primarily absorb rainfall to reduce runoff. In studies,

long-stranded mulches (for example, agricultural straws,

wood shreds, ponderosa pine needles, etc.) have been

observed forming “mini-debris dams” as mulch fibers

become interlocked along flow paths on the slope. These

mulch clumps contort overland flow paths, slow the flow

velocity, and hold sediment on the hillslope (Foltz and

Copeland2009;GroenierandShowers2004;Pannkukand

Robichaud 2003; Yanosek and others 2006). In addition,

long fiber mulches require greater shear force to displace

them compared to shorter-fiber mulches (Groenier and

Showers 2004). Hydromulches tend to have thin, short

fibers and depend on the formation of a smoothmat and/or

soiladherenceforeffectiveness(Bautistaandothers2009).

Mulch Treatment Effectiveness

There are few completed studies that measured the

effectiveness of mulch in reducing post-fire runoff and/

or erosion, and most of the available studies are of short

duration. Of the field- and lab-based studies described in

Appendix C, only one has data through three post-fire

years (see Appendix C-Study II). Longer-term studies at

different scales of measurement are on-going, but data

have not been analyzed or published.

Agricultural Straw—Robichaud and others (2000)

summarized results from four quantitative studies of

post-fire straw mulching treatment effectivenessthat had

been completed prior to 2000. All four studies reported

a significant reduction in sediment yield due to straw

mulching. Since 2000, the data consistently show that

straw mulch (ground cover of over 60 percent) is highly

effective in reducing post-fire hillslope erosion on steep

(up to 65 percent) slopes (Napper 2006). Examples of

measured effectiveness include:

	 After the Cerro Grande Fire in New Mexico, the

application of straw mulch with seed reduced mean

annual sediment yields by 70 percent in the first

post-fire year and 95 percent in the second post-fire

year; however, precipitation was below normal during the two study years (Dean 2001) (see Appendix

C-Study I).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 25

	 Wagenbrenner and others(2006) reported thatstraw

mulch immediately increased themean ground cover

tonearly80percentandfacilitatedvegetativeregrowth

after the 2000 Bobcat Fire in Colorado. Mulching

did not reduce sediment yields in the year of the fire

when a large amount ofsediment was produced from

a single 5- to 10-year return interval storm. Yet, in

post-fire years one, two, and three, there was over

95 percent reduction in mean sediment yield on the

strawmulchtreatedplotsascomparedtotheuntreated

control plots (Wagenbrenner and others 2006) (see

Appendix C-Study II).

	 Usingpairedswaleplotsinstalledonthe2002Hayman

Fire, Rough (2007) measured reductions in sediment yields of 94 percent in post-fire year one and

90 percent in post-fire year two on the straw mulch

swale compared to the untreated control swale (see

Appendix C-Study III).

	 After a 1991 wildfire in northeastern Spain, hillslope

plots were established on steep hillslopes of two differentsoils(gypsiferous and calcareous) to study the

effectiveness of dry barley straw mulch combined

withseedingandseedingaloneforreducingsediment

yields.Bothtreatmentssignificantlyreducedsediment

yields as compared to the untreated controls on both

soils and in both post-fire years one and two. Except

for post-fire year one on gypsiferous soil, there were

nosignificantdifferencesbetweenthemeansediment

yields for mulch and seed combination and seeding

alone within each soil type and post-fire year (Badia

and Marti 2000) (see Appendix C-Study IV).

	 Immediately after the 2002 Indian Fire, one set of

paired swales was used to compare sediment yields

from a straw mulch treated plot and an untreated

control plot after a high intensity (I10 = 4.6 inch h–1

[117 mm h–1]) rain event. The straw mulch reduced

the sediment yield by 81 percent compared to the

control (Riechers and others 2008) (see Appendix

C-Study VI).

	 Rainfall simulations (I = 3.3 inch h–1 [83 mm h–1])

were done on small (5.3 ft2 [0.5 m

2

]) hillslope plots

after the 2002 Fox Creek Fire. In post-fire year 1, the

10 wheat straw mulched plots had 86 percent less

sediment compared to the 10 control plots. (Groen

and Woods 2008) (see Appendix C-Study VII).

	 In the area burned by the 2002 Hayman Fire, aerial

straw mulch treatment (1 ton ac

–1 [2.5 Mg ha–1])

is being evaluated using a paired watershed study.

Preliminary results show that the watershed treated

with straw mulch reduced erosion by 63 percent in

the first post-fire year and 68 percent in the second

post-fire year as compared to the untreated control

watershed (Robichaud and Wagenbrenner, unpublished report 2006).

Given the measured effectiveness of straw mulch in

reducing post-fire erosion, it is considered one of the

more cost-effective emergency stabilization treatments

currently available.

Wood-Based Mulches—Woodmulchesareapromising

new material for use in post-fire hillslope stabilization.

Preliminary and laboratory-based studies indicate that

manufactured wood mulch products as well as shredded

trees can be equal to or more effective than straw mulch

in reducing post-fire hillslope erosion. Examplesinclude:

	 Immediately after the 2002 Indian Fire, one set of

paired swales was used to compare sediment yields

from a wood chip mulched plot and an untreated

control plot after three erosion-causing summer rain

events. The wood chip mulch reduced the sediment

yield by about 95 percent compared to the control

forthe first two smallerrain events; the effectiveness

decreasedforthethird,highintensity(I10=4.6inchh–1

[117 mm h–1]) rain event when the wood chip mulch

reducedsedimentyieldsbylessthan68percent.After

the third rain event, wood chips were observed at the

bottomoftheslopewheretheyhadbeendepositedafter

beingwasheddownslopebyoverlandflows(Riechers

and others 2008) (see Appendix C-Study VI).

	 Wood strands, a manufactured wood mulch product,

have been tested in two laboratory rainfall/overland

flow simulation studies using screened forest soils

in a rectangular plot placed at a 30 percent slope. In

the first study, several sizes of wood strands were

compared to equal cover amounts of agricultural

straw,anditwasshownthatwheatstrawandtwosizes

of wood strands were equally effective at reducing

erosion by over 98 percent (Foltz and Dooley 2003).

Building on these results, two wood strand blends

were tested on two soil types, two slopes, and three

coverage amounts with simulated rainfall and added

inflow. Compared to the untreated controls, wood

strandmaterialsreduced sediment yield by at least 70

percent for all treatment combinations. In addition,

when compared to sediment yield reductions due to

agriculturalstraw(asreportedbyBurroughsandKing

1989), wood strand materials were equally effective

on coarse-grained soils and superior to straw on

fine-grained soils (Yanosek and others 2006) (see

Appendix C-Study VIII, Lab Study 2).
26 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

	 Wood shreds, a mulch material of variable-sized

pieces produced on site from small-diameter trees

andwoodydebris(GroenierandShowers2004),were

tested using rainfall and overland flow simulation.

Sediment yield reductions ranged from 60 to nearly

100percent,dependingonthesoiltype(gravellysand

had greater sediment yields as compared to sandy

loam), amount of concentrated flow, andmulch cover

amount (Foltz and Copeland 2009) (see Appendix

C-Study VIII, Lab Study 3).

	 Wood shreds were further tested using the same

laboratory rainfall and overland flow simulations on

the burned surface soil and ash collected following

the 2006 Tripod Fire in north-central Washington.

Thisstudywasdonetodeterminetheoptimumstrand

length(s) of wood shredsto use for post-fire hillslope

stabilization. By controlling the proportion of “fine”

shreds(shredslessthan 1 inch [2.5 cm]) in the mulch

blend, three shred blends were evaluated for runoff

and sediment concentration reduction. All the blends

reduced runoff amounts, but the blend with all fine

shreds removed was most effective for both runoff

and sediment yield reduction during rainfall and

rainfall plus concentrated flow.In addition,therewas

no significant difference between 50 and 70 percent

shred ground cover (Foltz and Wagenbrenner 2010)

(see Appendix C-Study VIII, Lab Study 4).

	 After the 2002 Hayman Fire, manufactured wood

strands were one of three treatments (wood strands,

wheat straw, and contour raking) evaluated using

hillslope plots. Of the three treatments, only wood

strands had significantly lower sediment yields as

compared to the control plots in postfire years one

and two. Also, in post-fire year two the remaining

wood strand component of the ground cover was

seven times greater than the remaining wheat straw

componentofthegroundcover,suggestingthatwood

strands have greater longevity as compared to wheat

straw (Robichaud and Wagenbrenner, unpublished

report 2006).

	 InSpain,Bautista andothers(2009)foundthat anatural mulch (shredded forest debris), with and without

seeds,washighlyeffectiveatreducingerosion.During

the first post-fire year, average sediment yield from

untreated plots was about 9 ton ac

–1 (20 Mg ha–1), but

mulchedsiteshadnegligiblesedimentyields(Bautista

and others 2009).

Giventhepotentialeffectivenessindicatedbythesestudies,

themanufacture, transportation, and broadcast application ofwood-basedmulchesareevolvingtoaccommodate

its use in post-fire hillslope stabilization. Several wood

mulch post-fire treatment effectiveness studies are in

progress on burned areas of the 2002 Hayman Fire

(Front Range, Colorado), 2005 School Fire (southeastern

Washington), 2007CascadeComplexFire (centralIdaho),

and 2008 Jesusita Fire (southwest California).

Natural Burned Needle Cast Mulch—

	 Conifer forests burned at low and moderate severity

often have trees that are charred and partially consumed by fire, leaving dead needles in the canopy.

These needles fall to the ground or are blown from

the charred canopy by the wind to provide a natural

mulch ground cover. In a rainfall and overland flow

simulationlaboratorystudy,PannkukandRobichaud

(2003) tested the effectiveness of 50 percent ground

cover of Douglas-fir and ponderosa pine needle cast.

The short, flat Douglas-fir needles laid directly on

the ground for their full length and reduced interrill erosion by 80 percent compared to a 60 percent

reduction with ponderosa pine needles. The long,

bundled, and curved ponderosa pine needles tended

to form mini-debris dams on the soil surface and

reduced rill erosion by 40 percent compared to a 20

percentreductionwithDouglas-firneedles.Although

the natural needle cast mulch is effective, it generally is unavailable in high burn severity areas where

the needles are consumed by the fire (Pannkuk and

Robichaud 2003) (see Appendix C-Study VIII, Lab

Study 1).

Hydromulch—Hydromulching is relatively new in postfire hillslope stabilization, and effectiveness data are

scarce. However, effectiveness monitoring indicates that

hydromulch may reduce sediment yields during the first

few storms, but it shows little resistance to concentrated

flow, degrades quickly, and its long-term effectiveness is

not known.

	 Afterthe2002HaymanFire,1560ac(630ha)ofsteep,

inaccessible hillslopeswere treatedwith hydromulch

toprotectDenver’smunicipalwaterreservoirsystem,

and another 1500 ac (610 ha) adjacent to forest roads

weretreatedusingtruck-mountedsprayers(Robichaud

and others 2003). In post-fire year one, the aerial

hydromulch reduced sediment yield by 95 percent

as compared to the control; in post-fire year two, the

sediment yield reduction was 50 percent. However,

the ground-based application of hydromulch did not

significantly reduce sediment yields as compared

to the control plots in either year (Rough 2007) (see

Appendix C-Study III).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 27

	 The aerialhydromulchtreatment atthe2002Hayman

Fire is also being evaluated using a paired watershed study, and the preliminary data show that the

hydromulch was less effective in reducing erosion

during the first and second post-fire years than was

reported by Rough (2007). The sediment yield from

thehydromulchtreatedwatershedwasonly18percent

less in the first post-fire year and 27 percent less in

the second post-fire year as compared to the sediment

yields from the control watershed (Robichaud and

Wagenbrenner, unpublished report 2006).

	 After the 2003 Cedar Fire in southern California,

hillslopes burned at high soil burn severity were

treated with aerial hydromulch using two configurations—application over 100 percent of the treatment

area (H100) and application of 100 ft (30 m) wide

contour strips of hydromulch such that 50 percent of

the area wastreated (H50). A paired watershed study

is being used to measure treatment effectiveness, but

differences in rainfall between the watersheds have

confounded the preliminary results. The H50 watershed, which is approximately 1 mi (1.6 km) from the

H100andcontrolwatersheds,receivedgreaterrainfall

amountsathigherintensitiesincomparisontotheother

two.In 2003, the year ofthe fire, the H100 watershed

reduced the sediment yield by 53 percent compared

to the control, and the H50 watershed had a larger

sediment yield than either of the other two. In postfire year one, the control and the H100 watersheds

had over three times more rainfall at greater intensities than the previous year, but the H50 watershed

again had greater rainfall amount and intensity than

either of these. These greater rain amounts resulted

in greater sediment yields in all the watersheds. The

H100 watershed had 43 percent less sediment compared to the control; and the H50 watershed, despite

its larger, more intense rainfall, had 37 percent less

sediment compared to the control (Wohlgemuth and

others, unpublished report 2006).

	 The effectiveness of the hydromulch treatment on

the Cedar Fire was also monitored using hillslope

plots with silt fence sediment traps (Robichaud

and Brown 2002). In post-fire year one, the

H50 hydromulch reduced sediment yields by

more than 50 percent, and the H100 hydromulch

cover reduced sediment yields by about 75 percent (Hubbert, unpublished report 2007) (see

Appendix C-Study V).

The use of hydromulch treatments for post-fire hillslope

stabilizationareofparticularinterestinthesteepchaparral

areas ofsouthern California where wildfires are common

and the Santa Anna winds are known to dislocate and

deeply pile lighter dry mulches, leaving bare soil exposed

to winter rains. Besides the ongoing studies discussed

above, post-fire hydromulch treatments for hillslope

stabilization are being studied on three recent southern

California fires—the 2007 Santiago Fire, the 2008 Gap

Fire, and the 2009 Jesusita Fire.

