Bear Valley Road Inventory (GRAIP) Report

In Support of the Bear Valley Category 4b Demonstration

USDA Forest Service, Boise National Forest

February 24, 2010

Chase Fly1, Kari Grover-Wier2, John Thornton3, Tom Black4, and Charlie Luce5

1Hydrologic Technician

2Hydrologist

3

Forest Hydrologist

USDA Forest Service

Boise National Forest

1249 S. Vinnell Wy.

Suite 200

Boise, Idaho 83709

4Hydrologist

5

Research Hydrologist

USDA Forest Service

Rocky Mountain 

Research Station

322 E. Front St.

Suite 401

Boise, Idaho 83702

Produced with funding from:
Bear Valley Road Inventory (GRAIP) Report

In Support of the Bear Valley Category 4b Demonstration, Boise National Forest

ii

Acknowledgements

Through an interagency agreement, the U.S. Environmental Protection Agency 

(USEPA) provided funding for the field inventory and data analysis in order to conduct 

GRAIP analysis for Bear Valley streams. Without this funding, the project would not 

have been possible. The views expressed in this document do not necessarily reflect 

the views of the USEPA. 

The following individuals were field crew members for the Boise National Forest who 

were critical to the progress of this road inventory and are acknowledged and 

appreciated for their contributions to the successful completion of this project:

Nathaniel Bogie

Curtis Martin

Blaise Bernal

Ernesto Matal Sol

Megan Jenkins

Michelle Fast

Rumika Chaudhry
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Table of Contents

Executive Summary ...................................................................................................... 5

1.0 Background ......................................................................................................... 7

2.0 Study Objectives ................................................................................................. 9

3.0 Methods.............................................................................................................. 10

4.0 Monitoring Location.......................................................................................... 11

5.0 Results ............................................................................................................... 14

5.1 Road-stream Hydrologic Connectivity .........................................................................14

5.2 Fine Sediment Production & Delivery..........................................................................14

5.3 Upstream Sediment Accumulation ..............................................................................27

5.4 Drain Point Condition..................................................................................................31

5.5 Stream Crossing Failure Risk .....................................................................................32

5.6 Gully Initiation Risk .....................................................................................................34

5.7 Landslide Risk ............................................................................................................36

6.0 Quality Assurance............................................................................................. 37

7.0 Summary & Conclusions .................................................................................. 41

Appendix A: Glossary................................................................................................ 43

Appendix B: QAPP Compliance................................................................................ 48

Appendix C: Bear Valley GRAIP Data Files.............................................................. 52

References................................................................................................................... 53

List of Tables

Summary Table. Summary of GRAIP model risk predictions for Bear Valley.........................6

Table 1. Assessment Units proposed to be on IDEQ’s 2010 Category 4b list ........................... 7

Table 2. Road length and density for Bear Valley by sub-watershed ........................................ 8

Table 3. Length of road inventoried by road type ...................................................................... 9

Table 4. Sediment production and delivery by drain point type ................................................16

Table 5. Drain point-stream connectivity and sediment delivery by drain point type.................17

Table 6. Sediment delivery values for specific road segments displayed in Figure 5 ...............23

Table 7. Stream sediment load values by sub-watershed ........................................................29

Table 8. Drain point condition problems...................................................................................32

Table 9. Quality assurance statistics........................................................................................39

List of Figures

Figure 1. Bear Valley area map...............................................................................................13

Figure 2. Distribution of sediment delivery by drain type..........................................................16

Figure 3. Distribution of sediment delivery by the percentage of drain points ..........................18

Figure 4. Bear Valley area map of sediment-delivering drain points ........................................20

Figure 5. Sediment delivery maps of specific road segments ..................................................21

Figure 6. Bear Valley area map of sediment production ..........................................................24
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Figure 7. Distribution of sediment delivery by the percentage of road length ...........................26

Figure 8. Distribution of sediment delivery by the percentage of road segments .....................26

Figure 9. Distribution of road surface types .............................................................................27

Figure 10. Bear Valley area map of stream sediment accumulation ........................................28

Figure 11. Road density versus accumulated road sediment rate by sub-watershed...............30

Figure 12. Distribution of Stream Blocking Index values..........................................................33

Figure 13. Distribution of drain points discharge locations by length and slope .......................35

Figure 14. Stability index for hillslopes on a portion of NFSR 583............................................37

Figure 15. Map of Quality Assurance plot locations.................................................................48

List of Photos

Photo 1. Two photos of field data collection ............................................................................10

Photo 2. Three photos of high delivery drain points.................................................................19

Photo 3. One photo of road surface on a segment of NFSR 583.............................................25

Photo 4. Four photos of examples of drain point condition problems.......................................31

Photo 5. One photo of a stream crossing ................................................................................33
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Executive Summary

Sediment has been identified as the pollutant of concern in multiple stream segments 

within the Bear Valley Creek and Elk Creek watersheds on the Idaho Department of 

Environmental Quality’s (IDEQ) 2008 Integrated Report. The IDEQ, in conjunction with 

the Boise National Forest (BNF), is in the process of preparing their 2010 Integrated 

Report including a Category 4b demonstration of Bear Valley Creek and Elk Creek for 

submission to the U.S. Environmental Protection Agency (USEPA). 

The USEPA funded a site-specific road sediment inventory in 2009 for the Bear Valley 

and Elk Creek watersheds to assist in the development of a possible Category 4b 

demonstration. This inventory specifically quantified the extent and location of sediment 

contributions from roads to streams, using the Geomorphic Road Analysis and 

Inventory Package (GRAIP, Prasad et al. 2007, http://www.fs.fed.us/GRAIP). This suite 

of robust inventory and analysis tools evaluates the following road impacts and risks: 

road-stream hydrologic connectivity, fine sediment production and delivery, upstream 

sediment accumulation, drain point condition, stream crossing failure risk, gully initiation 

risk, and shallow landslide risk.

The Boise National Forest with instruction from the Rocky Mountain Research Station 

(RMRS) of the U.S. Forest Service (USFS) collaborated and worked together in 2009 to 

execute a comprehensive road inventory in Bear Valley. Over a course of four weeks 

during the summer of 2009, field crews mapped and collected data on a total of 146 

miles of roads. Using the data, risk profiles for the roads were developed to assess

impacts and risks to key watershed processes. A summary of predicted risks is 

displayed in the table below.

Road-stream hydrologic connectivity was calculated to be 18 miles (12.5%). The total 

amount of fine sediment from roads accumulating in Bear Valley Creek, Elk Creek, and 

their tributaries was 821 tons/yr, which accounts for 10% of all the sediment produced 

on Bear Valley roads. The predicted sediment delivery rate from roads of 4.3 

tons/mi2/yr suggests a 17% increase of the natural reference sediment erosion rate as 

predicted by the BOISED model (Reinig et al. 1991). 

Approximately 10% of road drainage features were recorded to be in poor condition or 

in need of maintenance. The risk of stream crossings becoming plugged was evaluated 

based on a stream blocking index (SBI) where 1 indicates virtually no risk and 4 

indicates high risk. The average SBI for stream crossings in this survey was 2. A total 

of 21% of all stream crossings have diversion potential, suggesting some risk of stream 

water flowing down the road prism if the pipe is blocked.

Slope stability data, which includes the frequency and attributes of observed landslides 

and gullies, is used to calculate gully initiation risk and landslide potential resulting from 

roads. Very few hillslope failures were observed and recorded in the survey, making 

necessary calibration to predict such risk impossible. Although 22 gullies were 
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observed and recorded during the field survey, the distribution of the drain points where 

they occur in association with all drain points was scattered and suggested no point at 

which increased gully initiation risk can be expected. No landslides were recorded in 

the survey, thereby not allowing accurate calibration of risk assessment. Lack of 

observed landslide and gully data suggests no significant risk of mass wasting is added 

by the existence of roads in Bear Valley.

Quality assurance measures were taken in order to ensure the integrity of the data 

collected. Field crews were trained on data collection methods by individuals 

considered experts in using the GRAIP inventory protocol. Three quality assurance 

plots were surveyed by each crew and by an expert crew in order to ascertain relative 

precision and bias of data collected. Results suggest that the margin of error among 

data collected by the different crews was acceptable and that the data are considered 

usable for analysis. Crews were audited monthly during the survey of a road by an 

expert who corrected procedural mistakes in real time and provided additional training.

Taken collectively, inventory results indicate that roads in the Bear Valley and Elk Creek 

watersheds do result in some hydrogeomorphic impacts and risks to aquatic 

ecosystems. Relative to road sediment production, however, sediment delivery is low. 

Areas of high sediment delivery could be reconstructed or otherwise improved in order 

to drastically reduce road-to-stream sediment transport. GRAIP predictions can be 

used to address the needs of specific road segments and drain points in the design 

phase of future road restoration or road maintenance projects. 

Summary of GRAIP model risk predictions for the Bear Valley and Elk Creek 

watersheds.

IMPACT/RISK TYPE GRAIP PREDICTION

Road-Stream Hydrologic Connectivity 18 miles, 12.5% of total road length

Fine Sediment Production 8,091 tons/year

Fine Sediment Delivery 845 tons/year, 10% of produced road sediment

Upstream Sediment Accumulation 821 tons/year, 10% of produced road sediment

Upstream Sediment Accumulation 

Rate

4.3 tons/mile2/year, 17% of natural reference 

sediment erosion rate

Drain Point Problems 379 drain points, 10% of all drain points

Stream Crossing Failure Risk

 - plug potential 36 stream crossings above average risk, 19% of total

 - fill at risk 3,213 meters3 

 - diversion potential 41 stream crossings, 21% of total

Gully Initiation Risk 22 observed gullies, not considered a substantial risk

Landslide Risk No observed landslides, not considered a substantial

risk
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1.0 Background

The Forest Transportation System is vast and represents an enormous investment of 

human and financial capital. This road and trail network provides numerous benefits to 

forest managers and the public, but can have detrimental effects on water quality, 

aquatic ecosystems, and other resources. There is currently a large backlog of 

unfunded maintenance, improvement, and decommissioning work on National Forest

System Roads (NFSR) and other Forest Roads (FR). Many of these roads and other 

critical Forest Transportation Facilities (e.g., culverts) are nearing or have exceeded 

their life-expectancy. This substantially elevates risks to aquatic resources, especially 

in relation to sediment delivery from roads to streams. 

Within the Bear Valley Creek and Elk Creek watersheds, sediment has been identified 

as the pollutant of concern in four assessment units (AU) which have been proposed to 

be on the Category 4b list in the Idaho Department of Environmental Quality’s (IDEQ)

2010 Integrated Report. Table 1 lists the IDEQ’s AUs of concern in the Bear Valley and 

Elk Creek watersheds, as proposed for the 2010 Integrated Report (see also Figure 1). 

The IDEQ administers state and federal laws which provide a framework for the 

protection of water quality in Idaho. Within this framework, water quality standards have 

been established as parameters for protecting designated beneficial uses of water. The 

beneficial uses of these AUs are currently undesignated. However, cold water, primary 

contact recreation, and secondary contact recreation are defined beneficial uses that 

apply to every waterbody in Idaho, including these AUs.

The IDEQ and the Boise National Forest (BNF) are in the process of preparing a 

demonstration that would justify the Category 4b listing of Bear Valley Creek and Elk 

Creek. This demonstration is to be submitted to the U.S. Environmental Protection 

Agency (USEPA) as part of the 2010 Integrated Report. USEPA regulations recognize 

that alternative pollution control requirements may obviate the need for a TMDL. 

Specifically, assessment units are not required to be included on the Section 303(d) list 

if “other pollution control requirements (e.g., best management practices) required by 

local, State, or Federal authority” are stringent enough to implement applicable water 

quality standards within a reasonable period of time. These alternatives to TMDLs are 

commonly referred to as Category 4b waters.

