Chapter 9 

Erosion, Sedimentation, and Cumulative 

Effects in the Northern Rocky Mountains 

Walter E Megahan and John G. King 

ABSTRACT Erosion and sedimentation are natural geomorphic processes 

characterized by large temporal and spatial variability. Recent radionuclide 

studies suggest that rare episodic events, such as large wildfires, produce 

massive sediment yields over time scales of thousands of years, thereby 

causing long-term average sediment production to exceed present-day 

average erosion rates by a factor of about 10. Even today, in undisturbed 

forested watersheds, sediment production is highly variable. Early studies 

of the effects of grazing and wildfire and surveys of river basins provided a 

foundation for much of the subsequent research on the effects of forest 

practices on erosion and sedimentation. The erosional and sedimentation 

effects of wildfire have been documented in many locations - ranging 

from none to minimal for low-intensity burns to catastrophic for highintensity burns. Management of forestlands to regulate the risk of wildfire 

effects on erosion and sedimentation is an important present-day concern 

throughout the region. 

Research consistently has shown that roads have the greatest effect of all 

practices associated with forest management on both surface and mass 

erosion. A large body of research shows, however, that much of the 

erosional impact of roads is manageable through proper land-use planning, 

location, design, construction, maintenance, and road closure. 

Considerable empirical data exists to illustrate surface erosion rates on 

roads, including time trends f0110~6ng construction as well as the effectiveness of a variety of erosion control practices. Effects of harvesting and 

associated site preparation activities on surface erosion are generally minimal and usually are controlled by providing downslope buffers. An exception is broadcast burning on harsh sites with highly erodible soils. Mass 

erosion, usually in the form of debris avalanches and torrents, is managed 

through risk assessment that uses inventory data and/or slope stability 

models to identlfy high-hazard site conditions. The primary management 

option for minimizing mass erosion resulting from roads or timber cutting 

is avoiding high-risk sites. Where avoidance is not possible, special design 

features are used, in the case of roads, or cutting and site preparation practices are modified, in the case of timber harvesting. 

Several empirical and process-based models have been developed to predict 

surface erosion rates, the effectiveness of a variety of erosion conti-ol practices, and downslope sediment delivery. Empirical data are the primary 
A Century of &rest and Wildland Watershed Lessons 

source of information for occurrence, magnitude, and downslope delivery 

of landslide material. Examples of downstream cumulative effects have 

been documented in terms of sediment delivery and associated channel 

responses. Methods to predict downstream cumulative effects are crude, 

however, limited primarily to sediment delivery, and are more applicable 

to smaller basins. Linkages between downstream cumulative effects and 

the impacts on beneficial uses, especially fish habitat, are poorly defined. 

KEYWORDS: allowable impacts, channel cross-section, cosmogenic isotopes, 

cumulative effects, episodic events, erodible soils, erosion, erosion control, 

fish, legislation, particle size distribution, prescribed burning, roads, routing, salmon, sedimeiitation, sediment delivery, sediment supply, site preparation, surface erosion, timber harvest, time trends, variability, wildfire 

Introduction 

In this chapter we describe some of the key information developed over 

the past 100 years about erosion, sedimentation, and associated cumulative 

effects in relation to forestland management in the northern Rocky 

Mountains (NRM). For purposes of this review, we define the NRM to 

include the states of Idaho and Montana. It is impossible to include all of 

the important studies that have been conducted. We include enough 

references to provide an overview of some of the important lessons learned 

and present our impressions of relevant research needs. 

Erosion, sedimentation, and associated downstream cumulative effects 

issues have long been a concern in the NRM. Prior to about 1950, the 

effects of sheep and cattle grazing on erosion and associated sedimentation 

were the primary problem. At issue was not only the potential for downstream sedimentation damages but also the effects of erosion on on-site 

range productivity. After World War 11, grazing pressures decreased, and 

demand for construction lumber led to increasing timber harvest during 

the 1950s. As the harvesting progressed from more easily accessed forestlands to steeper terrain, there was increasing concern about erosional 

effects and associated sedimentation damages from timber harvesting and 

road-building activities. 

A variety of legislation since the 1960s focused these concerns. 

Important federal legislation for managing National Forest lands such as 

the Multiple Use-Sustained Yield Act, the Forest and Rangeland 

Renewable Resources Planning Act, and the National Forest Management 

Act include protection of soil and water resources as a central theme. 

Additional legislation - including the Watershed Protection and Flood 

Prevention Act, the Resource Conservation Act, the National Environmental 

Policy Act, the Federal Water Pollution Act, and subsequent revisions to 

the Clean Water Act - was designed to protect soil and water resources on 

all lands, notjust national forests. Last, but certainly not least, the potential for sedimentation effects on threatened and endangered fish and 

amphibians identified under the Endangered Species Act is a widespread 
CHAPTER NINE 

concern throughout the NRM. Furthermore, both NRM states have developed statutes directed at erosion and sedimentation issues. 

Early Range Studies 

Most early studies were directed at the effects of wildfire or grazing on 

erosion and sediment production; these studies provide the basis for 

much of the subsequent work on forestlands. One of the earliest studies, 

by Connaughton (1935), documented the effects of wildfire on erosion of 

granitic soils in the Payette River basin of southern Idaho. He reported 

increasing erosion with burn intensity and slope gradient and greater 

erosion on previously logged areas compared to unlogged areas. Other 

fire-related studies documented the effects of wildfire on runoff and downstream damages. For example, Curtis and Packer (1951) described the 

effects of a 100-acre range fire that caused a flood peak large enough to 

close a highway with sediment deposits. 

Much of the early range research was carried out in southern Idaho in 

conjunction with watershed surveys in the Boise River drainage (USDA 

1940). The work was done to assess runoff and erosion source areas within 

the basin, in order to develop watershed management plans to protect 

large irrigation and flood control works. Using a sprinkling infiltrometer, 

Craddock and Pearce (1938) found that runoff and erosion were least on 

perennial wheatgrass range sites and greatest on annual weed sites and 

tended to increase with rainfall intensity, soil disturbance, and slope gradient in all cases. In 1939 and 1940, the US Geological Survey, working in 

cooperation with the US Department of Agriculture, collected daily runoff 

and sediment loads at several stations on streams in the Boise River basin 

(Love and Benedict 1948). Rosa and Tigerman (1951) used these data to 

relate sediment production to watershed conditions within the river basin 

through the use of sediment rating curves. 

The sprinkling infiltrometer proved to be an important tool for several 

subsequent researchers for determining the effects of site factors on erosion rates. Packer (1951) showed that erosion on rangeland was inversely 

proportional to ground cover density plus litter and directly proportional 

to size of bare soil openings. A second study (Packer 1953) documented 

increased erosion by the simulated trampling of livestock. Meeuwig (1969, 

1971) found that erosion on rangeland depends chiefly on ground cover 

and slope gradient, with lesser effects from soil organic matter content 

and texture. 

Natural Variabili5 

Erosion and sedimentation are characterized by large spatial and temporal 

variability. Spatial variability results from differences in site conditions, 

including geology, climate, topography, soils, vegetation, and proximity to 

erosion source. Temporal variability results from varying short-term weather conditions and longer-term climatic trends, as well as natural and 

human-caused disturbances. Interactions between spatial and temporal 

components occur as sediments are routed down the watershed system. 

203 
A Cenlury of Forest and Wildland Watershed Lessons 

Surface Erosion 

Early studies showed the effects of spatial variability on erosion on rangeland in response to changing site conditions such as ground cover density, 

slope gradient, and soil properties. On most undisturbed forested slopes 

in the NRM, surface erosion is negligible because dense vegetative cover 

and surface litter prevent soil movement. I-Iowever, surface erosion can 

occur on undisturbed, erodible, coarse-textured soils, especially on south 

exposures where vegetation cover is sparse as a result of low soil-moistureholding capacities. Clayton and Megahan (1 997) report annual surface 

erosion rates on undisturbed forest sites on granitic soils in southern 

Idaho averaging 0.09 tons per acre. Erosion rates varied from to zero to 1.6 

tons per acre, depending on site factors such as ground cover density, rainfall erosivity, solar radiation loading, and soil depth. Natural disturbance, 

such as by fire, can increase surface erosion rates. Megahan and Molitor 

(1975) recorded annual erosion rates of 0.6 tons per acre the first year 

after wildfire on north-facing granitic slopes where there was no evidence 

of surface erosion prior to the fire. By the third year after the fire, erosion 

rates were negligible because of rapid regrowth of understory vegetation. 