Chemical Soil Surface 

Treatments _____________________

Tackifiers, orsoil binding agents, are mixed with fiber,

seeds, and/or fertilizer for use in hydromulching and

hydro-seeding; however, tackifiers may be used alone as

a surface soil treatment. Soil binders are applied by putting theminto solution and spraying themon the soil or by

spreading solid granulated particles on the soilwhere they

can dissolve in rain and/or overland flow. When the soil

binder solution dries, it forms a thin web of polymer that

coats the soil particle surfaces at the water-soil interface,

which increases the shear force needed to detach those

particles (Sojka and others 2007). In addition, some soil

binders such as polyacrylamide (PAM) are flocculants

that can connect small particles, thus increasing their

size and mass, which allows them to settle out of solution

and be deposited (Sojka and others 2007). Some research

has shown that chemical surface treatments reduce soil

sealing and erosionmore effectively when combined with

physical treatments such as mulch or erosion barriers

(McLaughlin 2007; McLaughlin and others 2009; Zhang

and others 1998).

Chemicalsoilbindersareoftenclassifiedbytheirsource.

Natural or organic binders such as guar and starches are

derived from plant materials, and synthetic binders such

as polyacrylamide (PAM) formulations are derived from

petroleum products. Though natural guar tackifiers have

been used in post-fire hydromulch treatments (Moore,

personal communication),PAMistheonlysoil binderthat

hasbeenusedasapost-firehillslopestabilizationtreatment.

PAM is a class of synthetic polymers with hundreds of

specificformulationsthatcanbecategorizedbymolecular

structure (linear or cross-linked), charge (anionic—negatively charged; cationic—positively charged; or nonionic—no charge),solubility,molecular weight, and other

characteristics (Sojka and others 2007). Various types of

PAM have been used for over 50 years to improve soil

structure and permeability (Ajwa and Trout 2006). In

agriculture, PAM is mainly used to reduce erosion and

increase infiltration in sprinkler irrigated agricultural

soils and low-flow irrigation trenches (Lentz and Sojka
28 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

2000; Sojka and others 2007). Natural and synthetic

polymers, including PAM, are used on disturbed areas

such as construction sites, mining operations, landfills,

and unpaved roads for dust abatement, erosion control,

soil stabilization, and turbidity reduction in storm water

runoff (Faucette and others 2007; Hayes and others 2005;

Tice 2006). Though tackifiers have been applied over dry

mulches such as straw, pine needles, and wood materials

to bind the material and hold it on the soil surface (Etra

2007; McLaughlin and Brown 2006), this combination

of tackifier on mulch has only recently been tried experimentally as a post-fire hillslope treatment.

Cationic and non-ionic PAMs are known to be toxic for

fish and other aquatic life. However, the class of anionic

PAMs used for soil erosion and infiltration management

shows no measurable toxicity at concentrations of 100

ppm, an order of magnitude safety margin for the highest

concentration of PAM present (10 ppm) in agricultural

applications (Sojka and others 2007). Although negative

environmentalimpactshavenotbeendocumentedwhenthe

anionic PAMs are applied atrecommended concentration

rates, contractors for post-fire hillslope PAM treatment

applications have recommended application rates that

exceed manufacturer recommendations to improve performance (Moore, personal communication). In addition,

there issome concern surrounding the use of PAM due to

the presence ofresidual, unreacted acrylamidemonomers

(AMD), a known neurotoxin and suspected carcinogen in

humans and animals, as a product contaminant. However,

PAM does not revert to AMD on degradation, and the

small residual amounts of AMD contained in PAM are

rapidly metabolized in soil or natural waters by microorganisms(Sojka and others 2007). Though anionic PAMs

are considered safe if used as directed, prolonged skin

exposure and exposure to PAM dust can result in skin

irritation and inflammation ofmucousmembranes(Sojka

and others 2007).

Performance Characteristics of PAM and 

Other Polymers

Longevity—Longevity of soil binders is generally

expressedinmonths,notyears.TheCaliforniaDepartment

of Transportation (2007) developed a management guide

for erosion control on all road construction projects. This

guide includes a comparison matrix of three types of

plant-based materials (including guar and starches) and

five synthetic polymeric chemicals(including PAM) that

are rated on several criteria,including longevity.Guar and

starches,whichdegradethroughbiologicaldecomposition,

have short (1- to 3-month) longevity ratings, while PAM,

which photo-degrades, has a moderate (3- to 12-month)

longevityrating.Giventhatpost-firehillslopestabilization

treatment effectiveness is needed for at least two to three

years while revegetation occurs, the rapid degradation of

PAM and other soil binders is a drawback to their use in

post-fire treatment.

Soil Type and Cation Ion Availability—Adsorption of

PAMonsoilandclaymineralsurfacesdiffersbasedonsoil

texture,organicmattercontent,anddissolvedsalts(Luand

others 2002).PAMhas a high affinity for claymineralsurfacesand,onceadsorbed,isnoteasilyremoved.Generally,

PAM is less easily adsorbed onto coarse-textured soils,

and organic matter tends to interfere with the adsorption

process (Sojka and others 2007). Rough (2007) reported

that PAM preferentially bound to ash over mineral soil

when used after the 2002 Schoonover Fire in Colorado.

Adsorption of anionic PAMs to mineral surfaces,

which carry predominately negative charges, is aided by

an abundance of divalent cations such as Ca2+ (calcium

ions) in the solution. Consequently, PAM is often applied

with gypsum (CaSO4-2H2O) as a source fortheCa2+ ions.

Flanagan and others (2002) compared three treatments

(liquid PAM, liquid PAM plus dry gypsum, and untreated

control) using rainfall simulation on tilled silt loam soil

placed in 32 percent hillslope plots (10 ft [3.0 m] wide

and 30 ft [9.1 m] long). Although the PAM and PAM plus

gypsumresultswerenotsignificantlydifferent,totalrunoff

on the treated plots was 40 to 52 percent less than on the

control plots, and sediment yield on the treated plots was

83 to 91 percent less than on the control plots (Flanagan

and others 2002). Although this study showed that PAM

and PAM plus gypsum provided effective runoff and

sediment yield reductions on steep slopes, it did not look

at the effectiveness of PAM over time.

Viscosity and Infiltration Rate—Much ofthe research

onPAMuseinagriculturalirrigationhasreportedincreases

in infiltration rates, which generally have been attributed

to PAM stabilizing soil surface structure and preventing

the formation of surface seals (Sojka and others 2007).

However, if the soilstructure has already deteriorated (as

is often the case in areas of high soil burn severity) or if

the soil issandy (larger particles and lessstructured soil),

PAM’s tendency to increase viscosity of the infiltrating

water may reduce rather than increase infiltration (Sojka

and others 2007). Ajwa and Trout (2006) used packed

soil column experiments to measure infiltration rates

of an unburned sandy loam soil with a range of PAM

concentration (5 to 20 mg PAM L–1) in the infiltration

water. Final infiltration rates of 5 mg PAM L–1

were 35

percentlesswith emulsifiedPAMand 64 percentlesswith

granular PAM as compared to deionized water, and these
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 29

reductions in infiltration rates increased with increasing

PAMconcentrations(AjwaandTrout2006).Obviously,any

reduction in infiltration would be detrimental in post-fire

stabilization treatments and is a significant disadvantage

to using PAM in burned areas.

Effectiveness of PAM and Other Polymers

The effectiveness of PAM has been documented for use

in agricultural irrigation and in disturbed but not burned

areas; however, only a few of these studies involve the

typesofsoil andwater controlneededinpost-firehillslope

stabilization. Very few studies measure the effectiveness

of PAM or other polymersin post-fire applications. PAM

and guar products have been used in hydromulch mixes

applied for post-fire hillslope stabilization, but there

have been few attempts to evaluate the effectiveness of

the polymer component of the hydromulch treatment.

For example, one of the three mulch treatments Riechers

and others (2008) compared was a manufactured rice

straw pellet that contained PAM (Appendix C-Study VI).

However,PAMeffectiveness could not be evaluated asthe

treatments did not include rice straw pellets without PAM

or PAM applied directly on the soil.

Post-fire treatment effectiveness studies that include

PAM have generally been inconclusive or have shown no

treatment effect. After the 2000 Bobcat Fire in Colorado,

a test using simulated rainfall on small(11 ft2 [1m

2

]), high

burnseverityhillslopeplotsinthenorthernColoradoFront

Range found some initial erosion reduction that disappeared after the first 30 min of the 1-hour rain simulation

(Benavides-Solorio and MacDonald, unpublished report

2000). Following the 2002 Williams Fire in southern

California,sedimentyieldsfromapairofwatersheds(2and

6 ac [0.75 and 2.4 ha])—one treated with aerially applied

PAMandoneuntreated—were comparedforoneyear and

no significant difference was found (Wohlgemuth 2003).

After the 2002 Schoonover Fire in Colorado, PAM was

testedoverthreeyearsonpairedhillslopeswales.PAMwas

reapplied each year to half of the treated swales, and the

other half received only the initial application. Although

the PAMtreatmentsreduced sediment yield during lower,

less intense rainfall periods, it was not effective when

rainfall amounts and intensities increased. These results

were inconclusive, and storm erosivity explained 58 percent of the variability in sediment yields (Rough 2007)

(see Appendix D-Study I).

After the 2004 Red Bull Fire in central Utah, PAM was

oneoffourtreatments(PAM,strawmulch,PAMplusstraw

mulch, anduntreatedcontrol) evaluatedonaeriallyseeded

sites. Erosion bridges (three per treatment) were used to

measure soil movement over three years. No rainfall data

were reported and the small differences in net soil movementwere notsignificant(Davidson and others 2009)(see

Appendix D-Study II).

Treatment Combinations _________

Combining seeding with other treatments, especially

mulching, is relatively common on burned hillslopes.

Often, large areas burned at high and moderate severity

have been treated with broadcast seeding, and areas that

areparticularlyvulnerabletoerosionaredrymulchedover

the seeding to provide immediate ground cover and hold

seeds and moisture to enhance potential seed germination. Seeds are often included in hydromulch mixes and

appliedwith themulch slurry.Post-fire treatments applied

to establish seeded plants (main objective) are reviewed

in separate syntheses by Jan Beyers and several others

(as described in the Preface). The combination treatment

studies discussed here include those studies in which

seeding and other erosion control measures were applied

and erosion control was the primary objective.

If treatment effectiveness studies were done on erosion

barriers, mulching, or PAM in combination with seeding,

they have been presented in the previous section related

to the non-seeding portion of the treatment. There is

one additional study of a treatment—hand scarification

(using McLeod rakes to disturb the surface soil)—that

was combined with seeding that does not fit into any of

the previous sections. In this study, Rough (2007) found

no difference in sediment yields among paired swalesthat

were hand scarified and seeded and the untreated controls

(see Appendix E-Study I).

Treatment combinations that include two or more

hillslope treatments other than seeding are not common.

Given the expense of hillslope treatments, it is difficult

to justify applying more than a single treatment in one

area. After the 2000 Cerro Grande Fire in New Mexico,

Dean (2001) found that a combination of contour-felled

log erosion barriers (LEBs), straw mulch, and seeding

significantly (p<0.05) reduced sediment yieldsfrom hillslope plots by 77 percent in the year of the fire and by 96

percent in post-fire year one. However, these results were

not significantly different than the reduction in sediment

yields from plots treated with straw mulch and seeding;

Dean (2001) concluded that the LEBs added no additional

erosionmitigationoverthe strawmulchplusseedingtreatment (see Appendix E-Study II).

Whenresourcesthatareatriskfordamageduetoerosion

are of very high value and/or difficult to repair, erosion

mitigation treatments may be combined to provide more

protection for the values-at-risk. For example, after the
30 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

2002MissionaryRidgeFire inColorado,several hillslope

erosioncontrolmeasuresandsomechanneltreatmentswere

installed at higherthan normal density aboveLemonDam

toprotecttheintakestructuresofthedamfrombeingfilled

with sediment. Since the dam is a critical component of

thewatersupply systemforthe city ofDurango,Colorado,

the Water Conservation District was anxious to ensure

continuous facility operation (deWolfe and others 2008).

The hillslope treatmentsincluded:LEBs at90to250LEBs

ac

–1 (220 to 620 LEBs ha–1), 200 to 600 percent of typical;

hand-spread and crimped straw mulch at 2.5 ton ac

–1

(5.6 Mg ha–1), 125 percent of typical; and hand-spread

seeding at 60 to 75 lbs ac

–1 (67 to 84 kg ha–1), 150 percent

of typical. In addition, 13 check dams and 3 debris racks

were installed in the main drainage channel of the basin.

The erosion barriers, check dams, and debris racks were

cleanedoutandrehabilitatedaftereachsediment-producing

stormtoensuremaximumperformance forthenext event.

This combination of treatments virtually eliminated

sedimentation into the reservoir. The authors attribute the

successofthistreatmentcombinationto1)thehighdensity

of application for each treatment, 2) the enhancement of

treatments working in concert, 3)the quality oftreatment

installation, and 4) sediment and debris removal from

barrier treatments and repair of treatmentsto extend their

useful life (deWolfe and others 2008).

Management Implications_________

Post-fire emergency hillslope stabilization treatments

cannot prevent erosion, but they can reduce overland

flow, erosion, and sedimentation forsome rainfall events,

thereby reducing the risk to public safety and risk of damage to structures,roads, water quality, and critical habitat.

However, the effectiveness of any hillslope stabilization

treatment depends on actualrainfall amounts and intensities, especially in the first post-fire years(Robichaud and

others 2000; Robichaud 2005). Wagenbrenner and others

(2006) found that none of the treatments, including straw

mulch, were effective in reducing sediment yields from

large, high-intensity storm events after the 2000 Bobcat

Fire inColorado. The need to protect the valued resources

in and around burned areas hasmotivated effortsto refine

post-fireerosionpredictionmodels,improvetheeffectiveness of post-fire rehabilitation treatments, and evaluate

new treatment technologies.

