Field Guide for Mapping Post-Fire 

Soil Burn Severity

Annette Parsons, Peter R. Robichaud, Sarah A. Lewis, 

Carolyn Napper, and Jess T. Clark

United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical Report 

RMRS-GTR-243

October 2010
Parson, Annette; Robichaud, Peter R.; Lewis, Sarah A.; Napper, Carolyn; Clark, Jess T. 2010. Field guide for 

mapping post-fire soil burn severity. Gen. Tech. Rep. RMRS-GTR-243. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 49 p.

Abstract

Following wildfires in the United States, the U.S. Department of Agriculture and U.S. Department of the 

Interior mobilize Burned Area Emergency Response (BAER) teams to assess immediate post-fire watershed 

conditions. BAER teams must determine threats from flooding, soil erosion, and instability. Developing a postfire soil burn severity map is an important first step in the rapid assessment process. It enables BAER teams to 

prioritize field reviews and locate burned areas that may pose a risk to critical values within or downstream of 

the burned area. By helping to identify indicators of soil conditions that differentiate soil burn severity classes, 

this field guide will help BAER teams to consistently interpret, field validate, and map soil burn severity.

Keywords: BAER, photo series, post-fire mapping, post-fire rehabilitation, remote sensing

Authors

Annette Parsons is a retired Soil Scientist/GIS Specialist/BAER Liaison with the Remote Sensing Applications Center, U.S. Department of Agriculture, Forest Service in Salt Lake City, Utah. She develops assessment 

procedures used in the post-fire environment.

Peter R. Robichaud is a Research Engineer in the Air, Water, and Aquatic Environment Science Program 

located at the Rocky Mountain Research Station’s Forestry Science Laboratory in Moscow, Idaho. He develops 

and implements protocols for measuring and predicting post-fire runoff and erosion.

Sarah A. Lewis is a Civil Engineer in the Air, Water, and Aquatic Environment Science Program located at the 

Rocky Mountain Research Station’s Forestry Science Laboratory in Moscow, Idaho. She develops processes 

and tools for applying remote sensing technology to the post-fire environment.

Carolyn Napper is a Soil Scientist with the San Dimas Technology and Development Center, U.S. Department of Agriculture, Forest Service in San Dimas, California. She is a BAER Team Leader.

Jess T. Clark is a Remote Sensing Analyst and is under contract with the Remote Sensing Applications 

Center, U.S. Department of Agriculture, Forest Service in Salt Lake City, Utah. He provides remote sensing 

imagery for post-fire assessments.

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Contents

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

Issue and Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Terminology and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

The Role of Remote Sensing and GIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Burned Area Reflectance Classification (BARC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Creation of the BARC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Using the BARC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Other Derived Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Assessment Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Soils Assessment for Low, Moderate, and High Soil Burn Severity Classes . . . . . . . . . . . . . . . 9

Soil Burn Severity Classes and Vegetation Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Severity Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Soil Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Water Repellency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Soil Conditions Photo Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

A. Ground Cover: Amount and Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

B. Ash Color and Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

C. Soil Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

D. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

E. Soil Water Repellency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Pre-Fire Vegetation Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Vegetation Considerations Photo Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

A. Low Density Chaparral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

B. High Density Chaparral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

C. Low Density Mixed Conifer Forest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

D. High Density Mixed Conifer Forest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

E. Low Density Sagebrush/Grassland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

F. High Density Sagebrush/Grassland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Use of the Soil Burn Severity Map in Post-Fire Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Using the Soil Burn Severity Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Common Post-Fire Hydrology and Erosion Prediction Models . . . . . . . . . . . . . . . . . . . . . 31

Displaying Surface Runoff Potential on Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Displaying Erosion Potential on Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Other Uses of a Soil Burn Severity Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Conclusion and Management Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Appendix A—How to Map Soil Burn Severity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Appendix B—Soil Burn Severity Field Data Sheet and Key . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Appendix C—Using a Mini-Disk Infiltrometer to Assess Post-Wildfire Soil 

Water Repellency and Reduced Infiltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Appendix D—Example of the Soil Burn Severity Mapping Process, 2006 Derby Fire . . . . . 45

Appendix E—Summary of Soil Burn Severity Class Factors . . . . . . . . . . . . . . . . . . . . . . . . . 49

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 1

Introduction

Issue and Background

Post-fire assessments are generally conducted

by U.S. Department of Agriculture (USDA)

Forest Service or U.S. Department of the Interior (DOI) Burned Area Emergency Response

(BAER) teams after large wildfires. A BAER

team’s primary objective is to rapidly identify

post-fire effects and determine whether the

wildfire has created unacceptable risk to human

life and safety, property, and critical natural or

culturalresources. TheBAERteammaymanage

riskbyrecommendingtreatmentsforland, channel, road, and trail stabilization and for public

safety (Calkin and others 2007; USDOI BLM

2007;Napper2006;USDAForestService2004).

A map that reflects the fire’s effects on the

ground surface and soil condition is needed in

order to rapidly assess fire effects, identify potential areasof concern, andprioritize initialfield

reconnaissance. Thus, it isimportant to develop

a soil burn severity map as quickly as possible

during the initial post-fire assessment phase. 

This map identifies the fire-induced changes

in soil and ground surface properties that may

affect infiltration, runoff, and erosion potential

(Parsons 2002). It also enables BAER teams to

achieve their primary objective of identifying

areas of unacceptable risk to a critical value and

where rehabilitation treatments may be most

effective (Robichaud and others 2008b; Calkin

and others 2007; Robichaud and others 2000).

BAER teams have often struggled with accurately mapping post-fire soil burn severity. This

challenge has grown in recent years as larger

fires affect multiple jurisdictions, agencies,

and landowners. There is a need for consistent

methodologies, assessment tools, and terminology that quickly and accurately identify the

post-fire conditions. In response, BAER teams

are using many geospatial assessment tools to

expedite post-fire soil burn severity assessment. 

However, little standardization of methodology

or terminology has occurred in soil burn severity mapping and field verification. This guide

provides direction to BAER teams to promote

consistency in post-fire soil burn severity mapping. With a field-validated soil burn severity

map, BAER teams can more readily evaluate

secondary wildfire effects, including increased

runoff, erosion, flooding, sedimentation, and

vulnerability to invasive weeds, and can predict

natural revegetation (Calkin and others 2007).

This field guide clarifies concepts, terminology, context, and use of the soil burn severity

map. Field indicators and classification guidelines are alsoprovided foruse inmapping. Using

this field guide will ensure consistency in map

Field Guide For Mapping Post-Fire 

Soil Burn Severity

Annette Parsons, Peter R. Robichaud, Sarah A. Lewis, 

Carolyn Napper, and Jess T. Clark
2 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

products across ecoregions around the United

States. Components of this guide include:

• terminology and definitions,

• the role of remote sensing and geographic

information systems (GIS) in BAER

assessments,

• guidelinesforidentifying soil burn severity

classes in the field,

• discussion on soil burn severity within

general vegetation density models,

• photo series showing representative postfire soil and ground conditions, and

• field data sheetsto assist in data collection

for mapping soil burn severity.

This guide provides a reference for ground

conditions, soil characteristics, and vegetation

density modelsthat most closely match the field

setting. Observationscanbecomparedwiththose

in the tables and photos to make a determination of the soil burn severity classification at a

fieldlocation. Thisguidepresentsrepresentative

conditions only. Actual ground conditions will

vary within the categories.

Terminology and Definitions

Fire effects literature, Incident Management

Teams, and post-fire assessment teams use

various terms to describe post-fire conditions

(Jain and others 2004; Lentile and others 2006). 

Consistently using proper terms will help avoid

confusion and clarify the focus of the BAER

team’s products. See fig. 1 for an example of

a high intensity fire resulting in high soil burn

severity. This illustration depicts a scenario

where surface and ground fuels are abundant(in

other words, high pre-fire vegetation density). 

The correlation between fire intensity and soil

burn severity is not always direct, however,

because aside from the amount of heat generated, duration plays a critical role in fire effects

to soil (DeBano and others 1998; Hartford and

Frandsden 1992). To clarify their meanings and

tominimizeconfusionaboutimplicationsofburn

severity maps, the following terms are defined

(adapted from Scott and Reinhardt 2007):

Char: Visual estimate of soil or vegetation

burn that is essentially the percent ofthe surface

Figure 1. Illustrates the effect of fire intensity on above-ground vegetation and below-ground soil properties. 

Graphic modified by Mike Hankinson, National Park Service.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 3

that has been scorched (blackened). Soil char

is an indicator of potential root damage or soil

heating (Ryan and Noste 1985).

Fire effects: The physical, biological, and

ecological impacts of fire on the environment

(National Wildfire Coordinating Group 1996). 

Two types are often discussed: first-order fire

effects(direct effects ofthe combustion process

on the environment) and second-order fire effects (effects that occur after some time and

are often caused by interaction of fire-caused

stress with other factors).

Fire intensity: The amount of energy or

heat release per unit time or area during the

consumption of organic matter (Keeley 2009). 

Byram (1959) defined the term as “the rate of

energy or heat release per unit time, per unit

length of fire front, regardless of its depth.”

Othermeasures offire intensity include fireline

intensity, reaction intensity, and total fire flux,

all of which refer to the actual burning event

(White and Pickett 1985). Fire intensity is a

real-time burning measurement and does not

directly indicate the effects of the fire on the

vegetation or soil or the subsequent ecosystem

response (Keeley 2009). For example, a high

intensity fire that exhibits extreme fire behavior

(such as high flame length, rapid rate ofspread,

or overstory crown consumption) might result

in low- or moderate-degree effects on the soil

(soil burn severity) due to short heat residence

time. Typical examples are crown fires in forests or shrub or grassland fires. Conversely, a

low intensity fire (smoldering log) can produce

intense heat and can be long duration, resulting in high soil burn severity in the area under

the log, tree root channels, or woody debris

concentration.

Ground cover: Ground cover refersto effective organic cover as it pertains to mitigation

of runoff and erosion and includes litter, duff,

and woody debris. It may also be called “soil

cover” or “organic ground cover.”