Mass Erosion (Landslides) 

The vast majority of mass failures of concern to forest managers consist 

of debris avalanche landslides that occur on shallow soils overlying an 

impermeable layer, usually bedrock (Megahan, Day, and Bliss 19'78). In 

some cases, slumps may also be a problem, especially on roads. Both of 

these types of mass failures are episodic in nature and occur when shear 

stresses within a slope exceed shear strength. Thus, landslide occurrence 

is highly variable over both time and space, almost by definition. 

Inventories of hundreds of landslides (Megahan, Day, and Bliss 19'78; 

McClelland et al. 1997) show that landslides occur almost exclusively during very large storm events and vary on the basis of a variety of site conditions, such as type of bedrock, slope gradient, and slope location. Natural 

disturbances such as wildfire, earthquakes, insects, and disease can 

increase the occurrence of landslides (Croft and Adams 1950). 

Although landslides are a major concern in some areas of the NRM, 

landslide risks and occurrences are considerably less there than in other 

areas in the Northwest, such as the Coast Range of California, Washington, 

and Oregon. In a survey of slope stability problems in the western United 

States, Burroughs (1985) classifies about 10 percent of national forest 

lands in northern Idaho and western Montana and 12 percent in southern 

Idaho forests as having a "high potential" for landslide occurrence. 

The potential for mass erosion problems on landscapes may be evaluated through risk assessment, utilizing the results of landslide inventories to 

assist in the identification of high-hazard site conditions. Inventories of 

landslide occurrence and associated site characteristics have identified specific factors associated with high mass erosion hazard, including geologic, 
CHAPTER NINE 

soil, topographic, vegetation, and land-use characteristics (Megahan, Day, 

and Bliss 19'78; McClelland et al. 1999). 

Potential mass erosion problems have been evaluated more recently 

through risk assessment that uses slope stability models to identify landslide hazards at specific locations on the landscape. The infinite slope 

stability model accounts for the destabilizing effects of gravity and the 

components of friction and cohesion that resist failure. The LISA model 

(Hamrnond et al. 1992) uses the infinite slope stability model to determine a probability of failure and is useful for relative landslide hazard evaluation. More recently, slope stability models have been developed that 

combine the infinite slope model with hydrologic models. These models 

include SHALSTB (Montgomery and Dietrich 1994) and SINMAP (Pack, 

Tarboton, and Goodwin 1998). Local information on soils and geology and 

available landslide inventory data are used to calibrate these models. 

Considerable empirical data are available to illustrate the amount of 

sediment delivery to streams from landslides. Megahan, Day, and Bliss 

(1978) found an overall sediment delivery of 23 percent to channels in a 

survey of 629 landslides on the Clearwater National Forest in Idaho. A 

subsequent inventory of landslides on the Clearwater National Forest 

evaluated the effects of large storm events in 1995 and 1996 (McClelland 

et al. 199'7). An average of approximately 57 percent of the landslide 

material was delivered to streams from 907 landslides. 

Ward (1994) developed a two-step approach for estimating landslide 

delivery to streams. In the first step, site characteristics of landslide length, 

distance to the stream, and slope gradient are entered into a logistic 

model to determine whether a landslide will reach a stream. If the landslide is predicted to reach the stream, a multivariate model is used to 

estimate the percentage of slide volume being delivered. Site variables that 

are important for predicting delivery percent include slope gradient, 

distance to the stream, slide length, and ratio of slide length/distance to 

stream, depending on the type of disturbance at the landslide site (road 

prism location or natural slopes). 

Sediment Yields 

Numerous publications document that sediment yields can vary considerably from year to year in response to varying weather conditions and that 

episodic climatic events can increase sediment yields. However, long-term 

sediment yield data are limited to decades at best on undisturbed watersheds. Such data are available from 28 undisturbed study watersheds in 

Idaho ranging in size from 0.09 mi2 to 6.5 mi2 (USDA Forest Service, 

unpublished report). Lengths of records for the watersheds vary from 4 to 

28 years. Records for all stations were adjusted statistically to a common 17- 

year period from 1966 to 1982. The average annual sediment yield from 

all watersheds for this dataset was 33.1 yds3 mi-2 year1 and the range was 

7-76 yds3 year1. Statistically significant differences in sediment yield 

were explained mostly by differences in average annual streamflow (82 
A Century of Forest and U7ildland Watershed Lessons 

percent of variability) and watershed relief (3 percent of variability) 

between the study watersheds. These average sediment yields represent 

essentially pristine conditions without any human-caused or natural disturbances or major episodic climatic events. 

Granger, Kirchner, and Finkel (1996) showed that cosmogenic nuclide 

concentrations in stream sediments accurately reflect the area-averaged 

long-term (thousands of years) erosion rates of whole watersheds. 

Kirchner et al. (1998) compiled sediment data from 34 essentially undisturbed, forested watersheds in Idaho ranging in size from 0.1 mi2 to 13,550 

mi2, including 25 of the basins identified above. Lengths of records for the 

watersheds ranged from 4 to 79 years and averaged about 20 years. 

Sediment samples were collected from each watershed and analyzed for 

cosmogenic nuclide content to determine long-term average sediment 

yield. On average, the long-term sediment rates exceed the measured 

short-term rates by a factor of about 10. 

The Idaho watersheds had little or no glaciation, nor can the large 

differences between long- and short-term sediment rates be explained by 

climatic differences between Pleistocene and current climatic conditions. 

Apparently, long-term erosion rates and associated channel responses are 

driven by relatively rare episodic events that overshadow the short-term 

conditions represented by the available data sets. Episodic events are 

caused by large storms, often coupled with natural disturbances - especially 

wildfire - and result in very large sediment yields that can have major 

impacts on channel systems. Several such episodic events have occurred in 

Idaho in recent years from landslides during large storm events (Megahan, 

Day, and Bliss 1978; McClelland et al. 1997) and from intense wildfires 

(USDA Forest Service 1996; Pacific Watershed Associates 1998). 

Effects of Timber Harvest 

Timber harvest practices used in the NRM have minimal effects on 

erosion, which are small in comparison to the effects of the road system 

used to support the timber harvest. For example, jammer and skyline logging on steep granitic soils in central Idaho had a six-year average annual 

surface erosion rate of 0.06 tons per acre - only about 1.6 times the 

natural rate. In contrast, surface and mass erosion rates from the associated 

logging roads were 220 and 550 times natural rates, respectively (Megahan 

1975). Megahan (1980) summarizes the reported soil disturbance from 

various studies of logging systems in the Pacific Northwest and British 

Columbia; he found an average of 21 percent from tractor logging, 13 

percent from ground cable logging, 8 percent for skyline logging, and 4 

percent for aerial logging systems such as helicopter logging. Thus, one 

means of controlling surface erosion is selection of a harvesting system 

that minimizes ground disturbance and exposure of soil. Soil losses usually 

are small on harvest areas because most logging systems disturb less than 

about 30 percent of the soil surface, and bare areas are small, rough, and 

discontinuous (Rice, Rothacher, and Megahan 1972). 
CHAPTER NINE 

Site preparation activities can have more effect on the potential for 

surface erosion than logging itself. Prescribed burning is the most 

commonly used technique for site preparation in the NRM; it also is used 

to reduce the hazard for wildfire. The erosional consequences of burning 

depend on the severity of the burn and resulting reduction in vegetation, 

slash, litter, and humus. One plot study in the mixed conifers of northern 

Idaho found that a spring prescribed burn under relatively moist conditions retained sufficient ground cover to cause only minimal amounts of 

erosion (Robichaud, Graham, and I-Iungerford 1994). At the other 

extreme, broadcast burning of clearcuts on south-facing slopes on granitic 

soils in southern Idaho accelerated erosion on the burned portions to 

about 8 tons per acre - 66 times natural rates (Megahan, King, and 

Seyedbagheri 1995). At this harsh site, much of the sustained erosion is 

attributed to slow vegetation recovery. Clayton (1981) attributed 32 

percent of the first-year postlogging erosion to the broadcast burning. 

