Compilation of Risk Factors to Aquatic Resources from U.S. Forest Service –

Pacific Northwest Travel Analysis Reports

April 2015

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Compilation of Risk Factors to Aquatic Resources from U.S. Forest Service –

Pacific Northwest Travel Analysis Reports

Each National Forest (NF) across the U.S. was required to complete a Travel Analysis Report by 

September 2015. The analysis process was to compile/evaluate existing information on each 

forests road system related to aquatic and terrestrial risks, access benefits and costs. The 

purpose is to eventually define a minimum road system that is safe and responsive to public 

needs and desires, affordable and efficiently managed, have minimal ecological effects on the 

land, and is in balance with available funding for needed management actions, and meets Forest 

Plan objectives.

Each forest was allowed to develop their own set of criteria to evaluate risks and benefits. 

Because of this latitude in direction, the criteria used to evaluate risks to aquatic systems is 

highly variable. There are some similar threads between the forests but it is difficult to 

understand what and where the road/water problems are. Though, where results were 

decipherable, often a large percentage of the road system was negatively impacting aquatic 

systems. Specifically, 

• Olympic NF: Approximately 46% (618 miles) of needed roads had high risk to aquatics 

and 60% (409 miles) of unneeded roads had high risk to aquatics

• Gifford Pinchot NF: 28% (1,121.3 miles) were high aquatic risk; 29% (1,156.1 miles) were 

moderate; and 44% (1,777.8) were low.

• Mt. Baker – Snoqualmie NF: high aquatic risk – 999 miles (41%); medium aquatic risk –

492 miles (20%)

The following document highlights the criteria chosen to evaluate aquatic risks from two forests 

in Oregon and four forests in Washington. 

Rogue-River Siskiyou NF, Oregon

• Sediment Delivery

• Roads within Riparian Reserves

• Fish Passage through Road Crossings

• Key or Municipal Watershed Status

Sediment delivery; the rating system used to assess the environmental risk of excess sediment 

entering the stream system is based on five separate GIS analyses. Two of these analyses assign 

values to roads and three assign values to the impacted watershed. The highest value for each 

road is then combined with the highest value assigned to the impacted watershed in a matrix 

that assigns the final sedimentation delivery cost associated with that road.

1. Riparian reserves 

a. 150 feet (or 300 feet if fish bearing) contributions to sediment impacts. 

2. Sub-watershed ratings: percent of the total stream riparian area in the watershed that is 

displaced by the area occupied by roads.

a. Low: <7%, Moderate: 7% - 15%, High >15%

3. Stream crossings frequency individual road segment rating (stream crossings per mile):

a. Low: <1, Moderate 1-3, High >3
Compilation of Risk Factors to Aquatic Resources from U.S. Forest Service –

Pacific Northwest Travel Analysis Reports

April 2015

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4. Sub-watershed rating: average number of road crossings per mile of stream within the 

watershed.

a. Low: <0.5, Moderate 1-3, High >3

5. Road Density (miles/square mile) within the sub-watershed.

a. Sub-watershed rating: Low: <1.5, Moderate 0.5-1.0, High >1.0

Erosion potential: Used existing information with limited field verification at a coarse scale. Soil 

erosion layer in GIS which is based on groupings of soil complexes, landslide potential, soil 

stability, geological hazard mapping. 

1. Individual road segments rating: % of the road segment located within areas of high 

erosion, landslide potential or geological hazard risk.

a. Low: <5%, Moderate 5%-10%, High>10%

2. Sub-watershed rating: 50% is based on the percentage of road miles within areas with 

high erosion, landslide potential, or geological hazard risk and 50% based on the 

percentage of the watershed that includes these areas.

Final sediment delivery impact value is calculated using a matrix that takes into account the 

direct impacts of each road and the combined impacts of all roads in a particular watershed.