Soil burn severity: The affect of a fire on

ground surface characteristics, including char

depth, organic matter loss, altered color and

structure, and reduced infiltration (Lentile and

others 2006;DeBano and others 1998;Ryan and

Noste 1985). The classification of post-fire soil

condition is based on fire-induced changes in

physical and biological soil properties. During

post-fire assessments, there has been an intentional effort to use the term “soil burn severity”

to differentiate post-fire soil properties from

fire effects on vegetation (such as tree mortality) and/or general fire effects on long-term

ecosystem health.

Soil heating: An increase in soil temperature

as a result of heat transfer from the combustion

of surface fuel and smoldering combustion of

organic soil horizons.Because ofthe variability

of fuel consumption, soil heating typically is

non-uniform acrosslandscapes. In many cases,

the highestsoiltemperatures are associatedwith

high fuel consumption and/or complete duff/

forest floor consumption, which are affected

by the duration and intensity of the fire and are

related to the pre-fire fuel moistures. The two

components ofsoil heating that affectsoil burn

severity are maximum temperature achieved

and duration of heating.

Vegetation burn severity: The effect of a

fire on vegetative ecosystem properties, often

defined by the degree of scorch, consumption,

and mortality of vegetation and the projected

or ultimate vegetative recovery (Lentile and

others 2006; Morgan and others 2001). The

vegetation burn severity of a fire depends on the

fire intensity and the degree towhich ecosystem

properties are (or are not) fire resistant. For

example, a fire of exactly the same fireline

intensity might kill thin-barked trees but have

little effect on thick-barked trees, or it may
4 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

root-kill rather than canopy-kill trees, which

would result in greater mortality than initially

observed.

Water repellent soils (water repellency):

Resistant to water penetration; not wettable. 

With fire-induced soil water repellency, soil

particles are coated with hydrophobic compounds. When organic material burns at high

intensity, the hydrophobic organic compounds

often vaporize, and some of the vaporized

compounds move down into the soil. When the

vaporsreach a soil depth where the temperature

is low enough, the hydrophobic compounds

condense and coat the soil particles at that

depth—generally 0.25 to 2 inches (0.5 to 5 cm)

below the surface and frequently only in a thin

(< 1 mm) layer at the immediate soil surface. 

Water repellency is spatially variable across

the landscape and is correlated to soil type,soil

particle size, organic matter content, and depth

of the litter and duff layer on the soil surface

and soil moisture (MacDonald and Huffman

2004; Doerr and others 2009). See Appendix

C for more information on how to measure

water repellency.

The Role of Remote Sensing 

and GIS

The tables and photos in this field guide

(beginning on page 12) are useful for mapping

soil burn severity, whether the mapping is being done entirely by hand or if the mapping

includes the use of remotely-sensed images. 

This mapping does not require remote sensing

or GIS; however, both technologies are commonly used on large wildfires. Depending on

availability of resources, access, size, and time

frame, some fires are mapped fastest by hand. 

For example, a 1000 acre (400 ha) fire with

sufficient access may be a good candidate for

a post-fire assessment done solely via ground

and aerial observations. Waiting for a satellite

overpasses to image a fire may jeopardize a

BAERteam’s ability to complete its assessment

quickly.

For larger and more inaccessible fires, remote

sensing and GIS can greatly improve the speed,

precision, and accuracy of post-fire mapping

efforts. However, soil burn severity mapping

should never be done solely through the use

of remote sensing classifications and without

proper field verification (Parsons 2002; Hudak

and others 2004). Ecosystems and fire behavior

are variable enough that field observations and

refinement ofthe remote sensing classifications

are both necessary. Once the initial image classification has been done, the soil scientist or

otherspecialistmust verify the soil conditionsin

the field before the entire team can use the map.

Burned Area Reflectance 

Classification (BARC)

Since 2002, theUSDAForest ServiceRemote

Sensing Applications Center (RSAC) in Salt

LakeCity, Utah, and the USGS Centerfor Earth

Resources Observation and Science (EROS)

in Sioux Falls, South Dakota, have provided

satellite imagery and derived productstoBAER

teams to help rapidly map soil burn severity on

wildfires (Orlemann and others 2002). Among

the productstypically provided to BAER teams

byRSACandEROS are pre- and post-fire satellite images of the burned area and a preliminary

classification that represent landscape change. 

This product is referred to as the Burned Area

Reflectance Classification (BARC) (Clark and

Bobbe 2006).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 5

Creation of the BARC

The BARC is derived from an image transformation algorithm known as the Normalized

Burn Ratio (NBR). The NBR uses the nearinfrared (NIR) and mid-infrared bands (also

called the short-wave infrared [SWIR] band)

from the Landsatsatellite sensor. The algorithm

is as follows:

NBR = (NIR – SWIR) / (NIR + SWIR)

Healthy,greenvegetationreflectsNIRenergy. 

Conversely,NIRresponsedecreaseswhere there

islittlevegetation. Mid-infraredenergyislargely

reflected by rock and bare soil, meaning that

mid-infrared band values will be very high in

bare, rocky areas with little vegetation and low

in areas of healthy, green vegetation. Imagery

collected over a forest in a pre-fire condition

will have high near-infrared band values and

low mid-infrared band values, while imagery

collected over a forest after a fire will have low

near-infrared band values and highmid-infrared

band values.

Many researchers have used a single-scene

NBR (López-Garcia and Caselles 1991) and a

change detection approach based on the NBR

called the differenced Normalized Burn Ratio

(dNBR) (van Wagtendonk and others 2004) in

burn mapping projects. The dNBR is simply an

image differencing between a pre-fire NBR and

apost-fireNBR,which are ideallyoneyear apart

for vegetation and atmospheric consistency:

dNBR = NBRpre-fire – NBRpost-fire

In general, the dNBR is a useful and accurate

toolfor burn severity mapping (Brewer and others2005;Cocke andothers2005;Miller andYool

2002). Nearly all BARC layers are created from

the dNBR. Other algorithms are occasionally

used simply due to availability (or lack thereof)

of spectral bands in the post-fire satellite or airborne imagery used for the assessment.

Using the BARC

The BARC is not considered a soil burn severity map until it has been field verified and,

if necessary, refined to better represent soil

and ground conditions. The BARC begins as a

continuousrasterGISlayerthatis classified into

four colors that represent the four burn severity

classes: unburned is dark green, low is light

green,moderate isyellow, andhighisred. BARC

values are scaled 0 to 255; low values indicate

the least burned areas, and values increase as

burn severity increases. Some users may find

the BARC, as applied to the delivered product,

to be a good fit for their wildfire. It can be very

accurate in areas of densely forested ecosystems

where variation in vegetation type and density

are minimal. When no edits are needed, as determined by field verification, the BARC may

be renamed the “soil burn severity map.”

Moreoften,however,the thresholds appliedto

the delivered BARC may not be a good fit to the

observedpost-firesoilandgroundconditions. By

nature,satelliteimagesandtheirderivedproducts

suchastheBARCare reflectiveofthevegetative

condition because that is the uppermost layer

or what the satellite “sees.” Adjustments to the

BARC classes are necessary to produce a map

product that is reflective of the soil conditions. 

Plottingthe fieldobservationsofsoil andground

conditions usingGPScoordinates as a data layer

overlaid on theBARCallowsthe userto see how

closely the BARC classes match independent

and unbiased field observations. Many BAER

team members with basic GIS skills find they

can adjust the BARC to quickly create a map

that represents their observed soil and ground

conditions by making simple adjustmentsto the

BARCthresholdvalues. Thisiscalledsystematic

editing–changing the BARC thresholds across

the entire fire. Systematic editing works well in

situationswherevegetationandothersite factors

produce a fairly predictable distribution of soil
6 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

burn severity patterns across the landscape. To

make systematic changes to the BARC in ArcMap(EnvironmentalSystemsResearchInstitute,

Inc. [ESRI], Redlands, CA), team members

can simply open the symbology tab within the

properties of the BARC layer and adjust the

thresholds between the variousseverity classes. 

If, for example, field observations indicate the

BARC (as delivered) overestimates high severity across the entire fire, an analyst can adjust

the breakpoint between moderate (yellow) and

high (red) to include more yellow pixels. Common starting points for BARC thresholds are 0

to 75 (unburned), 76 to 109 (low), 110 to 187

(moderate), and 188 to 255 (high). If the high

severityinthedeliveredBARCisoverestimated,

the user may lower the break between moderate

and high from 188 to 170, for example.

Other situations may require edits to localized areas because the imagery used to create

the BARC may have problems that cause classification confusion. Clouds,snow,smoke from

surrounding fires, or large water bodies within

the burn scar (fig. 2) can create inconsistencies

in theBARC. Theremay also be cases where the

geology-soils-vegetation-topography interactions are socomplexthatsystematic adjustments

do not work well for the entire burned area. In

these instances,BAERteammembers canmake

soil burn severity adjustments through aerial

or ground observations and then integrate those

observations into the BARC using GIS.

Another GIS technique that can be used to

refine the BARC isto create an overlay with the

pre-firevegetationclasses. This canhelpaccount

for pre-fire vegetation densities and types that

Figure 2. Large water bodies within the fire perimeter, like Cheesman Reservoir in the 2002 Hayman Fire 

Landsat imagery (a), confuse the BARC (b) and should be masked out.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 7

can affect the BARC classification. An overlay

of timber sales or cut blocks may also be useful

for changing some areas oftheBARCfromhigh

to moderate or low soil burn severity. In this

case, BAER team members can use GIS layers

and a pre-fire vegetation classification to reclassify areas of high burn severity on the BARC

into whatever is appropriate based on the soil

and ground condition data gathered (Appendix

B). An example BARC mapping exercise of a

mixed conifer/mountain grassland fire that was

editedbyBAERteammembersbasedonpre-fire

vegetation is illustrated in Appendix D.

