# Southwest Crown of the Continent

GRAIP Roads Assessment

Center Horse and Morrell / Trail Project Area, Poorman Creek, and Cold Creek Lolo, Helena, and Flathead National Forests , Montana

August 15 , 2014

Richard Cissel 1 

### , Tom Black 1 

### , Nathan Nelson 1 

### , and Ch arlie Luce 2

1 Hydrologist

2 Research Hydrologist

U.S. Forest Service Rocky Mountain Research Station 322 E. Front St, Suite 401 Boise, ID 83702Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

2 

## Table of Contents

Acknowledgments

................................ ................................ ................................ ................................ ......... 8

Executive Summary

................................ ................................ ................................ ................................ ....... 9 Center Horse and Morrell/Trail Project Area Summary

................................ ................................ ........... 9

Po orman Creek Summary

................................ ................................ ................................ ....................... 11 Cold Creek Summary

................................ ................................ ................................ ............................... 13 Jammer Roads Summary

................................ ................................ ................................ ........................ 14

Conclusions

................................ ................................ ................................ ................................ ............. 15

1.0 Background

................................ ................................ ................................ ................................ ..... 17

2.0 Objectives and Methods

................................ ................................ ................................ ................. 18

3.0 Study Areas

................................ ................................ ................................ ................................ ..... 19 Center Horse and Morrell/Trail Project Area

................................ ................................ .......................... 19

Poorman Creek

................................ ................................ ................................ ................................ ....... 21

Cold Creek

................................ ................................ ................................ ................................ ............... 23

4.0 Results

................................ ................................ ................................ ................................ ............. 25

4.1 Road

- Stream Hydrologic Connectivity

................................ ................................ ........................ 25

Center Horse Morrell

- Trail Project Area

................................ ................................ ............................. 26

Poorman Creek

................................ ................................ ................................ ................................ ... 26

Cold Creek

................................ ................................ ................................ ................................ ........... 27

4.2 Road Surface Fine Sediment Production and Delivery

................................ ............................... 28

Center Horse Morrell

- Trail Project Area

................................ ................................ ............................. 28

Poorman Creek

................................ ................................ ................................ ................................ ... 31

Cold Creek

................................ ................................ ................................ ................................ ........... 33

4.3 Downstream Sediment Accumulation

................................ ................................ ........................ 35

Center Horse Morrell

- Trail Project Area

................................ ................................ ............................. 35

Poorman Creek

................................ ................................ ................................ ................................ ... 40

Cold Creek

................................ ................................ ................................ ................................ ........... 44

4.4 Landslides

................................ ................................ ................................ ................................ .... 47

Center Horse Morrell

- Trail Project Area

................................ ................................ ............................. 47

Poorman Creek

................................ ................................ ................................ ................................ ... 51

Cold Creek

................................ ................................ ................................ ................................ ........... 55

4.5 Gullies and Gully Initiation Risk

................................ ................................ ................................ ... 59

Center Horse Morrell

- Trail P roject Area

................................ ................................ ............................. 60

Poorman Creek

................................ ................................ ................................ ................................ ... 63

Cold Creek

................................ ................................ ................................ ................................ ........... 65

4.6 Stream Crossin g Failure Risk

................................ ................................ ................................ ....... 67Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

3 Center Horse Morrell

- Trail Project Area

................................ ................................ ............................. 67

Poorman Creek

................................ ................................ ................................ ................................ ... 70

Cold Creek

................................ ................................ ................................ ................................ ........... 72

4.7 Drain Point Condition and Fill Erosion

................................ ................................ ........................ 74

Center Horse Morrell

- Trail Project Area

................................ ................................ ............................. 74

Poorman Creek

................................ ................................ ................................ ................................ ... 78

Cold Creek

................................ ................................ ................................ ................................ ........... 81

4.8 Risks by Maintenance Level

................................ ................................ ................................ ........ 84

5.0 Jammer Road Inventory and Observations

................................ ................................ ..................... 86

5.1 Complete Complex Inventory

................................ ................................ ................................ ..... 87

5.2 Stream Crossing Survey

................................ ................................ ................................ ............... 91

6.0 Summary and Conclusions

................................ ................................ ................................ .............. 95 Center Horse and Morrell/Trail Project Area Summary

................................ ................................ ......... 95 Poorman Creek Summary

................................ ................................ ................................ ....................... 97 Cold Creek Summary

................................ ................................ ................................ ............................... 98 Jammer Roads Summary

................................ ................................ ................................ ...................... 100

Conclusions

................................ ................................ ................................ ................................ ........... 101

References

................................ ................................ ................................ ................................ ................ 103

Appendix A: Road Risks by Maint enance Level Table

................................ ................................ ............... 106

Appendix B: Glossary of Selected Terms

................................ ................................ ................................ .. 107

Appendix C: GRAIP Data Management Plan

................................ ................................ ............................. 109



## List of Figures

Figure 1. Location of these watershed inventories and Legacy Roads Monitorin g Project sites in Region 1.