Thus, use of fire for site preparation and fuel reduction is not appropriate 

for all sites. Lopping and scattering slash or a silvicultural practice that 

retains more of the residual stand may be more appropriate at sites with 

steep slopes and highly erodible soils or at harsh sites where revegetation 

rates are slow. 

Sediment travel distance from surface erosion in areas of diffuse runoff 

such as timber harvest units is minimal and easily controlled by providing 

downslope buffers of vegetation and debris on the ground. Both Idaho 

and Montana have rules and regulations that provide for streamside mailagement zones and regulate activities within these areas. We are not aware 

of any studies in the NRM to determine appropriate buffer widths below 

harvest units as a function of site characteristics. However, sediment travel 

from other areas with diffuse sources of runoff, such as road fills, averaged 

only about 8 feet below the toe of the fill in one study in northern Idaho 

(McMurtray-Carlton, King, and Tennyson 1982) and 12 feet in a study in 

southern Idaho (Ketcheson and Megahan 1996) and varied with the 

volume of erosion and the amount of obstructions on the slope (Megahan 

and Ketcheson 1996). 

Forest vegetation often provides the margin of safety between a secure 

slope and a landslide by providing root strength, removing soil water by 

evapotranspiration, anchoring the soil mass into the fractured bedrock, 

and buttressing and soil-arching action behind embedded tree trunks 

(Gray and Megahan 1981; Ziemer 1981). Studies of loss of root strength 

over time following timber harvesting (Burroughs and Thomas 1977) and 

frequency of landslide occurrence with time after timber harvesting 

(Megahan, Day, and Bliss 1978) suggest that landslides are most frequent 

410 years after logging. Unlike in coastal areas, mass erosion resulting 

from timber harvest is not a serious problem in the NRM. Megahan, Day, 

and Bliss (1978) found that only 2 percent of the landslides on the 

Clearwater National Forest occurred on cutting units, compared to 3 
A Century of Forest and Wildland Watershed Lessons 

percent on undisturbed areas. In a later study on the same area, 

McClelland et al. (1997) found that 12 percent of landslides occurred on 

cutting units, compared to 29 percent on undisturbed slopes. In areas 

where landslide risks are high, modifications to harvest practices can 

reduce landslide potential. Practices might include selection logging in 

preference to clearcutting, reduction in the size of clearcuts, establishment 

of vegetation leave areas, and integration of road drainage measures with 

vegetation leave areas (Gray and Megahan 1981). 

Effects of Roads 

Road construction results in exposure of bare soil, placement of unconsolidated material on the slope, soil compaction, destruction of soil 

aggregation, interception of subsurface flow, and concentration of surface 

runoff, all of which increase the potential for erosion and off-site sedimentation. Thus, it is not surprising that research has consistently shown 

that roads have the greatest effect on erosion of all practices associated 

w i t h 

forest management. Although other management activities, such as timber 

harvesting, usually occur on a larger percentage of the landscape, erosion 

rates on roads are large enough that they are the dominant source of 

sediment in the NRM. 

Magnitude of Road Effects 

Surface erosion from roads generally is highest during the first year 

following construction and decreases rapidly with time (Figure 9-1). 

Erosion rates during the first year following road construction of standarddesign roads on highly erodible granitic soils have been measured to 

exceed natural rates by up to 2,000-3,000 times, with erosion rates exceeding 90 tons per acre (Megahan and Kidd 19'72; Ketcheson, Megahan, and 

King 1999). The amount of surface erosion in the first year following construction accounted for 66-86 percent of total erosion measured over a 

four- to six-year period. Both armoring of the soil surface and reestablishment and growth of vegetation reduce surface erosion over time. The 

initial high road erosion rates following construction often are attributed 

to erosion of unconsolidated fill material (Megahan and Kidd 1972; King 

1984). At many sites, however, fillslope revegetation is sufficient after a year 

or two, so the long-term source of sediment is from the cutslopes, 

road tread, and ditch system. Moreover, traffic, road grading, and ditch 

cleaning rejuvenate a supply of finer sediments, and ditch cleaning may 

reinitiate an increase in cutslope erosion. Thus, most road systems represent a potential continuous source of sediment, although the source of the 

sediment will change over time. For example, a road built in the 1930s in 

one small study watershed was still producing about two tons per acre of 

erosion 37 years after construction-about a 50-fold increase over natural 

rates (Megahan 1974). Much of the erosion was attributed to continuing 

erosion of the cutslopes (Megahan, Seyedbagheri, and Dodson 1983). 
CHAPTER NINE 

100 

Figure 9-1. Eroszon afto c 

0 80 .- construction of roads zn U) Zena Creek and Silzw 2 Creek, Idaho. 

3 60 

S 

Y- O 

% 40 

f 

G 20 P 

0 

0 1 2 3 4 5 6 

Years after road construction 

Roads have also consistently been shown to have the greatest effect on 

mass erosion of all practices associated with forest management. 

Inventories of landslides conducted on two national forests in Idaho 

following major climatic events showed that landslides associated with 

roads accounted for 88 percent (Megahan, Day, and Bliss 1978) and 57 

percent (McClelland et al. 1997) of total landslide occurrences, respectively. 

In tlie earlier study, delivery of material to streams from road-associated 

landslides varied with location of the slide source in the road prism; 

cutslope slides delivered an average of 33 percent, whereas fillslope slides 

delivered 44 percent. In the later study, delivery of material to streams 

from road-associated landslides averaged about 25 percent. 

Controlling Road Erosion 

Although roads represent an important potential source of sediment, a 

large body of research shows that many of the erosional impacts of roads 

are manageable through proper land-use planning, location, design, construction, maintenance, and closure. Application of four basic principles 

can reduce the erosion and sedimentation impacts of roads (Megahan 

1977). A thorough knowledge of site conditions is required in applying 

these principles and deciding which combination of applications is best 

for the site and the planned activities. 

The first principle is preventive; it involves recognition and avoidance of 

high-erosion hazard areas (Megahan and King 1985). These areas include 

excessively steep slopes, highly erodible soils, areas with a high risk of landslide, and areas with a high potential to deliver sediment to streams. 

The second principle, also preventative, is to minimize the total amount 

of landscape disturbed by roads. This goal is accomplished in two ways: by 

minimizing the total length of roads and by keeping the roads as narrow 

as possible to accommodate transportation and drainage needs. The total 

mileage of roads necessary often is related to the type of yarding system 

used in the timber harvest operation. Some tractor and short-lead cable 

systems have had more than 25 percent of the area in roads, whereas 

209 
A Century of Forest and Wildland Watershed Lessons - 

skyline and helicopter yarding systems typically require less than 4 percent 

of the area in roads (Megahan 1985) (Figure 9-2). Thus, selection of the 

logging system can be used to reduce road length. Minimizing total road 

disturbaice also is accomplished by making roads as narrow as possible 

and rolling the grade to conform to the topography. This technique 

reduces surface erosion by minimizing the road disturbance width and the 

heights of cut- and fillslopes. Minimizing total road disturbance also 

reduces the occurrence of landslides. Landslide occurrence on roads is 

directly related to the amount of excavation required for the design standard of the road (Megahan, Day, and Bliss 19'78), so landslide occurrence 

on larger main arterial roads is considerably higher (3.5 slides per mile of 

road) than for narro~ver terminal roads (0.3 slides per mile of road). 

Figure 9-2. Percentage of 

area disturbed by dqferent 

logging systems. 

Tractor Groundline Skyl~ne Aer~al 

logging System 

The third principle is to provide for design or treatments on road features 

that reduce erosion. In the case of surface erosion, a considerable amount 

of research has gone into quantifying the effectiveness of a variety of road 

erosion control practices. Guidelines have been developed that describe 

the effectiveness of many of these treatments (Burroughs and King 1989). 

Fillslope treatments that combine a surface amendment, typically a mulch, 

with a revegetation measure, seeding, sprigging, or trailsplanting are more 

successful than either a surface amendment or revegetation measures 

alone (Megahan et al. 1992). Treatments that include an application of 

mulch with a means of holding the mulch in place on the slope (e.g., 

asphalt tackifier, net, or crimping) in combination with seeding or seeding 

and transplanting can reduce fillslope erosion more than 90 percent. 