Longer-Term Treatment Effectiveness

BAERtreatments are, by definition, emergency protection of public safety and short-termstabilization of burned

landscapes. When the BAER program was established, it

wasgenerallyassumedthatmostburnedsiteswerewellstabilizedwithinthreeyearsofburning.Subsequentresearch

hasshown that thisis not alwaysthe case (Robichaud and

others 2008b). Some sites, especially in arid or semi-arid

regions where naturally sparse ground vegetation leaves

exposed soil, may need erosion protection for more than

three years after a fire.Thus,the length oftime a treatment

remains effective has becomemore important aswebetter

understand the recovery process for various ecosystems.

Choosing Treatments

Since 2000, post-fire treatment spending and fire suppression costs have increased, and like fire suppression

spending, BAER costs have come under scrutiny, and

cost containment protocols are being explored. Treatment

justification has been reframed from “reducing a threat”

to “protecting values-at-risk” so that the values-at-risk

for damage or loss are clearly identified before an area is

designated for treatment (Calkins and others 2007). The

costofrepairingorreplacingthoseidentifiedvalues-at-risk

is weighed against the cost of treatment and the potential

treatment success. In some burned areas, the “no treatment” option may be the most appropriate response. This

is particularly true for areas burned at low or moderate

severity where adequate ground cover is provided by

remaining forest floor material and natural mulch, such

as scorched conifer needles, and for areas where rapid

natural recovery is expected.

The no treatment option may also be appropriate in

areas burned at high severity that do not pose a high risk

to identified values.Calkins and others(2007) have developed a Value-at-Risk assessment tool (the VAR tool) to

assist BAER teams with the cost-risk analysis needed to

justify post-fire treatment decisions. This procedure can

be helpful as it provides a framework to identify downstream values, provides monetary values when available,

and uses the implied minimum value (Calkins and others

2007) for non-monetary values-at-risk (water quality,

habitat for threatened species, recreational value, etc.).

In addition, the VAR tool incorporates the probability

of treatment success, an essential part of this valuation

process that may be determined through modeling (such

as the Erosion Risk Management Tool [ERMiT]) and/or

professional judgment (Calkins and others 2007). This

approach emphasizes the need to select treatments that

are known to be effective and to apply those treatments

in areas where stability is needed to protect public safety

and/or valued resources. Once it is established that there

arevalues-at-riskandthatBAERtreatmentsarenecessary

to stabilize hillslopes above and upstream ofthose values,

there is still the question of which treatment(s) to use.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 31

Protecting a Municipal Water Supply

Contributed by 

Jennifer Hickenbottom Rick Patten Bruce Sims

Forest Hydrologist Forest Hydrologist (retired) Regional Hydrologist

Coville National Forest, WA Northern Region, Missoula, MT

The 2003 Myrtle Fire burned 3600 ac (1460 ha) within the municipal watershed of Bonners Ferry,

Idaho. The steep, burned area was aerially straw mulched and seeded, and areas along all roads were

hydromulched and seeded. Light rains followed the fire, and both seeded and natural vegetation was

very robust, providing an effective ground cover over much of the burned area (uncommon in postfire year one). On 4 July 2004, one year after the fire, a high intensity storm of 1.6 inch (41 mm) of

rain in two hours occurred over the burned area. Nearly all ephemeral draws within the burned area

had surface flow, but erosion wasrelatively minor because the draws were well vegetated (SB4-fig.1).

Despite the protection from dense vegetation, the State of Idaho municipal water supply turbidity

standard (50 NTU) was greatly exceeded (SB4-fig. 2). This spike in turbidity was short-lived; about

nine hours afterthe surge in turbidity had begun, the readings were nearing pre-stormlevels(SB4-fig.

2). The city of Bonners Ferry maintained continuous water service to its customers by using back-up

sources while allowing substandard surface water to bypass its system.

SB4-fig. 1. Photo taken after the 4 July 2004 storm 

showing overland flow in a swale near the top of the 

ridge above Myrtle Creek. 

SB4-fig. 2. Graph of the hourly turbidity monitoring 

measurements for Myrtle Creek, Bonners Ferry primary 

municipal water source, on 4 July 2004, 10 months after 

the Myrtle Creek Fire. The graph shows a pulse of sediment 

that passed through the system due to storm runoff. (Water 

Quality monitoring data from the City of Bonners Ferry Water 

and Sewer Department.)
32 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Post-Fire Recovery

Contributed by

Peter R. Robichaud

Research Engineer 

USDA Forest Service

Rocky Mountain Research Station 

The potential for dramatic increasesin hillslope erosion after firesis well documented (see Moody

and Martin 2009 for a synthesis of post-fire sediment yields in the western United States). The time

needed for burned hillslopesto recover, orreturn to the pre-fire erosion potential, is not aswell known.

Based on limited data, thisrecovery time is estimated to be about three yearsfor most western forests,

and the effectiveness of post-fire hillslope stabilization treatments are generally evaluated using this

time frame. During the pastfew years,some longer-term monitoring projects have provided evidence

suggesting that the recovery time needed for post-fire hillslope stability may be longer than three

years (SB5-fig. 1).

Themagnitude ofthepotential post-fire erosion response isdependent on burn severity,topography,

soil type, soil moisture, and ground cover (live vegetation and litter). The actual erosion response is

dependent on rainfall characteristics—especially intensity and amount. In the first two years after a

fire, rainfall intensities with lessthan two-year return intervals have resulted in large sediment yields

in many locations (Moody and Martin 2009). Although it generally takes a larger rain event to trigger a large erosion response after three or four post-fire recovery years, such responses have been

documented (see Appendix B, table AB-5 for PFy5 [high intensity storm] and PFy6 [long-duration

storm]; see also table AB-9 for PFy4 [high intensity storm]). These observations confirm that the

potentialerosionresponseremainsabovepre-firelevelsformorethanthreeyearsinsomeburnedareas.

SB5-fig. 1. In post-fire year four, a paired watershed 

study site on the 2002 Cannon Fire in California had 

a rainfall event with maximum 10-min intensity (I10) of 

6.22 inch h–1 (158 mm h–1). The sediment basin filled 

and then over-topped, depositing large rocks and tree 

debris both inside and outside the sheet metal wall that 

forms the sediment basin. The sediment yield from the 

contour-felled log treated catchment was estimated 

at over 3.9 ton ac–1 (8.7 Mg ha–1) (see table AB-9 in 

Appendix B).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 33

There is no single best approach to post-fire hillslope

stabilization. Appendix A contains a chart that summarizes the known effectiveness and specific performance

issues related to the post-fire treatments currently in use.

However, each BAER team will have to match their treatmentrecommendationsto the specific environmental and

climaticfactors,burnconditions,andprobablehydrological

responses of the area.

Monitoring Post-Fire Treatment 

Effectiveness

When BAER teams recommend hillslope treatments,

theyoftenadaptapplicationrates,mulchformulations,and/

ortreatment combinationstoimprove treatment effectiveness or to accommodate the climate or topography of the

area being treated.The adaptationsin treatment protocols

combinedwiththedistinctivecharacteristicsofeachburned

area make each post-fire treatment installation unique.

Monitoring the effectiveness of the specific treatment

type and application rate for the climate (specifically the

rainfall characteristics), topography, and burn severity

of the area can provide valuable information to improve

treatmentselection.Measurementsoftreatment effectiveness are most useful when they are directly related to the

objective(s) of the treatment. For example, if a hillslope

treatment is applied to reduce runoff and erosion, then

the monitoring should measure rainfall characteristics,

hillslope runoff, and erosion rates overseveral years.With

thesedatawecanevaluatetreatmenteffectivenessinterms

ofthe characteristicsthat are known to limit effectiveness.

Using the “Best Available” Treatments

The selection of “best available” can be challenging

for BAER teams. This synthesis is a direct response to

the need for reporting and comparing hillslope treatment

effectiveness information. However, a printed document

isstatic—adescriptionofour currentknowledge.Aspostfiretreatmentsimproveandnewoptionsbecomeavailable,

they too will need to be evaluated. The information on

treatmentperformance characteristics andenvironmental

factorsthat impact treatment effectiveness can be applied

to these future choices even if the specific treatment

is not included in this synthesis. A hillslope treatment

effectiveness web page (http://forest.moscowfsl.wsu.edu/

BAERTOOLS/HillslopeTrt)hasbeenaddedtooursuiteof

BAERTOOLSwebpages.Informationfromthissynthesis

is posted on the web page, and new information will be

posted as it becomes available.

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38 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Appendix A. Hillslope Treatment Effectiveness and Performance 

Characteristics Summary Table ______________________________________

Table AA-1. Ratings of post-fire hillslope stabilization treatment effectiveness for three rainfall regimes (high intensity, low intensity, and high 

total amount; see fig. 4 and table 1 in main text) are presented in the table below. Treatment effectiveness codes: 1 = more effective; 

2 = somewhat effective; and 3 = not effective. Treatments are also rated as more likely (more) or less likely (less) to exhibit performance 

characteristics that impact treatment effectiveness, post-fire recovery, and/or the environment. Other phrases are used to describe the 

performance characteristics of treatments that are dependent on circumstances or are not effectively rated as more or less likely. Details 

of treatment performance characteristics can be found in the individual treatment sections of the main text. 

Straw Wood Hydro- Soil binders Contour-felled Straw

mulches mulches mulches (PAM) logs (LEBs) wattles

Overall High intensity rainfall 1 1 3 3 3 3

effectiveness (>2-yr return interval)

(rating: 1, 2, or 3)

Low intensity rainfall 1 1 1 2 1 1

High rainfall amount 1 1 2 3 2 2

(>2 inch [50 mm] in 6 hr)

Performance Resistant to wind lessa morea more more more more

characteristics displacement

that impact

effectiveness Remains functional for more more less less more more

more than 1 year

Provides ground cover more more more less less less

Increases infiltration more more not known depends on less less 

conditions

Increases soil moisture more more more less less less

retention

Shortens flow paths more more less less more more

Traps sediment more more less less more more

Slows development of more more more more less less

concentrated flow 

Other Contains noxious weed possible less less less less possible

considerations seeds

Delays revegetation depends on depends on less less less less 

mulch thickness mulch thickness

Harmful to the less less depends on depends on less less

environment components type and

concentration

a In wind tunnel tests, agricultural straw resisted movement in wind speeds of 15 mi h–1 (6.5 m s–1), and wood straw resisted movement in wind speeds of 40 mi h–1

(18 m s–1) (Copeland and others 2006).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 39

Appendix B. Erosion Barrier Treatment Effectiveness Studies (2000 to the 

present) _________________________________________________________

Study I. Effectiveness of contour-felled logs (LEBs) in reducing sediment following the 2000 Bobcat Fire in central 

Colorado (Wagenbrenner and others 2006)

Study design: Contour-felled logs (LEBs) were hand-installed at a mean rate of 900 ft ac

–1 (680 m ha–1) on

20 to 35 percentslopesthat were burned at high severity. Silt fence sediment traps were established at the base

of paired swales to compare the sediment yields from treated and untreated areas.

Plot size(s): Paired swales ranged from 0.25 to 1.25 ac (0.1 to 0.5 ha), and each swale included a zero-order

channel formed by convergent hillslopes.

Factors that impacted study design and/or results: 

•	 In the year of the fire (FY), a large storm compromised storage capacity of the LEBsthat had been installed.

The old LEB plotsremained in the study; however, new treated swales were established with sediment traps

and compared to their paired control. In table AB-1, the sediment yieldsfrom the swale plotsinstalled before

the storm are labeled “old,” and the sediment yieldsfrom the swale plotsinstalled after the storm are labeled

“new.” 

•	 In post-fire year three (PFy3), the two general study areas had different rainfall. Both rainfall amounts are

reported (table AB-1).

Generalized results:

LEBs were ineffective in large storms but could be effective for small events given sufficient sediment storage

capacity (Wagenbrenner and others 2006).

Table AB-1. Results from LEB study following the 2000 Bobcat Fire. Rainfall amount, maximum 30-min 

intensity (I30), and mean annual sediment yields are reported for each of the four years of the 

study. Mean percent difference in sediment yield between the control and the treated swales are 

reported for each year. Time since fire codes: FY = year of the fire; PFy1 = 1 year after the fire; 

PFy2 = 2 years after the fire; and PFy3 = 3 years after the fire (Wagenbrenner and others 2006).

Time 

since 

fire

------------Rainfall----------- -------------------------Sediment yields-------------------------

Amount

(inch [mm])

I30

(inch h–1

[mm h–1])

Control

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Treated

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Difference

(%)

FY 2.4 [60] 1.9 [48] 2.8 [6.2] olda

-2.6 [5.8]

newb-NA

old-7.1

new-NA

PFy1 3.0 [75] 1.1 [29] 4.2 [9.5] old-2.5 [5.7]

new-1.2 [2.8]

old-40

new-71

PFy2 1.4 [36] 0.67 [17] 0.54 [1.2] old-0.01 [0.03]

new-0.09 [0.2]

old-98

new-83

PFy3 0.67 [17]

4.3 [110]

0.71 [18]

1.4 [35] 0.3 [0.7] old-0.009 [0.02]

new-0.03 [0.07]

old-97

new-10

a old = sediment yields from plots installed before the large storm that occurred the same year as the fire. b new = sediment yields from plots installed after the large storm that occurred the same year as the fire.
40 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study II. Measured effectiveness of LEBs in reducing sediment, and the effect of study plot size on these 

measurements; the 2000 Hi Meadows Fire in central Colorado (Gartner 2003)

Study design: In post-fire year one, a two-month study (1 Jul 01 to 31 Aug 01) examined the effect of study

plot size on LEB treatment effectiveness in reducing sediment yield. LEBs were installed at a rate of 71 LEBs

ac

–1 (175 LEBs ha–1) or 320 LEB ft ac–1 (240 LEB m ha–1) on steep slopesthat had been burned at high severity.

Plot size(s): Two paired catchments of ~40 ac (~16 ha) were selected and one was treated with LEBs. Nested

within these two catchments were plots (10 to 50 ft2 [1 to 5 m

2

]), hillslopes (~4,300 ft2 [~400 m

2

]), and subcatchments(2.5 to 12 ac [1 to 5 ha]).Cumulative (two-month)sediment yieldswere determined forthe hillslopes,

sub-catchments, and catchments, while sediment flux (lb ft–1 [kg m

–1]) was measured on the smallest plots.