................................ ................................ ................................ ................................ ................................ .... 19
Figure 2. Land ownership and all roads within the Center Horse and M orrell/Trail project area.

............ 20
Figure 3. Geology of the Center Horse and Morrell/Trail project area.

................................ ..................... 20
Figure 4. Elevation and location of inventoried roads within the Center Horse and Morrell

- Trail p roject

area.

................................ ................................ ................................ ................................ ............................ 20
Figure 5. Geology of the Poorman Creek area..

................................ ................................ ......................... 21
Figure 6. Land ownership and all roads within the Poorman Creek area.

................................ .................. 22
Figure 7. Elevation and location of inventoried roads within the Poorman Creek area.

........................... 22
Figure 8. Geology of the Cold Creek area.

................................ ................................ ................................ .. 23
Figure 9. Land ownership and all roads within the Cold Creek area.

................................ ......................... 24
Fig ure 10. Elevation and location of inventoried roads within the Cold Creek area.

................................ . 24
Figure 11. Percen t total sediment delivered to streams by percent of drain points.

................................ 29
Figure 12. Sediment production and delivery by drain point type.

................................ ............................ 29Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

4 Figure 13. Fine sediment delivery to channels by road segment a nd drain point in the upper Little
Shanley and Black Canyon Creeks area.

................................ ................................ ................................ ...... 30
Figure 14. Percent total sediment delivered to streams by percent of drain points.

................................ 32
Figure 15. Sediment production and del ivery by drain point type.

................................ ............................ 32
Figure 16. Fine sediment delivery to channels by road segment and drai n point in central roaded portion

of the Cold Creek area.

................................ ................................ ................................ ............................... 32
Figure 17. Percent total sediment deliv ered to streams by percent of drain points.

................................ 33
Figure 18. Sediment production and delivery by drain point type.

................................ ............................ 33
Figure 19. Fine sediment delivery to channels by road segment and drain point in the central roaded
portion of the Cold Creek area.

................................ ................................ ................................ .................. 34
Figure 20. Sediment accumulation from all road

- rel ated sediment sources (road surface, gullies, landslides, and fill erosion) in the Center Horse and Morrell/Trail project area.

................................ ....... 37
Figure 21. Specific sediment from road surface sediment in the Center Horse and Morrell/Trail project

area.

................................ ................................ ................................ ................................ ............................ 38
Figure 22. Specific sediment from all road

- related sediment sources (road surface, gullies, landslides, and fill erosion) in the Center Horse and Morrell/Trail project area.

................................ ......................... 39
Figure 23. Sediment accumulation from all road

- related sediment sources (road surface, gullies,
landslides, and fill erosion) in the Poor man Creek area.

................................ ................................ ............ 41
Figure 24. Specific sediment from road surface sediment in the Poorman Creek area

. ............................ 41
Figure 25. Specific sediment from all road

- related sediment sources (road surface, gullies, lan dslides,
and fill erosion) in the Poorman Creek area.

................................ ................................ .............................. 43
Figure 26. Sediment accumulation from the r oad surface in the Cold Creek area.

................................ ... 45
Figure 27. Specific sediment from road surface sediment in th e Cold Creek area.

................................ ... 46
Figure 28. Observed landslides in the Spring Creek area of the Center Horse an d Morrell/Trail project

area.

................................ ................................ ................................ ................................ ............................ 48
Figure 29. Natural slope stability in the Spring Creek drainage of the Center Horse and Morrell/Trail
project area..

................................ ................................ ................................ ................................ ............... 49
Figure 30. Changes in slope stability risk in t he Spring Creek drainage of the Center Horse and Morrell/Trail project area.

................................ ................................ ................................ .......................... 50
Figure 31. Observed landslides in the Poorman Creek area..

................................ ................................ ..... 51
Figure 32. Natural slope stability in the central part of the Poorman Creek area.

................................ .... 52
Figure 33. Changes in slope stability risk in the central part of the Poo rman Creek area.

