Idaho Forestry Best 

Forest Service 

Intermountain 

Research Station 

Management Practices: 

General Technical 

Report INT-GTR-339 Compilation of Research 

October 1996 on Their Effectiveness 

Kathleen A. Seyedbagheri 
The Author 

Kathleen A. Seyedbagheri is a Hydrologist at the Intermoun-. 

tain Research Station's Forestry Sciences Laboratory in Boise, 

ID. She attended Boise State University, the University of Notre 

Dame, and Utah State University, and holds bachelor's degrees in anthropology, mathematics, and watershed science. 

She received an interdisciplinary master's degree in environmental studies in 1994. She served as a forestry aide, forestry 

technician, and hydrologic technician at the Boise Laboratory 

between 1974 and 1980, and has been in her present position 

since 1980. 

Research Summary 

A search was conducted for quantitative ldaho research 

results on the effectiveness of the ldaho Forest Practices Act 

rules and regulations pertaining to timber harvest and forest 

road construction and maintenance. These rules and regulations are designated as the "best management practices" for 

the prevention of nonpoint source pollution from silviculture 

under provisions of the Federal Clean Water Act. For each 

practice, the relevant research results are summarized; more 

general summaries for related groups of practices are also 

provided. 

I would like to thank my cooperators at the ldaho Division of 

Environmental Quality (DEQ): Geoff Harvey, Steve Bauer, 

Donna Rodman, and Bob Steed. Michael Mclntyre of the 

Division of Environmental Quality took special interest in the 

project; his suggestions and time were greatly appreciated. 

Special thanks go to my supervisors at the lntermountain 

Research Station: Walt Megahan, Jack King, and Jim Clayton, 

for sharing their extensive knowledge of "best management 

practices" research and for providing their support during this 

project. 

I am particularly grateful to Dannielle Treadwell of the Intermountain Research Station for her cheerful assistance in many 

of the more tedious aspects of the effort. The Forest Service's 

FS INFO-Intermountain library system in Ogden, UT, and the 

University of ldaho library in Moscow were of great help locating 

copies of publications. I would also like to thank Jim Colla of the 

ldaho Department of Lands for providing information on best 

management practices interpretation. The cooperation of Carla 

Wise, Jay O'Laughlin, and George Belt of the University of 

ldaho was appreciated. Finally, I would like to thank all those 

who offered personal and professional support, and the many 

contacts in government, industry, and academia who shared 

their time and expertise. 

Contents 

Page 

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

Background and Need ......................................................... 3 

The Best Management Practices Project ............................. 3 

Format .................................................................................. 4 

Rule 3. Timber Harvesting ................................................. 5 

Rule 3.c. Soil Protection ....................................................... 7 

Research Results by Best Management 

Practice ......................................................................... 9

Rule 3.d. Location of Landings, Skid Trails, 

and Fire Trails ............................................................. 17 

Research Results by Best Management 

Practice ....................................................................... 17

Rule 3.e. Drainage Systems .............................................. 18 

Research Results by Best Management 

Practice ....................................................................... 18 

Rule 3.f. Treatment of Waste Materials ............................. 20 

Research Results by Best Management 

Practice ....................................................................... 21 

Rule 3.9. Stream Protection ............................................... 22 

Research Results by Best Management 

Practice ....................................................................... 22 

Rule 3.h. Maintenance of Productivity and 

Related Values ........................................................... 24 

Research Results by Best Management 

Practice ....................................................................... 24 

Rule 4. Road Construction and Maintenance ................ 27 

Rule 4.b. Road Specifications and Plans ........................... 29 

Research Results by Best Management 

Practice ....................................................................... 33 

Rule 4.c. Road Construction .............................................. 46 

Research Results by Best Management 

Practice ....................................................................... 50 

Rule 4.d. Road Maintenance ............................................. 65 

Research Results by Best Management 

Practice ....................................................................... 68 

General Erosion Research Summary ............................. 77' 

References ...................................................................... 85 

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

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

Intermountain Research Station 

324 25th Street 

Ogden, UT 84401 
Idaho Forestry Best 

Management Practices: Introduction 

Compilation of Research 

on Their Effectiveness 

Kathleen A. Seyedbag heri 

I 

Rule 3. 

Timber Harvesting I 

Rule 4. Road 

Construction 

and Maintenance I 

General Erosion 

Research Summary I 

References I 
Introduction I 
Idaho Forestry Best Management Practices: Compilation of 

Research on heir Effectiveness 

Kathleen A. Seyedbagheri 

Background and Need 

In 1972, Section 208 of the Federal Clean Water Act 

Amendments established the regulatory framework 

for nonpoint source pollution control through use of 

"best management practices" (BMPs). The responsibility for developing BMP's was delegated to the States. 

Best management practices are defined in the Idaho 

Water Quality Standards and Wastewater Treatment 

Requirements (Idaho Administrative Procedures Act 

16.01.2003,01) as "a practice or combination of practices determined by the Department [of Health and 

Welfare] to be the most effective and practicable means 

of preventing or reducing the amount of pollution 

generated by nonpoint sources" (Idaho Department of 

Health and Welfare 1989). 

Idaho was among the first five States to adopt a 

comprehensive modern forest practices act in 1974 

(Henly and Ellefson 1986). The act's purpose was to 

provide authority for rules "...designed to assure the 

continuous growing and harvesting of tree species and 

to protect and maintain the forest soil, air, and water 

resources, and wildlife and aquatic habitat" (Idaho 

Forest Practices Act, Title 38, Chapter 13, Idaho 

Code). Regulated forest practices include timber harvest, road construction and maintenance, reforestation, use of chemicals, and slash management. 

Rules and regulations (Idaho Administrative Procedures Act 20.15) are drafted by a Forest Practices 

Advisory Committee consisting of eight members representing forest land or timber owners, timber operators, fisheries biologists, and informed citizens. Exofficio members include representatives of the Idaho 

Division of Environmental Quality, the U.S. Department of Agriculture, Forest Service, the Idaho Farm 

Bureau, nonindustrial forest landowners, environmental groups, and resource consultants. Executive 

authority over the rules and regulations is held by the 

Idaho Board of Land Commissioners, which includes 

the Governor, attorney general, secretary of state, 

state auditor, and superintendent of public instruction. Rules and regulations are reviewed yearly and 

changes are made as necessary. The first set of rules 

and regulations was issued in 1976. 

The Idaho Forest Practices Water Quality Management Plan was completed in 1979 in accordance with 

Section 208 of the Federal Clean Water Act. This plan 

identified the rules and regulations associated with 

the Idaho Forest Practices Act, with recommended 

modifications, as the approved silvicultural BMP's. 

The Idaho Division of Environmental Quality is delegated authority to implement the Section 208 requirements, with primary responsibility for evaluating whether the BMP's adequately protect beneficial 

uses. The Idaho Department of Lands is the designated management agency for State and private lands. 

The Forest Service and the U.S. Department of the 

Interior, Bureau of Land Management are the designated management agencies for Federal lands. In 

1980, the Idaho Water Quality Standards were 

amended to identify the Forest PracticesrAct rules and 

regulations as the silviculturd BMP's for Idaho (Idaho 

Department of Health and Welfare 1985,1989). 

Although Idaho had regulated forest practices 

through the Forest Practices Act rules and regulations 

since 1976, and although much research had been 

done in Idaho related to the effectiveness of various 

BMP's, this research had never been assembled. The 

Division of Environmental Quality entered into Collection Agreement INT-9084CA with the Forest Service's Intermountain Research Station in Boise to locate 

and assemble the available Idaho researchinformation; 

this report is based on the results of that project. 

The Best Management Practices 

Project 

According to the agreement, only quantitative research data collected in Idaho were to be used, and 

only BMP's inRules 3 and4 (Timber Harvest andRoad 

Construction/Maintenance) were to be evaluated. This 

was solely a compilation of existing research, not a 

new research study. The requirement that only Idaho 

data were to be used had advantages and drawbacks. 

The advantages were in limiting the project's scope 

and in making sure the data had direct applicability. 

The disadvantage was that a great deal of research 

done in other States was automatically eliminated 

from consideration. 

The forest practice water quality BMP's in RuIes 3 

and 4 were subdivided into individual components to 
the extent possible. A search for Idaho research results on these individual BMP7s was conducted. This 

included literature searches as well as personhl contacts with individuals representing State and Federal 

agencies, universities, private industry, and others. 

A bibliography of potentially useful references was 

established. References in the bibliography (including 

literature citations) were screened for applicability. 

Generally, research measurements onsite or at a nearby 

downstream point were required. Although instream 

monitoring studies are useful, they seldom provide a 

direct measure of the effectiveness of a particular 

BMP, due to complex channel processes and cumulative effects. For each individual BMPlistedunder each 

subrule, the information relevant to that BMP was 

extracted from the references and included in the 

report. 

The literature searches and interviews revealed 

that little BMP effectiveness research had been done 

in Idaho with the exception of the work done by the 

Intermountain Research Station. (The Station has 

done research on the effects of various logging and 

road construction techniques since the 1950's.) 

Fewer than 100 references that actually give quantitative effectiveness data on specific BMP's were 

found; the majority of these were based on Intermountain Research Station data. Many BMP7s have not 

been researched at all in Idaho. Many studies had 

important implications for various BMP's, but did not 

provide quantitative effectiveness data. For each BMP, 

this report gives effectiveness data when available, 

and may also give relevant information from other 

research studies.This report includes both English 

and metric units of measure, depending on the units 

used in the original research. 

The first draft of this report was completed in July 

1992. Therefore, relevant research reports written in 

1992 or afterward are generally not included in this 

report. 

Format 

BMP Summaries 

Individual BMP's from Rules 3 and 4 of the April 

1990 Rules and Regulations are listed sequentially in 

the report. Each is identified by its subrule designation within the rules and regulations (for example, 

Rule 4.c.vii.i). These designations are not unique, because several BMP's might be listed under a given 

subde. Therefore, each BMP was also assigned allnique 

sequential number to facilitate cross-referencing. These 

numbers have no significance outside this report. The 

wording of the BMP's is not taken verbatim from the 

Forest Practices Act Rules and Regulations; refer to 

the Rules and Regulations for exact wording. 

More recent versions of the Rules and Regulations 

(May 1992) included a few rules (regarding culvert 

size and winter operations) that were not included in 

this report, they were not promulgated when the 

literature searches were conducted. Other rules may 

have been added since that time or may be addedin the 

future. For the most part, however, the rules remained 

constant over the course ofthis project. Insertion ofthe 

culvert size rule resulted in a renumbering oftwo rules 

following it (stream crossings and reuse of existing 

roads). The old numbering system is used in this 

report, these rules are designated 4.b.vi. and 4.b.vii., 

respectively. The winter operations rules were added 

at the end of the road maintenance section, and no 

renumbering of old rules was involved. Although neither culvert size nor winter operations were included 

in the literature search, I do not recall seeing any 

Idaho research on these topics. 

For each BMP, all research studies considered relevant to it are listed in chronological order (and alphabetically by author within years). The authors and 

date are listed first, followed by the study site location. 

Background information on the study and relevant 

research results are summarized. Page numbers are 

given. Although this is somewhat of a departure from 

the usual scientific reporting style, I felt that this 

format would be most useful in a reference context. 

Following all the listing of research studies for an 

individual BMP, cross-references may be provided. At 

the beginning of each subrule (Rule 3.c., Rule 3.d., 

etc.), a summary of the section is provided. 

General Erosion Research Summary 

The most common cross-reference is to the General 

Erosion Research Summary. This section follows the 

BMP summaries. The research studies summarized 

there have implications for one or more of the BMP's, 

but may not address any particular BMP directly. 

Parts of the information presented there, or other 

information from the same reference, may also appear 

under specific BMP's. The information in this section 

generally addresses general erosion processes, time 

trends, or seasonal trends. Because this section was 

not anticipated during the literature search, only 

general information from references that met the 

original screening criteria is included. 

References 

The last section of the report lists complete references for all citations. When applicable, the BMP's 

where the reference was cited are listed. 
Rule 3. Timber Harvesting 
Rule 3.c. Soil Protection 

Nine BMP's (1 through 9) were evaluated. BMP 1 is 

general rule 3.c.: "For each harvesting operation, select the logging method and type of equipment adapted 

to the given slope, landscape, and soil properties in 

order to minimize erosion." 

The remaining BMP's are more specific, and deal 

with six major concepts: 

Choice of yarding system, specifically, ground 

versus aerial yarding (BMP's 2 and 3); 

Skid trail gradient (BMP 4); 

Skid trail width (BMP 5); 

Number of skid trails (BMP 6); 

Tractor size (BMP 7); 

Uphill versus downhill cable yarding (BMP 8) and 

downhill yarding techniques (BMP 9). 

Ground Skidding Versus Aerial Yarding 

In addition to yarding method, BMP's 2 and 3 also 

address soil properties (stability, saturation, ease of 

compaction, and erosion potential), slope gradient 

(less than or greater than 45 percent), and proximity 

to streams. 

Twenty references were found that address direct or 

indirect impacts for different yarding systems. Of 

these, only one (Carlton and others 1982) actually 

tested for ground skidding versus aerial yarding. This 

study found no significant difference in onsite surface 

erosion between skyline- and tractor- logged areas, or 

even between logged and unlogged areas in the Gospel 

Hump area near Grangeville (p. 18). The percentage of 

bare ground was the best predictor of surface erosion 

on logged and unlogged areas, regardless of yarding 

method (p. 23). 

Seven other references addressed surface erosion 

associated with various yarding systems. Arnold and 

Lundeen (1968) evaluated skid trail erosion in the 

South Fork Salmon River drainage. The estimated 

average annual erosion depth for 5 years after crawler 

tractor logging was 0.1 foot (p. 138). McGreer (1981) 

measured 1-year erosion rates on skid trails near the 

town of Headquarters. The values varied from 0.003 to 

0.583 inches, depending on exposure of subsoil, cover 

provided by litter or slash, and skid trail gradient (p. 9). 

No significant difference in onsite surface erosion 

was found between skyline and jammer systems in 

research reported by Packer (1966, p. 695) and by 

Megahan and Kidd (1972b, p. 139). Megahan and Kidd 

noted, however, that the skyline system in this study 

was not used under optimal conditions. Each logging 

system increased sedimentation in ephemeral drainages by 0.6 times natural rates over a 7-year period 

(Megahan and Kidd 1972b, p. 140). 

Research in the Silver Creek Study Area in the 

Middle Fork of the Payette River drainage evaluated 

surface erosion associated with helicopter logging and 

broadcast burning (Clayton 1981; Megahan 1987; 

Megahan and others 1995). Clayton (1981, p. 6) reported that accelerated erosion in the first 2 years 

after logging was limited to 2 percent of the cutting 

unit area. He estimated that 40 to 60 percent of the 

erosion volumes of 6.0 and 4.0 tons per acre in the first 

and second years (respectively) were due to mechanical disturbance associated with logging (pp. 5-6). The 

total erosion volumes represented an increase over 

natural erosion of about one order of magnitude (p. 6). 

Megahan and others (1995) reported accelerated sedimentation (averaging 97 percent) at the watershed 

mouth persisting for 10 years after treatment. However, this increase was primarily attributed to the 

effects of broadcast burning on the harsh south aspect 

Idaho Batholith site. 

Soil disturbance is an indicator of the potential for 

surface erosion. However, soil disturbance is also 

considered beneficial for conifer regeneration under 

some circumstances. Six studies investigated soil disturbance associated with various yarding systems. 

Tractor and tractor-jammer units in the South Fork 

Salmon River drainage had 88 percent of transect 

points disturbed, and 40 percent of the points had bare 

soil (Krassel Ranger District 1983, p. 9). 

In the Silver Creek Study Area, Clayton (1990, p. 3) 

reported soil displacement on 33.5 and 28.5 percent of 

the total area ofunits logged with crawler tractors and 

rubber-tired skidders, respectively. Helicopter logging in the study area caused soil mixing on less than 

3 percent of the cutting unit area (Clayton 1981, p. 6). 

Leverick (1980, pp. 91-94) and Rummer (1982, p. 

107) evaluated mineral soil exposure associated with 

use of a rubber-tired miniskidder in the University of 

Idaho Experimental Forest near Moscow. In both 

studies, soil was exposed on about 12 percent of the 

area. Bellito's research in the same forest (1985, pp. 

39-41,46,49,69) found that deep soil disturbance was 

generally limited to the corridors for both the KoIler 

(skyline) and KWIK (jammer or high lead) yarding 

systems. He felt erosion potential was greater on the 

KWIK units due to a greater number of corridors; 

disturbance due to the Koller system could be controlled to accommodate natural regeneration. 

Mass erosion due to yarding systems is less of a 

concern than is surface erosion. However, a general 

statement in one publication could be interpreted to 

address this issue. Based on a survey of landslides in 

the Middle Fork Payette River and on the Clearwater 

National Forest, Megahan and others (1979, p. 132) 

recommended that logging methods minimize disturbance to the understory to reduce mass erosion 

frequency. 
Soil compaction may decrease productivity or increase erosion. Seven studies were found that evaluated compaction effects ofvarious yarding systems. In 

the University of Idaho Experimental Forest Bellito 

(1985, pp. 36,46-47, 59) found minimal or no significant compaction associated with cable logging (Koller 

or KWIK yarders) in dry weather. However, in a 

shelterwood cut logged during wet weather with the 

KWIK ground lead (double drum jammer configuration), 21 percent of the area was compacted (a bulk 

density increase of 0.12 grams per cubic centimeter in 

the corridors), and productivity losses could be expected. The Koller skyline did not cause compaction in 

wet weather logging except when the skyline cable 

was not high enough above the slope to keep the logs 

from dragging on the ground. A single drum jammer 

near the town of Smith's Ferry resulted in significant 

compaction on the disturbed areas, with a bulk density 

increase of 0.29 grams per cubic centimeter or 37.6 

percent. Reduced productivity was expected (Bellito 

1985, p. 38). 

In the South Fork Salmon River drainage, an average of 40 percent of sampling points on tractor and 

tractor-jammer logged units appeared to be compacted. 

The compacted sites showed a 26 percent increase in 

bulk density, with some loss of productivity expected 

(Krassel Ranger District 1983, p. 9). 

Clayton (1990, pp. 3-4) measured bulk density 

changes associated with crawler tractors and rubbertired skidders operating in the Silver Creek Study 

Area near Crouch. He found significant increases in 

bulk density, ranging from 15 to 29 percent, on all 

main and secondary skid trails; differences between 

the two skidder types were not significant. Productivity losses due to compaction were expected on at least 

two of the three cutting units sampled. A landing in 

one of the units showed a 32 percent increase in bulk 

density. 

Lenhard (1978, pp. 10,13) found significant changes 

in bulk density (14 to 34 percent) associated with 4 to 

32 passes of a rubber-tired skidder on volcanic-ash 

influenced soils near Potlatch; one to two passes did 

not result in statistically significant changes. 

Leverick (1980, pp. xv, 91) and Rummer (1982, pp. 

64, 83, 105) assessed the impacts of rubber-tired 

miniskidders operating in the University of Idaho 

Experimental Forest. Three of four stands had significant increases in bulk density on skid trails. However, 

the skid trails covered only 5 to 7 percent of the stand 

area; compaction was limited to the upper 6 inches of 

the soil profile; the bulk density values were in the 

lower half of the critical range, or that range of estimated threshold values for root growth inhibition. 

Therefore, productivity losses were expected to be 

minimal. 

Froehlich and others (1985, pp. 1016-1017) showed 

significant and long-lasting compaction associated 

with ground skidding on volcanic and granitic soils 

near McCall, for periods ranging from 0 to 25 years 

after logging and for soil depths from 5.1 to 30.5 

centimeters. Initial compaction was about twice as 

much on volcanic soils; recovery rates were similar on 

the two soil types. 

The most important consideration in the choice of 

yarding system may be the road system required for 

support. Several papers addressed the indirect effects 

related to supporting road systems. Packer (1966, p. 

695) and Megahan and Kidd (197213, p. 140) reported 

that roads supporting jammer logging resulted in 

much higher total erosion rates from a jammer-logged 

watershed than &om a skyline-logged watershed with 

no roads. Kidd and Kochenderfer (1973) noted that 

jammers required parallel roads every 200 to 400 feet, 

the corresponding figure for mobile spars for skyline or 

high lead logging was 1,500 to 2,000 feet. Burroughs 

and others (1972, p. 11) reported jammer densities 

exceeding 10 linear miles per square mile, and stressed 

the critical need to provide proper drainage for the 

overland flow and subsurface seepage intercepted by 

the roads. 

Megahan (1988, p. 337) summarized existing research to compare the percent of area in roads for 

various logging systems. The percent of the area in 

roads ranged from 2.6 to 3.9 percent for skyline logging, from 1.0 to 4.3 percent for tractor logging, and 

from 25 to 30 percent for jammer logging. Hartsog and 

Gonsior (1973, p. 13) observed that tractor and jammer skidding can cause disturbance and damage to 

road prism components, (cutslope, fillslope, tread, and 

ditch), and prevent correct functioning of the road 

drainage system. 

Skid Trail Gradient 

Best management practice 4 says that skid trail 

gradient should be limited to a maximum of 30 percent 

on geologically unstable, saturated, highly erodible, or 

easily compacted soils. Two Idaho studies evaluated 

skid trail gradient on three soil types: granitic, basalt, 

and volcanic ash cap. McGreer (1981, p. 6) measured 

l-year surface erosion rates on skid trail plots near 

Headquarters. For comparable plots, increases in slope 

from 15 percent to 40 or 45 percent increased erosion. 

At the steeper gradients, erosion increased by factors 

of 1.2 for the ash-with-litter plots, 1.7 for the ashwithout-litter plots, and 3.7 for exposed subsoil plots. 

However, the effects of the soils, litter, and slash 

variables were much greater than those of slope. 

In Kidd's study on four sites in west-central Idaho 

(1963, pp. 4-5) slope gradient class (20 to 30,40 to 50, 

or 60 to 70 percent) was not sigzllficant in the analysis 
of variance of quantitative erosion data. However, the 

interaction of soil (basalt or granitic) and slope gradient was significant in analysis of qualitative ratings of 

erosion control structure effectiveness. Kidd (1963, p. 

6) recommended spacing erosion control structures 

more closely as skid trail gradient increased. Kidd's 

study (1963, pp. 4-5) showed that more skid trail 

erosion occurred in ravines than on hillsides, and that 

skid trail erosion was greater on soils derived from 

granite than on those derived from basalt. 

Skid Trail Width and Number of Skid Trails 

In an early study in the Boise Basin Experimental 

Forest near Idaho City, reported by Haupt (1960, pp. 

635-638) and Haupt and Kidd (1965, pp. 665, 668), 

skid trails were reused whenever possible. Ninety 

percent of skid trail areas had 50 percent or more 

mineral soil exposed. However, skid trail soil disturbance is beneficial for regeneration of ponderosa pine. 

Most of the material eroded from skid trail surfaces 

was contained in erosion control structures; skid trails 

stabilized within 4 years. In some cases, there were 

tradeoffs between area in skid trails and area in roads. 

Road erosion was a much greater source of stream 

sedimentation, and roads provided poorer sites for 

regeneration. 

Based on his research on skid trail surface erosion 

rates on volcanic ash cap soils near Headquarters, 

McGreer (1981, p. 10) recommendedlirnitingthewidth 

of blading of skid trails due to higher erosion rates on 

exposed subsoils and on soils without litter or slash 

layers. Clayton (1990, p. 7) and Froehlich and others 

(1985, p. 1017) recommendedlimiting the total areain 

skid trails due to the significant levels of soil compaction observed on skid trails on granitic and volcanic 

soils. 

Clayton (1990, pp. 2,4) found no significant difference in bulk density between main and secondary skid 

trails (where secondary skid trails had an estimated 3 

to 10 passes), for either rubber-tired skidders or crawler 

tractors. Lenhard (1978, pp. 10,22) found significant 

changes in bulk density on volcanic-ash influenced 

soils near Potlatch after 4 to 32 passes ofarubber-tired 

skidder, but not after one to two passes. He recommended that skidder operators disperse their movements rather than concentrate them when working on 

similar soils. Similarly, Leverick (1980, pp. 88-89) 

found that bulk densities increased with the number 

of passes (from 0 to 30) of a rubber-tired miniskidder, 

with the first 10 trips producing the greatest changes. 

Tractor Size 

Only one study actually compared the impacts of 

small andlarge tradors. In the Boise Basin Experimental 

Forest, Haupt (1960, pp. 636-638) found that bared 

areas averaged 34 acres per square mile in skid trails 

and 19 acres per square mile in haul roads for large 

tractors (D-8), compared to 17 acres per square mile in 

skid trails and 33 acres per square mile in haul roads 

for small tractors (D-4). The relationships between 

road area and skid trail area for the two tractor sizes 

varied among silvicultural systems; tractor size effects were not apparent for group selection but were 

for stem selection. 

Leverick (1980, p. 97) and Rurnmer (1982) tested 

rubber-tired miniskidders in the University of Idaho 

Experimental Forest. The Case-Davis Fleethoe 30 

was not durable enough for skidding small-diameter 

trees, but the Case-Davis DH-4 functioned adequately 

with minimal site impact (including compaction and 

soil disturbance). See BMP's 2, and 3 for details. 

Uphill and Downhill Cable Yarding 

No studies actually provided a quantitative comparison of uphill versus downhill cable yarding. 

Craddock(1967, p. 25) and Megahan and Kidd (1972a, 

p. 139) noted that downhill cable yarding in the Zena 

Creek Logging Study Area near McCall increased soil 

disturbance and surface erosion. Jensen and Finn 

(1966, pp. 8,32,59), based on their hydrologic analysis 

of the same study area, recommended that road building be limited largely to ridge tops on the decomposed 

granitic landtype. Logging on these areas would require uphill yarding or roadless logging systems. 

No references were found specific to BMP 9, lifting 

leading ends of logs when downhill cable yarding. 

Research Results by Best Management 

Practice 

BMP 1-Rule 3.c. For each harvesting operation, 

select the logging method and type of equipment 

adapted to the given slope, landscape, and soil properties to minimize erosion. 

See Rule 3.c.i. (BMP's 2 and 3) and Rule 3.c.iii., 

tractor size (BMP 7). 

BMP 2Rule 3.c.i. Use other than tracked or wheel 

skidding on geologically unstable, saturated, or easily 

compacted soils. 

BMP 3-Rule 3.c.i. Use other than tractor or wheel 

skidding on slopes exceeding 45 percent gradient and 

immediately adjacent to a class I or class 11 stream, 

unless the operation can be done without causing accelerated erosion. 

These two rules will be considered together, with 

slope gradients indicated. 

Packer 1966, Zena Creek Logging Study Area, Payette 

National Forest, 67 percent slope gradient-Erosion 

did not differ on lands logged with jammer and mobile 
spar high-lead systems 2 years after logging. However, the watershed logged with jammers had almost 

seven times more sediment in subdrainages beckuse of 

the road system needed to support the jammer (p. 695). 

See Megahan and Kidd (1972b) for this study's 

completion report. 

Arnold and Lundeen 1968, South Fork Salmon River, 

variable slopegradients, many in excess of 45percentAverage annual erosion on skid trails was estimated to 

be 0.1 foot for the first 5 years aRer crawler tractor 

logging (p. 138). 

Burroughs and others 1972, Idaho-Montana border 

near Lolo Pass, 23 percent slope gradient-Studies 

indicatedthat 1 mile of roadin the deep snowpackzone 

would intercept 310 acre-feet of overland flow and 

subsurface seepage during the spring snowmelt period. Draining the intercepted water is critical, especially in areas to be logged with jammers, because 

densities ofjammer roads offen exceed 10 linear miles 

per square mile (p. 11). 

Megahan and Kidd 1972b, Deep Creek Drainage, 

Zena Creek Logging Study Area, Payette National 

Forest (Control Watersheds Oompaul, Hamilton, 

Tailholt and Circle End Creeks), slope gradient 67 

percent-No significant difference was found in onsite 

erosion between skyline and jammer logging. Skyline 

logging probably caused more disturbance than usual 

because the slopes were straight to convex and because the logs were skidded downhill (p. 139). 

Jammer and skyline skidding increased sediment 

deposition in ephemeral drainages an average of 0.04 

tons per square mile per day from November 1960 to 

September 1967. This represented 0.6 times more 

sediment than measured on the control watersheds. 

However, the roads supporting the jammer logging 

caused large increases in sediment, 750 times that 

measured on the control watersheds (p. 140). 

Hartsog and Gonsior 1973, China Glenn Road, South 

Fork Salmon River drainage, Payette National Forest, 

most slopes less than 50percentgradient-Tractor and 

jammer skidding can cause disturbance and damage 

to road prism components (cutslope, fillslope, tread, 

and ditch) and prevent correct functioning of the road 

drainage system, thus causing serious sedimentation 

problems (p. 13). 

Kidd and Kochenderfer 1973, literature review, slope 

gradients not specified--Jammer logging required 

parallel contour roads every 200 to 400 feet (16 miles 

per section), mobile spar every 1,500 to 2,000 feet (3 

miles per section) (p. 285). 

Lenhard 1978, near Potlatch, slope gradient not 

specified-A Clark 666 rubber-tired skidder operating 

on volcanic-ash influenced soils produced significant 

changes (ranging i?om 14 to 34 percent) in bulk density 

after 4 to 32 passes; one to two passes did not produce 

significant changes (pp. 10, 13). Bulk densities increased from one to four passes; after four passes, bulk 

densities were relatively constant (pp. 15-16). Bulk 

densities did not differ significantly between the treatment year and 1 year afterward, except for the oneand four-pass treatments. The one-pass treatment 

showed an increase in bulk density between years, and 

the four-pass treatment showed a decrease (p. 11). 

Four passes may be a threshold beyond which rapid 

recovery does not occur (p. 17). 

The pore-size distribution index was significantly 

altered by all treatments except the one-pass treatment (p. 12). The data indicate a redistribution of flow 

channels for treatments with more than four passes 

(p. 18). This entails a reduction in macropores critical 

for plant growth and atration processes (p. 22). 

Megahan and others 1979, Clearwater National 

Forest and Middle Fork Payette River Drainage, Boise 

National Forest, variable slope gradients-Landslide 

occurrence tended to increase as either tree or shrub 

crown cover decreased. When crown covers were less 

than 80 percent, landslide occurrence appeared to be 

more sensitive to reductions in shrub crown cover than 

to reductions in tree crown cover. The authors recommended using timber harvest procedures that minimize the disturbance of understory vegetation (p. 132). 

Leverick 1980, University of Idaho Experimental 

Forest, West Hatter Creek and Flat Creek Units, slope 

gradient not specified-Soil compaction and soil disturbance were evaluated for a Case-Davis Fleethoe 30 

converted to a rubber-tired miniskidder for skidding 

small-diameter trees. On 13 percent of the area mineral soil was exposed enough for erosion to occur (pp. 

91-94). Bulk density increased significantly in the top 

2 inches of the most heavily traveled skid trail of the 

Flat Creek unit, but not at soil depths of 4 to 6 inches 

or 8 to 10 inches. This minimal effect on bulk density 

was attributed to dry soil conditions at the time of 

treatment (p. xv, 91). A controlled experiment on the 

West Hatter Creek unit (with soil moisture varying 

from 20.38 to 25.32 percent) indicated that compaction 

was limited to the upper 6 inches of soil (p. xv). 

Clayton 1981, Silver Creek Study Area, Control 

Creek Watershed, Boise National Forest, 30 to 50 

percent slope gradients-Helicopter yarding with 

broadcast burning accelerated erosion on 2 percent of 

the area, with a short-term increase in erosion volume 

of approximately one order of magnitude (p. 6). One 

year after logging, 40 percent of the 6.0 tons per acre 

oferosionvolume was attributed to mechanical disturbance associated with logging; 32 percent was attributed to burning; 19 percent was associated with 
disturbance but not attributed to a single cause; and 9 

percent was attributed to natural causes. During the 

following year, erosion volume was 4.0 tons per acre, 

with the percentages attributed to the various~causes 

about the same as in the first year (pp. 5-6). 

On 3 percent of the total area, soil horizon mixing 

was observed. This was attributed to a combination of 

rodent activity and mechanical disturbance associated with logging (p. 6). 

McGreer 1981, near Headquarters, slope gradients 

up to 60 percent, skid trailgradients 15 to 50percentOne-year erosion rates were measured on skid trail 

plots established with a D-6 Caterpillar tractor. The 

following tabulation was adapted from table 2, (p. 9): 

Skid trail 

gradient Soil cover 

Percent 

15 Ash with litter 

45 Ash with litter 

15 Ash without litter 

45 Ash without litter 

15 Exposed subsoil 

40 Exposed subsoil 

50 Subsoil covered with slash 

Erosion rate 

Tons/ Area 

acre inches 

0.28 0.003 

0.30 0.004 

1.00 0.012 

1.86 0.022 

20.46 0.164 

72.60 0.583 

1.08 0.013 

McGreer defined "area inches" as follows: "Area 

inches assumes an even distribution of erosion throughout the area (plot), which in reality is seldom, if ever, 

the case. However, the measure is useful as an easy 

way to visualize the unit." 

The author concluded that "ash topsoils are resistant to erosion but exposure of underlying subsoils 

results in erosion rates severe enough to reduce longterm soil productivity and to create stream sedimentation. Organic litter or slash effectively prevent erosion." [Abstract] 

Plots with ash horizons were approaching a zero 

erosion rate by the end of the first year (p. 6); although 

erosion rates were decreasing, erosion from plots with 

exposed subsoils was expected to remain high for at 

least the second year (p. 7). 

Recommendations (p. 10) included: 

Avoid bladed skid trails if possible 

Minimize width and depth ofbladingwhere blading 

is necessary 

Top and limb trees on skid trails to the extent 

feasible. 

Carlton and others 1982, Gospel Hump, slopegradients of logged plots varied from 9 to 53 percent-No 

significant differences in erosion rates were found 

between skyline- and tractor-logged plots, or between 

logged and undisturbed plots (p. 18). Surface erosion 

was adequately explained by a "percent bare ground" 

variable alone (p. 23). Predictive equations for seasonal erosion and recovery time for natural mitigation 

of accelerated erosion (versus percent bare ground) 

were developed (pp. 24-26). 

Rummer 1982, University of Idaho Experimental 

Forest, Hatter Creek and Flat Creek Units, slopes 10 to 

20 percent-A Case DH4 backhoe was converted to a 

rubber-tired miniskidder to be tested for removing 

thinning residues. Site impacts were evaluated as 

part of the study. Three of four stands showed significant increases in bulk density, confined to the upper 

6 inches of the soil profile on skid trails (that averaged 

5 to 7 percent of the total stand area). Average bulk 

density values for the upper 6 inches of soil on skid 

trails ranged from 1.11 to 1.43 grams per cubic centimeter, in the lower half of the critical range (undisturbed areas in the Flat Creekunits had bulk densities 

ranging from 0.93 to 1.12 grams per cubic centimeter 

in the upper 6 inches). Based on the depth, areal 

extent, and degree of compaction, the author concluded that there was minimal damage in terms of 

reduced site productivity (pp. 64,83,105). 

Soil disturbance studies showed that an average of 

79 percent of the total stand area (ranging from 70 to 

89 percent) was in the categories "undisturbed" or 

"litter disturbed but still in place" (p. 107). 

This study is a followup to Leverick (1980) and 

incorporates some of Leverick's data. 

Krassel Ranger District, Payette National Forest 1983, 

Teapot Timber Sale, fiassel Ranger District, Payette 

National Forest, slope gradients rwt specifid-Line 

transects of three tractor- and tractor-jammer logged 

units showed 81 to 100 (average 88) percent of the 

sampling points were disturbed, 14 to 54 (average 40) 

percent had bare soil (compared to 2 percent in undisturbed control transects), and 30 to 47 (average 40) 

percent appeared to be compacted. The compacted 

sites showed a 26 percent increase in bulk density. 

Some loss of productivity was expected as a result of 

compaction (p. 9). 

Bellito 1985, Flat Creek Unit of the University of 

Idaho Experimental Forest, slope gradient 20 to 40 

percent, and near Smith's Ferry, slope gradient 80 to 

100percent4te impacts, including compaction and 

soil disturbance, were evaluated for a Koller Model 

K-300 (small skyline yarder), and for a KWIK yarder 

rigged as a ground lead (double drum jammer) and as 

a live skyline (in effect a high lead) on the experimental forest. Compaction associated with use of a single 

drum jammer near Smith's Ferry was also evaluated. 

No appreciable compaction occurred during dry 

weather cable yarding with either the Koller or the 

KWIK (clearcuts in units 1,2, and 3 of the experimental 
forest). Some compaction did occur in the Koller corridors but the area of impact was limited to about 1 

percent of the total unit (pp. 46-47). For the two 

clearcut units yarded with the Koller skyline, there 

was a small (0.07 grams per cubic centimeter) but 

significant (alpha = 0.10) increase in bulk density at 

the corridor centers. Bulk density changes were not 

significant at 5 or 10 feet on either side of the corridor 

centers (pp. 35, 62). In the worst case, this would be 

only 1.2 percent of the total area of the unit having 

significant compaction (pp. 35,36,62). The author felt 

that no productivity losses due to compaction occurred 

in the units logged in dry weather (p. 46). 

However, compaction was apparent on units logged 

during wet weather (shelterwood in units 4 and 5 of 

the experimental forest). The section yarded with the 

KWIK ground lead had a measured bulk density 

increase of 0.12 grams per cubic centimeter in the 

corridors, which was significant at alpha = 0.05. Because the ground lead logging system required more 

skidding corridors than the skyline system, 21 percent 

of the total area of the ground lead section was compacted, which would probably result in a loss of productivity(~. 36,46,59). CompactionintheKollerskyline 

section of the shelterwood was limited to one corridor 

where lack of deflection resulted in a yarding situation 

similar to a ground lead (p. 46). Higher soil moisture 

contents during the ground lead yarding may have 

contributed to the differences in compaction (p. 46). 

All of the experimental forest units except one of two 

Koller clearcuts had enough exposed mineral soil to 

accommodate natural regeneration. Deep disturbance 

was generally limited to the corridors (p. 46). Concentration of disturbance in the numerous corridors of the 

clearcut unit yarded with the KWIK skyline resulted 

in a higher potential for erosion and sedimentation 

than in the Koller clearcuts, even though one of these 

had significantly more exposed mineral soil (pp. 39-41, 

69). 

At the Smith's Ferry site, bulk density increased 

0.29 grams per cubic centimeter (37.6 percent) in 

areas where the single drum jammer was used. Bulk 

densities of samples from the logged area were significantly higher (alpha = 0.05) than samples from adjacent undisturbed areas. It was concluded that reduced 

productivity was likely (p. 38). 

The author concluded that the Koller skyline was 

preferable to the ground lead systems in this study, 

because it caused no significant compaction on either 

wet or dry soils when used properly, and had the 

capability of creating the desired degree of soil disturbance depending on site conditions (p. 49). 

Froehlich and others 1985, two sites near McCall, 

s1opegradients:granitic soils 10 to 45percent; volcanic 

soils 10 to 35 percent-Bulk densities of granitic 

and volcanic soils were evaluated on skid trails of 

ground-skidded, partial-cut areas, and nearby undisturbed areas. Samples were taken at depths of 5.1, 

15.2, and 30.5 centimeters at sites rangingfrom 0 to 25 

years since logging (sampled in 5-year age classes). 

Compaction was significant and highly persistent 

on both soil types. The only samples showing full 

recovery were the three oldest age classes at a depth of 

5.1 centimeters on granitic soils. Nearly all other age 

classes and soil depths showed highly significant differences (p < 0.01) between skid trails and undisturbed 

areas, for both soils. A trend toward recovery was 

indicated by a significant relationship between time 

since logging and differences in bulk density (skid trail 

versus undisturbed) for all but one combination of soil, 

age, and depth. Recovery was faster at the 5.1 centimeter depth than at the other depths sampled (pp. 1016- 

1017). 

The difference in bulk density between skid trails 

and undisturbed areas was significantly greater (p < 

0.01) on the volcanic soils than on the granitic soils. 

Initial compaction (percent difference in bulk density 

between skid trails and undisturbed areas) was significantly (nearly two times) greater on the volcanic 

soil than on the granitic soil, but recovery rates for the 

two soil types were not significantly different. Therefore, the volcanic soils can be expected to take longer 

to achieve full recovery (p. 1017). 

Megahan 1987, Silver Creek Study Area, Control 

Creek and Eggers Creek Watersheds, Boise National 

Forest, average slope gradient 50 percent-& helicopter yarding and prescribed burning, annual sediment yields increased sigmficantly (based on a paired 

watershed study). The increases, averaging 100 percent, continued to persist 9 years after logging. Years 

with the highest sediment yields in the control watershed showed the greatest acceleration of sedimentation in the logged watershed. The increases in sediment were attributed to surface and mass erosion in 

the cutting units; no increases were measured in 

channel erosion or streamflow (p. 260). 

This paper does not separate logging and burning 

effects; see Clayton (1981) and Megahan and others 

(1995) for estimation of the relative influences of 

logging and burning. Megahan and others (1995) is a 

more complete report of the same study. 

Megahan 1988, literature review, variable slope 

gradients-The amount of area in roads, skid trails, 

and landings for various logging systems was compared, based on published studies. The Idaho data 

included: tractor-selection, tractor-group selection, 

tractor-partial clearcut, jammer-group selection, and 

skyline-partial clearcut. For tractor logging, the area 

in roads varied fkom 1.0 to 4.3 percent, and the area in 

skid trails varied fkom 6.7 to 6.8 percent. For jammer 

logging, 25 to 30 percent of the area was in roads. For 
skyline logging, 2.6 to 3.9 percent of the area was in 

roads (p. 337). 

Clayton 1990, Silver Creek Study Area, Central 

Watersheds, Boise National Forest, slope gradients 

generally less than dopercent-Three sites were studied for impacts of ground skidding on soils: one with a 

designated main skid trail, logged by Caterpillar tractor; one with a designated main skid trail, logged by 

rubber-tired skidder; and one 'loggers' choice," with no 

restrictions other than adhering to BMP's. 

$oil displacement was evaluated for main and secondary skid trails, landings, firelines, and "other" 

categories. Total soil displacement was similar for the 

three units, but the distribution among the categories 

varied. The loggers' choice unit had the least skid trail 

disturbance due to its more circular shape. Total skid 

trail disturbance was equal for the skidder and tractor 

units (25 percent); however, there was less displacement in the "other" category for the skidder unit (3.5 

percent) than for the tractor (8.5 percent) and loggers' 

choice (10 percent). This difference was attributed to 

the additional displacement associated with maneuvering the tractor. Total area with soil displacement 

was 33.5 percent for the tractor unit, 28.5 percent for 

the skidder unit, and 27 percent for the loggers' choice 

unit (p. 3). This can be compared with 1.5 percent 

displacement (exclusive of landings constructed away 

from cutting units) associated with helicopter logging 

in the adjacent ControlCreekwatershed(C1ayton 1981). 

Significant increases (ranging from 15 to 29 percent) 

in bulk density occurred in all skid trail areas of each 

unit. A significant increase (32 percent) in bulk density also occurred in the landing of the loggers' choice 

unit (the only landing included in the study). Other 

areas showed only slight changes in bulk density 

(pp. 3,4). Differences between bulk densities on tractor and skidder skid trails were not statistically significant at the 95 percent level (p. 6). 

Penetrometer measurements of the tractor and 

skidder main skid trails and the loggers' choice landing (the only areas tested) all showed significant 

changes in both surface (0 to 7.5 centimeters) and 

subsurface (7.5 to 17.5 centimeters) soils (p. 5). 

The author concluded that multiple passes with 

either type of ground skidder (rubber-tired skidders or 

crawler tractors) resulted in significant soil compaction on coarse-textured granitic soils. On at least two 

of the three cutting units, the increases in bulk densities for skid trails and landings fell into the monitoring 

category of "detrimentally compacted," and productivity losses might be expected. In the third unit, the 

value fell outside the 95 percent confidence interval. 

The author recommended the following techniques 

to minimize the area impacted by ground skidding: 

Restrict skidding to marked trails 

Require directional felling 

Encourage operators to string cables'to logs instead of driving to them. 