Much of this effectiveness can be lost, however, if direct runoff from the 

road tread is diverted to fillslopes (King 1979). Thus, maintenance of the 

designed drainage system also is critical in reducing fillslope erosion. 

Cutslopes, which typically are constructed with steeper gradients than fillslopes, are prone to dry ravel and sloughing processes. Erosion control 

treatments on cutslopes are less successful; reported reductions in erosion 

for terracing and mulch applications, both with seed and fertilizer, are in 

the range of 30-60 percent (King 1994; Megahan, Wilson, and Monsen 

2001). The road tread also is a source of sediment, and rutting of the road 
CHAPTER NINE 

tread from traffic concentrates runoff and increases surface erosion. 

surfacing forest roads effectively reduces erosion, and plot studies of 

of gravel, bituminous surfacing, and dust oil have shown 

in road tread erosion exceeding 77 percent (Burroughs and 

King 1985). Use of lowered tire pressures on logging trucks also results in 

surface erosion, partly because it causes less-defined wheel ruts 

(Foltz 1995). Plot studies on short road segments indicate a twofold to 

more than a fourfold increase in sediment production from freshly graded 

roads that become rutted (Foltz and Burroughs, 1990). Thus, routine 

grading or road closures to minimize rutting are additional options for 

erosion control. 

In the case of mass erosion on roads, special design features often are 

used to reduce sidecast material, bench roads, compact fills, control 

drainage, and retain cut- and fillslopes. Excellent technical guidelines 

describing these and other road construction techniques in high-risk areas 

are available (Burroughs, Chalfant, and Townsend 1976; Chatwin et al. 

1994). Control of drainage is critical in minimizing slope failures. 

The fourth principle is to minimize the delivery of road-derived 

sediments to streams. This approach requires careful planning of road 

locations to minimize the number of stream crossings and maximize slope 

travel distance to streams. Several empirical studies make it possible to 

estimate sediment travel distance below roads on the basis of local site 

characteristics. Haupt (1959) defines sediment travel distance from roads 

constructed on granitic materials in southern Idaho as a function of the 

amount of obstructions on the slope below the road, cross-ditch spacing 

on the road, fillslope embankment length, and road gradient. Packer 

(1967) found sediment travel distance to be controlled by cross-drain 

spacing on the road, slope obstruction characteristics, fillslope cover 

density, soil particles greater than 2 mm (characterized by type of geology), 

and road age. Both of these studies provide prediction equations for total 

sediment travel distance. Other researchers have defined the probability 

of sediment travel distance below road culverts on border zone geology in 

northern Idaho (Burroughs and King 1989) and on granitic soils in 

southern Idaho (Ketcheson and Megahan 1996). Additional studies make 

it possible to define not only how far sediment travels below roads but also 

how much travels how far. Wasniewski (1995) developed relationships 

between cumulative sediment volume and travel distance below roads on 

granitic and gneiss/schist soils in northern Idaho. King (1979) presents 

data for the percentage of eroded sediment volume that travels given 

distances below roads on border zone soils in northern Idaho, and 

Ketcheson and Megahan (1996) present similar data for granitic soils in 

southern Idaho. Megahan and Ketcheson (1996) developed a prediction 

equation for sediment travel distance based on the volume of road erosion, 

runoff source area, hillslope gradient, and obstructions below the road, 

and they provide a relationship showing sediment volume in relation to 
A Century of Forest and Wildland Watershed Lessons 

total flow length of sediment. Use of both equations makes it possible to 

predict the volume of sediment reaching channels and to evaluate the 

effects of alternative erosion control measures or road locations on the 

volume of sediment delivered to streams. One additional treatment - 

placement of slash generated from road-clearing operations on or below 

fillslopes - has been shown to be very effective in capturing sediment and 

reducing sediment transport distance (Cook and King 1983). 

Many older roads were located in areas with a high potential delivery of 

sediment to streams, such as in valley bottoms paralleling streams, often 

constricting the channel, or on unstable slopes with a high potential for 

landslides. In these cases, some form of road obliteration may be desirable. 

Although road obliteration is becoming more widely used, little information is available at this time to quantify either short- or long-term effects on 

sediment production. 

Predicting Road Erosion 

The number of empirical studies of surface erosion on roads conducted 

over the years in the NRM has led to the development of empirical models 

for predicting on-site erosion rates, the effectiveness of erosion control 

practices, and downslope delivery of eroded materials. Available empirical 

studies have been assembled into a methodology (known as the R1-R4 

Sediment Yield Prediction model) for estimating the effects of roads and 

other forest disturbances on erosion and sediment yields (Cline et al. 

1981). Further discussion of the R1-R4 model is presented in the 

"Cumulative Watershed Effects" section below, 

In addition to empirical models, there has been considerable effort 

devoted to the development of process models for predicting road erosion. 

Simons, Li, and Shiao (1977) developed the first physically based process 

model for predicting sediment production from forest roads from individual storm events. The ROSED (Road SEDiment) model was applied to 

mine haul roads in Montana as well as forest roads in other locations 

(Ward 1985). The model considers all components of the road prism, 

including cutslopes and fillslopes, the running surface, ditches, and culverts. Hydrologic processes evaluated include interception, infiltration, 

overland flow routing, and sediment detachment and transport using raindrop splash and overland flow shear stress. 

More recently, the Watershed Erosion Prediction Project (WEPP) model 

has been applied to forest roads, areas of timber cutting, and burned forest 

areas (Elliot and Hal1 1997). The model is physically based and includes an 

evaluation of runoff and erosion processes similar to those considered in 

the ROSED model. WEPP also uses a long-term climate generator to simulate storm events as well as snowfall and melt, and it provides estimates of 

vegetation growth and the production of litter. The model was developed 

to replace the empirically based Universal Soil Loss Equation (USLE) and 

its successor the Modified Universal Soil Loss Equation (MUSLE). The 

current version of the model evaluates erosion and downslope sediment 
CHAPTER NINE 

movement from small areas (road sections or cutting units); a watershedscale version of the model for application on forest lands is under development. A simplified version of the model called X-DRAIN (Elliot et al. 

1998) provides estimates of sediment deposition below forest roads for 

selected conditions of cross-drain spacing, road gradient, length of forest 

buffer area below the road, steepness of the buffer, and soil texture. The 

model has been tested on forest roads in Idaho and elsewhere (Elliot, 

Hall, and Graves 1999) for both erosion rate on the road and sediment 

travel downslope below roads. 

Cumulative Watershed Effects 

Cumulative effects for the purposes of this chapter are the erosion and 

sedimentation consequences, both on and off site, of one or more forest 

practices (harvesting, road building, or fire) over time. Because the Clean 

Water Act mandates the assessment of cumulative watershed effects of land 

management activities, this issue is very relevant. Watershed case studies, 

process studies, and paired watershed studies are different strategies for 

addressing cumulative effects in basins of concern and for developing 

methods to predict cumulative watershed effects elsewhere (Reid 1993). 

All three of these approaches have been used in the NRM. 

Case Studies 

The best example of a case study on cumulative effects is the South Fork 

Salmon River basin. Historically, the South Fork Salmon River was the 

single most important summer Chinook salmon spawning stream in 

the Columbia River basin (Mallet 1974). Intensive logging and road construction took place between 1945 and 1965. The combination of highly 

erodible soils, steep slopes, soil disturbance from road building and timber 

harvest, and large climatic events in 1955, 1962, 1964, and 1965 delivered 

large quantities of sediment to the river, and by 1965 sediment quantities 

were in excess of the stream's transport capacity. There was deposition of 

predominantly sand-sized material throughout much of the river system, 

and prime salmon spawning and rearing areas were buried with sand. As 

a result, a moratorium on logging and road construction was imposed by 

the USDA Forest Service in 1966 for much of the basin. Assessments of the 

basin were performed in 1965 to estimate sediment volumes by source 

(USDA 19651, and over time rehabilitation practices were installed to 

reduce surface erosion and mass erosion. More than 400 miles of roads 

were closed and stabilized. 

