Black, T. A., Cissel, R. and Luce, C. H. 2012. The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 1: Data Collection Method. Gen. Tech. Rep. RMRS-GTR-280WWW. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Cissel, R. M., Black, T. A., Schreuders, K. A. T., Prasad, A., Luce, C. H., Nelson, N.A., Tarboton, D.G., and Nelson, N. A. 2012. The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 2: Office Procedures. Gen. Tech. Rep. RMRS-GTR-281WWW. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 

Cook, C., and Dresser, A. 2010. Erosion and Channel Adjustments Following Forest Road Decommissioning, Six Rivers National Forest. In M Furniss, C Clifton, and K Ronnenberg, eds., 2007. Advancing the Fundamental Sciences: Proceedings of the Forest Service National Earth Sciences Conference, 

San Diego, CA, 18-22 October 2004, PNW-GTR-689, Portland, OR: US Department of Agriculture, Forest Service, Pacific Northwest Research Station.

Luce, C.H., and Black, T. 1999. Sediment production from forest roads in western Oregon. Water Resources Research. Vol. 35, No. 8, pp: 2561-2570.

Overall, both treatment types were effective compared 

to control roads.

Exceptions: new gullies on SDRR roads, large erosion 

volumes at some excavated stream crossings, localized 

increases in flowpath condition problems. 

•

•

Further work to determine fine-scale causes behind 

these increases and reductions, as well as examine 

BMPs and develop tools for managers to use to prevent 

problems and further reduce impacts and risk to 

watersheds from forest roads.

•

Conclusions • Fine sediment delivery was reduced 79% by decommissioning, and 61% by SDRR.

Mass Wasting

Shallow landslides and gullies that meet a minimum 

threshold for size are measured or estimated to 

determine volume. Even after a storm event, most sites 

did not have any new mass wasting events. Gullies 

often initiate below new drainage points when they 

have a long contributing length of road or discharge 

onto a steep or unstable slope.

PreTreatment 

Volume (m3)

Number 

of New

Volume 

of New 

(m3)

% New 

Volume of 

Pre Volume

PreTreatment 

Volume (m3)

Number 

of New

Volume 

of New 

(m3)

% New 

Volume of 

Pre Volume

Decom Treatment 97 84,150 12 1,000 1% 1,930 20 590 30%

Decom Control 92 20,050 6 2,110 11% 1,210 23 140 11%

SDRR Treatment 86 9,270 5 1,030 11% 8,650 59 13,680 158%

SDRR Control 71 7,380 4 10 0.2% 2,340 30 380 16%

Site Type

Length 

of Road 

(km)

Landslides Gullies

Decommissioning treatments, which prevent roads from 

concentrating water in large volumes, were successful 

at reducing risk from both gullies and landslides. 

SDRR treatments, which leave water concentrated and 

may discharge at new locations, were less successful, 

particularly in relation to new gully formation. 

 SDRR Road Surface Erosion

Road surface and flowpath condition problems include 

gullies, rills, buried ditch lines, ruts, and stream 

diversion courses.

%, PreTreatment 

Length

%, PostStorm Event 

Length

Δ 

Length 

(m)

% 

Change 

Length

%, PreTreatment 

Length

%, PostStorm Event 

Length

Δ 

Length 

(m)

% 

Change 

Length

SDRR Treatment 85,990 10% 1% -7,970 -89% 10% 6% -3,140 -36%

SDRR Control 68,310 5% 2% -2,080 -56% 12% 15% 2,250 27%

Surface Condition Problems Flowpath Condition Problems

Site Type

Length of 

Road 

Treated 

(m)

Road surface and flowpath condition problems were 

both successfully addressed by the SDRR treatments. 

Control roads experienced an increase in flowpath 

condition problems, and a decrease in surface 

condition problems. The decrease was much smaller 

than that of the treated roads.

Excavated Stream Crossings

Excavated stream crossings on decommissioned roads have had their culvert infrastructure removed. The channel 

and remaining road fill are recontructed to closely mimmick the natural channel and valley. We surveyed the 

excavated crossings to determine the shape of 

the new crossing, erosion present, and the risk 

of further erosion (Black et al. 2012).

As the new channel adjusts, some erosion is 

expected at excavated stream crossings. While the 

mean volume eroded for all sites was low relative 

to previous findings (Cook and Dresser 2010), a few sites had significantly higher eroded volumes. Volumes may vary with 

precipitation, channel sizes (bigger streams erode more and wider channels inherently have more volume), natural 

slopes, or with design and implementation standards (matching the excavation to the natural channel and valley). Eroded 

volumes were 15% of the total that could be expected to erode over time as the untreated crossings failed.

Total 

Volume (m3)

Mean 

Volume (m3)

Total Volume 

(m3)

Mean Volume 

(m3)