It is important for BAER team members to

consider the dates of the satellite imagery used

to create the BARC. Though analysts at RSAC

and EROS try to use image pairs (pre- and

post-fire) that match each other well (ideally

one year apart and similar dates), pairs may

sometimes span multiple years. If there have

been management activities on the landscape

between the dates of the imagery used, those

activities may influence the severity mapping

results. For example, logging activities that

occur between the pre- and post-fire images

used to create a BARC will likely be classified

as high severity. The BARC will assume that

the fire in the area of the logging activity was a

stand-replacing event when, in reality, the forest

structure changed due to management activities

prior to the fire event. The BARC assumes all

things are equal on the landscape between preand post-fire imagery with the exception of the

wildfire. BAER teams need to be aware of these

potential misclassifications.

RSAC hosts an annual interagency training

where BAER teams are taught to understand

theBARC,make systematic and localized edits,

and use the edited layer in additional modeling. Training materials and information can be

found at http://www.fs.fed.us/eng/rsac/baer/

training.html.

Other Derived Products

BAER teams are sometimes asked to make an

assessmentofthevegetationconditionfollowing

thewildfire. Inthis case,relatedproductslike the

RapidAssessment ofVegetationCondition after

Wildfire (RAVG)suite containmore appropriate

geospatial layers (www.fs.fed.us/postfirevegcondition). TheRAVG project createsmapsthat

relate vegetation effects such as percent change

in basal area, canopy cover, and vegetation burn

severity. RAVGusuallymapsfireswithin30days

offire containment(specialrequests arepossible

for faster delivery). In addition, the Monitoring

Trends in Burn Severity (MTBS) project can

provide historical fire severity information in

an area that the BAER team is working (www.

mtbs.gov). The MTBS project is a nationwide

effort to map the vegetation burn severity of all

large fires(greaterthan 1000 acres, 400 ha in the

West and 500 acres, 200 ha in the East) between

1984 and present, regardless of vegetation type

or land ownership. MTBS usually maps fires

one year after they burn.

Assessment Guidelines

The BARC can be used to identify and characterize preliminary soil burn severity classes. 

From this initial map, BAER teams can make

a paper copy of the remote sensing image provided or anothermap base,make field visits, and

complete theBAERFieldDataSheet(Appendix

B). Teammembersshouldsystematicallycollect

soil information (ground cover, ash color and

depth, soil structure, condition of roots, and

water repellency) for each soil burn severity

class and record locations of data points on a

map or using a GPS unit. Once team members

get a sense of how the soil burn severity classes

are arrayed on the landscape (Key and Benson

2005), they can begin to compare the BARC to
8 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

the soil and ground condition observations to

determine its accuracy. Ifseveralspecialists are

assisting in the validation process, ensure that

thegroupis calibratedusingthe sameprocedure. 

After compiling assessments from the various

specialists andcomparingthese fieldevaluations

to imagery and map data, the team can develop

a soil burn severity map from the BARC that

is consistent with fire effects science and that

meets the needs of the BAER team in assessing

runoff and erosion potential.

In some cases, remote sensing imagery and

the BARC may not be available to assist in

mapping. This field guide is also appropriate

as a reference for hand mapping. This section

presents a brief description of some important

concepts to keep in mind when mapping either

by hand or with a BARC map and stepsin mapping soil burn severity. More detail can be found

in Appendix A.

The ability to map effectively depends on

the mapper’s ability to examine the burned

landscape, determine relationships ofimportant

contributingfactors,makepredictionsabouthow

and where conditions occur on the landscape,

and create polygons representing those conditions. Concepts such as map unit composition,

purity, scale, and intended use are all important

to understand. These concepts affect how and

where polygons are drawn and what those polygons represent.

One important consideration is minimum

polygon size. In general, a minimum of 40 acres

(16 ha) is appropriate, but it may be as large as

100 or more acres (40 ha or more) on large fires

or as small as 10 acres (4 ha) in areas of critical

values-at-risk. It is also important to determine

the distribution and extent of localized fire effects when creating a soil burn severity map as

they may not represent the majority of the area

mapped and should not disproportionately skew

the soil burn severity classification.

The photos in this guide provide visual reference to what are considered “representative

concepts” of soil burn severity classes in low

and high density vegetation types. These photos

should be used as a guide only–they should

not be viewed as absolute or all-inclusive. 

Professional judgment is necessary when interpreting soil and ground conditions, especially in

moderate density vegetation systems where no

representative photos are provided.

Steps involved in mapping soil burn severity

include:

• Get the big picture. Survey the area to

develop a sense of how “green,” “brown,”

and “black” are distributed in the burned

area. Record notes.

• Gather field information. Spend time on

the ground, take notes, and collect GPS

points.

• Start forming “map unit” concepts. 

Learn how terrain, vegetation, and burn

indicators relate, and describe each map

unit according to observed characteristics.

• Develop a concept of “map unit purity.”

Develop an idea of how homogenous the

soil burn severity classes are and include

descriptions of the classes in the report.

• Focus field time in the “black.” Time

should be spent where the likely problem

areas are, and where the most valuable

information will be gained.

• Draw polygons on a map.Using theBARC,

a post-fire satellite image, or a topo map,

delineate the soil burn severity classes on

a map. Use the ground data notes to help

you decide where lines should go.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 9

Soils Assessment for Low, 

Moderate, and High Soil Burn 

Severity Classes

Soil Burn Severity Classes and 

Vegetation Considerations

Though this document and geospatial tools

such as the BARC are intended to help map

fire effects on soils, the first thing that the field

observer and the remote sensing imagery “see”

is the overlying burned vegetation. Because

soil burn severity is a result of multiple site factors, including weather at time of burning, for

the purposes of the following vegetation type

and density models, we assume that there is a

direct correlation between vegetation density

and amount of ground fuels (Safford and others 2007). More fuels typically cause longer

fire residence time, which may result in greater

impacts to the soil and ground conditions. The

followingmatrix showsthe correlation between

vegetation type, density model, and soil burn

severity (table 1). These are guidelines and are

not necessarily applicable in all fires.

Information about vegetation density and

post-fire vegetation characteristics is useful in

classifyingburnseverity. Likewise, canopychar

and color are often used as ancillary indicators

of overall burn severity but do not necessarily

coincide with soil burn severity. In the following descriptions of low, moderate, and high soil

burn severity, canopy color is included to guide

field stops and initial assessments.

However, to correctly use the soil burn severity map for its intended purpose (predicting

accelerated risk of runoff or erosion), the map

must reflect the fire-induced changes in soil

and ground conditions. The following description of soil burn severity indicators helps users

correctly assess post-fire effects to the soil and

ground conditions.

Table 1. Matrix of soil burn severity and vegetation type and density models.

Soil burn severity classes

Vegetation type Density modela Low Moderate High

Chaparral Sparse Cb U

Medium C C U

High C C U

Forest Sparse C U

Medium C C U

High C C C

Sagebrush Sparse C U

Medium C C U

High C C U

Grass Sparse C

Medium C U

High C C

a Percent canopy cover for sparse, medium, and high density are approximately defined as:

Sparse ≤ 20%; Medium = 20–60%; and High ≥ 60%.

b Key: C = common; U = unlikely (but can occur in some circumstances); Gray cells = not applicable/does 

not occur.
10 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Severity Indicators

Low soil burn severity:Surfaceorganic layers

are not completely consumed and are still recognizable. Structural aggregate stability is not

changed from its unburned condition, and roots

are generally unchanged because the heat pulse

below the soil surface was not great enough to

consume or char any underlying organics. The

ground surface, including any exposed mineral

soil,mayappearbrownorblack(lightlycharred),

and the canopy and understory vegetation will

likely appear “green.”

Moderate soil burn severity: Up to 80

percent of the pre-fire ground cover (litter and

ground fuels) may be consumed but generally

not all of it. Fine roots (~0.1 inch or 0.25 cm diameter)maybescorchedbutarerarelycompletely

consumed over much of the area. The color of

the ashonthe surface isgenerallyblackened with

possible gray patches. There may be potential

for recruitment of effective ground cover from

scorched needles or leaves remaining in the

canopy that will soon fall to the ground. The

prevailing color of the site is often “brown” due

to canopy needle and other vegetation scorch. 

Soil structure is generally unchanged.

High soil burn severity: All or nearly all of

the pre-fire ground cover and surface organic

matter (litter, duff, and fine roots) is generally

consumed, and charringmay be visible on larger

roots. The prevailing color of the site is often

“black” due to extensive charring. Bare soil

or ash is exposed and susceptible to erosion,

and aggregate structure may be less stable. 

White or gray ash (up to several centimeters

in depth) indicates that considerable ground

cover or fuels were consumed. Sometimes very

large tree roots (> 3 inches or 8 cm diameter)

are entirely burned extending from a charred

stump hole. Soilis often gray, orange, orreddish

at the ground surface where large fuels were

concentrated and consumed.

Soil Characteristics

Common changes to the soil include:

• loss of effective ground cover due to

consumption of litter and duff;

• surface color change due to char, ash cover,

or soil oxidation;

• loss of soil structure due to consumption

of soil organic matter;

• consumption of fine roots in the surface

soil horizon; and

• formation of water repellent layers that

reduce infiltration.

The loss of effective ground coveristhe single

most important change that can greatly increase

erosion and runoff. It is important to compare

pre-fire ground cover to post-fire ground cover

to understand how much has changed as a result

of the fire. For example, if ground cover was

sparse prior to the fire,soil burn severity should

not be considered high as there was not enough

fuel to maintain long duration heat to affect the

soil to that degree.

The mineralsoil color can also reflect the soil

burn severity. In low soil burn severity, exposed

mineral soil may appear brown or black. High

soil burn severity soil can be orange or reddish

due to soil oxidation or, more commonly, will

appear grey due to ash cover or an ash/soil mix

at the surface.

Soil structure can change by fire through the

loss ofstructural aggregate stability. Thisis due

toorganicmaterial combustioninthe surface soil

horizon. The combusted organic compounds act

as an adhesive that bind soil particlesinto stable

aggregatesthatresistdetachment. Dependingon

the soil type and the degree of heating, exposed

soils may become powdery, single-grained, or

loose afterintenseheatingandarehighlysusceptible to detachment by wind, water, and gravity.