Generalized results:

LEBs generally were effective for low intensity rain events observed during the two-month study period

(Gartner 2003).

Table AB-2. Results from LEB study following the 2000 Hi Meadows Fire. Rainfall amount and maximum 10-min 

intensity (I10) are reported for the study area. Mean sediment flux (lb ft –1 [kg m–1]) is reported for plots. Mean 

cumulative sediment yields (ton ac–1 2-mo–1 [Mg ha–12-mo–1]) for the hillslopes, sub-catchments, and 

catchments are reported for the study period of 2 months. Mean percent difference in sediment yield between 

the paired control and the treated study areas are reported. Time since fire code: PFy1 = 1 year after the fire 

(Gartner 2003).

Time 

since 

fire

-------------Rainfall-------------- --------------------------Sediment yields------------------------

Amount

(inch 2-mo–1

[mm 2-mo–1])

I10

(inch h–1

[mm h–1])

Control

(lb ft –1

[kg m–1])

Treated

(lb ft –1

[kg m–1])

Difference

(%)

PFy1 4.2 [107] 1.3 [34] Plots 511 [762] 107 [161] 79

Control

(ton ac–1 2-mo–1

[Mg ha–1 2-mo–1])

Treated

(ton ac–1 2-mo–1

[Mg ha–1 2-mo–1])

Hillslopes 1.3 [2.8] 0.21 [0.46] 84

Subcatchment 0.29 [0.64] 0.27 [0.61] 7

Catchment 0.38 [0.86] 0.05 [0.11] 87
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 41

Study III. Comparing the effectiveness of three erosion barrier treatments in reducing sediment following the 

2000 Valley Complex Fire in western Montana (Robichaud and others 2008a)

Study design: Sixteen hillslope plots with a single erosion barrier installed across the lower width of each

treated plot were established immediately after the fire on steep planar slopes burned at high severity. Four

repetitions of four treatments (LEBs, straw wattles, hand dug contour trenches, and untreated controls) were

randomly applied. Low intensity rainfall plus overland flow simulations were used immediately after the fire

(2000) to measure treatment effectiveness. After the simulation study, silt fences were installed at the base of

each plot below the erosion barrier. Sediment yields from natural rainfall were measured for post-fire years

one, two, and three. 

Plot size(s): Hillslope plots were 200 to 350 ft2 (20 to 30 m

2

) with a single erosion barrier at the base of each

treated plot.

Generalized results:

The LEBs and straw wattles lower values for total runoff, and all three erosion barrier treatments had lower

values for peak flow rates; however, only the straw wattles significantly reduced sediment yields compared to

the controls. In the subsequent three years,sediment yieldsfrom natural rainfall were measured, and there was

no treatment effect associated with 10 sediment-producing rain events. In addition, sediment yields increased

with increasing total rainfall and rainfall intensity. The erosion barrier treatment effectiveness measured during low intensity simulated rainfall (even with added inflow) was not evident during higher intensity summer

storms typical of western Montana (Robichaud and others 2008a).

Table AB-3. Results from erosion barrier study following the 2000 Valley Complex Fires. Mean rainfall amount, maximum 10-min 

intensity (I10), and event sediment yields are reported for both the simulation study and the natural rainfall study. Mean percent 

difference in sediment yield between the control and the treated plots are reported for each year. Time since fire codes: 

FY = year of the fire; PFy1 = 1 year after the fire; PFy2 = 2 years after the fire; and PFy3 = 3 years after the fire (Robichaud 

and others 2008a).

Time 

since 

fire

------------------------------------Sediment yields--------------------------------

-----------------Rainfall amount-----------------

(inch [mm])

Control

(ton ac–1 [Mg ha–1])

Treated

(ton ac–1 [Mg ha–1])

Difference

(%)

FY

Rain + inflow simulation

Rain: 1.1 [26] for 60 min

Inflow: 13 gal min–1 [48 L min–1] for last 15 min

0.98 [2.2] LEB 0.26 [0.58]

Straw wattle 0.09 [0.21]a

Trench 1.1 [2.5]

74

90

–14b

Event amount

(inch [mm])

I10

(inch h–1

[mm h–1])

Amount

(inch [mm])

Control

(ton ac–1 [Mg ha–1])

Treated

(ton ac–1 [Mg ha–1])

Difference

(%)

PFy1 1.1 [29] 

0.26 [6.6] 

0.62 [16] 

0.87 [22] 

0.15 [3.8]

0.54 [14] 

0.78 [20] 

1.6 [40]c

0.30 [7.6] 

0.54 [14]

Cumulative for

5 events

3.0 [77]

Cumulative for

5 events

13 [29]

Cumulative for

5 events

LEB 6.7 [15]

Straw wattle 12 [27]

Trench 14 [32] 

 

48

7.7

–7.7b

PFy2 0.11 [2.8] 

0.30 [7.6] 

0.29 [7.4]

0.54 [14] 

1.7 [43]c

0.84 [21]

Cumulative for

3 events

0.71 [18]

Cumulative for

3 events

0.36 [0.8]

Cumulative for

3 events

LEB 0.36 [0.8]

Straw wattle 0.49 [1.1]

Trench 0.31 [0.7]

0

–38b

13

PFy3 0.16 [4.1] 

0.22 [5.6]

0.30 [7.6] 

1.2 [31]

Cumulative for

2 events

0.39 [10]

Cumulative for

2 events

0.03 [0.07]

Cumulative for

2 events

LEB 0.08 [0.19]

Straw wattle 0.14 [0.31]

Trench 0.06 [0.14]

–170b

–340b

–100b

a Significant (p = 0.005) reduction in sediment yield compared with the control. b Negative values in the percent difference column indicate that sediment yields were larger for the treated plots than for the control plots.

c 2- to 5-yr return period for 10-min duration (Miller and others 1973).
42 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study IV. A multi-year, multi-site study of the effectiveness of LEBs for reducing post-fire runoff and sediment 

yields (Robichaud and others 2008b)

Overall study design: Between 1998 and 2002,six paired watershed sites were established following six wildfiresto measure the effectiveness of LEBsin reducing post-fire runoff and erosion. In each location, two small,

matched watersheds were selected, and each had a sheet metal headwall with an overflow weir installed at the

base outlet. One watershed was treated with LEBs and one was left untreated as the control. Event runoff and

sediment yields were measured at the base outlet over several post-fire years (Robichaud and others 2008b). 

Plot size(s): Paired watersheds ranged from 2.5 to 25 ac (1 to 10 ha).

Factors that impacted study design and/or results: Results from each of the six sites are reported separately

below.

Study IV—Site 1 

Fire: 1998 North 25 Mile Fire

Location: North-central Washington

Site specific design: Mean slopes for the watersheds were 39 percent on the treated and 50 percent on the

control. LEBs were installed at a rate of 19 ac

–1 (46 ha–1) and had an estimated 2.2 ton ac–1 (5.0 Mg ha–1) total

sediment storage capacity.

Table AB-4. Results from LEB effectiveness study following the 1998 North 25 Mile Fire. Event rainfall amount, maximum 

10-min intensity (I10), runoff, peak flow, and sediment yields are reported for rainfall events that resulted in runoff 

and/or sediment. Data for large events (I10 ≥ 2-year return period) are in bold type and the return period is shown as 

a subscript. Mean percent difference in sediment yield between the control (C) and the treated (T) plots are reported 

for each event. --- indicates that no rainfall events resulted in measurable runoff or sediment in that year. Time since 

fire codes: PFy1 = 1 year after the fire; PFy2 = 2 years after the fire; PFy3 = 3 years after the fire; and PFy4 = 4 years 

after the fire (Robichaud and others 2008b).

-----------Rainfall----------

Event 

amount

--------Peak flow-------

Time 

since 

fire

I10 --------Runoff--------- (X 10–2 ft3

s–1ac–1 -------------------Sediment yield---------------

(inch 

[mm])

(inch h–1

[mm h–1])

(inch [mm]) [m3

s–1km–2]) (ton ac–1 [Mg ha–1]) Difference

C T C T C T (%)

PFy1 0.23 [5.8]

0.14 [3.6]

0.43 [11]

0.52 [13]

0.63 [16]

0.75 [19]

1.2 [31]

0.31 [8.0]

 0 [0]

 0 [0]

0.01 [0.3]

0.05 [1.2]

Not

measured

0 [0]

0 [0]

0 [0]

0.3[0.02]

Not

measured

0 [0]

0 [0]

0.20 [0.45]

0.08 [0.19]

0.14 [0.31]

0.33 [0.74]

0.06 [0.13]

0 [0]

–100a

–100a

71

100

PFy2 --- --- --- --- --- --- --- --- ---

PFy3 --- --- --- --- --- --- --- --- ---

PFy4 0.99 [25] 1.6 [40]10-25 0 [0] Not

measured 0 [0] Notmeasured 0.08 [0.17] 0 [0] 100

a Negative values in the percent difference column indicate that sediment yields were larger for the treated plots than for the control plots.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 43

Study IV—Site 2 

Fire: 1999 Mixing Fire

Location: Southern California

Site specific design: Mean slopes for the watersheds were 24 percent on the treated and 19 percent on the

control. LEBs were installed at a rate of 53 ac

–1 (131 ha–1) and had an estimated 31 ton ac–1 (70 Mg ha–1) total

sediment storage capacity.

Table AB-5. Results from LEB effectiveness study following the 1999 Mixing Fire. Event rainfall amount, maximum 10-min intensity (I10), runoff, 

peakflow, and sediment yields are reported for rainfall events that resulted in runoff and/or sediment. Data for large events (I10 ≥ 2-year 

return period) are in bold type and the return periods shown as a subscript. Mean percent difference in sediment yield between the control 

(C) and the treated (T) plots are reported for each event. n.d. means that no data was obtained. --- indicates that no rainfall events resulted 

in measurable runoff or sediment in that year. + indicates that the event sediment yield was added to next event sediment yield. Time since 

fire codes: PFy1 = 1 year after the fire; PFy2 = 2 years after the fire; ...; and PFy6 = 6 years after the fire (Robichaud and others 2008b).

-----------Rainfall----------

Event 

amount

----------Peak flow---------

Time 

since 

fire

I10 ---------Runoff------------ (X 10–2 ft3

s

–1ac–1 ----------------------Sediment yield----------------------

(inch

[mm])

(inch h–1

[mm h–1])

(inch [mm]) [m3

s

–1km–2]) (ton ac–1 [Mg ha–1]) Difference

C T C T C T (%)

PFy1

0.67 [17]

0.55 [14]

0.66 [17]

0.59 [15]

0.56 [14]

0.87 [22]

0.48 [12]

0.56 [14]

0.57 [14]

0.73 [19]

0.35 [9]

0.35 [9]

0.12 [3]

0.43 [11]

0.31 [8]

0.43 [11]

0.94 [24]

0.71 [18]

0.67 [17]

0.35 [9]

0 [0]

0 [0]

0 [0]

0 [0]

0.004 [0.1]

n.d.

n.d.

n.d.

n.d.

n.d.

0.02 [0.4]

0.004 [0.1]

0.01 [0.2]

0.004 [0.1]

0.004 [0.1]

0.004 [0.1]

n.d.

0.004 [0.1]

0.004 [0.1]

0.004 [0.1]

0 [0]

0 [0]

0 [0]

0 [0]

0 [0]

n.d.

n.d.

n.d.

n.d.

n.d.

4.3 [0.3]

1.4 [0.1]

1.4 [0.1]

2.9 [0.2]

1.4 [0.1]

0 [0]

n.d.

1.4 [0.1]

1.4 [0.1]

1.4 [0.1]

0 [0]

+

0 [0]

0 [0]

0 [0]

0.004 [0.01]

0 [0]

0 [0]

0.004 [0.01]

0 [0]

0.009 [0.02]

+

0 [0]

0.054 [0.12]

0.004 [0.01]

0.025 [0.06]

0.040 [0.09]

0.025 [0.06]

0.031 [0.07]

0.004 [0.01]

–100a

 0

–100a

–100a

–500a

–100a

–100a

–600a

–100a

PFy2

0.54 [14]

0.61 [16]

0.48 [12]

0.50 [13]

0.61 [16]

0.43 [11]

0.43 [11]

0.24 [6]

0.31 [8]

1.5 [38]

n.d.

n.d.

n.d.

0.02 [0.6]

0.01 [0.3]

0.004 [0.1]

0.004 [0.1]

0.004 [0.1]

0 [0]

n.d.

n.d.

n.d.

n.d.

0 [0]

1.4 [0.1]

1.4 [0.1]

0 [0]

0 [0]

0 [0]

n.d.

+

0.004 [0.01]

+

0 [0]

0.60 [1.3]

+

0.004 [0.01]

+

0.005 [0.01]

0.025 [0.06]

 0

–100a

 95

PFy3 0.87 [22] 0.83 [21] 0.01 [0.3] n.d. 5.7 [0.4] n.d. 0 [0] 0 [0] 0

PFy4 2.85 [72] 0.63 [16] 0.02 [0.6] n.d. 1.4 [0.1] n.d. 0 [0] 0 [0] 0

PFy5

1.43 [36]

0.71 [18]

2.62 [66]

4.01 [102]

1.67 [43]

0.43 [11]

0.43 [11]

2.95 [75]5-10

0.83 [21]

0.47 [12]

0.004 [0.1]

0 [0]

0.04 [1.0]

0.02 [0.6]

0.004 [0.1]

n.d.

n.d.

0.06 [1.6]

0.02 [0.5]

0.01 [0.3]

0 [0]

0 [0]

16 [1.1]

1.4 [0.1]

0 [0]

n.d.

n.d.