Table 1. Bear Valley AUs recommended to be Category 4b-listed in IDEQ’s 2010 

Integrated Report (personal communication, Leslie Freeman, IDEQ, 2010).

Assessment Unit

Name

Stream Name Pollutant Length 

(mi)

Beneficial 

Uses

17060205SL012_02a Upper Bear Valley Creek and 

tributaries – 1

st and 2nd order

Sediment 28.86 Undesignated

17060205SL012_05 Bear Valley Creek – 5

th order Sediment, 

Temperature

11.24 Undesignated

17060205SL013_03 Bearskin Creek – 3

rd order Sediment 1.83 Undesignated

17060205SL013_04 Elk Creek – 4

th order Sediment 8.94 Undesignated
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In the Bear Valley and Elk Creek watersheds, like any other watershed where roads 

exist, it is known that roads have some impact on water quality and associated 

beneficial uses, particularly in terms of sediment delivery to streams. However, to what 

degree or where this delivery is occurring is largely unknown or speculative given the 

extensive road mileage in the area. To help complete the Category 4b demonstration, 

the USEPA funded a site-specific road sediment inventory in 2009 for the Bear Valley 

and Elk Creek watersheds. This inventory specifically quantified the extent and location 

of sediment contributions from roads to streams, using the Geomorphic Road Analysis 

and Inventory Package (GRAIP, Prasad et al. 2007, http://www.fs.fed.us/GRAIP).

The GRAIP data collection method provides forest managers with real data that 

captures the extent to which roads affect stream channels. Precise locations where 

sediment delivery is occurring, drainage features are compromised, or road 

maintenance issues need to be addressed to further minimize undesirable aquatic 

impacts from roads were identified during the GRAIP inventory. 

The road density for the Bear Valley and Elk Creek watersheds combined is 0.87 (miles 

of road length per miles squared of area). The area of the watershed is 191.4 square 

miles (495.6 km2or 122,504 acres) and the total road length is 167 miles (267 km). A 

breakdown of road density by sub-watershed is included in Table 2.

Table 2. Road length and density (miles of road length per miles squared of area) for the 

Bear Valley and Elk Creek watersheds by sub-watershed (HUC6).

Sub-watershed Forest Road1

Length (mi)

Unauthorized

Road Length 

(mi)

Total Existing 

Road Length 

(mi) 

Total 

Area 

(mi2)

Road 

Density 

(Rd mi/mi2)

Wyoming 11 2 13 25.7 0.5

Fir Creek 6 0 6 20.2 0.3

Cache 28 9 37 40.0 0.9

Upper Bear Valley 45 10 55 26.3 2.1

Upper Elk 2 2 4 40.8 0.1

Lower Elk 17 4 21 20.8 1.0

Bearskin 22 9 31 17.6 1.7

Combined Total 131 36 167 191.4 0.9

All roads in the Bear Valley and Elk Creek watersheds were targeted in the road 

inventory. However, due to time and resource constraints certain roads were given 

priority based on assessments made in the field by a crew leader. All 131 miles (210 km) 

of Forest Roads (including open, closed, or otherwise designated roads) were prioritized 

and successfully surveyed. Most unauthorized roads (user-created or otherwise 

unclassified roads) were prioritized, but not all were surveyed. The field crew leader 

 

1

Forest Roads include all National Forest System Roads and other Forest Roads which have been 

authorized by a legally documented right-of-way held by Valley County (36 CFR 212.1). Forest Roads do 

not include unauthorized roads.
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visited each unauthorized road and deemed it a priority based on various characteristics 

including: lower slope position, close proximity to a stream channel, observed stream 

connection and active sediment delivery between drain points and a channel, active road 

surface erosion, little vegetation on road surface or in flow paths, concentrated water flow, 

drainage feature types, existence of drainage problems, and use. As stated in the Quality 

Assurance Project Plan (QAPP), a feature will no longer be considered a road when it 

does not move water along its surface, no longer has stream crossings, and is not located 

in a position where it can interact with the stream channel (Black et al. 2009).

Over a course of four weeks during the summer of 2009, Bear Valley field crews mapped 

and collected data on a total of 146 miles (235 km) of roads (see Table 3). Precisely 

3,175 individual road segments and 3,826 unique drain points comprise these 146 miles.

These road segments and drain points make up the entirety of the data that are analyzed 

in this report.

Up to 21 miles (34 km) of unauthorized roads were not surveyed. The decision to forego 

the survey of these roads was made based on the previously mentioned prioritization 

criteria which indicated limited impact. Forest GIS files (using aerial photography) 

estimate approximately 36 miles (58 km) of unauthorized roads in the Bear Valley and Elk 

Creek watersheds. However, the exact number of unauthorized roads within the 

watersheds is unknown as many of them are difficult to physically locate (due to 

overgrowth of vegetation or no access). Therefore, 21 miles of unauthorized roads may 

be more than double the actual miles of roads not surveyed due to discrepancies among

GIS data and field observations. 

Table 3. Length of road inventoried and surveyed by field crews by road type2. 

Road Type Total Existing 

Length (mi) 

Total Length 

Surveyed (mi)

% Total Length 

Surveyed

Forest Roads 131 131 100%

Unauthorized Roads 36 15 42%

Combined Total 167 146 87%

2.0 Study Objectives

GRAIP is designed to assess the geomorphic and hydrologic activity and risk of roads as 

well as the physical condition of roads and their associated drain points. Field crews 

surveyed roads in the Bear Valley and Elk Creek watersheds in an effort to better 

 

2

All figures except for Combined Total Length Surveyed may not be accurate as GIS data and field

observations did not always align. Many unauthorized and a few NFS road segments displayed in BNF 

road shapefiles did not match existing roads on-the-ground. Often, the length and shape were drastically 

different from what was indicated on maps. Some roads displayed on BNF road layers likely never 

existed or no longer exist as such due to re-growth of vegetation and results of previous restoration work 

rendering a road no longer identifiable as such.
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understand the overall effect of roads on key watershed processes. Specifically, the 

project is intended to address the following questions.

1. What is the existing level of fine sediment delivery from roads to streams in Bear 

Valley?

a. How does the contributed sediment from roads compare to natural 

reference sediment levels?

2. Where are the locations of highest sediment delivery from roads to streams?

a. Can these sites be reconstructed to eliminate or minimize delivery?

3. What unknown geomorphic or hydrologic issues exist in Bear Valley’s road system 

that could help forest managers make decisions and plan more effectively?

3.0 Methods

The Geomorphic Roads Analysis and Inventory Package (GRAIP) was used to 

inventory and model the risk profile of each of the road segments included in the study. 

The GRAIP system consists of a detailed, field-based road inventory protocol combined 

with a suite of geographic information system (GIS) models. The inventory is used to 

systematically describe the hydrology and condition of a road system using Geographic 

Positioning System (GPS) technology and automated data forms (Black, Cissel, and 

Luce 2009). The GIS models use these data to analyze road-stream hydrologic 

connectivity, fine sediment production and delivery, upstream sediment accumulation, 

stream sediment input, shallow landslide potential with and without road drainage, gully 

initiation risk, and the potential for and consequences of stream crossing failures. 

Detailed information about the performance and condition of the road drainage 

infrastructure is also supplied. The inventory was conducted in accordance with the 

Quality Assurance Project Plan (QAPP) developed in cooperation with the USEPA and 

the RMRS (Black et al. 2009). A summary of QAPP results can be found in Section 6.0 

of this report.

 

Photo 1. Field crew members collecting data on a stream crossing (left) and collecting 

GPS points for a drainage feature (right).
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4.0 Monitoring Location

The 122,500-acre (191 square miles) Bear Valley area is located in the mountains of 

west-central Idaho. The watershed is approximately 100 miles northeast of Boise, 25 

miles northeast of Lowman, and about 20 miles northwest of Stanley. It lies wholly in 

Valley County at the southeastern margin of the Salmon River Mountains and southern 

border of the Frank Church River of No Return Wilderness Area. The gentle, highaltitude slopes of Bear Valley are home to meadows, wetlands, and meandering 

streams, which provide essential habitat for multiple fish and wildlife species. Among 

these are three endangered fish species including Chinook salmon, steelhead, and bull 

trout as well as other native species such as westslope cutthroat trout, elk, wolves, and 

others. Plant species include stands of lodgepole pine, Douglas fir, and whitebark pine 

as well as sensitive wetland species. 

Bear Valley is located in the headwaters of the Middle Fork Salmon River and includes 

two 5th HU (hydrologic unit) watersheds, Bear Valley Creek and Elk Creek. Bear Valley 

Creek flows approximately 20 miles to its confluence with Marsh Creek, where they both 

form the start of the Middle Fork Salmon River. At its widest, the watershed is about 14 

miles wide, and it is about 20 miles long. Water tempreatures within the basin are cool

and salmonid spawning is a major factor in resource management of the area.

The Bear Valley area contains landforms somewhat atypical of those representative of 

the central mountains of the granitic Idaho batholith. The terrain in the watershed is 

unique in that it exhibits realatively gentle topography compared to adjacent 

watersheds, such as the South Fork Payette and the Deadwood, which are steep and 

highly dissected. As a whole, the watershed is typified by heavily-forested, 

mountainous terrain with a relatively high base elevation of about 6,200 feet. Cape 

Horn Mountain is the highest point in the watershed at nearly 9,600 feet and lies just 

south of the mouth of Bear Valley Creek. Mountains are slightly to strongly dissected, 

with wide valleys and meadow basins, some exhibiting laucustrine deposits. Most of 

the watershed has been glaciated and much of the surface is veneered with glacial 

outwash and associated quaternary deposits. The higher mountain peaks and ridges of 

the divide are pronounced, but not sharp and broken; rather, they are somewhat 

rounded or edgeless and heavily forested.

The watershed is divided nearly down the middle by the broad, main, U-shaped, southto-north trending Bear Valley Creek valley. Valley sides rise moderately steep to 

steeply, but rarely precipitously, to the upland mountains. Other dominant stream 

valleys (e.g. Elk Creek, Bearskin Creek, and some other tributaries) are U-shaped as 

well, and headwater tributaries are only moderately incised. Streams within the Ushaped valleys typically have a gradient of less than 1% with seasonally high water 

tables and high sinuousity.

Mean annual precipitation in the watershed ranges between 25 and 60 inches, 

depending on elevation. Seventy-five percent of the annual precipitation falls from 
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November through April. Snow pack present on April 1 accounts for 60% of the mean 

annual precipitation. Higher elevations often retain snow pack well into early summer.

The entire watershed is National Forest System land. Most is administered by the 

Lowman Ranger District of the BNF, while some area in the northeastern part of the 

watershed is administered by the Middle Fork Ranger District of the Salmon-Challis 

National Forest. Portions of National Forest System Roads 568 and 579 are subject to 

the majority of traffic use in the watershed, most of which is associated with the 

wilderness access and whitewater recreation. Users drive these roads to obtain access 

to the Middle Fork Salmon River and the Frank Church River of No Return Wilderness 

Area. The Middle Fork Salmon River is administered by the Salmon-Challis National 

Forest. (Shapiro et al. 2000)

Bear Valley roads vary in appearance and drainage features, but most have a surface 

consisted of native material. The original construction standards of arterial roads such 

as FR 582, FR 579, and FR 563 included a crowned surface with an inboard ditch and 

diffuse drainage off the fillslope. Over time and with repeated grading and 

maintenance, these high-use roads often have an outside berm with frequent nonengineered drainage features where water has cut through the berm and off the road 

prism. The north end of the Bearskin road (FR 563) had frequent, effective, engineered 

berm drains that acted like lead off ditches, diverting flow away from the road and 

streams. The construction style for upper-slope collector and “spur” or local roads was 

generally at a lower standard. Some of these roads would have a ditch with frequent 

culverts, while others would drain through broad based dips or water bars. Many roads 

in Bear Valley pass through vast meadows and wetland areas amidst flat terrain. Such 

roads did not always have clearly defined flow paths or stream connection. Many 

sensitive fish, wildlife, and plant habitat areas are within the immediate vicinity of roads

in Bear Valley.