Roads within Riparian Reserves

1. Individual road segments rating: % of the road segment located within one site tree 

height or 300 feet for fish streams.

a. Low: <10%, Moderate 10%-40%, High >40%

Fish Passage through Road Crossings

1. Individual road segments rating: road crossings per mile of road in fish bearing streams.

a. Low: <1, Moderate: 1-2, High >2

Key or Municipal Watershed

A Key Watershed designation if part of the Northwest Forest Plan Aquatic Conservation Strategy 

where there is a guideline for no net increase in the total miles of road inside these watersheds 

and an emphasis on reducing the miles of road in areas with high erosion and high sediment 

delivery potential.

1. Sub-watershed rating: within a Key Watershed or Ashland Creek Municipal Watershed

a. High – if it is within a key watershed or municipal watershed; low if it is not.

Results (combination of all road risks, not just aquatics): 541 miles high risk (11%), 2543 miles 

medium risk (49%) and 2,099 miles low risk (40%). Totally road miles – 5,183

Willamette NF, Oregon

The hydrologist and fisheries biologist developed a metric to determine risk rankings that looked 

at both chronic and acute sources of impacts.

Acute sources:
Compilation of Risk Factors to Aquatic Resources from U.S. Forest Service –

Pacific Northwest Travel Analysis Reports

April 2015

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• Soil instability: % of road length in high instability categories in the Willamette National 

Forest Soil Resource Inventory

• Road position: % of road length located mid-slope along hillsides with over 70% gradient

• Stream crossing density: number of stream crossings per mile of road

Chronic sources:

• Fine sediment potential: % of road miles in 3 categories based on road surfacing and 

proximity to stream crossings

• Riparian proximity: % of road miles within 170’ of perennially flowing (Class 1-3) streams

• Proximity to anadromous fish & municipal water sources: % of road miles within 500’ of 

streams that have threatened or endangered fish, and /or contribute to a municipal 

watershed (Class 1 streams)

• Proximity to non-anadromous fish: % of road miles within 500’ of streams with 

management indicator species (Class 2 steams)

Gave scores between 1-5 (low to high risk) but the report does not include those scores or how 

they were distributed.

Olympic NF, Washington

Defined aquatic risk as the potential for a road segment to damage water quality and fish 

habitat by causing landslides, introducing sediment, altering riparian areas, or limiting channel 

movement. Assessed 5 factors using GIS modeling:

1. Geologic hazard

2. Proximity to fish habitat

3. Stream crossing density

4. Proximity to stream channels

5. Upslope hazard

Gave scores of High, Medium or Low with about 1/3 in each category. The review team then 

looked for stream-adjacent road segments, potential delivery of sediment to anadromous fish 

streams, and potential delivery of sediment to municipal water supplies.

Result: Approximately 46% (618 miles) of needed roads had high risk to aquatics and 

60% (409 miles) of unneeded roads had high risk to aquatics.

Future refinements or field verification should include:

• Presence of unstable sidecast material and the potential for failures to initiate landslides 

that would deliver sediment to stream channels

• The number and size of existing stream crossings and their associated road fills

• The potential for existing culvert to become plugged

• The potential for the road segment to initiate stream diversions

• Potential impacts on floodplains and riparian areas

• Existing culvert fish passage barriers

Colville NF, Washington

Looked at water quality, not “aquatic risk”.

1. Sedimentation into hydrological features
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Pacific Northwest Travel Analysis Reports

April 2015

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a. High – 41-100% of the road is located within high risk rating zones or road is insloped with a native surface with more than two perennial or intermittent 

stream crossings greater than 3% road grade.

b. Medium – 20-40% of the road is located within a high risk rating zone or road is 

in-sloped with a native surface with one or two perennial or intermittent stream 

crossings greater than 3% road grade.

c. Low – road does not meet criteria for medium or high risk

2. Non-sediment pollution: high risk zones are defined as those within 300 feet of stream 

reaches or potential of Total Maximum Daily Load concerns, and/or dispersed camping 

sites and/or associated human activity, and/or cattle access provided at road-stream 

crossing.

a. High – 100% of the road is located within high risk rating zones OR the road has 

two or more dispersed camping sites and associated human activity within 300 

feet of a perennial or intermittent stream OR road has two or more perennial or 

intermittent stream crossings where cattle have access.

b. Medium – 2-5% of the road is located within high risk rating zones OR road has 

one dispersed camping site and associated human activity within 300’ of a 

perennial or intermittent stream OR road has one perennial or intermittent 

stream crossing where cattle have access.

c. Low – road does not meet criteria for medium or high risk.