Megahan and others 1995, Silver Creek Study Area, 

Control Creek and Eggers Creek Watersheds, Boise 

National Forest, cutting unit gradients 24 to 97 percent, averaging 47 percent-For the 10 years after 

(clearcut) helicopter logging and prescribed burning, 

total sediment yield increased significantly (p < 0.05), 

an average of 97 percent. Greatest effects were observed during years with the highest sediment yields. 

Active erosion within the cutting units was the 

apparent source of the accelerated sediment. One 

progressive mass failure contributed a maximum of 6 

percent of the total. The remainder was attributed to 

accelerated surface erosion resulting from exposure of 

bare soil on the cutting units. Vegetative cover of 

shrubs and herbs was still below predisturbance levels 

10 years after logging; this was due to the effects of 

prescribed burning on the harsh south aspect Idaho 

Batholith site (pp. 22-24). Accelerated erosion and 

sedimentation generated by prescribed burning on 

such sites tends to outweigh the benefits gained by 

helicopter yarding. 

The accelerated sedimentation in this study was 

primarily attributed to burning, not logging. This is a 

more complete report ofthe study described inMegahan 

(1987). 

See the General Erosion Research Summary for 

additional information. 

BMP &Rule 3.c.ii. Limit the grade of constructed 

skid trails on geologically unstable, saturated, highly 

erodible, or easily compacted soils to a maximum of 30 

percent. 

Kiolcl 1963, four sites on the Boise and Payette National Forests-Three sites were selectedwithg 

soil parent material, and one with Columbia River 

basalt soil parent material. Quantitative and qualitative evaluations were made of erosion on skid trail 

segments and effectiveness of various erosion control 

measures (slash dams, log water bars, lop-and-scatter 

slash). All skid trails were seeded after the control 

measures were applied. Skid trail slopes varied from 

20 to 90 percent (p. 2). 

The quantitative data were used to evaluate how the 

measured erosion volumes varied with slope gradient, 

structure spacing, and soil parent material. Slope 

gradient class (20 to 30,40 to 50, or 60 to 70 percent) was 

not found significant in the analysis of variance (p. 4). 

Analysis of the qualitative structure performance 

ratings indicated that more skid trail erosion occurred 

in ravines than on hillsides, and that all the structure 

types tended to be ineffective in ravines. This was true 

for both soil types. However, the structure rating 

value analysis showed that the basaltic soil skid trails 

showed less erosion than those on granitic soils, with 
the difference almost significant at the 1-percent level. 

This may be due to inherent erodibility and productivity characteristics (pp. 4-5). According to the 'author, 

"The structure rating values were lower on basalt; this 

suggests that basaltic soil is inherently less erodible 

and more productive in growing ground cover that is 

effective in controlling erosion." 

Statistical analysis ofthe qualitative ratings showed 

that the interactions of soil and structure treatment 

and soil and slope gradient were significant at a level 

between 1 and 5 percent. "This means that soil had a 

variable effect on the structure performance rating, 

depending upon the structure used and slope class" 

(p. 5). 

Based on two research studies and the experience of 

erosion control crews, the author recommended structure spacing by soil parent type (granite or basalt), 

slope gradient (10 to 70 percent), and topographic 

location (sidehill or ravine) (p. 6). 

McGreer 1981, near Headquarters-One-year erosion rates were measured on skid trail plots established with a D-6 Caterpillar tractor. Measured values, adapted from table 2 (p. 9), were: 

Skid trail 

gradient Soil cover Erosion rate 

~hns l Area 

Percent acre inches 

15 Ash with litter 0.28 0.003 

45 Ash with litter 0.30 0.004 

15 Ash without litter 1.00 0.012 

45 Ash without litter 1.86 0.022 

15 Exposed subsoil 20.46 0.164 

40 Exposed subsoil 72.60 0.583 

50 Subsoil covered with slash 1.08 0.013 

For comparable plots, increases in slope from 15 to 

40 or 45 percent increased erosion. At the steeper 

gradients, erosion increased by factors of 1.2 for the 

ash with litter, 1.7 for the ash without litter, and 3.7 

for the exposed subsoil plots (p. 6). However, the 

effects of the soils, litter, and slash variables were 

much greater than those of slope (p. 6). Both of the 

exposed subsoil plots had high erosion rates, even on 

the gentler slope; all of the volcanic ash topsoil plots 

had low erosion rates, even on the steeper slopes 

(p. 10). 

See the ~eneral Erosion Research Summary for 

additional information on geologically unstable, saturated, highly erodible, or easily compacted soils. 

volumes, tractor size). If we assume that skid trail 

width is partially dependent on tractor size, this research has implications for BMP 5. See discussion of 

the effects of tractor size under this reference in BMP 

7 (Rule 3.c.iii., tractor size rule). 

McGreer 1981, near Headquarters-One-year erosion rates were measured on skid trail plots established with a D-6 Caterpillar tractor. Measured values, adapted from table 2 (p. 9), were: 

Skid trail 

gradient Soil cover 

Percent 

15 Ash with litter 

45 Ash with'litter 

15 Ash without litter 

45 Ash without litter 

15 Exposed subsoil 

40 Exposed subsoil 

50 Subsoil covered with slash 

Erosion rate 

Tons / 

acre 

0.28 

0.30 

1.00 

1.86 

20.46 

72.60 

1.08 

Area 

inches 

0.003 

0.004 

0.012 

0.022 

0.164 

0.583 

0.013 

The author recommended limiting the width of 

blading of skid trails due to higher erosion rates on 

exposed subsoils and on soils without litter or slash 

layers (p. 10). 

Froehlich and others 1985, two sites near McCallThe authors recommended minimizing the area in 

skid trails due to persistent compaction (more than 25 

years) on ground-skidded areas (p. 1017). See summary of this publication under Rule 3.c.i. (BMP's 2 and 

3) for details. 

Clayton 1990, Silver Creek Study Area, Central 

Watersheds, Boise National Forest-Three sites were 

studied for impacts of ground skidding on soils: one 

with a designated main skid trail, logged by Caterpillar tractor; one with a designated main skid trail, 

logged by rubber-tired skidder; and one "loggers' 

choice," with no restrictions other than adhering to 

BMP's. 

Bulk density increased significantly in all areas 

classified as skid trails in each unit (pp. 3-4). The 

author recommended limiting skid trail area by designating skid trails, by directional felling, and by stringing cables rather than driving to logs (p. 7). 

See the summary of this publication under Rule 

3.c.i. (BMP's 2 and 3) for details. 

BMP &Rule 3.c.iii. Limit skid trails to the minimum feasible number. 

BMP 6-Rule 3.c.iii. Limit skid trails to the mini- Haupt 1960, Boise Basin Experimental Forest, Boise 

mum feasible width. National Forest-The objective of this research was to 

Haup t 1960, Boise Basin Experimental Forest, Boise determine the andarealextentofsoil dist~bance 

National Forest-The objective of this research was to caused by logging activities under various treatments 

determine the type and areal extent of soil disturbance (silvicultural systems, initial stand volumes, reserve 

caused by logging activities under various treatments volumes, tractor size). Areas bared by logging were 

(silvicultural systems, initial stand volumes, resene classified as having more or less than 50 percent ofthe 
mineral soil exposed. About 90 percent of the "skidding and associated disturbance" areas had more than 

50 percent mineral soil exposed (p. 635). However, the 

author noted that skid trail disturbance is beneficial 

for regeneration of ponderosa pine (p. 638). 

This study also showed that tradeoffs might exist 

between area in skid trails and area in roads; see the 

summary under the next rule (BMP 7) for details. See 

Haupt and Kidd (1965) for a followup to this report. 

Haupt and Kidd 1965, Boise Basin Experimental 

Forest, Boise National Forest-This article is a followup 

to Haupt (1960). An attempt was made to minimize 

erosion associated with logging and logging road construction in 1953 to 1954 by use of "good logging 

practices," including reuse of skid trails wherever 

possible (p. 665). 

Most skid trail rill erosion occurring on the study 

area during the first 4 years was contained in the next 

erosion control structure downslope; after that time 

skid trails had stabilized due to rehabilitation measures. Sediment from skid trails was deliveredto streams 

only near stream crossings (p. 668). 

Lenhard 1978, near Potlatch-On volcanic-ash influenced soils, a Clark 666 rubber-tired skidder was 

used to test for changes in soil properties as travel 

intensity increased. Seven sites within one-half acre 

were randomly assigned treatments of 1, 2, 4, 8, 16, 

and 32 passes (p. 7). 

Significant changes in bulk density (ranging from 14 

to 34 percent) occurred for 4 to 32 passes; one to two 

passes did not produce significant changes (p. 10). 

Bulk densities increased from one to four passes; after 

four passes, bulk densities were relatively constant 

(pp. 15-16). Bulk densities did not differ significantly 

between years (treatment year and 1 year after treatment) except for the one- and four-pass treatments (p. 

11). The one-pass treatment showed an increase in 

bulk density between years; the four-pass treatment 

showed a decrease. Four passes may be a threshold 

value beyond which rapid recovery does not occur (p. 17). 

Pore-size distribution index was significantly altered by all treatments except the one-pass treatment 

(p. 12). The data indicate a redistribution of flow 

channels for treatments with more than four passes 

(p. 18). This entails a reduction in macropores critical 

for plant growth and infiltration processes (p. 22). 

On similar soils, the author suggests that skidder 

operators attempt to disperse rather than concentrate 

their movements over the harvesting unit (p. 22). 

Leverick 1980, University of Idaho Experimental 

Forest, West Hatter Creek and Flat Creek Units--Soil 

compaction and soil disturbance were evaluated for a 

Case-Davis Fleethoe 30 converted to a rubber-tired 

miniskidder for skidding small-diameter trees. 

In the West Hatter Creek unit, experiments were 

conducted to evaluate bulk density changes at various 

depths as related to the number oftrips (O,l, 5,10,15, 

20, 25, or 30) with the skidder (pp. 43, 88). Soil 

moisture varied from 20.38 to 25.32 percent on the 

skid trails tested (p. 88). Bulk density varied with 

number of trips at the 0 to 2 inch depth and at the 4 to 

6 inch depth, but changes were not significant at a 

depth of 8 to 10 inches (p. 89). The first 10 trips 

produced the greatest changes in bulk density (p. 88), 

about 13 percent at a depth of 0 to 2 inches and 10 

percent at 4 to 6 inches (pp. 132-133). 

In the Flat Creek unit, the most heavily traveled 

skid trail was sampled for bulk density around four 

points representing various frequencies of travel. 

Undisturbed areas near each sampling point were also 

sampled. Samples were taken at depths of 0 to 2,4 to 

6, and 8 to 10 inches (p. 44). Skid trail points were 

significantly different from nearby undisturbed points 

only at the 0 to 2 inch depth, probably because of dry 

soil conditions at the time of the experiment (p. 91). 

However, there were significant differences among 

points with different travel frequencies at the 0 to 2 

and 2 to 4 inch depths (p. 91). 

Froehlich and others 1985, two sites near McCallThe authors recommended minimizing the area in 

skid trails due to persistent compaction (more than 25 

years) on ground-skidded areas (p. 1017). See the 

summary of this publication under Rule 3.c.i. (BMP's 

2 and 3) for details. 

Clayton 1990, Silver Creek Study Area, Central 

Watersheds, Boise National Forest-Three sites were 

studied for impacts of ground skidding on soils: one 

with a designated main skid trail, logged by Caterpillar tractor; one with a designated main skid trail, 

logged by rubber-tired skidder; and one 'loggers' 

choice," with no restrictions other than adhering to 

BMP's. 

Bulk density increased significantly (ranging from 

15 to 29 percent) for all areas classified as skid trails 

in each unit (pp. 3-4). Bulk density did not differ 

significantly between the main and secondary skid 

trails on either the tractor or skidder units (p. 4). 

Secondary skid trails had an estimated 3 to 10 passes 

(p. 2); this designation was not used on the loggers' 

choice unit. The author recommended limiting skid 

trail area by designating skid trails, by directional 

felling, and by stringing cables rather than driving to 

logs (p. 7). 

See the summary of this publication under Rule 

3.c.i. (BMP's 2 and 3) for details. 

BMP 7-Rule 3.c.iii. Limit tractor size to the minimum appropriate for the job. 
Haupt 1960, Boise Basin Experimental Forest, Boise 

National Forest-The objective ofthis research was to 

determine the type and areal extent of soil disturbance 

caused by logging activities under various treatments 

(silvicultural systems, initial stand volumes, reserve 

volumes, and tractor size). Bared areas in skid trails 

averaged 34 acres per square mile and haul roads 

averaged 19 acres per square mile for large tractors 

(D-8); areasinskid trails averaged 17 acres per square 

mile, and areas in haul roads averaged 33 acres per 

square mile for small tractors (D-4) (p. 636). 

Some aerences in the patterns of disturbance were 

noted among silvicultural systems. For stem selection, 

using smaller tractors, road areaincreased as harvesting intensified (more trees per square mile), while skid 

trail area remained constant. For the larger tractors, 

skid trail area increased, while road area remained 

constant (pp. 637-638). Regression analysis indicated 

that the total amount of bared area at any given level 

of harvest intensity might be slightly greater for large 

tractors than for small tractors under a stem selection 

system (p. 637). 

For group selection, the effects of tractor size on the 

relative areas in skid trails and roads were not apparent. Areas of disturbance were similar for bothtractor 

sizes, and both skid trail and road disturbance increased as harvesting levels intensified (p. 638). The 

authors state: "Results of the present study indicate 

rather conclusively that excessive haul road disturbance is associated with use of small tractors in stem 

selection cutting" (p. 638). 

Skid trail disturbance is beneficial to regeneration 

of ponderosa pine, while most haul roads offer poor 

sites for regeneration. Haul roads are useful for providing future access (p. 638). 

See Haupt and Kidd (1965) for a followup article 

with implications for this rule. 

Haupt and Kid 1965, Boise Basin Experimental 

Forest, Boise National Forest-This is a followup to 

Haupt (1960). Although the results presented here do 

not address the tractor size rule, when combined with 

the results given in the summary for Haupt (1960) 

there are implications for the rule. 

An attempt was made to minimize erosion associated with logging and logging road construction from 

1953 to 1954 by use of "good logging practices," including reuse of skid trails, a prohibition on skidding down 

channels, limited skidding across channels, seeding of 

skid trails, installationof slash barriers or cross ditches 

on skid trails, installation of cross ditches on roads, 

and seeding and harrowing of roads (p. 665). 

Most skid trail rill erosion occurring on the study 

area during the first 4 years (1953 to 1957) was 

contained in the next erosion control structure 

downslope; by 1957 skid trails had stabilized due to 

rehabilitation measures. Sediment from skid trails 

was delivered to streams only near stream crossings 

(p. 668). Most sediment heading to and in channels 

was from haul roads; roadways were revegetated and 

stabilized by 1958 (p. 668). 

Leverick 1980, University of Idaho Experimental 

Forest, West Hatter Creek and Flat Creek units-The 

Case-Davis Fleethoe 30 converted to a miniskidder 

was not durable enough for skidding small-diameter 

trees. The author suggested that the Case-Davis DH4, 

a slightly larger utility machine, might be better 

suited (p. 97). See Rule 3.c.i. (BMP's 2 and 3) for site 

impacts; see Rummer (1982) for a followup. 

Rurnmer 1982, University of Idaho Experimental 

Forest, Hatter Creek and Flat Creek units-The Case 

DH4 backhoe was tested for skidding small-diameter 

trees, as recommended by Leverick (1980). The DH4 

functioned adequately with minimal site impact; see 

Rule 3.c.i. (BMP's 2 and 3) for details. 

BMP %Rule 3.c.i~. Uphill cable yarding is preferred. 

Jensen and Finn 1966, Zena Creek Logging Study 

Area, Payette National Forest-A hydrologic analysis 

of the study area (13,334 acres) was conducted to 

evaluate watershed conditions and make recommendations (pp. 1, 2). Five landtypes were present; the 

decomposed granitic landtype was most susceptible to 

erosion and sedimentation problems. For example, in 

any watershed, the sedimentation rate was directly 

proportional to the road mileage constructed in the 

lands with decomposed granitic soils (pp. 4,85). Sediment rates as much as 1,000 times higher than normal 

were measured in some watersheds with decomposed 

granitic soils (p. 84). Subsurface flows of water are 

intercepted by roadcuts, interrupting the normal hydrologic function and beginning a cycle of accelerated 

erosion on these landtypes (pp. 4,32,62). 

Because of these characteristics, the authors recommended that road building on decomposed granitic 

soils be limited mostly to ridgetops, unless exposed 

areas could be completely stabilized, and the hydrologic fundion could be preserved (pp. 8, 32). Logging 

on these areas would require logging systems capable 

of uphill yarding to ridgetop roads, or logging systems 

that do not require roads (p. 59). They felt that the 

Skagit Mobile Yarder, a skyline yarder that had been 

used in the study area, could be used in some situations with minimal watershed damage if roads were 

built on ridgetops or on stable landtypes (other than 

decomposed granitics). However, they noted that the 

Skagit system was not the ultimate for logging of 

decomposed granitic soils (p. 59). 

See Craddock (1967) for further information. 

Craddock 1967, Zena Creek Logging study Area, 

Payette National Forest-Both downhill and uphill 

cable yardingwere conducted on the study area, using 
the Skagit Mobile Yarder, a skyline yarder. Although 

no quantitative erosion data were given, the downhill 

cable yarding configuration was unsatisfacto2y. Reasons included ground disturbance, damage to the 

residual stand, and lack of control. When the uphill 

yarding configuration was used, soil disturbance was 

minimal and stand damage was also avoided (p. 25). 

Megahan and Kidd 1972b, Deep Creek drainage, 

Zena Creek Logging Study Area, Payette National 

Forest-Onsite erosion for skyline and jammer logging were evaluated using erosion plots. No significant differences were found between the two methods; 

sediment production in ephermeral drainages increased an average of 0.6 times for the 5 years after 

logging (pp. 139-140). The skyline system probably 

caused more disturbance thanusual because the slopes 

were straight to convex, rather than concave, and 

because the logs were skidded downhill rather than 

uphill (p. 139). 

BMP 9-Rule 3.c.i~. When downhill cable yarding is 

used, take reasonable care to lifi leading ends of logs 

to minimize downhill movement of slash and soils. 

No references were found specific to lifting leading 

ends of logs; see the previous rule (BMP 8) for general 

observations regarding downhill cable yarding. 

Rule 3.d. Location of Landings, Skid 

Trails, and Fire Trails 

Seventeen BMP's (10 through 26) were evaluated. 

These BMP7s deal with four major concepts: 

(1) The location of landings, skid trails, and fire 

trails relative to: 

Site stability 

The stream protection zone 

Amount of sidecasting 

(BMP7s 10 through 17); 

(2) Landing size (BMP 18); 

(3) Inclusion of slash or stumps in landing fill material (BMP's 19 and 20); 

(4) Stabilization of landings requiring sidecasting 

by (BMP's 21 through 26): 

Seeding 

Compaction 

Riprapping 

Benching 

Mulching 

Other suitable means. 

19 through 26, see the corresponding BMP7s under 

Rule 4.c., Road construction. 

Research Results by Best Management 

Practice 

BMP 10-Rule 3.d. Locate landings on stable areas 

to prevent the risk of materials entering streams. 

See Rule 3.d.i., landing location rule (BMP 13), and 

the General Erosion Research Summary. 

BMP 11-Rule 3.d. Locate skid trails on stable 

areas to prevent the riskofmaterials entering streams. 

See Rule 3.d.i., skid trail location rule (BMP 14), and 

the General Erosion Research Summary. 

BMP 12-Rule 3.d. Locate fire trails on stable areas 

to prevent the risk of materials entering streams. 

See Rule 3.d.i., fire trail location rule (BMP 15), and 

the General Erosion Research Summary. 

BMP 13--~ule 3.d.i. Locate allnew or reconstructed 

landings on stable areas outside the appropriate stream 

protection zone. 

See the General Erosion Research Summary; no 

specific references were found. 

BMP 1ARule 3.d.i. Locate all new or reconstructed 

skid trails on stable areas outside the appropriate 

stream protection zone. 

See the General Erosion Research Summary; no 

specific references were found. 

BMP 15-Rule 3.d.i. Locate all new or reconstructed 

fire trails on stable areas outside the appropriate 

stream protection zone. 

See the General Erosion Research Summary; no 

specific references were found. 

BMP 16Rule 3.d.i. Locate fire trails where 

sidecasting is held to a minimum. 

No references were found. 

BMP 17-Rule 3.d.i. Locate skid trails where 

sidecasting is held to a minimum. 

No references were found. 

BMP 18-Rule 3.d.ii. Minimize the size of landings 

to that necessary for safe economical operation. 

No references were found. 

BMP 19-Rule 3.d.iii. Keep fill material used in 

landing construction free of loose stumps to prevent 

landslides. 

No references were found specific to landings; see 

rule 4.c.iv., woody materials in roadfills (BMP 127). 

BMP 2CRule 3.d.iii. Keep fill material used in No references were foundthats~ecificall~ dealt ldng construction free of excessive slash to prevent these topics in the context of landings, skid trails, and landslides. fire trails. However, information on stable areas is in No references were found specific to landings; see the General Erosion Resemh S=~W- For BMP7s rule 4.c.iv., woody in roadfills (BMP 127). 
BMP 21-Rule 3.d.iii. On slopes where sidecasting Practices 42 through 44 address achieving landing 

is necessary, stabilize landings by use of: seeding (first drainage and stabilization through: - 

alternative). Reshaping (BMP 42); 

No references were found specific to landings; see Establishing ground cover (BMP 43); rule 4.c.iii., stabilization of exposed material by seed- Other means (BMP 44). ing (BMP 117). 

No research was found on fire trail stabilization. BMP 2!2-Rule 3.d.iii On slopes where sidecasting Only one reference was found on landing drainage. is stabilize lan&@ by use of: compadion Clayton (1990, p. 7) noted that standard rock ripwrs (second alternative). did not adequately reduce subsoil compaction on a No references were found specific to landings; see landing in the Silver Creek study area H~ recorn- rule 4.c.iii., stabilization of exposed material by com- mended that other implements be tested. paction (BMP 118). Froehlich and others (1985, p. 1017) recommended 

BMP 23--Rule 3.d.iii. On slopes where sidecasting 

is necessary, stabilize landings by use of: riprapping 

(third alternative). 

No references were found specific to landings; see 

rule 4.c.iii., stabilizationofexposedmaterial by riprapping (BMP 119). 

BMP 2ARule 3.d.iii. On slopes where sidecasting 

is necessary, stabilize landings by use of: benching 

(fourth alternative). 

No references were found specific to landings; see 

rule 4.c.iii., stabilizationof exposed material by benching (BMP 120). 

BMP 25-Rule 3.d.iii. On slopes where sidecasting 

is necessary, stabilize landings by use of: mulching 

(fiRh alternative). 

No references were found specific to landings; see 

rule bc.iii., stabilizationof exposedmaterialby mulching (BMP 121). 

BMP 26-Rule 3.d.iii. On slopes where sidecasting 

is necessary, stabilize landings by use of: other suitable means (sixth alternative). 

No references were found specific to landings; see 

rule 4.c.iii., stabilization of exposed material by other 

suitable means (BMP 122). 

Rule 3.e. Drainage Systems 

Seventeen BMP's (27 through 44) were evaluated. 

Best management practices 27 through 29 are the 

general rule 3.e.: For each landing, skid trail, and fire 

trail, provide and maintain a drainage system that 

scarifying skid trails because bf the long-term compaction observed in their research. 

Kidd (1963, pp. 4-6) found that log water bars were 

more effective than slash dams, or lopping and scattering slash, for controlling erosion on seeded skid trails 

with soils derived from granite or basalt. Cross ditches 

could be substituted for log water bars if every third or 

fourth structure remained a log water bar. All structures were generally ineffective in ravines. 

Haupt and Kidd (1965, p. 668) noted that both slash 

barriers and cross ditches were generally effective in 

containing sediment on seeded skid trails in the Boise 

Basin Experimental Forest. 

McGreer (1981, p. 9) found that, for skid trails with 

the volcanic ash topsoils intact, leaving a remnant 

litter layer reduced &st-year erosion 72 percent on 15 

percent gradient skid trails, and 84 percent on 45 

percent gradient trails. For skid trails with the volcanic ash topsoil bladed away and the alluvial subsoils 

exposed, first-year erosion was reduced by placing 

slash on the skid trail. Erosion on the slash-treated, 50 

percent gradient skid trail was 98.5 percent less than 

on a 40 percent gradient skid trail without slash, and 

94.7 percent less than on a 15 percent gradient skid 

trail without slash. Skid trails with exposed alluvial 

subsoils without slash treatments had much higher 

erosion rates and slower recovery than skid trails on 

volcanic ash topsoils. 

Gray and Megahan (1981 p. 21) recommended Zeavhg undisturbedvegetation below skid trails and other 

disturbed areas to spread water and reduce the likelihood of mass erosion. - - 

will control the dispersal of surface water in order to . 

prevent sediment from damaging Class I streams. Research Results by Best Management 

Practices 30 through 41 suggest six alternatives for Practice 

stabilizing skid trails and firetrails: 

Water bars (BMP's 30 and 36); 

Cross drains (BMP's 31 and 37); 

Outsloping (BMP's 32 and 38); - - Scarif~cation (BMP's 33 and 39); 

Seeding (BMP's 34 and 40); 

Other suitable means (BMP's 35 and 41). 

BMP 27-Rule 3.e. For each landing, provide and 

maintain a drainage system that will control the 

dispersal of surface water in order to prevent sediment 

from damaging Class I streams. 

Gray and Megahan 1981, Pine Creek, Boise National 

Forest-Based on their analyses of slope stability in 

the Idaho Batholith, the authors recommend leaving 
undisturbed vegetation to provide water-spreading 

areas large enough to accommodate water draining 

from roads, skidtrails, and other disturbed areas (p. 21). 

BMP 28-Rule 3.e. For each skid trail, provide and 

maintain a drainage system that will control the 

dispersal of surface water in order to prevent sediment 

from damaging Class I streams. 

Gray and Megahan 1981-See discussion under 

BMP 27. 

See Rule 3.e.i., skid trail drainage (BMP's 30 through 

35). 

BMP 29-Rule 3.e. For each fire trail, provide and 

maintain a drainage system that will control the 

dispersal of surface water in order to prevent sediment 

from damaging Class I streams. 

Gray and Megahan 1981-See discussion under 

BMP 27. 

See Rule 3.e.i., fire trail drainage (BMP9s'36 through 

41). 

BMP 30-Rule 3.e.i. Keeping current, stabilize 

erosion-prone skid trails by: water barring (first 

alternative). 

Kidd 1963, four sites on the Payette and Boise Nutwnal Forests, three granitic, one basaltic-Various 

skid trail erosion control methods (lopping and scattering slash, slash dams, and log water bars) were 

tested on two soil parent materials, granite and basalt 

(p. 1). All skid trails were seeded after installation of 

erosion control structures (p. 2). Qualitative effectiveness ratings were assigned with 1.0 completely effective and 4.8 completely ineffective (p. 3). 

Effectiveness ratings of the various structures were 

not significantly different in analysis of variance because of the general ineffectiveness of all types of 

structures in ravine bottoms (pp. 4-51. Water-diverting structures (log water bars and cross ditches) were 

generally more effective than the sediment-filtering 

methods (slash dams and lopping and scattering of 

slash) (p. 5). 

Effectiveness ofthe various structures was analyzed 

relative to soil parent material, sidehill versus ravine, 

and percent of slope. Overall, log water bars were most 

effective, with ratings of 1.78 on granitic soils and 1.54 

on basaltic soils, compared to ratings of 2.15 (granitic 

soils) and 2.25 (basaltic soils) for slash dams, and 2.93 

(granitic soils) and 1.60 (basaltic soils) for lopping and 

scattering of slash (p. 5). 

Slash dams were not recommended for use on 

sidehills due to their high relative cost and their 

inability to divert water; they also deteriorate and 

become ineffective in 1 or 2 years. Log water bars do an 

excellent job of diverting water on either flat or shallow, trough-shaped sidehill skid trails. Cross ditches 

can be substituted for log water bars, but are prone to 

sloughing; every third or fourth structure should be a 

log water bar to divert water. Cross ditches are the 

least expensive. Lopping and scattering of slash was 

recommended for gentler slopes with minimal potential for surface flow undercutting. Recommendations 

are given for spacing of structures based on slope 

gradient, soil parent material, and sidehill versus 

ravine (p. 6). 

BMP 31-Rule 3.e.i. Keeping current, stabilize 

erosion-prone skid trails by: cross draining (second 

alternative). 

Kidd 1963-See Rule 3.e.i., stabilization of skid 

trails by water barring (BMP 30). 

Haupt and Kidd 1965, Boise Basin Experimental 

Forest, near Idaho City-On seeded skid trails with 

slash barriers or cross ditches, sediment from rills was 

generally contained by erosion control structures during the first 4 years; after that, skid trails had stabilized. Skid trail sediment reached streams only near 

stream crossings (p. 668). No quantitative effectiveness data were given. 

BMP 32-Rule 3.e.i. Keeping'current, stabilize 

erosion-prone skid trails by: outsloping (third 

alternative). 

No references were found. 

BMP 33--Rule 3.e.i. Keeping current, stabilize erosion-prone skid trails by: scarifying (fourth alternative). 

Froehlich and others 1985, two sites near McCall, 

one granitic, one volcanic-The authors recommend 

scarifying skid trails because of persistent compaction 

(more than 25 years) on ground-skidded areas (p. 1017). 

See Rule 3.c.i. (BMP's 2 and 3) for details. 

BMP 3P-Rule 3.e.i. Keeping current, stabilize erosion-prone skid trails by: seeding (fifth alternative). 

Kidd 1963-see rule 3.e.i., stabilizationofskid trails 

by water .barring (BMP 30); seeding was used in 

conjunction with other methods tested rather than 

being tested separately. 

Haupt and Kidd 1965-See rule 3.e.i., stabilization 

of skid trails by cross draining (BMP 31); seeding was 

used in conjunction with other methods rather than 

being tested separately. 

See the General Erosion Research Summary regarding the effectiveness ofvegetation and other ground 

cover in reducing erosion. 

BMP 36-Rule 3.e.i. Keeping current, stabilize erosion-prone skid trails by: other suitable means (sixth 

alternative). 

Kidd 1963-see rule 3.e.i., stabilizationof skidtrails 

by water barring (BMP 30) for a discussion of the 

effectiveness of slash dams and lopping and scattering 

slash. 
Haupt and Kidd 1965-See rule 3.e.i., stabilization 

of skid trails by cross draining (BMP 31), for a discussion of the effectiveness of slash barriers. 

McGreer 1981, near Headquarters-For skid trails 

with the volcanic ash topsoils intact, leaving a remnant litter layer reduced first-year erosion 72 percent 

on 15 percent gradient skid trails, and 84 percent on 45 

percent gradient skid trails (p. 9). 

For skid trails with the volcanic ash topsoil bladed 

away and the alluvial subsoils exposed, first-year 

erosion was reduced by placing slash on the skid trail. 

Erosion on the slash-treated 50 percent gradient skid 

trail was 98.5 percent less than on a 40 percent 

gradient skid trail without slash, and 94.7 percent less 

than on a 15 percent gradient skid trail without slash 

(p. 9). 

Skid trails with exposed (no slash) alluvial subsoils 

had much higher erosion rates and slower recovery 

than skid trails on volcanic ash topsoils (p. 9). 

Although water bar use was not a variable in this 

study, it was assumed that water bars would be used 

whenever topsoils or subsoils were exposed (p. 10). 

See the General Erosion Research Summary for 

additional information. 

BMP 36--Rule 3.e.i. Keeping current, stabilize erosion-prone iire trails by: water barring (first alternative). 

No references were found specSc to fire trails; see 

Rule 3.e.i., stabilization of skid trails by water barring 

(BMP 30). 

BMP 37-Rule 3.e.i. Keeping current, stabilize 

erosion-prone fire trails by: cross draining (second 

alternative). 

No references were found specific to fire trails; see 

Rule 3.e.i., stabilization of skidtrails by cross draining 

(BMP 31). 

BMP 38-Rule 3.e.i. Keeping current, stabilize 

erosion-prone fire trails by: outsloping (third 

alternative). 

No references were found specific to fire trails; see 

Rule 3.e.i., stabilization of skid trails by outsloping 

(BMP 32). 

BMP 39-Rule 3.e.i. Keeping current, stabilize 

erosion-prone fire trails by: scarifying (fourth 

alternative). 

No references were found specific to fire trails; see 

Rule 3.e.i., stabilization of skid trails by scarifying 

(BMP 33). 

BMP 40--Rule 3.e.i. Keeping current, stabilize erosion-prone fire trails by: seeding (fifth alternative). 

No references were found specific to fire trails; see 

Rule 3.e.i., stabilization of skid trails by seeding 

(BMP 34). 

BMP 41-Rule 3.e.i. Keeping current, stabilize erosion-prone fire trails by: other suitable means (sixth 

alternative). 

No references were found specific to fire trails; see 

Rule 3.e.i., stabilization of skid trails by other suitable 

means (BMP 35). 

BMJ? 42-Rule 3.e.ii. Reshape landings as needed to 

facilitate drainage prior to fall and spring runoff. 

No references were found. 

BMF'43-Rule 3.e.ii. Within 1 year after harvesting 

is completed, stabilize all landings by establishing 

ground cover (first alternative). 

No references were found specific to landings; see 

the General Erosion Research Summary regarding 

stability due to ground cover. See Clayton 1990, under 

BMP 44, stabilization of landings by some other means. 

BMP 44--Rule 3.e.ii. Within 1 year after harvesting 

is completed, stabilize all landings by: some ather 

means (second alternative). 

Clayton 1990, Silver Creek, Boise National ForestThe landing tested in this study was compacted (to a 

statistically significant degree assumed to be detrimental to productivity); standard rock rippers did not 

successfully reduce subsoil compaction. The author 

recommended that other implements such as the 

winged subsoiler be tested (p. 7). 

Rule 3.f. Treatment of Waste 

Materials 

Seventeen BMP's (45 through 61) were evaluated. 

Practices 45 through 47 comprise the general rule 3.f.: 

"All debris, overburden, and other waste material 

associated with harvesting shall be left or placed in 

such a manner as to prevent their entry by erosion, 

high water, or other means into streams." The remaining BMP's deal with five general topics: 

Felling, bucking, and limbingtrees such that trees 

and tree parts fall away from Class I streams 

(BMP's 48 through 50); 

Removing slash and debris that falls into streams 

(BMP's 51,52,54,55); 

Placement or treatment of material removed &om 

streams (BMP's 53,56,57); 

Placement of waste material from construction or 

maintenance of landings, skid trails, and fire trails 

(BMP's 58 through 60); 

Placement of logging operation waste such as 

crankcase oil, filters, grease, and oil containers 

(BMP 61). 

No research was found that addressed these topics 

in any depth. Only one study was considered relevant. 

Megahan and others (1995) found some evidence that 
removing logging slash from streams by hand may 

have released sediments stored behind natural channel obstructions. 

The reader is also referred to Rule 4.c.ii., clearing 

road construction debris from drainage ways (BMP 

115). King (1981, p. 63) concluded that normal slash 

clearing operations associated with road construction 

activities have minimal effects on stream sedimentation. 

Research Results by Best Management 

Practice 

BMP 46-Rule 3.f. Leave or place all debris associated with harvesting in such a manner as to prevent 

entry by erosion, high water, or other means into 

streams. 

No references were found. 

BMP 46-Rule 3.f. Leave or place all overburden 

associated with harvesting in such a manner as to 

prevent entry by erosion, high water, or other means 

into streams. 

No references were found. 

BMP 47-Rule 3.f. Leave or place all other waste 

material associated with harvesting in such a manner 

as to prevent entry by erosion, high water, or other 

means into streams. 

No references were found. 

BMP 48-Rule 3.f.i. Wherever possible, fell trees in 

such a manner that the tree or any part thereof will 

fall away from any Class I streams. 

No references were found. 

BMP 49--Rule 3.f.i. Wherever possible, buck trees 

in such a manner that the tree or any part thereof 

will fall away from any Class I streams. 

No references were found. 

BMP SO-Rule 3.f.i. Wherever possible, limb trees 

in such a manner that the tree or any part thereof 

will fall away from any Class I streams. 

No references were found. 

BMP 61-Rule 3.f.i. Continuously remove slash 

that enters Class I streams as a result of harvesting 

operations. 

Megahan and others 1995, Silver Creek Study Area, 

Boise National Forest-In a paired watershed study of 

the effects of helicopter logging and broadcast burning, logging slash that fell into streams was removed 

by hand after the logging was completed. 

The year following logging was the only year (of 7 

years analyzed) that the unlogged watershed had 

more sediment stored behind channel obstructions. 

(There was no statistically significant difference between the two watersheds in channel sediment storage behind obstructions in any of the years before or 

after logging.) The authors hypothesized that slash 

removal may have disturbed some natural channel 

obstructions in the logged watershed. 

See Rule 4.c.i.i., clearing road construction debris 

from drainage ways (BMP 115). 

BMP 62--Rule 3.f.i. Continuously remove other 

debris that enters Class I streams as a result of 

harvesting operations whenever there is a potential 

for stream blockage or if the stream has the ability for 

transporting such debris. 

No references were found. 

BMP 63-Rule 3.f.i. Place removed material 5 feet 

slope distance above the ordinary high water mark. 

No references were found. 

BMP 6ARule 3.f.ii. Immediately after skidding 

remove slash that enters Class I1 streams whenever 

there is a potential for stream blockage or if the stream 

has the ability for transporting such debris. 

Megahan and others 1995-See summary under 

BMP 51. 

BlVIP 66-Rule 3.f.ii. Immediately after skidding 

remove other debris that enters Class I1 streams 

whenever there is a potential for stream blockage or 

if the stream has the ability for transporting such 

debris. 

No references were found. 

BMP 66-Rule 3.f.ii. Place removed material above 

the high water mark (first alternative). 

No references were found. 

BMP 57-Rule 3.f.ii. Otherwise treat (removed 

material) as prescribed by the department (second 

alternative). 

No references were found. 

BMP 68--Rule 3.f.iii. Deposit waste material from 

construction or maintenance of landings in geologically stable locations outside ofthe appropriate stream 

protection zone. 

No references were found. See the General Erosion 

Research Summary regarding geologically stable 

locations. 

BMP 69-Rule 3.f.iii. Deposit waste material from 

construction or maintenance of skid trails in geologically stablelocations outside ofthe appropriate stream 

protection zone. 

No references were found. See the General Erosion 

Research summary regarding geologically stable 

locations. 

BMP 60-Rule 3.f.iii. Deposit waste material from 

construction or maintenance of fire trails in geologically stable locations outside ofthe appropriate stream 

protection zone. 

No references were found. See the General Erosion 

Research Summary regarding geologically stable 

locations. 
BMP 61-Rule 3.f.i~. Place waste resulting from 

logging operations (such as crankcase oil, filters, grease, 

and oil containers) outside of Class I and Class I1 

stream protection zones. 

No references were found. 

Rule 3.g. Stream Protection 

Twenty BMP's (62 through 81) were evaluated. 

Practice 62 is the general rule 3.g.: "During and after 

forest practice operations, protect streambeds and 

streamside vegetation to maintain water quality." 

The remaining BMP's address four main topics: 

Stream crossings during skidding (BMP's 63 

through 68); 

Cable yarding within the stream protection zone 

(BMP's 69 and 70); 

Vegetation management in Class I stream protection zones (BMP's 71 through 80); 

Soil protection in Class I1 stream protection zones 

(BMP 81). 

Two references were found regarding stream crossings. In a paired watershed study near Pierce, 

Bachmann (1958, pp. 23,34-35) found that skidding 

logs across the creek increased turbidities and stream 

blockages due to damming by slash and debris. 

Turbidities were 100 parts per million when logs were 

being skidded across the stream. Measured pretreatment turbidities on the same stream were less than 7 

parts per million; on the control watershed they were 

less than 6 parts per million throughout the 3-year 

study period. Near Idaho City, Haupt and Kidd (1965, 

p; 668) observed sedimentation effects downstream 

from skid trail stream crossings. 

No research was found on cable yarding within 

stream protection zones. 

Only one study was found that actually compared 

water quality in logged areas with and without streamside buffer strips. In the Priest River Experimental 

Forest, Snyder (1973) compared physical and chemical properties upstream and downstream of areas that 

had been clearcut and that had the slash burned. For 

paired sampling stations with buffer strips, the only 

parameters with significant increases between the 

upstream and downstream stations were electrical 

conductivity, bicarbonate, sulfate, calcium, and magnesium. For paired sampling stations without buffer 

strips, all of those parameters showed significant 

differences; in addition, pH, turbidity, suspended solids, and potassium showed significant differences. 

Parameters showing no significant differences included 

chloride, nitrate, and sodium. Buffer strips may reduce suspended solids by blocking the movement of 

sediment and confining the flow of water to existing 

stable channels (pp. 64-65). 

Clayton and Kennedy (1985, p. 1047) found minimal 

losses of nutrients in solution and in sediments for the 

first 4 years after clearcut logging and slash burning 

in the Silver Creek Study Area. Buffer strips were 

credited as one factor limiting movement of large 

amounts of nutrients mobilized by slash burning and 

decay, and for limiting sediment delivery to streams. 

In a companion study on the same watershed, Megahan 

and others (1995) found that total annual sediment 

yields were increased an average of 97 percent for 10 

years after treatment. About 94 percent of the increased sediment yield was attributed to accelerated 

surface erosion (resulting primarily from broadcast 

burning) on the cutting units; a maximum of 6 percent 

was attributed to a mass erosion site on the cutting 

units. The sediment from the mass erosion site was 

delivered directly to the stream. Sediment delivery 

ratios could not be ascertained from the available 

data. 

Based on their analyses of slope stability in the 

Idaho Batholith, Gray and Megahan (1981, pp. 20-21) 

recommended leaving buffer zones of undisturbed 

vegetation along all streams during clearcut logging 

operations. Several studies reported in the General 

Erosion Research Summary show the importance of 

vegetation in soil stabilization. See the road buffer 

strip rules (BMPYs 86 through 88). 

Research Results by Best Management 

Practice 

BMP 62--Rule 3.g. During and after forest practice 

operations, protect streambeds and streamside vegetation to maintain water quality and aquatic habitat. 

See more specific rules in 3.g.i., 3.g.ii., 3.g.iii., and 

3.g.i~. (BMP's 63 through 81). 

BMP 63-Rule 3.g.i. Avoid tracked or wheeled skidding in or through streams. 

Bachmann 1958, Crystal and Silver Creeks near 

Pierce, Gold and Simmons Creeks near Avery-Skidding of logs across Crystal Creek increased turbidities 

and stream blockages due to slash and debris dams (p. 

23). Turbidities were 100 parts per million when logs 

were being skidded across the stream. Measured pretreatment turbidities on the same stream were less 

than 7 parts per million; on the control watershed they 

were less than 6 parts per million throughout the 

3-year study period (pp. 3435). 

Haupt and Kidd 1965, Boise Basin Experimental 

Forest near Idaho City-In this study, logs were skidded across streams only when it was impractical to do 

otherwise (p. 665). There were 58 skid trail channel 

crossings in the 16 logged watersheds (p. 666). Following use, skid trails were seeded, and cross ditched or 

covered with slash (p. 665). Although no quantitative 
data were reported, it was noted that the only sediment found in streams due to skidding was in areas 

immediately downstream of the skid trail crossings 

(p. 668). 

BMP *Rule 3.g.i. Install adequate temporary 

structures to carry streamflow when streams must be 

crossed. 

No references were found. 

BMP 66-Rule 3.g.i. Cross a stream at right angles 

to its channel if at all possible. 

No references were found. 

BMP 66--Rule 3.g.i. Comply with the Stream Channel Protection Act when constructing hydraulic structures in streams. 

No references were found. 

BMP 67-Rule 3.g.i. Remove all temporary crossings immediately after use. 

No references were found. 

BMP 68-Rule 3.g.i. Water bar the ends of skid 

trails near channel crossings where applicable. 

No references were found specific to water bars on 

the ends of skid trails near channel crossings; see Rule 

3.e.i., water bar rule (BMP 30) for generalinformation 

on the effectiveness of water bars on skid trails. 

BMP 69-Rule 3.g.ii. Minimize streambankvegetation disturbance when cable yarding is necessary 

across or inside stream protection zones. 