Mid- to upper-slope roads at higher elevations and in the south end of the watershed 

generally had steeper gradients and were constructed with various periodic drainage 

features. Concentrated flow and clearly defined flow paths were more common in 

steeper terrain. Many unauthorized, closed, or decommissioned roads existed in these 

upper-slope areas which drained largely by means of water bars or diffuse drainage. 

The usage and maintenance level of upper-slope roads in the Bear Valley watershed is 

generally lower than that of lower-slope roads. 

Live stream crossings were especially frequent on lower-slope roads, although they did

exist at all slope positions. The watershed has relatively flat topography with limited 

steep terrain, so stream crossing fills, cutslopes, and fillslopes were typically small. 

Roads often run parallel to stream channels, especially at lower elevations in the 

watershed (e.g. FR 582 on Bear Valley Creek, FR 563 on Bearskin Creek, and FR 579 

on Elk Creek). Data suggest, however, that the majority of roads in Bear Valley pose 

little to no risk to water quality and associated beneficial uses.
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Figure 1. Bear Valley area map including roads surveyed.
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5.0 Results

GRAIP inventory and modeling tools were used to characterize the following types of 

impacts and risks:

 Road-stream hydrologic connectivity

 Fine sediment production and delivery

 Upstream sediment accumulation

 Drain point condition

 Stream crossing failure risk

 Gully initiation risk

 Landslide risk

5.1 Road-stream Hydrologic Connectivity

Roads can intercept shallow groundwater and convert it to surface runoff, particularly in 

steep terrain, resulting in local hydrologic impacts when that water is discharged directly 

to channels (Wemple et al. 1996). Additional runoff is also produced from the 

compacted road surface. Basin-scale studies in the Oregon Cascades suggest that a 

high degree of integration between the road drainage system and the channel network 

can increase peak flows (Jones and Grant 1996). 

GRAIP calculates the hydrologically-connected portion of the road using the field 

assessment of drain point connection and a road segment flow routing system. The 

flow path below each drain point is followed until evidence of overland flow ceases or 

the flow path reaches a channel. A total of 18 mi (29 km) out of the 146 mi (235 km)

of surveyed roads in Bear Valley (12.5%) were hydrologically connected to a stream. 

5.2 Fine Sediment Production & Delivery

Fine sediment production for a road segment (

E

) is estimated based on a base erosion 

rate and the properties of the road (Luce and Black 1999), as shown below. 

E B L S V R

B

is the base erosion rate3(kg/m)

L

is the road length (m) contributing to the drain point

S

is the slope (m/m) of the road segment

V

is the vegetation cover factor for the flow path

R

is the road surfacing factor

 

3

For this analysis, a base erosion rate of 210 kg/m/yr of road length per unit of slope was assumed. This 

figure is based on BOISED model base rates for road sediment production where maintained, heavy use 

roads are present (Reinig et al. 1991). The base rates were developed from Zena Creek (in the nearby 

South Fork Salmon River drainage) in erosion studies conducted by Megahan. Further work could 

determine if this rate is appropriate for this climate, geology and road system. 
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Delivery of eroded sediment to the channel network is determined by observations of 

each place that water leaves the road. Each of these drain points is classified as 

delivering, not delivering, or uncertain. No estimate of fractional delivery is made 

because there is insignificant hillslope sediment storage in locations where there is a 

clear connection to the channel under most circumstances. For this analysis, uncertain 

observations were treated as delivering. GRAIP identifies drain points at which 

sediment is delivered to a channel and estimates how much sediment is delivered to the 

channel at a given drain point in kilograms per year.

Drain Point Analysis

Delivery of fine sediment occurs through a mix of road drainage features including ditch 

relief culverts, non-engineered drain points, stream crossings and others. In Table 4, 

sediment delivery is broken out by drain type to assess their effectiveness in preventing 

sediment from entering the channel. A total of 3,826 drain points were documented, 

414 of which (11%) were hydrologically connected to stream channels. However, only 

282 of these stream-connected drain points (7% of all drain points) were observed to be 

actively delivering sediment to a channel (see Table 5). These points deliver 845 

tons/year (767 tonnes/yr) of sediment4, or 10% of the 8,091 tons/year (7,340 tonnes/yr)

of sediment produced by the road surfaces and ditches. Existing drain points are 

always recorded when spotted in the field, but field crews may determine that a drain 

point is not actively receiving any water flow from the road based on observed evidence.

In this case, the drain point is noted to be an “orphan” drain point and no flow or 

sediment is routed to it.

There are eight different types of drain points defined in the GRAIP model: broad based 

dips, diffuse drainage, ditch relief culverts, lead off ditches, non-engineered drainage 

features, stream crossings, sumps, and water bars. The three drain types which 

delivered the most sediment to a stream channel are stream crossings, non-engineered 

drains, and ditch reliefs with sediment deliveries of 279.7 tons/year (253.7 tonnes/yr), 

210.1 tons/year (190.6 tonnes/yr), and 193.0 tons/year (175.0 tonnes/yr), respectively. 

This means that 33% of all 845 tons (766.6 tonnes) of road sediment delivered to a 

stream annually is delivered directly to a stream crossing at a road/stream intersection. 

Similarly, 25% of all sediment delivered leaves the road prism at a non-engineered drain 

and 23% at a ditch relief culvert. The other five drain types deliver considerably less 

sediment to the stream channels, each at less than 7% of total sediment delivered (see 

Figure 2). 

 

4 Of the 845 tons/year (766.6 tonnes/yr) of delivered road sediment included in these figures, 24.3

tons/year (22 tonnes/yr) are delivered to streams outside of the Bear Valley and Elk Creek watersheds.

This difference is accounted for by four drain points recorded in the survey near watershed boundaries,

three of which are on NFSR 569 near the summit of Whitehawk Mountain and the other on NFSR 502A 

near the headwaters.
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Table 4. Summary of sediment production and delivery at drain points. 

Drain Type Count Total Sediment 

Production (kg/yr)

Total Sediment 

Delivery (kg/yr)

% Sediment 

Delivery

% Length5

Connected

Broad Based Dip 488 1,274,729 50,110 4% 4%

Diffuse Drain 1,077 1,458,626 53,554 4% 2%

Ditch Relief Culvert 388 1,250,319 175,043 14% 15%

Lead Off Ditch 90 270,864 20,549 8% 7%

Non-Engineered 501 1,019,218 190,590 19% 20%

Stream Crossing 191 253,699 253,699 100% 100%

Sump 14 6,903 0 0% 0%

Water bar 1,077 1,806,088 23,027 1% 2%

All Drains 3,826 7,340,447 766,571 10% 11%

Figure 2. Distribution of total sediment delivered by drain type.

Reasons behind the large difference between the three highest producers and the other 

five may be that many stream crossings, non-engineered drains, and ditch reliefs exist

on lower-slope roads that are close to a stream channel. Many of the lower 

maintenance level, unauthorized, less-travelled, decommissioned, or closed roads are 

located far from streams, thickly covered by vegetation, or have been closed to traffic 

for a number of years. Such roads are often mid- to upper-slope and are drained by 

closely spaced water bars or broad based dips, or they drain diffusely. Consequently, 

 

5

ELength was used to calculate this figure. It is the effective length of road that was draining to a

particular drain point. If a road segment has two distinct flow paths assigned to different drain points, the 

ELength for that drain point will be equal to one half of the total length of the corresponding road

segment.
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these low-maintenance, low-traffic roads tend to deliver less sediment to the stream 

channel. Further analysis could be done using GRAIP data to validate or reject these 

observations and to better understand other variables surrounding the effectiveness of 

different drain types in a given location. Geographical location of drain types, slope 

position, the surface type of adjacent road segments, or other factors that play into 

sediment production and delivery could be investigated.

The drain types with the highest percentage of features that actively deliver sediment to 

a stream channel are stream crossings, ditch relief culverts, and non-engineered drains

(see Table 5). Any road segment draining directly to a live stream crossing is 

automatically going to be delivering its produced sediment to that stream. Fifty-one 

percent of stream crossings in Bear Valley are actively delivering sediment to streams. 

The remaining 49% of stream crossings in Bear Valley are “orphan” drain points, 

meaning these do not drain road surface water and sediment which would pass through 

the culvert directly. Mitigations to prevent continued direct sediment delivery at stream 

crossings may include establishing ground cover vegetation to filter sediment before it 

enters the creek or adding additional drainage on the road on either side of the stream 

crossing to prevent direct delivery. Sediment delivery from non-engineered drains could 

likely be mitigated through road maintenance, such as removing the outside berm and 

re-establishing diffuse drainage off the fillslope. Ditch relief culverts delivering sediment 

may require the installation of more frequent road drainage features up road in order to 

decrease the volume and energy of water flowing down the road or ditch and through 

the pipe.

Table 5. Summary of drain point connectivity to streams and observed active sediment 

delivery at drain points (i.e. orphan drain points may be connected to the stream, but do

not actively drain water or sediment from the road surface).

Drain Type Count Drain 

Points 

Connected 

to Stream

% of Drain 

Points 

Connected

Drain Points 

Actively Delivering 

Sediment to 

Stream

% of Drain points 

Actively Delivering 

Sediment to 

Stream

Broad Based Dip 488 23 5% 18 4%

Diffuse Drain 1,077 22 2% 19 2%

Ditch Relief Culvert 388 67 17% 54 14%

Lead Off Ditch 90 6 7% 6 7%

Non-Engineered 501 87 17% 72 14%

Stream Crossing 191 191 100% 98 51%

Sump 14 0 0% 0 0%

Water bar 1,077 18 2% 15 1%

All Drains 3,826 414 11% 282 7%

The precise percentage of all drain points contributing 100% of the sediment to the 

stream system in Bear Valley is 7.37%. Figure 3 displays the distribution of these drain 

points contributing sediment on a cumulative scale. The data confirm that 1.2% of all

drain points contribute 50% of all the sediment. This is equal to a total of 46 drain 

points causing half of the problem. Furthermore, 116 drain points (3%) account for 80% 
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of the sediment, 157 (4.1%) for 90% of the sediment, and so on. These figures suggest 

a feasible amount of maintenance and road improvement could drastically diminish the 

impact of roads on Bear Valley Creek and its tributaries.

Figure 3. Percentage of the total amount of fine sediment delivered to a stream 

channel explained by the percentage of the total quantity of drain points.

Areas of High Sediment Delivery to Streams

Sediment delivery from roads in Bear Valley appears to be dispersed throughout the 

watershed (Figure 4). Specific locations where clusters of drain points with high 

sediment delivery exist are few with varying characteristics. Initial analysis suggests 

that the data do not show patterns of consistently similar characteristics among 

separate areas of high sediment delivery. One observation made in reviewing GRAIP 

data is that stream delivery often occurred at or near live stream crossings. When a 

road bends around a draw where a stream is present and water drains on or near that 

bend, road sediment regularly reaches the stream, whether at the stream crossing or 

another drainage feature.

Sediment delivery is also common along roads that run parallel to nearby streams. In 

the Idaho batholith, the median transport distance below ditch relief culverts was found 
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to be 53 meters in a previous study by Megahan and Ketcheson (1996). In Bear Valley, 

207 of the 282 drain points actively delivering sediment to a stream (73%) were within 

53 meters of a channel. These drain points contribute 572.9 of the 845 tons/year (519.7

of the 766.6 tonnes/yr) or 68% of the total connected sediment. A total of 680 more 

drain points that were not actively delivering road sediment to the stream also fell within 

53 meters of a channel.