3. Disruption of groundwater flow and negative hydrologic surface connectivity. High risk 

zones are when the road is located within the riparian area and/or floodplain (300 feet 

from stream edge.) Parallel roads on slopes also disrupt flows.

a. High: 5-100% of the road is located within high risk rating zone OR 5-100% of 

road is within 300’ of perennial or intermittent stream OR there are more than 2 

parallel roads (stacked roads) on slopes over 30% between the perennial or 

intermittent stream and ridge.

b. Medium: 0-5% of the road is located within a high risk rating zone OR 0-5% of 

the road is within 300’ of perennial or intermittent stream OR there are 1-2 

parallel roads (stacked roads) on slopes over 30% between the perennial or 

intermittent stream and ridge.

c. Low - road does not meet criteria for medium or high risk.

4. Sedimentation into hydrological features because roads that cross streams can prevent 

or inhibit fish passage.

a. High: road has 2 or more crossings on Class 1 or 2 streams

b. Medium: road has 1 stream crossing on Class 1 or 2 streams

c. Low: road has no stream crossings on Class 1 or 2 streams

5. Impact on bull trout, cutthroat trout, redband trout and designated critical habitat 

where high risk zones are roads within 300’ of water documented to have listed fish or 

designated critical habitat.

a. High: 51-100% of the road is located within high risk rating zones OR the road 

has 2 or more stream crossings on water documented to have listed fish or 

designated critical habitat.

b. Medium: 1-50% of the road is located within high risk rating zones of water 

documented to have listed fish OR the road has 1 stream crossing on water 

documented to have listed fish or critical habitat.
Compilation of Risk Factors to Aquatic Resources from U.S. Forest Service –

Pacific Northwest Travel Analysis Reports

April 2015

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c. Low – 0% of the road is located within high risk rating zones of water 

documented to have listed fish OR the road has no stream crossing on water 

documented to have listed fish or critical habitat.

Results of the aquatic risks were not easily discernable.

Gifford Pinchot NF, Washington

This forest assessed six criteria for aquatic risks and used “professional judgment” to base the 

level of risk.

1. Fish bearing crossings: road segment crosses a fish-bearing stream

a. High – road crosses the GPNF mapped distribution and/or the critical habitat 

designated by US Fish and Wildlife Service and National Oceanic and Atmospheric 

Administration for the Endangered Species Act listed species: lower Columbia River 

coho, Chinook and steelhead, and Columbia River bull trout.

b. Moderate – road crosses the GPNF mapped distribution of non-ESA-listed fish 

species.

c. No Risk– road does not cross any mapped fish bearing streams. 

2. Fish culvert barriers: road culvert is a barrier to fish migration

a. High - road segment has a culvert barrier blocking 0.1 miles or greater of fish 

habitat.

b. Moderate- road segment has a culvert barrier blocking less than 0.1 miles of fish 

habitat.

c. No Risk - road segment does not have a culvert barrier. 

3. Stream crossings: road segment crosses stream

Crossings per road segment for road segments less than 1 mile:

a. High- equal to or greater than 3 stream crossings.

b. Moderate- 1 or 2 stream crossings.

c. No Risk- no crossings.

Average Crossings per mile for road segments 1 mile or longer:

d. High- equal to or greater than 3.0 stream crossings per mile.

e. Moderate- up to 3.0 stream crossings per mile.

f. No Risk- no crossings. 

4. Sediment delivery: road segment produces sediment from road surface and delivers to 

streams

a. High- relative high rate of sediment delivery from road surfaces to streams.

b. Moderate- relative low rate of sediment delivery from road surfaces to streams.

c. No Risk- no delivery to streams (no stream crossings and road not near stream).

d. Not Rated - road segment was not rated for this criterion. 