Root conditioncanalsobeusedtointerpretsoil

heating severity. Fine root loss or charred larger
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 11

roots in the surface soil horizon is the result of

high heat for a sufficient duration.

Ash color and depth are indicative of soil

heating. A thick layer (~3 inches or 8 cm) of

powdery gray or white ash usually results from

complete combustion of litter, duff, and surface

fuels and can indicate severe heating. For reference, it takes approximately 8 inches(22 cm) of

duff(assuming a bulk density of 0.1 g/cubic cm)

to produce 1 inch (2.5 cm) of ash. However, ash

may not always be a reliable indicator because

it is highly mobile by wind and water.

Water Repellency

Increasingburnseverityisoftenincorrectlyassumedtobepositivelycorrelatedwithincreasing

soil water repellency (Lewis and others 2006). 

However, pre-fire soil texture and type, amount

and depth of litter cover, soil moisture, and soil

organic matter as well as the temperature and

residence time of the fire all affect the degree

of soil modification and resulting soil water

repellency (DeBano 2000a; Doerr and others

2000). Coarse-grained soils are more prone to

fire-induced water repellency than fine-grained

soils. Volcanic ash-cap soils, which are finegrained, areusuallynaturallywaterrepellent,but

the degree ofwaterrepellency is often altered by

fire heating (Robichaud and Hungerford 2000;

Doerr and others 2000). Naturally water repellent soils are also frequently (but not always)

found under canopies oftrue fir(Abies spp.) and

underindividualsage (Artemisia spp.)or chaparral shrubs (Ceonothus spp. and others). As the

litter and duff on the soil surface is consumed

in a fire, water repellent conditions are often

created or exacerbated through the formation of

hydrophobic compounds. However, very high

temperatures (> 280 °C) or a long heating time

may preclude the formation of water repellent

soil at the surface. A water repellent layer may

still be formed in the cooler subsurface that

will hinder infiltration and increase runoff and

erosion (DeBano 2000b). A thin layer of water

repellent soil at or near the surface is common

and will generally dissipate more quickly via

bioturbation, gravity, and freeze-thaw cycles

than will a water repellent layer deeper in the

soil profile (Doerr and others 2000). Because

the temperature and duration of forest fires and

soil properties have high spatial variability, the

connection between burn severity and soilwater

repellency is neither universally consistent nor

well defined (Doerr and others 2000). See Appendix C for information on how to measure

waterrepellency (Robichaud and others 2008a).

All of these factors should be considered together while determining the soil burn severity

classification. Not all possible indicators must

be present, but generally, two or more factors of

high severity dominating an area may justify a

classification of high soil burn severity for that

polygon.

The following photo series exemplifies the

soil burn severity descriptions provided above

and includes:

A. Ground Cover: Amount and Condition

B. Ash Color and Depth

C. Soil Structure

D. Roots

E. Soil Water Repellency
12 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Soil Conditions Photo Series

A. Ground Cover: Amount and Condition

Low soil burn severity

Little or no change from pre-fire

status. Less than 50% consumption

of litter, some char. Needles and

leaves mostly intact.

Moderate soil burn severity

Up to 80% consumption of litter

and duff, but generally incomplete. 

Recognizable leaves and needles

remain. Ifmorecompleteconsumption

occurred, a mitigating factor may be

potentialforleaf- or needle-castfrom

scorched canopy to provide ground

cover.

High soil burn severity

Little to no effective ground cover

remaining after fire (less than 20%). 

All or most litter and duff has been

consumed, only ash or bare soil (ash

blown away) remain. Little to no

potential for leaf- or needle-cast.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 13

B. Ash Color and Depth

Low soil burn severity

Ground surface may be black with

recognizable fine fuels (needles, grass,

and leaves) remaining on surface.

Moderate soil burn severity

Thin layer of black to gray ash with

recognizeable litter beneath it. Ash

layer may be patchy as it is highly

moveable bywind andwater. Soil heating

may have been significant; residence

time usually brief. If thicker ash layer

is observed, a mitigating factor may

be leaf- or needle-cast potential from

scorched canopy.

High soil burn severity

Thick, 1- to 3-inch (3- to 6-cm or more)

layer of powdery gray or white ash

covers the ground. Greater than 90%

surface organics consumed; significant

soil heating has occurred;residence time

long. No potentialforleaf- or needle-cast

to provide ground cover.

Localized red (oxidized) soil may

underlie a thick, powdery layer of gray

and white ash–generally found near

a burned out stump or log; indicates

extreme heating.
14 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

C. Soil Structure

Low soil burn severity

St r uct u re u ncha nge d. G ra nula r

agg regates a re not weakened by

consumption of organic matter.

Moderate soil burn severity

Structure slightly or not altered. Some

consumption of organicmatterin the top

0.5 inch (1 cm) of the soil profile.

High soil burn severity

Structural aggregate stability reduced or

destroyed. Loose- and single-grained

soil dominates and is exposed or under

ash (up to 4 inches or 10 cm of ash). 

Consumption of organic matter in the

top 2 inches (5 cm) of the soil profile.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 15

D. Roots

Low soil burn severity

Fine roots (~0.1 inches or 0.25 cm

diameter) intact and unchanged.

Moderate soil burn severity

Fine roots nearsurface may be charred

or scorched; large roots intact (~0.25

inches or 0.5 cm diameter).

High soil burn severity

Many or most fine roots near surface

consumed or charred. Some charring

may occur on very large roots(~3 inches

or 8 cm diameter).
16 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

E. Soil Water Repellency

Low soil burn severity

No fire-inducedwaterrepellency. Water

infiltrates immediately; however, some

soils exhibitwaterrepellency evenwhen

unburned (see section 4.3).

Moderate soil burn severity

Weak tomediumwaterrepellency found

at or just below soil surface. Water

infiltrates slowly.

High soil burn severity

Strongwaterrepellency found atsurface

or deeper. Water does not infiltrate. In

case of extreme soil heating, soil water

repellency may be destroyed or may

exist at very deep soil depths (6 inches

or 15 cm).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 17

Pre-Fire Vegetation 

Considerations

Pre-fire vegetation density (including ground

fuels, litter, and duff) is a key factor to consider

whenmappingsoil burn severity. Forthepurposes

of this field guide, vegetation types have been

generalized into two pre-fire vegetation densities

within three fire-prone ecosystems that represent

widespreadconditionsinthewesternUnitedStates.

Chaparral: Low and high density chaparral

vegetation are represented by chaparral or mixed

shrub-chaparralvegetationcommunities. Ground

fuels are characteristically sparse, except directly

undertheshrubcanopy,witharangeoflowtohigh

density canopy fuels. Mean annual precipitation

generallyrangesfrom12to20inches(30to50cm).

Mixed conifer forest: Themixed conferforest

contains ground fuels that range from sparse to

dense. Mean annual precipitation varies widely

from 20 to 80 inches (50 to 200 cm) and is generally dependent on elevation; higher elevation

precipitation is dominated by snow. Sparse, dry

ground fuels are characteristic oflower precipitation regimes; while higher precipitation regimes

produce thicker, wetter, and denser ground fuels. 

Canopyfuelsalsovarylargelybyprecipitationand

locallybyaspect(for example,southfacingslopes

aregenerally dryandsparse). Groundandcanopy

fuels may also vary if a recent disturbance such

as disease, insect, or blowdown event has caused

widespread treemortality, orif a past disturbance

such as thinning or harvesting occurred.

Sagebrush/grassland: The sagebrush/grassland has sparse ground fuels because of the

arid climate associated with rangelands. Mean

annual precipitation ranges from 4 to 8 inches

(10 to 20 cm). Canopy fuels can be dense but

aremore often intermixedwith patches of grass,

native andnon-native forbs, andexposedmineral

soil. Though some of these areas are generally

not at high risk of increased soil erosion after

wildfires, they are often at high risk of weed or

noxiousspeciesinvasion andmay be considered

for post-fire rehabilitation treatments.

Beyond identifying the general vegetation

density characteristics of an area, the spatial

structure or heterogeneity/homogeneity of the

vegetation must be considered. Large patches

of dense vegetation (such as a hillside) in an

otherwise sparsely vegetated area can lead to

an area of high soil burn severity that may have

hydrological implications in the event of high

intensity precipitation. Smaller patches of dense

vegetationthat createhighsoilburnseveritytypically have less potential for increasing runoff or

soil erosion in a watershed. Vegetation’s spatial

distribution affects fire behavior and residence

time, which directly impact subsequent soil

changes. Vegetation types and the spatial distribution of ground,surface, ladder, and canopy

fuels can vary greatly across an area.

Pre-fire vegetation type and density are important factors to consider when interpreting

the BARC layer. Before a wildfire, areas of low

surface vegetation biomass will have low nearinfrared reflectance values in remote sensing

imagery. When awildfire occurs and burns areas

of low biomass, the change is not substantial to

the satellite sensor and is often correctly classified as low soil burn severity in the BARC. 

This may be an appropriate classification when

assessing only the soil and ground conditions. 

However, if the BARC (and its source data, the

dNBR) is used to help map vegetation effects, it

may underestimate the vegetative burn severity.

The following photo series is intended as a

general guide. Choose the density model that

most closely matches your site, and consider

the severity indicators for that model. Be aware

of localized discrepancies and their potential

implications on the post-fire soil and ground

conditions. Field specialist interpretation of

soil conditions in areas of moderate vegetation

density is necessary.

Thefollowingvegetationconsiderationsphoto

series is arranged by density, vegetation class,

and burn severity. See table 1 for a depiction of

the likelihood of encountering these soil burn

severity conditions.
18 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Vegetation Considerations Photo Series

A. Low Density Chaparral

Low soil burn severity, low density chaparral—most common condition as ground and canopy

fuels are sparse, causing minimal soil heating.