River responses following the moratorium were monitored through 

photographic documentation, channel cross-section surveys, and transects 

to evaluate the particle size distribution of the river bed in spawning and 

rearing areas (Megahan, Platts, and Kulesza 1980). The watershed rehabilitation program reduced sediment supply to a level at which the river 

began to remove excess sediments. Conditions within the river improved 

with time (Figure 9-3) (Platts and Megahan 1975; Megahan, Platts, and 

Kulesza 1980). In 1978 the moratorium was lifted, and a new land-use plan 
A Century of Forest and Wildland Watershed Lessons 

- 

allowed cautious reentry into the basin. Monitoring continued to assure 

continuing improvement of the river conditions. A comparison of 

sediment storage in the river channel between 1965 and 1989 indicated 

that about '78 percent of the sand and gravel had been transported out of 

the river (Bohn and Megahan 1991). Such case studies or basin-wide 

assessments provide useful information on types and magnitudes of 

problems, sources of sediment, rehabilitation needs and priorities, and 

quantified time trends in recovery. 

Figure 9-3. (a) 1966: Cloy Hole almost complete~jlled with sand; (b) 1972: most 

sand is gone, and m'ginal rubbMoulder streambed surface is ~-euealed. Source: i'Itegahan, 

Potyondy, and Sqedbagheri (1992). Reprinted with permission of the publishm 

Paired Watershed Studies 

A second strategy for assessing cumulative sedimentation effects is paired 

watershed studies, which usually are carried out in conjunction with other 

studies to define and describe processes of erosion, sediment delivery, and 

sediment transport. Much research in the NRM relative to the cumulative 

effects issue has been conducted in small, paired watersheds - most less 

than 1 mi2 in area - on granitic and metasedimentary geology. 

Management treatments have been evaluated on I1 watersheds (Horse 

Creek and Silver Creek study areas), representing 102 station-years of data 

for pretreatment conditions and 109 station-years following treatment. 

Paired watershed approaches typically compare the effects of selected forest 

practices in treated watersheds with an undisturbed control watershed. 

These watersheds typically are monitored for a sufficient number of years 

in an undisturbed condition to determine natural rates and variability in 

erosion and sedimentation processes. Various forest activities are applied 

to each watershed, and conditions and processes are monitored for a 

suEciently long period to allow for substantial recovery of disturbed areas. 

The types of practices that have been monitored include different types of 

yarding systems, different sizes of clearcuts and amounts of timber harvested, different site preparation techniques, and different types of road 

standards and treatments. Measurements of conditions and processes vary 

by watershed but have included climatic variables, streamflow variables, 

sediment production, channel storage of sediment, hillslope storage of 

sediment, and erosion and site conditions on undisturbed slopes, harvest 

units, and road features. These small watershed and process studies have 
CHAPTER NINE 

been extremely useful in understanding processes and developing 

relationships that can be extrapolated to other areas in the NRM. 

Prediction Methods 

In the late 1970s Forest Senice researchers and soil scientists and 

hydrologists from the Northern and Intermountain Regions of the 

National Forest System collaborated in integrating information from small 

watershed studies and process studies with relevant research from other 

geographic areas to develop a methodology for estimating the erosional 

and sedimentation consequences of land management activities (Cline et 

al. 1981). This Guide for Predicting Sediment Yields from Forested Watersheds 

estimates average sediment production over time from harvesting, road 

building, and fire activities. 

This methodology, known as the R1-R4 Sediment Yield Prediction 

model, was developed principally for national forests and similar lands on 

watersheds in or generally associated with the Idaho batholith, but it has 

been applied elsewhere in the NRM. A landscape stratification procedure 

(Wendt, Thompson, and Larson 1975) provides the basic geomorphic 

response units for assessing erosion and sediment delivery to channels. 

The procedure provides an estimate of on-site erosion for a given management activity, modifies the amount of erosion according to erosion 

mitigation measures (best management practices) and general land-unit 

characteristics, delivers the eroded material to the stream system, and 

routes it through the watershed to a critical stream reach. The sediment 

delivery ratio approach used for sediment routing through channels 

provides unrealistic sediment supplies in larger watersheds because the 

effects of channel storage on the attenuation of the sediment wave are 

not considered. The procedure is widely used on national forest lands, 

primarily as a land-use planning tool to compare the effects of alternative 

land management activities on sediment production. It is structured so 

that new information and local data can be used to refine the procedure; 

thus, many variations of this procedure now exist. 

Megahan, Potyondy, and Seyedbagheri (1992) document application of 

the sediment yield prediction methodology, as adapted to the Boise 

National Forest in southern Idaho (Reinig et al. 1991), to compare sediment production from alternative timber harvest activities and wildfire in 

a major tributary of the South Fork Salmon River (Figure 9-4). Potts, 

Peterson, and Zuuring (1985) used the R1-R4 model to illustrate the possible effects of wildfire and post-fire timber salvage on sediment yields in 

the NRM. There has been limited comparison of modeled versus actual 

erosion or sediment yields using this procedure (Gerhardt 1992; 

Ketcheson, Megahan, and King 1999). The latter comparison was done on 

a research study area in the southern part of the Idaho batholith. The evaluation showed that model predictions of on-site erosion were very close to 

that measured but that predicted sediment delivery to and down streams 

was substantially higher than that recorded on study watersheds. The 
A Century of Forest and Wildland Watershed Lessons 

researchers conclude that the primary reason for overprediction of 

sediment delivery to streams is the fact that the Rl-R4 procedure assumes 

average conditions for landscape units and ignores road location in relation 

to proximity to streams. 

1300 2 

S 1200 5 I100 Improved road design 

Maximum mitigation 

I 1000 Helicopter logging 

E Figure 9-4. Comparison of modeled 

.1 900 time trend in sediment yields for alter- 2 

c 800 native land management practices for E South Fork of the Salmon tributary. < 700 0 Source: Megahan, Potyondy, and 2 600 Seyedbagheri (1 992). Reprinted with F mil pemzission of the publishex 

400 

1950 1955 1960 1965 1970 1975 1980 1985 1990 1996 

Year 

An effort has been made to develop a basin-scale physical process model 

to evaluate cumulative effects of alternative land management activities in 

the Gospel Hump area of the Nez Perce National Forest in Idaho. This 

model consisted of an expansion of the original ROSED model to a watershed scale; it was adapted to snowrnelt hydrology conditions that are common 

in central Idaho. The model, called SNOSED (SNOwrnelt-SEDiment) 

(Simons et al. 1981), included routines for sediment routing on the basis 

of measured channel conditions. The model was used to compare expected 

consequences of various long-term land management scenarios on streamflow and sediment production. However, SNOSED was evaluated on a 

small watershed for which sediment, streamflow, and climatic data were 

available. The results of the evaluation suggested the need for improvement of the model, especially with regard to how it models subsurface flow, 

before it can be considered sufficiently reliable (Barber 1982). 

Defining What's Allowable 

One major problem facing forest managers dealing with sedimentation 

effects of alternative management practices is to define how much sediment, of what kind, is allowable. There has been some effort toward such 

assessments in the NRM, but much more needs to be done. Wilson, Patten, 

and Megahan (1982) used an adaptation of the R1-R4 model on the 

Clearwater National Forest to develop a methodology to define how much 

change in annual sediment yield is needed to upset the geomorphic equilibrium of channels in headwater basins. First they made a comparison of 

R1-R4 predicted versus measured annual sediment yields for nine basins; 

there was reasonable agreement. Next, watershed characteristics for 65 

watersheds were used to predict annual sediment yields for undisturbed 

conditions and the existing disturbance condition. Low-gradient channel 

reaches at the mouth of each watershed were sampled for evidence of 

channel aggradation. The researchers developed a scattergram by plotting 
CHAPTER NINE 

predicted undisturbed sediment yield for each watershed against predicted 

sediment yield increase from management activities, expressed as a percentage over natural. Points on the scattergram were labeled for evidence 

of agg-adation in the channel. There was a clear break between channels 

with and without aggradation that suggested that increases in annual sediment yields of about 100 percent were needed to cause channel aggradation. 

Defining allowable sediment yield increases is linked most often to the 

need to know the impacts on beneficial uses, especially aquatic habitat and 

fish populations. In response to this need, fisheries biologists with the 

USDA Forest Service and the University of Idaho developed the Guide for 

Predzcting Salmonid Response to Sediment Yields in Idaho Baiholiih Watusheds 

(Stowell et al. 1983). This procedure uses the predicted average annual 

sediment yields from the R1-R4 model as input. Relationships were developed between predicted sediment yield and existing habitat conditions 

on selected watersheds and combined with relationships between habitat 

conditions and fish population responses from field and laboratory studies. 