13 [0.9]

0 [0]

0 [0]

0 [0]

0 [0]

+

0.20 [0.44]

0 [0]

0 [0]

0 [0]

+

0.022 [0.05]

0 [0]

 0

 0

 89

 0

PFy6 0.28 [7.1]

3.9 [100]

0.31 [8]

0.67 [17]

0.004 [0.1]

0.03 [0.7]

0.004 [0.1]

0.03 [0.8]

0 [0]

1.4 [0.1]

0 [0]

0 [0]

0 [0]

0.33 [0.73]

0 [0]

0 [0]

 0

 100

a Negative values in the percent difference column indicate that sediment yields were larger for the treated plots than for the control plots.
44 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study IV—Site 3 

Fire: 2000 Valley Complex Fires

Location: Western Montana

Site specific design: Mean slopes for the watersheds were 39 percent on the treated and 46 percent on the

control. LEBs were installed at a rate of 48 ac

–1 (119 ha–1) and had an estimated 33 ton ac–1 (73 Mg ha–1) total

sediment storage capacity.

Table AB-6. Results from LEB effectiveness study following the 2000 Valley Complex Fires. Event rainfall amount, maximum 10-min intensity 

(I10), runoff, peakflow, and sediment yields are reported for rainfall events that resulted in runoff and/or sediment. Data for large events 

(I10 ≥ 2-year return period) are in bold type and the return periods shown as a subscript. Mean percent difference in sediment yield between 

the control (C) and the treated (T) plots are reported for each event. n.d. means that no data was obtained. --- indicates that no rainfall 

events resulted in measurable runoff or sediment in that year. + indicates that the event sediment yield was added to next event sediment 

yield. Time since fire codes: PFy1 = 1 year after the fire; PFy2 = 2 years after the fire; ...; and PFy6 = 6 years after the fire (Robichaud and 

others 2008b).

-----------Rainfall----------

Event 

amount

--------Peak flow-------

Time 

since 

fire

I10 -----------Runoff------------- (X 10–2 ft3

s–1ac–1 ------------------------Sediment yield----------------------

(inch 

[mm])

(inch h–1

[mm h–1])

(inch [mm]) [m3

s

–1km–2]) (ton ac–1 [Mg ha–1]) Difference

C T C T C T (%)

PFy1 0.29 [7]

0.35 [9]

0.39 [10]

1.2 [30]

1.7 [42]5

1.3 [32]2

0 [0]

0 [0]

0 [0]

0 [0]

0.004 [0.1]

0.004 [0.1]

0 [0]

2.9 [0.2]

1.4 [0.1]

0 [0]

1.4 [0.1]

1.4 [0.1]

0.36 [0.08]

+

0.25 [0.56]

0 [0]

+

0.067 [0.15]

100

73

PFy2 0.53 [14]

0.93 [24]

0.50 [13]

0.51 [13]

2.3 [59]25

1.3 [32]2

0.06 [1.5]

0.01 [0.3]

0.01 [0.2]

0 [0]

0.004 [0.1]

0.01 [0.2]

0 [0]

2.9 [0.2]

4.3 [0.3]

0 [0]

2.9 [0.2]

2.9 [0.2]

0.05 [0.11]

0.17 [0.38]

0.20 [0.44]

0.0 [0.0]

0.15 [0.33]

0.067 [0.15]

100

11

65

PFy3 0.04 [1.1]a 0.20 [5]a 0.22 [5.7]a 0 [0]a 0 [0]a 0 [0]a 0.040 [0.09]a 0 [0]a 100

PFy4 --- --- --- --- --- --- --- --- ---

PFy5 --- --- --- --- --- --- --- --- ---

PFy6 0.74 [19]a 0.47 [12]a 0.10 [2.5]a 0.004 [0.1]a 0 [0]a 0 [0]a 0.054 [0.12]a 0 [0]a 100

a The runoff and sediment produced by this event were caused by snowmelt.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 45

Study IV—Site 4 

Fire: 2001 Fridley Fire

Location: Southern Montana

Site specific design: Mean slopes for the watersheds were 37 percent on the treated and 43 percent on the

control. LEBs were installed at a rate of 28 ac

–1 (70 ha–1) and had an estimated 21 ton ac–1 (48 Mg ha–1) total

sediment storage capacity.

Table AB-7. Results from LEB effectiveness study following the 2001 Fridley Fire. Event rainfall amount, maximum 10-min intensity (I10), runoff, 

peak flow, and sediment yields are reported for rainfall events that resulted in runoff and/or sediment. Data for large events (I10 ≥ 2-year 

return period) are in bold type and the return periods shown as a subscript. Mean percent difference in sediment yield between the control 

(C) and the treated (T) plots are reported for each event. n.d. means that no data was obtained. --- indicates that no rainfall events resulted 

in measurable runoff or sediment in that year. + indicates that the event sediment yield was added to next event sediment yield. Time 

since fire codes: PFy1 = 1 year after the fire; PFy2 = 2 years after the fire; PFy3 = 3 years after the fire; and PFy4 = 4 years after the fire 

(Robichaud and others 2008b).

---------Rainfall--------

Event 

amount

--------Peak flow-------

Time 

since 

fire

I10 --------Runoff--------- (X 10–2 ft3

s

–1ac–1 ----------------------Sediment yield-------------------

(inch

[mm])

(inch h–1

[mm h–1])

(inch [mm]) [m3

s–1km–2]) (ton ac–1 [Mg ha–1]) Difference

C T C T C T (%)

PFy1 0.73 [19]

0.42 [11]

0.57 [15]

0.56 [14]

0.81 [21]

0.91 [23]

1.3 [34]

2.2 [55]5

1.9 [47]2-5

1.8 [45]5

0 [0]

0 [0]

0.01 [0.3]

n.d.

n.d.

0.004 [0.1]

0.004 [0.1]

0.01 [0.2]

n.d.

n.d.

0 [0]

0 [0]

7.1 [0.5]

2.9 [0.2]

0 [0]

1.4 [0.1]

1.4 [0.1]

5.7 [0.4]

n.d.

n.d.

0 [0]

0 [0]

+

+

3.0 [6.7]

0.054 [0.12]

0.080 [0.18]

+

+

2.6 [5.8]

–100a

–100a

13

PFy2 0.19 [4.8]b 0.12 [3.0]b 0.19 [4.7]b 0.01 [0.3]b 4.3 [0.3]b 5.7 [0.4]b 0.13 [0.29]b 0.071 [0.16]b 45

PFy3 --- --- --- --- --- --- --- --- ---

PFy4 0.28 [7.1]

1.10 [27]

0.28 [7.1]

1.10 [27]

0.004 [0.1]

0.004 [0.1]

0 [0]

0 [0]

n.d.

n.d.

0 [0]

0 [0]

0.004 [0.01]

0.004 [0.01]

0.004 [0.01] 

0 [0]

0

100

a Negative values in the percent difference column indicate that sediment yields were larger for the treated plots than for the control plots.

b The runoff and sediment produced by this event were caused by snowmelt.
46 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study IV—Site 5 

Fire: 2002 Hayman Fire

Location: Central Colorado

Site specific design: Mean slopes for the watersheds were 27 percent on the treated and 33 percent on the

control. LEBs were installed at a rate of 45 ac

–1 (110 ha–1) and had an estimated 31 ton ac–1 (69 Mg ha–1) total

sediment storage capacity.

Table AB-8. Results from LEB effectiveness study following the 2002 Hayman Fire. Event rainfall amount, maximum 10-min intensity (I10), runoff, 

peak flow, and sediment yields are reported for rainfall events that resulted in runoff and/or sediment. Mean percent difference in sediment 

yield between the control (C) and the treated (T) plots are reported for each event. n.d. means that no data was obtained. --- indicates that 

no rainfall events resulted in measurable runoff or sediment in that year. + indicates that the event sediment yield was added to next event 

sediment yield. Time since fire codes: FY = year of the fire; PFy1 = 1 year after the fire; and PFy2 = 2 years after the fire (Robichaud and 

others 2008b).

----------Rainfall---------

Event 

amount

--------Peak flow-------

Time 

since 

fire

I10 --------Runoff--------- (X 10–2 ft3

s–1ac–1 --------------------Sediment yield----------------

(inch

[mm])

(inch h–1

[mm h–1])

(inch [mm]) [m3

s–1km–2]) (ton ac–1 [Mg ha–1]) Difference

C T C T C T (%)

FY 1.2 [31] 0.35 [9.0] 0.08 [2.1] 0 [0] 34 [2.4] 0 [0] 0.33 [0.74] 0.031 [0.07] 91

PFy1 0.18 [4.6]

0.17 [4.3]

0.71 [18]

1.1 [29]

0.51 [13]

0.91 [23]

2.0 [52]

0.91 [23]

0 [0]

0 [0]

0.34 [8.6]

0.21 [5.4]

0 [0]

0 [0]

0.21 [5.3]

0.07 [1.7]

0 [0]

0 [0]

71 [5.0]

53 [3.7]

0 [0]

0 [0]

71 [5.0]

37 [2.6]

0.004 [0.01]

0 [0]

8.8 [20]

2.0 [4.6]

0 [0]

0.13 [0.03]

4.2 [9.4]

0.89 [2.0]

100

–100a

52

38

PFy2 0.16[4.1]

0.46 [12]

0.41 [10]

0.35 [9.0]

0.27[6.9]

0.31 [8.0]

0.46 [12]

0.35 [9.0]

0.46 [12]]

0.59 [15]

0.35[9.0]

0.67 [17]

0.39 [10]

0.63 [16]

0.51 [13]

1.1 [27]

0.83 [21]

0.47 [12]

0 [0]

0 [0]

0.03 [0.8]

0 [0]

0.02 [0.4]

0.004 [0.1]

0.03 [0.8]

0.01 [0.2]

0 [0]

0 [0]

0 [0]

0.02 [0.5]

0 [0]

0.004 [0.1]

0 [0]

0.03 [0.8]

0.004 [0.1]

0 [0]

0 [0]

0 [0]

37 [2.6]

0 [0]

36 [2.5]

5.7 [0.4]

34 [2.4]

5.7 [0.4]

0 [0]

0 [0]

0 [0]

31 [2.2]

0 [0]

2.9 [0.2]

0 [0]

27 [1.9]

1.4 [0.1]

0 [0]

+

+

1.4 [3.1]

0.009 [0.02]

+

0.59 [1.3]

1.0 [2.3]

0.18 [0.41]

0.13 [0.03]

+

+

0.35 [0.78]

0 [0]

+

0.02 [0.04]

0.20 [0.45]

0.04 [0.09]

0 [0]

74

100

3.3

78

78

100

a Negative values in the percent difference column indicate that sediment yields were larger for the treated plots than for the control plots.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 47

Study IV—Site 6 

Fire: 2002 Cannon Fire

Location: East-central California

Site specific design: Mean slopes for the watersheds were 44 percent on the treated and 38 percent on the

control. LEBs were installed at a rate of 36 ac

–1 (90 ha–1) and had an estimated 7.1 ton ac–1 (16 Mg ha–1) total

sediment storage capacity.

Generalized results:

High intensity rainfall (maximum 10-min rainfall intensity [I10] ≥ two-year return period), produced most of

the measured runoff and sediment yields, except in the southern California site where long-duration rain events

produced most of the runoff and erosion. Runoff, peak flows, and sediment yields showed a significant treatment effect for smaller rain events (I10 < two-year return period) where all three response variables were lower

in the treated watersheds than in the control watersheds. However, and perhaps more importantly, there were

no treatment effects for rain events with larger return periods (Robichaud and others 2008b).

Table AB-9. Results from LEB effectiveness study following the 2002 Cannon Fire. Event rainfall amount, maximum 10-min intensity (I10), 

runoff, peak flow, and sediment yields are reported for rainfall events that resulted in runoff and/or sediment. Data for large events 

(I10 ≥ 2-year return period) are in bold type and the return periods shown as a subscript. Mean percent difference in sediment yield 

between the control (C) and the treated (T) plots are reported for each event. --- indicates that no rainfall events resulted in measurable 

runoff or sediment in that year. Time since fire codes: FY = year of the fire; PFy1 = 1 year after the fire; PFy2 = 2 years after the fire; 

PFy3 = 3 years after the fire; and PFy4 = 4 years after the fire (Robichaud and others 2008b).

---------Rainfall--------

Event 

amount

--------Peak flow-------

Time 

since 

fire

I10 --------Runoff--------- (X 10–2 ft3

s–1ac–1 -------------------Sediment yield----------------

(inch

[mm])

(inch h–1

[mm h–1])

(inch [mm]) [m3

s

–1km–2]) (ton ac–1 [Mg ha–1]) Difference

C T C T C T (%)

FY 3.9 [100] 1.1 [29] 0.004 [0.1] 0.004 [0.1] 0 [0] 0 [0] 0.058 [0.13] 0.054 [0.12] 7.7

PFy1 0.77 [20] 0.39 [10] 0 [0] 0 [0] 0 [0] 0 [0] 0.004 [0.01] 0 [0] 100

PFy2 --- --- --- --- --- --- --- --- ---

PFy3 --- --- --- --- --- --- --- --- ---

PFy4 1.2 [30] 5.3 [134]100 0.02 [0.6] 0.04 [0.9] 14 [1.0] 23 [1.6] 4.3 [9.7] 6.8 [15] –158a

a Negative values in the percent difference column indicate that sediment yields were larger for the treated plots than for the control plots.
48 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Appendix C. Mulch Treatment Effectiveness Studies 

(2000 to the present) _______________________________________________

Study I. Effectiveness of straw mulch + seeding treatment to reduce sediment yields following the 2000 Cerro 

Grande Fire in central New Mexico (Dean 2001)

Study design: Six repetitions of three treatments (straw mulch + seeding; straw mulch + seeding + contourfelled LEBs; and untreated control) were installed on 23 to 24 percent slopes that had been burned at high

severity. These sites were monitored for two years.

Plot size(s): The hillslope plots were 200 to 350 ft2 (20 to 30 m

2

) with silt fence sediment traps installed at the

base.