Substrate—

soil/litter/duff 

Surface litter charred or partially

consumed. Leafstructures charred but

recognizable. Mineral soil visible with

discrete patches of ash; soil structure

and roots unchanged. 

Surface vegetation—

understory/shrubs/forbs 

Fine fuels(grasses and forbs)scorched

or partially consumed. Coarser shrub

stems intact.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage mostly unaltered. 

Patches of scorched leaves generally

not dominant. 

5-30% charred canopy
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 19

Moderate soil burn severity, low density chaparral—unlikely to occur as mappable polygons

due to low vegetation density. These conditions may occur directly beneath individual shrubs.

Substrate—

soil/litter/duff 

Surface littermostlycharredor consumed;

blackened or gray ash on surface. 

Soil structure and roots unlikely to be

significantly altered.

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and small

stems) mostly consumed. Shrub stems

charred; root crowns intact.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage mostly consumed; shrub

skeletons and smaller stems (< 0.5 inches

or 1 cm) remain.

30-100% charred canopy
20 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

B. High Density Chaparral

Low soil burn severity, high density chaparral—even in high density chaparral, soil heating is

commonly of short duration, causing minimal effects on the soil.

Substrate—

soil/litter/duff 

Surface litter charred or partially

consumed. Leaf structures charred but

recognizable. Mineral soil visible with

discrete patches of ash. Soil structure

and roots unchanged.

Surface vegetation—

understory/shrubs/forbs 

Fine fuels(grasses andforbs)scorchedor

partially consumed;shrub stemsintact.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage mostly unaltered. 

Patches of scorched leaves generally

not dominant. 

5-30% charred canopy
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 21

Moderate soil burn severity, high density chaparral—most common condition, canopy

consumption may be patchy, mixed severity, or fairly continuous; soil moderately affected.

Substrate—

soil/litter/duff 

Surfacelittermostlycharredorconsumed;

blackened or gray ash on surface. Soil

structure and roots unlikely to be altered.

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs and small

stems) mostly consumed. Shrub stems

charred; root crowns intact. 

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage mostly consumed. Shrub

skeletons and smallerstems(< 0.5 inches

or 1 cm) remain.

30-100% charred canopy
22 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

High soil burn severity, high density chaparral—generally found only in old, dense, decadent

stands, especially if in large, continuous patches.

Substrate—

soil/litter/duff 

All or most organic surface matter is

consumed, leaving fine gray or white

ash and extensive charred mineral soil. 

Soil surface black, brown, or reddish

beneath ash. Fine roots and organic

matter consumed, resulting in loss of

soil structure. 

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and small

stems) consumed including fuels

< 1 inch or 2 cm.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage completely consumed. 

Only larger diameter (> 1 inch or 2 cm)

stems remain.

90-100% charred canopy
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 23

C. Low Density Mixed Conifer Forest 

Low soil burn severity, low density forest—most common condition as ground and canopy fuels

are sparse, causing minimal soil heating.

Substrate—

soil/litter/duff 

Surface litter char red or partially

consumed. Leaf or needle structures

charred but recognizable. Duff largely

intact. Soil structure and roots remain

largely unchanged.

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and smaller

shrubs) scorched or partially consumed.

Canopy vegetation—

ancillary factors for additional clues

Tree canopy mostly unaltered. Slight

scorch may be observed.

5-10% charred tree canopy and < 3-ft or

1-m char heights
24 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Moderate soil burn severity, low density mixed conifer forest—unlikely to occur in very sparse

forest systems except where significant understory occurs, and in those cases, soil burn severity is

a function of the understory vegetation system rather than the sparse forest.

Substrate—

soil/litter/duff 

Surface litter charred or partially

consumed. Leaf or needle structures

charred but recognizable. Duff largely

intact. Soil structure and roots remain

largely unchanged.

Surface vegetation—

understory/shrubs/forbs 

Finerfuels(grasses,forbs,shrubs,twigs,

and small limbs) mostly consumed.

Canopy vegetation—

ancillary factors for additional clues

Tree canopy mostly scorched or

consumed.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 25

D. High Density Mixed Conifer Forest

Low soil burn severity, high density forest–will generally occur where surface fuels are lightest.

Substrate—

soil/litter/duff 

Surface litter charred or partially

consumed. Leaf or needle structures

charred but recognizable. Duff largely

intact. Soilstructure and rootsremains

largely unchanged.

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and smaller

shrubs)scorched or partially consumed. 

Twigs and small limbs on ground may

also be consumed.

Canopy vegetation—

ancillary factors for additional clues

Tree canopy mostly unaltered. Slight

scorch may be observed.

5-10% charred tree canopy and

< 3-ft or 1-m char height
26 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Moderate soil burn severity, high density mixed confer forest—most common condition; often

interspersed with localized patches of low and high soil burn severity. Soil is moderately affected.

Substrate—

soil/litter/duff 

Surface organics may be charred, but

leaf or needle structure recognizable. 

If consumed, charred needles or leaves

on trees will create mulch quickly. Gray

or black ash or charred litter may cover

much ofsurface; soil structure and roots

generally intact.

Surface vegetation—

understory/shrubs/forbs 

Surface fuels and understory vegetation

may be consumed. All plant parts may

be consumed including fuels > 1 inch or

2 cm. Large logs consumed or deeply

charred.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage scorched but generally

not completely consumed. Needles

or leaves remain on trees (significant

potential for needle-cast to provide

mulch).

10-80% charred canopy and

3-6-ft or 1-2-m char height
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 27

High soil burn severity, high density mixed conifer forest—most likely to occur where ground

fuels were dense prior to the fire. Can also be found in localized patches by tree stumps or where

large, downed logs burned; soil is severely affected.

Substrate—

soil/litter/duff 

Allormostsurfaceorganics are removed,

leaving fine gray or white ash and

extensive charred mineral soil. Soil

surface black, brown, orreddish beneath

ash. Soil structure weakened due to

consumption of fine roots and organics. 

Evidence of previously significant litter

or surface fuels (deep ash; duff lines on

trees and rocks).

Surface vegetation—

understory/shrubs/forbs 

Surface fuels and understory vegetation

consumed. All plant parts may be

consumed, including fuels > 1 inch or

2 cm. Most tree stems are charred,

and large logs are consumed or deeply

charred.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage completely consumed. 

Few to no needles or leavesremaining on

trees(little to no potentialfor needle-cast

to provide mulch).

90-100% charred canopy and

> 6-12-ft or 2-4-m char height
28 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

E. Low Density Sagebrush/Grassland

Low soil burn severity, low density sagebrush/grassland—only common condition; areas of

burned, partially burned, and unburned litter and vegetation.

Substrate—

soil/litter/duff 

Surface litter char red or partially

consumed. Leaf structures charred but

recognizable. Mineral soil visible with

discrete patches of ash beneath individual

shrubs. Soil structure and roots remain

unchanged.

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and smaller

stems) scorched or partially consumed. 

Large shrub stems intact.

Canopy vegetation—

ancillary factors for additional clues

Patchy canopy foliage scorch; may be

partially to almost completely consumed.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 29

F. High Density Sagebrush/Grassland

Low soil burn severity, high density sagebrush/grassland—areas of burned and partially burned

litter and vegetation.

Substrate—

soil/litter/duff 

Surface litter charred or partially

consumed. Leaf structures charred but

recognizable. Mineral soil visible with

discrete patches of ash. Soil structure

and roots unchanged. 

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and smaller

stems) scorched or partially consumed;

shrub skeletons and fine stems intact. 

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage scorched or partially

consumed. 

5-30% charred canopy
30 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Moderate soil burn severity, high density sagebrush/grassland—most common condition;

may be patchy, mixed severity, or fairly continuous canopy consumed; soil not severely affected.

Substrate—

soil/litter/duff 

Su r face litter mostly cha r red or

consumed. Blackened ash on surface. 

Soil structure and roots unlikely to be

altered. 

Surface vegetation—

understory/shrubs/forbs 

Finer fuels (grasses, forbs, and small

stems) consumed. Sagebrush stems

charred or consumed;root crownsintact.

Canopy vegetation—

ancillary factors for additional clues

Canopy foliage mostly consumed. 

30-90% consumed canopy
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 31

Use of the Soil Burn Severity 

Map in Post-Fire Assessments

Using the Soil Burn Severity Map

Once it is field verified, the soil burn severity map is combined with information about

topography, pre-fire vegetation, and precipitation to determine the hydrologic and erosion

response potential of burned watersheds. This

is one of the most important purposes of the

soil burn severity map. Hydrologic and erosion

response predictions can be made with a variety

of models and techniques. A brief summary of

available modelsthat are commonly used in the

post-fire environment follows. The pros and

cons of some of these models are discussed in

detail by Foltz and others (2008). These model

results can be displayed in tables, graphs, or GIS

attribute layers.

Common Post-Fire Hydrology and 

Erosion Prediction Models

WEPP: The Water Erosion Prediction Project

(WEPP)is a physical-basedmodel that predicts

runoff, upland soil erosion, and hillslope

sediment delivery (Flanagan and Livingston

1995). The climate file that drives WEPP is

stochastically generated from 2600 historical

weatherstation data and ismodified by theRock

Clime interface formountainousregions(Elliot

2004). Several interfaces have been developed

specifically for post-fire assessments using

the WEPP model. These and other erosion

and runoff models used by BAER teams are

discussed below. WEPP and itssub-models can

be accessed online at http://forest.moscowfsl.

wsu.edu/fswepp.

ERMiT: Erosion Risk Management Tool

(ERMiT) is a tool developed specifically for

post-fire assessments that predicts the probability associated with a given amount of

single-storm soil erosion in tons/acre (tons/ha)

for a given hillslope topography in each of five

yearsfollowing forest, chapparal, and sagebrush

wildfires(Robichaud and others 2007).ERMiT

also predicts the benefits of mitigation treatments during the recovery period for seeding,

mulching, and installing contour-felled log

erosion barriers.