No specific references were found. See the General 

Erosion Research Summary for information on 

vegetation's effectiveness in stabilizing soil. 

BMP 70-Rule 3.g.ii. Minimize channeldisturbance 

when cable yarding is necessary across or inside stream 

protection zones. 

No references were found. . 

BMP 71-Rule 3.g.iii. Provide the large organic 

debris (LOD), shading, soil stabilization, wildlife cover 

and water filtering effects of vegetation along Class I 

streams. 

All the references found on the effectiveness of 

buffer strips between cutting units and streams are 

cited below. They do not distinguish between Class I 

and Class I1 streams. 

See Rule 4.b.i., buffer strips below roads (BMP's 86 

through 88) and the General Erosion Research Summary for information on vegetation's effectiveness in 

stabilizing soil. 

Snyder 1973, Benton Creek, Ida Creek, and Canyon 

Creek, Priest River Experimental Forest-Water was 

sampled for various physical and chemical properties 

at stations upstream and downstream from areas that 

had been clearcut logged and had the slash burned. 

Buffer strips of undisturbed vegetation were 200 feet 

wide on Benton and Ida Creeks, and 100 feet wide on 

Canyon Creek (pp. 7,9,11). 

For paired sampling stations with buffer strips, the 

only parameters with significant increases between 

the upstream and downstream stations were electrical conductivity, bicarbonate, sulfate, calcium, and 

magnesium. For paired sampling stations without 

buffer strips, all those parameters again showed significant differences; in addition, pH, turbidity, suspended solids, and potassium showed significant differences. Parameters showing no significant difference 

included chloride, nitrate, and sodium. 

Buffer strips may reduce suspended solids by blocking the movement of sediment and confining the flow 

of water to existing stable channels (pp. 64-65). 

Gray and Megahan 1981, Pine Creek Study Area, 

Middle Fork of the Payette River Drainage, Boise 

National Forest-Several analyses evaluated the contributions offorest vegetation to slope stability through 

various mechanisms. The authors recommended leaving buffer zones of trees above and below haul roads, 

and leaving buffer zones of undisturbed vegetation 

along all streams during clearcut logging operations 

(pp. 20-21). 

Clayton and Kennedy 1985, Silver Creek Study Area, 

Boise National Forest-A paired watershed approach 

was used to evaluate changes in nutrient budgets of 

six elements (potassium, calcium, magnesium, sulfur, 

phosphorus, and nitrogen) following clearcut logging, 

helicopter yarding, and broadcast burning of slash. 

Buffer strip widths averaged 15 meters for first- and 

second-order channels, and 30 meters for the thirdorder main channel (pp. 1042-1043). Nitrate-nitrogen 

in streamwater increased about 10 times for the 4 

years after logging; no other treatment effects were 

apparent in the stream solution chemistry (pp. 1045- 

1046). There were small but significant changes in 

stream sediment nutrient transport for all elements 

the third year following logging (p. 1046). 

Nutrient losses in solution and in sediments were 

characterized as "minimally accelerated" (p. 1047). 

Buffer strips were credited as one factor limiting 

movement of large amounts of nutrients mobilized by 

slash burning and decay, and limiting the delivery of 

sediment to streams (p. 1047). 

Megahan 1987, and Megahan and others 1995, 

Silver Creek Study Area, Boise National Forest-In a 

paired watershed study, the treated watershed was 

helicopter logged; slash was broadcast burned. Buffer 

strips averaging 25 meters wide were left between 

cutting units and perennial streams. Vegetation within 

the buffer strips was undisturbed, except that trees 

expected to die before the next timber harvest were 

removed. 
Total annual sediment yields at the watershedmouth 

were increased an average of 97 percent (or a total of 

114 tonnes) for 10 years after treatment. Streamflow 

analyses and studies conducted in the channels indicated that accelerated channel erosion was not responsible for the increased sediment yields. Rather, 

about 94 percent of the increased sediment yield was 

attributed to accelerated surface erosion (resulting 

primarily from broadcast burning) on the cutting units; 

a maximum of 6 percent was attributed to a mass 

erosion site on the cutting units. The sediment from 

the mass erosion site (about 7 tonnes) was delivered 

directly to the stream. Sediment delivery ratios could 

not be ascertained from the available data. 

BMP 72-Rule 3.g.iii.(a). Leave hardwood trees 

wherever they afford shade over a stream or maintain 

the integrity of the soil near a stream (Class I). 

No specific references were found. See Rule 3.g.iii., 

general buffer strip rule (BMP 71), and the General 

Erosion Research Summary. 

BMP 73--Rule 3.g.iii.(a). Leave shrubs wherever 

they afford shade over a stream or maintain the 

integrity of the soil near a stream (Class I). 

No specific references were found. See Rule 3.g.iii., 

general buffer strip rule (BMP 71), and the General 

Erosion Research Summary. 

BMP 74-Rule S.g.iii.(a). Leave grasses wherever 

they afford shade over a stream or maintain the 

integrity of the soil near a stream (Class I). 

No specific references were found. See Rule 3.g.iii., 

general buffer strip rule (BMP 71), and the General 

Erosion Research Summary. 

BMP 75--Rule 3.g.iii.(a). Leave rocks wherever 

they afford shade over a stream or maintain the 

integrity of the soil near a stream (Class I). 

No specific references were found. See Rule 3.g.iii., 

general buffer strip rule (BMP 711, and the General 

Erosion Research Summary. 

BMP 76--Rule 3.g.iii.(b). Leave 75 percent of the 

current shade over the stream (Class I). 

No references were found. 

BMP 77-Rule 3.g.iii.(c). Carefully log the mature 

timber from the (Class I) stream protection zone in 

such a way that shading and filtering effects are not 

destroyed. 

No specific references were found. See Rule 3.g.iii., 

general buffer strip rule (BMP 71), and the General 

Erosion Research Summary. 

BMP 78-Rule 3.g.iii.(d). and (e). Leave standing 

trees, including conifers, hardwoods, and snags (snags 

within given limitations), within 50 feet of the ordinary high water mark on each side of all Class I 

streams in the given minimum numbers per 1,000 feet 

of stream (first alternative). 

No references were found. 

BMP 79--Rule 3.g.iii.O. Request a site-specific 

riparian management prescription as an alternative 

to the standing tree and shade requirements for Class I 

streams (second alternative). 

No references were found. 

BMP &Rule $.g.iii.(g). Where the opposite side of 

the stream does not currently meet the given minimum standing tree requirements, consider a sitespecific riparian prescription that meets the large 

organic debris needs of the stream (Class I). 

No references were found. 

BMP 81-Rule 3.g.i~. Provide soil stabilization and 

water filtering effects along Class I1 streams by leaving undisturbed soils in widths sdticient to prevent 

washing of sediment into Class I streams. In no case 

shall this widthbe less than 5 feet slope distance above 

the ordinary high water mark on each side of the 

stream. 

See rule 3.g.iii., Class I buffer zones (BMP 71); rule 

4.b.i., buffer strips below roads (BMP's 86 through 88); 

and the General Erosion Research Summary. 

Rule 3.h. Maintenance of Productivity 

and Related Values 

Three BMPs (82 through 84) were evaluated. These 

comprise the "wet areas" Rule 3.h.iii.: 'When conducting operations along bogs, swamps, wet meadows, 

springs, seeps, wet draws, or other sources where the 

presence of water is indicated, protect soil and vegetation from disturbance that wouldcause adverse effects 

on water quality, quantity, and wildlife habitat. Consider leaving buffer strips." Other rules in 3.h. deal 

with wildlife and esthetic values and were not within 

the scope of the BMP project. 

No research was found specifically addressing the 

wet area BMPs. See the General Erosion Research 

Summary, the timber harvest buffer strip rule (BMP 

71), and the road buffer strip rules (BMP's 86 through 

88). 

Research Results by Best Management 

Practice 

BMP 82-Rule 3.h.iii. When conducting operations 

along lakes, bogs, swamps, wet meadows, springs, 

seeps or other sources where the presenceof water is 

indicated, protect soil from disturbance that would 

cause adverse effects on water quality, water quantity, wildlife habitat, and aquatic habitat. 
No specific references were found. See the General 

Erosion Research Summary; Rule 3.g.iii., timber harvest buffer strips (BMP 71); and Rule 4.b.i., road buffer 

strips (BMP's 86 through 88). 

BlMP 83-Rule 3.h.iii. When conducting operations 

along lakes, bogs, swamps, wet meadows, springs, 

seeps or other sources where the presence of water is 

indicated, protect vegetation from disturbance that 

would cause adverse effects on water quality, water 

quantity, wildlife habitat, and aquatic habitat. 

No specific references were found. See the General 

Erosion Research Summary; Rule 3.g.iii., timber harvest buffer strips (BMP 71); and Rule 4.b.i., road buffer 

strips (BMP's 86 through 88). 

BMP 84--Rule 3.h.iii. When conducting operations 

along lakes, bogs, swamps, wet meadows, springs, 

seeps or other sources where the presence of water is 

indicated, consider leaving buffer strips. 

No specific references were found. See Rule 3.g.iii., 

timber harvest buffer strips (BMP 71); and Rule 4.b.i., 

road buffer strips (BMP's 86 through 88). 
Rule 4. Road Construction 

and Maintenance 
Rule 4.b. Road Specifications and 

Plans 

Twenty-four BMP's (85 through 108) were evaluated. Five major themes regarding road planning are: 

Minimum disturbance, including minimum road 

standard, minimum cut and fill volumes, and 

minimum road width (BMP's 85, 89 through 91, 

93,941; 

Road buffer strips: minimum road construction 

within the stream protection zone, and providing 

for vegetation between roads and streams (BMP's 

86 through 88); 

Disposition of excavated material (BMP's 92,95, 

96); 

Road drainage, culverts, and stream crossings 

(BMP's 97 through 107); 

Reuse and reconstruction of existing roads (BMP 

108). 

Minimum Disturbance 

Several studies have implications for roadcut volumes. Two studies (Burroughs and others 1972, p. 11; 

Megahan 1972, p. 355) showed that even relatively low 

roadcuts can intercept significant amounts of surface 

and subsurface snowmelt runoff, disturbing slope hydrology and creating potential road drainage and 

erosion problems. ' 

In the Horse Creek Study Area, ditch aggradation 

increased as cut height increased (Tennyson and others 1981, pp. 55, 70). Also, as roadcut area or height 

increased, cutslope erosion volumes increased (King 

1981, pp. 83,101; Tennyson and others 1981, pp. 16, 

21). However, in the Silver Creek Study Area, cut 

height was not a significant variable in predicting 

surface erosion (Boise State University, Department 

of Geology and Geophysics 1984, pp. 16,30,31). 

The Silver Creek study correlated cutslope gradient 

with cutslope erosion (p. 18). The same conclusion was 

reached in a study of long-term (45-year) cutslope 

erosion in the same area (Megahan and others 1983, 

pp. 24, 25). The authors recommended constructing 

cutslopes at lower gradients on gentle terrain and 

using terraced slopes on steeper terrain (p. 27). On the 

other hand, Gonsior and Gardner (1971, p. 33) recommended building cuts "as steep as possible consistent 

with subsurface conditions."Megahan andBohn(l989, 

P. 508) noted that progressive mass failures can occur 

at relatively low slope gradients under certain conditions of subsurface flow; hazards are increased if 

timber has been harvested above the roadcut (p. 509). 

Jensen and Finn (1966, p. 8) suggested that on glacial 

moraine lands, roadcuts should be laid back to 1.5:l or 

67 percent, to prevent round glacier-packed boulders 

from rolling out of the roadcut. 

Several reports of fillslope erosion in the Horse 

Creek Study Area showed that erosion increased with 

fill height (Cook and King 1983, pp. 3-4; King 1979, 

pp. 5,6; King 1981, p. 83; Tennyson and others 1981, 

pp. 13,15, 16). In the Gospel Hump area, fill length 

and vertical fill height (along with time since construction) were the best predictors of fill erosion volumes, 

and were also highly correlated with sediment transport distances (Carlton and others 1982, pp. 31, 32, 

39). In the Idaho Batholith, Megahan (1974a, p. 11) 

reported greater tree growth in the upper fourth of fills 

averaging 200 feet in length. The study showed that 

the planted trees significantly reduced surface erosion 

(pp. 13-14); other research studies indicated that 

the trees should also reduce the risk of mass erosion 

(pp. 2-31. 

Several studies in the Idaho Batholith addressed the 

importance of fillslope gradient with respect to surface 

andmass erosion. Jensen and Cole (1965, p. 13) reported 

that the major cause of fill failures in the South Fork 

Salmon River drainage was the location of roads on 

steep slopes when the natural angle ofrepose ofthe fill 

material (67 percent or 1.5:l) was exceeded or approached too closely to allow a margin of safety. They 

recommended that fills be built at an angle of 50 

percent or 2:l (p. 13); if fill lengths are limited, this 

puts constraints on road siting based on hill slope 

gradients (p. 14). Investigations of slope failures 

(Gonsior and Gardner 1971, pp. 30-31) revealed that 

slope steepness was a major factor in all road-associated failures. Based on laboratory tests, they recommended that "no unretained slopes should be allowed 

in excess of 35 degrees, or 70 percent, on roadfills." It 

was also noted that steep slopes were more prone to 

surface erosion of fine particles. However, for plot 

studies in the Silver Creek Study Area, fillslope gradient was not a statistically significant predictor of 

sediment yield over the range of the data set, 34 to 41 

degrees (Megahan and others 1991, pp. 54-56; Megahan 

and others 1992). 

Hartsog and Gonsior (1973, p. 6) reported that 

roadfills designed for 67 percent, but constructed at 

the angle of repose (70-80 percent), showed sloughing 

and settlement cracks and eroded during a highintensity rainstorm. Megahan (1974a, p. 1) noted that 

investigations by the Payette National Forest concluded that fills constructed at angles exceeding the 

natural angle of repose could not be stabilized by grass 

seeding (p. 1). 

Some studies looked at combinations of cut, fill, and 

tread. Based on investigations of mass failures in the 

Idaho Batholith, Gonsior and Gardner (1971, p. 33) 

recommended sacrificing road alignment to avoid deep 

cuts and fills. Similarly, Hartsog and Gonsior (1973, 

p. 21) recommended minimizing heights of cuts and 

fills, and tread width to reduce road erosion. Ketcheson 
and Megahan (1990, pp. 4-51 found that sediment flow 

volume and travel distances increased as total source 

areas (including cut, fill, tread, andundisturbed sIopes 

contributing sediment) increased. Earlier investigations by Haupt (1959b, pp. 330-331) suggested that fill 

length, but not cut height or road width, predicted flow 

distance. Packer (1967, pp. 12-13) did not find cut, fill, 

or tread dimension variables to be significant predictors of sediment flow distance. 

The relative importance of cut, fill, and tread as 

sources of surface and mass erosion were discussed in 

several reports (Arnold and Lundeen 1968, p. 117; 

Burroughs and King 1989, p. 16; Jensen and Cole 

1965, p. 11; Jensen and Finn 1966, p. 70; King 1981, 

p. 106; Megahan and Kidd 1972a, pp. 10-11; Megahan 

and others 1979, p. 131). See Research Results by Best 

Management Practice, BMP 85, Road Construction 

and Maintenance, for details. 

Three studies specifically addressed road standard. 

Megahan and others (1979, p. 131) found that as road 

standardincreased, so did the frequency of landslides. 

They attributed the increased landslides to the increased volume of material excavated. King (1981, p. 

76) noted that regardless of the intended road standard, the area disturbed was often a function of topographical constraints and location of the road within 

the landscape. In the Horse Creek Study Area, road 

standard was not as important as sideslope characteristics in predicting sediment transport distance (King 

1979, p. 9). 

Road Buffer Strips 

Twelve studies reported on sediment movement 

below roads; some of these tried to identify the variables controlling the distance of sediment movement. 

Variables that seem to be important include: obstructions on the slope, road drainage features, fillslope 

characteristics, and site characteristics. Time since 

construction and weather also play a role. 

Several of these studies noted the importance of 

obstructions (including vegetation) on the slope below 

the road. For example, Haupt (1959b, pp. 330-331) . found that the "slope obstruction index," related to the 

downhill spacing of obstructions, was the variable 

most highly related to transport distance. Major slope 

obstructions included in the index were "standing 

trees, down snags, logging slash and fallen branches 

greater than 3 inches in diameter, rock outcrops, 

clumps of brush higher than 2 feet, tree stumps, 

hummocks, and natural depressions." Grass and low 

brush between major obstructions were also considered when computing the index. 

Packer and Christensen (1964, pp. 7,9) noted that 

slope obstructions vary in their ability to retard sediment flow. The following were listed in order of decreasing effectiveness: 

(1) Depressions made by pushed-over or wind-thrown 

trees, or a wavy ground surface; 

(2) Logs thicker than 4 inches; 

(3) Rocks more than four inches wide at ground 

surface; 

(4) Trees and stumps; 

(5) Slash and brush; 

(6) Grass, weeds, and shrubs. 

Using this classification for 720 sites in Idaho and 

Montana, Packer (1967, pp. 12-13) reported that obstruction spacing, and the interaction of obstruction 

spacing and obstruction type, were the variables most 

highly related to sediment transport; initial obstruction distance was also significant (ranking fifth among 

the variables). 

c In the Gospel Hump area, the obstruction index was 

a statistic- significant variable in explaining sediment transport distances (Carlton and others 1982, 

pp. 38-39). In this case, the obstruction index was a 

measure of the relative efficiency of obstructions in 

blocking the flow of sediment (pp. 17,82). Ketcheson 

and Megahan (1990, p. 11) noted that obstructions can 

deflect or stop sediment flow if they are large, in 

contad with the ground, and oriented perpendicular 

to the fall line of the slope. Small stems are generally 

ineffective in deflecting or stopping sediment flow. 

Based on Ketcheson and Megahan's study, Burton 

(n.d., p. 2) reported a strong correlation between sediment storage behind obstructions and lengths of sediment flow in the Silver Greek Study Area. Length of 

obstructions was one of four variables in an equation 

predicting sediment flow travel distances (p. 3). 

Filter windrows are a special kind of obstruction 

purposely placed at the toe of the fill. Research in the 

Horse Creek Study Area (Burroughs and King 1989, 

p. 9; Cook and King 1983, p. 4; King 1979, pp. 9-10; 

Tennyson and others 1981, p. 41) has shown slash 

filter windrows to reduce movement of sediment below 

filldopes. The length of windrows constructed at five 

stream crossings totalled 1,190 feet. Only seven sediment flows were observed below the windrowed fills in 

the 3-year study period; three of these had sediment 

delivery to the stream. Breaching of windrows usudy 

occurred as a result of slumping when snowmelt saturated the fill. Average transport distance for sediment 

flows was 3.8 feet below'windrows. For fills without 

lCilter windrows, the average transport distance was 

41.4 feet for flows originating in slumps, and 24.2 feet 

for flows originating in areas that had not slumped 

(Cook and King 1983, pp. 2-4). 

Road drainage features are another important factor influencing sediment movement below roads. Haupt 

(195913) looked at various road design and site factors 

as predictors of sediment flow distance below logging 

roads that had been "put to bed" (standard logging 

road closure techniques that include cross ditching 
and removal oftemporary culverts) (pp. 329-330). This 

analysis showed that the cross ditchinterval squared, 

and the product of cross ditch interval and road gradient, ranked second and fourth among the variables 

tested (pp. 330-331). A similar exercise by Packer 

(1967, pp. 12-13) showed that of 24 watershed and 

road characteristics tested as predictors of sediment 

movement downslope from logging roads, cross drain 

spacing was fourth in importance. 

When roads were being constructed in the Silver 

Creek Study Area, sediment flows associated with 

berm drains or cross drains (relief culverts) had greater 

volumes and traveled farther than those originating 

on fillslopes (Megahan and others 1986, pp. 35-36). 

The same pattern held in the 4 years after construction (Ketcheson and Megahan 1990, p. 3). Probability 

distributions were developed for sediment flow volume and length by source, including relief culverts, 

berm drains, and rock drains (pp. 9-10,13-16). 

Similarly, in the Horse Creek Study Area, sediment 

flows influenced by relief culverts (where the source 

gully was below or adjacent to a culvert) tended to 

travel farther than other flows (Tennyson and others 

1981, pp. 41-42). Presence or absence of runoff from 

the road surface was an important variable in predicting sediment flow distance (p. 44). Burroughs and 

King (1989, p. 10) developed'frequency distributions of 

sediment transport distance for flows influenced by 

relief culverts, and for travelway runoff compared 

with no travelway runoff, based on the Horse Creek 

data. 

Fillslope characteristics that appear to influence the 

distance of sediment transport include fillslope length 

or height, cover density, gullying or slumping, bulk 

density, and parent material. The relation between 

sediment transport and fillslope length or vertical 

height was discussed in the previous section on minimum disturbance. See Haupt 1959b, pp. 331-332; 

Tennyson and others 1981, pp. 43-44; Carlton and 

others 1982, pp. 38-39. Fillslope cover density was the 

seventh most important variable in Packer's (1967, 

pp. 13,15-16) analysis of sediment transport distance. 

Several reports from the Horse Creek Study Area 

indicate that sediment transport distances increase 

as source gully volume increases (King 1979, p. 6; 

Tennyson and others 1981, pp. 43-44); slumped material is transported greater distances than unslumped 

material (Burroughs and King 1989, p. 9; Cook and 

King 1983, p. 4; Tennysonandothers 1981, p. 41). Bulk 

density of fill material was a significant predictor of 

transport distance in the Gospel Hump area (Carlton 

and others 1982, pp. 38-40). Parent material will be 

discussed in the next section. 

Site characteristics potentially important to sediment transport include the parent material and the 

sideslope gradient. For example, in Packer's analyses 

(1967, pp. 12-14), the thirdmost important predictor of 

sediment transport distance was percentage by weight 

of undisturbed slope soil particles and water-stable 

aggregates greater than2 mm in diameter. The following soil groups were listed in order of decreasing 

percentages (and increasing sediment movement)': basalt, andesite, glacial silt, hard sediments, granite, 

and loess. In the Gospel Hump area, sediment flows 

originating from nongranitic fill materials were predicted to travel about 5 feet farther than those from 

granitic fill materials (Carlton and others 1982, p. 47). 

In Haupt's study (1959b, p. 331) the lower sideslope 

gradient was not significant, which was attributed to 

the confounding effect of slope obstructions. However, 

in the Horse Creek Study Area, King (1979, pp. 8,9) 

reported that as slope gradient increased, larger volumes of sediment were transported greater distances 

in the first year after construction. In the same area, 

Tennyson and others (1981, pp. 43-44) found slope 

gradient to be a significant predictor of sediment 

transport distance in the second year following construction. Reports from the Silver Creek Study Area 

also indicate that gradient influenced sediment 

transport distances (Burton n.d., p. 3; Ketcheson and 

Megahan 1990, p. 5). Sideslope gradient was one of 

four independent variables in the equation predicting 

transport (Burton n.d., p. 3). 

Despite this research on sediment transport below 

roads, transport is still difEcult to predict accurately 

due to the numerous interacting variables (Burroughs 

and King 1989, p. 8). While individual variables may 

test highly significant, the predictive multiple regression equations generally have low r-squared values, 

indicating they predict only a small fiaction of the 

variability (Carlton and others 1982, pp. 39-40; Packer 

1967, p. 13; Tennyson and others 1981, pp. 41, 44). 

Another approach is to report the distribution of sediment flows in time and space. Several such reports are 

available (Burroughs andKing 1989, pp. 9-11; Carlton 

and others 1982, p. 38; Haupt and Kidd 1965, p. 668; 

Ketcheson and Megahan 1990, pp. 3,9-10,12-16; King 

1979, pp. 6,8,9; Megahan 1991, p. 146; Megahan and 

others 1986, pp. 35-36; Tennyson and others 1981, pp. 

39,41,42,44); see Research Results by Best Management Practice for BMPYs 86 through 88. This approach 

may provide useful information, but the unique circumstances of site conditions, road design, and weather 

that produced a given data set are unlikely to be 

duplicated elsewhere. 

Buffer strips may be desirable not only for limiting 

sediment delivery from roads to streams, but also for 

reducing mass and surface erosion. For example, 

Gonsior and Gardner (1971, pp. 31-32 ) recommended 

leaving trees below roadfills because tree roots enhance soil stability by mechanical reinforcement and 

by removing moisture. Similarly, Gray and Megahan 
(1981, pp. 20-21) suggested leaving trees above and 

below haul roads, based on their analyses of the 

contributions of forest vegetation to slope stability 

through various mechanisms. See the General Erosion Research Summary for more information on the 

influence of vegetation on surface and mass erosion. 

Disposition of Excavated Material 

Only one reference was found. Clayton and Arnold 

(1972, p. 16) suggested borrowing fill for placement in 

areas of very well weathered granitic rock, to promote 

fillslope stability. See the General Erosion Research 

Summary for information on geologically stable sites. 

Road Drainage, Culverts, Stream Crossings 

Four reports were found that compared the relative 

merits of insloping with outsloping (Burroughs and 

King 1989, p. 16; Gonsior and Gardner 1971, p. 33; 

Hartsog and Gonsior 1973, p. 20; Haupt and others 

1963, p. 8). All concluded that insloping was generally 

preferable; outsloping requires special attention to 

road design, erosion control measures, and maintenance. 

Dips, water bars, and cross drains were discussed in 

four references. Haupt and others (1963, pp. 6-7)noted 

that earthen cross drains spaced 30 to 90 feet apart 

generated erosion on both insloped and outsloped road 

sections during severe storms. If earthen cross drains 

are used, they recommended draining them on the 

outcurve (p. 8). Based on their analyses of the contributions of vegetation to slope stability, Gray and 

Megahan (1981, p. 21) recommended that road cross 

drainage structures should drain onto undisturbed 

vegetation. 

Both Haupt (1959b, pp. 330-331) and Packer (1967, 

pp. 13-14) found spacing of cross drainage structures 

to be a significant variable with respect to sediment 

flow distance. Haupt (1959a) used his regression equation to develop tables for use in road design, construction, and abandonment. Various tables can be used to 

estimate the buffer strip widths, cross ditch interval, 

or slope obstruction index to minimize sediment delivery to streams for a wide range of road and site 

characteristics (pp. 9-20). Similarly, Packer (1967) 

developed a table (pp. 16-17) using his regression 

equation (p. 12) to define buffer strip width given 

obstruction spacing and obstruction types with adjustments for soil type, cross drain spacing, distance to 

initial obstruction, fillslope cover density, the percent 

of erosion prevention, and so forth. A table with the 

same information also appears in the publication by 

Packer and Christensen (1964, pp. 15-17). 

Packer (1967) also investigated cross drain spacing 

needed to prevent formation of road surface rills exceeding 1 inch in depth. Significant variables, in order 

of importance, were: road surface stability, road surface 

grade, topographic position, aspect, and upper slope 

steepness (pp. 6-71. The regression equation (p. 6) was 

used to develop a table (p. 11) that gives cross drain 

spacings by road grade and soil type with adjustments 

for topographic position, aspect, slope steepness, and 

the percent of cases in which 1-inch rill formation is 

prevented. This table is found on page 14 of the report 

by Packer and Christensen (1964), who also provided 

guidelines for installation of some cross drainage structures (pp. 33-36). 

Te~yson and others (1981) measured ditch aggradation and degradation on a newly constructed road. 

During snowmelt periods, ditches generally degraded 

(deepened); distance between culverts and road gradient were significantly and positively correlated with 

degradation (pp. 55, 70). During the first snowmelt 

period, ditches on roads withgradients of 6 to 9 percent 

degraded an average of 0.122 feet (p. 55). During 

summer, aggradation (filling) was more common; 

aggradation was significantly and positively correlated with cutslope height (p. 70). In general, deposition was observed in the first 100 feet of the ditch; 

erosion increased with increasing distances along the 

ditch (pp. 57-58). 

Experiments with simulated rainfall on the Nez 

Perce National Forest indicate that degradation of an 

unprotected ditch might produce more sediment than 

an unprotected road tread on roads with low volumes 

of traffic (Burroughs and King 1989, p. 14). In these 

experiments (Burroughs and others 1983b, p. 14), the 

ratio of sediment yields were: 

(unrocked ditch + untreated cutslope) : 

(rocked ditch + untreated cutslope) = 2.29. 

Burroughs and King (1989, pp. 13-14) outline procedures for designing roadside ditch riprap for forest 

roads. 

In the Silver Creek Study Area, results from 

preconstruction seismic and resistivity surveys were 

used to accurately predict the necessary drainage 

design and to plan underdrain installation on a new 

collector road (Clayton 1983, p. 5). 

Several studies reported on sediment movement 

below relief culverts (Burroughs and King 1989; 

Ketcheson and Megahan 1990; Megahan and others 

1986; Te~yson and others 1981). These studies were 

summarized under "Road Buffer Strips" (pp. 30-31). 

Gray and Megahan (1981, p. 21) recommended leaving undisturbed vegetation in areas large enough to 

accommodate road drainage (water spreading areas) 

based on their analyses of slope stability. Megahan 

and others (1979, p. 131) studied the relationship 

between culverts and landslide frequency, volume, 

and delivery. Twenty-seven percent of road-associated 

slides originated on roadfills without culverts, 
compared to 7 percent on fills with culverts. Thirtyone percent of the volume from road-associated slides 

originated on fills without culverts, compare3 to 21 

percent on fills with culverts. Fifty-one percent of the 

road-associated slide material delivered to streams 

originated on fills without culverts, compared to 16 

percent that originated on fills with culverts. 

Several reports addressed culvert installation and 

stream crossings. Innorthern Idaho, Bachmann (1958, 

pp. 22,35,37) observed temporarily increased turbidity and a sediment deposit associated with culvert 

installation. Increases in sedimentation and turbidity 

were noted at crossings of some small tributaries 

(p. 25). Over the course of the study, increases in 

turbidity were noted only during rain, snowmelt, and 

direct channel disturbances; sediment sources were 

predominantly at stream crossings (pp. 35, 37). Although turbidity sampling was not adequate to define 

average or maximum values (p. 37), turbidity differences were apparent above and below road crossings 

(p. 35). 

In the Horse Creek Study Area, sediment increases 

were observed when roads were pioneered, temporary 

culverts were placed, slash was cleared from the rightof-way, and culverts were permanently installed (King 

1981, pp. 62,67). Routing the streamflow around the 

construction site when culverts were permanently 

installed, "dewatering," reduced sedimentation (King 

and Gonsior 1980, p. 9). Shortly after construction, 

sediment concentrations at the crossings returned to 

preconstructionlevels, except duringrainstorms. Then, 

sediment loads were about 100 to 1,000 times higher 

than normal (p. 11). During the first snowmelt period 

following construction, considerable sediment was 

generated at crossings (p. 11). The following summer 

(1 year after construction), sediment loads during 

storms were about 10 times higher than normal (p. 15). 

Three references provided recommendations for culvert design and installation. Based on their observations of storm damage to logging roads, Haupt and 

others (1963, p. 8) recommended that culverts placed 

in major ravines be laid on the original grade so that 

they drain into the original channel rather than on the 

fill of the incurve. Hartsog and Gonsior (1973) recommended skewing culverts or using downspouts to 

avoid steep culvert gradients that result in scour 

(p. 10). They also discussed proper bedding of culverts 

and compaction of backfill material (p. 12). Gonsior 

and Gardner (1971, p. 12) measured low soil permeabilities in their investigations of slope failures, noting that decreasing permeability over time must be 

accounted for in culvert planning. They stressed the 

need to evaluate surface and subsurface flow conditions when locating and designing roads (p. 33). No 

references were found on planning culvert installation 

to provide for fish passage. 

Hartsog and Gonsior (1973, p. 21) stressed the need 

for careful planning to control sediment from the 

road's cutslope and ditch. They recommended routing 

water down the road surface rather than along the toe 

of the cutslope. They also recommended providing for 

sediment filtering or settling before runoff leaves the 

road surface, or for discharging drainage far enough 

away from streams to provide for water infiltration 

and clarification. 

Reconstruction of Existing Roads 

No references specifically addressed reconstruction 

versus new road construction; however, numerous 

references show that total erosion or erosion on various components of the road prism decreases over time 

(ranging fiom the first season to the first 3 years). 

Megahan (1974b) has the largest data set spanning 

the longest time. He has dealt most directly with the 

trend of erosion. He developed a negative exponential 

equation showing surface erosion on severely disturbed granitic soils over time. By far the greatest 

percentage of erosion occurs in the first and second 

years after construction (p. 12). In the first year, 

erosion rates are about 1,000 times greater than on 

undisturbed lands (p. 12). Additional disturbances 

result in new cycles of surface erosion (p. 13). 

Research Results by Best Management 

Practice 

BMP 86-Rule 4.b. Plan each road to the minimum 

use standards adapted to the terrain and soil materials to minimize disturbances and damage to forest 

productivity, water quality, and wildlife habitat. 

To avoid repetition, and to consider interactions 

among variables, this rule will be combined with the 

rules for minimum road width, minimum cut volumes, 

and minimum fill volumes (BMP's 89, 90, and 91). 

Each reference will indicate whether it pertains to 

road standard, road width, roadcut volume, roadfill 

volume, or some combination. See the General Erosion 

Research Summary regarding the requirement 

"adapted to the terrain and soil materials." 

It is intuitively clear that minimizing the area disturbed in cuts, tread and ditch, or fill should reduce 

erosion. However, other factors such as cut and fill 

angles must also be considered. 

Haupt 1959a,b, width, cut, fill, Little Owl Creek 

watershed, Boise River basin-Haupt (1959b), tested 

seven variables, including road width, roadcut height, 

and embankment slope length as predictors of sediment flow distance below logging haul roads that had 

been "put to bed" (standard logging road closure 

techniques that include cross ditching and removal of 

temporary culverts). Multiple regression analysis 

showed that the "slope obstruction index" was the 
most highly related, followed by the cross ditch 

interval squared, the embankment slope length, and 

the product of cross ditch interval and road gradieht 

(pp. 330-331). In the regression equation, an increase 

of 1 foot of embankment slope length increases sediment flow distance by about 3.5 feet Cp. 332). The range 

of embankment slope lengths used to develop the 

equation was 1 to 32 feet (p. 331). Haupt (1959a) cautioned against extrapolating beyond a 20-foot embankment slope length (p. 6). 

Jensen and Cole 1965, fill, South Fork Salmon River 

drainage-A survey of mass erosion during an April 

1965 rain and snowmelt event showed that 77.5 percent of the landslides originated on roadfills (p. 11). 

The major cause of fill failures was the location of 

roads on steep slopes such that the natural angle of 

repose of the fill material (67 percent or 1.5:l) was 

exceeded or approached too closely to allow a margin 

of safety(p. 13). They recommended building fills at an 

angle of 50 percent or 2:l (p. 13). If fills are to be less 

than 100 feet long, this recommendation would limit 

construction to slopes with gradients less than or 

equal to 45 percent. If fills are to be less than 50 feet 

, long, this recommendation would limit construction to 

slopes with gradients less than or equal to 38 percent 

(P. 14). 

Jensen and Finn 1966, width, cut, fill, Zena Creek 

Logging Study Area, Payette National Forest-Rates 

are given for average yearly surface erosion from cut, 

tread or ditch, and fill. Information is provided for four 

landtypes: strongly glaciatedgranitic soils, periglacial 

(ice action mainly on site) granitic soils, river terrace 

lands, and decomposed granitic soils. For strongly 

glaciated granitic soils and river terrace lands, the 

values for all road prism components are 0.1 inch 

surface erosion per year. For periglacial granitic soils, 

the cut value is 0.2 inch, the tread and ditch and the fill 

values are 0.1 inch. For the decomposed granitic soils, 

the cut value is 1.0 inch, the treadandditchvalue is 0.1 

inch, and the fill value is 0.5 inch (p. 70). 

The authors recommend minimizing roadcutting 

operations on decomposed granitic soils and on the 

face of river terraces (pp. 4,8,28,32,62). On decomposed granitic soils, road construction on slopes over 

45 percent requires slope stabihationmeasures (p. 8). 

On glacial moraine lands, roadcuts should be reduced 

in steepness to 1.5:l or 67 percent, to prevent round 

glacier-packed boulders from rolling out ofthe roadcut 

(p. 8). 

Packer 1967, width, cut, fill, 720 sites in Idaho and 

Montana-Twenty-five road and watershed characteristics were tested as predictors of sediment 

movement distance downslope from road cross drains 

(pp. 4-5). Among these variables were cut height and 

gradient, fill length and gradient, and road width; 

however, none of these appeared in the ha1 multipleregression equation (p. 12). 

Arnold and LuncEeen 1968, width, cut, fill, South 

Fork Salmon River 'drainage-A survey of erosion on 

the roads producing the highest sediment levels indicated that 65 percent of sediment originated from 

fillslopes, 10 percent from cutslopes and ditches, 21 

percent from maintenance wasting of cutslope material, and 4 percent f?om road surfaces (p. 117). 

Gomior and Gardner 1971, cut, fill, Zena Creek 

drainage, Payette National Forest-Investigations of 

slope failures revealed that slope steepness was a 

major factor in all road-associated failures. Based on 

laboratory tests, the authors recommended that "no 

unretained slopes should be allowed in excess of 35 

degrees, or 70 percent, on roadfills." They also noted 

that steep slopes were more prone to surface erosion of 

fine particles (pp. 30-31). 

The authors recommended buiIding cutslopes, "as 

steep as possible consistent with subswtkce conditions," and sacrificing alignment to avoid deep fills or 

cuts (p. 33). 

Burroughs and others 1972, cut, near Lolo Pass at 

the Idaho-Montana border-Substantial volumes of 

water were intercepted at roadcuts with an average ' 

height of 36 inches (p. 3) during the snowmelt season 

in the deep snow zone (p. 11). Subsurface seepage 

averaged 58 percent of the total, the remainder occurred as overland flow (p. 10). In the central Idaho 

Batholith, such overland flow from snowmelt is seldom observed(p. 12). See Megahan (1972) for information on a similar study in the Idaho Batholith. 

Megahan 1972, cut, Pine Creek, Boise National Forest-Subsurface flow interception was measured along 

roadcuts deep enough to expose bedrock (average soil 

depth was about 31 inches) in first order watersheds 

(p. 351). Subsurface flow was intercepted only during 

the spring snowmelt period (p. 353). The volume of 

flow intercepted was about 7.3 times greater than the 

estimated snowmelt runoff from the road area alone 

(p. 355). About 35 percent of the total subsurface flow 

was intercepted by the roadcut (p. 355). More subsurface flow was intercepted in drainage bottoms, but 

flow was not limited to those areas (p. 353). 

See Burroughs and others (1972) for information on 

a similar study. 

Megahan and Kidd 1972a, width, cut, fill, Zena 

Creek Study Area, Payette National Forest-Time 

trends for erosion on logging roads were discussed. 

High initial erosion rates were largely due to fillslope 

erosion; these high rates could be avoided by fill 

stabilization methods (p. 11). Continued accelerated 

road erosion rates were expected due to erosion of 
weathered granitic bedrock on the road tread and 

steep cutslopes (p. 10). 

Hartsog and Gonsior 1973, width, cut, fill, south 

Fork Salmon River drainage, Payette National Forest-During the construction period and the early 

period of use, an engineeringresearch team evaluated 

a road designed to minimize watershed impacts. Fills 

that had been designed for 67 percent, but constructed 

at the angle of repose (70 to 80 percent), showed 

sloughing and settlement cracks, and also eroded 

during a high-intensity rainstorm (p. 6). The primary 

recommendation for future projects was to minimize 

heights of cuts and fills, and widths of tread, sacrificing road alignment as necessary (p. 21). 

Megahan 1974a, fill, Deadwood River drainage, 

Boise National Forest-Previous investigations by the 

Payette National Forest concluded that fills constructed 

at angles exceeding the natural angle of repose could 

not be stabilized by grass seeding (p. 1). This study 

investigated roadfill surface erosion control from various combinations of tree planting, tree seeding, fertilizing, mulching, and netting (pp. 5-6). 

Planted trees significantly reduced surface erosion 

(pp. 13-14); other studies indicated trees should also 

reduce mass erosion (pp. 2-3). Trees grew faster in the 

upper fourth ofthe fillslope thaninlower parts (the fill 

length averaged 200 feet). Megahan suggested the 

increased growth might be due to deeper soils and 

greater moisture nearer the road (p. 11). 

King 1979, standard, fnE, Horse Creek Study Area, 

Nez Perce National Forest-In the first year after 

construction, fill erosion volumes (per 100 feet of road 

length) increased as fillslope height increased (pp. 5, 

6). See King (1981) for an analysis of this trend, 

including additional years of data. 

A survey of rills and gullies found that the largest 

average volumes occurred on fillslopes from 20 to 30 

feet high(p. 6). However, thelargest gullies, which had 

the greatest transport distances, were not related to 

the height of the fill, but to improper drainage from the 

road surface (pp. 6,ll). Transport distances'of material eroded from fillslopes depended more on sideslope 

characteristics below the fills than on the road standard (p. 9). 

See King (1981), Tennyson and others (1981), and 

Cook and King (1983) for additional information. 

Megahan and others 1979, standard, cut, fill, 

Clearwater National Forest and Midde Fork of the 

Payette River drainage, Boise National Forest-In a 

survey of mass erosion, 66 percent of road-associated 

slides originated on roadcuts, 27 percent on roadfills 

without culverts, and 7 percent on fills with culverts. 

Forty-seven percent of the volume originated on cuts, 

31 percent originated on fills without culverts, and 21 

percent originated on fills with culverts. However, 

33 percent of the slide material delivered to streams 

originated on cuts, 51 percent originated on fills without culverts, and 16 percent originated on fills with 

culverts (p. 131). 

When roads were built to lower standards, landslide 

frequency decreased, presumably because less excavation was required. The average number of slides per 

kilometer ofroad was 2.2 for arterial, 1.2 for collector, 

0.6 for service, and0.2 for temporary or terminalroads 

(p. 131). 

King 1981, standard, cut, fill, Horse Creek Study 

Area, Nez Perce National Forest-Length of fillslopes 

was controlled largely by topographical constraints; 

roads designed to minimize cuts and fills (Standard 11) 

always disturbed a greater area than the higher standard roads (Standard I) due to steeper sideslopes in 

the areas where Standard I1 roads were constructed, 

Both road standards had fill gradients of 1.5:l (p. 76). 

Road erosion data were evaluated for 1 to 3 years 

after construction. As the area of roam increased, 

winter erosion increased (p. 81). As roadcut area 

increased, total cutslope erosion increased (p. 101). 

For both cuts and fills, erosion volumes per mile of 

road length increased as cut or fill height increased 

(pp. 83,101). The study compared erosionwhenthe cut 

or fill height was the shortest (category 1) to taller 

heights (categories 2,3, and 4). Height category 1 was 

0 to 10 feet; category2 was 10 to 20 feet; category 3 was 

20 to 30 feet; and category 4 was greater than 30 feet 

for both cuts and fills (pp. 78,96). For fills on all study 

roads, erosion was 6.9 times greater for category 2, 

17.0 times greater for category 3, and 19.5 times greater 

for category 4 (p. 83). On average, for cuts on all study 

roads, erosion was 5.5 times greater for ~ategory2~7.5 

times greater for category 3, and 10.0 times greater for 

category 4 (p. 101). 

For each height category, cut erosion was greater 

than fill erosion; the difference increased as height 

increased (p. 106). Percent differences between cut 

and £ill erosion were 7.0,121.2, and 179.9 for categories 1, 2, and 3, respectively. The average percent 

difference was 98.4. 

See King (1979), Tennyson and others (1981), and 

Cook and King (1983) for additional information. 

Tennyson and others 1981, cut, fill, Horse Creek 

Study Area, Nez Perce National Forest-For one study 

road analyzed, erosion volume per mile of road length 

increased as both cut and fill heights increased (pp. 13, 

15,16,21). See King (1981) for the average increase by 

height category for all study roads (the figures are 

similar in both reports). Aggradation of the ditch 

increased significantly as cutslope height increased 

(pp. 55,701. 

See King (1979,1981), and Cook and King (1983) for 

additional information. 
Carlton and others 1982, fill, Gospel Hump management areas, Nez Perce National Forest-Fillslope erosion on newly constructed (1978 and 1979) logging 

roads was measured in 1980 and 1981, using both 

bordered erosion plots and rill surveys. All fillslopes 

were fertilized, seeded, and hydromulched (p. 13). 