Drain points draining extended lengths of road, if connected to the stream, are likely to 

deliver a large quantity of sediment. Figure 4 shows a map of the top 24 sedimentdelivering drain points throughout the entire Bear Valley watershed. These 24 drain 

points deliver a total of 285.5 tons/year (259 tonnes/yr) of sediment to streams, which 

equals 34% of the total amount of road sediment reaching streams. The average length

of road draining to the top 24 sediment-delivering drain points was 184 meters 

compared to an overall average of 61 meters per drain point. All but one of these

features were within 200 meters of a stream crossing or a stream running parallel to the 

road and 14 were within 53 meters. Shortening the length between drain points may 

reduce the amount of sediment produced within these 24 drain points.

A map of the road surface sediment delivery and the accumulated sediment delivered 

through drain points is shown for portions of NFSR 569, FR 563, NFSR 579, FR 579,

FR 582, and NFSR 502 (Figure 5). These road segments have relatively high levels of 

stream connectivity and sediment delivery.

 b) 

a) c) 

Photo 2. Photos of high delivery drain points. a) Gully at outlet of highest delivering 

drain point in the entire basin, located on NFSR 569. b) Sack Creek stream crossing on 

FR 582, one of top 24 highest delivering drain points in basin. c) Eroded and 

dilapidated stream crossing of Bearskin Creek on NFSR 563C1.
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Figure 4. Map of all drain points which are actively delivering sediment to a channel. 

The top 24 drain points in terms of highest annual sediment delivery are emphasized.
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Figure 5. Maps of fine sediment delivery to channels by road segment and drain point. 

As indicated in the legend below, the road line is colored to indicate the predicted mass 

of fine sediment that is produced on the road and delivered to the channel. The size 

and color of the circle indicate the accumulated mass of sediment delivered through 

each drain point. All red circles indicate a drain point that is actively delivering sediment 

to streams while small white points represent a drain point not connected to the stream

(see Legend below). See Table 6 for length of sediment-contributing road segments 

and amount of sediment delivery for each displayed road.

 

A) NFSR 569 leading to 

Whitehawk Lookout 

has a steeper grade 

(9% average for 

displayed segment) 

compared to most Bear 

Valley roads and has

the highest sediment 

delivery rate out of any

stretch of road in the 

entire watershed (see 

Table 6). 
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B) FR 582 C) FR 563 D) NFSR 579

 

Bear Valley Road, FR 582 (B), at the headwaters of Bear Valley Creek drains large 

quantities of sediment to streams. This segment of the Bearskin Road, FR 563 (C), has 

frequent drain points that are connected to a stream. Along Fir Creek from Cape Horn 

Summit to the cutoff for the Fir Creek Campground, NFSR 579 (D) passes through a 

burn area and exhibits concentrated flow and frequent sediment delivery. The NFSR 

579 culvert crossing of Fir Creek was upgraded to a bridge to allow aquatic organism 

passage in 2009 after the GRAIP survey was completed. The project included a new 

ditch lined with rock. The 

project was designed to 

significantly reduce the 

sediment delivery at this stream 

crossing. 

E) FR 579 near the 

confluence of Elk Creek 

and Bear Valley Creek 

runs very close to the 

banks of Elk Creek. The 

two delivering drain points 

nearest Elk Creek, and 

their adjacent road 

segments, represent 

diffuse drainage and not 
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concentrated flow. Although well-defined 

flow paths and drain points did not occur 

on this road segment, evidence of fine 

sediment reaching the channel was 

observed by the field crew. It is unlikely 

that any improvements, short of road realignment) could mitigate sediment 

delivery along this road segment because 

of the close proximity between the road 

and the stream and the road is already 

draining diffusely.

F) NFSR 502 has multiple stream crossings, 

many of which are directly receiving 

sediment. This portion of NFSR 502 has 

three stream crossings. The streams in 

this image are unnamed streams in the 

headwaters of Bear Valley Creek.

Table 6. Sediment delivery values for road segments displayed in Figure 5 including 

percentage of total annual sediment delivery for the entire basin.

Forest Road Length of Road 

Delivering 

Sediment to 

Stream (mi)

Sediment 

Delivered to 

Stream 

(tons/yr)

Sediment 

Delivered to 

Stream 

(tonnes/yr)

% of Total 

Annual 

Sediment 

Delivery

NFSR 569 0.75 121.6 110.3 14%

FR 582 0.70 41.7 37.8 5%

FR 563 1.13 70.4 63.9 8%

NFSR 579 (Fir Creek) 1.68 64.9 58.9 8%

FR 579 (Elk Creek) 0.82 30.1 27.3 4%

NFSR 502 0.61 53.9 48.9 6%

Combined Total 5.69 382.6 347.1 45%

Road Segment Analysis

Sediment Production on roads in the Bear Valley area occurs at various rates. As 

previously mentioned, the total amount of fine sediment production from roads is 8,091 

tons/year (7,340.4 tonnes/yr). Figure 6 displays the relative sediment production rates 

on roads throughout the Bear Valley and Elk Creek watersheds. As would be expected, 

roads with steeper gradients produce the most sediment. For example, NFSR 569 and 

NFSR 583 appear to be high sediment producers. Given the high level of fine sediment 

delivery from NFSR 569, it would be assumed that the production rate is also high, 

which is estimated to be 537.5 tons/year (487.6 tonnes/yr) or 7% of the total. NFSR 

583 (Photo 3) delivers very little sediment to streams, yet its production rate is among
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the highest in the basin at 736.1 tons/year (667.8 tonnes/yr) or 9% of total. Sediment 

production is also relatively high where NFSR 579 runs alongside Fir Creek and on 

much of NFSR 502. 

Figure 6. Bear Valley area map of relative sediment production rates by road segment.
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Photo 3. Photo of a road segment of NFSR 583 leading to Bear Valley Mountain 

Lookout. Although, this road delivers very little sediment, much of the road is badly 

eroded and yields high sediment production rates.

The length and slope of a road segment are both variables in the equation GRAIP uses 

to calculate sediment production. Longer road lengths and steeper road gradients yield 

higher sediment production values. Recorded road segments had an average length of 

74 meters with a range of 7 to 950 meters and a median of 57 meters. The average 

slope was 5.1% with a range of 0% to 26% and a median of 4.3%. Of the total road 

length, 12.2 miles (8%) have a slope of 0% and 51 miles (35%) have a slope of less 

than 2%.

The fraction of sediment delivered can be quantified in terms of percentiles of road 

length. Figure 7 displays the distribution of individual road segments contributing fine 

sediment to a channel by road length. Of the 146 miles (235 km) of total road length, 

4.5 miles (7.2 km) are generating 50% of the sediment delivered to streams. That 

means approximately 3% of the road length surveyed is generating half of the road 

sediment load found in Bear Valley streams. This includes many of the road segments 

displayed in Figure 5. Less than 6% (8.6 mi or 13.8 km) of road length generates 80% 

of sediment delivered, 7.6% (11.1 mi or 17.9 km) generates 90%, and 12.5% (18.3 mi or 

29.4 km) generate 100% of sediment delivered. 

These data suggest that fine sediment delivery from roads could be substantially 

reduced with the implementation of a feasible amount of road improvement work. The 

GRAIP data could be used to identify the specific location of sediment delivering road 

segments. Various road improvements could be made to these segments to decrease 

or eliminate sediment delivery including constructing additional drainage features or resurfacing roads.
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Figure 7. Percentage 

of the total amount of 

fine sediment delivered 

to a stream channel 

explained by the 

percentage of the total 

road length.

The total number of road segments is not meaningful for many analytical puposes 

because each road segment varies in length and other characteristics. However, it is 

useful to note the number of recorded road segments that would require attention or 

repair for management purposes. Not all problematic road segments are adjacent to 

each other, which may necessitate detailed logistical planning for the implementation of 

project work. Figure 8 demonstrates the relationship between the percentage of total 

sediment delivery to streams and the percentage of all road segments contributing 

sediment. Out of a total of 3,175 individual road segments, 338 (11%) are delivering 

sediment to streams. Of these segments, 59 (1.9%) are contributing 50% of the 

sediment, 145 (4.6%) account for 80% of the sediment, and 198 (6.2%) generate 90% 

of delivered sediment.

Figure 8. Percentage 

of the total amount of 

fine sediment delivered 

to a stream channel 

explained by the 

percentage of the total 

quantity of road 

segments.
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The dominant surface type found on Bear Valley roads was native material (see Figure 

9). Many decommissioned, closed, or otherwise lightly-used roads were found to have 

grasses and herbaceous vegetation growing abundantly on the road surface. Small 

lengths of closed or decommissioned roads had significant amounts of brush growing 

on the surface. A short segment of NFSR 568 to Dagger Falls was previously paved to 

reduce sediment delivery in this important Chinook spawning reach adjacent to the Bear 

Valley Creek crossing. Native surfaced roads produce considerably more sediment 

than other surface types, with paved roads producing the least amount of sediment.

The GRAIP model calculates that native surfaced roads produce 25 times the sediment 

of paved roads, and 5 times that of any other surface type.

Figure 9. Distribution of road surface types found in Bear Valley by road length.

Vegetation in the flow path is also included in the equation when calculating sediment 

production on a road segment. Vegetation can slow flow velocity, impede erosion and 

sediment transport, and allow for filtering or sediment storage. GRAIP significantly 

reduces its prediction of sediment production when vegetation in the flow path is 

recorded to be greater than 25%. Field data reported that 27% of the total flow path

length was observed to be more than 25% obstructed by any sort of vegetation. The 

remaining 73% of total flow path length in the watershed had 25% or less vegetated 

cover, resulting in no reduction of sediment production estimates. Flow paths on the 

road surface are typically not vegetated. Flow paths in a ditch can be vegetated, but 

frequently are not due to ditch cleaning during road maintenance activities.

5.3 Upstream Sediment Accumulation

GRAIP generates a stream network that is segmented at each channel confluence and 

each road/stream intersection. For each stream segment, the model calculates the 

accumulated road sediment load at the downstream end of that segment, including the 
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total accumulated sediment from upstream stream segments (Figure 10). The total 

predicted amount of accumulated road sediment found in the stream segment nearest 

to the mouth of Bear Valley Creek was 820.7 tons/year (744.5 tonnes/yr). The sediment 

load was greatest after the confluence of Bear Valley and Elk Creeks. 

Figure 10. Bear Valley area map of stream sediment accumulation from roads.
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The majority of stream sediment accumulation (74%) is produced by roads which drain 

to Bear Valley Creek and its tributaries, a total of 609.0 tons/year (552.5 tonnes/yr). 

From this amount 532.5 tons/year (483.1 tonnes/yr) or 65% of total sediment 

accumulation originates from above the confluence with Elk Creek. Cache Creek 

contains 52.0 tons/year (47.2 tonnes/yr) at its mouth. Elk Creek and its tributaries carry 

211.7 tons/year (192.1 tonnes/yr) of road sediment (26% of total) prior to converging 

with Bear Valley Creek. 

The stream network that the GRAIP model produced was based on both an existing 

GIS stream layer and a predicted stream layer from the TauDEM model. The total 

stream length of the stream layer produced by GRAIP was 582 miles (937.1 km). Road 

sediment is found in 134 miles (215.4 km) of streams, or 23% of the total stream length. 

Streams with no sediment load are generally first and second order streams located at 

higher elevations or in small, isolated drainages. These road sediment-free streams 

(77% of the total stream length) flow at locations that are either above roads, where 

roads do not exist, or where roads do not actively deliver sediment to a channel. Table 

7 displays the accumulated stream sediment values for the basin by sub-watershed.