GeoWEPP: GeoWEPP develops a drainage

network for a selected region and then defines

the channel network and hillslope polygons for

a selected watershed by defining the watershed outlet for pre- and post-fire conditions

(Renschler 2008). GeoWEPP utilizes two

modes: “Flowpath” and “Watershed.”Flowpath

mode predictsrunoff and erosion for every pixel

within the selectedwatershed. Watershedmode

predicts sediment delivery from each hillslope

polygon and streamchannelsegmentidentified.

Disturbed WEPP: Disturbed WEPP allows

usersto describe numerous disturbed forest and

rangeland erosion conditions,including lowand

high soil burn severity conditions. The interface

output provides mean annual runoff, erosion

rates, and sediment yields as well as a return

period analysis and the probability of a given

amount of erosion occurring the year following

a disturbance. Additionally,the usermay review

the WEPP summary and extended outputs.

Curve Number: The curve number (CN)

method estimates runoff depth (Ponce and

Hawkins 1996). It considers rainfall, soils,

cover type, treatment/conservation practices,

hydrologic conditions, and slope steepness. Users choose CNs based on cover type, treatment

(in the case of post-fire modeling, soil burn

severity), hydrologic conditions, and hydrologic

soil group to estimate runoff and peak flow;

therefore, the CN is the single most important

parameter in this method. Two CN methods

are often used during post-fire assessments:

WILDCAT4 (Hawkins and Greenberg 1990)

and FIRE HYDRO (Cerrelli 2005).
32 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

TR-55: The TR-55 model usesthe runoff CN

as an input parameter. TheTR-55 is a simplified

procedure to calculate the stormrunoff volume,

peak flowrate, hydrograph, and storage volume

forstormwatermanagementstructuresin small

watersheds (USDA NRCS 2005). It initially

assumes a Natural Resource Conservation Service (NRCS) Type II rainfall distribution and

later improves by adding three more rainfall

distributions (Type I, IA, and III). TR-55 then

programs the computations for estimating the

time of concentration.

WMS: The Watershed Modeling System

(WMS) (http://www.ems-i.com/index.html)

provides a graphical interface to the TR-55

model and uses CNs to predict storm runoff,

peak flow rate, and hydrograph for watersheds. 

The user can select the variousrainfall distributions described under TR-55.

RUSLE: The Revised Universal Soil Loss

Equation (RUSLE) model was developed for

cropland applicationsto predict average annual

erosion (RUSLE 1993). It has been applied to

post-fire modeling using GIS techniques after

the Cerro Grande Fire in New Mexico (Miller

and others 2003) and with other fires.

FERGI:TheFireEnhancedRunoff andGully

Initiation (FERGI) model is a physical-based

mathematical description of hillslope hydrologic and geomorphic response to a given set of

weather events (Luce 2001). FERGI estimates

theprobabilityofpost-fire rainfall excess,runoff

generationamount, andgullyinitiationpositions

on hillslopes with and without mitigations using contour-felled logs or log erosion barriers.

USGS Regression Equations: The USGS

regression equations are used to estimate magnitude and frequency of floods of both gauged

and ungauged streamsfrom watersheds greater

than 5 mi2 (13 km2

) (Thomas and others 1997). 

StreamStat, a web-based tool, has been used

recently for various hydrologic regions based on

theirstreamgauge records,basincharacteristics,

and numerous studies throughout the United

States (USGS 2007). The pre-fire hydrologic

response is adjusted based on the percentage of

the watershed area that was burned at moderate

and high soil burn severity and a user-defined

modifier.

Rational Method: The traditional rational

method was originally developed to calculate

the flood peak flow under the assumption that

the intensities of both rainfall and infiltration

are uniformly distributed in time and space

(Ponce 1989). The modified rational method

adjusts the rainfall to a patterned or design

storm distribution.

ModelchoiceisoftendeterminedbytheBAER

team experience, available data, geographical

area, and desired output. It is important to note

that the soil burn severity map is not a map of

runoff or erosion potential but it is an input into

hydrologic or erosion models as it represents

fire-caused changes in those parameters that

affectrunoff or erosion potentialsuch as ground

cover, hydraulic conductivity, hydrologic soil

group,soilK-factor, curve number, and interrill/

rill erodibility.

Displaying Surface Runoff Potential 

on Maps

After the hydrologic models are run for the

burned areas of interest, the results can be displayed in GIS. For example, a runoff potential

map might represent the post-fire watershed response conditionsthatreflectthe likelyfirst-year

runoff. These runoff amounts could be divided

into four classes (unchanged, low, moderate,

and high) that represent runoff or peak flow potential. The post-hydrology-modeling products

generally do not produce what looks like a soil

burn severity map because other physiographic

features (slope, aspect, soil type, and expected

precipitation) are used during the modeling.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 33

Displaying Erosion Potential on 

Maps

Using GIS, the soil burn severity map can

be overlaid with slope, soil type, and amount

of exposed soil and rock. These combinations

can be grouped appropriately to aid in erosion

modeling. Forexample,aseriesofERMiTmodel

runs for the dominant groups of characteristics

can be calculated and the resulting values can be

displayedintabularformor addedtothe attribute

table of the combined feature class to display

a map of post-fire soil erosion potential. The

erosion potential map may also look different

from the soil burn severity map. Ahigh soil burn

severity condition on flat ground would have

a low erosion potential due to the topography.

Other Uses of a Soil Burn Severity 

Map

Additionally, the spatial and temporal “snapshot” of soil burn severity often becomes a

baseline for monitoring changes in soil and

ground conditions and vegetation recovery. 

Several other GIS products such as tree mortality can be derived from these maps and field

observations. Overlaying the soil burn severity

map with steep slopes or rock outcrops can be

usedforidentifyingandmodelingpost-fire slope

stability issues. These maps can also be used

to determine soil burn severity by ownership,

watersheds, or land cover.

Analysis for implementation planning can be

done using GIS to develop polygons of high

soil burn severity that may be under consideration for treatment such as aerial seeding or

mulching. Modeling can be used to determine

natural reseeding likelihood based on polygon

size and shape (edge effect) as well as to map

the proximity of potential seeded areas to nest

sites, cultural resources, and other resources at

risk. In short, the soil burn severity map can be

used by a variety of resource specialists for a

range of analyses.

Conclusion and Management 

Implications

Using a common set of soil burn severity

indicators and definitions in rapid, post-fire

assessment is important. The guidelines

presented in this report will help users identify

fire effects that are directly related to postfire soil conditions rather than to overstory

or ecosystem conditions. Consistency in

assessments will lead tomore credible products

beingusedtoevaluatepost-fire risktorunoff and

erosion potential andwilllead tomore informed

and financially prudent decisions regarding

post-fire rehabilitation treatments. Themethods

outlined in this report will also help increase

the efficiency and speed of assessments and

will allowspecialistsfromdifferentregions and

disciplinesto produce consistent products. The

process of refining the BARC to create the soil

burn severitymap should be clearly documented

with descriptions of all systematic and local

adjustments to the soil burn severity classes. A

few sentences and photos describing what low,

moderate, and high soil burn severity lookslike

for each vegetation type is also an important

part of the assessment record. These metadata

and clearly labeled digital and hard copyBAER

soil burn severity maps should be delivered to

managers, other agencies, resource specialists,

community groups, media, and individuals.

Acknowledgments

We thank the entire BAER community for its’

support of this document. Many people provided

excellent review comments, including (in alphabetical order by last name): Craig Busskohl,
34 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Alex Janicki,Jason Jiminez,Tommy John,Peter

Jordan, and Dean Sirucek. Abig thanksto those

whoprovidedphotosthatwereusedfortheguide:

Ashley Covert, Stefan Doerr, Andrew Hudak,

Michael Pellant, Brad Rust, and Dean Sirucek. 

We are also very appreciative of the many other

people who lent us photos that were not used.

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 37

Appendix A—How to Map Soil 

Burn Severity

This Field Guide for Mapping Soil Burn Severity is intended to be a standardized guide to

help users translate field-observed soil and site

conditionsthat represent the low, moderate, and

highsoilburnseverityclassesintomappolygons

for use by resource specialists to predict runoff

and erosion.

Mapping Concepts

Mapping,whether done inGIS or by hand, is a

skillthatisgenerallytaskedtoanindividualwith

expertise and knowledge of mapping concepts

and, often, previous knowledge ofthe area being

mapped. The following sources are excellent

references for mapping, and, though focused

on mapping soils, much of the information and

many of the concepts apply to mapping natural

resources in general. The National Soil Survey

Handbook (USDA NRCS 2009) (http://soils.

usda.gov/technical/handbook/) and Chapters 1

and 2 of the Soil Survey Manual (SSM) (Soil

Survey Division Staff 1993) (http://soils.usda.

gov/technical/manual/) are available online.

The discussion of soil forming factors in the

SSM,Chapter1,highlightstheneedforthemappertounderstandthesoil-landscaperelationships

in order to delineate polygons on a map:

“Regional patterns of climate, vegetation,

and parent material can be used to predict the

kinds of soil in large areas. The local patterns

of topography or relief, parent material, and

time, and their relationships to vegetation and

microclimate, can be used to predict the kinds

of soil in small areas. Soil surveyors learn to

use local features, especially topography and

associatedvegetation, asmarksofunique combinations of all five factors. These features are

used to predict boundaries of different kinds

of soil and to predict some of the properties of

the soil within those boundaries.” (Soil Survey

Division Staff 1993).”

Extending this idea of soil forming factors

to soil burn severity, one could argue that soil

burn severity is a function of pre-fire vegetation

type, density, amount and type of ground fuels,

litter, and terrain (as it influences fire behavior

andfire frequency). Weatheristheunpredictable

element. We can directly observe these site factors(otherthanweather)or atleasttheirpost-fire

evidence. An area with heavy ground fuels can

experience high soil burn severity, whereas an

areawithlittle tonofuelwillnot. Theheavyfuels

provide the opportunity for high heat and long

residence times—the main criteria resulting in

high soil burn severity conditions. On the other

hand, a fire can pass quickly over an area with

light fuelssuch as grass. The vegetation may be

consumed but heat residence time is brief and

soil characteristicsremainunchangedbythe fire.