The rill survey data, considered more representative of the actual fillslope erosion volumes (pp. 38,45), 

were used to develop predictive multiple regression 

equations (p. 32). Fill length and vertical fill height, 

along with time since construction, were the variables 

found to be the best predictors of fillslope erosion 

volumes. Slope length andvertical height ofthe fillslope 

were also highly correlated with sediment transport 

distances (p. 39). 

Cook and King 1983, fill, Horse Creek Study Area, 

Nez Perce National Forest-For 3 years &er road 

construction, eroded material was collected in troughs 

below windrowed and nonwindrowed fillslopes in two 

height classes: 0 to 10 feet (class 1) and 10 to 20 feet 

(class 2) (p. 3). All fillslopes had a 1.5:l slope and were 

seeded, hydromulched, and fertilized (p. 2). Erosion 

volumes (in cubic feet per 100 feet ofroad length) were 

greater on class 2 fillslopes for both windrowed and 

nonwindrowed fills (pp. 3-4): 

Erosion volumes 

Windrowed Nonwindrowed 

(ft3 / 100 ft road length) 

Class 1 0.325 35.85 

Class 2 0.650 64.30 

See King (1979, 1981), and Temyson and others 

(1981) for additional information. 

Megahan and others 1983, cut, Silver Creek Study 

Area, Boise National Forest-Long-term (45-year) 

cutslope erosion was positively correlated with original cutslope gradient (pp. 24,25). The authors recommended constructing cutslopes at lower gradients on 

gentle terrain and using terraced slopes on steeper 

terr'ain (p. 27). 

Boise State University, Department of Geology and 

Geophysics 1984, cut, fill, Silver Creek Study Area, 

Boise National Forest-Sediment collected in troughs 

below cutslopes and at the bottom of bordered fillslope 

plots was measured for a period of 3 years after road 

construction. 

No discernible trend was apparent between cutslope 

source area above the trough (which depended on 

cutslope length) and erosion volume (pp. 16,30, 31). 

Cutslope bngths ranged from 10 feet to more than 50 

feet (p. 7). Cutslope sediment yieldincreasedascutslope 

gradient increased, based on a subsample of 40 cutslope 

plots witha range ingradient of 0.95:l to 1.51:l (p. 18). 

See Megahan and others (1991,1992) for results of 

the fill plot data analysis. 

Burroughs and King 1989, cut, fill, Horse Creek 

Study Area, Nez Perce National Forest-Sediment 

entering the stream from the ditch system (representing erosion of the cut, ditch, and 28 percent of the road 

surface) and that entering from the fillslope side 

(representing erosion of the fillslope and 72 percent of 

the road surface) was monitored for 4 years after 

construction (p. 16). At the study site, the cut and fill 

had no erosion control treatment, and the road was 

unsurfaced (p. 15). 

Partitioning of the sediment between the two entry 

sites reversed over time. The first year, 20 percent 

entered from the ditch, and 80 percent from the fillslope 

side. By the fourth year, 83 percent entered from the 

ditch, and 17 percent from the fillslope side. This 

reversal was attributed to stabilization over time of 

the fillslope due to surface armoring and revegetation 

(p. 16). 

Megahan and Bohn 1989, cut, Silver Creek Study 

Area, Boise National Forest-A progressive mass failure (sapping failure) originating in a road cutslope 

was attributed to cutslope construction at a gradient of 

34 degrees. The angle of friction for the soil material 

type is about 33 degrees; failures can occur at half the 

angle of friction when seepage is parallel to the slope 

(p. 508). Mass erosion hazards of this type in the 

cutslope are increased if timber is harvested above the 

roadcut (p. 509). 

Ketcheson and Megahan 1990, width, cut, fill, Silver 

Creek Study Area, Boise National Forest-Sediment 

flows were inventoried from various sources including 

fills, cross drains (relief culverts), berm drains, rock 

drains, and landings. Sediment flow length and volume increased as the area contributing runoff and 

sediment to each of the sources increased (pp. 4-5). 

Megahan and others 1991, fill, Silver Creek Study 

Area, Boise National Forest-Sediment from bordered 

fillslope erosion plots was measured for 3 years after 

road construction (p. 54). Fillslope gradient was not 

a statistically significant predictor of sediment 

yield over the range of the data set, 34 to 41 degrees 

(pp. 54-56). 

See Boise State University, Department of Geology 

andGeophysics (1984) andMegahan andothers (1992) 

for additional information. 

Megahan and others 1992, fill, Silver Creek Study 

Area, Boise National Forest--Sediment from bordered 

fillslope erosion plots was measured for 3 years after 

road construction. No significant difference in fillslope 

erosion was found between design slopes of 

34 degrees (1.33:1), and 37 degrees (1.5:l). Also, no 

significant interactions were found between the two 

design slopes and the three fillslope construction practices (sidecast, layer placement, and controlled compaction). The results were the same when the actual 
fillslope gradients, rather than the design gradients, 

were used. 

See Boise State University, Department of Geology 

and Geophysics (1984), Megahan and others (1991). 

See the General Erosion Research Summary. 

BMP 86-Rule 4.b.i. Plan transportation networks 

to minimize road construction within stream protection zones. 

BMP 87-Rule 4.b.i. Design to leave areas ofvegetation between roads and streams (first alternative). 

BMP 88-Rule 4.b.i. Design to reestablish areas 

of vegetation between roads and streams (second 

alternative). 

Since research with implications for one of these 

three rules generally has implications for the others, 

they will be considered together here. No references 

were found specific to reestablishing vegetation between roads and streams. See the General Erosion 

Research Summary regarding the value of vegetation 

in reducing surface and mass erosion. 

Bachmann 1958, Silver and Crystal Creeks, near 

Pierce-This study investigated the effects of logging 

and logging road construction on selected physical, 

chemical, and biological features of northern Idaho 

trout streams (pp. 2-3), using a paired-watershed 

approach (p. 9). Measured predisturbance (1955 and 

1956) turbidities ranged from 0.25 to 2.10 parts per 

million in Silver Creek, and from 0.6 to 6.9 parts per 

million in Crystal Creek (p. 34). 

In the Crystal Creek drainage, which had road 

construction activity in 1956 and 1957, a vegetated 

buffer strip (width unspecified) was left between the 

road and stream, except at stream crossings. Roadfills 

were not treated at stream crossings (pp. 21-22). 

Temporarily increased turbidity (90 parts per million) 

and a sediment deposit were associated with culvert 

installation (pp. 22, 35, 37). Increases in sedimentation and turbidity were noted at crossings of some 

small tributaries (p. 25). However, most of the material that eroded from the road prism was not delivered 

to the stream due to the distance between the road and 

the stream (p. 25). Increases in turbidity were noted 

only during rainfall, snowmelt, and direct channel 

disturbances; sediment sources were predominantly 

at stream crossings (pp. 35, 37). Although turbidity 

sampling was inadequate to define average or maximum values (p. 37), turbidity was different above and 

below road crossings, and between the roaded and 

unroaded watersheds (p. 35). 

Haupt 1959a,b, Little Owl Creek watershed, Boise 

River basin-Haupt (1959b) looked at various road 

design and site factors as predictors of sediment flow 

distance below logging roads that had been "put to 

bedn (standard logging road closure techniques that 

include cross ditching and removal of temporary culverts) (pp. 329-330). Multiple regression analysis 

showed that the "slope obstruction indexn was the 

variable most highly related to transport distance, 

followed by cross ditch interval squared, embankment 

slope length, and the product of cross ditch interval 

and road gradient (pp. 330-331). Slope obstructions 

included in the index were "standing trees, down 

snags, logging slash, and fallen branches greater than 

3 inches in diameter, rock outcrops, clumps of brush 

higher than 2 feet, tree stumps, hummocks, <and natural depressions" (p. 330). The lower sideslope gradient 

was not significant, because of the confounding effect 

of slope obstructions (p. 331). The regression equation 

can be used to predict necessary buffer strip widths 

under various conditions (p. 332). 

Haupt (1959a) used the regression equation to develop tables for road design, construction, and abandonment. Various tables can be used to estimate the 

buffer strip widths, cross ditch interval, or slope obstruction index necessary to minimize sediment delivery to streams under a wide range of road and site 

characteristics (pp. 9-20). 

Packer and Christensen 1964,720 sites in Idaho and 

Montana-This publication is a field guide for controlling logging road sediment, primarily through the 

control of cross drain spacing and buffer strip widths. 

It is based on the research reported in Packer (1967) 

and on field experience. 

The authors noted that slope obstructions vary in 

their ability to retard sediment flow. In order of decreasing effectiveness they include (pp. 7,9): 

(1) Depressions made by pushed-over or wind-thrown 

trees, or a wavy ground surface 

(2) Logs thicker than 4 inches 

(3) Rocks more than 4 inches wide at ground surface 

(4) Trees and stumps 

(5) Slash and brush 

(6) Grass, weeds, and shrubs. 

A table was developed giving buffer strip widths 

required to prevent sediment delivery in 83 percent of 

cases, based on obstruction spacing and obstruction 

type (p. 16). Adjustment factors are provided to allow 

for soil group, cross drain spacing, distance to first 

obstruction, fillslope cover density, and 97 percent 

prevention of sediment delivery (pp. 15-17). 

Obstruction storage capacity tended to be exceeded 

by the fourth or fifth year after road construction. 

Buffer strips could be narrower if drainage was diverted toward other obstructions or if new obstructions were provided when the road was 3 years old 

(p. 11). 

See Packer (1967) for additional information. 
Haupt and Kidd 1965, Boise Basin Experimental 

Forest, Boise National Forest-An attempt was made 

to minimize erosion associated with logging and loggingroadconstructionin 1953 and 1954 byusingugood 

logging practicesn including careful road location, a 

minimum number of stream crossings, 10-foot minimum buffer strips between roads and streams whenever possible, and seeding and harrowing of roads 

following use (p. 665). 

Sediment flow distances were measured from 1953 

to 1957 and in 1960 (p. 667). Of 104 sediment flows 

below haul roads, 50 percent were less than 5 feet long, 

80 percent were less than 10 feet long, and all were less 

than 30 feet long (p. 668). Severe storms in 1956 

lengthened flows; only six lengthened afier 1956 

(p. 668). 

More than 20 percent of the flows reached stream 

channels (p. 668). The width of the buffer strip was 

apparently critical in preventing delivery. The 8-foot 

mean width of buffer strips through which sediment 

flows reached a channel was significantly different 

from the 30-foot mean width of buffer strips that 

contained flows within their boundaries (p. 669). 

Jensen and Finn 1966, Zena Creek Study Area, 

Payette National Forest-Based on their hydrological 

analysis, the authors recommended limitingroad construction on stream-cut decomposed granite lands to 

the ridgetops. If roads are built elsewhere, cuts and 

fills should be fully stabilized and intercepted subsurface flow should be routed in a manner least disruptive to the natural patterns (pp. 8,321. 

Packer 1967,720 sites in Idaho and Montana, representing six major soil groups-Twenty- four watershed 

and road characteristics were tested as predictors of 

sediment movement downslope from logging roads. 

The significant variables, in order ofimportance, were 

obstruction spacing, the interaction of obstruction 

type and obstruction spacing, undisturbed slope stability, cross drain spacing, initial obstruction distance, 

age of road, and fillslope cover densityl(pp. 12-13). A 

multiple regression equation was developed (p. 12), 

and was also representedin a tabular form (pp. 16-17). 

This is essentially the same table as that in Packer and 

Christensen (1964, pp. 15-17), except that distances 

are measured from the shoulder of the road rather 

than from the centerline. 

See Packer and Christensen (1964) for additional 

information. 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-The authors conducted field 

and laboratory investigations of slope failures and soil 

properties. They recommended leaving barriers of live 

trees below all road fillslopes so their roots could 

enhance soil stability through mechanical reinforcement and by depleting soil moisture (pp. 31-32). 

Megahan and Kidd 1972a, Zena Creek Study Area, 

Payette National Forest-A barrier of logs and debris 

substantially lowered sediment yields from logging 

roads by intercepting sediment flows on one of three 

study watersheds (pp. 5-6). 

King 1979, Horse Creek Study Area, Nez Perce National Forest-Travel distances for sediment flows 

resulting from rill and gully erosion of roadfills were 

evaluated for 1 year following road construction. Gullies with the largest volumes of erosion had greater 

transport distances (p. 6). The relationship between 

percent of eroded volume deposited and distance below the road was curvilinear (pp. 6,8,9). The majority 

of the material was transportedless than 20 feet in the 

first year (pp. 6, 8, 9). As slope gradient increased, 

larger volumes were transported greater distances 

(pp. 8,9). Sediment transport distance appeared to be 

related more to sideslope characteristics than to the 

road design standard (p. 9). 

Filter windrows were very effective in limiting material available for transport (0.22 cubic feet of eroded 

material per 100 feet of road length) in the first year 

after road construction (pp. 9-10). 

See Tennyson and others (1981), Cook and King 

(1983), and Burroughs and King (1989) for followup 

reports. 

Gray and Megahan 1981, Pine Creek Study Area, 

Middle Fork of the Payette River drainage, Boise National Forest-Analyses evaluated the contributions 

of forest vegetation to slope stability through various 

mechanisms. The authors recommendedleaving buffer 

zones of trees above and below haul roads, and leaving 

buffer zones ofundisturbedvegetation along all streams 

during clearcut logging operations (pp. 20-21). 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-Travel distances for 

sediment flows resulting from rill and gully erosion 

of roadfills were evaluated for 2 years after road 

construction. 

Transport distances were variable (pp. 39,41, 42). 

The maximum flow distance was 150 feet (p. 41). 

Flows influenced by relief culverts (those with the 

source gully below or adjacent to culverts) tended to 

travel farther than other flows (p. 41). Flows originating from rills and gdhes in slumps had greater average travel distances than those originatingin fill areas 

that did not slump, 41.4 feet compared to 24.2 feet 

(p. 41). No sediment was transported beyond fills with 

slash filter windrows the first year after construction; 

average sediment flow distance below windrows was 

3.8 feet the second year after construction (p. 41). The 

average transport distance for all flows was 11.2 feet 

at the beginning of the study, and 26.3 feet 2 years 

later (p. 42). For flows not associatedwithwindrows or 

relief culverts, an average of 73 percent ofthe material 
was deposited within 50 feet of the roadfill 2 years 

after construction (p. 44). 

Regression models of sediment transport had low 

predictive values, probably due to the omission of 

important variables such as obstruction information. 

Gully volume was the most important predictor of 

travel distance for both the first and second year; the 

presence or absence of runoff from the road surface 

was also important. For the second year, fillslope 

height and sideslope gradient were also significant 

(pp. 41,43,44). 

See King (1979), Cook and King (1983), and 

Burroughs and King (1989) for additional information 

Carlton and others 1982, Gospel Hump Management Areas, Nez Perce National Forest-Rill, gully, 

and slump surveys (pp. 16-17) were conducted from 

spring 1980 through fall 1981 on fills of roads constructed in 1978 and 1979. All fillslopes had been 

fertilized, seeded, and hydromulched (p. 13). 

Excluding sediment flows influenced by culverts, 

average downslope transport of sediment below the 

fills was 8.4 feet, varying from 0 to 53 feet (p. 38). 

Several variables were significantly correlated with 

transport distance, including fillslope length and vertical height, sediment volume, bulk density, and obstruction index (pp. 38-39). Regression equations developed from the data had low r-squared values, 

probably because data were not available for other 

important variables such as site-specific precipitation 

and runoff (pp. 39-40). Sediment flows originating 

from nongranitic fill materials were predicted to travel 

about 5 feet farther than those from granitic fill materials (p. 47). 

See Burroughs and King (1989) for additional 

information. 

Cook and King 1983, Horse Creek Study Area, Nez 

Perce National Forest-Sediment transport below fills 

was evaluated for 3 years after road construction. All 

fills were 1.5: 1 slopes, and were seeded, hydromulched, 

and fertilized. Some had slash filter windrows constructed at the toe of the fill. Windrows at five stream 

crossings were a total of 1,190 feet long (pp. 2-4). 

Only seven sediment flows were observed below the 

windrowed fills in the 3-year study period; three of 

these delivered sediment to the stream. Windrows 

usually breached as a result of slumping when snowmelt saturated the fill (p. 4). Average transport distance for sediment flows was 3.8 feet below windrows. 

For fills without windrows, the average transport 

distance was 41.4 feet for flows originating in slumps, 

and 24.2 feet for flows originating in areas of the fill 

that had not slumped (p. 4). 

Most ofthis informationis also presentedinTennyson 

and others (1981). First year results are presented in 

King (1979). See Burroughs and King (1989) for addiMegahan and others 1986, Silver Creek Study Area, 

Boise National Forest-A sediment budget was developed for material eroded from roads during construction. All measurements were made within a year of 

the completion of construction. About 85 percent ofthe 

eroded material was stored on slopes, 8 percent was 

stored in the stream channels, and 7 percent was 

delivered to the mouths of the watersheds (p. 38). 

The volume and transport distance of sediment 

flows below the road werecmeasured. Sediment flows 

associated with berm drains or cross drains (relief 

culverts) had greater volumes and travel distances 

than those originating on fillslopes. For sediment 

flows originating on fXlslopes, the average flow traveled 

6 meters; the longest traveled 64 meters, with 94 

percent traveling less than 15 meters. The average 

sediment flow originating from drainage structures 

traveled 32 meters, the longest traveled 118 meters, 

with 39 percent transported less than 15 meters. 

Volumes of sediment flows averaged 0.3 cubic meters 

for flows from fills compared to 4.7 cubic meters from 

drainage structures (pp. 35-36). 

See KetchesonandMegahan(l990), Megahan(1991), 

and Burton (n.d.) for additional information. 

Burroughs and King 1989, Horse Creek Study Area 

and Gospel Hump management areas, Nez Perce National Forest-For most midslope forest roads, only 

fillslopes close to stream channels are likely to deliver 

sediment to the streams. However, predicting sediment flow distance is difficult due to the numerous 

interacting variables (p. 8). 

Most of the results are in the summaries above for 

King (1979), Tennyson and others (1981), Carlton and 

others (1982), and Cook and King (1983). 

Fillslope sediment flow travel distance data from 

one road were summarized for 2 years after construction at Horse Creek (p. 9). They showed the influence 

of slash filter windrows, travelway drainage, slumping, and culverts. For flows not influenced by any of 

these, the average transport distance was 25.8 feet 

and the maximum was 86 feet. Windrows reduced 

travel distances to an average of 3.8 feet with a 

maximum of 33 feet. The average travel distances 

were increased to 58.8 feet by travelway drainage 

(maximum 85 feet), to 72.8 feet by culvert flow (maximum 125 feet), and to 80.4 feet by slumping (maximum 106 feet). Figures showing cumulative frequency 

of travel distance can be used to plan buffer strips in 

areas similar to Horse Creek (gneiss and schist parent 

materials with 30 to 40 percent sideslope gradients) 

(pp. 10-11). 

The distance sediment flowed was not strongly correlated with road gradient, length of the road segment 

draining into the culvert, or sideslope gradient for 

Horse Creek sediment flows related to relief culverts. - tional information. - 
Over half of the sediment flows below relief culverts 

were transported more than 75 feet (p. 10). 

A plot of sediment transport distance at Gospel 

Hump showed that travelway drainage increased average distances, while greater densities of obstructions reduced them (p. 9). 

See King(1979), Tennysonandothers (1981), Carlton 

and others (1982), and Cook and King (1983) for 

additional information. 

Ketcheson and Megahan 1990, Silver Creek Study 

Area, Boise National Forest-Volumes and lengths of 

sediment flows below roads were measured for 4 years 

after road construction. Statistics are given (p. 3) for 

length and volume by source (fills with and without 

cull logs placed at toe, cross drains (relief culverts), 

berm drains, rock drains, and landings). Sediment 

flows from cross drains (relief culverts) had the greatest average volume (819.5 cubic feet) and length (248 

feet), and also contained 63 percent of the total sediment flow volume (pp. 3,5). Sediment flows from fills 

traveled an average of 20 feet (p. 3), with average 

volumes of around 24 cubic feet. Flows associated with 

berm drains averaged 66 feet long (205.1 cubic feet) 

and those associated with rock drains averaged 39 feet 

long (24.5 cubic feet). Differences in sediment flow 

volume and length among the sources were related 

to the sizes of the contributing source areas, including both the road prism and undisturbed watershed 

(PP. 3,5). 

Probability distributions were developed for sediment flow volume and length by source. Maximum 

travel distances were less than 200 feet for all sources 

except cross drains, for which the maximums ranged 

to 900 feet. Sediment flows from cross drains have a 

0.15 probability of traveling farther than 300 feet. 

Volume distributions were similar to those for distance. The probability distributions can be used to 

plan buffer strip widths based on road drainage structures (pp. 9, 10, 12-16). 

Sediment flow volumes decrease rapidly within the 

first 75 feet of travel. Gradient and obstructions iduence sediment volume distribution for those portions 

of flows more than 75 feet below roads (pp. 5, 7, 8). 

Obstructions can deflect or stop sediment flow if they 

are large, in good contact with the ground, and 

oriented perpendicular to the slope. Small stems are 

generally ineffective in this regard (p. 11). 

See Megahan and others (1986), Megahan (1991), 

and Burton (ad.) for additional information. 

Megahan 1991, Silver Creek Study Area, Boise National Forest-For sediment flows originating from 

roams, more than 95 percent ofthe total volume was 

within 20 meters of the toe of the fill 4 years after 

construction (p. 146). 

See Megahan and others (1986), Ketcheson and 

Megahan (1990), Burton (n.d) for additional information. 

Burton, n.d., Silver Creek Study Area, Boise National Forest. Unpublished data attributed to 

Megahan-Sediment storage behind obstructions was 

strongly correlated with lengths of sediment flow 

(p. 2). An equation relating sediment flow travel distance to sideslope gradient, source area, total length of 

obstructions, and total volume of onsite sediment was 

derived (p. 3). 

See Megahan and others (1986), Ketcheson and 

Megahan (1990), Megahan (1991). See also the General Erosion Research Summary. 

BMP 89--Rule 4.b.ii. Plan to minimize road width 

to that which will safely accommodate the anticipated 

use. 

See Rule 4.b. (BMP 85), references marked "width." 

BMP 90-Rule 4.b.ii. Minimize cut volumes by 

designing the road alignment to fit the natural terrain 

features as closely as possible. 

See Rule 4.b. (BMP 85), references marked "cut." 

BMP 91-Rule 4.b.ii. Minimize fill volumes by designing the road alignment to fit the natural terrain 

features as closely as possible. 

See Rule 4.b. (BMP 85), references marked "fill." 

BMP 92--Rule 4.b.ii. Use as much of the excavated 

material as practical in fill sections. 

Clayton and Arnold 1972, Idaho Batholith-Areas 

of the most highly weathered granitic rock class 

(class 7) are prone to landslides. The authors suggest 

that stability would be enhanced by borrowing fill 

from areas with other rock-weathering classes (p. 16). 

BMP 93--Rule 4.b.ii. Plan minimum cuts, particularly near stream channels. 

See Rule 4.b. (BMP 85), references marked "cut," and 

Rule 4.b.i., road buffer strips (BMP's 86 through 88). 

BMP 94-Rule 4.b.ii. Plan minimum fills, particularly near stream channels. 

See Rule 4.b. (BMP 85), references markedUfill," and 

Rule 4.b.i., road buffer strip rules (BMP's 86 through 

88). 

BMP 95-Rule 4.b.iii. Design embankments so that 

excavated material may be disposed of on geologically 

stable sites. 

No specific references were found. See the General 

Erosion Research Summary for references regarding 

geologically stable sites. 

BMP 9ORule 4.b.iii. Design waste so that excavated material may be disposed of on geologically 

stable sites. 

No specific references were found. See the General 

Erosion Research Summary for references regarding 

geologically stable sites. 
BMP 97-Rule 4.b.i~. Plan roads to drain naturally 

by: outsloping (first alternative). 

BMP 98-Rule 4.b.i~. Plan roads to drain naturally 

by: insloping (second alternative). 

These two BMP's will be reviewed together. 

Haupt and others 1963, Zena Creek Logging Study 

Area, Payette National Forest-Following three longduration, low-intensity storms ofunprecedented total 

rainfall (pp. 4-51, the authors visually evaluated erosion on insloped and outsloped sections of a newly 

constructed loggingroad. Both insloped and outsloped 

sections had earthen cross drains spaced 30 to 90 feet 

apart (p. 2). Shoulders and fills had been seeded and 

mulched with chopped hay and asphalt binder (p. 3). 

Insloped sections had less erosion damage than 

outsloped sections. The outsloped sections had severe 

erosion of the roadbed, decreasing the usable width, 

while damage on the insloped sections was slight (pp. 

6-7). The worst damage on outsloped sections occurred 

at the mouths of swales on incurves (p. 6). All earthen 

cross drain outlets were deeply eroded on the outsloped 

portions (p. 6). Cross drains also generated fill erosion 

on insloped sections (p. 7). Fill erosion, although widespread on both insloped and outsloped sections, was 

more severe on outsloped sections, especially on 

incurves (pp. 6-7). No cases were observed where 

sloughing on insloped sections interfered with inside 

drainage; this was attributed to the shallow soils on 

the roadcuts (p. 7) 

Based on their observations, the authors recommended insloping, leading as much runoff as possible 

away from the long fill on the incurve (p. 8). They also 

recommended that if earthen cross drains are to be 

used, they should drain on the outcurve (p. 8). 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-Based on field and laboratory investigations of slope failures, the authors recommended insloping all fill sections and providing 

outside berms, unless adequate fillslope erosion control measures can be provided. Benched sections could 

be outsloped if natural vegetation or erosion control 

measures are adequate to prevent erosion (p. 33). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest--An engineering research team evaluated a road designed to 

minimize watershed impacts, during the construction 

period and the early period of use. The road had been 

designed as an outsloped road, but did not function 

that way because trenches had been left by tractors 

and skidded logs, and because berms had been left 

along the edge of the road during grading (p. 13). The 

authors felt that outsloping would seldom function as 

designed due to runoff concentrated by wheels and 

slight differences in soil properties. They recommended 

outsloping only where surfaces are "relatively nonerodible," such as full-bench sections (p. 20). 

They further noted that insloping can result in 

considerable sediment movement unless cutslopes and 

ditches are stabilized. They suggestedthatroads should 

be designed to carry water along the tread, and that 

provisions should be made to filter or settle out sediment before road runoff reaches streams (p. 21). 

Burroughs and King 1989, Horse Creek Study Area, 

Nez Perce National Forest-The authors recommended 

insloping to the ditch or providing for uniform distribution of outslope drainage. Outsloped sections would 

require care during road maintenance to avoid creating berms and to maintain uniform drainage (p. 16). 

BMP 99--Rule 4.b.i~. Plan roads to drain naturally 

by grade changes where possible. 

No references were found. 

BMP 100-Rule 4.b.i~. Plan dips on roads when 

necessary. 

BMP 101Dule 4.b.i~. Plan water bars on roads 

when necessary. 

BMP 102-Rule 4.b.i~. Plan cross drainage on roads 

when necessary. 

These three BMP's are considered together here. 

Haupt 1959a,b, Little Owl Creek watershed of the 

Boise River Basin-Haupt (1959b) looked at various 

road design and site factors as predictors of sediment 

flow distance below logging roads that had been "put 

to bed" (standard loggingroad closure techniques that 

include cross ditching and removal of temporary culverts) (pp. 329-330). Multiple regression analysis 

showed that the "slope obstruction index" was the 

variable most highly related to transport distance, 

followed by cross ditch interval squared, embankment 

slope length, and the product of cross ditch interval 

and road gradient (pp. 330-331). The regression equation can predict necessary buffer strip widths under 

various conditions (p. 332). 

Haupt (1959a) used the regression equation to develop tables for road design, construction, and abandonment. Various tables can be used to estimate the 

buffer strip widths, cross ditch interval, or slope obstruction index necessary to minimize sediment delivery to streams under a wide range of road and site 

characteristics (pp. 9-20). 

Haupt and others 1963, Zena Creek Logging Study 

Area, Payette National Forest-Following three longduration, low-intensity storms of unprecedented total 

rainfall (pp. 4-5), the authors visually evaluated erosion on insloped and outsloped road sections of a newly 

constructedloggingroad. Both insloped and outsloped 

sections had earthen cross drains spaced 30 to 90 feet 
apart (p. 2). Shoulders and fills had been seeded and 

mulched with chopped hay and asphalt binder (p. 3). 

All earthen cross drain outlets were deeply eroded 

on the outsloped portions (p. 6). Cross drains also 

generated fill erosion on insloped sections; Cross drain 

outlets were the only site where surface drainage had 

overtopped the road on inslopes (p. 7). The authors 

recommended that if earthen cross drains are to be 

used, they should drain on the outcurve (D. 8). 

Packer and Christensen 1964,720 sites in Idaho and 

Montana-This publication is a field guide for controlling logging road sediment, primarily through the 

control of cross drain spacing and buffer strip widths. 

It is based on the research reported in Packer (1967) 

and field experience. 

Logging road surfaces deteriorate rapidly when rill 

erosion exceeds 1 inch in depth. A table (pp. 13-15) 

gives cross drain spacing required to prevent 83 percent of cases of rill erosion deeper than 1 inch by road 

grade and soil group, with adjustment factors for slope 

position, exposure, sidehill slope gradient, and increased erosion prevention (97 percent). 

Another table (p. 16) gives buffer strip widths (measured from the road centerline) required to prevent 

sediment delivery in 83 percent of cases, based on 

obstruction spacing and obstruction type. Adjustment 

factors are provided to allow for soil group, cross drain 

spacing, distance to first obstruction, fillslope cover 

density, and 97 percent prevention of sediment delivery (pp. 15-17). 

Guides are provided for estimating some of the 

variables (pp. 17-22), and for installing devices to 

control erosion and sediment flow, including some 

cross drainage structures (pp. 33-40). 

See Packer (1967) for additional information. 

Haupt and Kidd 1965, Boise Basin Experimental 

Forest, Boise National Forest-The authors evaluated 

efforts to minimize erosion associated with logging 

and logging road construction. "Good logging practices" included seeding, harrowing, and cross draining 

ofroads following loggingin 1953 and 1954 (p. 665). By 

1958, the perennial grasses that had been seeded on 

the roadways were well established and erosion was 

negligible during the most intense storm (2.82 inches 

per hour for 10 minutes) of the 7-year study period 

(p. 668). 

Packer 1967,720 sites in Idaho and Montana, representing six major soil groups-Twenty-four watershed 

and road characteristics were tested as predictors of: 

(1) cross drain spacing needed to prevent road surface 

rills deeper than 1 inch, and (2) the distance of sediment movement downslope. Cross drainage structures included dips, cross ditches, and open-top culverts; these were not evaluated separately. For the 

analysis of cross drain spacing, significant variables, 

in their order of importance, were road surface stability, road surface grade, topographic position, aspect, 

and upper slope steepness (pp. 6-7). The regression 

equation (p. 6) was used to develop a table (p. 11) that 

gives cross drain spacings by road grade and soil type 

with adjustments for topographic position, aspect, 

slope steepness, and the percent of cases in which 1-inch 

rills are prevented. This is the same as the table (p. 14) 

in Packer and Christensen (1964). 

Cross drain spacing was one of the significant variables in the prediction of sediment transport distance. 

A table (pp. 16-17) was developed using the regression 

equation (p. 12) to define buffer strip width given 

obstruction spacing and obstruction types with adjustments for soil type, cross drain spacing, distance to 

+tial obstruction, fillslope cover density, the percent 

of erosion prevention, and so forth. (See the road buffer 

strip rule, Rule 4.b.i., BMP's 86 through 88). The 

authors suggest increasing buffer strip width by 1 foot 

for each 10-foot increase in cross drain spacing beyond 

30 feet (p. 16). This is essentially the same table as in 

Packer and Christensen (1964, pp. 15-17), except that 

distances are measured from the road shoulder rather 

than from the road centerline. 

See Packer and Christensen (1964) for additional 

information. 

Megahan and Kidd1972a,b, Zena Creek Study Area, 

Payette National Forest-The authors studied erosion 

and sedimentation from logging and road construction. Roads built in October 1961 were seeded and 

water barred after logging was completed in November 1962. The average sedimentation rate in ephemeral drainages below roads for 4.8 years after logging 

was 51.0 tons per square mile per day. No data were 

collected for comparison on roads that were not seeded 

or water barred. Sedimentationrates onnearby undisturbed watersheds averaged 0.07 tons per square mile 

per day. A return to predisturbance levels was not 

expected due to continued roadcut and tread erosion. 

Gray and Megahan 1981, Pine Creek Study Area, 

Middle Fork of the Payette River drainage, Boise National Forest-Analyses evaluated the contributions 

of forest vegetation to slope stability through various 

mechanisms. The authors recommended that road 

cross drainage structures should drain onto undisturbed vegetation (p. 21). 

BMP 103-Rule 4.b.v. Plan relief culverts and roadside ditches whenever reliance upon natural drainage 

would not protect the running surface, excavation, or 

embankment. 

Megahan and others 1979, Clearwater National 

Forest and Middle Fork of the Payette River drainage, 

Boise National Forest-In a survey of mass erosion, 66 

percent ofroad-associated slides originated onroadcuts, 

27 percent originated on roadfills without culverts, 
and 7 percent originated on fills with culverts. Fortyseven percent of the erosion volume originated on 

roadcuts, 31 percent originated on fills without culverts, and 21 percent originated on fills with culverts. 

However, just 33 percent of the slide material delivered to streams originated on roadcuts, 51 percent 

originated on fills without culverts, and 16 percent 

originated on fills with culverts (p. 131). 

Gray and Megahan 1981, Pine Creek Study Area, 

Middle Fork of the Payette River drainage, Boise National Forest-Analyses evaluated the contributions 

of forest vegetation to slope stability through various 

mechanisms. The authors recommended leaving areas of undisturbed vegetation, water spreading areas, 

large enough to accommodate road drainage (p. 21). 

Tennyson and others 1981, Horse Creek, Nez Perce 

National Forest-Ditch elevation was measured following road construction. During snowmelt periods, 

ditches generally degraded; the distance between culverts and the road gradient was significantly and 

positively correlated with degradation (pp. 55, 70). 

During the first snowmelt period, ditches on roads 

with gradients of 6 to 9 percent degraded an average 

of 0.122 feet (p. 55). During summer, aggradation 

(filling) was more common; aggradation was significantly and positively correlated with cutslope height 

(p. 70). In general, deposition was observed in the first 

100 feet of the ditch; erosion increasedwith increasing 

distance (pp. 57-58). 

Burroughs and others 1983b, Rainy Day Road, Nez 

Perce National b ore st-~ests with simulated rainfall 

compared the sediment yield from the ditch plus the 

untreated cutslope for rocked and unrocked ditches. 

The ratio of sediment yields (p. 14) was: 

(unrocked ditch + .untreated cutslope) : 

(rocked ditch + untreated cutslope) = 2.29 

Clayton 1983, Silver Creek Study Area, Boise National Forest-Results from preconstrudion seismic 

and resistivity surveys were used to accurately predict 

the necessary drainage design and to plan underdrain 

installation on a new collector road (p. 5). 

Megahan and others 1986, Silver Creek Study Area, 

Boise National Forest-A sediment budget was developed for material eroded from roads during construction. In the fall of the year of construction, about 85 

percent of the eroded material was stored on slopes 

(p. 38). 

The authors measured the volume and transport 

distance of sediment flows below the road. Sediment 

flows associated with berm drains or cross drains 

(relief culverts) had greater volumes and travel distances than those originating on fillslopes. For sediment flows originating on fillslopes, the average travel 

distance was 6 meters, the maximum was 64 meters; 

94 percent were transported less than 15 meters. For 

sediment flows originating from drainage structures, 

average travel distance was 32 meters, the maximum 

was 118 meters; 39 percent were transportedless than 

15 meters. Volumes of sediment flows averaged 0.3 

cubic meters for flows from fills compared to 4.7 cubic 

meters for flows from drainage structures (pp. 35-36). 

See Ketcheson and Megahan (1990) for a followup 

report. 

Burroughs and King 1989, Horse Creek Study Area 

and Rainy Day Road, Nez Perce National Forest-Rill 

volumes and sediment flow transport distances were 

measured in the Horse Creek Study Area for 2 years 

after road construction. One of the longest average 

transport distances (72.8 feet) for sediment flows below road fillslopes resulted when rills were formed 

below relief culvert outflows or when sediment flows 

from rills combined with relief culvert flow paths 

(pp. 8-91. 

Transport distances below relief culverts were not 

strongly correlated with the length of road contributing to the culvert, the road gradient, or the sideslope 

gradient (p. 10). A figure (p. 10) shows the cumulative 

frequency of sediment travel distances for flows influenced by relief culverts; this might apply to similar 

sites with gneiss and schist parent material and 

sideslope gradients of 30-40 percent (p. 11). 

Procedures for designing roadside ditch riprap for 

forest roads are given (pp. 13-14). Experiments with 

simulated rainfall on the Rainy Day Road indicate 

that degradation of an unprotected ditch might produce more sediment than erosion from an unprotected 

road tread on roads with low volumes of traffic (p. 14). 

See Tennyson and others (1981), and Burroughs and 

others (198313) for additional information. 

Ketcheson and Megahan 1990, Silver Creek Study 

Area, Boise National Forest-The authors measured 

volumes and lengths of sediment flows below roads for 

4 years after road construction. Statistics give length 

and volume by source: fills with and without cull logs 

placedat toe, cross drains (relief culverts), berm drains, 

rock drains, and landings (p. 3). Sediment flows from 

cross drains (relief culverts) had the greatest average 

volume (819.5 cubic feet) and length (248 feet); they 

contained 63 percent ofthe total sediment flow volume 

(pp. 3, 5). The mean length of flows associated with 

berm drains was 66 feet (mean volume 205.1 cubic 

feet) compared to a mean length of 39 feet for rock 

drains (meanvolume 24.5 cubic feet). Differences were 

related to the sizes of the contributing source areas, 

including both road prism andundisturbed watershed 

areas (pp. 3,5). 

Probability distributions were developed for sediment flow volume and length by source. Maximum 

travel distances were less than 200 feet for all sources 
except cross drains (relief culverts), for which the 

maximum ranged to 900 feet. For cross drains, the 

probability of travel distances exceeding 300 feet is 

0.15. Volume distributions were similar to those for 

distance. The probability distributions can be used to 

plan the width of buffer strips based on road drainage 

structures (pp. 9, 10,12-16). 

See Megahan and others (1986) for additional 

information. 

For general information on road drainage see the 

General Erosion Research Summary, especially 

Gonsior and Gardner (19711, Burroughs and others 

(19721, Clayton and Arnold (1972), Megahan (1972), 

Clayton (1983), Megahan (1983), and Vincent (1985). 

BMP 104--Rule 4.b.v. Design culvert installations 

to prevent erosion of the fill. 

Bachmann 1958, Silver and Crystal Creeks, near 

Pierce-This study used a paired-watershed approach 

(p. 9) to investigate the effects of logging and logging 

road construction on selected physical, chemical, and 

biological features of northern Idaho trout streams 

(pp. 2-3). Measured predisturbance (1955 and 1956) 

turbidities ranged from 0.25 to 2.10 parts per million 

in Silver Creek, and from 0.6 to 6.9 parts per millionin 

Crystal Creek (p. 34). 

In the Crystal Creek drainage, which had road 

construction activity in 1956 and 1957, a vegetated 

buffer strip (width unspecified) was left between the 

road and stream, except at stream crossings. Roadfills 

at stream crossings were not treated (pp. 21-22). 

Temporarily increased turbidity (90 parts per million) 

and a sediment deposit were associated with culvert 

installation (pp. 22, 35, 37). Increases in turbidity 

were noted only during rain, snowmelt, and direct 

channel disturbances; sediment sources were predominantly at stream crossings (pp. 35,37). Although 

turbidity sampling was not adequate to define average 

or maximum values (p. 37), turbidity was different 

above and below road crossings, and also between the 

roaded and unroaded watersheds (p. 35). 

Haupt and Others 1963, Zena Creek Logging Study 

Area, Payette National Forest-Following three longduration, low-intensity storms of unprecedented total 

rainfall (pp. 4-51, erosion was visually compared on 

insloped and outsloped road sections of a newly constructed logging road. Both insloped and outsloped 

sections had earthen cross drains spaced 30 to 90 feet 

apart (p. 2). Shoulders and fills had been seeded and . 

mulched with chopped hay and asphalt binder (p. 3). 

Insloped sections had less erosion damage than 

outsloped sections. The worst damage on outsloped 

sections occurred at the mouths of swales on incurves 

(p. 6). The authors recommended that culverts placed 

in major ravines be laid on the original grade so they 

drain into the original channel rather than on the fill 

of the incurve (p. 8). 

Gonsior and Gardner 1971-When investigating 

slope failures in the Idaho Batholith, the authors 

measured low soil permeablilities. Permeability can 

be expected to decrease over time in roadfills and 

elsewhere; this must be considered in the design of 

culverts (p. 12). The authors stressed the need to 

evaluate surface and subsurface flow conditions when 

locating and designing roads (p. 33). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-During the 

construction period and the early period of use, an 

engineering research team evaluated a road designed 

to minimize watershed impacts. The authors recom- 

&ended that dimpled connecting bands not be used on 

culverts because sections sometimes leak or separate. 

They also recommended skewing culverts or using 

downspouts to avoid steep culvert gradients that result in scour (p. 10). Proper bedding of culverts and 

compaction of backfill material are discussed (p. 12). 

Burroughs and King 1989, Horse Creek Study Area 

and Rainy Day Road, Nez Perce National Forest-Rill 

volumes and sediment flow transport distances were 

measured for 2 years after road construction in the 

Horse Creek Study Area. One of the longest average 

transport distances (72.8 feet) for sediment flows below road fillslopes resulted when rills formed below 

relief culvert outflows or when sediment flows from 

rills combined with the paths of flows from relief 

culverts (pp. 8-9). Transport distances below relief 

culverts were not strongly correlated with the length 

of road contributing water to the culvert, the road 

gradient, or the sideslope gradient (p. 10). A figure 

(p. 10) shows the cumulative frequency of sediment 

travel distances for flows influenced by relief culverts; 

this might apply to similar sites with gneiss and schist 

parent material and sideslope gradients of 30 to 40 

percent (p. 11). 

BMP 106-Rule 4.b.v. Plan drainage structures to 

achieve minimum direct discharge of sediment into 

streams. 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-During the 

construction period and the early period of use, an 

engineering research team evaluated a road designed 

to minimize watershed impacts. The authors stressed 

the need for careful planning to control sediment from 

the cutslope and ditch. They recommended routing 

water down the road surface rather than along the toe 

of the cutslope. They also recommended providing for 

sediment filtering or settling before runoff leaves the 

road surface, or discharging drainage far enough from 

streams to provide for infiltration and clarification 

(p. 21). 
BMP 106--Rule 4.b.vi. Plan stream crossings to be 

minimum in number. 

Bachmann 1958, Silver and Crystal Creeks, near 

Pierce-This study used a paired-watershed approach 

(p. 9) to investigate the effects of logging and logging 

road construction on selected physical, chemical, and 

biological features of northern Idaho trout streams 

(pp. 2-31. Measured predisturbance (1955 and 1956) 

turbidities ranged from 0.25 to 2.10 parts per million 

in Silver Creek, and from 0.6 to 6.9 parts per million in 

Crystal Creek (p. 34). 

In the Crystal Creek drainage, which had road 

construction activity in 1956 and 1957, a vegetated 

buffer strip (width unspecified) was left between the 

road and stream, except at stream crossings. Roadfills 

were not treated at stream crossings (pp. 21-22). 

Temporarily increased turbidity (90 parts per million) 

and a sediment deposit were associated with culvert 

installation (pp. 22, 35, 37). Increases in sedimentation and turbidity were noted at crossings of some 

small tributaries (p. 25). However, most of the material that eroded from the road prism was not delivered 

to the stream due to the distance between the road and 

the stream (p. 25). Increases in turbidity were noted 

only during rain, snowmelt, and direct channel disturbances; sediment sources were predominantly at 

stream crossings (pp. 35,37). Although turbidity sampling was inadequate to define average or maximum 

values (p. 37), turbidity was different above and below 

road crossings, and also between the roaded and 

unroaded watersheds (p. 35). 