Table 7. Stream sediment load values by sub-watershed (HUC6).

Sub-watershed Total 

Accumulated 

Road 

Sediment in 

Stream 

(kg/yr)

Total 

Accumulated 

Road 

Sediment in 

Stream 

(tons/yr)

Accumulated 

Road 

Sediment 

Rate 

(tons/mi2/yr)

Total 

Accumulated 

Natural 

Sediment in 

Stream6

(tons/yr)

Accumulated 

Reference 

Sediment 

Erosion 

Rate6

(tons/mi2/yr)

Road 

Density 

(Rd 

mi/mi2)

Wyoming 8,400 9.3 0.4 540.6 21 0.5

Fir Creek 60,974 67.2 3.3 605.3 30 0.3

Cache 94,441 104.1 2.6 879.3 22 0.9

Upper Bear Valley 388,658 428.4 16.3 788.3 30 2.1

Upper Elk 3,150 3.5 0.1 979.4 24 0.1

Lower Elk 48,336 53.3 2.6 602.9 29 1.0

Bearskin 140,574 154.0 8.8 474.6 27 1.7

Combined Total 744,532 820.7 4.3 4,870.4 25.5 0.9

GRAIP calculates the accumulated road sediment load for each stream segment 

specific to the total area of land draining to it. The specific accumulated sediment load 

figure of the stream segment at the mouth of a channel will indicate the value for the 

entire drainage of that channel. At the mouth of Bear Valley Creek the specific 

accumulated sediment load is 4.3 tons/mi2/yr (1.5 Mg/km2/yr). The total predicted 

stream sediment load from natural erosion of undisturbed hillslopes within the Bear 

Valley and Elk Creek watersheds is approximately 4,870 tons/yr. This yields a

reference sediment erosion rate of 25.5 tons/mi2/yr (8.9 Mg/km2/yr). Therefore, road 

 

6

The background sediment erosion rates used for this comparison were derived using the BOISED 

model which calculates sediment erosion rates by land type. These figures were copied from the Bear 

Valley Watershed Analysis (Shapiro et al. 2000).
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sediment accumulation essentially increases the natural stream sediment accumulation 

rate by 17%. Disturbances such as wildfire, logging, or roads are not accounted for in 

this reference sediment rate. Such disturbances as wildfire will elevate the indicated 

natural sediment erosion rate, especially in this basin which has experienced multiple 

wildfires in recent years. In fact, 59% of the total area (113 mi2) of the basin has burned 

since 1985. 

In comparing road density to the accumulated road sediment rate (Figure 11), where 

higher road densities exist, higher accumulated road sediment rates generally occur as 

well. However, this is not true for all sub-watersheds in the basin. The Fir Creek and 

Upper Bear Valley sub-watersheds have higher accumulated road sediment rates in 

comparison to their road densities than do most other sub-watersheds, whereas the 

Wyoming and Upper Elk sub-watersheds have lower ratios. Upper Elk measures 

extremely low in both categories, which would be expected as it has a large area and 

very little road length. Although the sample size of sub-watersheds for this basin is too 

low to draw out any real statistical correlation, the two sub-watersheds with the highest 

road density, Bearskin and Upper Bear Valley, also have the highest accumulated road 

sediment rates. Many other variables, such as terrain and geology, may also be related 

to this phenomenon.

Figure 11. Road density versus accumulated road sediment rate by sub-watershed.
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5.4 Drain Point Condition

The GRAIP inventory involves an assessment of the condition of each drain point and a 

determination of how well it is performing its intended function. Problems with drain 

point condition are pre-defined for each drain type. Broad based dips are considered to 

be in poor condition if they are insufficiently outsloped and pond water on the road. 

Culverts are defined to be in poor condition if they have more than 20% occlusion of the 

inlet by sediment, substantial inlet crushing, significant rust, or flow around the pipe. 

Lead off ditches are considered problematic if they have excess deposition or are 

gullied. Non-engineered features are almost always a problem due to a blocked ditch, a 

gully, a broken outside berm, or a diverted wheel track. Stream crossings are 

considered a problem if they are blocked by sediment or wood, crushed or rusted 

significantly, incising, scouring or loosing much water from flow around the pipe. Sumps 

are a problem if they pond water on the road surface or cause fill saturation. Water bars 

that are damaged, under sized, or do not drain properly are defined as problematic. 

Diffuse drains (outsloped roads) are rarely observed to have drain point problems. 

a) b) 

c) d) 

Photo 4. Examples of drain point condition problems including: a) erosion at a broad 

based dip, b) a rusted and damaged ditch relief culvert, c) a stream crossing with flow 

around and possibly over the pipe, and d) a non-engineered feature where the stream is 

cutting into the road fill material.
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In Bear Valley, non-engineered features were observed to have the highest rate of 

problems (58%), while lead off ditches or berms and diffusely drained roads were least 

likely to have problems (Table 8). Any drain point that causes erosion of fill material at 

its outlet is considered problematic. Drain point features that most often eroded fill 

material at the outlet or away from the fillslope were non-engineered features and water 

bars (both at 4%).

Table 8. Drain point condition problems and fill erosion below drain points.

TOTAL CONDITION PROBLEMS FILL EROSION

Drain Type Count Count Percentage Count Percentage

Broad Based Dip 488 23 5% 6 1%

Diffuse Drain 1,077 0 0% 2 0.2%

Ditch Relief 388 48 12% 11 3%

Lead Off 90 1 1% 0 0%

Non-Engineered 501 291 58% 19 4%

Stream Crossing 191 15 8% 5 3%

Sump 14 2 14% 0 0%

Water bar 1,077 76 7% 45 4%

Total 3,826 379 10% 88 2%

Features other than actual drain points were often observed and recorded during the 

field inventory on Bear Valley roads. Field crews are trained to observe and record any 

existing gates, ends of roads, gullies, landslides, photo points, road closure features, 

and road hazards are among these additional features. Given that these features are 

not the focus of the GRAIP model, it is likely that more of these features exist than what 

was recorded. Of these additional collected features, some were noted to be damaged, 

hazardous, or in need of maintenance or attention. Two out of seven gates were noted 

to be damaged or dysfunctional. Four road hazards were recorded where various 

circumstances pose a risk to vehicles or people using the road.

5.5 Stream Crossing Failure Risk

In addition to contributing fine sediment to streams through surface erosion, stream 

crossings may fail catastrophically when blocked and deliver large sediment pulses to

stream channels. Stream crossing failure risks were assessed using the Stream 

Blocking Index (SBI, Flanagan et al. 1998). The SBI characterizes the risk of plugging 

by woody debris by calculating the ratio of the culvert diameter to the upstream channel 

width and the skew angle between the channel and the pipe inlet. 

Field crews recorded a total of 191 stream crossings in Bear Valley. Of these stream 

crossings, 45 (24%) did not have a round culvert pipe present and were not included in 

the SBI calculations. These crossings were designed with a bridge or an oval pipe, were 

decommissioned and excavated, or otherwise did not include a pipe in the design. Risk 

of pipe plugging does not exist at most of these stream crossing types.
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Photo 5. Many stream crossings 

such as this one have more than one 

pipe to prevent blockage or flow 

diversion. SBI figures do not account 

for the presence of multiple pipes 

which means some SBIs may predict 

higher risk than what actually exists. 

The SBI values for Bear Valley stream crossings were relatively high with an average 

value of 2 for the 146 assessed stream crossings (Figure 12). This is out of a range of 1

to 4, where 1 suggests minimal to no risk of blockage. The 36 stream crossings with 

values of 3 and 4 all had pipe to channel width ratios equal to or less than 0.75. 

Approximately one third of these crossings had a channel angle (angle at which the 

channel enters the pipe) greater than 25 degrees. Some stream crossings predicted to 

be at risk in Bear Valley may not be as prone to failure as predicted. Therefore, a more 

thorough field survey of stream crossings with high SBIs would indicate where failures 

would likely occur and where repair is needed.

Figure 12. Distribution of Stream Blocking Index values.
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The risk of a stream crossing failure can also be viewed in the context of the 

consequences of failure (Flanagan et al. 1998). A consequence of concern at these 

stream crossings is the erosion of fill material into the stream channel. The fill material 

that would likely be excavated in an overtopping type failure was calculated. Then the 

prism of fill at risk was modeled as bounded at the base by an area 1.2 times the 

channel width, with side slopes climbing to the road surface at an angle of 33%. The fill 

volume at risk in the Bear Valley road configuration was approximately 3,213 m

3

. 

A second, and perhaps greater, consequence of concern at failed stream crossings is 

the diversion of stream flow onto road surfaces and unchannelled hillslopes. Once a 

crossing becomes occluded and begins to act as a dam, failure can occur in several 

ways. If the road grade dips into and rises out of the crossing, the failure is likely to be 

limited to a localized overtopping of the stream crossing. However, if the road grades 

away from the stream crossing in one or more directions, the flow may be diverted down 

the road and ditch and onto adjacent hillslopes, where it can cause gullying and/or 

landsliding (Furniss et al. 1998, Best et al. 1995). In these situations, volumes of 

sediment far exceeding those at the crossing can be at risk. A past example of such an 

event occurred in this basin in 2003 where a flow diversion failure occurred on NFSR 

579 due to a post-wildfire debris flow.

GRAIP addresses this issue by classifying the potential for stream crossings to divert 

streamflow down the adjacent road as: no potential, potential to divert in one direction, 

or potential to divert in two directions. In Bear Valley, 21% (41 out of 191) of the stream 

crossings on the roads had the potential to divert streamflow down the road in at least 

one direction. Taking into account both the diversion potential and the fill material 

volume at risk, stream crossing failure risk in Bear Valley is low to moderate.

5.6 Gully Initiation Risk

Gullying at drain points below roads can be a substantial source of sediment to stream 

channels. Gully initiation occurs when the shear stress applied by runoff exceeds the 

strength of the soil surface on the hillslope. GRAIP computes the Erosion Sensitivity 

Index (ESI) (Istanbulluoglu et al. 2003), as shown below, at each drainage point. 

2 ESI L S

, where:

L

is the road length contributing to the drain point

S

is the slope of the hillslope below the drain point

Generally, calculated ESI values can then be compared to a critical ESI threshold

(ESIcrit) to identify areas with a high risk of gully formation (i.e., where drain point ESI > 

ESIcrit). ESIcrit is empirically-derived using inventoried gullies. In Bear Valley, a total of 

22 gullies were recorded and 17 gullies were associated with a drain point that was 

actively discharging water to it from the road surface. This means that 0.4% (17 out of 

3,826) of all drain points were discharging to a gully. There were not enough observed 

gullies in proportion to the number of drain points to establish ESIcrit for this area. There 
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is no ESI at which the risk of gullying increases significantly, because the drain points 

with gullies are distributed relatively evenly throughout the road length-discharging 

hillslope range (Figure 13).

Figure 13. Distribution of where drain points discharge flow from the road by ELength 

and slope of the hillslope at the drain point.

The average ESI for all drain points was 1.9, with an average contributing road length of 

61 m. The average slope of the hillslope at the drain point was 14%. Of all drain points 

discharging to a gully, 10 (59%) had an ESI less than the average of 1.9. This affirms 

the conclusion that the sample of observed gullies in Bear Valley is insufficient to 

determine ESIcrit, which suggests that the gullies found in Bear Valley are not strongly 

tied to road length draining to them or the slope of the hillslope on which they are 

located. Other factors such as localized geology, past wildfires, or isolated large storm 

events may be causes of the gullies that do exist. Given the active wildfire history of the 

basin, it might be predicted that gullying would be a greater risk than observed, 

especially taking into account concentrated flow from roads. Nearly 30% of the area of 

Bear Valley burned during the Red Mountain wildfire in 2006 and the Sheep Trail 

wildfire in 2007, and a total of 59% of the basin has burned within the last 25 years. 