Post-fire field reconnaissance allows team

members to examine the condition of the soil

and to estimate the pre-fire characteristics at a

given site. It is important for the mapper to be

abletodeterminerelationshipsbetweensitecharacteristics and soil burn severity. For example,

it is common to observe high soil burn severity

in a California chaparral system on blackened,

north-facing slopes that had high pre-fire vegetation density. Less dense (drier) south-facing

slopes may also appear black after the fire but

commonly exhibit moderate or low soil burn

severity due to the lighter fuels. Observing and

understanding thisrelationship can help to map,

by extrapolation, those areas in large fires that

an observer may not have time to visit. 

Another element that is crucial to effective

mapping is designing map units. Though this

can be far more complex when mapping soils

than when mapping soil burn severity, the basic

conceptissimilar. Chapter2oftheSSMprovides

useful insight:

“While studying the soil patterns in different

landscapes,the soilscientistmust keep inmind

how best to relate the patterns observed to
38 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

appropriate map units. ... This requires many

judgments. Every map unit that is tentatively

identified is evaluated by two tests: 1) Can it

bemapped consistently? 2)Isit needed tomeet

the objectives of the survey?” (Soil Survey

Division Staff 1993).”

To apply this to soil burn severity mapping,

map units should be meaningful for the end

use (predicting runoff and erosion) and not so

complex or detailed that they cannot be mapped

within the short time frame of a BAER assignment. Mappers can, in part, meet these goals by

keeping the legend simple; using simple classes

of “low,” “moderate,” “high,” and “unburned”;

anddescribingthemapinclusions(orexclusions)

in the map metadata.

This leads to the concepts of map unit purity,

map scale, and delineation size. Chapter 2 ofthe

SSM offers this guidance:

“Standards of purity are adjusted according

to the precision required by the survey objectives. Probably all delineations contain some

kinds of soil besides that identified in the map

unit name.”

“The map scale must be large enough to allow

areas ofminimumsize to be delineated legibly. 

... The choice of map scale also depends on

the perspective of the user.”

“Map users who want a broad perspective of

large areas, however, are usually concerned

with comparisons among delineations of all, or

a large part, ofthemap. Consequently, delineations onmapsforsuch uses are generally larger

and fewer in number.” (Soil Survey Division

Staff 1993).”

With BAER soil burn severity mapping, the

scale (and detail) of mapping is almost always

moregeneral. Thereisnotsufficienttimeduringa

BAERassessmenttocreateahighlydetailedmap

of soil burn severity, nor would such a detailed

map effectivelymeet the needs ofthe users(runoff and erosion prediction). The increased use

of remote sensing and BARC maps has greatly

increased both the level of detail and precision

of soil burn severity mapping, and the digital

nature of the BARC lends itself to use in spatial

models for runoff and erosion. It is important

to keep in mind, however, that the models used

are not particularly sensitive to slight changes

in soil burn severity; thus, it is more efficient

and more useful to keep the map units(soil burn

severity classes) and delineations fairly broad

while still accurately capturing the location and

distribution of soil burn severity classes in the

watersheds throughout the burned area.

Points to Consider When Mapping 

Soil Burn Severity:

The ultimate purpose of the soil burn severity

map is to predict increased runoff and erosion

from the burned area, especially in areas with

resource values at risk. Remembering this will

help users keep perspective on the level of detail

and focus their efforts on specific areas at risk. 

• Get the big picture. Aquick reconnaissance

(via helicopter, overlooks, or quick drivethroughs) helps to get an overview of the

burned area and to develop a sense of the

extent, location, and distribution of the

“green,” “brown,” and “black” areas. These

are the broad visual indicators that will

guide the surveyor’sfield observations and

map delineations. It is a good idea to record

notes on a topographic map or post-fire

satellite image of the area. To avoid bias,

avoid using the BARC.

• Gather field information. As much time

as possible should be spent on the ground

gathering site-specific information. This

field time can begin by visiting areas that

were identified during the reconnaissance

as largely “green,” “brown,” or “black.”

These become representative polygons for
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 39

each vegetation type and density. Detailed

notes should be taken, data should be

recorded on the field data sheet (Appendix

B) at as many ground points and traverses

as possible, andGPS coordinatesshould be

collected forthose points and traverses. The

mapper can now begin to assess the types

of vegetation, terrain, and other features

in these areas and the ground conditions

and can develop an understanding of the

relationships among pre-fire vegetation,

terrain, and soil burn severity. 

• Start forming “map unit” concepts. For

example, a large area appeared blackened

from the air. During the field visit, it turns

out that while it is all black, half of it was

dense forest (pre-fire) and half of it was

shrubland. Ground conditions in these

areas indicate that the dense forested

areas exhibit a preponderance of soil

characteristicsthat point to a high soil burn

severity classification (for example, deep

ash, no fine fuels or soil cover remaining,

loss of soil structure, etc). In the shrub

areas, however, soil characteristics point

to a moderate classification (for example,

some unburned litter remains under the

thin ash, structure is intact, etc). This is a

relationship that can likely be extrapolated

to other parts ofthe burn. There will not be

time to visit every polygon, so the mapper

must learn to develop these relationships

in mind and take good notes. 

• Focus the majority of field time in the 

“black.” “Black” and sometimes “brown”

areas are most likely to be sources of

increased runoff. There will never be

enough time to visit all of the identified

at-risk field sites, so field time should be

spent wisely. However, spending some

time in the “green” will help the mapper

understand what pre-fire soil and ground

conditions looked like so a determination

can be made as to how much has been

changed as a result of the fire. 

• Develop a concept of purity. Based on

initial field investigations, it might be

estimated that the black areas that were

mapped as “high” soil burn severity in

forest types are 80 percent high but have

scattered inclusions of moderate and low. 

Or black, shrubby areas that were mapped

as “moderate” are generally 75 percent

moderate, but have small spots of “high”

or larger spots of “low” scattered in them. 

Capture these concepts in field notes and

map metadata. It is important to include

these descriptions of soil burn severity

classes in the mapping technical report. 

• Draw polygons on a map. If available, a

post-fire satellite image should be used; if

not, a topographic map should be used. A

post-fire satellite image helps determine

exactly where likely polygon delineations

should be drawn; however, cutoffs between

categories are not always “black and

brown,” so to speak. Judgment calls based

on field data and reconnaissance will be

neededwhen drawing polygon boundaries. 

The end use of the map (runoff and erosion

prediction) should be kept in mind as

delineations (polygons) are created—

meaning, areas that are likely to behave

similarly should be lumped, and areasthat

will behave differently should be split.

All of the above steps are greatly facilitated

if the mapper has a BARC that is a decent fit to

the field ground observations. If the BARC is a

good start but not accurate, determine whether

systematic or localized edits are needed (see

page 5). 
40 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

This form is a guide for 10 observation points at a single field stop. It will not always be necessary

to record 10 observations if site variability is low; however, if variability is high, more observations

may be needed. The purpose is to quickly record information to document observations of soil burn

severity and provide support and rationale for post-fire treatments. Thisform will also provide metadata to describe site conditions. The data collected here may be used as inputs to hydrologic models.

You will have to use your professional judgment when estimating change from pre-fire conditions. Examine areas of similar soil and vegetation that have not burned and form your opinion as

to the degree it has or has not been changed by the fire. An electronic copy of this form is available

at http://forest.moscowfsl.wsu.edu/BAERTOOLS/.

Appendix B—Soil Burn Severity Field Data Sheet and Key

Soil Burn Severity Assessment 

Field Data Sheet Fire name: Observers:

Date: Site ID: GPS coordinates: BARC classification:

Observation point Ground

cover (1)

Surface color and

ash depth (2)

Soil

structure

(3)

Roots

(4)

Soil water

repellency (5)

Observed

soil burn

severity

class (6)

Photo # Other

comments

EXAMPLE 20 to 50% white, 1 mm no change intact I 3 mL surf Mod 23 homogenous

1

2

3

4

5

6

7

8

9

10

Average/majority

for site (7)

Site characteristics: Aspect (deg): Slope %:

Slope length (ft or m): Slope position: Lower Middle Upper Ridge Other

Soil texture class: 

clay loam, silt loam, loam

Dominant pre-fire

vegetation type

Pre-fire vegetation

density

Vegetation

comments:

Other

notes:

Surface rock %: Chaparral Low

Soil comments: Forest High

Sagebrush/grassland Other

Other
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 41

Data Form Columns:

(1) Ground cover: Record an estimated percentage of cover (greater than 50%; 20 to 50%; or

less than 20%). Ground cover means effective organic cover as it pertains to mitigation of runoff

and erosion and includes litter, duff, and woody debris.

Example: “20 to 50%”

(2) Surface color and ash depth: Include a brief note on color and depth of ash (inches or cm),

if any. 

Example: gray, 5 cm

(3) Soil structure: Has it changed from pre-fire structure? The most common change is from a

granular structure in the surface horizon to a loose- or single-grained soil in areas where heat residence time was long and organic matter was consumed. 

Example: “changed (loose)” or “no change”

(4) Roots: Have they been altered from pre-fire condition?

Example: “scorched,” “no change,” or “very fine consumed”

(5) Soil water repellency: Use the infiltrometer (I) or water drop penetration time method (W)

and record volume of infiltration or how long water takes to infiltrate, respectively. If repellency is

observed, note the depth tested (inches or cm).

Example: “I/3mL/at surface” or “W/25 sec/ at 1-2 cm”

(6) Observed Soil Burn Severity Class: Record the soil burn severity class at the observation

point.