King and Gonsiorl980, Horse Creek Study Area, Nez 

Perce National Forest-Limited sediment sampling at 

monitoring stations above culvert inlets ("A stations"), 

below culvert outlets ("B stations"), and 100 yards 

downstream YC stations") provided indications of the 

first-year effects (1978-1979) of road construction at 

stream crossings (p. 3, 7). 

At one crossing, pioneering operations provided an 

estimated 12.3 pounds of excess sediment at the C 

station (p. 9) compared to 0.2 pounds for permanent 

culvert installation. The low value for permanent 

culvert installation was attributed to "dewatering," or 

routing the streamflow around the construction site 

during installation. At another crossing, which was 

not dewatered, 46 pounds of sediment passed the C 

station during permanent culvert installation (p. 9). 

Shortly after construction, sediment concentrations 

at the crossings returned to preconstruction levels 

except during rainstorms, during which the sediment 

loads increased by about 100 to 1,000 times over the 

normal load at the B stations (p. 11). During the first 

snowmelt period following construction, the road contributed 400 pounds of sediment at one stream crossing, based on measurements at the monitoring stations (p. ll). The following summer (1 year after 

construction), sediment loads during storms were up 

to 10 times greater than normal (p. 15). 

See King (1981) for a more complete report. 

King 1981, Horse Creek Study Area, Nez Perce National Forest-Sediment sampling at monitoring stations above culvert inlets ("A stations"), below culvert 

outlets ("B stations"), and 100 yards downstream ("C 

stations") was used to evaluate the effects of road 

construction activities at stream crossings. Summaries are given of some of these measurements for road 

pioneering activities in 1978 and 1979 (p. 62). Sediment due to pioneering and temporary culvert placement varied from 0.00 to 212.59 pounds, averaging 

40.65 pounds, when measured at C stations. These 

values do not necessarily represent total sediment produced; in some cases flows may have been inadequate to 

provide transportto the C stations (pp. 61,63). Delivery 

ratios from the B to C stations varied from 14.4 to 72.5 

percent for three stream crossings tested (p. 64). The 

mean peak sediment concentration measured at 10 C 

stations during pioneering activities was 2,256 milligrams per liter (p. 63). Clearing of right-of-way slash 

at one crossing contributed 1.56 pounds of sediment at 

the C station; the peak concentration was 88.1 milligrams per liter (p. 63). Sediment concentrations upstream from the activities were generally less than 5 

milligrams per liter (p. 63). 

Sediment measurements during permanent culvert 

installation in 1978 and 1979 are also summarized 

(p. 67). For eight culvert installations, the sediment 

measured at the C stations varied from 0.22 to 603.75 

pounds, averaging 82.96 pounds (p. 66). Concurrent 

measurements were available at the B stations in 

some cases. It appears that C station values were 

strongly influenced by the lack of sediment transport 

in some cases, and by channel scour in others (p. 66). 

Peak sediment concentrations measured at the C 

stations during 10 permanent culvert installations 

varied from 5.3 to 39,243 milligrams per liter, averaging 5,924.8 milligrams per liter (p. 70). 

See Rule 4.b.i., minimum roadconstructionin streamside protection zones and road buffer stip rules (BMP's 

86 through 88). 

BMP 107-Rule 4.b.vi. Plan all culvert installation 

on Class I streams to provide for fish passage. 

No references were found. 

BMP 108-Rule 4.b.vii. Consider reuse of existing 

roads when reuse or reconstruction would result in the 

least long-run impact on site productivity, water quality, and fish and wildlife habitat. 

Megahan 1974b, four sites in the Idaho Batholith: 

Deep Creek, Silver Creek, Bogus Basin, Deadwood 

River-Data on roadfill erosion or total road prism 

erosion were used to develop a negative exponential 

equation showing surface erosion on severely disturbed 
granitic soils over time. By far the greatest percentage 

of erosion occurs in the first and second years after 

construction (p. 12). In the first year, erosion rates are 

three orders of magnitude (about 1,000 times) greater 

than on undisturbed lands, where rates average 0.07 

tons per square mile per day (p. 12). Additional disturbances result in new cycles of surface erosion (p. 13). 

No references were found specific to reuse compared 

to new road construction; however, numerous references show decreases over time (ranging from the first 

season to the first 3 years) in total road erosion or 

erosion on various components of the road prism. 

Megahan (197413) has the largest data set and the 

longest records. Because he dealt most directly with 

the concept of erosion time trends, his research was 

summarized here. 

Rule 4.c. Road Construction 

Forty BMP's (109 through 148) were evaluated. 

These addressed several topics associated with road 

construction: 

Placement of excess material from road construction (BMP's 109 through 113,115, and 116); 

Surface stabilization ,of material exposed during 

the construction process (BMP's 117 through 122); 

Fillslope stability (BMP's 123 through 127); 

Windrows (BMP's 128 and 129); 

Road construction in or near streams (BMP's 130 

through 132); 

Maintenance of outsloped roads (BMP's 133 and 

134); 

Quarry drainage (BMP 135); 

Prevention of fill erosion due to drainage structures (BMP's 136 through 142); 

Drainage on uncompleted roads (BMP's 143 and 

144); 

Minimum grade of relief culverts (BMP 145); 

Earthwork during wet periods (BMP 146); 

Hazards from overhanging banks and trees (BMP's 

147 and 148). 

Placement of Excess Material 

No references were found on the placement of road 

construction debris, overburden, and other materials. 

The reader is referred to the General Erosion Research Summary for information on the "stable location" requirement of these BMP's. One study addressed clearing drainage ways of debris generated 

during construction. King(1981, p. 63) obseved shortterm increases in sediment during clearing of right-ofway slash at a stream crossing; he concluded that 

normal slash clearing operations would have minimal 

effects on stream sedimentation. 

Stabilization of Exposed Material 

Several studies evaluated various means of stabilizing cut and fillslopes. Most of the research has been 

done on fillslopes, and most looked at combinations of 

treatments listed in the BMP's rather than individual 

treatments (for example, seeding, mulching and netting compared to a control, instead of comparing seeding to a control, mulching to a control, and netting to 

a control). 

An early fillslope study in the Idaho Batholith 

(Ohlander 1964, p. 19) compared a seed and fertilizer 

control treatment to the use of seed and fertilizer 

coupled with five other treatments. These were surface holes, chipped slash, straw and asphalt binder, 

and one or three layers of paper netting. The one layer 

of paper netting and the asphalt binder and straw 

treatments were the most effective in terms of both 

sediment reduction and vegetation production (p. 29). 

Another fillslope study in the Idaho Batholith 

(Bethlahmy and Kidd 1966, p. 4) compared anunseeded 

control with various treatments. In general, combinations of seed, fertilizer, mulch, and netting were the 

most effective. 

Megahan (1974a, p. 14) found that mulch and netting used in conjunction with seeding or planting 

significantly reduced fillslope surface erosion in the 

Idaho Batholith. Planted trees (without mulch) also 

reduced surface erosion (pp. 13-14) and had better 

survival rates than seeded trees or seeded grass (p. 8). 

Trees were also expected to reduce mass erosion hazards (p. 3). Fertilizer increased tree growth (p. 11). He 

recommended that planted trees, fertilizer, mulch, 

and netting be used to attain maximum erosion control (p. 15). 

In the Silver Creek Study Area, 16 fillslope treatments were tested (Megahan and others 1992, p. 59). 

As a group, treatments combining revegetation and 

surface amendments were more effective in controlling erosion than either revegetation or surface amendments alone (p. 63). The most effective individual 

treatment combined straw, crimping, seed, fertilizer, 

and transplants (p. 59). Acompanion study on cutslopes 

in the study area (Boise State University, Department 

of Geology and Geophysics 1984, p. 20) found that dry 

seeding, hydroseeding, and hydroseeding plus terracing all significantly reduced cutslope erosion. 

Several references reported on studies of cutslope 

and fillslope erosion control in northern Idaho. King 

(1984, p. 2) summarized results from the Horse Creek 

Study Area. Three treatments (plus a control) on cut 

and fillslopes were evaluated for 3 years after road 

construction. The treatments included: straw mulch 

with asphalt tackifier, seed, and fertilizer; cellulose 

fiber hydromulch, seed, and fertilizer; dry seeding; 

and no treatment. On cutslopes, straw mulch reduced 
erosion by 32 to 47 percent, the only treatment that 

significantly reduced erosion. All of the treatments 

were comparable in reducing fillslope erosion. Relative to the control, the treatments reduced erosion 24 

to 30 percent for fills from 20 to 40 feet high, and from 

46 to 58 percent for fills less than 20 feet high. 

Also in the Horse Creek Study Area, Burroughs and 

King (1985, p. 186) applied simulated rainfall to fillslopes to evaluate the relative erosion control of an 

established dense stand of grass and wood excelsior 

mulch with nylon netting over loose soil, compared 

with loose soil. The grass treatment reduced sediment 

by 99.5 percent and the mulch treatment reduced 

erosion by 91 percent compared with the bare, loose 

soil (p. 189). They concluded that mulch could provide 

immediate protection, while a dense stand of grass 

provided effective long-term protection (p. 189). 

The importance of fill compaction in the Idaho 

Batholith was addressed in several reports. Lack of fill 

compaction was identified by Gonsior and Gardner 

(1971, p. 31) as an important factor contributing to 

failures, through liquefaction under saturated conditions, and through reduced resistance to shear under 

all conditions. Similarly, Hartsog and Gonsior (1973, 

pp. 6-7) noted that lack of fill compaction was partially 

responsible for sloughing, settlement cracks, and liquefaction during heavy rainstorms. Clayton and Arnold 

(1972) recommended compaction of fillslopes constructed in weathering class 7 rock (the most highly 

weathered) to reduce the chance of mass failure (p. 16). 

Also in the Idaho Batholith, Megahan and others 

(1992, pp. 57-58) evaluated fillslope erosion control of 

six construction techniques. Three methods of embankment placement were tested: side cast, layer 

placed, and controlled compaction. The three methods 

did not differ significantly with respect to surface 

erosion; however, controlled compaction was recommended to reduce mass erosion on high hazard sites 

(pp. 61-62). Surface rolling with a grid roller, intended 

to compact the surface of the fill, significantly increased surface erosion rates for all of the embankment placement methods. On average, erosion increased from 9.2 (no rolling) to 28.9 (with rolling) 

metric tons per hectare per year (p. 61). 

Burroughs and King (1989, p. 2) noted that factors 

influencing the effectiveness of fillslope treatments 

include: timing, type, and rate of application of treatments, as well as insloping or outsloping of the road 

surface, soil erodibility, and slope gradient. Many of 

the same variables influence cutslope erosion control, 

although erosion processes may be different on steep 

cutslopes (p. 11). Aspect, elevation, soil type, and frost 

heaving may be important (p. 12). Ditch maintenance 

may reinitiate cutslope erosion processes by undercutting the slope (pp. 12-13). 

No references were found regarding riprap for stabilization of exposed material. 

Fillslope Stability 

No references were found regarding the incorporation of snow, ice, and frozen soil into roadfills. Based on 

their analyses of slope failures in the Idaho Batholith, 

Gonsior and Gardner (1971, pp. 31-33) stressed that 

logs, stumps, large roots, and debris should always be 

removed from fill material. For research on the effects 

of compaction on fill stability, see BMP 118, stabilization of exposed material by compacting, and the General Erosion Research Summary. 

Windrows 

Only a few studies actually measured the effectiveness of windrows. One in the Horse Creek Study Area 

was reported most completely by Cook andKing(1983). 

Windrow construction at five stream crossings totaled 

1,190 feet in length (pp. 2-4). Comparisons (between 

windrowed and nonwindrowed fill sections) of sediment in collection troughs below the fills indicated 

that 99 percent of eroded fill material was retained 

within the windrows (p. 3). Average sediment volumes 

in troughs below windrows was 0.325 cubic feet per 

100 feet of road for fill lengths of 0 to 10 feet and 0.650 

cubic feet per 100 feet of road for fill lengths of 10 to 

20 feet. Corresponding values for nonwindrowed fills 

were 35.85 cubic feet per 100 feet ofroad for fill lengths 

of 0 to 10 feet and 64.30 cubic feet per 100 feet of road 

for fill lengths of 10 to 20 feet (pp. 3-4). Surveys of rills 

and gullies in the fills provided another means of 

estimatingwindrow performance. Basedon these data 

it was estimated that windrows retained 75 to 85 

percent of the eroded material (p. 4). 

Only seven sediment flows were observed below the 

windrowed fills in the 3-year study period; three of 

these had sediment delivery to the stream. When 

windrows were breached, it was usually because of 

slumping associated with snowmelt saturation of the 

fill (p. 4). Average transport distance for sediment 

flows was 3.8 feet below windrows. For nonwindrowed 

fills, the average transport distance was 41.4 feet for 

flows originating in slumps, and 24.2 feet for flows 

originating in unslumped areas of the fill (p. 4). 

Another study in the Horse Creek Study Area 

(Burroughs and King 1985, pp. 186-187) compared 

fillslope sediment generated by simulated rainfall for 

a loose soil control and a loose soil with filter windrow 

treatment. The windrow treatment reduced sediment 

by 87 percent compared with the control (p. 189). This 

study indicated that windrows could provide effective 

protection immediately following construction; other 

observations in the study area confirped that windrows were still effective 7 years after construction 

(p. 190). 

Researchin the Silver Creek Study Area (Ketcheson 

and Megahan 1990) showed no significant differences 
in sediment flow volume or length between fills with 

and without cull logs placed at the toe (p. 3). However, 

field observations elsewhere in the Idaho Batholith 

have confumed the effectiveness ofwindrows (Hartsog 

and Gonsior 1973, p. 5). 

Several other reports present data that have implications for windrows. As indicated in the sections on 

buEer strips, several studies (Haupt 1959a,b; Packer 

and Christensen 1964; Packer 1967; Burroughs and 

King 1989; Ketcheson and Megahan 1990; Burton 

n.d.) have shown the importance of slope obstructions 

in limiting sediment movement. See summaries of 

these references under the buffer,striprules (BMP's 86 

through 88) or the windrow rules (BMP's 128 and 129). 

Road Construction In or Near Streams 

See Rule 4.b.i., minimum road constructionin stream 

protection zones and road buffer strip rules (BMP's 86 

through 88) and Rule 4.b.vi., minimum stream crossings (BMP 106). 

Maintenance of Outsloped Roads 

Two reports noted the difticulties in maintaining 

outsloped roads. Hartsog and Gonsior (1973, p. 13) 

observed ruts from logging activities that redirected 

the flow of water on an outsloped road. They felt that 

concentrations of water would occur on almost any 

outsloped road under normal tr6c conditions (p. 20). 

They also observed that a berm left by a grading 

operation concentrated water that eventually drained 

onto the fillslope, and was a major source of erosion 

during a heavy rainstorm (p. 13). 

Burroughs and King (1989, p. 16) observed a similar 

situation where an unintentionally constructed berm 

concentrated flow that resulted in high fillslope erosionrates. They recommendedinsloping to the ditch or 

providing uniform distribution of outslope drainage. 

Road maintenance employees would need to be careful 

to avoid creating berms and to maintain uniform 

drainage on outsloped portions of the road. 

See BMP's 97 and 98 for more information on 

insloping and outsloping. 

Quarry Drainage 

Qnly one study was found that addressed quarries. 

Bachmann (1958) measured turbidities near a quarry 

site as part of a study of the effects of logging and road 

construction on various stream characteristics. Rock 

was quarried in the Crystal Creek watershed during 

road construction activities (p. 22). The quarry was 

adjacent to a small tributary, and was a major source 

of sediment (p. 30). Sediment deposits nearly covered 

the channel below the quarry. Turbidities measured 

at the sampling station near the quarry were among 

the highest in the study (p. 30). For example, values of 

350 parts per million of sediment were measured 

during snowmelt; after a 12-hour rain, 2,169 parts per 

million of sediment were measured (p. 36). Pre-disturbance turbidities ranged from 0.6 to 6.9 parts per 

million in Crystal Creek (p. 34). 

Preventing Fill Erosion Due to Drainage Structures 

Most of the reports summarized under these BMP's 

presented qualitative observations or recommendations rather than quantitative data. For example, 

Haupt and others (1963) observed storm damages 

associatedwith cross drains on insloped and outsloped 

road sections. All earthen cross drain outlets were 

deeply eroded on the outsloped portions (p. 6). Cross 

drains also generated fill erosion on insloped sections. 

Cross drain outlets were the only site where surface 

drainage overtopped the inslope (p. 7). Based on their 

obsemations, the authors recommended that if earthen 

cross drains are to be used, they should drain on the 

outcurve (p. 8). 

During the construction period and the early period 

of use, Hartsog and Gonsior (1973) evaluated a road 

designed to minimize watershedimpads. The authors 

recommended that dimpled connecting bands not be 

used on culverts, to prevent sections from separating 

or leaking. They also recommended skewing culverts 

or using downspouts to avoid steep culvert gradients 

that result in scour (p. 10). Proper bedding of culverts 

and compaction of backfill material were discussed (p. 

12). Gonsior and Gardner (1971) stressed the need to 

evaluate surface and subsdce flow conditions when 

locating and designing roads (p. 33). 

Research in the Horse Creek Study Area evaluated 

the influence of relief culverts on sediment flow transport distances for 2 years after road construction 

(Burroughs and King 1989). One of the longest average transport distances (72.8 feet) for sediment flows 

below road fillslopes resulted when rills formed below 

relief culvert outflows or when sediment flows from 

rills combined with relief culvert flows (pp. 8-9). Transport distances below relief culverts were not strongly 

correlated with the length of road contributing to the 

culvert, the road gradient, or the sideslope gradient 

(p. 10). A cumulative frequency distribution of sediment travel distances for flows influenced by relief 

culverts was developed (p. 10). 

No references were found regarding the use of riprap 

or vegetative matter to minimize erosion of the fill 

associated withdrainage structures. For relatedreferences, see Rule 4.c.iii., stabilization of exposed material by seeding (BMP 117), mulching (BMP 121), and 

other suitable means (BMP 122), and the General 

Erosion Research Summary. Also, no references were 

found that directly addressed time trends in fill 
erosion due to outflow from drainage structures. However, numerous studies show time trends in erosion 

that illustrate the need for timely application bf erosion control measures; some of these are listed under 

BMP 138. 

Drainage on Uncompleted Roads 

No references were found that dealt directly with 

erosion due to lack of drainage structures on uncompleted roads during spring and fall runoff. However, 

many references have implications for this rule. Several cross-references are listed under BMP's 143 and 

144. 

In the South Fork Salmon River drainage, Hartsog 

and Gonsior (1973) evaluated the construction and 

initial performance stages of a road designed to minimize environmental impacts. The road was designed 

as an outsloped road, but did not function as such 

because skidded logs and skidding tractors rutted the 

road surface (p. 13). During a heavy 4-day rainstorm 

on Labor Day weekend, this road had considerable 

erosion, that was largely attributed to incomplete 

shaping and grading (p. 19). A half-mile length of 

pioneer road had no erosion, even though it had no 

drainage structures installed. This was attributed to 

minimal disturbance of natural drainage patterns, 

flat grade or short stretches of unbroken grade, and 

loose, absorbent soil conditions (p. 15). Based on these 

observations, the authors suggested constructing a 

minimum standard contour road with a rolling grade 

and installing drainage structures during logging operations. Each road section could be completed to the 

desired standard when log hauling was finished on 

that section (p. 19). 

Based on observations in the Silver Creek Study 

Area, Megahan and others (1986) noted that construction phase erosion often depended more on the stage of 

road construction during rainstorms than on the final 

design features of the road. They recommended that 

temporary berms be constructed to protect fills when 

storm threats are high (p. 39). 

Minimum Grade of Relief Culverts 

No references were found relating to this BMP. 

Earthwork During Wet Periods 

Two studies with simulated rainfall showed that 

sediment yields from rutted road sections were greater 

than those from unrutted sections. In northern Idaho, 

Burroughs and others (1983b, p. 16) measured a 108 

percent increase in sediment associated with ruts. 

They noted that surface armoring might not occur if 

traffic is present (p. 22). In eastern Idaho, Foltz and 

Burroughs (1990, pp. 273-274) found that a rutted 

road could produce from 1.0 to 2.1 times as much 

sediment as an unrutted road, depending on the moisture conditions. They recommended road closures to 

prevent rutting during wet weather (p. 275). 

In the Silver Creek Study Area, Megahan and others 

(1991) tested several site factors as predictors of fillslope erosion during snow-free periods. Only ground 

cover density and rainfall erosivity (an index based on 

rainfall intensity) were statistically significant (p. 56). 

Hazards from Overhanging Banks and Trees 

No references were found on the hazards of overhanging banks. Several references stressed the contributions of trees to slope stability, and many recommendedleavingtrees above and below roads whenever 

the hazards are not too great. 

For example, Gonsior and Gardner (1971, pp. 31-32) 

felt live trees were important sources of slope stability 

by mechanically reinforcing the soil and depleting soil 

moisture (and possibly slowing subsurface weathering by moderating temperatures). Burroughs and 

Thomas (1977, p. 16) evaluated the tensile strength of 

Douglas-fir roots, and found them to be an important 

factor increasing slope stability. Root tensile strength 

decreases rapidly in the first year after tree felling, 

and continues to decrease gradually over time. 

Megahan and others (1979, p. 133) found that landslides were most common 4 to 10 years after logging; 

landslide frequencies remained elevated for 20 years 

after logging. These time trends were attributed to the 

increasing loss of root strength through decay, interacting with growth of new roots over time to again 

stabilize the slope (p. 132). The slope stability analyses 

of Gray and Megahan (1981, p. 20) showed that many 

sites in the Idaho Batholith are in a state of marginal 

equilibrium, and may fail when roads are constructed 

or trees are harvested. They recommended leaving 

buffer zones of trees above and below haul roads, 

although they noted that the stability benefits must be 

weighed against the safety hazards (p. 21). 

Two references documented the role of tree roots in 

slowing erosion originating on cutslopes in the Silver 

Creek Study Area. Megahan and others (1983, p. 27) 

evaluated long-term (45-year) cutslope erosion rates. 

Reductions in soil erosion due to tree roots were 

observed in the field and were also apparent from the 

data. Megahan and Bohn (1989, p. 509) monitored a 

progressive mass failure originating on a cutslope; 

they noted that mass erosion hazards of this type are 

increased if timber is harvested above the roadcut. 

Also, tree roots were observed to slow uphill progress 

of failure and to retain soil that would otherwise 

collapse (pp. 504, 506). 
Research Results by Best Management 

Practice 

BMP 10SRule 4.c. Place debris associated with 

road construction in such a manner as to prevent entry 

into streams. 

No references were found. 

BMP 110-Rule 4.c. Place overburden associated 

with road construction in such a manner as to prevent 

entry into streams. 

No references were found. 

BMP Ill-Rule 4.c. Place other materials associated with road construction in such a manner as to 

prevent entry into streams. 

No references were found. 

BMP 112-Rule 4.c. Deposit excess material on 

stable locations ,outside the stream protection zones. 

No references were found; see the General Erosion 

Research Summary for references regarding stable 

locations. 

BMP 113-Rule 4.c. Deposit slash on stable locations outside the stream protection zones. 

No references were found. See the General Erosion 

Research Summary for references regarding stable 

locations. 

BMP IlARule 4.c.i. Construct roads in compliance with the planning guidelines of Rule 4.b. 

See summaries under individual BMP's in Rule 4.b. 

BMP 116-Rule 4.c.ii. Clear drainage ways of all 

debris generated during construction that potentially 

interferes with drainage or water quality. 

King 1981, Horse Creek Study Area, Nez Perce National Forest-Sediment sampling at monitoring stations above culvert inlets ("A stations"), below culvert 

outlets ("B stations"), and 100 yards downstream ("C 

stations") was used to evaluate the effects of road 

construction activities at stream crossings. Clearing 

right-of-way slash at one crossing contributed 1.56 

pounds of sediment at the C station; the peak concentration of sediment during the operation was 88.1 

milligrams per liter (p. 63). Sediment concentrations 

upstream from pioneering activities were generally 

less than 5 milligrams per liter (p. 63). Based on these 

measurements and visual observations at other crossings, the author concluded that normal slash clearing 

operations have minimal effects on stream sedimentation (p. 63). 

See Rule 3.f.i., removal of slash during harvesting 

operations (BMP 51). 

BMP 116-Rule 4.c.ii. Clear drainage ways of all 

debris generated during maintenance that potentially 

interferes with drainage or water quality. 

No references were found. 

BMP 117-Rule 4.c.iii. Where exposed material 

(excavation, embankment, borrow pits, waste piles, 

and so forth) is potentially erodible, and where sediments would enter streams, stabilize prior to fall or 

spring runoff by: seeding (first alternative). 

Ohlander 1964, Zena Creek Study Area, Payette 

National Forest--Sediment and vegetation were measured on fillslope erosion plots on south aspect slopes 

in the year following road construction. All plots except the control were seeded and fertilized; six treatments were tested: chipped slash, one layer paper 

netting, three layers paper netting, asphalt binder 

and straw, surface holes, and control (p. 19). The treatment using one layer of paper netting had the highest 

vegetation production, with asphalt binder and straw 

second (p. 31). (These two treatments also had the 

lowest sediment production; see the mulch rule, BMP 

121, and the other suitable means rule, BMP 122.) 

Average vegetation production measured in the fall 

was 20 pounds per acre for the control, 2,039 pounds 

per acre for the one layer paper netting treatment, and 

1,599 pounds per acre for the asphalt binder and straw 

treatment. All treatments significantly increased vegetation production as compared to the control; the 

lowest value of production was 900 pounds per acre for 

the chipped slash plots (p. 29). 

Bethlahmy and Kidd 1966, Bogus Basin Road, Boise 

National Forest-Eight f3lslope treatments were tested 

in plot studies, including various combinations of 

contour furrows, seed, fertilizer, holes, straw mulch, 

polymer emulsion, paper netting, jute netting, chicken 

wire netting, and straw mulch with asphalt emulsion 

(p. 2). All plots except the control were seeded and 

fertilized. The plots were on the fillslope of a newly 

constructed road. The fillslope had a gradient of 80 

percent and a southeast aspect. Six measurements 

were made over 11 months. 

Treatments were placed in three general groups: 

seed and fertilizer (Group A); seed, fertilizer, and 

mulch (Group B); seed, fertilizer, mulch, and netting 

(Group C). In Group A, one plot had contour furrows, 

seed, fertilizer, and holes; the other plot had polymer 

emulsion, seed, and fertilizer (p. 2). Both treatments 

had greater cumulative erosion than the control, with 

an average increase of 15 percent. Groups B and C 

both reduced erosion compared to the control (p. 4). 

See the mulch rule, BMP 121, and the other suitable 

means rule, BMP 122. 

Jensen and Finn 1966, Zena Creek Study Area, 

Payette National Forest-Watershed conditions were 

evaluated throughout the Zena Creek Study Area. The 

authors noted that most previous road stabilization 

attempts on decomposed granitic soils, including grass 

seeding, were unsuccessful. Cutslope surfaces remained raw and unvegetated, and grass roots were 
inadequate to stabilize steep sandy fillslopes when 

moisture content was high. Complete stabilization of 

cuts and fills on decomposed granitic soils appeared 

infeasible for slopes exceeding 45 percent (p. 76). 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-Based on extensive field and 

laboratory analyses of slope failures, the authors recommended revegetating fill surfaces as soon as possible after construction (p. 33). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-Field investigations evaluated the construction and initial performance stages of a road designed to minimize environmental impacts. The authors stressed the need to 

accelerate revegetation of cuts and fills (p. 22). 

Megahan 1974a, Deadwood River Road, Boise National Forest-Fillslope plot studies evaluated surface 

erosion control, growth, and survival associated with 

ponderosa pine, grass, and surface amendments. The 

potential of ponderosa pine to reduce mass erosion was 

discussed and assumed, although it was not tested in 

this study (pp. 2-3,15). The roadfill was 11 years old 

when the plots were installed, and had been unsuccessfully seeded to grass at least twice before the study 

(p. 4). The fillslope had a southwest aspect, and a 

gradient of 70 to 75 percent (p. 4). Nine treatments 

plus a control (pp. 5-6) were evaluated for longer than 

3 years (p. 7). 

Survival data were reported for plantedtrees, seeded 

trees, and seeded grass by years (p. 8). Survival was 

poor for seeded grass and seeded trees, but excellent 

for planted trees. After 4 years, 5 percent of seeded 

tree's survived, compared to 97 percent of planted 

trees. Seeded grass decreased from 17.2 to 0.8 plants 

per square foot over the 4-year period. Grass vigor may 

have decreased due to a severe grasshopper infestation (p. 8). 

Erosion did not differ significantly among the various treatments that used mulch (p. 13), which included the seeded grass and the seeded trees, as well 

as some of the planted trees (p. 5). The erosion control 

was attributed to the mulch and erosion net rather 

than to the seeding (pp. 13-15). See the mulch rule, 

BMP 121, and the other suitable means rule, BMP 122. 

King 1979, Horse Creek Study Area, Nez Perce National Forest-Fillslope erosion on hydroseeded slopes 

was measured for 1 year after construction. Rill and 

gully erosion processes were dominant in the summer; 

slumping was important during spring snowmelt 

(p. 11). Erosion volumes estimated by measuring rills 

and gullies were 9.9 cubic feet per 100 feet of road 

(p. 11). Of the total, 7 cubic feet eroded per 100 feet of 

road length during summer thunderstorms the year of 

construction; 2.9 cubic feet eroded per 100 feet of road 

during spring snowmelt the following year (p. 4). 

Slump surveys conducted on selected road sections 

showed the volume of displaced material averaging 

4.36 cubic feet per 100 feet of road; however, not a11 of 

this material left the fill (p. 10). 

On two other roads, fillslopes were seeded and 

mulched (straw mulch with asphalt tackifier). These 

roads had average erosion volumes of 6.1 and 5.1 cubic 

feet per 100 feet of road as measured in the rill and 

gully survey. Slump volumes were 21.91 and 13.57 

cubic feet per 100 feet of road (p. 10). 

See other Horse Creek publications listed under this 

rule for followup reports. 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-The authors compared 

road segments that were similar except for slope 

treatments. Hydroseeded fills with no mulch showed 

45 percent less fillslope erosion (33.1 cubic feet per 100 

feet of road) than untreated controls (59.71 cubic feet 

per 100 feet of road) during the first summer. However, differences were not statistically significant 

(p. 15). Fillslope gradients were 1.5:l (p. 7). 

Class 1 cutslopes (0-10 feet high) that were 

hydroseeded and mulched (straw mulch with an asphalt tackifier) showed significantly less erosion (73 

percent reduction) than untreated cutslopes for the 

first year after construction. Cumulative erosion was 

15 cubic feet per 100 feet ofroad for untreated cutslopes, 

compared to just 4 cubic' feet per 100 feet of road for 

treated cutslopes (p. 21). 

Carlton and others 1982, Gospel Hump management 

areas, Nez Perce National Forest-Fillslope erosion on 

roads constructed in 1978 and 1979 was evaluated by 

two methods from the spring of 1980 through the fall 

of 1981. The rill survey method was considered more 

representative of actual erosion rates than the bordered trap method (pp. 31, 38). All fillslopes were 

fertilized, seeded, and hydromulched (p. 13). Cumulative erosion volumes were about 65 cubic feet per 100 

feet of road in the spring of 1980 and 85 cubic feet per 

100 feet of road in the fd of 1981 (p. 30). No data were 

collected on untreated cutslopes, so erosion reduction 

due to treatment cannot be assessed. 

Cook and King 1983, Horse Creek Study Area, Nez 

Perce National Forest-Erosion was evaluated for a 

3-year period after construction on 1.5:l road fillslopes 

that had been seeded, hydromulched, and fertilized. 

Average erosionvolume measuredin collection troughs 

below the fills was 35.85 cubic feet per 100 feet of road 

for Class 1 (0-10 feet long) fillslopes and 64.30 cubic 

feet per 100 feet of road for Class 2 (10-20 feet long) 

fillslopes (p. 3). No measurements were made on 

untreated fillslopes, so erosion reduction due to treatment cannot be evaluated. 
Boise State University, Department of Geology and 

Geophysics 1984, Silver Creek Study Area, Boise Nutional Forest-Collection troughs were used to evaluate erosion from cutslopes with gradients ranging 

from 0.95:l to 1.8:l for 3 years after road construction. 

All of the treated cutslopes (dry seed, hydroseed, 

hydroseed plus terrace) had much lower erosion than 

untreated cutslopes. Untreated cutslopes yielded an 

average of 15 times as much sediment as the dry 

seeded slopes. Sample sizes for the other treatments 

(hydroseed and hydroseed plus terrace) were much 

smaller and comparisons may be misleading (p. 20). 

For results of fillslope studies, see Megahan and 

others (1991) and Megahan and others (1992). 

King 1984, Horse Creek Study Area, Nez Perce Nutional Forest-Three treatments (plus a control) on 

cut and fillslopes were evaluated for 3 years after road 

construction. The treatments included: straw mulch 

with asphalt tackifier, seed, and fertilizer; cellulose 

fiber hydromulch, seed, and fertilizer; dry seeding; 

and no treatment. 

On cutslopes, only the straw mulch treatment significantly reduced erosion, by 32 to 47 percent (p. 2). 

AU of the treatments were comparable in reducing 

fillslope erosion. Relative to the control, the treatments reduced erosion by 24 to 30 percent for fills 20 

to 40 feet high, and by 46 to 58 percent for fills less than 

20 feet high (p. 2). 

See other Horse Creek reports in this rule for additional information. 

Burroughs and King 1985, Horse Creek Study Area, 

Nez Perce National Forest-Simulated rainfall was 

applied to 1.5:1(67 percent) fillslopes to evaluate the 

relative erosion control effectiveness of an established 

dense stand of grass and wood excelsior mulch with 

nylon netting over loose soil, compared to loose soil. 

The grass stand had 97 percent cover of grass, litter, 

and stones greater than 0.25 inches in diameter; 

species were primarily orchardgrass and smoothbrome. 

Four applications of simulated rainfall were made for 

each treatment (pp. 186-187). The grass treatment 

reduced sediment by 99.5 percent, and the mulch 

treatment reduced sediment by 91 percent, compared 

to the bare, loose soil (p. 189). Mulch can be used to 

provide immediate protection, while a dense stand of 

grass provides effective, long-term protection (p. 189). 

Burroughs and King 1989, literature review, various 

sites-The authors reviewed road erosion studies from 

Idaho and elsewhere. Only new Idaho data (not summarized elsewhere in this report), general observations, and recommendations will be included in, this 

summary. 

Erosion control treatments on one part of the road 

prism may influence sediment yield from other parts 

of the road prism (p. 1). Sediment contributions from 

the road prism components may vary over time. At one 

stream crossing in the Horse Creek Study Area, 80 

percent of the sediment measured the first year after 

construction entered from the fillslope side of the road; 

by the fourth year, 83 percent was entering by the 

ditch system. The road tread was unsurfaced and 

crowned; cuts and fills were not treated (pp. 15-16). 

Factors influencing the effectiveness offillslope treatments include: timing, type, and rate of application of 

treatments, as well as insloping or outsloping of the 

road surface, soil erodibility, and slope gradient (p. 2). 

Many of the same variables influence cutslope erosion 

control, although erosion processes may be different 

on steep cutslopes (p. 11). Aspect, elevation, soil type, 

and frost heaving may be of importance (p. 12). Ditch 

maintenance may initiate cutslope erosion processes 

by undercutting the slope (pp. 12-13). 

Based on observations on the Nez Perce National 

Forest, dry seeding is not recommended for 0.75:l 

cutslopes unless cutslope height is less than 6 to 8 feet. 

Sediment reductions for dry seeding are estimated at 

10 percent for 0.75:l cutslopes more than 8 feet high, 

and 36 percent for 1:l cutslopes, for the first year 

following construction (p. 11). 

After grass is established on cutslopes, it can reduce 

sediment an estimated 86 to 100 percent, depending 

on density of coverage (p. 12). 

Megahan and others 1992, Silver Creek Study Area, 

Boise National Forest-Erosion plots were used to 

evaluate the effectiveness of six construction techniques and 16 postconstruction treatments in controlling fillslope erosion for 3 years after road construction. Fills had design slopes of 1.5:l or 1.33:l. 

The steep slope seeder treatment (seed and fertilizer) decreased erosion by 52 percent (or 4.9 tons per 

acre per year) relative to the control. Other treatments 

combined seedingwithtransplants, mulches, and other 

techniques (see the mulch rule, BMP 121, and other 

suitable means rule, BMP 122). 

See the General Erosion Research Summary for 

additional information. 

BMP 118-Rule 4.c.iii. Where exposed material 

(excavation, embankment, borrow pits, waste piles, 

and so forth) is potentially erodible, and where 

sediments would enter streams, stabilize prior to fall 

or spring runoff by: compacting (second alternative). 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-The authors conducted extensive field and laboratory analyses of slope failures. 

Lack of fill compaction appeared to be an important 

factor contributing to failures, through liquefaction 

under saturated conditions, and through reduced resistance to shear under all conditions (p. 31). The 

authors recommended compaction of all fillslopes, 

with the degree of compaction depending on design 

standards and the properties of the fill material (p. 33). 
Clayton and Arnold 1972, Idaho Batholith-Based 

on their studies of the properties of granitic rock, the 

authors recommend compacting fillslopes constivcted 

in weathering class 7 rock, the most highly weathered 

classification. Landslides are common when roads are 

cut through class 7 rock (p. 16). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-Field investigations evaluated the construction and initial performance stages of a road designed to minimize environmental impacts. Lack of fill compaction was 

partially responsible for sloughing, settlement cracks, 

and also for liquefaction during a heavy rainstorm 

(pp. 6-71. 

Megahan and others 1992, Silver Creek Study Area, 

Boise National Forest-Erosion plots were used to 

evaluate the effectiveness of six construction techniques and 16 postconstruction treatments in controlling fillslope erosion for 3 years after road construction. Fills had design slopes of 1.5:l or 1.33:l. 

Three methods of embankment placement were 

tested: side cast, layer placed, and controlled compaction. There was no significant difference among the 

three methods with respect to surface erosion; however, controlled compaction was recommended to reduce mass erosion on high hazard sites. Surface rolling with a grid roller, intended to compact the surface 

of the fill, significantly increased surface erosion rates 

for all of the embankment placement methods. On 

average, erosion increased from 9.2 (no rolling) to 28.9 

(with rolling) metric tons per hectare per year. 

See the General Erosion Research Summary for 

additional information. 

BMP 119-Rule 4.c.iii. Where exposed material 

(excavation, embankment, borrow pits, waste piles, 

and so forth) is potentially erodible, and where sediments would enter streams, stabilize prior to fall or 

spring runoff by: riprapping (third alternative). 

No references were found; see the General Erosion 

Research Summary for information on the stabilizing 

effect of ground cover. 

BMP 120-Rule 4.c.iii. Where exposed material 

(excavation, embankment, borrow pits, waste piles, 

and so forth) is potentially erodible, and where sediments would enter streams, stabilize prior to fall or 

spring runoff by: benching (fourth alternative). 

Hartsog and Gonsior 1973, South Fork Salmon 

River Drainage, Payette National Forest-Field investigations evaluated the construction and initial performance stages of a road designed to minimize environmentalimpacts. The authors discussed the potential 

advantages and disadvantages of cutslope terraces. 

Some engineers believe that terraces improve regeneration; the authors believed that terracing increases 

erosion and sedimentation. The long-term effects of 

terracing on the study road's cutslopes were not yet 

apparent when the report was written (p. 10). 

Megahan and others 1983, Silver Creek Study Area, 

Boise National Forest-Long-term (45-year) cutslope 

erosion was positively correlated with original cutslope 

gradient (pp. 24,25). The authors recommended constructing cutslopes at lower gradients on gentle terrain and using terraced slopes on steeper terrain (p. 27). 

Boise State University, Department of Geology and 

Geophysics 1984, Silver Creek Study Area, Boise National Forest-Collection troughs were used to evaluate erosion from cutslopes with gradients ranging 

from 0.95:l to 1.8:l for 3 years after road construction. 

AU of the treated cutslopes (dry seed, hydroseed, 

hydroseed plus terrace) had much lower erosion than 

untreated cutslopes. However, sample sizes for the 

hydroseed plus terrace treatment were small (p. 20). 

For results of fillslope studies, see Megahan and 

others (1991), and Megahan and others (1992). 

Megahan 1988, Silver Creek Study Area, Boise NationalForest-Cutslope terracingreduced surface erosion by 86 percent (p. 344). 

See the General Erosion Research Summary for 

additional information. 

BMP 121-Rule 4.c.ii.i. Where exposed material 

(excavation, embankment, borrow pits, waste piles, 

and so forth) is potentially erodible, and where sediments would enter streams, stabilize prior to fall or 

spring runoff by: mulching (fifth alternative). 

Ohlander 1964, Zena Creek Study Area, Payette 

National Forest-Sediment and vegetation were measured on fillslope erosion plots on southerly slopes in 

the year following road construction. All plots except 

the control were seeded and fertilized; six treatments 

were tested: chipped slash, one layer paper netting, 

three layers paper netting, asphalt binder with straw, 

surface holes, and control (p. 19). 

The author divided the study into three stages. In 

the first stage, the surface treatments alone afforded 

slope protection. Sediment measurement in the spring 

following construction showed that the asphalt binder 

with straw treatment had the lowest sediment production (242 pounds per acre). Chipped slash had higher 

sediment yields (15,247 pounds per acre than the 

control, which yielded 12,463 pounds of sediment per 

acre (p. 29). 

In the second stage, during the summer, the surface 

treatments and the new vegetative growth both provided erosion protection. The fall sediment measurement showed asphalt binder with straw, yielding 

138 pounds of sediment per acre, was the second most 

effective treatment. The control plots averaged 3,346 

pounds per acre for the fall measurement. The chipped 
slash treatment substantially reduced erosion compared to the control during this stage, yielding 740 

pounds of sediment per acre (p. 29). 

The third stage was the vegetative stage, when 

vegetation provided the most erosion control. Measurements in the fall following construction showed the 

second highest vegetation production (1,599 pounds 

per acre) on the plots with asphalt binder with straw. 

The control produced only 20 pounds ofvegetation per 

acre. The chipped slash treatment produced 900 pounds 

of vegetation per acre (p. 29). 

Bethlahmy and Kidd 1966, Bogus Basin Road, Boise 

National Forest-Eight fillslope treatments (p. 2) were 

tested in plot studies including various combinations 

of contour furrows, seed, fertilizer, holes, straw mulch, 

polymer emulsion, paper netting, jutenetting, chicken 

wire netting, and straw mulch with asphalt emulsion. 

All plots except the control were seeded and fertilized. 

The plots were on the fillslope of a newly constructed 

road. The fillslope had a gradient of 80 percent and a 

southeast aspect. Six measurements were made over 

11 months. 

Treatments were placed in three general groups 

(p. 4): seed and fertilizer (Group A); seed, fertilizer, 

and mulch (Group B); seed, fertilizer, mulch, and 

netting (Group C). In Group B, one plot had contour 

furrows, seed, fertilizer, holes, and straw mulch; the 

other plot had straw mulch with polymer emulsion, 

seed, and fertilizer (p. 2). Both of these treatments had 

less cumulative erosion than the control, an average of 

72 percent less. This was less erosion than Group A, 

but more than Group C (see the seeding rule above and 

the other suitable means rule below). The addition of 

straw mulch in Group B reduced erosion by an average 

of 74 percent compared to similar treatments in Group 

A that did not include mulch (p. 4). 

Jensen and Finn 1966, Zena Creek Study Area, 

Payette National Forest-Watershed conditions were 

evaluated throughout the Zena Creek Study Area. The 

authors noted that most previous road stabilization 

attempts on decomposed granitic soils, including 

mulching, were unsuccessful. Complete stabilization 

of cuts and fills on decomposed granitic soils appeared 

infeasible for slopes exceeding 45 percent (p. 76). 