This emphasizes the prediction that the risk of gullying throughout areas of the 

watershed with roads is uniformly low.
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5.7 Landslide Risk

Bear Valley has a very low incidence of shallow landslides or other types of mass 

wasting. The GRAIP inventory records landslides which are visible from the road and are 

greater than a minimum threshold of 6 feet in slope length and slope width. However, no 

such landslides were observed during the inventory. Similar to gully initiation risk, based 

on the lack of mass wasting events observed during the road inventory in Bear Valley

despite recent wildfire history, increased risk of landsliding caused by roads is very low. 

Managing the land for such events would likely not be an effective use of resources.

The risk of shallow landslide initiation is predicted using SINMAP 2.0 (Pack et al., 2005, 

http://hydrology.neng.usu.edu/sinmap2/), then modified to account for contributions of 

road runoff. An example from NFSR 583 is shown in Figure 14 to illustrate the change 

in risk in an area where the inherent landslide risk is high. This risk is assessed by 

referring to an index referred to as the Stability Index (SI). SINMAP was run initially to 

determine the intrinsic stability (SI) of the slopes over which the road traverses and to 

identify locations that are at high risk of failure without a road(Figure 14a). 

A second stability index run was performed to address the effects of road water 

contribution to drain points on the road network. This second stability index run is 

referred to as the Stability Index Combined (SIC) because it accounts for both the 

naturally inherent risk of hillslope failure in a landscape and the added risk from roads. 

Roads which exhibited the greatest amount of negative change in slope stability in Bear 

Valley include NFSR 583, NFSR 569, NFSR 564, NFSR 500, and NFSR 502. Because 

there were no recorded landslides from the GRAIP field survey, an accurate calibration 

of change in the SI was not possible. This means that the different degrees of slope 

stability displayed in Figure 14 are only relative to each other and do not necessarily 

make up reliable predictions of increased risk of mass wasting for this area. Therefore,

Figure 14 and its indicated predictions of SI change due to roads are only an estimation

of what might actually be happening. The true added risk of mass wasting with road 

drainage could be higher or lower than GRAIP outputs suggest. More data on existing 

failures is needed for calibration.

The grid cells surrounding portions of NFSR 583 with increased risk of landsliding due 

to road drainage are shown in Figure 14b. This stretch of NFSR 583 runs through a 

previously burned area where flow of water on the road is highly concentrated, resulting 

in high amounts of energy when water discharges from the road prism. The road 

surface is highly eroded. The drain points depicted in the figure below are mostly water 

bars with a few non-engineered drains and one ditch relief culvert. The addition of drain 

points to the roads primarily increased previously existing high landslide risk. Instances 

where previously stable hillslopes were classified as unstable due to road drainage 

were few. 
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14a 14b

a) SI values for hillslopes in an un-roaded condition. b) Negative changes in SI due to 

the addition of road drainage.

Figure 14. Stability index for hillslopes in the vicinity of NFSR 583.

Potential improvements that could mitigate the increased landslide potential along atrisk roads such as NFSR 583 primarily include the installation of more frequent drainage 

features (e.g. water bars, broad based dips, etc.). However, increased drainage may 

redistribute landslide risk to other locations rather than eliminate it. Risks of mass 

wasting are often slightly increased in steep, dissected terrain, because it is difficult to 

redirect discharge from one location without elevating the risk in others. This is 

consistent with Madej (2001), who concluded that decommissioned roads in high risk 

areas commonly experience failures after treatment because their effects cannot always 

be fully mitigated. 

6.0 Quality Assurance

As a measure of quality assurance and quality control for data collected during the field 

inventories, a plan was devised and created in collaboration between RMRS hydrologists 

and GRAIP model developers and USEPA project managers. The plan is entitled, 

Geomorphic Road Analysis and Inventory Package (GRAIP) Field Collection Activities: 

Quality Assurance Project Plan (QAPP). (Black et al. 2009)

The QAPP outlines several data quality objectives (DQOs) that are intended to ensure 

accuracy and consistency of data among field crews. First, each crew received training 

from GRAIP experts at the RMRS prior to being deployed to the study area. These crews 
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received further training in the field from the field crew leader upon arrival to the study area. 

Field crews and the field crew leader coordinated daily to answer any field related 

questions and to address data collection procedures. The crew leader also acted as part of 

an “expert” crew for empirical assessment of precision and bias.

Three road sections (QA plots, see Figure 15 in Appendix B) were selected for quality 

assurance monitoring and analysis in compliance with the QAPP. Each of these roads was 

individually surveyed by each of the three hired field crews and by an expert crew. 

Sediment production and sediment delivery results were compared to measure precision 

and bias. One of these sections was chosen based on having high sediment production 

and high sediment delivery. Another section was specifically chosen to have low sediment 

production and low sediment delivery. The third section was chosen by convenience and is 

more representative of the average road conditions within the watershed. The first of these 

QA plots was surveyed soon after the hired crews completed training. The second QA plot 

was completed approximately one month after the initial plot and the third another month 

after the second.

Precision is a measure of repeatability and consistency. Bias is a measure of accuracy. 

Since sediment production and delivery values were generally very high in the project 

watersheds, relative precision and bias were evaluated to assess QAPP objectives. 

Precision and bias were calculated for each of the three QA plots. For individual QA plots, 

relative precision of sediment production ranged from 13% to 17% and relative bias ranged 

from -20% to 18% (Table 9). Relative precision of sediment delivery ranged from 17% to 

19% and relative bias from -29% to 9%. The objective outlined in the QAPP was to ensure 

that relative precision values are within 20% of the mean of all replicates of collected data, 

including that of the expert crew. The objective for relative bias was defined to be within 

20% of the expert crew’s sediment production and delivery predictions. These objectives 

were met in all but one category of one QA plot, the relative bias for QA Plot 3. Here, the 

bias for sediment production was -20.27% and -28.65% for sediment delivery. This means 

that data collected by hired field crews suggest less sediment was being both produced 

and delivered to streams than did the expert crew’s data. Because this was the last QA 

data set collected before the end of the field season, corrective action did not take place as 

there was insufficient time to do so before field crews ended the season.

Total sediment delivery for QA Plot 2 was drastically lower than it was for QA Plots 1 or 3. 

The QAPP identifies transition values for sediment production and delivery below which 

absolute values of precision and bias are to be used for assessment rather than relative 

values. The transition value for sediment delivery is 5 tonnes/km/year. Total estimated 

sediment delivery calculated from the expert crew’s data for QA Plot 2 was 1.58 

tonnes/km/year. Therefore, absolute precision and bias are to be examined. The absolute 

precision for sediment delivery for QA Plot 2 was 0.40 tonne/km/year and the absolute bias 

was -0.51 tonne/km/yr. This is within the absolute objective value of 1 tonne/km/year as 

outlined in the QAPP.
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Table 9. Quality assurance statistics for the Middle Fork Payette River7and Bear Valley 

Creek and Elk Creek watersheds. 

QA Plot 1

Experts Crew 1 Crew 2 Crew 3 Abs_Prec Rel_Prec Abs_Bias Rel_Bias

Sum_SedDel 

(kg/yr) 723,146 602,646 1,001,908 763,732 

Sum_SedProd 

(kg/yr) 807,154 738,724 1,048,186 1,037,079 

Sum_ELength (m) 3530 3525 3530 3527

SedDel/ELength 

(t/km/yr) 204.85 170.97 283.85 216.55 40.98 18.71% 18.94 9.24%

SedProd/ELength 

(t/km/yr) 228.65 209.57 296.96 294.05 38.80 15.08% 38.21 16.71%

QA Plot 2

Experts Crew 1 Crew 2 Crew 3 Abs_Prec Rel_Prec Abs_Bias Rel_Bias

Sum_SedDel 

(kg/yr) 6,216 3,150 3,150 6,300 

Sum_SedProd 

(kg/yr) 157,563 207,743 140,301 210,263 

Sum_ELength (m) 3926 3931 3929 3928

SedDel/ELength 

(t/km/yr) 1.58 0.80 0.80 1.60 0.40 33.08% -0.51 -32.48%

SedProd/ELength 

(t/km/yr) 40.13 52.85 35.71 53.53 7.80 17.12% 7.23 18.02%

QA Plot 3

Experts Crew 1 Crew 2 Crew 3 Abs_Prec Rel_Prec Abs_Bias Rel_Bias

Sum_SedDel 

(kg/yr) 487,828 341,297 317,345 384,600 

Sum_SedProd 

(kg/yr) 1,028,792 809,744 913,073 735,271 

Sum_ELength (m) 3831 3826 3823 3832

SedDel/ELength 

(t/km/yr) 127.35 89.22 83.01 100.37 16.98 16.98% -36.48 -28.65%

SedProd/ELength 

(t/km/yr) 268.56 211.67 238.85 191.89 28.87 12.68% -54.43 -20.27%

Objective Met

Objective Not Met

 

7

Field crews conducting the Bear Valley GRAIP road inventory in the summer of 2009 were concurrently 

conducting a GRAIP road inventory on the Middle Fork Payette River watershed. This QAPP was 

designed to be the quality assurance plan for both project areas. QA Plots 1 and 3 were in the Middle 

Fork Payette River watershed and QA Plot 2 was in the Bear Valley Creek watershed (see Appendix B).
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The unachieved DQO of relative bias of sediment production and delivery on QA Plot 3 

may be a result of greater misinterpretation of road drainage attributes by the expert crew 

rather than the hired crews. As shown in the table, both predicted sediment production and 

predicted sediment delivery outputs from the expert crew’s dataset were considerably 

higher than the same for all three hired crews. This suggests that for this plot, the hired 

crews were rather consistent in their interpretations of road drainage attributes, but the 

expert crew was the outlier.

The primary sources of error among the QA plots were discrepancies in flowpath 

vegetation on road segments and stream connection at drain points as interpreted by the 

crews. Flowpath vegetation is calculated into the sediment production equation. Where 

the percentage vegetation cover in the flowpath is recorded to be 25% or more, the 

sediment production rate is dramatically reduced. This was often the case in comparing 

the road segment attributes of different crews’ datasets for these QA plots. On QA Plot 3, 

the hired crews recorded an average of 33% of flowpath length to have more than 25% 

vegetation whereas the expert crew only recorded 15% for the same. The other main 

source of error for these plots was the observed and recorded road-stream connectivity of 

drain points. In general, hired field crews recorded fewer drain points to be hydrologically 

connected to a stream than did the expert crew. On average, hired crews recorded 33% of 

drain points to be connected to a stream whereas the expert crew recorded 45% to be 

connected. Further training on measuring flowpath vegetation and on identifying evidence 

of fine sediment transport and water flow to determine stream connection will help reduce 

these errors among future crews. 

In order to address the observed bias in the flow path vegetation observations, additional 

crew training will be implemented along with a new calibration element in future GRAIP 

field inventories. A point/line transect approach will be used to calibrate the field crew on 

two road segments inventoried each day. First a crew will estimate and record vegetation 

cover, then a 20 meter tape will be stretched along the flow path and vegetation presence 

or absence will be recorded at one meter intervals. The transect intersection data will 

serve to calibrate the ocular estimates through time and between crews. Frequent 

calibration of ocular estimate values has been shown to be effective in minimizing observer 

bias in other forestry data collection problems such as estimating tree stem diameter.

In addition to the survey of QA plots, the field crew leader conducted monthly field audits or 

“ride-a-longs” with each crew in order to evaluate the crew’s performance and provide realtime corrective action as needed. During these ride-a-longs, the field crew leader would 

observe a field crew through the survey of a road segment, point out inaccurate or 

inconsistent performance and correct it on the spot, and review weaknesses and 

discrepancies in data collection procedures that might affect data quality.