Example: “Unburned,” “Low,” “Moderate,” or “High”

(7) Average/Majority for Site: Estimate the most frequent or average of the 10 observations.
42 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Appendix C—Using a Mini-Disk Infiltrometer to Assess PostWildfire Soil Water Repellency and Reduced Infiltration

The Mini-disk Infiltrometer (MDI) has been adapted for use as a field test of post-fire infiltration

and soil waterrepellency. Although theWater Drop PenetrationTime (WDPT)test has been the common field test for soil water repellency, the MDI test takes less time, is less subjective, and provides

a relative infiltration rate. The relative infiltration rate indicates reduced infiltration potential that

may result from fire-induced soil water repellency, soil sealing, and other factors. For each test, the

porous base plate of the MDI is placed on the soil, and the amount of water that passes into the soil

in one minute is measured. Post-fire soil water repellency has most often been detected at 0.2 to

1 inch (0.5 to 3 cm) below the visible surface. In burned areas, soil surface measurements where

soil and ash mix often indicate non-water repellent soil, making it necessary to brush or “dust” the

ash away before testing the uppermost soil layer (fig. C1).

Test steps (abridged version, see Robichaud and others 2008a):

(1) Using a brush ortrowel(depending on testing depth), expose

the soil to be tested by removing overlying material (ash

and organic material).

(2) Fill the MDI and set to 1 cm suction.

(3) Record the start volume (mL).

(4) Place the MDI porous disk flat against the soil with the MDI

held perpendicular to the surface. Start the timer when the

MDI disk and soil come into contact. 

(5) Continue to hold the MDI against the soil surface so that

the entire infiltration disk is in contact with the soil for one minute. 

(6) At the end of one minute, remove the MDI from the soil and record the end volume.

Field test materials:

• Mini-disk Infiltrometer

• water

• hand trowel

• stopwatch

• ruler to measure soil depth

• data recording sheets

• plastic squirt bottle for

rinsing porous disk

Figure C1. Using the MDI in the field.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 43

Sampling a Burned Area

Post-fire assessments of soil water repellency and reduced infiltration are needed within days of

fire containment. This short time frame for sampling necessitates a sampling scheme that 1) focuses

on areas where soil water repellency and reduced infiltration are most likely; and 2) provides a logical method for extrapolation of sample results to unsampled areas.

The burned area is divided into areas of similar characteristics based on the factors that correlate

strongly with post-fire soil water repellency—burn severity and slope aspect (which is used as a

simple surrogate for vegetation type and density). MDI tests are done along transects located on

upper and lower positions of selected hillslopes from each combination of moderate and high burn

severity and north and south aspects. The results from the sampled hillslopes are applied to other

burned but not sampled hillslopes with the same burn severity and aspect. Like most statistical

analyses, the more measurements taken, the higher the confidence level assigned to the results. This

sampling scheme, based on the classification of the burned area, can provide practical guidance for

making the most of the limited time available for post-fire assessment.

A recently published Research Note (RMRS-RN-33), New Procedure for Sampling Infiltration 

to Assess Post-Fire Soil Water Repellency (Robichaud and others 2008a), provides instructions for

using the Mini-disk infiltrometer, field data sheets, a detailed sampling scheme with pre-determined

sample size and confidence levels, and a formatted data analysis spreadsheet tool. An electronic

copy of the Research Note and spreadsheet tool can be accessed at: http://forest.moscowfsl.wsu.

edu/BAERTOOLS/. 

Interpreting Results

The MDI test measures the volume of water (mL) that passes from the infiltrometer into the soil

in one minute. Through field testing, the one-minute interval has been proven to be long enough

to detect water repellent soil conditions yet fast enough to be a useful assessment procedure for

post-fire assessment teams. The MDI test provides a relative infiltration rate that can be used to

classify soil water repellency and compare the infiltration capacities of tested sites. The mean of

three individual MDI readings is the MDI value at that sample location. The MDI value determines

the degree of soil water repellency (strong, weak, or none) at each depth sampled at each location. 

The proportion of MDI values (percent) that indicate strong, weak, and none are used to describe

the degree and extent of soil water repellency on the assessed hillslope.

Three classes of soil water repellency were identified based on the relationship between the common WDPT test and MDI test values performed at the same location:

MDI test	 WDPT test

Strong (0 to < 3 mL min–1) WDPT values > 40 sec

Weak (3 to < 8 mL min–1) WDPT values of 11-40 sec

None (> 8 mL min–1) WDPT values of 0-10 sec

The WDPT values listed above are from the guidelines generally followed by the BAER community. Because moderate water repellency is difficult to define and the implications for potential

watershed response can be ambiguous, we suggest using strong, weak, and none for water repellency
44 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

classes. Strong water repellency is indicative of significantly reduced infiltration and increased

potential for watershed response. Areas with strong water repellent soils will often be targeted

for post-fire erosion and runoff mitigation. Soils classified as weak (or none) generally have an

infiltration potential similar to the pre-fire condition.

The soil water repellency data collected with this sampling scheme is specific to a class of soil

burn severity and slope aspect (moderate/north, moderate/south, high/north, or high/south), and the

assessment from the sampled slopesis applied to the unsampled slopes of the same soil burn severity

and aspect. This can be useful in prioritizing areasfor post-fire stabilization treatments. Other factors

to consider when prescribing stabilization treatments are: 1) fallen needle cover (needle-cast) that

may provide substantial natural protection from erosion; and 2) the size of patches (continuity) of

severely burned areas because large patches can also increase runoff and erosion potential even if

soils were not classified as strongly water repellent.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 45

Appendix D—Example of the Soil Burn Severity Mapping 

Process, 2006 Derby Fire 

The Derby Fire (45.6° N., 109.9° W) burned approximately 200,000 acres (81,000 ha) on the

Gallatin National Forest in Montana. The fire burned a variety of vegetation types (grass, shrub,

and forest) and over substantial elevation changes (3900 to 7400 ft or 1200 to 2250 m). The fire

began on 22 August 2006 and burned until 15 October 2006. Due to the size of the fire and the long

burning period, the use of remote sensing benefited the BAER team as it made its rapid assessment.

The following figures show the pre- and post-fire imagery (figs. D1 and D2), the BARC layer

(fig. D3), and the field-adjusted final soil burn severity map created by the BAER team (fig. D4).

Figure D1. Pre-fire Landsat imagery of the Derby Fire acquired 2 September 2003. The fire perimeter is the 

black outline.
46 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Figure D2. Post-fire Landsat imagery of the Derby Fire acquired 18 September 2006. The fire perimeter is 

the black outline.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 47

Figure D3. Initial BARC map of the Derby Fire. Preliminary BARC thresholds were 0-75 (unburned / very low); 

76-130 (low); 131-187 (moderate); and 188-255 (high). The fire perimeter is the black outline.
48 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010

Figure D4. Final field-adjusted soil burn severity map of the Derby Fire. In order to achieve an acceptable 

classified image, the BAER team had to separate the forest lands from the grasslands and classify each 

vegetation type separately. The field observations indicated that the BARC overestimated high and moderate 

soil burn severity. Final BARC thresholds used by the BAER team were 0-75 (unburned/very low); 76-160 

(low); 161-214 (moderate); and 215-255 (high). The final severity map shows smaller patches of both high 

and moderate severity while increasing the low severity. The BAER team clipped the soil burn severity layer 

to the fire perimeter.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-243. 2010 49

Appendix E—Summary of Soil Burn Severity Class Factors

Adapted from the BAER Handbook (USDA 1995) by Alex Janicki.

Factor 

considered

Soil burn severity class

Low Moderate High

Aerial view of 

canopy

Tree canopy largely 

unaltered.

Shrub canopy intact and 

patches of scorched 

leaves not dominant. Ash 

is spotty.

Tree canopy is scorched over 

50% of area. Shrubs mostly 

charred but difficult to assess 

fuels from air. Black ash is 

visually dominant. Gray or white 

ash may be spotty.

Tree canopy is largely consumed 

over > 50% of area. Shrubs 

completely charred but difficult to 

assess fuels from air. Gray and 

white ash is visually dominant.

Vegetation

Trees

Shrubs

Fine fuels 

(Grassland)

Nearly all of crown 

remains “green.” Some 

scorching in understory 

trees.

High scorch height. Generally, 

> 50% of crown is scorched. 

Mostly “brown” crowns with intact 

needles.

No needles or leaves remaining. 

Some or many branches may 

be consumed. Mostly “black” 

remaining vegetation.

Scorching in canopy but 

leaves remain mostly 

green. Limited fire runs 

with higher scorch. 5 to 

30% charred canopy.

30 to 100% charred canopy. 

Smaller branches < 0.5 inch 

(1 cm) remain. Shrub density was 

moderate or high.

90 to 100% charred canopy. Most 

branches consumed, including 

fuels < 1 inch (2.5 cm). Skeletons 

or root crowns remain. Shrub 

density was moderate or high. 

Often old growth in character.

Scorched or partially 

consumed.

Mostly consumed. Appears black 

from the air. Small roots and seed 

bank remain intact and viable.

Not rated as high unless loss of 

seed bank is suspected or soil 

structure strongly altered.

Ground cover

Generally, > 50% litter 

cover remains under 

trees—less under shrub 

community or where prefire cover is sparse.

Generally, 20 to 50% cover 

remains or will be contributed 

by scorched leaf fall from 

trees. Shrub litter will be mostly 

consumed.

0 to 20% cover remains as 

burned litter and woody debris 

under trees. Shrub litter is 

consumed.

Water 

repellency

Soils may be naturally 

water repellent under 

unburned chaparral. Other 

soils will infiltrate water 

drops in less than 10 sec; 

greater than 8 mL min–1

with the MDI.

The surface of the mineral soil 

below the ash layer may be 

moderately water repellent but 

water will infiltrate within 10 to 40 

sec; 3 to 8 mL min–1 with the MDI.

Strongly water repellent soils 

(repels water drops for > 40 

seconds; less than 3 mL min–1

with the MDI) may be present at 

surface or deeper.

Soil

Original soil structure—

fine roots and pores are 

unaltered.

Original soil structure—roots 

and pores slightly altered or 

unaltered. Soil color darkened or 

charred at surface or just below 

surface only.

Soil structure to 1 inch is 

degraded to powdery, singlegrained, or loose. Fine roots are 

charred. Pores are destroyed. 

Black charred soil color common 

below thick ash layer. Compare 

with unburned.


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