5. Mass wasting: road segment crosses known landslides or potentially unstable soils

a. High- road segment crosses known landslides.

b. Moderate- road segment crosses potentially unstable soils.

c. No Risk- road segment does not cross known landslides or potentially unstable soils.

d. Not Rated - road segment was not rated for this criterion. 

6. Riparian occupancy: road segment is within riparian reserve for stream, lakes, ponds 

and wetlands

a. High- road segment is within Riparian Reserve for 0.3 continuous miles or greater.
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Pacific Northwest Travel Analysis Reports

April 2015

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b. Moderate-road segment is within Riparian Reserve for 0.2-0.29 continuous miles.

c. No Risk - road segment is not within Riparian Reserve for stretches over 0.19 miles. 

Results: 28% (1,121.3 miles) were high aquatic risk; 29% (1,156.1 miles) were moderate; and 

44% (1,777.8) were low.

Mt. Baker-Snoqualmie NF, Washington

Aquatic Resource Potential Risk Factors Assessment 

The roads - aquatic resource risk factors rated for each road segment, were the following factors 

of potential failure: 

1. location of road segment in Washington State rain-on-snow zone and type of 

contributing upslope area 

a. 2 = rain-on-snow (1500’ – 3500’ zone) 

b. 1 = rain or snow dominated (rain: 500’-1500’; snow: 3500’-5500’) 

c. 0 = lowland or highland (lowland: 5500’)

2. percent of area occupied by road on unstable soils, highly eroded glacial, alluvial fan, or 

recessional outwash deposits and highly fractured / unstable base geology 

a. 5 = over 50 percent 

b. 3 = 31-50 percent 

c. 2 = 10-30 percent 

d. 0 = < 10 percent

3. history of road associated failures from sources which have not been corrected includes 

replace-in-kind that have not been sized larger or replaced by a bridge; culvert spacing is 

too far for amount of runoff; large debris load existing up the channel 

a. 2 = repeated 

b. 1 = some 

c. 0 = no history

4. number of large channel crossing culverts (>36” diameter or with >3’ of fill) 

a. 2 = more than one 

b. 1 = one 

c. 0 = none 

5. number of channel crossings per 500 feet of road (using GIS stream and road layers) 

a. 2 = 3 or more crossings 

b. 1 = 2 crossings 

c. 0 = no crossings 

6. method of construction: if constructed before 1970, assume sidecast excavation, if 

constructed after 1970, assume layer placement excavation 

a. 2 = sidecast 

b. 1 = layer placement 

c. 0 = full bench 

7. average side slope of road 

a. 3 = > 60 percent 

b. 2 = 40-60 percent 

c. 0 = < 40 percent
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Pacific Northwest Travel Analysis Reports

April 2015

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8. vegetative cover: percent of area above road segment having stand age of >35 years 

(use either stand year of origin or young stands 0-5, 6-30, 31+ years GIS data layers; if no 

GIS available, use aerial photos) 

a. 3 = <20%

b. 2 = 20-49%

c. 1 = 50-70%

d. 0 = >70%

9. road stacking upslope from the road segment; if the road segment is a mid-slope road, 

rate as 1 even if there is not a road segment upslope. If the road segment upslope is a 

ridge-top road, rate as 1 rather than a 2) 

a. 3 = two or more segments above 

b. 2 = one segments above 

c. 1 = road segment is a ridge top segment 

In addition to these potential risk factors, the following “consequence of failure” factors were 

identified and rated according to a 1 – 4 scoring key: 

a. bench, terrace, or floodplain of enough size to trap potential failure debris (organic 

and inorganic) is present between the road and any channel, wetland, 

infrastructure, or other valuable natural resource ........................................1 

no bench, terrace or floodplain of enough size to trap potential failure debris 

(organic and inorganic) is present between the road and any channel, wetland, 

infrastructure, or other valuable natural resource ............................ go to b 

b. average side slope below the road segment is < 20 percent; channels, wetlands, 

infrastructure, or other valuable natural resource > 50 feet from the road...... ..1 

perennial channels, wetlands, infrastructure, or other valuable natural resource < 50 

feet from the road ...................................................................2 

average side slope below the road is > 20 percent ............................ go to c 

c. average side slope below the road is > 20 percent and < 40 percent; channels, 

wetlands, infrastructure, or other valuable natural resource > 1000 feet from the 

road ......................................................................................... 1 

channels, wetlands, infrastructure, or other valuable natural resource > 500 feet but 