Megahan 1974~~ Deadwood River Road, Boise National Forest-Fillslope plot studies evaluated surface 

erosion control, growth, and survival associated with 

ponderosa pine, grass, and surface amendments. The 

potential of ponderosa pine to reduce mass erosion was 

discussed and assumed, although it was not tested in 

this study (pp. 2-3,15). The roadfill was 11 years old 

when the plots were installed, and had been unsuccessfully seeded to grass at least twice before the study 

tp. 4). The fillslope had a southwest aspect, and a 

gradient of 70 to 75 percent (p. 4). Nine treatments 

plus a control (pp. 5-6) were evaluated for longer than 

3 years (p. 7). 

Erosion did not dBer significantly among the various treatments that used straw mulch (p. 13), which 

included treatments of seeded grass, seeded trees with 

and without fertilizer, and planted trees at two spacings, with and without fertilizer. All of the mulches 

were used in conjunction with erosion net (p. 5). 

Erosion on the mulched plots averaged 95 percent less 

than that on the control plots over a 3-year period. 

Effectiveness decreased somewhat over time; erosion 

reductions (relative to the control) fell from 98 percent 

in the first year to 92 percent in the third year. Mulches 

also increased tree growth on some plots (p. 13). 

King 1979, Horse Creek Study Area, Nez Perce National Forest-Fillslope erosion was measured for 

1 year after construction on three roads. Rill and gully 

erosion were dominant in the summer; slumping was 

important during spring snowmelt (p. 11). 

On two roads, fillslopes were seeded and mulched 

(straw mulch with asphalt tackifier). These roads had 

average erosion volumes of 6.1 and 5.1 cubic feet per 

100 feet of road as measured in a survey of rills and 

gullies. Measured volumes displaced by slumping were 

21.91 and 13.57 cubic feet per 100 feet of road; however, not all of this material left the fill (p. 10). 

No data on untreated fills were included. However, 

comparisons are available for one road with 

hydroseeded but mulched fills. Erosion volumes 

estimated from measurements of rills and gullies were 

9.9 cubic feet per hundred feet of road (p. 11). Slump 

surveys showed the volume of displaced material averaged 4.36 cubic feet per 100 feet of road (p. 10). 

See other Horse Creek publications under this rule 

for followup reports. 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-Class 1 cutslopes (0 to 10 

feet high) that were hydroseeded and mulched (straw 

mulch with an asphalt tackifier) showed significantly 

less erosion (73 percent reduction) than untreated 

cutslopes for the first year after construction. Cumulative erosion was 15 cubic feet per 100 feet of road for 

untreated cutslopes, compared to just 4 cubic feet for 

treated cutslopes (p. 21). 

Carlton and others 1982, Gospel Hump management 

areas, Nez Perce National Forest-Fillslope erosion on 

roads constructed in 1978 and 1979 was evaluated by 

two methods from the spring of 1980 through the fall 

of 1981. The rill survey method was considered more 

representative of actual erosion rates than the bordered trap method (pp. 31, 38). All fillslopes were 

fertilized, seeded, and hydromulched (p. 13). Cumulative erosion volumes were about 65 cubic feet per100 

feet of road in the spring of 1980 and 85 cubic feet per 

100 feet of road in the fall of 1981 (p. 30). No data were 
collected on untreated fillslopes, so erosion reduction 

due to treatment cannot be assessed. 

Cook and King 1983, Horse Creek Study Are&, Nez 

Perce National Forest-Erosion was evaluated for a 

3-year period after construction on 1.5: 1 road fillslopes 

that had been seeded, hydromulched, and fertilized. 

Average erosion measured in collection troughs below 

the fills was 35.85 cubic feet per 100 feet of road for 

Class 1 fillslopes (0 to 10 feet long) and 64.30 cubic feet 

per 100 feet of road for Class 2 fillslopes (10 to 20 feet 

long) (p. 3). No measurements were made on untreated fillslopes, so erosion protection provided by the 

treatment cannot be evaluated. 

King 1984, Horse Creek Study Area, Nez Perce National Forest-Three treatments (plus a control) on 

cut and fillslopes were evaluated for 3 years after road 

construction. The treatments included: straw mulch 

with asphalt tackifier, seed, and fertilizer; cellulose 

fiber hydromulch, seed, and fertilizer; dry seeding; 

and no treatment. 

On cutslopes, only the straw mulch treatment significantly reduced erosion, by 32 to 47 percent (p. 2). 

All of the treatments were comparable in reducing 

fillslope erosion. Relative to the control, the treatments reduced erosion by 24 to 30 percent for fills 20 

to 40 feet high, and 46 to 58 percent for fills less than 

20 feet high (p. 2). 

See other Horse Creek reports under this rule for 

further information. 

Burroughs and King 1985, Horse Creek Study Area, 

Nez Perce National Forest-Simulated rainfall was 

applied to 1.5:1(67 percent) fillslopes to evaluate the 

rel'ative erosion control effectiveness of an established 

dense stand of grass and wood excelsior mulch with 

nylon netting over loose soil, compared to loose soil. 

The grass stand had 97 percent cover of grass, litter, 

and stones greater than 0.25 inches in diameter; 

species were primarily orchardgrass and smooth brome. 

Four applications of simulated rainfall were made for 

each treatment (pp. 186-187). The grass treatment 

reduced sediment by 99.5 percent, and the mulch 

treatment reduced sediment by 91 percent, compared 

to the bare loose soil (p. 189). Mulch can be used to 

provide immediate protection, while a dense stand of 

grass provides effective long-term protection (p. 189). 

Burroughs and King 1989, literature review, various 

sites-The authors review road erosion studies from 

Idaho and elsewhere. Only new Idaho data (not summarized elsewhere in this report), general observations, and recommendations will be included in this 

summary. 

Erosion control treatments on one part of the road 

prism may influence sediment yield from other parts 

of the road prism (p. 1). Sediment contributions from 

the road prism components may vary over time. At one 

stream crossing in the Horse Creek Study Area, 80 

percent of the sediment measured the first year after 

construction entered from the fillslope side of the road; 

by the fourth year, 83 percent was entering by the 

ditch system. The road tread was unsurfaced and 

crowned; cuts and fills were not treated (pp. 15-16). 

Factors iduencing the effectiveness offillslope treati 

ments include: timing, type, and rate of application of 

treatments, as well as insloping or outsloping of the 

road surface, soil erodibility, and slope gradient (p. 2). 

Many of the same variables influence cutslope erosion 

control, although erosion processes may be different 

on steep cutslopes (p. 11). Aspect, elevation, soil type, 

and frost heaving may be of importance (p. 12). Ditch 

maintenance may initiate cutslope erosion processes 

by undercutting the slope (pp. 12-13). 

Effectiveness of fillslope mulches can be reduced by 

frost heaving or ground ice (p. 2). Hydromulches often 

do not remain on steep fillslopes unless combined with 

a fiber tackifier (p. 2). Drainage from the road tread 

onto the fillslope can reduce the effectiveness of any 

mulch (p. 3). 

Wood chips and rock mulches cannot be used on 

cutslopes; hydromulch is ineffective on steep cutslopes 

(pp. 11,12). Sediment reductions for hydromulching 

are estimated at 10 percent on 0.75: 1 cutslopes, and 30 

percent for 1:l cutslopes or cutslopes that are not as 

steep (p. 12). Straw mulch is more effective if applied 

with a tackifier (p. 11). Estimated sediment reductions for straw mulch alone are 35 percent for 0.75:l 

slopes and 40 percent for 1:l slopes. For straw mulch 

with asphalt tackifier, the estimated sediment reductions are 40 percent for 0.75:l and 75 percent for 1:l 

slopes (p. 11). Frost heaving or ground ice can reduce 

effectiveness of cutslope mulch treatments (p. 11). 

Megahan and others 1992, (Silver Creek Study Area, 

Boise National Forest-Erosion plots were used to 

evaluate the effectiveness of six construction techniques and 16 postconstruction treatments in controlling fillslope erosion for 3 years following road construction. Fills had design slopes of 1.5:l or 1.33:l. 

The most effective treatment, reducing erosion by 95 

percent, was straw-crimp-seed-fertilizer-transplant. 

The straw-crimp-net treatment was the second most 

effective, reducing erosion by 93 percent. Other treatments with mulches that reduced erosion were: strawpolymer-seed-fertilizer-transplant (86 percent), 

straw-net-seed-fertilizer-transplant (83 percent), 

straw-net (79 percent), hydromulch-seed-fertilizertransplants (69 percent), and hydromulch-seed-fertilizer (71 percent). The straw-crimp, hydromulch, and 

straw-polymer treatments were not significantly different from the control. 

The 16 treatments were also dividedinto three groups 

that were tested for erosion control effectiveness: 

revegetation alone, surface amendments alone, and 
revegetation combined with surface amendments. 

Treatments in which revegetation and surface amendments were combined were the most effective, followed by revegetation alone, and surface amendments 

alone. 

See the seeding rule, BMP 117; the other suitable 

means rule, BMP 122. See also the General Erosion 

Research Summary. 

BMP 122-Rule 4.c.iii. Where exposed material 

(excavation, embankment, borrow pits, waste piles, 

and so forth) is potentially erodible, and where sediments would enter streams, stabilize prior to fall or 

spring runoff by: other suitablemeans(sixth alternative). 

Ohlander 1964, Zena Creek Study Area, Payette 

National Forest-Sediment and vegetation were measured on fillslope erosion plots on southerly slopes in 

the year following road construction. AU plots except 

the control were seeded and fertilized; six treatments 

were tested: chipped slash, one layer paper netting, 

three layers paper netting, asphalt binder with straw, 

surface holes, and control (p. 19). 

The author divided the study into three stages. In 

the first stage, the surface treatments alone afforded 

slope protection. Sediment measurement in the spring 

following construction showed that the surface hole 

treatment, yielding 11,978 pounds per acre, produced 

only slightly less sediment than the control, which 

yielded 12,463 pounds per acre. In this stage, onelayer 

of paper netting had reduced sediment yields (302 

pounds per acre); however, three layers of paper netting had higher sediment yields (17,908 pounds per 

acre) than the control (p. 29). 

In the second stage, during the summer, the surface 

treatments and the new vegetative growth both provided erosion protection. The fall measurement showed 

that the surface hole treatment (2,274 pounds per 

acre) reduced sediment yields compared to the control 

plots (3,346 pounds per acre). However, all other 

treatments were much more effective at this stage. 

The one layer of paper netting treatment produced 

just 128 pounds of sediment per acre. The three layers 

of paper netting treatment yielded 320 pounds per 

acre (p. 29). 

The third stage was the vegetative stage, when 

vegetation provided the most erosion control. Measurements in the fall following construction showed the 

surface hole treatment produced 1,264 pounds of vegetation per acre; the control produced just 20 pounds 

per acre. The highest vegetation production was on the 

plots with one layer of paper netting(2,039 pounds per 

acre); plots with three layers of paper netting produced 1,341 pounds of vegetation per acre (p. 29). 

Bethlahmy and Kidd 1966, Bogus Basin Road, Boise 

National Forest-Eight fillslope treatments (p. 2) were 

tested in plot studies including various combinations 

of contour furrows, seed, fertilizer, holes, straw mulch, 

polymer emdsion, paper netting, jute netting, chicken 

wire netting, and straw mulch with asphalt emulsion. 

All plots except the control were seeded and fertilized. 

The plots were on the fillslope of a newly constructed 

road. The fillslope had a gradient of 80 percent and a 

southeast aspect. Six measurements were made over 

11 months. 

Treatments were placed in three general groups: 

seed and fertilizer (Group A); seed, fertilizer, and 

mulch (Group B); seed, fertilizer, mulch, and netting 

(Group C). In Group C, one plot had seed, fertilizer, 

straw mulch, and paper netting; another plot had 

seed, fertilizer, straw mulch, and jute netting; and the 

last plot had seed, fertilizer, straw mulch, and chicken 

wire netting (p. 2). These treatments had much less 

ctumulative erosion than the control, an average of 99 

percent less. This was better than either group A or 

group B. See seeding and mulching rules as mentioned 

earlier. The addition of netting in Group C to the 

mulch treatments in Group B reduced average erosion 

by 98 percent. 

Jensen and Finn 1966, Zena Creek Study Area, 

Payette National Forest-Watershed conditions were 

evaluated throughout the Zena Creek Study Area. The 

authors noted that most previous road stabilization 

attempts on decomposed granitic soils, including wattling (staking bundles of woody plant material, oRen 

live shrub cuttings that will root, into contour trenches 

and backfilling with soil) and artificial structures, 

were unsuccessful. Complete stabilization of cuts and 

fills on decomposed granitic soils appeared infeasible 

for slopes exceeding 45 percent (p. 76). 

Megahan 1974a, Deadwood River Road, Boise National Forest-Fillslope plot studies evaluated surface 

erosion control, growth, and survival associated with 

ponderosa pine, grass, and surface amendments. The 

potential of ponderosa pine to reduce mass erosion was 

discussed and assumed, although it was not tested in 

this study (pp. 2-3,15). The roadfill was 11 years old 

when the plots were installed, and had been unsuccessfully seeded tograss at least twice before the study 

(p. 4). The fillslope had a southwest aspect, and a 

gradient of 70 to 75 percent (p. 4). Nine treatments 

plus a control (pp. 5-6) were evaluated for longer that 

3 years (p. 7). 

Survival was poor for seeded grass and seeded trees, 

but excellent for planted trees (p. 8). ARer 4 years, 

5 percent of seeded trees survived, compared to 97 

percent of planted trees. Seeded grass decreased .from 

17.2 to 0.8 plants per square foot over the four 4-year 

period. Grass vigor may have decreased due to a severe 

grasshopper infestation (p. 8). Growth of planted trees 

was significantly greater in the upper fourth of the 

200-foot-long fillslope (p. 11). 
There was no significant difTerence in erosion between the two spacings (1.5 by 1.5 feet, and 2.5 by 2.5 

feet) ofplanted, unmulched trees (p. 13). Plantefl trees 

without mulch significantly reduced erosion (compared to the control plots) each of the 3 years; average 

reductions were 44 percent (pp. 13-14). 

Erosion did not differ significantly among the various treatments with mulch (p. 13), which included 

treatments of seeded grass, seeded trees with and 

without fertilizer, and planted trees at two spacings 

with and without fertilizer. All of the mulches were 

used in conjunction with erosion net (p. 5). Erosion on 

the mulched plots averaged 95 percent less than that 

on the control plots over a 3-year period. Effectiveness 

decreased somewhat over time; erosion reductions 

(relative to the control) fell from 98 percent in the first 

year to 92 percent in the third year. Mulches also 

increased tree growth on some plots (p. 13). 

The author recommended that in areas where ponderosa pine is a climax or seral species, it should be 

planted on roadfills at 3- or 4-foot spacing, fertilized, 

and mulched for the maximum surface and mass 

erosion control benefits. Lodgepole pine was recommended for subalpine fir habitat types (pp. 15-16). 

See Megahan ( 1978) for another report on this study. 

Megahan 1978, Deadwood River Road, Boise NationalForest-Fillslope plot studies evaluated surface 

erosion processes on bare plots and unmulched plots 

planted with ponderosa pine seedlings (p. 351). The 

roadfill had a southwest aspect, and a gradient of 70 to 

75 percent; it was 11 years old when the plots were 

installed (p. 350). 

Three water years (October 1 through September 

30) of data were available to test seasonal differences 

(p. 351). Mean daily erosion was significantly greater 

during the summer-fall period than during the winterspring period when there was no snow cover (pp. 351- 

352). Planted trees caused statistically significant 

reductions (0.05 level) in erosion during the summerfall periods, but not during the winter-spring periods 

(p. 352). Within the summer-fall periods, plots with 

planted trees had significantly less (0.01 level) erosion 

than the control plots both during periods with rain 

and without rain (p. 353). Tree planting reduced estimated dry creep erosion (relative to the control) from 

1.9 to 1.2 metric tons per square kilometer per day 

during rainy periods, and from 2.6 to 1.4 metric tons 

per square kilometer per day during rainfree periods 

(p. 355). 

See Megahan (1974a) for other results of this study. 

King 1979, Horse Creek Study Area, Nez Perce National Forest-Fillslope erosion was measured for 

1 year following construction on three roads. Rill and 

gully erosion processes were dominant in the summer; 

slumping was important during spring snowmelt (p. 11). 

On two roads, fillslopes were seeded and mulched 

(straw mulch with asphalt tackifier). These had average volumes of 6.1 and 5.1 cubic feet per 100 feet of 

road as measured in a survey of rills and gullies. 

Measured volumes displaced by slumping were 21.91 

and 13.57 cubic feet per 100 feet of road; however, not 

all of this material left the fill (p. 10). 

No data on untreated fills were included. However, 

comparisons are available for one road with hydroseeded but unmulched fills. Erosion volumes estimated 

from measurements of rills and gullies were 9.9 cubic 

feet per 100 feet ofroad (p. 11). Slump surveys showed 

an average of 4.36 cubic feet was displaced per 100 feet 

of road (p. 10). 

See other Horse Creek publications listed under this 

rule for followu~ re~orts. * - 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-Class 1 cutslopes (0 to 10 

feet high) that were hydroseeded and mulched (straw 

mulch with an asphalt tackifier) showed significantly 

less erosion (73 percent reduction) than untreated 

cutslopes for the first year after construction. Cumulative erosion was 15 cubic feet per 100 feet ofroad for 

untreated cutslopes, compared to 4 cubic feet for treated 

cutslopes (p. 21). 

Carlton andothers 1982, Gospel Hump management 

areas, Nez Perce National Forest-Fillslope erosion on 

roads constructed in 1978 and 1979 was evaluated by 

two methods from the spring of 1980 through the fall 

of 1981. The rill survey method was considered more 

representative of actual erosion rates than the bordered trap method (pp. 31,38). All fillslopes were fertilized, seeded, and hydromulched (p. 13). Cumulative 

erosion volumes were about 65 cubic feet per 100 feet 

of road in the spring of 1980 and 85 cubic feet per 100 

feet of road in the fall of 1981 (p. 30). No data were 

collected on untreated fillslopes, so erosion reduction 

due to treatment cannot be assessed. 

Cook and King 1983, Horse Creek Study Area, Nez 

Perce National Forest-Erosion was evaluated for a 

3-year period after construction on 1.5:l road fillslopes 

that had been seeded, hydromulched, and fertilized. 

Average erosion measured in collection troughs below 

the fills was 35.85 and 64.30 cubic feet per 100 feet of 

road for Class 1 (0-10 feet long) and Class 2 (10-20 feet 

long) fillslopes, respectively (p. 3). No measurements 

were made on untreated fillslopes, so erosion protection provided by the treatment cannot be evaluated. 

Boise State University, Department of Geology and 

Geophysics 1984, Silver Creek Study Area, Boise National Forest-Collection troughs were used to evaluate erosion from cutslopes with gradients ranging 

from 0.95:1 to 1.8:l for 3 years after road construction. 

AU of the treated cutslopes (dry seed, hydroseed, 

hydroseed plus terrace) had much lower erosion rates 
than untreated slopes. However, sample size for the 

hydroseed plus terrace treatment was small (p, 20). 

For results of fillslope studies, see Megahan and 

others (1991) and Megahan and others (1992). 

King 1984, Horse Creek Study Area, Nez Perce National Forest-Three treatments (plus a control) on 

cut and fillslopes were evaluated for 3 years after road 

construction. The treatments included: straw mulch 

with asphalt tackifier, seed, and fertilizer; cellulose 

fiber hydromulch, seed, and fertilizer; and dry seeding. 

On cutslopes, only the straw mulch treatment significantly reduced erosion, by 32 to 47 percent (p. 2). 

All treatments were comparable in reducing fillslope 

erosion. Relative to the control, the treatments reduced erosion 24 to 30 percent for fills 20 to 40 feet 

high, and 46 to 58 percent for fills less than 20 feet high 

(P. 2). 

See other Horse Creek reports in this rule for additional information. 

Burroughs and King 1985, Horse Creek Study Area, 

Nez Perce National Forest-Simulated rainfall was 

applied to 1.5:l (67 percent) fillslopes to evaluate the 

relative erosion control effectiveness of an established 

dense stand of grass and wood excelsior mulch with 

nylon netting over loose soil, compared to loose soil. 

The grass stand had 97 percent cover of grass, litter, 

and stones greater than 0.25 inches in diameter; 

species were primarily orchardgrass andsmooth brome. 

Four applications of simulated rainfall were made for 

each treatment (pp. 186-187). 

The grass treatments reduced sediment by 99.5 

percent and the mulch treatment reduced sediment by 

91 percent, compared to bare loose soil (p. 189). Mulch 

can be used to provide immediate protection, while a 

dense stand of grass provides effective long-term protection (p. 189). 

Burroughs and King 1989, literature review, various 

sites-The authors reviewed road erosion studies from 

Idaho and elsewhere. Only new Idaho data (not summarized elsewhere in this report), general observations, and recommendations will be included in this 

summary. 

Erosion control treatments on one part of the road 

prism may influence sediment yield from other parts 

of the road prism (p. 1). Sediment contributions from 

the road prism components may vary over time. At one 

stream crossing in the Horse Creek Study Area, 80 

percent of the sediment measured the first year after 

construction entered from the fillslope side of the road; 

by the fourth year, 83 percent was entering by the 

ditch system. The road tread was unsurfaced and 

crowned; cuts and fills were not treated (pp. 15-16). 

Factors influencing the effectiveness of fillslope treatments include: timing, type, and rate of application of 

treatments, as well as insloping or outsloping of the 

road surface, soil erodibility, and slope gradient (p. 2). 

Many of the same variables influence cutslope erosion 

control, although erosion processes may be different 

on steep cutslopes (p. 11). Aspect, elevation, soil type, 

and frost heaving may be important (p. 12). Ditch 

maintenance may initiate cutslope erosion processes 

by undercutting the slope (pp. 12-13). 

Two types of erosion control nets (one plastic net, 

and one nylon-reinforced paper) were compared on 1: 1 

cutslopes with vertical heights of 8 to 12 feet in the Nez 

Perce National Forest. Two years of observations 

showed no displacement of the mats, and erosion 

reductions were estimated at 95 to 98 percent (p. 12). 

All mats and netting require uniform slopes to function properly (p. 12). Erosion reductions for excelsior 

matsis estimatedas 75 percent on 1:l cutslopes and 60 

pgrcent on 0.75:l cutslopes (p. 12). 

Megahan and others 1992, Silver Creek Study Area, 

Boise National Forest-Erosion plots were used to 

evaluate fillslope erosion control effectiveness of six 

construction techniques and 16 postco~~tn.ictiontreatments for 3 years afker road construction. Fills had 

design slopes of 1.59 or 1.33:l. 

Cost and effectiveness of the individual postconstruction treatments are given. The most effective 

treatment, reducing erosion by 95 percent, was strawcrimpseed-fertilizer-transplant. The straw-crimpnet 

treatment was the second most effective, reducing 

erosion by 93 percent. The effectiveness of selected 

fillslope treatments are summarized: 

Erosion redaction 

(percent change 

Fillslope treatment relative to control) 

Straw, crimp, seed, fertilizer, transplant 95 

Straw, crimp, net 93 

Straw, polymer, seed, fertilizer, transplant 86 

Straw, net, seed, fertilizer, transplant 83 

Steep slope seeder, transplant 81 

Hydromulch, seed, fertilizer 71 

~~&omulch, seed, fertilizer, transplants 69 

Sprig, transplant * 

Polymer, seed, fertilizer, transplant * 

sprig * 

Straw, crimp * 

Straw, polymer * 

Polymer ** 

*Not significantly different from the control. 

**Increased erosion 10 percent. 

The 16 treatments were also divided into three 

groups that were tested for erosion control effectiveness: revegetation alone, surface amendments alone, 

and revegetation combined with surface amendments. 

The group of treatments that combined revegetation 

with surface amendments was the most effective, 

followed by revegetation alone, and surface amendments 
alone. See the seeding rule (BMP 117), compacting 

rule (BMP 118) mulch rule (BMP 121). 

See the General Erosion Research Summary. 

BMP 123-Rule 4.c.i~. In the constructionofroadfills 

near streams, compact the material to reduce the 

entry of water, minimize erosion, and minimize the 

settling of fill material. 

See summaries of Gonsior and Gardner (1971), 

Clayton and Arnold (1972), Hartsog and Gonsior (1973), 

and Megahan and others (1992), under BMP 118, 

stabilization of exposed material by compacting. See 

the General Erosion Research Summary for additional information. 

BMP 12P-Rule 4.c.i~. Minimize the amount of 

snow buried in embankments. 

No references were found. 

BMP 125-Rule 4.c.i~. Minimize the amount of ice 

buried in embankments. 

No references were found. 

BMP 126-Rule 4.c.i~. Minimize the amount of 

frozen soil buried in embankments. 

No references were found. 

BMP 127-Rule 4.c.i~. Avoidincorporatinginto fills 

significant amounts of woody material. 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-Extensive field and laboratory analyses were conducted, and slope stability was 

analyzed to determine the principal causes of slope 

failures in the Zena Creek Study Area. Based on these 

studies, the authors stressed that logs, stumps, large 

roots, and debris should always be removed from fill 

material (pp. 31,32,33). 

BMP 128-Rule 4.c.i~. Slash may be windrowed 

along the toe of the fill, but must meet the requirements of Rule 4.d.iii. 

BMF 129-Rule 4.c.i~. Debris may be windrowed 

along the toe of the fill, but must meet the requirements of Rule 4.d.iii. 

Note: these two rules will be considered together 

since slash and debris are often incorporated into 

windrows, and since the terms may be used interchangeably in the literature. 

Haupt 1959a,b, Little Owl Creek watershed of the 

Boise River basin-Haupt (1959b) looked at various 

road design and site factors as predictors of the distance sediment flowed below logging roads that had 

been "put to bed" (standard logging road closure techniques that include cross dit- and removal of 

temporary culverts) (pp. 329-330). Multiple regression analysis showed that the "slope obstruction index" was the variable most highly related to transport 

distance, followed by cross ditch interval squared, 

embankment slope length, and the product of cross 

ditch interval and road gradient (pp. 330-331). The 

lower sideslope gradient was not significant, because 

ofthe confounding effect of slope obstructions (p. 331). 

The regression equation (p. 332) can be used to predict 

necessary buffer strip widths under various conditions. 

Haupt (1959a) used the regression equation to develop tables for use in road design, construction, and 

abandonment. Various tables can estimate the buffer 

strip widths, cross ditch interval, or slope obstruction 

index necessary to minimize sediment delivery to 

streams for a wide range of road and site charaderistics (pp. 9-20). 

Packer and Christensen 1964, based on research at 

720 sites in Idaho and Montana-This publication is a 

field guide for controlling logging road sediment, primarily through the control of cross drain spacing and 

buffer strip widths. It is based on the research reported in Packer (1967) and field experience. 

Slope obstructions vary in tkeir ability to retard 

sediment flow. The following were listed in order of 

decreasing effectiveness (pp. 7,9): 

(1) Depressions made by pushed-over or wind-thrown 

trees, or a wavy ground surface 

(2) Logs thicker than 4 inches 

(3) Rocks more than 4 inches wide at ground surface 

(4) Trees and stumps 

(5) Slash and brush 

(6) Grass, weeds, and shrubs. 

A table (pp. 15-17) gives buffer strip widths (measured from the road centerline) required to prevent 

sediment delivery in 83 percent of cases, based on 

obstruction spacing and obstruction type. Adjustment 

factors are provided to allow for soil group, cross drain 

spacing, distance to first obstruction, fillslope cover 

density, and 97 percent prevention. For each 5-foot 

increase in distance to the first obstruction, the buffer 

strip width increases 4 feet. 

Obstruction storage capacity tended to be exceeded 

by the fourth or fifth year after road construction. The 

authors suggested that buffer strips could be narrower 

if drainage is diverted toward other obstructions or if 

new obstructions are provided when the road is 3 years 

old (p. 11). 

See Packer (1967) for additional information. 

Packer 1967,720sites in Idaho and Montana, representing six major soil groups-Twenty-four watershed 

and road characteristics were tested as predictors of 

sediment movement downslope from logging roads. 

The significant variables, in their order ofimportance, 

were obstruction spacing, the interaction of obstruction type and spacing, undisturbed slope stability, 

cross drain spacing, initial obstruction distance, age of 

road, and fillslope cover density (pp. 12-13). The multiple regression equation (p. 12) is also represented in 

a table (pp. 16-17). This is essentially the same table 
as in Packer and Christensen (1964, pp. 15-17), except 

that distances are measured from the road shoulder 

rather than from the road centerline. 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-The authors conducted field 

and laboratory investigations of slope failures and soil 

properties. They recommended leaving riprap or debris at or near the toe of the fill to stop sediment 

movement (p. 33). 

Megahan and Kidd 1972a, Zena Creek Study Area, 

Payette National Forest-Field observations showed 

substantially lower sediment yields &om loggingroads 

on one of three study watersheds. The reduction was 

due to interception of sediment flows by a barrier of 

logs and debris (pp. 5-6). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-Field investigations evaluated the construction and initial performance of a road designed to minimize environmental impacts. Slash piled at the toe of the fills formed 

highly effective debris basins (p. 5). Most of the 165 

cubic yards of sediment eroded from fills during a 

heavy 4-day storm was trapped in the slash and debris 

at the toe ofthe fills. Maximum transport distance was 

300 feet (p. 18). The authors felt that the slash and 

debris piles were one of the best sediment control 

devices during the storm. They felt the piles should be 

used in the future unless the associated fire or insect 

hazard was too high (p. 20). They suggested that all 

fills should have sediment catchments, specifically 

slash and debris piles, if these are not esthetically 

unacceptable (pp. 21-22). 

King1979, Horse Creek Study Area, Nez Perce National Forest-King evaluated travel distances for 

sediment flows from rill and gully erosion of roadfills 

for 1 year following road construction. Filter windrows 

were very effective in limiting material available for 

transport (0.22 cubic feet of eroded material per 100 feet 

of road length passed through the windrows, pp. 9-10). 

See other Horse Creek reports listedunder this rule 

for additional information. 

King and Gonsior 1980, Horse Creek Study Area, 

Nez Perce National Forest-In one subdrainage, 550 

feet of fillslopes (out of 731 feet) had filter windrows 

consisting of logging slash and debris, with cull logs 

keyed into the toe of the slope (p. 15). During the first 

summer, fall, and spring after construction, the windrows were 100 percent effective in retaining material 

eroded from the fillslope. Summer and fall fill erosion 

for the subdrainage was 25,000 to 40,000 pounds; 

spring fill erosion was 1,600 pounds. During the next 

summer-fall period, fill erosion in the subdrainage 

totalled 7,000 pounds. One windrow breach occurred, 

but no sediment reached the stream. The authors 

concluded that windrows were highly effective during 

the first year and a half (the period evaluated for this 

publication, p. 17). 

Observations of roads constructed elsewhere during 

the same year supported this conclusion. Total windrow length was 1,220 feet. Bothvolumes and transport 

distances of sediment were reduced considerably below windrowed fills. Transport distances were 10 to 

100 times greater below fills that were not windrowed 

(p. 17). 

See other Horse Creek reports listed under this rule 

for additional information. 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-The authors compared 

erosion on sections of fillslopes that were windrowed 

oy were not windrowed on one road for 2 years after 

construction. Differences were large, but not statistically significant. Sediment yields were 13.8 times 

greater on fills that were not windrowed for fillslopes 

0 to 10 feet long and 70.2 times greater for fillslopes 10 

to 20 feet long (pp. 15, 18). 

Travel distances for sediment flows from rill and 

gully erosion of roadfills were evaluated for 2 years 

after road construction. No sediment was transported 

beyond fills with slash filter windrows the first year 

after construction; average sediment flow distance 

below windrows was 3.8 feet the second year after 

construction (p. 41). This is considerably less than the 

average distance for fills that were not windrowed 

(p. 42). 

See other Horse Creek reports listed under this rule 

for additional information. 

Cook and King 1983, Horse Creek Study Area, Nez 

Perce National Forest-Sediment volumes and transport distances below fills were evaluated for 3 years 

after road construction. All fills were 1.5:l slopes, and 

were seeded, hydromulched, and fertilized. Some had 

slash filter windrows constructed at the toe of the fill. 

Windrow construction at five stream crossings had a 

total length of 1,190 feet (pp. 2-4). 

Comparisons between windrowed fill sections and 

sections that were not windrowed in collection troughs 

below the fills indicated that 99 percent of eroded fill 

material was retained within the windrows (p. 3). The 

average volume of sediment collected in troughs below 

the windrows was 0.325 cubic feet per 100 feet of road 

for fill lengths of 0 to 10 feet, and 0.650 cubic feet per 

100 feet of road for fill lengths of 10 to 20 feet. 

Corresponding values for fills that were not windrowed were 35.85 cubic feet per 100 feet of road (fill 

lengths of 0 to 10 feet) and 64.30 cubic feet per 100 feet 

of road (fill lengths of 10 to 20 feet, pp. 3-4). Surveys of 

rills and gullies in the fills provided another means of 

estimatingwindrow performance. Based on these data, 

the authors conservatively estimated that the windrows trapped 75 to 85 percent of the sediment (p. 4). 
Only seven sediment flows were observed below the 

windrowed fills in the 3-year study period; three of 

these delivered sediment to the stream. If widdrows 

were breached, it was usually because of slumping 

when snowmelt saturated the fill (p. 4). Average transport distance for sediment flows was 3.8 feet below 

windrows. For fills that were not windrowed, the 

average transport distance was 41.4 feet for flows 

originating in slumps, and 24.2 feet for flows originating in areas of the fill that had not slumped (p. 4). 

See other Horse Creek reports listed under this rule 

for additional information. 

Burroughs and King 1985, Horse Creek Study Area, 

Nez Perce National Forest-Simulated rainfall was 

applied to 1.5:1(67 percent) fillslopes to evaluate the 

relative effectiveness of an established dense stand of 

grass, wood excelsior mulch with nylon netting over 

loose soil, or loose soil with a filter windrow, compared 

to loose soil. The grass stand had 97 percent cover of 

grass, litter, and stones greater than 0.25 inches in 

diameter; species were primarily orchardgrass and 

smooth brome. Four applications of simulated rainfall 

were made for each treatment (pp. 186-187). The grass 

treatment reduced sediment by 99.5 percent, mulch by 

91 percent, and windrow by 87 percent, compared to 

bare loose soil (D. .. 189). This studv indicates that " 

windrows can provide effective protection immediately following construction; other observations in the 

study area confirmed that windrows were still effective 7 years after road construction (p. 190). 

Burroughs and King 1989, Horse Creek Study Area 

and Gospel Hump management areas, Nez Perce National Forest-Most of these results have been summarized before. 

The Horse Creek fillslope sediment data from one 

road were summarized for 2 years after construction 

(p. 9), showing the influence of slash filter windrows, 

road surface drainage, slumping, and culverts. Windrowed fills had the shortest average (3.8 feet) and 

maximum (33 feet) transport distances of the five 

categories. Material below windrows was often transported over the snowpack during the spring rather 

than through the windrow (p. 8). 

The influence of obstruction density (rated on an 

index from 0 to 6, with 6 most dense) on sediment 

transport distance was reported for Gospel Hump (p. 9). 

Obstructions included slash, shrubs, depressions, and 

so forth below the fills. Transport distance decreased 

as the obstruction index increased. 

Ketcheson and Megahan 1990, Silver Creek Study 

Area, Boise National Forest-The volumes and lengths 

of sediment flows below roads were measured for 

4 years after road construction. Sediment flows from 

fills traveled an average of 20 feet (p. 3); the maximum 

distance was less than 200 feet (p. 12). Sediment 

volume and the distance sediment traveled did not 

differ significantly between fills with and without cull 

logs placed at the toe (p. 3). 

Obstructions can deflect or stop sediment flow if 

they are large, in good contact with the ground, and 

oriented perpendicular to the slope. Small stems are 

generally ineffective (p. 11). 

See Burton (n.d.) for additional information. 

Burton (n.d.), unpublished data attributed to 

Megahan, Silver Creek Study Area, Boise National 

Forest-Sediment storage behind obstructions and 

the lengths of sediment flow were strongly correlated 

(p. 2). An equation relating sediment flow travel distance to sideslope gradient, source area, total length of 

obstructions, and total volume of on-site erosion was 

derived (p. 3). 

See Ketcheson and Megahan (1990) for additional 

information. 

See the General Erosion Research Summary. 

BMP 130-Rule 4.c.v. Construct stream channel 

crossings in compliance with minimum standards for 

stream channel alterations under the provisions of 

Title 42, Chapter 38, Idaho Code. 

No references were found, other than those listed 

under the corresponding Forest Practices Act BMP's. 

BMP 131-Rule 4.c.v. Avoid road construction in 

stream channels. 

See Rule 4.b.i., minimum road constructionin stream 

protection zones and road buffer strip rules (BMP's 86 

through 88) and Rule 4.b.vi., minimum stream crossings (BMP 106). 

BMP 132--Rule 4.c.v. Construct roads that constrict upon a stream channel in compliance with minimum standards for stream channel alterations under 

provisions of Title 42, Chapter 38, Idaho Code. 

No references were found, other than those listed 

under the corresponding Forest Practices Act BMP's. 

BMP 133-Rule 4.c.vi. During and following operations on outsloped roads, retain outslope drainage. 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-Field investigations evaluated the construction and initial performance of a road designed to minimize environmental impacts. The road was designed as an outsloped 

road, but skidded logs and skidding tractors created 

ruts in the road surface (p. 13). The authors felt that 

concentrations of water would occur on almost any 

outsloped road under normal trac conditions (p. 20). 

A berm left by a grading operation concentrated 

water that eventually drained onto the fillslope. During a heavy 4-day rainstorm, 165 cubic yards of fill 

material eroded (p. 18); the berm was the single most 

important factor contributing to erosion (p. 13). 
Burroughs and King 1989, Horse Creek Study Area, 

Nez Perce National Forest-Sediment entering the 

stream by the ditch system (representing erosion of 

the cut, ditch, and 28 percent of the road surface) and 

that entering from the fillslope side (representing 

erosion of the fillslope and 72 percent of the road 

surface) was monitored for 4 years following construction on a crowned road section (p. 16). At the study site, 

the cut and fill had no erosion control treatment, and 

the road was unsurfaced (p. 15). A berm was created 

unintentionally during construction and maintenance 

activities. This berm concentrated drainage onto the 

fill and contributed to high fill erosion rates during the 

first year, when 80 percent of the sediment entered by 

the fillslope side of the road (p. 16). 

The authors recommend insloping to the ditch or 

providing uniform distribution for outslope drainage. 

Outsloped sections would require careful road maintenance to avoid creating berms and to maintain uniform drainage (p. 16). 

See Rule 4.b.iv., outsloping and insloping rules 

(BMP's 97 and 98). 

BMP 134--Rule 4.c.vi. During and following operations on outsloped roads, remove berms on the outside 

edge except those intentionally constructed for protection of road grade fills. 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-Field investigations evaluated the construction and initial performance stages of an outsloped road designed to 

minimize environmental impacts. A berm left by a 

grading operation concentrated water that eventually 

drained onto the fillslope. During a heavy 4-day rainstorm, 165 cubic yards of fill material eroded (p. 18); 

the berm was the single most important factor contributing to erosion (p. 13). 

Megahan and others 1986, Silver Creek Study Area, 

Boise National Forest-Erosion and sediment were 

evaluated in three watersheds during road construction. During construction, erosion offen depended more 

on the stage of road construction during rainstorms 

than on the final design features of the road. The 

authors recommended that temporary berms be constructed to protect fills when storm threats are high 

(P. 39). 

Burroughs and King 1989, Horse Creek Study Area, 

Nez Perce National Forest-Sediment entering the 

stream by the ditch system (representing erosion of 

the cut, ditch, and 28 percent of the road surface) and 

that entering from the fillslope side (representing 

erosion of the fillslope and 72 percent of the road 

surface) was monitored for 4 years after construction 

on a crowned road section (p. 16). At the study site, the 

cut and fill had no erosion control treatment, and the 

road was unsurfaced (p. 15). 

A berm was created unintentionally during construction and maintenance. The bed concentrated drainage 

onto the fill and contributed to high f3l erosion rates 

during the first year, when 80 percent of the sediment 

entered from the Wlope side of the road (p. 16). 

The authors recommend insloping to the ditch or 

providing uniform distribution for outslope drainage. 

Outsloped sections require careful road maintenance 

to avoid creating berms and to maintain uniform 

drainage (p. 16). 

BMP 136-Rule 4.c.vii. Provide for drainage of 

quarries to prevent sediment from entering streams. 

Bachmann 1958, Silver and Crystal Creeks, near 

Pierce-This study investigated the effects of logging 

and logging road construction on selected physical, 

cffemical, and biological features of northern Idaho 

trout streams (pp. 2-3), using a paired-watershed approach (p. 9). Measured predisturbance (1955 and 

1956) turbidities ranged from 0.25 to 2.10 parts per 

million in Silver Creek, and from 0.6 to 6.9 parts per 

million in Crystal Creek (p. 34). 

Rock was quarried in the Crystal Creek watershed 

during road construction in 1956 and 1957 (p. 22). The 

quarry was adjacent to a small tributary, and was a 

major source of sediment (p. 30). Sediment deposits 

nearly covered the channel below the quarry. 

Turbidities at the sampling station near the quarry 

were among the highest measuredin the study (p. 30). 

For example, turbidity ranged to 350 parts per million 

during snowmelt and to 2,169 parts per million after 

a 12-hour rain (p. 36). Turbidity sampling was not 

adequate to dehe average or maximum values (p. 37). 

BMP 136--Rule 4.c.viii. Construct cross drains to 

minimize erosion of embankments. 

Haupt and others 1963, Zena Creek Logging Study 

Area, Payette National Forest-Following three longduration, low-intensity storms of unprecedented total 

rainfall (pp. 4-5), the erosiononinsloped and outsloped 

road sections of a newly constructed loggingroad were 

compared visually. Both insloped and outsloped sections had earthen cross drains spaced 30 to 90 feet 

apart (p. 2). Shoulders and fills had been seeded and 

mulched with chopped hay and asphalt binder (p. 3). 

All earthen cross drain outlets were deeply eroded 

on the outsloped portions (p. 6). Cross drains also 

generated fill erosion on insloped sections. Cross drain 

outlets were the only site where surface drainage 

overtopped the inslope (p. 7). Based on their observations, the authors recommended that if earthen cross 

drains are to be used, they should drain on the outcurve 

(p. 8). 

See Rule 4.b.iv., dipslwater bars/cross drain rules 

(BMPs 100 through 102); Rule 4.c.iii., stabilization of 

exposed material (BMP's 117 through 122); and the 

General Erosion Research Summary. 
BMP 137-Rule 4.c.viii. Construct relief culverts to 

minimize erosion of embankments. 

Gonsior and Gardner 1971, Zena Creek drdinage, 

Payette National Forest-During the authors investigations of slope failures in the Idaho Batholith, low soil 

permeablilities were measured. Permeability can be 

expected to decrease over time in roadfills and elsewhere; this must be considered when designing culverts (p. 12). The authors stress the need to evaluate 

surface and subsurface flow water conditions when 

locating and designing roads (p. 33). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-A road designed to minimize watershed impacts was evaluated 

during the construction period and the early period of 

use. The authors recommended against using dimpled 

connecting bands on culverts to avoid leakage and to 

prevent sections from separating. They also recommended skewing culverts or using downspouts to 

avoid steep culvert gradients that result in scour (p. 

10). Proper bedding of culverts and compaction of 

backfill material are discussed (p. 12). 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-Travel distances for sediment flows from rill and gully erosion of roams were 

evaluated for 2 years after road construction. Flows 

influenced by relief culverts (the source gully was below 

or adjacent to culverts) tendedto travel farther (pp. 41-42). 

See Burroughs and King (1989) for additional 

information. 

Burroughs and King 1989, Horse Creek Study Area 

and Rainy Day Road, Nez Perce National Forest-In 

the Horse Creek Study Area, rill volumes and sediment flow transport distances were measured for 

2 years after road construction. One of the longest 

average transport distances (72.8 feet) for sediment 

flows below road fillslopes resulted when rills formed 

below relief culvert outflows or when sediment flows 

from rills combined with the paths of relief culvert 

flows (pp. 8-9). Transport distances below relief culverts were not strongly correlated with the length of 

road contributing to the culvert, the road gradient, or 

the sideslope gradient (p. 10). The authors developed 

a cumulative frequency distribution of sediment travel 

distances for flows influenced by relief culverts (p. 10); 

this might apply to similar sites with gneiss and schist 

parent material and sideslope gradients of 30 to 40 

percent (p. 11). 