Factors that impacted the study design and/or results: 

Results comparing the straw mulch + seeding to the untreated controls are reported here; results comparing

straw mulch + seeding + contour-felled LEBs treatment to the untreated controls are reported in Appendix

E-Study II (combination studies). The differences in sediment yield between the straw mulch + seeding treatment and the straw mulch + seeding + LEBs treatment were not significant.

Generalized results:

Agricultural straw mulch with seed significantly reduced mean annual sediment yields by 70 percent in the

first post-fire year and 95 percent in the second post-fire year; however, precipitation was below normal during

the two study years (Dean 2001).

Table AC-1. Results from straw mulch plus seeding hillslope treatment following the 2000 Cerro Grande 

Fire. Annual rainfall amount, maximum 10-min intensity (I10), and mean annual sediment yields are 

reported for the year of the fire (FY) and the post-fire year one (PFy1). Difference (%) in mean sediment 

yields between the control and treated plots are reported for both years and were significant at the p<0.05 

level (Dean 2001).

Time 

since 

fire

---------Rainfall---------- -------------------------Sediment yields------------------------

Amount

(inch [mm])

I10

(inch h–1

[mm h–1])

Control 

(ton ac–1 yr –1

[Mg ha–1 yr –1])

Straw mulch + seeding 

(ton ac–1 yr –1

[Mg ha–1 yr –1])

Difference

(%)

FY 2.1 [52] 0.94 [24] 3.7 [8.3] 1.1 [2.5] 70

PFy1 6.1 [156] 3.9 [99] 5.6 [12.6] 0.30 [0.67] 95
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 49

Study II. Effectiveness of straw mulch in reducing erosion following the 2000 Bobcat Fire in central Colorado 

(Wagenbrenner and others 2006)

Study design: Dry straw mulch treatment was hand-placed on hillslopes of stony or gravelly sandy loam with

23 to 54 percent slopes burned at high severity. Silt fence sediment traps were established at the base of paired

swales to compare the sediment yields from treated and untreated areas.

Plot size(s): Paired swales ranged from 0.25 to 1.25 ac (0.1 to 0.5 ha), and each swale included a zero-order

channel formed by convergent hillslopes.

Factors that impacted study design and/or results: In the year of the fire (FY), a large storm compromised

the placement and decomposition of the straw mulch that had been applied. These straw mulch plots remained

in the study; however, new straw mulch plots were established with a paired control. The sediment yields from

the plots installed before the storm are labeled “old,” and the sediment yields from the plots installed after the

storm are labeled “new” (table AC-2). Also, in post-fire year three (PFy3), the two general study areas had

different rainfall. Both rainfall amounts are reported (table AC-2).

Generalized results:

Although straw mulch immediately increased the mean ground cover to nearly 80 percent, it did not reduce

sediment yields in the year of the fire when a large amount of sediment was produced from a single large (5- to

10-year return interval) storm. In post-fire years one, two, and three, there was over 95 percent reduction in

mean sediment yield on the straw mulch plots as compared to the untreated control plots (Wagenbrenner and

others 2006).

Table AC-2. Results from straw mulch study following the 2000 Bobcat Fire. Rainfall amount, maximum 

30-min intensity (I30), and mean annual sediment yields are reported for each of the four years of the 

study. Mean percent difference in sediment yield between the control and the treated plots are reported 

for each year. Time since fire codes: FY = year of the fire; PFy1 = 1 year after the fire; PFy2 = 2 years 

after the fire; and PFy3 = 3 years after the fire (Wagenbrenner and others 2006).

Time 

since 

fire

-----------Rainfall----------- --------------------Sediment yields--------------------

Amount

(inch [mm])

I30

(inch h–1

[mm h–1])

Control

(ton ac–1 yr–1

[Mg ha–1 yr –1])

Straw mulch 

(ton ac–1 yr–1

[Mg ha–1 yr –1])

Difference

(%)

FY 2.4 [60] 1.9 [48] 2.8 [6.2] olda

-1.4 [3.2]

newb-NA

old-48.4

new-NA

PFy1 3.0 [75] 1.1 [29] 4.2 [9.5] old-0.2 [0.5]

new-0.009 [0.02]

old-95.2

new-99.8

PFy2 1.4 [36] 0.67 [17] 0.54 [1.2] old-0.009 [0.02]

new-0.003[0.006]

old-98.3

new-99.5

PFy3 0.67 [17]

4.3 [110]

0.71 [18]

1.4 [35] 0.3 [0.7] old-0.00 [0.001]

new-0.00 [0.000]

old-99.9

new-99.9

a old = sediment yields from plots installed before the large storm that occurred the same year as the fire. b new = sediment yields from plots installed after the large storm that occurred the same year as the fire.
50 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study III. Mulch treatment effectiveness in reducing erosion following the 2002 Hayman Fire in central Colorado 

(Rough 2007)

Study design: Fourrepetitions ofthree mulch treatments—dry straw mulch (StrM), ground-based hydromulch

(GHM), and aerial hydromulch (AHM)—were applied to swales that were paired with an untreated control on

the gravelly sandy loam hillslopes that had burned at high severity. Silt fence sediment traps to hold eroded

sediment from the swales were established at the base of each of the 24 swales.

Plot size(s): Paired swales ranged from 0.25 to 1.25 ac (0.1 to 0.5 ha), and each swale included a zero-order

channel formed by convergent hillslopes.

Factors that impacted study design and/or results: Allmulch treatmentswere placed on burned areasthat had

been aerially seeded. Although the treatments were applied the same year as the fire, sediment-producing rain

events had occurred prior to site installation. No data from 2002, the year of the fire, are included in this study.

Generalized results:

The straw mulch reduced sediment yields by 94 percent in post-fire year one and 90 percent in post-fire year

two as compared to the untreated control swale. In comparison, the aerial hydromulch reduced the sediment

yield by 95 percent in post-fire year one but only 50 percent in post-fire year two as compared to the control.

The hydromulch that was applied from the ground did not significantly reduce sediment yields as compared

to the control plots in either year (Rough 2007).

Table AC-3. Results from straw mulch and hydromulch study following the 2002 Hayman Fire. Rainfall amount, 

maximum 30-min intensity (I30), and mean annual sediment yields are reported for post-fire years one 

(PFy1) and two (PFy2). Mean percent difference in sediment yield between the control and treated plots 

are reported for both years. Treatment codes: StrM = dry straw mulch; GHM = hydromulch-ground application (sprayed on); and AHM = hydromulch-aerial application (applied with aircraft) (Rough 2007).

----------Rainfall---------- -------------------Sediment yield------------------ Time 

since 

fire

Amount 

(inch [mm])

I30

(inch h–1

[mm h–1]) Treatment

Control

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Treated

(ton ac–1 yr –1

[Mg ha–1 yr –1])

Difference

(%)

StrM 5.9 [13.2] 0.33 [0.74] 94

PFy1 6.0 [153] 1.6 [40.4] GHM 4.5 [10.2] 3.8 [8.5] 17

AHM 3.2 [7.2] 0.17 [0.39] 95

StrM 4.9 [11.0] 1.1 [2.5] 90

PFy2 11.9[303] 0.87 [23.2] GHM 3.8 [8.5] 3.1 [6.9] 19

AHM 2.0 [4.5] 1.0 [2.3] 50
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 51

Study IV. Effectiveness of dry barley straw mulch and seeding treatments in reducing erosion following a 1991 

wildfire in northeastern Spain (Badia and Marti 2000)

Study design: Fourrepetitions ofthree treatments(12 plots)—combination ofseed plus dry barley straw mulch

(Mulch + Sd),seed only, and untreated control—were established on two soils(calcareous and gypsiferous) on

steep hillslopes (40 to 49 percent) burned at moderate severity.

Plot size(s): PVC troughs were embedded at the base of each bounded, rectangular hillslope plot (86 ft2 [8 m

2

])

to measure sediment yields.

Factors that impacted study design and/or results: 

•	 Rainfall was not directly reported in this article but was estimated from a bar graph showing monthly totals.

•	 Thisstudyincludedstrawmulchcombinedwithseedandseedonlytreatments.Althoughseedingas ahillslope

stabilization treatment is not covered in this report, table AC-4 does include the reported sediment yields for

the seed only treatment.

Generalized results:

Strawmulch with seeding and seeding alone significantly reduced sediment yields as compared to the untreated

controls on both gypsiferous and calcareous soils in post-fire years one and two. Except for post-fire year one

on gypsiferoussoil, there were no significant differences betweenmean sediment yieldsforseeding with mulch

and seeding alone within each soil type and post-fire year.

Table AC-4. Results from barley straw mulch plus seeding study following a 1991 wildfire in Spain. Annual rainfall amounts have been estimated from a bar graph of monthly amounts. Maximum intensity 

was not reported. Mean annual sediment yields are reported for post-fire years one (PFy1) and two 

(PFy2) by soil type (gypsiferous; calcareous) and treatment (Mulch + Sd = straw mulch plus seed; and 

Seed only). Difference (%) in mean sediment yields between the control and treated plots are reported 

for both years and were significant at the p<0.05 level; differences (%) between treatments were significant only for post-fire year one on gypsiferous soils (Badia and Marti 2000).

-----------Rainfall---------- -------------------------------Sediment yields--------------------------

Time 

since 

fire

Amount 

(inch

[mm])

Intensity

(inch h–1

[mm h–1])

Control

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Treated

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Difference

(%)

PFy1 ~12 [295] Not reported Gypsiferous soil Mulch + Sd 0.19 [0.43] 83

1.14 [2.56] Seed only 0.36 [0.80] 69

Calcareous soil Mulch + Sd 0.18 [0.41] 59

0.45 [1.01] Seed only 0.28 [0.63] 38

PFy2 ~10 [247] Not reported Gypsiferous soil Mulch + Sd 0.63 [1.42] 59

1.6 [3.49] Seed only 0.56 [1.25] 64

Calcareous soil Mulch + Sd 0.32 [0.71] 64

0.87 [1.96] Seed only 0.44 [0.98] 50
52 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study V. Effectiveness of hydromulch treatment in reducing erosion following the 2003 Cedar Fire in southern 

California (Hubbert, unpublished report 2007)

Study design: A total of 54 silt fence plots were installed to monitor treatment effectiveness of hydromulch

applied over 100 percent of the treatment area and hydromulch applied in 100 ft (30 m) wide contourstrips over

50 percent of the hillslope. The treatments were applied on two different parent materials—granite bedrock

and gabbro bedrock. The distribution of the silt fence plots was: 13 gabbro control; 11 gabbro strip hydromulch;

10 granitic control; 10 granitic strip hydromulch; and 10 granitic full hydromulch. (Note: no gabbro full hydromulch plots were included.)

Plot size(s): Planar hillslope plots approximately 100 ft (30 m) long and 16 ft (5 m) wide.

Factors that impacted study design and/or results:

•	 The hydromulch was applied in December 2003, but the silt fence plots were not installed until late January

2004. Thus, the plots were not monitoring sediment yields for the first winter rain events.

•	 Rock cover differed by parent material—23 percent for the gabbro and 3 percent for the granitic.

•	 The actual hydromulch coverage was less than desired. The actual level of soil cover observed for the full

hydromulch treatment was 56 percent and 27 percent for the strip hydromulch treatment.

•	 Sediment yields were not directly reported but were estimated from bar graphs.

Generalized results:

In post-fire year one, the strip hydromulch treatment reduced sediment yields by more than 50 percent,

and the full hydromulch treatment reduced sediment yields by about 75 percent (Hubbert, unpublished

report 2007).

Table AC-5. Results from an aerial hydromulch study following the 2003 Cedar Fire. Rainfall amount and 

sediment yields are reported by treatment and parent material for three series of rainfall events in 

post-fire year one. Treatment codes: Strip HM-gabbro or Strip HM-granitic = hydromulch applied in 

100 ft [30 m] wide contour strips over 50 percent of a burned area with gabbro or granitic parent material; Full HM-granitic = hydromulch applied over 100 percent of a burned area with granitic parent 

material; and Control-gabbro or Control-granitic = untreated control area with gabbro or granitic parent 

material. The sediment yields are estimated from bar graphs in the monitoring report. Mean percent 

difference in sediment yield between the control and treated plots are reported for all three periods. 

(Hubbert, unpublished report 2007). 

Time 

since 

fire

(mo)

Rainfall 

(inch [mm])

(period) Treatment

------------------Sediment yields----------------------

Control

(ton ac–1

[Mg ha–1])

Treated

(ton ac–1

[Mg ha–1])

Difference

(%)

4 5.7 [145]

2 Feb-2 Mar

Strip HM-gabbro 0.6 [1.3] 63

Control-gabbro 1.6 [3.6]

Full HM-granitic 0.4 [0.9] 87

Strip HM-granitic 0.8 [1.8] 74

Control-granitic 3.1 [7.0]

5 0.85 [21.6]

3 Mar-13 Apr

Strip HM-gabbro 1.6 [3.6] 52

Control-gabbro 3.3 [7.4]

Full HM-granitic 0.5 [1.1] 62

Strip HM-granitic 1.0 [2.2] 23

Control-granitic 1.3 [2.9]

6 0.41 [10.4]

14 Apr-16 May

Strip HM-gabbro 0.1 [0.2] 50

Control-gabbro 0.2 [0.4]

Full HM-granitic 0.01 [0.02] 90

Strip HM-granitic 0.05 [0.1] 50

Control-granitic 0.1 [0.2]
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 53

Study VI. Effectiveness of mulch treatment in sediment reduction following the 2002 Indian Fire in central 

Arizona (Riechers and others 2008)

Study design: A single repetition of four treatments (three different mulches and one control) were applied on

matched and adjacent swales that contained zero-order channels with slopes of 30 to 40 percent at the top and

lessthan 10 percent at the toe. The treatments were 1) wood chips made on-site from fire-killed trees and spread

by the wood chipper for 100 percent cover; 2) manufactured pellets consisting of compressed, pulverized rice

straw and a polyacrylamide (PAM)soil flocculant/tackifier, which was hand-dispersed at 50 percent coverage,

resulting in 80 to 90 percent coverage after becoming wet and expanding; 3)rice straw hand-applied at 2 ton ac

–1

(4.5 Mg ha–1); and 4) untreated control. These treatments were compared during three summer rain events.