........................ 53
Figure 34. Observed landslides in the Cold Creek area.

................................ ................................ ............. 55
Figure 35. Natural slope stability in the Cold Creek area.

................................ ................................ .......... 56
Figure 36. Changes in slope stability risk in the central part of the Cold Creek area.

................................ 57
Figure 37. Locations of observed gullies and ESI risk at drain points, western portion of the Center Horse

area.

................................ ................................ ................................ ................................ ............................ 60
Figure 38. Length

- slope plot that shows the distribution of gullied and non

- gullied drain points.

........... 62
Figure 39. Locations of observed gullies and ESI risk at drain points, central portion of the Poorman

Creek area.

................................ ................................ ................................ ................................ .................. 63
Figure 40. Locations of observed gullies and ESI risk at drain points, central portion of the Cold Creek

area.

................................ ................................ ................................ ................................ ............................ 65Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

5 Figure 41. Distribution of SBI values for the Center Horse and Morrell/Trail project area.

...................... 67
Figure 42. The stream crossings with the highest risk of plugging and the most severe consequences of

failure in the Center Hor se and Morrell/Trail project area.

................................ ................................ ....... 68
Figure 43. Spring Creek diversion that delivered 41 Mg of sedi ment to the stream.

................................ 69
Figure 44. Distribution of SBI values for the Poorman Creek area.

................................ ............................ 70
Figure 45. The stream crossings with the highest risk of plugging and the most severe consequences of

failur e in the Poorman Creek area.

................................ ................................ ................................ ............. 70
Figure 46. Stream diversion at a natural ford in the western portion of the Poorman Creek area.

.......... 71
Figure 47. Distribution of SBI values for the Cold Creek area.

................................ ................................ ... 72
Figure 48. The stream crossings with the highest risk of plugging and the most severe consequences of

f ailure in the Cold Creek area.

................................ ................................ ................................ .................... 72
Figure 49. Specific drain point problems by drain type in the Cent er Horse and Morrell/Trail project area.

................................ ................................ ................................ ................................ ................................ .... 75
Figure 50. Drain point problems in the Spring Creek wate rshed.

................................ .............................. 76
Figure 51. Specific drain point problems by drain type in the Poorman Creek area.

................................ 78
Figure 52. Drain point problems in the western half of the Poorman Creek area.

................................ .... 79
Figure 53. Specific drain point problems by drain type in the Cold Creek area.

................................ ........ 81
Figure 54. Drain point problems in the Cold Creek area.

................................ ................................ ........... 82
Figure 55. Sediment delivery risks for all three areas.

................................ ................................ ............... 84
Figure 56. Fill erosion total mass and delivered mass for all three project areas.

................................ ..... 85
Figure 57. Gully and landslide risks for the Center Horse and Morrell/Trail project area.

........................ 85
Figure 58. Drain point problems for all three project areas.

................................ ................................ ...... 86
Figure 59. Jammer road l ocations in the Center Horse and Morrell/Trail project area, with the complete
surveyed complexes and the stream crossings that we surveyed.

................................ ............................ 87
Figure 60. Fine sediment delivery to channels by road segment and drain point in the upper Black
Canyon jammer road complex..

................................ ................................ ................................ .................. 88
Figure 61. Fill erosion and gullies in the Black Canyon jammer road complex.

................................ ......... 89
Figure 62. Stream crossings with observed fill erosion on jammer roads in the Center Horse and Morrell/Trail project area.

................................ ................................ ................................ .......................... 91
Figure 63. Probability graph output from the local fit regression in R.

................................ ...................... 93
Figure 64. Stream crossings on jammer roads with problems, including observed overtopping, diversion,
and culvert problems.

................................ ................................ ................................ ................................ . 93



## List of Tables

Table A. Summary of GRAIP

- predicted road risk predictions, Center Horse and Morrell/Trail project area.

................................ ................................ ................................ ................................ ................................ .... 10

Table B. Summary of GRAIP

- predicted road risk predictio ns, Poorman Creek area.

................................ .. 12

Table C. Summary of GRAIP

- predicted road risk predictions, Cold Creek area.

................................ .......... 13

Table D. Summary of ob served and predicted jammer road risks.

................................ ............................. 15Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

6 Table 1. Summary of effective road lengths by drain type for the Center Horse and Morrell/Trail Project

Area..

................................ ................................ ................................ ................................ ........................... 25

Table 2. Summary of effective road lengths by drain type for the Poorman Creek area.