See Tennyson and others (1981) for additional 

information. 

See Rule 4.b.v., relief culvert rule (BMP 103) and 

culvert installationrule (BMP 104); Rule4.c.iii., stabilization of exposed material (BMP's 117 through 122); 

and the General Erosion Research Summary for additional information. 

BMP 138-Rule 4.c.viii. Minimize the time between 

construction and installation of erosion control devices. 

No references were found that directly address time 

trends in fill erosion due to outflow from drainage 

structures. However, numerous studies show time 

trends that illustrate the need for timely application of 

erosion control measures. For examples oftime trends 

ranging from days to years see: Ohlander (1964), p. 29; 

Bethlahmy and Kidd (1966), p. 4; Megahan (1978), 

pp. 352-353; Carlton and others (1982), p. 30; Cook and 

King (1983), p. 4; Megahan and others (1992), p. 64. 

BMP 139--Rule 4.c.viii. Use riprap to minimize 

erosion of the fill. 

No references were found; see the General Erosion 

Research Summary. 

BMP 140-Rule 4.c.viii. Use vegetative matter to 

minimize erosion of the fill. 

No references were found. See Rule 4.c.iii., stabilization of exposed material by seeding (BMP 117), mulching (BMP 121), and other suitable means (BMP 122); 

and the General Erosion Research Summary. . 

BMP 141-Rule 4.c.viii. Use downspouts to minimize erosion of the fill. 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-A road designed to minimize watershed impacts was evaluated 

during the construction period and the early period of 

use. Based on their observations, the authors recommended skewing culverts or using downspouts to 

avoid steep culvert gradients that result in scour (p. 10). 

BMP 142--Rule 4.c.viii. Use similar devices [similar to downspouts] to minimize erosion of the fill. 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-A road designed to minimize watershed impacts was evaluated 

during the construction period and the early period of 

use. Based on their observations, the authors recommended skewing culverts or using downspouts to 

avoid steep culvert gradients that result in scour 

(p. 10). 

See Rule 4.c.iii., stabilization of exposed material 

(BMP's 117 through 122), and the General Erosion 

Research Summary. 

BMP 143--Rule 4.c.viii. Install drainage structures 

on incomplete roads that are subject to erosion prior to 

fall or spring runoff (first alternative). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-Field investigations evaluated the construction and initial performance stages of a road designed to minimize environmental impacts. The road was designed as an 

outsloped road, but skidded logs and skidding tractors 

created ruts in the road surface (p. 13). During a heavy 
4-day rainstorm on Labor Day weekend, this road had 

considerable erosion, which was largely attributed to 

incomplete shaping and grading (p. 19). A half-mile 

length of pioneer road had no erosion., even though it 

had no drainage structures installed. This was attributed to minimal disturbance of natural drainage patterns, flat grade or short stretches of unbroken grade, 

and loose, absorbent soil conditions (p. 15). The authors suggested that the best solution might be to 

construct a minimum standard contour road with a 

rolling grade, including drainage structures, during 

logging operations. Each road section could then be 

completed to the desired standard when log hauling 

was finished on that section (p. 19). 

Megahan and others 1986, Silver Creek Study Area, 

Boise National Forest-Erosion and sediment were 

evaluated in three watersheds during road construction. Erosion during construction often depended more 

on the stage of road construction during rainstorms 

than on the final design features of the road. The 

authors recommended that temporary berms be constructed to protect fills when storm threats are high 

(P. 39). 

No references were found that dealt directly with 

erosion due to lack of drainage structures on incomplete roads during spring and fall runoff. However, 

many references have implications for this rule. See 

Rule 4.c.viii., time between construction and installation of erosion control devices (BMP 138). References 

listed there show fill erosion time trends. See Megahan 

and Kidd (1972a, p. 8) for seasonal and annual time 

trends in total road erosion. In the General Erosion 

Research Summary, see Burroughs and others (19721, 

regarding spring runoff; Megahan (1972), regarding 

spring runoff; Megahan (1974b), regarding road erosion time trends; Vincent (1985), regarding seasonal 

runoff and sedimentation from road tread; and 

Ketcheson and Megahan (1990), regarding seasonal 

and annual trends in total road erosion. 

BMP 14ARule 4.c.viii. Install cross drains on 

incomplete roads that are subject to erosion prior to 

fall or spring runoff (second alternative). 

No references were found that directly address this 

rule; see Rule B.c.viii., drainage structures for incomplete roads subject to erosion (BMP 143); and Rule 

4.b.iv., cross drain rules (BMP's 100 through 102). 

BMP 146-Rule 4.c.viii. Install relief culverts with 

a minimum grade of 1 percent. 

No references were found. 

BMP 146--Rule 4.c.i~. Postpone earthwork during 

wet periods, if, as a result, erodible material would 

enter streams. 

No references were found that directly address 

earthwork during wet periods; however, the following 

studies have some implications for this rule. 

Burroughs and others 19833, Rainy Day Road, Nez 

Perce National Forest-Simulated rainfall was applied repeatedly to new road prism surfaces (cut, 

tread, and ditch). Initial sediment yields on the unprotected surfaces were high but yields declined rapidly 

(p. 9). Sediment yields increased 108 percent when the 

unsurfacedroadtread was ruttedrather than unrutted; 

these yields also decreased rapidly with successive 

applications of simulatedrainfall (p. 16). However, the 

rapid amnoring that occurred on these study plots 

might not have occurred if traffic had been present 

(p. 22). 

Foltz and Burroughs 1990, Tin Cup Creek, Caribou 

National Forest, east ofIdaho Falls-Three 30-minute 

applications of simulated rainfall were applied to 

paired roadway surface plots, one rutted and one 

unrutted. There was a thin layer of loose material over 

a compacted, bladed road surface (p. 272); gradients of 

the plots were 8.4 and 9.0 percent (p. 269). Sediment 

production from the rutted plots decreased sharply 

over time after the first 20 minutes, reflecting a limited supply ofmaterial for transport (p. 272). Sediment 

production from the unrutted plots rose for about the 

first 30 minutes, but then maintained a more level 

sediment production with a slight decline at about 45 

minutes. The sediment levels from the rutted plot 

were consistently higher than those from the unrutted 

plot, peaking at 90 grams per second, compared to 32 

grams per second for the unrutted plot (p. 272). When 

the data were adjusted to account for the relative 

proportions of rutted and unrutted surface on a road 

with two ruts, the sediment production ratios were 2.1 

(dry conditions), 1.2 (wet conditions), and 1.0 (very wet 

conditions); the different conditions correspond to the 

measurements during the three applications of simulated rainfall (pp. 273-274). Road closures and other 

measures are recommended to prevent rutting during 

wet weather (p. 275). 

Megahan and others 1991, Silver Creek Study Area, 

Boise National Forest-Several site factors were tested 

as predictors of fillslope erosion during snowfree periods. Only ground cover density and rainfall erosivity 

were statistically significant (p. 56). 

BMP 147-Rule 4.c.x. In rippable materials, construct roads with no overhanging banks. 

No references were found. 

BMP 148-Rule 4.c.x. In rippable materials, fell 

any trees that present a potential hazard to tr&c 

concurrently with the construction operation. 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-Extensive field and laboratory analyses of slope failures were conducted. The 

authors felt that live trees were important sources of 

slope stability by mechanicallyreinforcing the soil and 

depleting moisture (and possibly slowing subsurface 
weathering by moderating temperatures). They recommended leaving barriers of live trees immediately 

below the fill and above the cut (pp. 31-32). 

Burroughs and Thomas 1977, South Fork Payette 

River near Lowman, Boise National Forest-Rocky 

Mountain Douglas-fir root numbers and tensile 

strength over time were measured on clearcut and 

undisturbed slopes. All sampling areas were within 

old-growth sites (100- to 200-year-old trees). Tensile 

strength of tree roots was shown to be an important 

factor increasing slope stability onlogged andunlogged 

slopes. However, root strength decreases rapidly in 

the first year after tree felling, continuing to decrease 

gradually over time (p. 16). 

Megahan and others 1979, Clearwater National 

Forest and Middle Fork Payette River drainage, Boise 

National Forest-In the two study areas, 1,418 landslides were inventoried (p. 121). The frequency of 

landslides tended to increase as either tree or shrub 

crown cover decreased (p. 132). When crown covers 

were less than 80 percent, landslide occurrence appeared to be more sensitive to reductions in shrub 

crown cover than to reductions in tree crown cover. 

The authors recommended using timber harvest procedures that minimize the disturbance of understory 

vegetation (p. 132). Landslides were most common 4 to 

10 years after logging; ladslide frequencies remained 

elevated for 20 years after logging (p. 133). These time 

trends were attributed to the loss of root strength 

through decay (increasing landslide frequency), interacting with growth of new roots (decreasing landslide 

frequency) (p. 132). 

Gray and Megahan 1981, Pine Creek Study Area, 

Middle Fork of the Payette River drainage, Boise National Forest-Several analyses evaluated the contributions of forest vegetation to slope stability through 

various mechanisms. The analyses showed that many 

sites in the Idaho Batholith are in a state of marginal 

equilibrium, and may fail when roads are constructed 

or trees are harvested (p. 20). The authors recommended leaving buffer zones of trees above and below 

haul roads, although they noted that the benefits of 

leaving trees must be weighed against the safety 

hazards they represent (p. 21). 

Megahan and others 1983, Silver Creek Study Area, 

Boise National Forest-Long-term (45-year) cutslope 

erosion was estimated using exposed tree roots. Reductions in soil erosion due to tree roots were observed 

in the field and were also apparent from the data. The 

authors indicate that this benefit should be considered 

when deciding whether to cut trees above road cutslopes (p. 27). 

Megahan and Bohn 1989, Silver Creek Study Area, 

Boise National Forest-Three progressive mass failures (sapping failures) were monitored after logging 

and road construction. This type of failure had never 

been observed previously in the study area. Two of the 

failures occurred at low gradient sites (9 and 11 percent) in cutting units and were attributed to changes 

in seepage flows due to logging (p, 508). The other 

failure originated in a road cutslope and was attibuted to the steepness (34 percent) of the cutslope 

(p. 508). Mass erosion hazards in the cutslope are 

increased if timber is harvested above the roadcut 

(p. 509). Tree roots were observed to slow the uphill 

progress of failure and to retain soil that would otherwise collapse (pp. 504,506). 

See the General Erosion Research Summary for 

additional information. 

Rule 4.d. Road Maintenance 

Forty BMP's (149 through 188) were evaluated. Best 

management practices 149 and 150 comprise the general rule 4.d.: "Conduct regular preventive maintenance operations to avoid deterioration of the road 

surface and minimize disturbance and damage to 

forest productivity, water quality, and fish and wildlife habitat." The remaining BMP's addressed several 

specific topics associated with road maintenance: 

Disposition of maintenance products (BMP's 151 

and 152) 

Repair and stabilization of slumps, slides, and 

similar failures (BMP's 153 through 158) 

Maintenance of culverts and ditches (BMP's 159, 

160,170,171, 177,184,188) 

Controlling road surface drainage through crowning, outsloping, insloping, water barring, berm 

removal, and similar practices (BMP7s 161 through 

165,172 through 176,180 through 181) 

Maintenance of the road surface (BMP's 166 

through 169) 

Road closures (BMP's 178,179,185) 

Seeding and other erosion control measures on 

abandoned roads (BMP's 182 and 183) 

Bridge removal on abandoned roads (BMP 186) 

Culvert removal on abandoned roads (BMP 187). 

Disposition of Maintenance Products 

No references were found on this topic. 

Repair and Stabilization of Slumps, Slides, and 

Similar Failures 

In the Horse Creek Study Area, Burroughs and King 

(1989, pp. 8-9) measured sediment flow transport from 

rills and gullies on fillslopes for 2 years after road 

construction. The longest average transport distance, 

80.4 feet, was for sediment flows from rills formed in 

slurnpedmaterial (pp. 8-9). Megahan and others (1979) 

inventoried landslides on the Clearwater and Boise 
National Forests. On average, 19 percent of the slide 

material was delivered to a stream (p. 121). Costs of 

road repair and slide stabilization were estimated for 

the Clearwater slides (p. 135). 

Maintenance of Culverts and Ditches 

No references were found on maintenance of culverts. Three references alluded to the role of ditch 

maintenance in perpetuating cutslope erosion. Arnold 

and Lundeen (1968, p. 117) surveyed road erosion on 

the roads producing the most sediment in the South 

Fork Salmon River drainage. They estimated that 10 

percent of sediment originated from cutslopes and 

ditches; 21 percent originated from maintenance wasting of cutslope material. Megahan and others (1983, p. 

28) noted that road maintenance is the primary cause 

of long-term accelerated cutslope erosion. Removal of 

slough material at the base of the roadcut during 

maintenance operations interferes with the natural 

slope-forming process, removes a favorable site for 

vegetation growth, and reinitiates slope erosion processes. They suggested that removal of the material 

deposited at the base of the roadcut be avoided or 

minimized whenever possible, for instance, on forest 

roads that are used infrequently. Similarly, Burroughs 

and King (1989, pp. 12-13) observed that ditch maintenance often undercuts the cutslope, reinitiating cutslope erosion processes. 

Controlling Road Surface Drainage Through 

Crowning, Outsloping, Insloping, Water Barring, 

Berm Removal, and Similar Practices 

No references were found on crowning. Research on 

all the other methods was reviewed under Rule 4.b. or 

Rule 4.12.; the corresponding BMP's under those rules 

are cross-referenced. For outsloping and insloping, 

refer to Rule 4.b.iv., outsloping and insloping rules 

(BMP's 97 and 98). For water bars, refer to Rule 4.b.iv., 

dips, water bars, and cross drains (BMP's 100 through 

102). For berm removal, refer to Rule 4.c.vi., berm 

removal (BMP 134). 

Maintenance of the Road Surface 

Packer and Christensen (1964, p. 2) noted that 

research indicated secondary logging road surfaces 

deteriorate rapidly when rill depths exceed 1 inch. 

Packer (1967) tested 14 road and watershed variables 

as predictors of the surface water flow distance producing 1-inch rills. The multiple regression equation 

developed from the most important predictive variables was used to make a table (Packer 1967, p. 11; 

Packer and Christensen 1964, pp. 13-15) that gives 

recommended cross drain spacings (to prevent 1-inch 

rill formation) by road grade and soil type, with adjustments for topographic position, aspect, slope steepness, 

and the percent of cases in which 1-inch rill formation 

is to be prevented. 

In Packer's analysis (1967, pp. 8-9) the most important predictive variable was the proportion of soil 

particles and water-stable aggregates larger than 2 

mm on the road surface. Although this property is 

related to the soil group, the benefits of larger particles 

can be derived on all soil types by surfacing roads with 

gravel or crushed rock. Similarly, in tests with simulatedrainfall on various road surface types, Burroughs 

and others (1983a, p. 10) found that sediment yield 

was correlated directly with the amount ofloose soil on 

the surface, and inversely correlated with the average 

size of the loose soil. A later publication on the same 

study (Burroughs and King 1985, p. 187) reported that 

sediment yields from dust oil surfaces were about 13 

percent of the yield from the native surfaces at the 

same gradient,and that yields from bituminous surfaces were just 1.1 percent of those from native surfaces. However, Burroughs andKing (1989, p. 2) noted 

that dust oil surfaces break down under heavy traffic 

and also contribute volatile chemicals to surface runoff. Another simulated rainfall experiment (Burroughs 

and others 198313, p. 1) indicated that a travelway 

(road tread) with gravel surfacing produced only 23 

percent of the sediment yield of an unsurfaced 

travelway. The same study also indicated that rocked 

ditches generatedless sediment than unrocked ditches. 

Burroughs and King (1989) summarized research 

results from Horse Creek and Gospel Hump. In both 

cases, sediment transport distpces below fills were 

generally larger for sediment flows influenced by 

travelway drainage (p. 9). 

Two studies with simulated rainfall indicated that 

rutted roads produce higher sediment yields than 

unrutted roads. Burroughs and others (1983b, p. 16) 

reported that sediment yields increased 108 percent 

when the unsurfaced road tread was rutted rather 

than unrutted; these yields decreased rapidly with 

successive applications of simulated rainfall. However, the rapid armoring that occurred on these study 

plots might not have occurred if traffic had been 

present (p. 22). In eastern Idaho, Foltz and Burroughs 

(1990, pp. 273-274) found that sediment yields on 

rutted roads were 1.0 to 2.1 times yields on unrutted 

roads, with the ratio depending on the moisture conditions before the simulated rainfall. 

Megahan (1974b) developed a negative exponential 

equation showing surface erosion on severely disturbed granitic soils over time. By far the greatest 

percentage of erosion occurs in the first and second 

years after construction (p. 12). Additional disturbances (such as road grading) result in new cycles of 

surface erosion(p. 13). This was supportedby Vincent's 

(1985) study of road surface sediment production in 

the Silver Creek Study Area. The study road was 

constructed in 1980, extensively eroded before the 
first measurements in 1981, and regraded before the 

1982 measurements (pp. 7-91. The road was less erodible in the eroded condition than in the regraded 

condition; a given amount of runoff generated 75 to 80 

percent less sediment for the eroded road in 1981 than 

for the regraded road in 1982 (p. 39), a reversal of the 

usual time trend. 

Megahan (1988, p. 341) stated that long-term accelerated erosion tends to continue on roads in direct 

proportion to traffic use and in inverse proportion to 

the level of road maintenance. Megahan and others 

(1983, p. 28) noted that road maintenance is the 

primary cause of long-term accelerated cutslope erosion. Removal of slough material at the base of the 

roadcut during maintenance operations interferes with 

the natural slope-forming process, removes a favorable site for vegetation growth, and initiates slope 

erosion processes. They suggested that removal of the 

material deposited at the base of the roadcut should be 

avoided or minimized whenever possible, on forest 

roads that are used Wequently, for instance. Arnold 

and Lundeen (1968, p. 117) surveyed road erosion on 

the roads producing the most sediment in the South 

Fork Salmon River drainage. They estimated that 21 

percent of sediment originated from maintenance wasting of cutslope material, and that just 4 percent originated from road surfaces. 

Road Closures 

Megahan (1988, p. 341) stated that long-term accelerated erosion tends to continue on roads in direct 

proportion to traffic use. 

In the South Fork Salmon River drainage, closed 

roads were inventoried to evaluate surface and mass 

erosion. Roads with light use (foot, horse, or motorcycle) showed greater average surface erosion than 

those with no use (Clifton and Megahan 1988, p. 4). 

Two studies with simulated rainfall indicated that 

rutted roads produce higher sediment yields than 

unrutted roads. Burroughs and others (1983b, p. 16) 

reported that sediment yields increased 108 percent 

when the unsurfaced road tread was rutted rather 

than unrutted; these yields decreased rapidly with 

successive applications of simuilated rainfall. However, they noted that the rapid armoring that occurred 

on these study plots might not have occurred if trac 

had been present (p. 22). In eastern Idaho, Foltz and 

Burroughs (1990, pp. 273-274) found that sediment 

yields on rutted roads were 1.0 to 2.1 times yields on 

unrutted roads, with the ratio depending on the moisture conditions before the simulated rainfall. They 

recommended road closures to prevent rutting during 

wet weather (p. 275). 

Seeding and Other Erosion Control Measures on 

Abandoned Roads 

Haupt and Kidd (1965) monitored the effectiveness 

of various techniques designed to minimize erosion 

associated with logging and logging road construction. 

These included seeding, harrowing, and cross draining of roads following logging in 1953 and 1954 

(p. 665). By 1958, the perennial grasses that had been 

seeded on the roadways were well established and 

erosion was negligible during the most intense storm 

(2.82 inches of rain per hour for 10 minutes) of the 

7-year study period (p. 668). 

Megahan and Kidd (1972a,b) studied erosion and 

sedimentation from logging and road construction. 

Roads built in October 1961 were seeded and water 

barred afterloggingwas completed inNovember 1962. 

The average sedimentation rate in ephemeral drainages below roads for 4.8 years after logging was 51.0 

tons per square mile per day. No data were collected 

for comparison on roads that were not seeded or water 

barred. Sedimentation rates on nearby undisturbed 

watersheds averaged 0.07 tons per square mile per 

day. A return to predisturbance levels was not expected due to continued roadcut and tread erosion. 

In the South Fork Salmon River drainage, closed 

roads were inventoried to evaluate surface and mass 

erosion (Cliftun and Megahan 1988). Erosion classes 

were used for surface erosion ratings, with 1 = natural, 

2 = very low, 3 = low, 4 = moderate, and 5 = high (p. 2). 

Average values for roadfills and road tread were each 

slightly less than2, while the average value for roadcuts 

was 2.6 (p. 3). On all road prism components (roadcut, 

road tread, and roadfill), correlation analyses showed 

that as ground cover densities increased, surface erosion decreased. Roadcuts were most sensitive to 

changes in cover density (p. 5). Ground cover included 

litter and rocks, as well as vegetative cover. 

Because cutslopes exhibited the greatest erosion 

and were more sensitive to changes in cover, Clifton 

andMegahan (1988) recommended that cutslope revegetation be given priority for rehabilitation measures 

(p. 6). 

Multiple regression analyses also were conducted 

for each component of the road prism. Of 19 variables 

tested, the roadcut cover density and bedrock weathering class explained 86 percent of the variance in 

roadcut surface erosion (p. 6). Of 40 variables tested, 

the roadfill cover density explained 69 percent of the 

variance in roadfill surface erosion (p. 7). Of 25 variables tested, the percent road tread cover outside 

wheel tracks explained 53 percent of the variance in 

road tread surface erosion (p. 6). 

A followup report (Clifton and Thompson 1989) 

noted that 73 percent of the variation in surface 
erosion (for cut, tread, and fill combined) was explained by the cover density variable (p. 4). Ground 

cover included litter and rocks as well as vegetativecover. Average cover densities were 85 percent on 

roadcuts, 90 percent on road tread, and 91 percent on 

roadfills (p. 13). 

See Rule 4.c.iii., stabilization of exposed material 

(BMP's 117 through 122) and the General Erosion 

Research Summary for additional information. 

Bridge Removal on Abandoned Roads 

No references were found on this topic. 

Culvert Removal on Abandoned Roads 

Jensen and Finn (1966, pp. 87,90) described road 

rehabilitation in the Deep Creek drainage. Rehabilitation consisted of digging channels across the road to 

reopen ephemeral drainages, constructing dips every 

100 feet, and removing all culverts and fill material in 

draws. The roadway was seeded to perennial grasses. 

The authors recommended using the same techniques 

in future rehabilitation efforts on decomposed granitic 

landtypes, using a dragline (if possible without major 

reconstruction) and a D-7 or D-8 tractor. They noted, 

however, that even with such efforts, it would be 

impossible to stop most of the accelerated sedimentation or to restore the natural hydrologic function that 

had been altered by roadcuts (p. 91). 

In the South Fork Salmon River drainage, surface 

and mass erosion were evaluated on 13 closed logging 

roads about 20 years after they were closed (Clifton 

and Thompson 1989, p. 3). The authors identified 

problem sites with the potential to deliver sediment to 

streams, assigning values for the potential delivery to 

streams (1 = no potential through 9 = sediment supplied directly to the watercourse) and priority for 

treatment (1 = high priority through 9 = low priority). 

The five types of problem sites, in order of decreasing 

frequency, were: culverts with fill intact, road gullies, 

washouts, various diversion problems, and plugged 

culverts (p. 17). 

Culverts with fill intact were the most common 

problem site (28 percent of total) and were of two types: 

log culverts and pipe culverts. Each log culvert stored 

an estimated 23 to 26 cubic yards of sediment, which 

would be released slowly as the logs rotted. Removal 

would be difficult due to heavy vegetative cover on the 

culvert (spruce, alders, mosses) and difEculty of access. The average sediment delivery potential rating 

was 9; the problem priority rating was 4.7. Pipe culverts stored about 6 to 8 cubic yards of sediment that 

would be released when the culverts failed. The average sediment delivery potential rating for pipe culverts was 6.1; the problem priority rating was 4.8 

(p. 17). 

Culverts plugged with debris were the least frequent of the problem sites. At these sites, seasonally 

active watercourses were being rerouted across the 

road. The average sediment delivery potential rating 

was 5.2; the problem priority was 5.2 (p. 17). 

Research Results by Best Management 

Practice 

BMP 149-Rule 4.d. Conduct regular preventive 

maintenance operations to avoid deterioration of the 

roadway surface. 

See Rule 4.d.iii.(c)., maintenance of the road surface 

(BMP's 166 and 167). 

BMP 160-Rule 4.d. Conduct regular preventive 

mmintenance operations to minimize disturbance and 

damage to forest productivity, water quality, and fish 

and wildlife habitat. 

See subrules below (BMP's 151 through 188) and the 

General Erosion Research Summary for additional 

information. 

BMP 161-Rule 4.d.i. Sidecast all debris associated 

with road maintenance in a manner to prevent its 

entry into streams. 

No references were found. 

BMP 152--Rule 4.d.i. Sidecast all slide material 

associated with road maintenance in a manner to 

prevent its entry into streams. 

No references were found. 

BMP 163--Rule 4.d.ii. Repair slumps causing stream 

sedimentation. 

Burroughs and King 1989, Horse Creek Study Area, 

Nez Perce National Forest-Sediment flow transport 

from rills and gullies on fillslopes was measured for 2 

years after road construction. The longest average 

transport distance, 80.4 feet, was for sediment flows 

from rills formed in slumped material (pp. 8-91. 

See Rule 4.d.ii., slide repair rule (BMP 155) for 

additional information. 

BMP 164-Rule 4.d.ii. Stabilize slumps causing 

stream sedimentation. 

See Rule 4.d.i.i., slump repair rule (BMP 153), and 

the slide repair rule (BMP 155). 

BMP 155-Rule 4.d.ii. Repair slides causing stream 

sedimentation. 

Day and Megahan 1977, Clearwater National Forest-The authors directed an inventory of 629 new 

landslides (including slumps and other mass failures 

over 10 cubic yards in volume) over a 3-year period 

(1974-1976). The year 1974 had more landslide activity than average due to a rain-on-snow event in January (p. 1). Total volume of the slides was 716,500 cubic 
yards; of this, 166,000 cubic yards were delivered to should be avoided or minimized whenever possible, on 

streams (p. 6). The average annual cost of road repair forest roads used infrequently, for instance (p. 28). -. 

was estimated be $130,'00; the average Burroughs and King;989, literature 

of road stabilization was estimated to be $1,100,000 review-Maintenanee of the diWl oftenundermts tb (P. 6). cutslope and initiates cutslope erosion processes (pp. 

Megahan and others 1979, Clearwater National 12-13). 

Forest and Middle Fork Payette River drainage, Boise 

National Forest-On the Clearwater National Forest, 

629 new landslides (including slumps and other mass 

failures over 10 cubic yards in volume) were inventoried over a 3-year period (1974-1976). In the Middle 

Fork Payette River drainage, 789 landslides (mass 

failures over 10 cubic yards in volume) of varying ages 

were inventoried. On average, 19 percent of the slide 

material was delivered to a stream (p. 121); a total of 

304,000 cubic meters of material was delivered to, 

streams (p. 135). The costs of road repair and slide 

stabilization were estimated for the Clearwater slides 

(p. 135; or see Day andMegahan 1977, summary above). 

The costs of stabilization were about nine times greater 

than road repair. 

BMP 166-Rule 4.d.ii. Stabilize slides causing 

stream sedimentation. 

See Rule 4.d.ii., slide repair rule (BMP 155). 

BMP 167-Rule 4.d.ii. Repair other erosion features causing stream sedimentation. 

See Rule 4.d.ii., slide repair rule (BMP 155). 

BMP 168-Rule 4.d.ii. Stabilize other erosion features causing stream sedimentation. 

See Rule 4.d.ii., slide repair rule (BMP 155). 

BMP 169-Rule 4.d.iii.(a). Keep culverts functional 

(active roads). 

No references were found. 

BMP 160-Rule 4.d.iii.(a). Keep ditches functional 

(active roads). 

Arnold and Lundeen 1968, South Fork Salmon River 

drainage-A survey of road erosion on the roads producing the most sediment in the drainage found that 

65 percent of sediment originated from fillslopes, 10 

percent from cutslopes and ditches, 21 percent from 

maintenance wasting of cutslope material, and 4 percent from road surfaces (p. 117). 

Megahan and others 1983, Silver Creek Study Area, 

Boise National Forest-Long-term (45-year) cutslope 

erosion was estimated using exposed tree roots. The 

authors noted that road maintenance is the primary 

cause of long-term accelerated cutslope erosion. Removal of slough material at the base of the roadcut 

during maintenance operations interferes with the 

natural slope-forming process, removes a favorable 

site for vegetation growth, and reinitiates slope erosion processes. The authors suggested that removal of 

the material deposited at the base of the roadcut 

BMP 161-Rule 4.d.iii.(b). During andupon completion of seasonal operations, crown the road surface 

(active roads) (first alternative). 

No references were found. 

BlVIP 162-Rule 4.d.iii.(b). During andupon completion of seasonal operations, outslope the road surface 

(active roads) (second alternative). 

BMP 163-Rule 4.d.iii.(b). During anduponcompletion of seasonal operations, inslope the road surface 

(active roads) (third alternative). 

See Rule 4.b.iv., outsloping and insloping rules 

(BMP's 97 and 98). 

BMP 1-Rule 4.d.iii.(b). During andupon completion of seasonal operations, water bar the road surface 

(active roads) (fourth alternative). 

See Rule 4.b.iv., dips, water bars, and cross drains 

(BMP's .lo0 through 102). 

BMP 166-Rule 4.d.iii.(b). Duringanduponcompletion of seasonal operations, remove berms fkom the 

outside edge except those intentionally constructed 

for protection of fills (active roads). 

See Rule 4.c.vi., berm removal (BMP 134). 

BMP 166-Rule 4.d.iii.(c). Maintain the road surface as necessary to minimize erosion of the subgrade 

(active roads). 

Packer and Christensen 1964,720 sites in Idaho and 

Montana, representing six soil groups-Previous research had indicated that secondary logging road 

surfaces deteriorate rapidly when rill depths exceed 

1 inch (p. 2). Based on the research later reported in 

Packer (1967), the authors suggested cross drain spacings to prevent 83 percent of the cases of 1-inch rill 

formation. A table (pp. 13-15) gives recommended 

spacings byroadgrade and soil type, with adjustments 

for topographic position, aspect, slope steepness, and 

the percent of cases in which 1-inch rill formation is 

prevented. 

Packer 1967, 720 sites in Idaho and Montana, representing six soil groups-This publication explains the 

theoretical basis, research design, and data analysis 

that led to the field guide of Packer and Christensen 

(1964). Fourteen road and watershed variables were 

tested as predictors of surface water flow distance 

producing 1-inch rills. The most important variable 

was the proportion of soil particles and water-stable 

aggregates larger than 2 mm on the road surface. 
Although this property is related to the soil group, the 

benefits of larger particles can be derived on all soil 

types by surfacing roads with gravel or crushed rock 

(pp. 8-91. The multiple regression equation developed 

from the most important predictive variables was 

used to make a table (p. ll), which is the same as the 

table in Packer and Christensen (1964, pp. 13-15). 

Megahan 19743, four sites in the Idaho Batholith: 

Deep Creek, Silver Creek, Bogus Basin, and Deadwood 

River-Data on roadfill erosion or total road prism 

erosion were used to develop a negative exponential 

equation showing surface erosion on severely disturbed granitic soils over time. By far the greatest 

percentage of erosion occurs in the first and second 

years after construction (p. 12). In the first year, 

erosion rates are about 1,000 times greater than on 

undisturbed lands, where rates average 0.07 tons per 

square mile per day (p. 12). Additional disturbances 

(such as road grading) result in new cycles of surface 

erosion (p. 13). 

Burroughs and others 1983a, Silver Creek Study 

Area, Boise National Forest-Simulated rainfall was 

applied to six road sections representing three different roadway surfaces on a new road. Runoff, sediment, 

and other variables were measured. Sediment yield 

was directly correlated with the amount ofloose soil on 

the surface, and inversely correlated with the average 

size of the loose soil (p. 10). See Burroughs and King 

(1985) for analysis of the relative effectiveness of dust 

oil, gravel, and bituminous surfacing. 

Burroughs and others 1983b, Rainy Day Road, Nez 

Perce National Forest-Simulated rainfall was applied repeatedly to new road prism surfaces (cut, 

tread, and ditch). Initial sediment yields on theunprotected surfaces were high but declined rapidly (p. 9). 

Sediment yields increased 108 percent when the 

unsurfaced road tread was ruttedrather thanunrutted; 

these yields also decreased rapidly with successive 

applications (p. 16). However, the authors noted that 

the rapid armoring that occurred on these study plots 

might not have occurred if traffic had been present 

(P. 22). 

The relative effectiveness of rocked road surfaces 

and ditches was also tested. For ditches, the ratio of 

sediment yields (p. 14) was: 

(Unrocked ditch + untreated cutslope) : 

(Rocked ditch + untreated cutslope) = 2.29. 

Inclusion of the cutslope sediment in the measurement inasked the effectiveness of the rocked ditch 

(p. 1). A travelway with gravel surfacing producedonly 

23 percent of the sediment yield of an unsurfaced 

travelway (p. 1). 

Burroughs and King 1985, Silver Creek Study Area, 

Boise National Forest-This study includes results of 

the final analysis of the study reported in Burroughs 

and others (1983a). In that study, simulated rainfall 

was applied to six road sections representing three 

different roadway surfaces on a new road. Runoff, 

sediment, and other variables were measured. Sediment yields from dust oil surfaces were about 13 

percent of the yield from the native surfaces at the 

same gradient; yields from bituminous surfaces were 

about 1.1 percent of those from native surfaces (p. 187). 

Vincent 1985, Silver Creek Study Area, Boise National Forest-Runoff and sedimentation were measured during snowmelt and rainstorms on three sections of native roadway surface varying in gradient 

from 6.3 to 13.4 percent. The road was constructed in 

1980, extensively eroded before the first measurements in 1981, and regraded before the 1982 measurements (pp. 7-9); it was closed to traffic throughout the 

study period. The road was less erodible in the eroded 

condition than in the regraded condition; a given 

amount of runoff generated 75 to 80 percent less 

sediment for the eroded road in 1981 than for the 

regraded road in 1982 (p. 39). This is a reversal of the 

usual time trend, in which lower sediment yields 

would be expected 2 years construction. 

Megahan 1988, various sites, literature review-For 

the Interior West, long-term accelerated erosion tends 

to continue on roads in direct proportion to traffic use 

and in inverse proportion to the level of road maintenance (p. 341). 

Burroughs and King 1989, various sites, literature 

review-Dust oil surfaces break down under heavy 

tr&c and also contribute volatile chemicals to surface runoff (p. 2). No information was found on sediment reduction by lime or magnesium chloride (p. 2). 

Foltz and Burroughs 1990, Tin Cup Creek, Caribou 

National Forest, east ofIdaho Falls-Three 30-minute 

applications of simulated rainfall were applied to 

paired roadway surface plots, one rutted and one 

unrutted. There was a thin layer of loose material over 

a compacted, bladed road surface (p. 272); gradients of 

the plots were 8.4 and 9.0 percent (p. 269). Sediment 

production from the rutted plots decreased sharply 

over time after the first 20 minutes, reflecting a limited supply ofmaterial for transport (p. 272). Sediment 

production from the unrutted plots rose for about the 

first 30 minutes, but then maintained a more level 

sediment production with a slight decline at about 45 

minutes. 

The sediment levels from the rutted plot were consistently higher than those from the unrutted plot, 
peaking at 90 grams per second, compared to 32 grams 

per second for the unrutted plot (p. 272). When the 

data were adjusted to account for the relative proportions of rutted andunrutted surface onaroad with two 

ruts, the sediment productionratios (tworuts: noruts) 

were 2.1 (dry conditions), 1.2 (wet conditions), and 1.0 

(very wet conditions) for the three applications of 

simulated rainfall (pp. 273-274). The authors recommended road closures and similar measures to prevent rutting during wet weather (p. 275). 

BMP 167-Rule 4.d.iii.(c). Maintain the road surface as necessary to provide proper drainage (active 

roads). 

Packer and Christensen 1964,720 sites in Idaho and 

Montana, representing six soil groups-Previous research had indicated that secondary logging road 

surfaces deteriorate rapidly when rill depths exceed 

1 inch (p. 2). Based on the research later reported in 

Packer (1967), the authors suggestedcross drainspacings to prevent 83 percent of the cases of 1-inch rill 

formation. A table (pp. 13-15) gives recommended 

spacings by road grade and soil type, with adjustments 

for topographic position, aspect, slope steepness, and 

the percent of cases in which 1-inch rill formation is 

prevented. 

Paclzer 1967,720 sites in Idaho and Montana, representing six soil groups-This publication explains the 

theoreticd basis, research design, and data analysis 

that led to the field guide of Packer and Christensen 

(1964). Fourteen road and watershed variables were 

tested as predictors of surface water flow distance 

producing 1-inch rib. The most important variable 

was the proportion of soil particles and water-stable 

aggregates larger than 2 rnm on the road surface. 

Although this property is related to the soil group, the 

benefits of larger particles can be derived on all soil 

types by surfacing roads with gravel or crushed rock 

(pp. 8-9). The multiple regression equation developed 

from the most important predictive variables was 

used to make a table (p. ll), which is the same as the 

table in Packer and Christensen (1964, pp. 13-15). 

Arnold and Lundeen 1968, South Fork Salmon River 

drainage-A survey of road erosion on the roads producing the most sediment in the drainage found that 

65 percent of sediment originated from fillslopes, 10 

percent from cutslopes and ditches, 21 percent from 

maintenance wasting of cutslope material, and 4 percent from road surfaces (p. 117). 

Hartsog and Gonsior 1973, South Fork Salmon 

River drainage, Payette National Forest-During the 

construction period and the early period of use, an 

engineering research team evaluated a road designed 

to minimize watershed impacts. The road had been 

designed as an outsloped road, but did not function as 

one because of trenches left by skidding tractors and 

skidded logs, and because of berms lea along the road's 

edge during grading (p. 13). The authors felt that 

outsloping would seldom function as designed due to 

concentrations of water caused by wheel depressions 

and slight differences in soil properties. They recommend outsloping only where surfaces are "relatively 

nonerodible" such as full-bench sections (p. 20). 

They further note that insloping can result in considerable sediment movement unless cutslopes and 

ditches are stabilized. They suggest that roads should 

be designed, graded, and surfaced to carry water along 

the tread, and that provisions should be made to filter 

or settle out sediment before road runoff reaches 

streams (p. 21). 

Burroughs and others 1983b, Rainy Day Road, Nez 

Perce National Forest--Simulated rainfall was applied repeatedly to new road prism surfaces (cut, 

tread, and ditch). Initial sediment yields on the unprotected surfaces were high but declined rapidly (p. 9). 

Sediment yields increased 108 percent when the 

unsurfaced road tread was ruttedrather thanunrutted; 

these yields decreased rapidly with successive applications (p. 16). The rapid armoring that occurred on 

these study plots might not have occurrediftrailic had 

been present (p. 22). 

Megahan and others 1983, Silver Creek Study Area, 

Boise National Forest-Long-term (45-year) cutslope 

erosion was estimated using exposed tree roots. The 

authors noted that road maintenance is the primary 

cause of long-term accelerated cutslope erosion. Removal of slough material at the base of the roadcut 

during maintenance operations interferes with the 

natural slope-forming process, removes a favorable 

site for vegetation growth, and rejuvenates slope erosion processes. The authors suggested that removal of 

the material deposited at the base of the roadcut 

should be avoided or minimized whenever possible, on 

forest roads used infrequently, for instance (p. 28). 

Burroughs and King 1989, various sites, literature 

review-Ditch maintenance often undercuts the 

cutslope and reinitiates cutslope erosion processes 

(pp. 12-13). 

The authors summarize two studies showing the 

influence of drainage from the road surface onto the fill 

(Carlton and others 1982; Tennyson and others 1981). 

In the Horse Creek Study Area (Nez Perce National 

Forest), the average transport distances of sediment 

flows below fillslopes were more than twice as great if 

they were influenced by travelway drainage (58.8 feet 

compared to 25.8 feet). These figures are for sediment 

flows that are not associated with windrows, culverts, 

or slumps (p. 9), for 2 years after road construction. In 
the Gospel Hump management areas, transport distances below fills were generally greater for sediment 

flows influenced by travelway drainage (p. 9). 

Foltz and Burroughs 1990, Tin Cup Creek, Caribou 

National Forest, east ofIdaho Falls-Three 30-minute 

applications of simulated rainfall were applied to 

paired roadway surface plots, one rutted and one 

unrutted. There was a thin layer ofloose material over 

a compacted, bladed road surface (p. 272); gradients of 

the plots were 8.4 and 9.0 percent (p. 269). Sediment 

production from the rutted plots decreased sharply 

over time aRer the first 20 minutes, reflecting a limited supply ofmaterial for transport (p. 272). Sediment 

production from the unrutted plots rose for about the 

first 30 minutes, but then maintained a more level 

sediment production with a slight decline at about 45 

minutes. 

The sediment levels from the rutted plot were consistently higher than those fiom the unrutted plot, 

peaking at 90 grams per second, compared to 32 grams 

per second for the unrutted plot (p. 272). When the 

data were adjusted to account for the relative proportions of rutted and unrutted surface on a road with two 

ruts, the sediment production ratios (tworuts: no ruts) 

were 2.1 (dry conditions), 1.2 (wet conditions), and 1.0 

(very wet conditions) for the three applications of 

simulated rainfall (pp. 273-274). The authors recommended road closures and similar measures to prevent rutting during wet weather (p. 275). 

BMP 168-Rule 4.d.iii.(d). If road oil is used, apply 

it in such a manner as to prevent its entry into streams 

(active roads). 

Megahan 1988, various sites, literature review-The 

author was unable to find any literature documenting 

changes in water quality due to chemicals usedin road 

maintenance (p. 338). 

Burroughs and King 1989, various sites, literature 

review-Dust oil surfaces break down under heavy 

trac and also contribute volatile chemicals to surface runoff (p. 2). 

BMP 169--Rule 4.d.iii.(d). If other surface-stabiIizing materials are used, apply them in such a manner 

as to prevent their entry into streams (active roads). 

Megahan 1988, various sites, literature review-The 

author was unable to find any literature documenting 

changes in water quality due to chemicals usedin road 

maintenance (p. 338). 

Burroughs and King 1989, various sites, literature 

review-Noinformation was found onsediment reduction by lime or magnesium chloride (p. 2). 

BMP 170-Rule 4.d.iv.(a). Following termination of 

active use, clear ditches (inactive roads). 

See Rule 4.d.iii.(a). , functional ditches (active roads) 

(BMP 160). 

BMP 171-Rule 4.d.iv.(a). Following termination of 

active use, clear culverts (inactive roads). 

No references were found. 

BMP 172-Rule 4.d.iv.(a). Following termination of 

active use, crown the road surface (inactive roads) 

(first alternative). 

No references were found. 

BMP 173-Rule 4.d.iv.(a). Following termination of 

active use, outslope the road surface (inactive roads) 

(second alternative). 

BMP l7ARule 4.d.iv.(a). Following termination of 

active use, inslope the road surface (inactive roads) 

(tthird alternative). 

See Rule 4.b.iv., outsloping and insloping rules 

(BMP's 97 and 98). 

BMP 175-Rule 4.d.iv.(a). Following termination of 

active use, water bar the road surface (inactive roads) 

(fourth alternative). 

See Rule 4.b.iv., dips, water bars, and cross drains 

(BMP's 100 through 102). 

BMP 176-Rule 4.d.iv.(a). Following termination of 

active use, otherwise leave the road surface in a 

condition to minimize erosion (inactive roads) (fifth 

alternative). 

No references were found; see Rule 4.c.iii., stabilization of exposedmaterial (BMP's 117 through 1221, and 

the General Erosion Research Summary for additional information. 

BMP 177-Rde 4.d.iv.(a). Following termination of 

active use, continue maintenance of drainage structures as needed (inactive roads). 