<1000 feet from the road.....................................2

perennial channels, wetlands, infrastructure, or other valuable natural resource < 

500 feet from the road .................................................................. 2

average side slope below the road is > 40 percent .............................. go to d 

d. average side slope below the road > 40 percent and intermittent channels >1500 

feet from the road and no wetlands, infrastructure, or other valuable natural 

resource below the road ................................................................................... 1 
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Pacific Northwest Travel Analysis Reports

April 2015

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perennial channels, wetlands, infrastructure, or other natural resource > 1500 feet 

from the road .............................................................................. 2 

intermittent channels, wetlands, infrastructure, or other natural resource > 500 feet 

but < 1500 feet from road ................................................................ 2 

perennial channels, wetlands, infrastructure, or other natural resource >500 feet 

but < 1500 feet from road ..................................................................... 3 

intermittent channels, wetlands, infrastructure, or other natural resource < 500 feet 

from road .................................................................................... 3 

perennial channels, wetlands, infrastructure, or other natural resource < 500 feet 

from the road ............................................................................... 4 

The overall risk rating was obtained by multiplying the sum of the potential for failure scores (J) 

by the consequence of failure score (K), placing more emphasis of the effects of potential failure 

rather than just the probability of failure. The following table depicts this overall aquatic risk 

factor rating procedure: 

Road Segment # Potential for 

Failure Factors 

Scores

A B C D E F G H I

Sum of A – I 

Failure Scores

(J)

Consequence of 

Failure Score

(K)

Overall Risk 

Rating Score

(J x K)

2560-120 1 2 0 1 1 0 0 0 0 6 2 12

2250-155 2 3 1 1 1 1 3 0 1 13 2 26

2620-100 2 1 1 0 1 1 1 2 3 14 3 42

Aquatic Resource Values Assessment:

The six aquatic resource values were rated by the following High, Medium, Low procedure. 

(1) Fish Passage Needs (Risk) High = presence of both anadromous and resident fish with 

1⁄4 mile or more of habitat could be made accessible Medium = presence of only resident 

fish with 1⁄4 mile or more of habitat could be made accessible Low = less than 1⁄4 mile of 

habitat made accessible or presence of no fish passage problem 

(2) Key Watershed Designation (Value or Use) High = yes, contains Chinook salmon, 

steelhead and / or bull trout Medium = no, but contains Chinook salmon, steelhead or 

bull trout Low = no, and does not contain Chinook salmon, steelhead or bull trout 

(3) Proximity to Riparian Reserves (Value or Use) High = within riparian reserves having 

fish bearing channels Medium = within riparian reserves but not having fish bearing 

channels Low = no within a riparian reserve 

(4) Watershed Analysis (WA) & Watershed Restoration (WR) Status (Value or Use) High 

= road restoration work recommended in WA, opportunities existing for WR Medium = 

no road restoration work recommended in WA, but information exist about potential 
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Pacific Northwest Travel Analysis Reports

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for WR Low = no road restoration recommended, and no restoration potential known; 

no WA done 

(5) Water Quality Value (Clean Water Act 303(d) Listed Water Body (Value or Use) High 

= road or road segment is within contributing area to water body listed for a water 

quality/quantity parameter or characteristic considered to be directly sensitive to road 

management (fine sediment, turbidity, etc.) Medium = road or road segment is within 

contributing area to water body listed for a water quality/quantity parameter or 

characteristic considered to be indirectly sensitive to road management (temperature, 

dissolved oxygen, fish habitat) Low = road or road segment does not contribute to a 

listed water body, or the water body is listed for a water quality/quantity parameter not 

sensitive to road management 

(6) Municipal Watershed (Value or Use) High = road or road segment lies within 

contributing area of a large municipal watershed (city of Bellingham, Everett, Tacoma, 

etc.) Medium = road or road segment lies within contributing area of a small municipal 

watershed (Verlot, Maple Falls, Glacier, etc.) Low = road or road segment does not lie 

within contributing area of an municipal watershed As stated before all these aquatic 

resource values, except for fish passage were assigned these ratings at the fifth-field 

watershed scale. Fish Passage ratings were applied to each road segment.