.......................... 26

Table 3. Summary of effective road lengths by drain type for the Cold Creek area.

................................ .. 27

Table 4. Summary of sediment production and delivery at drain points in the Center Horse and Morrell/Trail Project Area.

................................ ................................ ................................ .......................... 29

Table 5 . Summary of sediment production and delivery at drain points in the Poorman Creek area.

....... 31

Table 6. Summary of sediment production and delivery at drain points in the Cold Creek area.

.............. 33

Table 7. Observed annual sediment yields for nearby areas.

................................ ................................ ..... 35

Table 8. Project area streams and sediment accumulation a nd specific sediment accumulation at the
stream mouth, calculated using only road surface

- related sediment and all road sediment sources (landslides, gullies, and fill erosion at drain points).

................................ ................................ ................... 36

Table 9. Project area streams and sediment accumulation and specific sediment accumulation at the
stream mouth, calculated using only road surface

- related sediment and all road sediment sources (landslides, gullies, and fill erosion at drain points).

................................ ................................ ................... 40

Table 10. Project area streams and sediment accumulation and specific sediment accumulation at the
stream mouth, calculated using only road surface

- related sediment.

................................ ....................... 44

Table 11. Number and types of observed landslides, as well as masses and volumes of sediment generated and delivered to the stream channel network in the Center Horse and Morrell/Trail project

area.

................................ ................................ ................................ ................................ ............................ 48

Table 12. Landslide risk changes in the Center Horse and Morrell/Trail project area by category and area.

................................ ................................ ................................ ................................ ................................ .... 50

Table 13. Number and types of observed landslides, as well as masses and volumes of sediment
generated and delivered to the stream channel network in the Poorman Creek area.

.............................. 51

Table 14. Landslide risk changes in the Poor man Creek area by category and area.

................................ 54

Table 15. Number and types of observed landslides, as well as masses and volumes of sediment
generated in the Cold Creek area.

................................ ................................ ................................ ............... 56

Table 16. Landslide risk changes in the Cold Creek area by category and area.

................................ ........ 58

Table 17. Inventoried gullies in the Center Horse and Morrell/Trail p roject area.

................................ ..... 61

Table 18. Sediment masses produced and delivered by active gullies in the Center Horse and Morrell/Trail
project area.

................................ ................................ ................................ ................................ ................ 61

Table 19. Distribution of drain points by ESI value, Center Horse and Morrell/Trail project area.

............ 62

Table 20. Further distribution information of drain points by ESI value.

................................ .................... 62

Table 21. Inventoried gullies in the Poorman Creek area.

................................ ................................ .......... 63

Table 22. Sediment masses produced and delivered by active gullies in the Poorman Creek area.

.......... 64

Table 23. Drain point and ESI statistics for the Poorman Creek area

................................ ......................... 64

Table 24. Inventoried gullies in the Cold Creek area.

................................ ................................ .................. 65

Table 25. Drain point and ESI statistics for the Cold Creek area.

................................ ................................ 66

Table 26. Drain point condition pro blems and fill erosion below drain points, Center Horse and Morrell/Trail project area.

................................ ................................ ................................ .......................... 74

Table 27. Fill erosion below drain points, volumes and masses, Center Horse and Morrell/Trail project

area.

................................ ................................ ................................ ................................ ............................ 77Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

7 Table 28. Drain point condition problems and fill erosion below drain points, Poorman Creek area.

....... 78

Table 29. Fill er osion below drain points, volumes and masses, Poorman Creek area.

............................. 79

Table 30. Drain point condition problems and fill erosion below drain points, Cold Creek area.

............... 81

Table 31. Fill erosion below drain points, volumes and masses, Cold Creek area.

................................ ..... 82

Table 32. Summary of sediment production and delivery at drain points on the jammer road complexes that were inventoried with GRAIP in the Center Horse and Morrell/Trail Project Area.

............................ 88

Table 33. Estimation of sediment delivery from road surfaces for all jammer roads in the Center Horse and Morrell/Trail project area, based on the road surface sediment delivery rate per kilometer from the
inventoried complexes.

................................ ................................ ................................ ............................... 89

Table 34. Mass wasting masses and d elivery for the observed mass wasting in the Black Canyon jammer
complex.

................................ ................................ ................................ ................................ ...................... 90

Table 35. Fill erosion statistics for the jammer road stream crossings observed in the Center Horse and Morrell/Trail project area.