Plot size(s): Double silt fence sediment traps were installed at the channel outlets of the large matched swales

(0.8 to 1.2 ac [0.3 to 0.5 ha]); each swale included a zero-order channel formed by convergent hillslopes.

Factors that impacted study design and/or results: 

•	 Not all silt fences were installed on catchments prior to the first post-fire rain events: the control and wood

chip swales were installed prior to the July event; the pellet swale was added prior to the August event; and

all four treatments were installed prior to the September event.

•	 The wood chip mulch floated off the slope in heavy overland flows, which decreased the cover by 58 percent

three months after application. The pellets degraded rapidly, causing the cover to decrease by 27 percent in

three months.

Generalized results:

The wood chip mulch reduced the sediment yield by about 95 percent compared to the control for the first two

smaller rain events; the effectiveness decreased for the third, high intensity (I10 = 4.6 inch h–1 [117 mm h–1])

rain event when the wood chip mulch reduced sediment yields by less than 68 percent. After the third rain

event, wood chips were observed at the bottom of the slope where they had been deposited after being washed

downslope by overland flows. The compressed pellets were in place for the second, smaller rain event and the

third, high intensity rain event where they reduced sediment yield by 80 percent and 42 percent, respectively,

as compared to the control. The straw mulch plots were in place for the third, high intensity rain event only and

reduced sediment yield by 81 percent compared to the control (Riechers and others 2008).

Table AC-6. Results from a study of three mulches following the 2002 Indian Fire. Rainfall amount, maximum 

10-min intensity (I10), and mean sediment yields are reported for three post-fire erosion-causing summer 

rain events that occurred in the year of the fire (FY). Treatments were wood chips, compressed pellets 

(PAM plus pulverized rice straw), and rice straw. Mean percent difference in sediment yield between the 

control and treated plots are reported for all three events by treatment. “na” indicates that no data were 

available because plots had not yet been established (Riechers and others 2008).

Post-fire 

period 

of 2002

---------Rainfall--------- -------------------------------Sediment yields--------------------------------

Amount

(inch

[mm])

I10

(inch h–1

[mm h–1])

Control

(ton ac-1 per–1

[Mg ha-1 per–1])

Treated

(ton ac–1 per–1

[Mg ha–1 per–1])

Difference 

(%)

13 Jul Wood chips 0.18 [0.42] 93

to 0.36 [9.2] 0.9 [22.9] 2.8 [6.4] Pellets na na

30 Jul Straw na na

31 Jul Wood chips 0 [0] 99.9

to 0.36 [9.1] 1.5 [38.1] 4.8 [10.8] Pellets 0.92 [2.2] 80

14 Aug Straw na na

15 Aug Wood chips > 6.9 [> 15.5]a < 68

to 2.4 [61] 4.6 [117] 21.6 [48.4] Pellets 12.6 [28.2] 42

14 Sep Straw 4.1 [9.1] 81

a Silt fences over-topped, resulting in unmeasured sediment; the amount reported is less than the actual total sediment yield.
54 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study VII. Effectiveness of straw mulch treatment in sediment reduction following the 2002 Fox Creek Fire in 

northwest Montana (Groen and Woods 2008)

Study design: This field-based rainfall simulation study was done on 9 to 17 percent hillslopes of sandy loam

soil that burned at high severity. Three treatments (10 replicates) were tested: 1) seed only, applied at 8 lb ac

–1

(9 kg ha–1); 2) wheat straw mulch, applied at 1 ton ac

–1 (2.24 Mg ha–1); and 3) untreated control.

Plot size(s): Each plot was a small frame of 5.3 ft2 (0.5 m

2

).

Factors that impacted study design and/or results:

•	 Some plot frames were damaged between years of the study so that in post-fire year two (PFy2), the rain

simulations were repeated on two seeded plots, three mulched plots, and four control plots only.

•	 The short flow path within the framed plots used in this study precluded rill erosion processes, and, as a

result, measured sediment yields predominantly are from interrill (sheet wash) erosion only.

Generalized results:

In post-fire year one, the 10 wheatstraw mulched plots had 86 percent lesssediment compared to the 10 control

plots. The small number of usable plots available in post-fire year two did not provide enough data for drawing

conclusions (Groen and Woods 2008).

Table AC-7. Results from field-based, small plot, straw mulch study using rainfall simulation following the 

2002 Fox Creek Fire. The mean value for the simulated rainfall amount and intensity are the same because the intensity was held constant over each hour-long simulation. Mean sediment yields and mean 

percent difference between control and treated plots are reported for each year. Treatments were wheat 

straw mulch (Mulch); seeding (Seed); and untreated (Control). Time since fire codes: PFy1 = 1 year after 

the fire and PFy2 = 2 years after the fire (Groen and Woods 2008).

Time 

since 

fire

n 

(#) Treatment

Rainfall amount

(inch [mm])

Intensity

(inch h–1 [mm h–1])

------------------Sediment yield-------------------

Control 

(ton ac–1

[Mg ha–1])

Treated

(ton ac–1

[Mg ha–1])

Difference

(%)

PFy1

10 Mulch 3.3 [84] 0.5 [1.0] 86

10 Seed 3.2 [82] 2.6 [5.8] 19

10 Control 3.3 [83] 3.2 [7.2]

PFy2

3 Mulch 2.5 [64] 1.0 [2.2] 48

2 Seed 2.7 [68] 0.8 [1.8] 57

4 Control 2.6 [66] 1.9 [4.2]
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 55

Study VIII. Laboratory studies of mulch effectiveness in reducing runoff and/or erosion on forest soils with postfire treatment applications

Lab Study 1. Effectiveness of needle cast in reducing post-fire runoff and erosion (Pannkuk and Robichaud 2003)

Study design: Following wildfires, burned ponderosa pine (PP) and Douglas-fir(DF) needlesthat had fallen to

the ground (needle cast) were collected, and burned surface soils(0 to 4 inch [0 to 10 cm])—volcanic silty loam

from central Washington and granitic sandy loam from Idaho—were excavated for use in laboratory studies.

The needles were placed over the soils in a rectangular plot to create four ground cover amounts (0, 15, 40, and

70 percent). Both rainfall and rainfall with additional surface flow added at the top of the plot were included in

the simulation. One rainfall intensity (1.3 inch h–1 [34 mm h–1]) was combined with one of four concentrated

flow rates (0, 1.5, 2.4, and 3.9 L min–1) over a 25-min simulation: 0 to 10 min = rain only; 10 to 15 min =

1.5 L min–1

; 15 to 20 min = 2.4 L min–1; and 20 to 25 min = 3.9 L min–1. Six replications of the rainfall-inflow

simulation were run with each combination of soil, needles, and cover amounts.

Plot size(s): The plot was a 13- by 3.3-ft (4- by 1-m) rectangular tray placed at a 40 percentslope under the rainfall simulators. Two inflow regulators allowed two trials to be run simultaneously by dividing the plot in half.

Factors that impacted study design and/or results: During some runs on the granitic soil, water leaked out

from under the soil (soil depth = 8 inch [0.2 m]) during the final five-minute inflow period. Therefore, data

from these portions of the runs were not used in the results.

Generalized results:

The short, flat Douglas-fir needles laid directly on the soil for their full lengths and reduced interrill erosion

by 80 percent compared to a 60 percent reduction with ponderosa pine needles. The long, bundled, and curved

ponderosa pine needles tended to form mini-debris dams on the soil surface and reduced rill erosion by 40

percent compared to a 20 percent reduction with Douglas-fir needles (Pannkuk and Robichaud 2003).

Table AC-8. Results from a laboratory study of post-fire needle cast mulch treatment effectiveness. Mean runoff and sediment yields are reported for granitic and volcanic 

soil for the by needle type (PP = ponderosa pine; DF = Douglas-fir), cover amounts 

(%), and inflow rates (L min–1). The symbol “nd” signifies no data. Different letters 

within a column group indicate a significant difference at α = 0.05 (Pannkuk and 

Robichaud 2003).

----------Runoff---------

(L min–1)

---------Sediment yield-------

(g min–1)

Soil type Granitic Volcanic Granitic Volcanic

Needle type PP 1.83a 2.32a 440a 506a

DF 1.75b 2.17b 441a 392b

Mulch cover

(%)

0 1.83a 2.32a 623a 509a

15 1.85a 2.21ab 565b 514a

40 1.82a 2.28ab 425c 464a

70 1.66b 2.1b 146d 309b

Inflow rate 

(L min–1)

0 0.56c 0.28d 62c 18d

1.5 2.05b 1.93c 551b 398c

2.4 2.75a 2.75a 707a 512b

3.9 nd 4.09a nd 868a
56 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Lab Study 2. Effectiveness of manufactured wood strands on reducing runoff and erosion on forest soils (Yanosek

and others 2006)

Study design: Three lengths of wood strands (6.3, 3.1, and 1.6 inch [160, 80, and 40 mm]) were manufactured

from wood waste veneer and combined in two blends (160-40 blend and 160-80 blend) to be tested for effectiveness in reducing erosion. The 160-40 blend contained an equal weight (1:4 piece ratio) of long and short

strands. The 160-80 blend contained an equal weight (1:2 piece ratio) of long and medium strands. The strands

were tested using rainfall and inflow simulations on two soils(coarse-grained gravelly sand and a fine-grained

sandy loam), two slopes (15 and 30 percent), and at four coverage amounts (0, 30, 50, and 70 percent). Four

replications of each combination were run.

Rainfall of 2.0 inch h–1 [50 mm h–1] was applied throughout each run (25 minutestotal). The simulation periods

were: R = rain only; R+1 = rain plus 1 L min–1 concentrated flow rate; and R+4 = rain plus 4 L min–1

concentrated flow rate. The rainfall-inflow simulation periods were applied over the 25 minutes in the following

intervals: R = 0 to 15 min; R+1 = 15 to 20 min; and R+4 = 20 to 25 min.

Plot size(s): The rectangular, steel plot was 13 ft long by 4.1 ft wide by 0.7 ft deep (4.0 m long by 1.2 m wide

by 0.2 m deep).

Factors that impacted study design and/or results: Percent decreases in runoff and sediment yield were not

directly reported in this article but were estimated from line graphs (Yanosek and others 2006: figs. 5 and 6).

Generalized results:

Compared to the untreated controls, wood strand materialsreduced sediment yield by at least 70 percent for all

treatment combinations. In addition, when compared to sediment yield reductions due to agriculturalstraw (as

reported by Burroughs and King 1989), wood strand materials were equally effective on coarse-grained soils

and superior to straw on fine-grained soils (Yanosek and others 2006).

Table AC-9. Results from a laboratory rainfall and inflow simulation study on the effectiveness of manufactured wood strands for mitigating runoff and erosion. Reduction in runoff (%) and sediment yield (%) as compared to bare plots at 30 percent 

slope are reported by soil type (sandy loam and gravelly sand), percent cover (%), 

and simulation period (R = rain only [0 to 15 min]; R+1 = rain plus 1 L min–1 inflow 

[15 to 20 min]; and R+4 = rain plus 4 L min–1 inflow [20 to 25 min]). The percent reductions are estimated from line graphs as reported in Yanosek and others (2006: 

figs. 5 and 6).

Mulch

cover 

(%)

Runoff reduction compared to bare plots (%)

Sandy loam soil Gravelly sand soil

R R+1 R+4 R R+1 R+4

0 0 0 0 0 0 0

30 86 56 36 80 50 25

50 99 83 59 95 75 40

70 <100 95 72 99 83 48

Mulch

cover 

(%)

Sediment reduction compared to bare plots (%) 

Sandy loam soil Gravelly sand soil

R R+1 R+4 R R+1 R+4

0 0 0 0 0 0 0

30 93 79 73 91 81 75

50 <100 92 86 99 94 91

70 <100 99 90 <100 95 94
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 57

Lab Study 3. Efficacy of using wood shreds for reducing runoff and erosion on forest soils (Foltz andCopeland 2009)

Study design: Laboratory rainfall plus inflow simulations were run on two soils to test the effectiveness of

wood shreds produced by a prototype wood shredding device. The tested wood shred mulch, which in actual

use would be produced on-site from locally available materials, was produced from lodgepole pine logging

slash and had a range of lengths from < 1 inch (25 mm) to > 8 inch (200 mm) with similarly variable widths

and thicknesses. The strands were tested using rainfall and inflow simulations on two soils (coarse-grained

gravelly sand and a fine-grained sandy loam) and at four coverage amounts (0, 30, 50, and 70 percent). Three

replications of each combination were run.

Rainfall of 2.0 inch h–1 (50 mm h–1) was applied throughout the entire run (25 minutes total). The simulation

periods were: R = rain only; R+1 = rain plus 1 L min–1 concentrated flow rate; and R+4 = rain plus 4 L min–1

concentrated flow rate. The rainfall-inflow simulation periods were applied over the 25 minutes in the following intervals: R = 0 to 15 min; R+1 = 15 to 20 min; and R+4 = 20 to 25 min.

Plot size(s): The rectangular, steel plot was 13 ft long by 4.1 ft wide by 0.7 ft deep (4.0 m long by 1.2 m wide

by 0.2 m deep) and set at a 30 percent slope.

Generalized results:

Sediment yield reductions ranged from 60 to nearly 100 percent, depending on the soil type (gravelly sand

had greater sediment yields as compared to sandy loam), amount of concentrated flow, and mulch cover

amount (Foltz and Copeland 2009).

Table AC-10. Results from a laboratory rainfall and inflow simulation study on the 

efficacy of wood shreds for mitigating erosion. Mean runoff depths (mm) and 

sediment yields (g) are reported by soil type (sandy loam and gravelly sand), percent 

cover (%), and simulation period (R = rain only [0 to 15 min]; R+1 = rain plus 1 L min–1

inflow [15 to 20 min]; and R+4 = rain plus 4 L min–1 inflow [20 to 25 min]). nr = no 

runoff (Foltz and Copeland 2009).