Due to logistics and the pressing demands of the field season, data collected on QA plots 

were not processed until after the end of the field season. QA results, including DQOs from 

QA Plot 3 that were not met and other dissatisfactory QAPP requirements, are currently 

being evaluated in order to take corrective action before the next phase of this or other 

similar projects. Despite the few quality assurance objectives that were not met, the 
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GRAIP data collected during the Bear Valley road inventory project is considered valid and 

usable for analysis. See Appendix B for more information on the QAPP.

7.0 Summary & Conclusions

The BNF and the RMRS initiated a road inventory project to include all roads in the Bear 

Valley and Elk Creek watersheds in the summer of 2009. Funding was provided through 

an interagency agreement with the USEPA. Field crews inventoried road segments in Bear 

Valley while a data manager and a GIS technician processed and analyzed the data that 

was collected in the field. The GRAIP model was used to predict the level of impact/risk 

that existing roads posed on streams. Study objectives were identified as outlined in 

Section 2.0 of this report. These objectives were met and the questions posed were 

answered as shown below.

1. What is the existing level of fine sediment delivery from roads to streams in Bear 

Valley?

a. How does the contributed sediment from roads compare to natural 

reference sediment levels?

The length of the sampled road that was hydrologically connected to streams totaled 18 mi 

(29 km) out of the 146 mi (235 km) of inventoried road (12.5%). The model predicted that 

the existing level of fine sediment delivery from roads to streams amounts to 845 tons (767

tonnes) annually, which is 10% of the predicted annual fine sediment production total of 

8,091 tons (7,340 tonnes). Road sediment that accumulates in the stream network 

annually is predicted by the model to be 821 tons (745 tonnes). Measuring from the mouth 

of Bear Valley Creek (which includes both Bear Valley and Elk Creek watersheds), the 

accumulated road sediment per unit area is predicted to be 4.3 tons/mi2/yr (1.5 

tonnes/km2/yr). Compared to the watershed’s natural reference sediment accumulation 

rate of 25.5 tons/mi2/yr (8.9 tonnes/km2/yr), added road sediment yields a 17% increase. 

2. Where are the locations of highest sediment delivery from roads to streams?

a. Can these sites be reconstructed to eliminate or minimize delivery?

As indicated in Figures 4 and 5, locations of high sediment delivery within the Bear Valley 

and Elk Creek watersheds are relatively widespread. NFSR 569 has the single highest 

sediment-delivering drain point and several other high delivery drain points within its length. 

NFSR 502, FR 582, FR 563, and FR 579 have frequent drain points which are actively 

delivering fine sediment to streams. Road-stream connection often occurs at or near live 

stream crossings on roads. Although these predicted locations of high sediment delivery 

are based on thorough field observations and careful data processing, more thorough field 

surveys of the indicated road segments and drain points would need to be completed in 

order to design effective management plans. Reconstruction of such sites is possible and 

feasible in most cases. In order to decrease sediment delivery, road improvements may 

involve the addition of more frequent road drainage features, leaving a shorter distance 

between features. This would decrease the energy of concentrated flow to individual drain 

points, thus shortening the distance that water and sediment travels down the hillslope. 
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Treatments may also include re-surfacing the road with a crushed rock aggregate or 

another type of surface which is less erosive. 

3. What unknown geomorphic or hydrologic issues exist in Bear Valley’s road system 

that could help forest managers make decisions and plan more effectively?

Other existing hydrologic issues in Bear Valley consist of drain point features in poor 

condition and stream crossings with a potential of being blocked or failing. Out of 3,826 

individual drain points, 10% (379) of drain point features were recorded to be in poor 

condition. These are drainage features that may require reconstruction, replacement, basic 

maintenance, or removal. The average stream blocking index of stream crossings at risk 

was 2 on a scale of 1 to 4 where 1 indicates virtually no risk. The fill volume at risk if these 

stream crossings fail in the Bear Valley road configuration was approximately 3,213 m3. A 

more thorough field assessment of each stream crossing at risk would be necessary to 

determine if the predicted failure potential is accurate and if the stream crossing culverts 

require attention. Although 22 gullies were recorded during the field survey, there are not 

enough data on gullies or landslides to suggest significant risk of mass wasting in Bear 

Valley. Critical thresholds to indicate when risk of gully initiation or landslides increases 

sharply were not established during data analysis. The lack of observed mass wasting 

events despite the fact that 59% of the basin has burned from wildfire within the last 25 

years strengthens the argument that management for such events should be a low priority.

The results of the QAPP suggest that the margin of error among data collected by the 

different crews was reasonable and that the data are considered usable for analysis. 

Field crews were regularly trained and audited on data collection methods by individuals 

considered experts in using the GRAIP inventory protocol. The three quality assurance 

plots that were surveyed by each crew and by an expert crew yielded acceptable figures 

of relative precision and bias. The relative precision and bias objectives were identified 

to be +/- 20% in the QAPP. DQOs were met in all but one category, relative bias of 

sediment delivery and production for QA Plot 3, which were -28.65% and -20.27% 

respectively. 

As a whole, these results indicate that Bear Valley roads do pose some risk to water 

quality and associated beneficial uses. It is also evident that a feasible amount of 

project work could eliminate a substantial portion of this risk. By making improvements 

to 4.5 miles of road, up to 50% of fine sediment delivery from roads could be eliminated. 

Reconstructing 10 miles of road could reduce this factor by as much as 85%. Other 

work could also be effective in greatly reducing many of the hydrogeomorphic impacts 

and risks that these roads pose to water quality and associated beneficial uses. This 

analysis will allow forest managers to efficiently prioritize resource restoration plans 

based on site-specific data.
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Appendix A: Glossary

Below is a list of terms and vocabulary associated with the GRAIP model and this 

report. Adapted from Black, Cissel, and Luce (2009) and the Forest Service Manual.

Accumulated road sediment rate. An output of the GRAIP model that is a prediction 

of the accumulated road sediment load in an identified stream segment, specific 

to the total area of land draining to that stream segment. Given in Mg/km2/yr by 

GRAIP, then converted to tons/mi2/yr for this report.

Arterial road. An NFS road that provides service to large land areas and usually 

connects with other arterial roads or public highways (e.g. NFSR 579).

Assessment unit. (AU) A segment of a water body that is treated as a homogenous 

unit, meaning that any designated uses, the rating of these uses, and any associated 

causes and sources must be applied to the entirety of the unit.

Berm. A build-up of sediment or road material generally found on the outside edge of a 

road, caused by periodic road maintenance such as grading.

Broad based dip. A type of drain point collected during the GRAIP field inventory 

characterized by a large grade reversal in the road either designed into the road 

grade or there as a result of two natural hillslopes meeting.

Collector road. An NFS road that serves smaller areas than an arterial road and that 

usually connects arterial roads to local roads or terminal facilities (e.g. NFSR 

502).

Cutslope. The steep slope on the uphill side of a road which is the result of the 

removal of hillslope material to make a flat surface for the road.

Designated road. An NFS road that is designated for motor vehicle use pursuant to 36 

CFR 212.51 on a Motor Vehicle Use Map (36 CFR 212.1).

Diffuse drain. A type of drain point collected during the GRAIP field inventory 

characterized by a road segment that does not exhibit concentrated flow off the 

road. Outsloped roads or crowned roads often drain half or all water diffusely off 

the fillslope. Although collected as a drain point, this feature is representative of 

an area or a road segment rather than a concentrated point where water is 

discharged from the road prism. Diffuse drainage is also commonly known as 

sheet drainage.

Ditch relief culvert. A type of drain point collected during the GRAIP field inventory 

characterized by a pipe (typically metal) that runs perpendicular to and under the 

road surface. These features generally drain water from the inboard ditch and 

cutslope of a road, not from a continuous stream channel.
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Drain point. A feature collected during the GRAIP field inventory that describes a

distinct point along a road where water flows off of the road and out of the road 

prism.

Fillslope. The steep slope on the downhill side of a road which is the result of the 

addition of material, often from the cutslope, to make a flat surface for the road.

Flow path. An attribute of a road segment collected during the GRAIP field inventory 

which describes the course flowing water takes, or would take if present, within 

the road prism. A flow path is where water is being concentrated and flowing 

along the road from where it enters the road prism to where it discharges off the 

fillslope.

Forest Road. (FR) A road wholly or partly within or adjacent to and serving the 

National Forest System (NFS) that the USFS determines is necessary for the 

protection, administration, and utilization of the NFS and the use and 

development of its resources (36 CFR 212.1). May be an NFS road or a public 

road where a legally documented right-of-way has been issued to a state, county, 

or local authority (e.g. FR 582 is co-managed by the USFS and Valley County).

Forest Transportation Atlas. A display of the system of roads, trails, and airfields of 

an administrative unit (36 CFR 212.1).

Forest Transportation Facility. A forest road or trail or an airfield that is displayed in a 

forest transportation atlas, including bridges, culverts, parking lots, marine 

access facilities, safety devices, and other improvements appurtenant to the 

Forest Transportation System (36 CFR 212.1).

Forest Transportation System. The system of NFS roads, NFS trails, and airfields on 

NFS lands (36 CFR 212.1).

Forest Transportation System Management. Travel planning, analysis, designation 

of roads, trails and areas for motor vehicle use, recordkeeping, scheduling, 

construction, reconstruction, maintenance, decommissioning, and other 

operations undertaken to achieve environmentally sound, safe, and cost-effective 

access for the use, enjoyment, protection, administration, and management of 

NFS lands.

Lead off ditch. A type of drain point collected during the GRAIP field inventory 

characterized by a ditch that moves flow from the roadside ditch and leads it onto 

the hillslope. Occurs most often on sharp curves in the road and/or where the 

cutslope switches roadsides. This feature is also known in some areas as a 

daylight ditch or a mitre drain. In Bear Valley, this feature was occasionally used 

to describe an engineered drainage feature along an outside berm where the 

berm is knocked down and a flow is directed onto the forest floor.
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Local road. An NFS road that connects a terminal facility with collector roads, arterial 

roads, or public highways and that usually serves a single purpose involving 

intermittent use (e.g. a spur road).

National Forest System Road. (NFSR) A forest road other than a road which has 

been authorized by a legally documented right-of-way held by a state, county, or 

local public road authority (36 CFR 212.1). Describes a road that is officially 

classified and managed by the USFS and is thereby assigned to a road 

maintenance category. 

Non-engineered drain. A type of drain point collected during the GRAIP field inventory 

characterized by a drainage feature where water leaves the road in an unplanned 

manner. This can occur where a ditch is dammed by debris or where a wheel rut 

diverts water off the fillslope. A non-engineered drain point is also collected 

where water flowing against a berm erodes through the berm and drains off the 

fillslope, or where flow running down the road surface (or wheel tracks) rather 

than in a ditch flows off the fillslope where the road is outsloped for a short 

distance. At any point where water leaves the road prism not by design, a nonengineered drain is collected.

Orphan drain point. A drain point collected during the GRAIP field inventory that 

exists, but does not actively drain water from the road prism. It is likely that such 

a feature did drain water in the past, but no longer does due to natural 

geomorphic as well as engineered changes to road drainage. Examples of 

orphan drain points include blocked or buried ditch relief culverts, stream 

crossings with no sediment draining to them directly, water bars on overgrown 

roads that now drain diffusely, etc.

Public road. A road under the jurisdiction of and maintained by a public road authority 

and open to public travel (23 U.S.C. 101(a)).

Road. A motor vehicle route over 50 inches wide, unless identified and managed as a 

trail (36 CFR 212.1).