This procedure is useful in land management planning to compare relative 

differences between management alternatives on fish populations. 

I-lowever, our ability to predict temporal and spatial responses in downstream habitats resulting from sediment yield increases from upstream 

land management practices is lacking. 

Only limited studies have been done to develop process-based models of 

sediment transport and habitat conditions. In one study of a Chinook 

salmon spawning reach of the South Fork Salmon River, a "salmonid 

spawning analysis model" was developed to model streamflow and sediment transport through the spawning reach, intrusion of fine sediment 

into Chinook redds, redd attributes of temperature, particle size distribution, interstitial velocities, and dissolved oxygen concentration (Havis et al. 

1993). This model perlormed well relative to data collected in artificial 

and natural 1-edds within the reach, but it does require calibration and 

known inputs of upstream streamflow, sediment, and stream temperature. 

This model is not directly linked to upstream erosion and sediment 

generated from forest activities. 

Research Needs 

Watershed scientists in the NRM region have made tremendous strides 

in understanding watershed processes and functions. This understanding 

has led to the development of useful sediment control methods and 

assessment tools that find application in management in this region and 

elsewhere. Nevertheless, we recognize the need for some additional 

research on erosion and sedimentation in the NRM. Variability in outputs 

of water and sediment from watersheds was recognized early in the 

research in this region. There is a need to develop a better understanding 

of natural variability and the factors influencing it, as well as how natural 

variability should be factored into decisions about forest management 

activities. Sediment delivery from upslope erosion sites and sediment 
A Century of Forest and Wildland Watershed Lessons 

routing connect hillslopes to streams and critical reaches. Progress has 

been made in understanding the factors influencing routing of sediment, 

but there is a need to develop practical methods for routing sediment 

through channel conditions that are representative of mountainous forested 

watersheds. In addition, we need to know how the delivered sediment 

affects different channel types or habitats and how this sediment impacts 

beneficial uses. Although assessment tools such as SNOSED and R1-R4 

have been developed in the NRM, there is a need to improve and test 

prediction models at the watershed scale. Watershed managers are being 

challenged to provide increasingly precise and robust assessments and to 

evaluate the cumulative effects of multiple management activities. 

Watershed models and watershed assessment tools provide the most effective 

means of meeting those demands. 

KEY LESSONS LEARNED IN THE NORTHERN ROCKY MOUNTAINS 

Erosion on rangeland is inversely proportional to ground cover and 

increases with slope gradient. 

Natural surface erosion rates in the NRM region are low. 

Long-term (1,000-year) erosion rates are an order of magnitude 

greater than background erosion rates measured at gaging stations, 

probably reflecting rare major hydrologic or disturbance events. 

In the NRM, mass erosion from harvest units is not a major problem. 

Roads are a major source of sediment to streams from both surface 

erosion and mass wasting. 

Four principles for minimizing erosion from roads are avoiding highhazard (steep, erodible) areas; reducing disturbance caused by roads 

by minimizing their length and width; designing and treating roads to 

reduce erosion; and minimizing delivery of sediment to streams. 

Cumulative effects have been studied using case studies, paired watershed studies, and process studies. 

Tools are available to predict sediment impacts from forest operations 

in this region. 

More research is needed to define allowable impacts from forest operations, but one study suggests that an increase of about 100 percent in 

background sediment loads is needed to cause measurable changes in 

channel aggradation. 

Literature Cited 

Barber, B.S. 1982. Application and evaluation of the Gospel-Hump 'SNOSED" model on a small forested 

water-shed in north-central Idaho. Master's thesis, University of Idaho. 

Bohn, C.C., and W.F. Megahan. 1991. Changes in sediment storage in the South Fork Salmon 

River, Idaho. In Proceedings ofthe Fzfth Federal Interagenq Sedimentation Conference, ed. S. Fan and 

Y. Kuo, 12-23 to 12-29. March 18-21, 1991, Las Iregas, NV. Washington DC: Federal Energy 

Regulatory Commission. 
CHAPTER NINE 

Burroughs, E.R., Jn 1985. Survey of slope stability problems on forest lands in the West. In 

Proceedings of a Wo-rkshop on Slope Stability: Problems and Solu,tions in Forest Management. General 

technical report PhW-180. Portland, OR: Pacific Northwest Forest and Range Experiment 

Station, USDA Forest Service. 

Burroughs, E.R., Jr., and J.G. King. 1985. Surface erosion control on roads in granitic soils. In 

Proceedings, Watershed Management in the Eighties, ed. E.B. Jones and T.J. Ward, 183-90. April 

30-May 1, 1985, Denver, GO. New York: American Society of Civil Engineers. 

-. 1989. Reduction ofsoil erosion onforest roads. General technical report INT-264. Ogden, UT: 

Intermountain Research Station, USDA Forest Service. 

Burroughs, E.R., Jr., and B.R. Thomas. 1977. Declining root strength in Douglaslfir after felling as a 

factor in shpe stability. Research paper INT-190. Ogden, UT: In~ermountain Forest and Range 

Experiment Station, USDA Forest Service. 

Burroughs, E.R., Jr., G.R. Chalfant, and M.A. To'ivnsend. 1976. Slope stabili9 in road construction: A 

guide to the construction of stabb roads in western Oregon and northern California. Portland: Oregon 

State Office, US Department of the Interior Bureau of Land Management. 

Chatwin, S.C., D.E. Howes, J.M': Schwab, and D.N. Swantston. 1994. A guide for management oflandslideprone terrain in the PaciJic Northwest, 2nd ed. Victoria, BC: Research Program, Ministry of 

Forests. 

Clayton, J.L. 1981. Soil disturbance caused by cbarcutting and helicopter yarding in the Idaho batholith. 

Research note INT-305. Ogden, UT: Intermountain Forest and Range Experiment Station, 

USDA Forest Service. 

Clayton, J.L., and W.F. Megahan. 1997. Natural erosion rates and their prediction in the Idaho 

batholith. Journal ofthe American Water Resources Association (33) 589-'703. 

Cline, R., G. Cole, W.F. Megahan, R. Patten, and J. Potyondy. 1981. Guide for predicting sediment 

yields from forested watersheds. Missoula, MT, and Ogden, UT: Northern Region and 

Intermountain Region, USDA Forest Service. 

Connaughton, C.A. 1935. Forest fires and accelerated erosion. Journal of Forestq 59:751-52. 

Cook, M. J., and J.G. King. 1983. Construction cost and erosion control effectiveness ofJilter windrows on 

fill slopes. Research note INT-335. Ogden, UT: Intermountain Forest and Range Experimental 

Station, USDA Forest Senice. 

Craddock, G.W., and C.K. Pearce. 1938. Surface run-ofand erosion on granitic mountain soils of Idaho 

as injluenced by range cova; soil disturbance, slope, and precipitation intensity. Circular no. 482. 

Washington, DC: US Department of Agriculture. 

Croft, A.R., and J.A. Adams. 1950. Landslides and sedimentation in the north fork of Ogden Rive? Maj 

1949. Research paper 21. Ogden, UT: Intermountain Forest and Range Experiment Station, 

USDA Forest Service. 

Curtis, J.D., and P.E. Packer. 1951. The ranch that blocked a highway. The Land 10(2):171-76. 

Elliot, WJ., and D.E. Hall. 1997. Water erosion prediction project (WP) forest applications. General 

technical report 365. Ogden, UT: Rocky Mountain Research Station, USDA Forest Service. 

Elliot, \V.J., D.E. Hall, and S.R. Graves. 1999. Predicting sedimentation from forest roads. Journal 

OfForesQ 97(8) :23-29. 

Elliot, MTJ., S.R. Graves, D.E. Hall, and J.E. Moll. 1998. The X-DRAIN moss drain spacing and sediment yield model. Publication 9877-1801. San Dimas, CA: Technology and Development Center, 

USDA Forest Service. 

Foltz, R.B. 1995. Sediment reduction from the use of lowered tire pressures. SAE 1994 

Transactions, Journal of Commercial lhhicles 2(103) :37&81. 