See Rule 4.d.iii.(a)., functional culverts and ditches 

(active roads) (BMP's 159 and 160). 

BMP 17PRule 4.d.iv.(b). Roads may be permanently blocked to vehicular traftic (inactive roads). 

Clifton and Megahan 1988, South Fork Salmon 

River drainage, Payette an& Boise National ForestsClosed roads wereinventoried to evaluate surface and 

mass erosion conditions (p. 1). "Intensive surveys" 

were conducted on 12.3 miles of road in two watersheds, representing three landtypes (p. 1). Erosion 

classes were used for surface erosion ratings (1 = 

natural, 2 = very low, 3 = low, 4 = moderate, and 5 = 

high) (p. 2). Roads with light use (foot, horse, or 

motorcycle) showed greater average surface erosion 

than those with no use (p. 4). 

Megahan 1988, various sites, literature reuiewSurface erosion rates tend to be directly proportional 

to the level of traffic (p. 341). 
See Rule 4.d.iv.(b)., seasonal blockage (inactive roads) 

(BMP 179). 

BMP 179-Rule 4.d.iv.(b). Roads may be seasonally 

blocked to vehicular traffic (inactive roads). 

Burroughs and others 1983b, Rainy Day Road, Nez 

Perce National Forest-Simulated rainfall was applied repeatedly to new road prism surfaces (cut, 

tread, and ditch). Initial sediment yields on the unprotected surfaces were high but declined rapidly (p. 9). 

Sediment yields increased 108 percent when the 

unsurfaced road tread was ruttedrather thanunrutted; 

these yields also decreased rapidly with successive 

applications (p. 16). The rapid armoring that occurred 

on these study plots might not have occurred if trac 

had been present (p. 22). 

Megahan 1988, literature review, various sitesSurface erosion rates tend to be directly proportional 

to the level of traffic (p. 341). 

Foltz and Burroughs 1990, Tin Cup Creek, Caribou 

National Forest, east ofIdaho Falls-Three 30-minute 

applications of simulated rainfall were applied to 

paired roadway surface plots, one rutted and one 

unrutted.\There was a thin layer of loose material over 

a compacted, bladed road surface (p. 272); gradients of 

the plots were 8.4 and 9.0 percent (p. 269). Sediment 

production from the rutted plots decreased sharply 

over time after the first 20 minutes, reflecting a limited supply of material for transport (p. 272). Sediment 

production from the unrutted plots rose for about the 

first 30 minutes, but then maintained a more level 

sediment production with a slight decline at about 45 

minutes. 

The sediment levels from the rutted plot were consistently higher than those from the unrutted plot, 

peaking at 90 grams per second, compared to 32 grams 

per second for the unrutted plot (p. 272). When the 

data were adjusted to account for the relative proportions of rutted and unrutted surface on a road with two 

ruts, the sediment production ratios (two ruts: no ruts) 

were 2.1 (dry conditions), 1.2 (wet conditions), and 1.0 

(very wet conditions) for the three applications of 

simulated rainfall (pp. 273-274). The authors recommended road closures and similar measures to prevent rutting during wet weather (p. 275). 

BMJ? 180-Rule 4.d.v.(a). Leave the road in a condition suitable to control erosion by outsloping 

(abandoned roads) (first alternative). 

See Rule 4.b.iv., outsloping and insloping rules 

(BMP's 97 and 98). 

BMP 181-Rule 4.d.v.(a). Leave the road in a condition suitable to control erosion by water barring (abandoned roads) (second alternative). 

See Rule 4.b.iv., dips, water bars, and cross drains 

(BMP's 100 through 102). 

BMP 182--Rule 4.d.v.(a). Leave the road in a condition suitable to control erosion by seeding (abandoned 

roads) (third alternative). 

Haupt and Kidd 1965, Boise Basin Experimental 

Forest, Boise National Forest-Erosion associatedwith 

logging and logging road construction was reduced by 

use of "good logging practices" including seeding, harrowing, and cross draining of roads following logging 

in 1953 and 1954 (p. 665). By 1958, the perennial 

grasses that had been seeded on the roadways were 

well established and erosion was negligible during the 

most intense storm (2.82 inches of rain per hour for 10 

minutes) of the 7-year study period (p. 668). 

Megahan and Kidd 1972a, b, Zena Creek Study Area, 

Payette National Forest-The authors studied erosion 

and sedimentation from logging and road construction. Roads built in October 1961 were seeded and 

water barred after logging was completed in November 1962. The average sedimentation rate in ephemeral drainages below roads for 4.8 years after logging 

was 51.0 tons per square mile per day. No data were 

collected for comparison on roads that were not seeded 

or water barred. Sedimentation rates on nearby undisturbed watersheds averaged 0.07 tons per square mile 

per day. A return to predisturbance levels of erosion 

was not expected due to continued roadcut and tread 

erosion. 

Clifton and Megahan 1988, South Fork Salmon 

River drainage, Payette and Boise National ForestsClosed roads were inventoriedto evaluate surface and 

mass erosion conditions (p. 1). "Intensive surveys" 

were conducted on 12.3 miles of road in two watersheds, representing three landtypes. "Extensive surveys" were conducted on 63.2 miles of road in four 

watersheds, representing 14 landtypes (p. 1). The following results are from the intensive survey data. 

Erosion classes wereused for surface erosion ratings 

(1 = natural, 2 = very low, 3 = low, 4 = moderate, and 

5 = high) (p. 2). Average values for roadfills and road 

tread were each slightly less than 2, while the average 

value for roadcuts was 2.6 (p. 3). On all road prism 

components (roadcut, road tread, and roadfill), correlation analyses showed that as ground cover densities 

increased, surface erosion decreased. Roadcuts were 

most sensitive to changes in cover density (p. 5). Ground 

cover included litter and rocks as well as vegetative 

cover. 

Multiple regression analyses also were conducted 

for each component of the road prism. Of 19 variables 

tested, the roadcut cover density and bedrock weathering class explained 86 percent of the variance in 

roadcut surface erosion (p. 6). Of 40 variables tested, 

the roadfill cover density explained 69 percent of the 

variance in roadfill surface erosion (p. 7). Of 25 variables tested, the percent road tread cover outside 
wheel tracks explained 53 percent of the variance in 

road tread surface erosion (p. 6). 

Because cutslopes exhibited the greatest erosion 

and were more sensitive to changes in cover, the 

authors recommended that cutslope revegetation be 

given priority for rehabilitation measures (p. 6). Average cover densities were much lower on cutslopes (23 

percent for head and 38 percent for toe) than on road 

treads (67 percent) and fills (74 percent) (p. 3). 

See Clifton and Thompson (1989) for a followup 

study. 

Clifton and Thompson 1989, South Fork Salmon 

River drainage, Payette and Boise National ForestsSurface and mass erosion were evaluated on 13 closed 

logging roads about 20 years after road closure (p. 3). 

Seven landtypes were represented in the four drainages studied (p. 3). 

Erosion classes were used for surface erosion ratings 

(1 = natural, 2 = very low, 3 = low, 4 = moderate, and 

5 = high). Overall, surface erosion rates were in the 1 

to 2 range; roadcuts had slightly higher erosion (p. 3). 

Regression analysis showed that 73 percent of the 

variation in surface erosion (for cut, tread, and fdl 

combined) was explained by the cover density variable 

(p. 4). Ground cover included litter and rocks, as well 

as vegetative cover. Average cover densities were 85 

percent on roadcuts, 90 percent on road tread, and 91 

percent on roadfills (p. 13). 

See Rule 4.c.iii., stabilization of exposedmaterial by 

seeding (BMP 117), and the General Erosion Research 

Summary for additional information. 

BMP 183--Rule 4.d.v.(a). Leave the road in a condition suitable to control erosion by other suitable methods (abandoned roads) (fourth alternative). 

Haupt and Kidd 1965, Boise Basin Experimental 

Forest, Boise National Forest-Erosion associatedwith 

logging and logging road construction was reduced by 

use of "good logging practices" including seeding, harrowing, and cross draining of roads following logging 

in 1953 and 1954 (p. 665). By 1958, the perennial 

grasses that had been seeded on the roadways were 

well established; erosion was negligible during the 

most intense storm (2.82 inches ofrain per hour for 10 

minutes) of the 7-year study period (p. 668). 

Megahan and Kidd 1972a, b, Zena Creek Study Area, 

Payette National Forest-Erosion and sedimentation 

from logging and road construction was studied. Roads 

built in October 1961 were seeded and water barred 

after logging was completed in November 1962. The 

average sedimentation rate in ephemeral drainages 

below roads for 4.8 years after logging was 51.0 tons 

per square mile per day. No data were collected for 

comparison on roads that were not seeded or water 

barred. Sedimentation rates on nearby undisturbed 

watersheds averaged 0.07 tons per square mile per 

day. A return to predisturbance levels of erosion was 

not expected due to continued roadcut and tread 

erosion. 

See Rule 4.c.iii., stabilization of exposed material 

(BMP's 117 through 122) and the General Erosion 

Research Summary for additional information. 

BMP 184-RuleC.d.v.(b). Cleanditches (abandoned 

roads). 

See Rule 4.d.iii.(a)., functional ditches-active roads 

(BMP 160). 

BMP 185-Rule 4.d.v.(c). Block the road to vehicular traffic (abandoned roads). 

See Rule 4.d.iv.(b)., seasonal and permanent road 

blocks-inactive roads (BMP's 178 and 179). 

BMP 186-Rule 4.d.v.(d). Remove bridges if required by the department (abandoned roads). 

No references were found. 

BMP 187-Rule 4.d.v.(d). Remove culverts if required by the department (abzindoned roads) (first 

alternative). 

Jensen and Finn 1966, Zena Creek Study Area, 

PayetteNational Forest-In the Deep Creek drainage, 

road rehabilitation efforts were made on 8.47 miles of 

road in 1965. Rehabilitation efforts consisted of digging channels across the road to reopen ephemeral 

drainages, constructing dips every 100 feet, and removing all culverts and fill material in draws (p. 87). 

The roadway was seeded to perennial grasses (p. 90). 

The authors recommended using the same techniques 

in future rehabilitation efforts on decomposed granitic 

landtypes, using a dragline (if possible without major 

reconstruction) and a D-7 or D-8 tractor. The authors 

noted, however, that even with such efforts, it would 

be impossible to stop most of the accelerated sedimentation or to restore the natural hydrologic function 

that had been altered by roadcuts (p. 91). 

Clifton and Thompson 1989, South Fork Salmon 

River drainage, Payette and Boise National ForestsSurface and mass erosion were evaluated on 13 closed 

logging roads about 20 years after road closure (p. 3). 

Seven landtypes were represented in the four drainages studied (p. 3). 

Problem sites with potential for sediment delivery to 

streams were identified and assignedvalues for potential delivery to streams (1 = no potential through 9 = 

supplied directly to watercourse) and priority for treatment (1 = high priority through 9 = low priority). The 

five types of problem sites, in order of decreasing 

frequency, were: culverts with fill intact, road gullies, 

washouts, various diversion problems, and plugged 

culverts (p. 17). 

Culverts with fdl intact, the most common problem 

site (28 percent oftotal), were of two types: log culverts 

and pipe culverts. Log culverts each stored an 
estimated 23 to 26 cubic yards of sediment that would 

be released slowly over time as the logs rotted. Removal would be difficult due to heavy vegetative cover 

on the culverts (spruce, alders, mosses) and difficult 

access. The average sediment delivery potential rating was 9; the problem priority rating was 4.7. Pipe 

culverts stored about 6 to 8 cubic yards of sediment 

that would be released when the culverts failed. Average sediment delivery potential rating for pipe culverts was 6.1; the priority rating was 4.8 (p. 17). 

Culverts plugged with debris were the least frequent problem sites. At these sites, seasonally active 

watercourses were being rerouted across the road. The 

average sediment delivery potential rating was 5.2; 

the problem priority was 5.2 (p. 17). 

BMP 188-Rule 4.d.v.(d). Maintain drainage structures as needed (abandoned roads) (second alternative). 

See the summary of Clifton and Thompson (1989) 

under the previous rule (BMP 187). 
General Erosion 

Research Summary 
General Erosion 

Research Summary 

The research studies summarized in this section 

have implications for one or more of the best management practices, but may not address any particular 

best management practice directly. Parts of the information presented here, or other information from the 

same reference, may also appear under specific best 

management practices. As in previous sections of this 

report, references are listed chronologically (alphabetically within the same year). 

Jensen and Finn 1966, Zena Creek Logging Study 

Area, Payette National Forest-A hydrologic analysis 

of the study area (13,334 acres) evaluated watershed 

conditions and made recommendations (pp. 1,2). Five 

landtypes were present; the streamcut, decomposed 

granitic landtype was most susceptible to erosion and 

sedimentation problems. Management recommendations, some specific to particular landtypes, are given 

(pp. 7-91. 

Average yearly surface erosion from cut, tread and 

ditch, and fill were given for four landtypes: strongly 

glaciated granitic soils, periglacial granitic soils, river 

terrace lands, and decomposed granitic soils. For 

strongly glaciated granitic soils and river terrace lands, 

the values for all road prism components were 0.1 inch 

of surface erosion per year. For periglacial granitic 

soils, the roadcut value was 0.2 inch of surface erosion 

per year and the tread and ditch and fill values were 

0.1 inch. For the decomposed granitic soils, the roadcut 

value was 1.0 inch of surface erosion per year, the 

tread and ditch value was 0.1 inch, and the fill value 

was 0.5 inch (p. 70). 

Bethlahmy 1967, Zena Creek Logging Study Area, 

Payette National Forest-Erosion from high-intensity 

simulated rainfall (12.2 centimeters per hour for 30 

minutes) on areas logged with group selection (with 

slashlopped and scattered) and onunlogged areas was 

a logarithmic function of runoff (p. 3). A small increase 

in runoff can cause a large increase in erosion (p. 6). 

Runoff was directly related to the amount of bare soil, 

that was much greater on southwest aspects (averaging 41.9 percent bare soil) than on northeast aspects 

(averaging 2.7 percent bare soil) (p. 4). Significantly 

greater erosion occurred on southwest aspects. Logged 

plots had significantly greater erosion than unlogged 

plots for the southwest aspect, but not for the northeast aspect (p. 5). 

Meeuwig 1970, seven sites in the Intermountain 

area, including two forested sites in Idaho: Basalt 

Range north of Seven Devils, Nez Perce National Forest; Trinity Mountains, Boise National ForestEight independent variables were used in a multiple 

regression equation to predict erosion resulting from 

simulated high-intensity rainfall (5 inches per hour 

for 30 minutes): 

Logarithm of ovendry weight of eroded soil and 

organic matter 

Versus 

A. Proportion of soil surface protected by vegetation 

and litter 

B. Proportion of soil surface protected by vegetation, litter, and stone 

D. Sand content of surface inch of soil 

E. Organic matter of surface inch of soil 

F. Organic matter of surface 2 inches of soil 

G. Slope gradient 

H. Bulk density of surface 4 inches of soil 

L. Air-dry weight of litter. 

Ofthe eight independent variables, protection ofthe 

soil surface from direct raindrop impact (A or B) was 

the most important variable in reducing erosion (p. 5). 

Gradient was also important, especially on sandy soils 

(p. 5). Organic matter increased the erodibility of 

sandy soils, including those on the two Idaho sites 

(p. 6). 

Various equations, graphs, tables, and nomographs 

show relationships among the variables and predict 

sheet erosion rates from storms similar to the experimental storm. 

See Meeuwig (1971) for a followup report. 

Farmer and Van Haveren 1971, laboratory study 

using soils from three Intermountain sites, including 

high- and low-elevation sites in the Boise National 

Forest-A laboratory experiment evaluated the erodibility of bare Intermountain area soils subjected to 

simulated rainfall. Three slope gradients were tested 

(2.5,18, and 32 percent); two rainfall intensities (about 

3 or 7 inches per hour) were applied for 30 minutes to 

saturated soils (p. 2). Erosion by overland flow and by 

soil splash were evaluated separately. 

A graph displayed the interactions among intensity, 

gradient, and particle size in determining erosion by 

overland flow (p. 4). Erosion was minimal if either 

steepness or intensity was low, but increased more 

than five times when both steepness and intensity 

were at their maximum values (p. 5). Larger particle 

sizes had lower erosion rates (p. 5). The soil variables 

tested were much less important than slope gradient 

or rainfall intensity (p. 5). Slope gradient and rainfall 

intensity accounted for 90 percent of the variance in 

the data, particle size accounted for just 6 percent (p. 5). 

For splash erosion, gradient and intensity accounted 

for 82 percent of the variance, while bulk density and 

the proportion of sand-size material accounted for 15 

percent (p. 7). Interactions were shown in figures 

(p. 7). Splash erosion increased as bulk density increased; most forest and rangeland soils have a seasonal 

increase in bulk density from spring to fall (p. 13). 
The high-elevation granitic soil was the least erodible of the three soils tested. The other two soils were 

similar in their erodibility (p. 11). In all cases, bare 

soils demonstrated little resistance to erosion. Severe 

erosion during high-intensity rains can be expected on 

areas with little vegetative cover (p. 13). 

Gonsior and Gardner 1971, Zena Creek drainage, 

Payette National Forest-The authors investigated 

mass failures to determine their causes and to recommend measures to prevent future failures. Field and 

laboratory measurements and a slope stability analysis were done. Contributing factors included: natural 

instability of the area, logging and road construction 

activities, steepness of roadcut and fillslopes, poor 

road drainage, lack of fill compaction, inclusion oflogs 

and stumps in fill material, and removal of trees near 

roads (pp. 30-32). Recommendations for future road 

construction methods are given (p. 33). Most of these 

are discussed under the corresponding best rnanagement practices. 

Meeuwig 1971, seven sites in the Intermountain 

area, including two forested sites in Idaho-This publication used the same data as Meeuwig (1970), but 

data from all sites were combined for this analysis 

rather than analyzed separately. A regression analysis was performed for the combined data set from the 

seven sites 

Common logarithm of the weight of material eroded 

during 30 minutes of simulated high-intensity rain 

Versus 

Percent surface cover (plants and litter) 

Litter weight 

Slope gradient 

Percent clay in surface inch of soil 

Percent sand in surface inch of soil 

Percent organic matter in surface inch of soil. 

As in the 1970 study, surface cover was the most 

important predictor variable. Cover had alarger effect 

as slope steepness increased, and slope had a larger 

effect as cover values decreased. When cover was less 

than 50 percent, erosion rates doubled for each 10 

percent increase in slope (p. 6). Erosion as a function 

of cover and slope was graphed (p. 6). 

Interactions (with respect to relative erodibility) 

between contents of sand, clay, and organic matter 

were shown (p. 8). The most erodible soils had high 

clay, low sand, and low organic matter (p. 9). Three 

combinations exhibiting low erodibility were (p. 9): 

(1) high clay, low sand, and high organic matter; 

(2) low clay, high sand, and low organic matter; 

(3) low clay, low sand, and any organic matter 

content. 

Burroughs and others 1972, near Lolo Pass at the 

Ihho-Montana border-In the zone of deepest snowpacks, substantial volumes of water were intercepted 

during snowmelt (p. 11) at roadcuts averaging 36 

inches high (p. 3). Subsurface seepage averaged 58 

percent of the total water intercepted during snowmelt; the remainder occurred as overland flow (p: 10). 

In the central Idaho Batholith, such overland flow 

fiom snowmelt is seldom observed(p. 12). See Megahan 

(1972) for a similar study in the Idaho Batholith. The 

factors identified as conducive to overland flow during 

snowmelt were (p. 11): 

A deep snowpack 

Snowmelt delayed until June due to elevation and 

aspect, then rapid snowmelt 

Moderate slope gradients 

A completely saturated soil mantle or a high water 

table. 

The study indicated that 1 mile of road in the deep 

snowpack zone would intercept 310 acre-feet of overland flow and subsurface seepage during the spring 

snowmelt period. Providing drainage for the intercepted water is critical, especially in areas to be logged 

with jammers, because densities of jammer roads 

often exceed 10 linear miles per square mile (p. 11). 

Special measures are also necessary for the prevention of cut and fill erosion (p. 11). 

Clayton and Arnold 1972, Idaho Batholith-A classification system for Batholith rocks was presented 

(pp. 7-8). Management implications ofthe stability properties of each weathering class are given (pp. 16-17). 

Megahan 1972, Pine Creek Study Area, Boise National Forest--Subsurface flow interception was measured along roadcuts deep enough to expose bedrock 

(average soil depth was about 31 inches) in first order 

watersheds (p. 351). Subsurface flow was intercepted 

only during the spring snowmelt period; overland flow 

was never observed (p. 353). The volume of flow intercepted was about 7.3 times greater than the estimated 

snowmelt runoff from the road area alone (p. 355). 

About 35 percent of the total subsurface flow was 

intercepted by the roadcut (p. 355). Subsurface flow 

interception was greater in drainage bottoms, but was 

not limited to those areas (p. 353). The author notes 

that this large volume of runoff must be considered in 

road drainage design, drainage structures, and erosion control measures, as we11 as the potential effects 

on channels and vegetation (p. 356). 

See Burroughs, Marsden, and Haupt (1972) for a 

related study. 

Megahan and Kidd 1972~~ b, Zena Creek StudyAreaa 

Payette National Forest-Erosion and sedimentation 

from logging and road construction were studied. 
Roads built in October 1961 were seeded and water 

barred after logging was completedinNovember 1962. 

Sediment was measured in ephemeral drainages below roads. The average road sedimentation rate for 

1.35 years before logging was 56.2 tons per square mile 

per day. The average road sedimentation rate for 4.8 

years after logging was 51.0 tons per square mile per 

day. These rates include sediment from both surface 

and mass erosion. Sedimentation rates on nearby 

undisturbed watersheds averaged0.07 tons per square 

mile per day. Roads increased sedimentation 770 

times over the natural rate; of this, 30 percent was 

from surface erosion and 70 percent was from mass 

erosion. Jammer and skyline logging increased sedimentation 0.6 times. 

Time trends for sediment from surface erosion on 

logging roads were discussed and shown in tabular 

and graphical form (Megahan and Kidd 1972a, pp. 8-9). 

In the first measurement period (November 1961 to 

June 1962), rates of sedimentation due to surface 

erosion were 109 tons per square mile per day, 1,560 

times the undisturbed rate. The rates decreased rapidly in subsequent measurement periods, then fluctuated from 0 to 100 times the natural rate. High initial 

sedimentation rates were largely due to fillslope erosion; but these high rates could be avoided by fill 

stabilization. Continued acceleratedroad erosion rates 

were expected due to erosion of weathered granitic 

bedrock on the road tread and steep road cutslopes. 

Mass erosion does not follow time trends in the same 

manner as surface erosion. It depends more on climatic events and the consideration given to road 

location, design, construction, and maintenance. 

Megahan 1974b, four sites in the Idaho Batholith: 

Deep Creek, Silver Creek, Bogus Basin, Deadwood 

River-Data on roadfill erosion or total road prism 

erosion were used to develop a negative exponential 

equation describing surface erosion on severely disturbed granitic soils over time. By far the greatest 

percentage of erosion occurs in the first and second 

years after construction (p. 12). In the first year, 

erosion rates are about 1,000 times greater than on 

undisturbed lands, where rates average just 0.07 tons 

per square mile per day (p. 12). After 40 years, erosion 

rates are about 10 times greater than on undisturbed 

lands (p. 12). Additional disturbances result in new 

cycles of surface erosion (p. 13). 

Erosion control measures are most effective if applied immediately after disturbance (p. 12). Seeding 

was not recommended because of the erosion that 

occurs before the seeded vegetation becomes established; mulching or transplants were recommended 

for immediate erosion control (p. 12). 

Burroughs and Thomas 1977, South Fork Payette 

River near Lowman, Boise National Forest- Rocky 

Mountain Douglas-fir root numbers and tensile 

strength over time were measured on clearcut and 

undisturbed slopes. All sampling areas were within 

old-growth sites (100 to 200-year-old trees). Tensile 

strength of tree roots was shown to be an important 

factor increasing slope stability onlogged andunlogged 

slopes. However, root strength decreases rapidly in 

the first year after tree felling, and then decreases 

gradually over time (p. 16). 

Day and Megahan 1977, Clearwater National Forest-Based on a survey of 629 landslides, this report 

gives seven criteria for identifying unstable slopes: 

Steep slopes (generally >60 percent) 

Highly weathered and fractured bedrock; bedrock 

with high mica or clay content (generally border 

zone rocks) 

Areas that show a concentration of subsurface 

water 

Adverse structure (planes of bedrock weakness 

dip with the slope of the land) 

Impermeable zones within the mantle or bedrock 

A history of landslides (p. 12). 

Megahan 1978, Deadwood River Road, Boise National Forest-Fillslope plot studies were used to evaluate surface erosion processes on bare plots and 

mulched plots planted with ponderosa pine seedlings (p. 351). The roacEll was 11 years old when the 

plots were installed, had a southwest aspect, and a 

gradient of 70 to 75 percent (p. 350). 

Three water years (October 1 through September 

30) of data were available to test seasonal differences 

(p. 351). Mean daily erosion was significantly greater 

during the summer-fall period than during the portions of the winter-spring period without surface snow 

cover (pp. 351-352). About 80 percent ofthe total erosion 

occurred during the summer-fall period (p. 356). 

Planted trees significantly reduced (45 percent, significant at the 0.05 level) erosion during the summerfall periods, but not during the winter-spring periods 

(20 percent, not significant) (p. 352). During the summer-fall periods, plots with planted trees had significantly less (0.01 level) erosion than the control plots 

for periods with and without rain (p. 353). Tree planting reduced estimated dry creep erosion (relative to 

the control) from 1.9 to 1.2 metric tons per square 

kilometer per day during rainy periods, and from 2.6 

to 1.4 metric tons per square kilometer per day during 

raidkee periods (p. 355). 

Dry creep accounted for 15 to 52 percent of the total 

summer-fall erosion. Wind was an important cause of 
dry creep, and also increased erosion during rainstorms by about 10 times (p. 357). The erodibility 

index explained only 25 percent of the variation in 

erosion (p. 354). 

Megahan and others 1979, CZearwaterNational Forest and Middle Fork Payette River drainage, Boise 

National Forest-The authors directed an inventory 

of 1,418 landslides of 8 cubic meters or more (pp. 120, 

121) in the two study areas. The data only give frequencies of occurrence; they do not define cause and 

effect (p. 137). 

The average slide volume was 460 cubic meters; on 

average, about 19 percent or 87 cubic meters was 

delivered to streams (p. 121). The Cle-ter National Forest had an average of 210 new slides per year 

during the 3-year study; however, 1 year of the three 

probably had greater than average slide frequency due 

to climatic events (p. 210). Climatic conditions had 

effects on both slide frequency and slide characteristics (pp. 128-129). Seventy-two percent of slides were 

debris slides or debris avalanches; 19 percent were 

slumps; 7 percent were debris flows or debris torrents; 

2 percent were rockfalls (p. 122). 

On the Clearwater National Forest, the Border Zone 

bedrock types had the highest frequency of slides per 

unit area; Batholith types had the lowest (p. 122). Rock 

types with a high mica content were the most prone to 

landslides. Occurrence of bedding planes parallel to 

sideslopes also increased slide hazard (p. 122). Effects 

of rock weathering on landslide frequency were not 

clear (p. 123). In the Belt Series, slide frequency 

increased with increased fracturing; on the other 

lithologies (bedrock types) the relationship was not as 

clear (p. 123). 

Forty-seven percent of slides occurred on slopes with 

gradients between 51 and 70 percent; 28 percent of 

slides occurred on slopes with gradients between 71 

and 90 percent (p. 125). Slide occurrence increased 

from the ridges downslope to the lower third of the 

slope (p. 126). The median drainage area above the 

slides was 0.6 hectares; 90 percent of slides had drainage areas of 4 hectares or less (pp. 126-127). Slide 

frequency by landtype was given for the Clearwater 

data (p. 128). 

Road construction was the most important factor 

contributing to landslides. Fifty-eight percent of the 

slides were associatedwithroadedareas uninfluenced 

by logging or fire; another 30 percent were associated 

with roads in combination with logging or fire. Seven 

percent of slides were associated with fire only; 

2 percent with logging only; 3 percent occurred on 

undisturbed sites (p. 130). 

Sixty-six percent of the road-associated slides originated on roadcuts, 27 percent on roadfills without 

culverts, and 7 percent on fills with culverts. Fortyseven percent of the volume of road-associated slides 

originated on roadcuts, 31 percent on fills without 

culverts, and 21 percent on fills with culverts. However, of the slide material delivered to streams, 33 

percent originated on cuts, 51 percent on fills without 

culverts, and 16 percent on fills with culverts (p. 131). 

For roads built to lower standards, landslide frequency decreased. This was attributed to the reduction in excavation required for successively lower 

standards. The average number of slides per kilometer of road was 2.2 for arterial, 1.2 for collector, 0.6 for 

service, and 0.2 for temporary or terminal roads (p. 131). 

The frequency of landslides tended to increase as 

either tree or shrub crown cover decreased (p. 132). 

When crown covers were less than 80 percent, landslide occurrence appeared to be more sensitive to 

reductions in shrub crown cover than to reductions in 

tfee crown cover. The authors recommended using 

timber harvest procedures that minimize the disturbance of understory vegetation (p. 132). Landslides 

were most common 4 to 10 years after logging; landslide frequencies remained elevated for 20 years after 

logging (p. 133). These time trends were attributed to 

the loss of root strength through decay (increasing 

landslides) interacting with growth of new roots (decreasing landslides) (p. 132). 

Some of the damages and costs associated with the 

landslides were given (p. 135). These include the area 

of slide scars, repair costs, stabilization costs, and 

volumes of material delivered to streams. 

Gray and Megahan 1981, Pine Creek Study Area, 

Middle Fork of the Payette River drainage, Boise Nutional Forest-Several analyses evaluated the contributions of forest vegetation to slope stability. Vegetation contributes to slope stability through root 

reinforcement, surcharging (vertical downward force 

exerted by the weight of the trees), soil arching (when 

soil begins to move through and around a row of trees 

firmly embedded or anchored in an unyielding layer), 

and regulating soil moisture (abstract and p. 2). The 

analyses showed that many sites in the Idaho Batholith 

are in a state of marginal equilibrium, and may fail 

when roads are constructed or trees. are harvested 

(p. 20). 

Based on their research, the authors offered management guidelines: 

Limit the size of clearcuts 

Stagger clearcuts in space and time 

Leave buffer zones above and below haul roads, 

along streams, and in critical areas 

Leave as much residual vegetation as possible 

Favor selection cutting over clearcutting 

Drain surface runoff from roads onto areas of 

undisturbed vegetation (p. 21). 

Tennyson and others 1981, Horse Creek Study Area, 

Nez Perce National Forest-The authors studied the 
effects of various road construction and road stabilization methods on erosion, sedimentation, and 

strearnflow. (Only general erosion processes, time 

trends, and seasonal trends are summarized here. 

Other results appear elsewhere in this report.) Road 

construction in the study area began in 1978 and was 

completed in 1979 (p. 2). Data collected through 1980 

were included in the report. 

Fillslope erosion included surface and mass erosion. 

Surface erosion was primarily sheet and rill erosion 

begun by rainstorms; this process was most active 

during the first few summer months following construction (p. 11). Mass erosion was primarily slumping 

of saturated soils during spring snowmelt. Fill erosion 

was greater in the summer than in the winter, decreasing from the first to the third summer (p. 14). 

About 44 percent of the rill erosion in fills occurrea 

during intense summer storms in the first 6 to 8 weeks 

after construction before the slopes had been seeded 

and hydromulched (pp. 37-38). 

Surface and mass erosion processes were also operating on the cutslopes. On the cutslopes, dry ravel 

(movement not caused by water) was an important 

surface erosion mechanism (D. 20). No reduction in 

cutslope erosion over time was apparent; winter erosion was greater than summer erosion (p. 21). Slumping during snowmelt was the major erosive process on 

cutsIopes (p. 67). Cumulative erosion from cutslopes 

was greater than that from fillslopes during the study 

(pp. 23,251. 

Various tables and graphs show time trends in the 

distance sediment flowed below fillslopes (pp. 42,45- 

46). Ditch elevation data (measured for 1 year following construction) were variable. There was a general 

trend toward degradation during snowmelt and aggradation during the summer (p. 70). 

Carlton and others 1982, Gospel Hump management 

areas, Nez Perce National Forest-Erosion plots were 

established on undisturbed sites, logged sites, and 

road fillslopes. Most of the harvested sites had been 

tractor logged; a few had been logged using skyline 

systems. Fillslopes had been fertilized, seeded, and 

hydromulched (p. 13). Roads were constructed and the 

areas were logged in 1978 and 1979; plots were installed in the late summer of 1979 and data were 

collected from the spring of 1980 through the fall of 

1981. 

Erosion was not significantly different on the undisturbed and harvested plots. The "percent bare ground" 

variable alone adequately predicted erosion (pp. 18, 

23-24). Equations were developed to predict the time 

required for recovery following disturbance on undisturbed or logged sites (pp. 25-26,28). 

Rill and gully erosion processes were dominant on 

the road fillslopes (p. 45). Rill survey data showed that 

most ofthe erosion occurred by the first measurement 

in the spring of 1980 (p. 30). The authors present the 

results of fillslope regression analyses giving seasonal 

or yearly erosion over time based on fillslope length 

and vertical height of the fill (pp. 32-35). 

Clayton 1983, Silver Creek Study Area, Boise National Forest-Seismic and resistivity geophysical 

surveys were used together with vegetation surveys to 

predict subsurface bedrock properties related to slope 

stability before road construction (pp. 1,2). Granitic 

rock in weathering class 7 (Clayton and Arnold 1972) 

and highly weathered basic dike rock were grouped 

together in a category called highly weathered rock; 

this category represents the greatest hazard for mass 

failures (pp. 1,2). 

Using the above combination of techniques to predid zones of highly weathered rock produced only one 

false negative (11 of 12 zones with highly weathered 

rock were predicted correctly); however, the techniques produced 10 false positives (10 zones predicted 

to be highly weathered rock were not). Field reviews of 

the geophysical data are necessary to eliminate false 

positives. The geophysical surveys were useful in 

planning the road drainage system (p. 5). 

Megahan 1983, Pine Creek Study Area, Boise National Forest-A paired watershed study evaluated 

the effects of clearcutting and wildfire on the hydrology of small first-order watersheds. Calibration measurements beganin 1970. InNovember 1972 one watershed was clearcut; in August 1973 both watersheds 

were burned by wildfire (pp. 812-813). 

On the clearcut watershed, there were large changes 

in several hydrologic variables (pp. 811, 816). The 

volume of subsurface flow intercepted at a roadcut 

increased 96 percent, with 27 percent higher peak flow 

rates. Similar changes were not detected on the 

unlogged watershed. Increased surface and mass erosion hazards are associated with the types and directions of the hydrologic changes observed (p. 811). 

The author recommended limiting clearcut size or 

using other silvicultural systems in areas where mass 

erosion hazards are a concern (p. 818). He also noted 

that interception of subsurface flow should be considered in planning road drainage systems and road 

locations relative to clearcuts (p. 818). 

Vincent 1985, Silver Creek Study Area, Boise National Forest-Runoff and sedimentation were measured during snowmelt and rainstorms on three sections of native roadway surface varying in gradient 

from 6.3 to 13.4 percent. The road was constructed in 

1980, extensively eroded before the first measurements in 1981, and regraded before the 1982 measurements (pp. 7-9); it was closed to traffic throughout the 

study period. 

Although 55 percent of the annual precipitation falls 

as snow (p. 16), and about 91 percent of the snowmelt 
runs off (p. 281, less than 10 percent ofthe total annual 

sediment yield from the road tread occurs during 

snowmelt (p. 52). However, snowmelt runoff may 

generate surface or mass erosion of fills if it is discharged onto the fill (p. 28). Road tread sediment 

production was dominated by short duration moderate- to high-intensity rain (p. 30). 

The road was less erodible in the eroded condition 

than in the regraded condition; a given amount of 

runoff generated 75 to 80 percent less sediment for the 

erodedroad in 1981 than for the regradedroadin 1982 

(p. 39). 

Sediment yields from t&e road tread increased with 

increasing gradient (p. 53). For the graded surface, 

plots withgradients of 6.3 percent had sediment yields 

of 21 tomes per hectare, those with gradients of 9.0 

percent had sediment yields of 37 tomes per hectare 

and those with gradients of 13.4 percent had sediment 

yields of 71 tonnes per hectare (p. 57). Gradient effects 

were more pronounced for snowrnelt sediment. (p. 55- 

56). 

Clifion and Megahan 1988, South Fork Salmon 

River drainage, Payette and Boise National ForestsClosed roads were inventoried to evaluate surface and 

mass erosion (p. 1). Surface erosion results are discussed elsewhere in this report; only mass erosion will 

be discussed here. 

Of 168 road segments inventoried, 135 had no mass 

erosion; 91 percent of the volume of mass erosion was 

in 14 road segments (p. 7). No statistically significant 

relationships were found between mass erosion and 

road gradient, hill slope gradient, road tread erosion 

class, cut erosion class, fill erosion class, road runoff 

index, road runoff source, occurrence of culverts, aspect, or overall surface erosion index @. 8). Certain 

landtypes were more prone to landslides than others 

(p. 24). 

See Cliffon and Thompson (1989) for a followup 

report. 

Clifton and Thompson 1989, South Fork Salmon 

River drainage, Payette and Boise National ForestsSurface and mass erosion conditions were evaluated 

on 13 closed logging roads about 20 years after road 

closure (p. 3). Seven landtypes were representedin the 

four drainages studied (p. 3). 

Surface erosion was assessed as a class variable. In 

general, surface erosion was rated natural to very low 

(p. 3). Surface erosion was greatest on landtype llla, 

especially on the cutslopes in that landtype; the lowest 

values were in landtype 102. However, the range in 

average surface erosion rating by landtype was quite 

limited. 

Mass erosion was the dominant erosion process in 

the study area (p. 11). Long-term mass erosion rates 

were about 36 cubic yards per mile of road per year, or 

3.4 cubic yards per acre ofroad area per year, about 85 

times greater than the erosion rate on undisturbed 

sites in the area (p. 8). Slope gradient explained 97 

percent of the variance in landslide volume. Most 

?andslides occurred on 40 to 90 percent slopes. The 

highest frequency of landslides per mile of road was on 

landtype 120e-1 (p. 9). 

fitcheson and Megahan 1990, Silver Creek Study 

Area, Boise National Forest-Volumes and length of 

sediment flows below roads were measured for 4 years 

after road construction. Only 14 of the 346 sediment 

flows observed originated after the first year. Sixtynine percent of sediment movement occurred in the 

first year; 27 percent of that occurred during construction. By the fourth year, 254 of 346 sediment flows 

showed no change in length, width, or volume (p. 11). 

Megahan and others 1991, Silver Creek Study Area, 

Boise National Forest-Sediment from bordered 

fillslope erosion plots was measured for 3 years after 

road construction (p. 54). Several variables were tested 

as predictors of fillslope erosion, including elevation, 

slope gradient, azimuth, direct beam solar radiation, 

ground cover density, and erosivity index. The only 

statistically significant variables were ground cover 

density and snow-fiee period rainfall erosivity (p. 55- 

56). These were used to develop a prediction equation 

(p. 56). A graph (p. 56) was developed to show the 

probability of occurrence of sediment yields from granitic roadfills as a function of ground cover density. 

Methods to adjust the predicted values for other slope 

lengths and gradients were given (p. 57). 
References 
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Megahan, Walter F.; Kidd, Walter J., Jr. 1972a. Effect of logging 

roads on sediment production rates in the Idaho Batholith. Res. 

Pap. INT-123. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 14 p. 

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143; 182; 183, General Erosion Research Summary. 

Megahan, Walter F.; Kidd, Walter J., Jr. 1972b. Effects of logging 

and logging roads on erosion and sediment deposition from steep 

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Research Summary. 

Megahan, Walter F.; King, John G.; Seyedbagheri, Kathleen A. 

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41(4): 771-795. 

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Megahan, Walter F.; Monsen, Stephen B.; Wilson, Monte D. 1991. 

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smm. 

~egahan, ~dter~- onse sen, Stephen B.; Wilson, MonteD.;Lozano, 

Nicholas; Haber, Donald F.; Booth, Gordon D. 1992. Erosion 

control practices applied to granitic roadfills for forest roads in 

Idaho: cost effectiveness evaluation. Land Degradation and Rehabilitation. 3(1): 55-65. 

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Megahan, Walter F.; Seyedbagheri, Kathleen A.; Dodson, Patrick C. 

1983. Long-term erosion on granitic roadcuts based on exposed 

tree roots. Earth Surface Processes and Landforms. 8: 19-28. 

BMP numbers: 85,89, 90,91; 120; 148; 160; 167. 

Megahan, Walter F.; Seyedbagheri, Kathleen k; Mosko, Timothy 

L.; Keteheson, Gary L. 1986. Construction phase sediment budget for forest roads on granitic slopes in Idaho. In: Hadley, 

kchard F., ed. Drainage basin sediment delivery: proceedings; 

Albwueraue.NM: 1986Aumt 4-8. IAHSPubl. 159. Wallingford, -. 

oxon; UK: lntemational Association for Hydrological Sciences 

Press: 31-39. 

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Ohlander, Coryell A. 1964. Effects of rehabilitation treatments on the sediment production of granitic road materials. Fort Collins, 

CO: Colorado State University. 78 p. Thesis. 

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Packer, Paul E. 1966. Forest treatment effects on water quality. In: 

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State University. PA; 1965 Aumst 29September 10: Oxford; 

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Packer, Paul E. 1967. Criteria for designing and locating logging 

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166; 167. 

Packer, PaulE.; Christensen, George F. 1964. Guides for controlling 

sediment from secondary logging roads. Ogden, UT; Missoula, 

MT: U.S. Department ofAgriculture, Forest Service, Intermountain Forest and Range Experiment Station and Northern Region. 

42 p. Reprinted September 1977, U.S. Government Printing 

Office 1980-682-8661222. 

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Rurnrner, Robert B. 1982. Analysis of productivity, costs and site 

impacts of a second generation mall log skidder. Moscow, ID: 

Univemity of Idaho. Thesis. 

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Snyder, Gordon G. 1973. The effects of clearcutting and burning on water quality. Moscow, ID: University of Idaho. Thesis. 

A more accessible reference based on the same study is: 

Snyder, Gordon G.; Haupt, Harold F.; Belt, George H., Jr. 

1975. Clearcutting and burning slash alter quality of 

stream waterin northern Idaho. Res. Pap. INT-168. Ogden, 

UT: U.S. Department of Agriculture, Forest Service, IntermountainForest andRange Experiment Station. 34 p. 

BMP numbers: 71. 

Tennyson, Lany C.; King, John G.; Prud'homme, B. 1981. Erosional 

processes on forest mads and flow duration characteristics of the 

Horse Creek streams. Moscow, ID: University of Idaho; College of 

Forestry, Wildlife, and Range Sciences. 119 p. Cooperative Research Agreement INT-80-117-CA with U.S. Department of Agriculture. Forest Service. Intermountain Forest and Range Experiment Station. 

BMPnuTnbers:85,89,90,91;86,87,88; 103; 117; 12% 122; 128, 

129; 137, General Erosion Research Summary. 

Vincent, Kirk R. 1985. Runoff and erosion from a logging road in 

response to snowmelt and rainfall. Berkeley, CA: Universrty of 

~aiifornia. 60 p. and appendix. Thesis. 

BMPnumbers: 143; 166, General Erosion Research Summary. 
Seyedbagheri, Kathleen A. 1996. ldaho forestry best management practices: compilation 

of research on their effectiveness. Gen. Tech. Rep. INT-GTR-339. Ogden, UT: U.S. 

Department of Agriculture, Forest Service, Intermountain Research Station. 89 p. 

A search was conducted for quantitative ldaho research results on the effectiveness of 

the ldaho Forest Practices Act rules and regulations pertaining to timber harvest and forest 

road construction and maintenance. These rules and regulations are designated as the 

"best management practices" for the prevention of nonpoint source pollution from silviculture under the provisions of the Federal Clean Water Act. For each practice, the relevant 

research results are summarized; more general summaries for related groups of practices 

are also provided. 

Keywords: erosion control, nonpoint pollution, logging, road construction, road maintenance, water pollution 

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