Boise NF, Squaw Creek, 2009 3,040 510 70 10 0.5

Clearwater NF, Potlatch River, 2010 3,490 580 60 10 0.3

Dixie NF, Mammoth Creek, 2010 780 260 20 10 0.3

Flathead NF, Flathead River, 2009 12,990 1,620 230 30 0.4

Mt. Baker-Snoqualmie NF, Baker River, 2009 1,500 1,500 150 150 0.6

Mt. Baker-Snoqualmie NF, Suiattle River, 2008 10,220 1,140 130 10 0.4

Olympic NF, Skokomish River, 2008 63,990 5,330 830 70 0.8

Payette NF, Calf Creek, 2009 4,140 1,040 110 30 0.6

Payette NF, Mann Creek, 2009 8,140 630 250 20 0.4

Rogue River-Siskiyou NF, Applegate River, 2010 1,840 610 20 10 0.1

Siuslaw NF, Alsea River, 2008 28,250 2,020 120 10 0.2

Six Rivers NF, Klamath River, 2009-2010 6,790 1,360 100 20 0.5

Umatilla NF, Granite Creek, 2008 2,940 420 40 10 0.2

Umatilla NF, Wall Creek, 2008 3,360 480 70 10 0.3

Umpqua NF, South Umpqua River, 2009 22,850 1,900 490 40 0.4

Willamette NF, Middle Fork Willamette River, 2010 7,550 630 110 10 0.4

Total 181,890 1,490 2,790 20 0.4

Site

Volume of Fill Removed Volume of Erosion in Crossings Mean 

Depth of 

Erosion 

(m3)

Sediment Delivery

Sediment delivery was calculated for each segment 

of road according to observations and the following 

equation (Luce and Black 1999, Cissel et al. 2012):

Treated Roads (97.4 km) Control Roads (92.5 km) Treated Roads (85.6 km) Control Roads (71.1 km)

Δ Road-Stream 

Hydrologic Connectivity -12.5 km (-62%) +1.2 km (+6%) -0.9 km (-3%) no change (-0.1%)

Δ Sediment Production 

from Road Surfaces -451 Mg/yr (-56%) -68 Mg/yr (-10%) -418 Mg/yr (-53%) -281 Mg/yr (-49%)

Δ Sediment Delivery from 

Road Surfaces -208 Mg/yr (-79%) +47 Mg/yr (+35%) -125 Mg/yr (-61%) -34 Mg/yr (-34%)

Δ Unit Sediment Delivery 

from Road Surfaces -2.1 Mg/km/yr (-79%) +0.5 Mg/km/yr (+34%) -1.5 Mg/km/yr (-61%) -0.4 Mg/km/yr (-34%)

Changes in Connectivity and Sediment, Pre-Treatment to Post-Storm Event

Decommissioned Roads (n = 15) SDRR Roads (n = 11)

E=B×L×S×V×R

E is the erosion for each road segment (kg/yr)

B is the base erosion rate (kg/m)

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

S is the slope of the road contributing to the drain point (m/m)

V is the vegetation cover factor for the flow path

R is the road surfacing factor

Road treatments have met or exceeded sediment 

production and delivery, and hydrologic 

connectivity expectations 

for both decommissioning 

and SDRR roads, with 

the exception of sediment 

Compared to the control roads, both production on SDRR roads.

decommissioning and SDRR treatments were effective 

at reducing sediment delivery to streams at most 

sites. This is due to decreases in sediment production 

and disconnection of roads from streams, with the 

former dominating SDRR roads.

Decommissioned 

Roads SDRR Roads Control Roads

Δ Road-Stream 

Hydrologic Connectivity

large decrease

small to moderate 

decrease small increase

Δ Sediment Production 

from Road Surfaces small to moderate 

decrease small decrease small increase

Δ Sediment Delivery 

from Road Surfaces

large decrease

small to moderate 

decrease

small to moderate 

increase

Expected Changes in Connectivity and Sediment, Pre-Treatment to PostStorm Event

Methods

The effectiveness of road treatments were measured using a 

before-after-control impact design (BACI). The GRAIP outputs 

and associated field observations were used as indicators of the 

state of risk.

A ~6 km sample of road was inventoried for both treatment and 

control sites. Control sites were selected based on their proximity 

and similarity to treated sites with respect to road construction 

methods, maintenance levels, geology, and hydrologic regimes. Each study site was inventoried before 

road treatments occurred, and again after a greater-than 7 year recurrence interval storm event. Treatment Control

Pre-Treat- ment

Post-Treat- ment

Post-Storm 

Event

Forest roads are frequently a major source of fine sediment delivery and mass wasting in steep terrains. The 

U.S. Forest Service operates over 616,000 kilometers of forest roads in a wide variety of landscapes. The USFS 

Legacy Roads Program has been working to address the environmental impact of this large road network by 

decommissioning or upgrading roads that historically have caused water quality impacts. The Legacy Roads 

Monitoring Project has developed a method and is monitoring a sample of 52 of these projects in order to 

establish the efficacy of the treatments over time and in a range of environments.

The Geomorphic Roads Analysis and Inventory Package (GRAIP) is a GPS 

based road inventory paired with a set of GIS tools designed to quantify the 

most common hydrologic and geomorphic problems associated with forest 

roads. GRAIP is combined with other field observations to evaluate:

Fine sediment delivery

Excavated stream crossings on decommissioned roads 

Mass wasting risks

Road surface erosion problems

Objective: To quantify the effectiveness of decommissioning (n=15) 

and storm damage risk reduction (SDRR; n=11) road treatments at reducing risk to watersheds.

•

•

•

•

Map of monitored Legacy Roads sites and 

other GRAIP studies.

Monitoring the Hydrologic and 

Geomorphic Effects of Forest 

Road Decommissioning and 

Road Improvements

Richard Cissel, Thomas Black, Nathan Nelson, and Charles H. Luce

U.S. Forest Service, Rocky Mountain Research Station, Boise, ID

Contact: rcissel@fs.fed.us or tblack@fs.fed.us

Brian Staab

U.S. Forest Service, Pacific Northwest Regional Office, Portland, OR

http://www.fs.fed.us/GRAIP