Foltz, R.B., and E.R. Burroughs, Jr. 1990. Sediment production from forest roads with wheel ruts. 

In Proceedings, Vl'atershed Planning and Analysis in Action, 26675. July 9-11, 1990, Durango, CO. 

New York: American Society of Civil Engineers. 

Gerhardt, N. 1992. Comparison of measured and modeled sediment yields on selected streams of 

the Nez Perce National Forest. In 2nd Annual Nonpoint Source Water Quality Monitoring Results 

Workshop. Boise: Division of Environmental Quality, Idaho Department of Health and Welfare. 
A Century of Forest and Wildland Watershed Lessons 

Gray, D.H., and W.F. Megahan. 1981. Forest vegetation removal and slope stabilzty in the Idaho batholith. 

Research paper INT-271. Ogden, UT: Intermountain Forest and Range Experiment Station, 

USDA Forest Service. 

Granger, D.E., J.W. Kirchner, and R. Finkel. 1996. Spatially averaged long-term erosion rates 

measured from in-situ cosmogenic nuclides in alluvial sediment. Journal of Geology 104:249-57. 

Hammond, C., D. Hall, S. Miller, and P. Swetik. 1992. Level Istability analyszs (LISA) documentatzon 

for version 2.0. General technical report INT-285. Ogden, UT: Intermountain Research Station, 

USDA Forest Service. 

Haupt, H. F. 1959. Road and slope characteristics affecting sediment movement from logging 

roads. Journal @Forestry 57(5):329-32. 

Havis, R. N., C. V. Alonso, J. G. King, and R. F. Thurow. 1993. A mathematical model of salmonid 

spawning habitat. Water Resources Bulletin 29 (3) :435-44. 

Ketcheson, G.L., and W.F. Megahan. 1996. Sediment productzon and downslope sediment transport from 

forest roads zn granztzc watersheds. Research paper INT-RP-486. Ogden, UT: Intermountain 

Research Station, USDA Forest Service. 

Icetcheson, G.L., W.F. Megahan, and J.G. King. 1999. "Rl-R4" and "BOISED" sediment yield 

prediction model tests using forest roads in granitics. Journal of the Ammcan Water Resources 

Association 35 (1):83-98. 

King, J.G. 1979. Fillslope erosion from forest roads. In Proceedings, 34th Meeting Amm'can Soczety of 

Agncultural Enpneers. October 2-5, 1979, Boise, ID. Paper 79-404. St. Joseph, MI: American 

Society of Agricultural Engineers. 

. 1984. Ongozng studies zn Horse Creek on water quality and water yzeld. Technical bulletin 435. 

New York: National Council for Air and Stream Improvement, Inc. 

-. 1994. Streamflow and sediment yield responses to forest practices in north Idaho. In 

Proceedzngs, Interzor Cedar-Hemlock-White Pine Forests: Ecology and Management, ed. D.M. 

Baumgartner, J.E. Lotan, and J.R. Tonn, 213-20. March 2-4, 1993, Spokane, WA. Pullman: 

Department of Natural Resources, Washington State University. 

Kirchner, J.W., R.C. Finkel, C.S. Riebe, D.E. Granger, J.L. Clayton, and W.F. Megahan. 1998. 

Episodic erosion of the Idaho batholith inferred from measurements over 10-year and 10,000- 

year timescales. Abstract in EOS Supplement, Transactions, Amm'can Geophysical Union 79:F338. 

Love, S.K., and P.C. Benedict. 1948. Dzscharge and sediment loads in the Boise River drainage basin, 

Idaho. Water Supply paper 1048. Washington, DC: US Geological Survey. 

Mallet, J. 1974. Inventory ofsaEmon and steelhead resources, habitats use and demands. Job Performance 

Report. Boise: Idaho Department of Fish and Game. 

McClelland, D.E., R.B. Foltz, W.D. Wilson, T.M! Cundy, R. Heinemann, J.A. Saurbier, and R.L. 

Schuster. 1997. Assessment @the 1995 & 1996floods and landslides on the Cleanuater NationalForest. 

Part 1: Landslide Assessment. USDA Forest Service Report. Missoula, MT: Northern Region, 

USDA Forest Service. 

McClelland, D.E., R.B. Foltz, C.M. Falter, W.D. Mrilson, T. Cundy, R.L. Schuster, J. Saurbier, C. 

Rabe, and R. Heinemann. 1999. Relative effects on a low-volume road system of landslides resulting from episodic storms in northern Idaho. Transportation Research Record 1652 (2):235-43. 

McMurtray-Carlton, M., J.G. King, and L.C. Tennyson. 1982. On-site erosion on natural and disturbed 

sozls, and natural bedload sediment productzon zn first-order drainages in the Gospel Hump area. Project 

Completion Report INT-80-115-CA. On file at Boise, ID: Forestry Sciences Laboratory, Rocky 

Mountain Research Station. 

Meeuwig, R.O. 1969. Infiltration and soil erosion on Coolwater Ridge, Idaho. Research note INT-103. 

Ogden, UT: Intermountain Forest and Range Experiment Station, USDA Forest Service. 

. 1971. Soil stability on high-eleuatzon rangeland in the intermountain area. Research paper INT94. Ogden, UT: Intermountain Forest and Range Experiment Station, USDA Forest Service. 

Megahan, W.F. 1974. Erosion over time on severe4 disturbed granzticsoib: A modcl. Research paper INT156. Ogden, UT: Intermountain Forest and Range Experiment Station, USDA Forest Service. 

-. 1975. Sedimentation in relation to logging activities in the mountains of central Idaho. In 

Sedzntent-Yzeld Workshop, Proceedings. November 28-30, 1972, Oxford, MS. Report ARS-S-40. 
CHAPTER NINE 

Oxford, MS: Sedirnent Laboratory, Agricultural Research Service, US Department of 

Agriculture. 

-. 1977. Reducing erosional impacts of roads. In Guidelines for Watershed Management, 

237-61. FA0 Conservation Guide. Rome, Italy: Food and Agriculture Organization of the 

United Nations. 

-. 1980. Nonpoint source pollution from forestry activities in the western United States: 

Results of recent research and research needs. In US. Forestrj and Water Quality: Vllzaf Course in 

the 80k? An Analysis ofEnvironmenta1 and Economic Issues. Proceedings, 92-151. June 19-20, 1980, 

Richmond, VA. Washington, DC: Water Pollution Control Federation. 

-. 1985. Road effects and impacts-watershed. In Forest Transportation Symposium; Proceedings, 

57-97. December 11-13, 1984, Casper, T4Y Lakewood, CO: Engineering Staff Unit: Rocky 

Mountain Region, USDA Forest Service. 

Megahan, T4'.F., and G.L. Ketcheson. 1996. Predicting downslope travel of granitic sediments from 

forest roads in Idaho. Joumaal ofthe American Water Resources Association 32(2) :371-82. 

Megahan, W.F., and I4T.J. Kidd. 1972. Effect of logging roads on sediment production rates in the Idaho 

batholith. Research paper INT-123. Ogden, UT: Intermountain Forest and Range Experiment 

Station, USDA Forest Service. 

Megahan, Mr.F., and P.N. King. 1985. Identification of critical areas on forest lands for control of 

nonpoiilt sources of pollution. Environmental Management 9(1):7-18. 

Megahan, T4'.F., and D.C. Molitor. 1975. Erosional effects of wildfire and logging in Idaho. In 

Watershed Management Symposium, American. Society of Civil Engineers, Irrigation & Drainage 

Division, 423-44. August 11-13, 1975, Logan, UT. 

Megahan, W.F., N.F. Day, and T.M. Bliss. 1978. Landslide occurrence in the western and central 

northern Rocky Mountain physiographic provinces in Idaho. I11 Forest Soils and Land Use, 

Proceedings, Fyth North American Forest Soils Colzference, 126-39. August 6-9, 1978, Ft. Collins, CO. 

Fort Collins: Colorado State University. 

Megahan, W.F., J.G. King, and K.A. Seyedbagheri. 1995. Hydrologic and erosional responses of a 

granitic watershed to helicopter logging and broadcast burning. Forest Science (41) :777-95. 

Megahan, W.F., W.S. Platts, and B. Kulesza. 1980. Riverbed improves over time: South Fork 

Salmon River. In Symposium on Watershed Management, Proceedings, vol. 1, 380-95. July 21-23, 

1980, Boise, ID. New York: American Society of Civil Engineers. 