Mulch

cover 

(%)

Runoff depth (mm) Sandy loam soil Gravelly sand soil

R R+1 R+4 R R+1 R+4

0 3.1 6.3 11 <0.01 1.3 4.2

30 0.2 1.8 5.7 <0.01 0.9 3.7

50 nr 0.4 3.4 nr 0.4 2.7

70 nr <0.01 1.3 nr 0.2 2.6

Mulch

cover 

(%)

Sediment yield (g)

Sandy loam soil Gravelly sand soil

R R+1 R+4 R R+1 R+4

0 780 1310 2330 4 790 3670

30 20 170 480 0.1 160 1470

50 nr 20 190 nr 50 460

70 nr <0.01 50 nr 20 210
58 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Lab Study 4. Effectiveness of wood shreds for reducing runoff and erosion on burned forest soils (Foltz and

Wagenbrenner 2010)

Study design: Laboratory rainfall plus inflow simulations were run on a burned, sandy loam forest soil to

determine the most effective blend of wood shred sizesfor use in post-fire hillslope treatmentsto reduce runoff

and sediment yield. The soil used for the simulations was collected from an area of high soil burn severity six

months after the 2006 Tripod Fire in north-central Washington. The soil was obtained from the top 8 inches(20

cm) and included an ash layer approximately 1.6 inch (4 cm) thick. The wood shreds, produced by a horizontal

grinder from lodgepole pine logging slash, were combined into three size blends containing different amounts

of “fines” (shreds less than 1 inch [2.5 cm] in length). These blends were designated: 1) AS IS—the standard

blend produced by the grinder; 2) MIX—50 percent fewer fines than the AS IS blend; and 3) REDUCE—all

fines removed. The wood strand blends were tested at two coverage amounts (50 and 70 percent). Six replications of each combination were run.

Rainfall of 2.0 inch h–1 [50 mm h–1] was applied throughout the entire run (25 minutes total). The simulation

periods were: R = rain only; R+1 = rain plus 1 L min–1 concentrated flow rate; and R+4 = rain plus 4 L min–1

concentrated flow rate. The rainfall-inflow simulation periods were applied over the 25 minutes in the following intervals: R = 0 to 15 min; R+1 = 15 to 20 min; and R+4 = 20 to 25 min.

Plot size(s): The rectangular, steel plot was 13 ft long by 4.1 ft wide by 0.7 ft deep (4.0 m long by 1.2 m wide

by 0.2 m deep) and set at a 40 percent slope.

Generalized results:

All wood shred blends reduced runoff amounts, but the blend with all fines removed was most effective for

both runoff and sediment yield reduction under conditions of rainfall and rainfall plus concentrated flow. No

significant difference between 50 and 70 percent ground cover was observed (Foltz and Wagenbrenner 2010).

Table AC-11. Results from a laboratory rainfall simulation study to evaluate three size blends of wood shreds 

for mitigating post-fire erosion. Mean runoff depths (mm) and sediment concentrations (g L–1) are reported 

for statistically significant treatment effects (a = 0.05). Results are presented by mulch blend (NONE; AS IS; 

MIX; and REDUCE), cover amount (0, 50, and 70 percent), and simulation period (R = rain only [0 to 15 min]; 

R+1 = rain plus 1 L min–1 inflow [15 to 20 min]; and R+4 = rain plus 4 L min–1 inflow [20 to 25 min]). Each 

combination of mulch blend and cover amount are shown for the rain only (R) period as cover amount 

was a significant factor only during that period. The results of 50 and 70 percent cover are combined for 

the simulation periods that included inflow. Superscript letters denote statistical groupings from pairwise 

comparisons within a simulation period (across a row) for either runoff depth or sediment concentrations 

(Foltz and Wagenbrenner 2010).

-------------Runoff depth------------

(mm)

--------Sediment concentrations---------

(g L–1)

Mulch blend NONE AS IS MIX REDUCE NONE AS IS MIX REDUCE

R

Cover (%)

0 1.5a 130a

50 0.34ab 0.52ab 0.18b 24bc 36b 32b

70 0.29b 0.23b 0.27b 6.9c 21bc 17bc

R+1 3.3a 0.81b 0.95b 0.81b 240a 40b 61b 96b

R+4 8.7a 5.2b 5.5b 4.7b 450a 420a 320ab 270b
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 59

Appendix D. Polyacrylamide (PAM) Treatment Effectiveness Studies 

(2000 to the present) _______________________________________________

Study I. Effectiveness of anionic polyacrylamide (PAM) treatment in reducing sediment yields following the 2002 

Schoonover Fire in central Colorado (Rough 2007)

Study design: Six paired swales were installed per treatment on steep slopes (mean 37 percent) of coarsetextured soil burned at high severity. The anionic, water-soluble PAM was applied in two forms—dry PAM that

consisted ofsmall particlesthat were scattered over the soil (5.0 lb ac

–1 [5.6 kg ha–1]), and wet PAM, which was

a slurry of PAM, water, and aluminum sulfate (10 lb ac

–1 [11 kg ha–1]) that was sprayed on the soil. The study

extended over three years, but dry PAM was used only in the first year (year of the fire [FY]). In subsequent

years, wet PAM was applied on the swales that previously had been treated with dry PAM. Each treated swale

was paired with an untreated control. Thus, the study design was:

•	 Fire year (FY): three swales treated with dry PAM, three swales treated with wet PAM, and each treated

swale paired with one of six untreated control swales

•	 Post-fire year one (PFy1): three dry PAM swales retreated with wet PAM; no further treatment on the other

nine swales

•	 Post-fire year two (PFy2): three retreated swalesfrom PFy1 were treated with wet PAM for the second time;

no further treatment on the other nine swales

Plot size(s): Swales had a mean contributing area of 0.46 ac (0.19 ha) and included zero-order channelsformed

by convergent slopes.

Factors that impacted study design and/or results: 

•	 A separate laboratory test found that PAM preferentially binds to ash over soil.

•	 The rain erosivity explained 58 percent of the variability in sediment yields.

Table AD-1. Results from PAM treatment effectiveness study following the 2002 Schoonover Fire. Rainfall amount, 

maximum 30-min intensity (I30), and mean annual sediment yields are reported for three post-fire years. 

Difference (%) in sediment yield between the control and treated plots are reported, and significant differences 

(p ≤ 0.05) are in bold type. Time since fire codes: FY = year of the fire; PFy1 = 1 year after the fire; and 

PFy2 = 2 years after the fire (Rough 2007).

--------Rainfall-------- -------------------------------------Sediment yields--------------------------------------

Time 

since 

fire

Amount 

(inch [mm])

I30

(inch h–1

[mm h–1])

Control 

(ton ac–1 yr–1

[Mg ha–1 yr–1]) Treatment

Treated 

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Difference

(%)

FY 4.2 [106] 0.64 [16] 1.2 [2.8] Dry PAM 1.0 [2.3] 18

1.6 [3.6] Wet PAM 0.25 [0.55] 85

PFy1 4.8 [122] 0.72 [18] 0.89 [2.0] Wet PAM—applied 

on dry PAM swales

1.2 [2.7] –35a

7.4 [17] Wet PAM—no new 

application

4.5 [10.2] 40

PFy2 9.6 [245] 1.3 [33] 3.7 [8.3] Wet PAM—reapplied 

to dry PAM swales

3.6 [8.1] 2

6.0 [14] Wet PAM—no new 

application

2.6 [5.8] 59

a Negative values in the percent difference column indicate that sediment yields were larger for the treated 

plots than for the control plots.

General results:

The results did not provide a clear indication of PAM effectiveness. PAM treatments reduced sediment yields

during lower,lessintense rainfall periods butwere not effectivewhen rainfall amounts and intensitiesincreased.

Storm erosivity explained 58 percent of the variability in sediment yields (Rough 2007).
60 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study II. Effectiveness of anionic polyacrylamide (PAM) treatment alone and in combination with straw mulch 

in reducing soil erosion following the 2004 Red Bull Fire in Utah (Davidson and others 2009)

Study design: Soil movement was measured using an erosion bridge at three locations within four different

treatment blocks (PAM, straw, PAM + straw, and untreated control) that were created by dividing 21 ac (8 ha)

of the treated area burned at high severity. The four treatment blocks were in gravelly clay loam colluvial soil,

which contains calcareouslime (pH 8.2) and meetsthe recommended percent clay and divalent cation requirements for successful treatment with PAM. The PAM used in this study was granular anionic PAM pelletized

with paper, which is water-activated to provide a time-release of various polyacrylamide polymers of different

molecular weights. Application rate of PAM was 7 lb ac

–1 (8 kg ha–1). The agricultural wheatstraw was applied

at 1.5 ton ac

–1 (3.4 Mg ha–1). The study was done over three years.

Plot size(s): Erosion bridge measurements of soil movement were done midslope at three distinct locations

within each treatment block.

Factors that impacted study design and/or results: 

•	 No rainfall data were reported in this study.

•	 The treatments were established on an area that had been seeded.

•	 The aerial straw application provided, by the authors’ description, uneven coverage.

•	 Net soil loss was presented as a single mean value for all three years so that changes over time could not be

evaluated.

•	 In post-fire year one (PFy1), there was significantly less bare soil on the PAM plus straw (< 45 percent) and

the PAM (< 35 percent) treatment areas than on the straw or the control (both > 65 percent); however, the

impact of the ground cover on soil movement was not evaluated.

General results:

No rainfall data were reported. Soil movement results were reported as a single cumulative figure for all three

years, and the small differences in net soil movement were not significant (Davidson 2009).

Table AD-2. Results from PAM and straw treatment 

effectiveness study following the 2004 Red 

Bull Fire. Mean value for net soil loss (inch [cm]) 

over a three-year post-fire period as estimated 

from a scatter plot. Estimated percent difference 

in soil loss between the control and treated plots 

are reported; however, none of these differences 

are significant at the p < 0.05 level. No rainfall 

data were reported (Davidson and others 2009).

Treatment

Soil

loss

(inch [cm])

Difference

(%)

Control –0.28 [-0.7]

Straw –0.31 [-0.8] 14

PAM –0.12 [-0.3] 57

PAM plus straw –0.16 [-0.4] 43
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010 61

Appendix E. Combination Treatments Effectiveness Studies (2000 to 

present) _________________________________________________________

Study I. Combination treatment effectiveness in reducing erosion following the 2002 Hayman Fire in central 

Colorado (Rough 2007)

Study design: The study involved four repetitions of paired swales on steep slopes with treatments of hand

scarification plus seeding and an untreated control.

Plot size(s): Silt fence sediment traps are located on paired swales that measure approximately 0.25 to 1.25 ac

(0.1 to 0.5 ha), and include zero-order channels formed by convergent slopes.

Factors that impacted the study design: In the year of the fire,sediment producing rain events occurred prior

to site treatment. Data from the year of the fire are not included.

Generalized results:

There was no difference in sediment yields from paired swales that were hand scarified and seeded or the

untreated controls (Rough 2007).

Table AE-1. Results from the combination study following the 2002 Hayman Fire. Annual rainfall 

amount, maximum 30-min intensity (I30), and mean annual sediment yields are reported for 

two treatments (hand scarification plus seeding and untreated controls) in post-fire year one 

(PFy1) and post-fire year two (PFy2). Difference (%) in sediment yield between the control 

and treated plots are reported (Rough 2007).

------------Rainfall------------- ---------------------------Sediment yields-------------------------

Time 

since 

fire

Amount 

(inch [mm])

I30

(inch h–1

[mm h–1])

Control 

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Scarification and 

seeding 

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Difference

(%)

PFy1 6.0 [153] 1.6 [40.4] 4.3 [9.7] 4.0 [8.9] 7

PFy2 11.9 [303] 0.87 [23.2] 3.2 [7.1] 2.7 [6.0] 15
62 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-240. 2010

Study II. Effectiveness of treatment combinations to reduce sediment yields following the 2000 Cerro Grande 

Fire in central New Mexico (Dean 2001)

Study design: Six repetitions of three treatments (straw mulch + seeding; straw mulch + seeding + contourfelled LEBs; and untreated control) were installed on 23 to 24 percent slopes that had been burned at high

severity. These sites were monitored for two years.

Plot size(s): The hillslope plots were 200 to 350 ft2 [20 to 30 m

2

] with silt fence sediment traps installed at the

base.

Factors that impacted the study design and results: 

•	Precipitation was below normal during the two study years.

•	Results comparing the straw mulch + seeding treatment to the controls are reported in Appendix C-Study I.

•	The differences in sediment yield between the straw mulch + seeding treatment and the straw mulch + seeding + LEB treatment were not significant.

Generalized results:

A combination of contour-felled LEBs, straw mulch, and seeding significantly (p < 0.05) reduced sediment

yieldsfrom hillslope plots by 77 percent in the year of the fire and by 96 percent in post-fire year one. The LEBs

added no additional erosionmitigation overthe strawmulch and seeding treatment, which reducedmean annual

sediment yields by 70 percent in the first post-fire year and 95 percent in the second post-fire year (Dean 2001).

Table AE-2. Results from combined hillslope treatments following the 2000 Cerro Grande Fire. Annual rainfall amount, maximum 10-min intensity (I10), and mean annual sediment yields are reported by treatment 

(straw mulch + seeding + LEBs and untreated controls) for the year of the fire (FY) and the post-fire year 

one (PFy1). Difference (%) in mean sediment yields between the control and treated plots are reported 

for both years and are significant at the p < 0.05 level (Dean 2001).

-------------Rainfall-------------- ----------------------------------Sediment yields-------------------------------

Time 

since 

fire

Amount 

(inch [mm])

I10

(inch h–1

[mm h–1])

Control 

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Straw mulch + 

seeding + LEBs 

(ton ac–1 yr–1

[Mg ha–1 yr–1])

Difference

(%)

FY 2.1 [52] 0.94 [24] 3.7 [8.3] 0.84 [1.9] 77

PFy1 6.1 [156] 3.9 [99] 5.6 [12.6] 0.21 [0.47] 96



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