Combining the Aquatic Potential Risk Factors and Aquatic Resource Values 

With both the aquatic risk rating and the aquatic value rating, the next step was to combine 

these two procedures in order to provide the overall road analysis process one aquatic resource 

assessment rating to be consistent with other resources of concern (vegetation, wildlife, and 

heritage resources). This was obtained using the matrix below:

Matrix for Rating Aquatic Resources (Risk Factors + Values)

Factor or Value High Medium Low

Composite Risk Factor 

Rating (A) 

Composite score of 27 

or greater 

Composite score 

between 15 – 26

Composite score of 14 

or less 

Fish Passage Needs 

(B)

Anadromous & 

resident fish present, 

1⁄4 mile or more 

habitat 

Only resident fish 

present with 1⁄4 mile 

or more of habitat 

Less than 1⁄4 mile 

habitat or no fish 

present 

Key Watershed Status

(1) 

Yes, contains listed 

ESA listed fish

No, but contains ESA 

listed fish

No, and does not 

contain ESA listed fish

Proximity to Riparian 

Reserves (2) 

Within riparian 

reserves having fish 

bearing channels 

With riparian reserves 

but does not have fish 

bearing channels 

Not within an riparian 

reserve 

WA and WR Status (3) Road restoration 

recommended in WA 

and opportunities 

exist for WR 

No road restoration 

recommended in WA, 

but opportunities 

exist for WR 

No road restoration 

recommended and no 

opportunities

Water Quality Status

(4)

Within an area with 

impaired water body 

Within an area with 

impaired water body 

Not within an area 

with impaired water 
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Pacific Northwest Travel Analysis Reports

April 2015

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directly affecting a 

WQ parameter 

indirectly affecting a 

WQ parameter 

body or WQ 

parameter not 

affected 

Municipal Watershed 

Status (5) 

Within an area of 

large municipal 

watershed 

Within an area of a 

small municipal 

watershed 

Not within a 

municipal watershed 

In rating both aquatic risk factors and aquatic values, more importance was assigned to the 

composite risk factor rating (A) and the aquatic value of fish passage (B). The overall aquatic 

resource rating for each road segment was obtained by following scoring scheme: 

• If both (A) and (B) is rated High, regardless of the ratings for (1), (2), (3), (4), (5) then 

overall rating is High 

• If either (A) or (B) is rated High, and 3 of (1), (2), (3), (4), or (5) is rated High, then overall 

rating is High 

• If either (A) or (B) is rated High, and 2 of (1), (2), (3), (4), or (5) is rated High, then overall 

rating is Medium 

• If either (A) or (B) is rated High, and just 1 of (1), (2), (3), (4), or (5) is rated High, then 

overall rating is Low 

• If (A) or (B) is rated Medium, and 4 or 5 of (1), (2), (3), (4), or (5) is rated High, then 

overall rating is High If (A) or (B) is rated Medium, and 3 of (1), (2), (3), (4), or (5) is rated 

High, then overall rating is Medium If (A) or (B) is rated Medium, and 1 or 2 of (1), (2), 

(3), (4), or (5) is rated High, then overall rating is Low If (A) and (B) is rated low, 

regardless of the ratings for (1), (2), (3), (4), or (5), then overall rating is Low

Results: Nearly 41% of the total road system (2,440 miles) has a resource concern of medium or 

high. The listing of numerous species as threatened or endangered under the Endangered 

Species Act and a large amount of unstable landscapes contribute to the high mileage of 

resource concern roads. 

high aquatic risk – 999 miles (41%)

medium aquatic risk – 492 miles (20%)