Megahan, T4T.T.F, J.P. Potyondy, and RA. Seyedbagheri. 1992. Best management practices and 

cumulative effects from sedimentation in the South Fork Salmon River: An Idaho case study. 

Chapter 15 in Watershed Management: BalancingSustainabili$ with Environmental Change, ed. R.J. 

Naiman, 401-14. Kew York: Springer-Verlag. 

Megahan, \\'.F., K.A. Seyedbagheri, and P.C. Dodson. 1983. Long-term erosion on granitic roadcuts based on exposed tree roots. Earth SurfaceProcesses and Landforms 8:19-28. 

Megahan, JV.F., M. Uiilson, and S.B. Monsen. 2001. Sediment production from granitic cutslopes 

on forest roads in Idaho, USA. Earth Surface Processes and Landforms 26(1):1-11. 

Megahan; W.F., S.B. Monsen, M.D. TVilson, N. Lozano, D.F. Haber, and G.D. Booth. 1992. Erosion 

control practices applied to granitic roadfills for forest roads in Idaho: Cost effectiveness 

evaluation. Land Degradation and Rehabilitation 3:55-65. 

Montgomery, D.R., and W.E. Dietrich. 1994. A physically based model for the topographic 

control on shallow landsliding. K'ater Resour-ces Research 30:1153-71. 

Pacific Watershed ,4ssociates. 1998. Aaial reconnaissance evaluation of recent storm qfects on upla~zd 

mountainous watersheds of Idaho. Arcata, Gk Pacific Watershed Associates. 

Pack, R.T., D.G. Tarboton, and C.N. Goodwin. 1998. The SINbfAP ,approach to terrain stability 

mapping. Proceedings ofthe 8th Congress of the I?zternational Associatio~a ofEngineering Geology Sept. 

21-25, 1998, Vancouver, British Columbia, Canada. Heidelberg, Germany: Springer-Verlag. 

Packer, P.E. 1951. An approach to watershed protection criteria. Journal $Forestry 49(9) :639-44. 

. 1953. Effects of trampling disturbance on watershed condition, runoff, and erosion. 

Journal ofForestry 51 (1) 28-31, 

. 1967. Criteria for designing and locating logging roads to control sediment. Forest Science 

13(1):2-18. 

221 
A Century of Forest and Wildland Watershed Lessons 

Platts, W.S., and W.F. Megahan. 1975. Time trends in riverbed sediment composition in salmon 

and steelhead spawning areas: South Fork Salmon River, Idaho. In North American Wildlife and 

Natural Resources Conference, Proceedings, 229-39. March 16-19, 1975, Pittsburgh, PA. 

Washington, DC: Wildlice Management Institute. 

Potts, D.F., D.L. Peterson, and H.R. Zuuring. 1985. Watershed modeling forfire management planning 

in the Northern Rocky Mountains. Research paper PSW-177. Berkeley, CA: USDA Forest Service. 

Reinig, L., R.L. Beveridge, J.P. Potyondy, and F.M. Hernandez. 1991. BOISED user's guide and 

program documentation. Boise, ID: Boise National Forest, USDA Forest Service. 

Reid, L.M. 1993. Research and cumulative watershed effects. General technical report PSW-GTR-141. 

Albany, CA: Pacific Southwest Research Station, USDA Forest Service. 

Rice, R.M., J.S. Rothacher, and W.F. Megahan. 1972. Erosional consequences of timber harvesting: An appraisal. In National Symposium on Watersheds in Transition, 321-29. Middleburg, VA: 

American Water Resources Association. 

Robichaud, P.R., R.T. Graham, and R.D. Hungerford. 1994. Onsite sediment production and 

nutrient losses from a low-severity burn in the interior Northwest. In Interior Cedar-Hemlock-White 

Pine Forests: Ecology and Management, Proceedings, ed. D.M. Baumgartner, J.E. Lotan, and J.R. 

Tonn, 227-32. March 2-4, 1993, Spokane. Pullman: Department of Natural Resources, 

Washington State University. 

Rosa, J.M., and M.H. Tigerman. 1951. Some methods for relatzng sediment production to watershed 

conditions. Research paper No. 26. Ogden, UT: Intermountain Forest and Range Experiment 

Station, USDA Forest Service. 

Simons, D.B., R.M. Li, and L.Y. Shiao. 1977. Formulation ofa road sediment model. Report CER76 

77DBSRMLLYS50. Fort Collins, CO: Colorado State University. 

Simons, D.B., R.M. Li, R.T. Combs, and C.C. Baggs. 1981. Forest management impacts on snowmelt and 

rainfall sediment yield zn mountazn stream, vol. 1. Project report. Boise, ID: Intermountain Station, 

USDA Forest Service. 

Stowell, R., A. Espinosa, T.C. Bjornn, W.S. Platts, D.C. Burns, and J.S. Irving. 1983. Guide for 

predzctzngsalmonid response to sedzment yields in Idaho batholith watersheds. Missoula, MT and Ogden, 

UT: Northern Region and Intermountain Region, USDA Forest Service. 

US Department of Agriculture (USDA). 1940. Run-off and waterflow retardation and soil erosion 

prevention for flood control purposes - The Boise Rivm Survey report. Field Flood Control 

Coordinating Committee No. 17B. 

. 1965. SouthFork Salmon River storm andflood rqbort. Krassel Ranger District, Payette National 

Forest, USDA Forest Service. 

USDA Forest Service. 1996. Emergency watershed protection propam measure, North Fork Boise River 

flood, Boise and Elmore Counties, Idaho. Unpublished report. Boise, ID: Boise National Forest, 

USDA Forest Service. 

Ward, T.J. 1985. Sediment yield modeling of roadways. In Soil erosion and conservation, ed. S.A. ElSwaify, W.C. Moldenhauer, and A. Lo, 188-99. Ankeny, IA: Soil Conservation Society of America. 

. 1994. Modeling delivery of landslide materials to streams. WRRI Report 288. La Cruces: New 

Mexico Water Resources Research Institute. 

Wasniewski, L.W. 1995. Hillslope sediment routing below new forest roads in central Idaho. 

Master's thesis, Oregon State University. 

Wendt, G.E., R.A. Thompson, and K.N. Larson. 1975. Land systems inventmy, Boise NationalForest, 

Idaho: A basic inventory for planning and management. Boise, ID: Boise National Forest, USDA 

Forest Service. 

Wilson, D., R. Patten, and W.F. Megahan. 1982. A systematic watershed analysis procedure for 

Clearwater National Forest. Leachates: Terrain analysis. Transportation Research Record 892:50-56. 

Ziemer, R.R. 1981. Roots and the stability of forested slopes. IAHS publication 132, 343-61. 

Wallingford, UK: International Association of Hydrologic Sciences. 
A Century of 

Forest and Wildland 

Watershed Lessons 

George G. Ice and John D. Stednick 

Editors 

Society of American Foresters 

Bethesda, Maryland 
Copyright 0 2004 by the Society of American Foresters 

Published by 

The Soclety of American Foresters 

5400 Grosvenor Lane 

Bethesda, MD 20814-2198 

www.safnet.org 

Tel: (301) 897-8720 

Fax: (301) 897-3690 

ISBN 0-939970-88-0 

All rights reserved. No part of this book may be reproduced in any form or by any means, 

electronic or mechanical, including photocopying, recording, or by any information storage 

and retrieval system, without written permission from the publisher. Address inquiries to 

Permissions, Society of American Foresters, 5400 Grosvenor Lane, Bethesda, MD 20814-2198. 

Library of Congress Cataloging-in-Publication Data 

A centmy of forest and wildland watershed lessons I George G. Ice and John D. Stednlck, editors. 

p. cm. 

Includes b~bl~ographcal references. 

ISBN 0-939970-88-0 (pbk.) 

1. Hydrology, Forest 2 Forest management. 3. Watershed management. 

I. Ice, George G. I1 Stednick, John D. 111. Soc~ety of American Foresters. 

Printed in the United States of America 

10987654321 

Cover images 

ICenneth M. Gale, Dave Powell. SAX archives SAX archives 

www.forestryimages.org USDA ores st Service, 

www.forestryimages.org