Road construction or reconstruction. Supervising, inspecting, actual building, and 

incurrence of all costs incidental to the construction or reconstruction of a road 

(36 CFR 212.1).

Road decommissioning. Activities that result in restoration of unneeded roads to a 

more natural state (FSM 7734).

Road maintenance. Ongoing upkeep of a road necessary to maintain or restore the 

road in accordance with its road management objectives (FSM 7714).
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Road prism. The portion of a hillslope directly affected by the construction of a road 

including the road surface, the cutslope, the fillslope, and any other features of a 

road. 

Road segment. (Also referred to as a road line) A linear feature collected during the

GRAIP field inventory that describes the road prism attributes for a stretch of 

road where these attributes are similar. Once an attribute of the road prism 

changes (e.g. flow path changes from ditch to wheel tracks), a new road segment 

is collected. Road segment attributes include flow paths, surface type, cutslope 

and fillslope characteristics, and more.

Sediment accumulation. An output of the GRAIP model that is a prediction of the 

amount of fine sediment accumulated in a specific stream segment as a direct 

result of roads.

Sediment delivery. An output of the GRAIP model that is a prediction of the amount of 

fine sediment added to the stream network as a direct result of the existence of 

roads. This figure is derived from observed attributes of drain point and road line 

features collected during the GRAIP field inventory, particularly whether or not 

water draining at a given drain point reaches a stream channel (stream 

connection).

Sediment production. An output of the GRAIP model that is a prediction of the 

amount of fine sediment produced on a given road segment. This figure is 

derived from observed attributes of road line features collected during the GRAIP 

field inventory (i.e. surface type and flow path vegetation), the slope and length of 

a road segment, and a base rate of road sediment production.

Stream connection. An attribute of a drain point which indicates that evidence of flow 

from the road prism reaching an active stream channel was observed in the field. 

Where stream connection is observed to exist, all fine sediment that was 

produced and delivered to that drain point is routed to the stream by the GRAIP 

model.

Stream crossing. A type of drain point collected during the GRAIP field inventory 

characterized by a stream channel that intersects a road and flows for at least 

part of most years. These features may drain water from the road or cutslope, 

but their primary purpose is to route water flowing down the hillslope in natural 

stream channels under (and occasionally over) the road. In order to be classified 

as a stream crossing, the channel must be continuous above and below the road,

have defined banks, be at least one foot wide, have a bed armored with gravel, 

rock, or sand, and display evidence of flow, even if dry at the time of survey.

Sump. A type of drain point collected during the GRAIP field inventory characterized by 

a closed depression where water is intentionally sent to pond or to infiltrate into 
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the ground. A sump can also be a place where water enters, but cannot escape, 

such as a blocked ditch on an insloped road.

Temporary road. A road necessary for emergency operations or authorized by 

contract, permit, lease, or other written authorization that is not a forest road and 

that is not included in a forest transportation atlas (36 CFR 212.1).

Unauthorized road. A road that is not a forest road or trail or a temporary road or trail 

and that is not included in a forest transportation atlas (36 CFR 212.1). 

Unauthorized roads are often user-created, are generally posted as closed, and 

are not maintained, but may be frequently used for activities such as dispersed 

camping.

Water bar. A type of drain point collected during the GRAIP field inventory 

characterized by a drainage feature which diverts water off of the road surface 

and out of the road prism onto the fillslope, or into a ditch. These features are 

common on roads with steep grades, upper-slope roads, and closed roads where 

regular maintenance is not done. Water bars are constructed by a grader blade 

or other equipment which cut into the road surface at a diagonal across the road. 

These drain points are typically 1 to 4 feet deep and 5-10 feet in road length. In 

some areas, these features are also known as cross drains or scratch ditches.
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Appendix B: QAPP Compliance

The Geomorphic Roads Analysis and Inventory Package (GRAIP) was used during the 

summer of 2009 to survey roads in two drainages in the Central Idaho Mountains, the 

Middle Fork Payette River watershed (4th order hydrologic unit) and the Bear Valley 

Creek and Elk Creek watersheds (both 5th order hydrologic units surveyed as one 

combined basin). These inventories were conducted by the Boise National Forest 

(BNF) and the Rocky Mountain Research Station (RMRS) of the U.S. Forest Service 

(USFS). The projects were funded by and completed in cooperation with the U.S.

Environmental Protection Agency (USEPA). As a measure of quality assurance for data 

collected during the field inventories, a plan was devised and created in collaboration 

between RMRS hydrologists and GRAIP model developers and USEPA project 

managers. The plan is entitled, Geomorphic Road Analysis and Inventory Package 

(GRAIP) Field Collection Activities: Quality Assurance Project Plan (QAPP). 

Figure 15. Map of QA plot locations in the Middle Fork Payette River and Bear Valley 

and Elk Creek watersheds.
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Precision is a measure of repeatability and consistency. Since sediment production and 

delivery values were generally very high in the project watersheds, relative precision 

was evaluated to assess QAPP objectives. Absolute precision was first measured by 

calculating the sample standard deviation:

n

x X

s

n

i

i

1

where,

xi = individual estimate of sediment production or delivery (replicate)

X

= mean of all replicates, including estimates derived from measurements by 

expert crew

n = number of replicates

Relative precision for such measurements is estimated as the relative standard 

deviation (RSD, or coefficient of variation):

where,

s = sample standard deviation

X

= mean of all replicates, including those produced from expert crew 

measurements

Bias is a measure of accuracy. Absolute or net bias (B) was calculated as: 

B = 

X - T

where, 

T = estimated sediment production or delivery based on measurements obtained 

by expert crew

X

= mean of all replicates, not including results of expert crew

Bias in relative terms is calculated as:

where,

T = sediment production or delivery estimate obtained by expert crew

B = Net bias
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Outline of actions taken or achievements made to comply with the QAPP:

Quality Objectives and Criteria

o Precision, Bias, and Accuracy. See explanation, equations, and table 

above.

o Representativeness. The sample of inventoried roads is considered a 

comprehensive sample. 

o Completeness. 100% of National Forest System Roads and other Forest 

Roads in Bear Valley were surveyed and the majority of unauthorized roads 

were successfully surveyed. The USFS Project Manager reviewed the 

progress and considered the sample sufficient to perform GRAIP modeling. A 

100% complete data set was collected for each road segment surveyed. As 

far as was manageable, all roads in a single sub-watershed were sampled 

before moving to a different sub-watershed. As stated in the QAPP, “A 

feature will no longer be considered a road when it does not move water 

along the surface, no longer has stream crossings, and is not located in a 

position where it can interact with the stream channel” (p. 14). Features 

which appear on GIS layers as unauthorized roads but were not inventoried 

meet this criteria. 

o Comparability. GRAIP road inventory procedural standards were met be all 

crews, resulting in comparable data.

o Pre-Inventory Training. Prior to performing the road inventory, field crews 

received training on GRAIP procedures. Training was conducted by the 

USFS Project Manager. 

o Documents and Records. The “Review and Distribution Acknowledgement” 

QAPP form was signed by the appropriate personnel. All other documents as 

outlined in the QAPP were kept except for field audit reports, which were not 

developed or used during the 2009 field season.

Data Generation and Acquisition

o Sampling Process Design. The GRAIP road inventory was considered a 

comprehensive sample without bias or statistical inference.

o Sampling Methods. The GRAIP road inventory was performed according to 

the procedures outlined in Black, Cissel, and Luce (2009).

o Sample Handling and Custody. Procedures were followed as outlined in 

the QAPP. Field crews transferred data weekly to the data manager. The 

data manager preprocessed data and transferred it to the GIS technician. 

The GIS technician corrected errors and backed up data to ensure its 

security.

o Quality Control

 Field Measurement Devices. GPS units and all other field data 

collection equipment items were tested and checked for accuracy.

 Field Measurement and Observation Procedures. Field crews were 

observed on field measurement procedures and corrected where 

necessary.

o Instrument/Equipment Testing, Inspection, and Maintenance. Field 

equipment was maintained and kept in working order or else it was not used.
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o Instrument/Equipment Calibration and Frequency. Field instrument 

calibration was performed according to manufacturer specifications including 

updates of software and firmware.

o Inspection/Acceptance for Supplies and Consumables. All field supplies 

were kept in proper working order or replaced if not.

o Data Acquisition (Non-direct Measurements). Field crews were trained 

and frequently corrected on interpretation of non-direct measurements (e.g. 

vegetation in the flowpath). Although, data do suggest that some 

discrepancies exist in the collection of such attributes, procedures outlined in 

the QAPP were followed.

o Data Management. See Sample Handling and Custody.

Assessment and Oversight

o Assessment and Response Actions

 Field Audits. As mentioned in discussion above, monthly field audits 

were performed where the field crew leader would observe a field 

crew’s survey of a road segment in order to review procedures and 

correct mistakes.

 Data Preparation Audits. The data manager and GIS Technician 

reviewed the data regularly in order to ensure its completeness and 

accuracy.

o Reports to Management. The USFS and USEPA Project Managers were in 

regular contact on the status of the project. Progress Reports were created at 

two different times to provide a formal update of the project’s progress.

Data Validation and Usability

o Data Review, Verification, and Validation

 All required signatories signed and approved the QAPP.

 All field crew members received training on GRAIP road inventory 

procedures.

 All agreed to field procedures were used in the project area.

 Equipment was maintained in proper working order.

 Instrument calibration procedures were performed according to 

manufacturer requirements.

 All project DQOs were achieved with the exception of relative bias 

figures for QA Plot 3 which were -20.27% for sediment production and 

-28.65% for sediment delivery. 

 Field audits were performed monthly with each crew. 

o Verification and Validation Methods. The USFS Project Manager and 

designees took part in the review, verification, and validation of data collected 

during the 2009 field season before crews had completely demobilized from 

field activities. It is recommended that future GRAIP inventories include at 

least daily calibration of the ocular estimates of percent vegetation cover in 

the flow path.

o Reconciliation with User Requirements. This is the data evaluation report 

that discusses the results and quality of the data collected. The data is 

considered usable for the project.
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Appendix C: Bear Valley GRAIP Data Files 

GRAIP data files from the Bear Valley GRAIP road inventory and this report are 

available to forest managers and interested parties. To receive such electronic files, 

please contact the Boise National Forest or the Boise Aquatic Sciences Lab of the 

Rocky Mountain Research Station. The following list includes names and formats of

some of the available files.

1. Bear Valley Road Inventory (GRAIP) Report (Microsoft Word document or PDF)

2. Bear Valley Road Inventory (GRAIP) Slideshow (Microsoft PowerPoint 

presentation or PDF)

3. Bear Valley Inventory spreadsheet describing raw data files of all surveyed roads 

(Microsoft Excel spreadsheets)

4. Various Microsoft Excel spreadsheets containing data from GRAIP outputs

5. Bear Valley .graip file and dataset (all files needed to view GRAIP outputs using 

the GRAIP toolbar in ArcMap)

6. Photos of various road segments and drain points

7. GIS shapefiles of GRAIP model outputs for Bear Valley

a. DrainPoints (contains data for all drain points including GRAIP predictions 

such as sediment production and sediment delivery)

b. RoadLines (contains data for all road segments including GRAIP 

predictions such as sediment production and sediment delivery)

c. StreamNet (contains data for all stream segments in the stream network 

including GRAIP predictions such as upstream sediment accumulation)

d. Individual shapefiles for each type of drain point (e.g. stream crossings, 

non-engineered drains, ditch relief culverts, etc.)

e. Road shapefile of all road segments and their attributes as collected by 

field crews, before being run through the model

8. GIS grids of GRAIP model outputs for Bear Valley

a. Original DEM used for GRAIP analysis

b. Slope stability grids

c. Grids related to the stream network
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