................................ ................................ ................................ .......................... 92

Table 36. Stream crossings on jammer roads with problems in the Center Horse and Morrell/Trail project

area.

................................ ................................ ................................ ................................ ............................ 94

Table 37. Summary of GRAIP

- predicted road risk predictions, Center Horse and Morrell/Trail project area.

................................ ................................ ................................ ................................ ................................ .... 96

Table 38. Summary of GRAIP

- predicted road risk predictions, Poorman Creek area.

................................ 97

Table 39. Summary of GRAIP

- predicted road risk predictions, Cold Creek area.

................................ ........ 99

Table 40. Summary of observed and predicted jammer road risks.

................................ ......................... 100Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

8 

## Acknowledgments

Funding from the Southwest Crown of the Continent Collaborative and from the Great Northern Landscape Conservation Coopera tive (GNLCC) made this effort possible. We would like to thank the field crews (Adrianna Hummer, Benjamin Sundy, Austin Maphis, Ian Reeves, Amberle Keith, Dylan Esmonde, Erik Smith, and Hayley Connolly

- Newman) for carefully and diligently collecting this d ata. We would also like to thank the Seeley Lake office of the Lolo National Forest, and Amy Vernarsky in particular, the Lincoln office of the Helena National Forest, and the Condon office of the Flathead National Forest for helping to provide logistical support and bunkhouse space. Thanks also to Anne Carlson, Taylor Greenup, Shane Hendrickson, Bruce Rieman, Adam Switalski, Robert Al

- chokhachy, and Cameron Thomas

.

The full dataset from this project will be available to the public through the GNLCC websit e, at http://greatnorthernlcc.org/

.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

9 

## Executive Summary

Thi s report presents results from three watershed

- wide inventories and assessment s of roads in the Center Horse and Morrell/Trail project area , Poorman Creek watershed, and Cold Creek watershed i n western Montana using the Geomorphic Road Analysis and Inventory Package (GRAIP). GRAIP is a field

based model developed by the Forest Service Rocky Mountain Research Station and Utah State University. The primary objectives of the project were to:

• Ide ntify the current level of fine sediment delivery from roads to streams compared to
reference.

• Identify the types and sources of road

- related hydrologic risk in the watershed.

• Select and prioritize future restoration actions to improve watershed condit ions and move towards an ecologically and economically sustainable road system.

• Establish a pre

- treatment condition for comparison to the same roads after treatments have been applied in certain areas.

• Compare GRAIP results with modified PACFISH/INFISH Biological Opinion (PIBO) monitoring program instream observation data for the watershed, collected concurrently with the GRAIP inventory, to investigate the ability to link instream conditions with upslope processes. (This will be a separate report).

Fi eld inventory and modeling anal ysis of the public roads in the Center Horse and Morrell/Trail project area, the Poorman Creek watershed area, and the Cold Creek watershed area in the Southwest Crown of
the Continent in western Montana using the GRAIP model provided detailed, site specific data on
sediment

- related watershed impacts from roads. Impacts are both chronic, in terms of annual sediment input to streams, and pulsed, such as during storm events when road connectivity to the channel
networks is at it s maximum. Inventory data was collected on 77 9 km ( 484 mi) of road, including 10, 835 drain points, by two field crews during the summer months of 2012 and 2013 (June to October). Additionally, jammer

- type logging roads were sampled and their road

- stream in tersections were surveyed in the Center Horse and Morrell/Trail project area.

The GRAIP model was used to predict sediment risk and sediment

- related impacts from roads. The model predicts road to stream hydrologic connectivity, sediment delivery to stream s, downstream sediment accumulation, risks of shallow landslides caused by roads, gully initiation risk below drain points, and risks to road

- stream crossings ( Table s A

, B, and C )

. Inventory data is also used to locate and describe problems with existing d rain points. In addition, GRAIP model data will be compared to in

stream PIBO monitoring for these project area s in a separate document.



### Center Horse and Morrell/Trail Project Area Summary

In the Center Horse and Morrell/Trail project area, there were 40 7 km (253 mi) of road and 5061 drain points surveyed. Table A presents a summary of the findings for this project area. Hydrologic connectivity was found to be a relatively low 4% of all road length at 16 km out of 407 km (10 mi out of 252 mi). The model p redicted 21.4 Mg/yr of delivered road surface fine sediment to stream channels, which is 5% of the 456 Mg generated annually by the road surface. This sediment was delivered through 314 of 5061 (6%) drain points. There was 16.2 Mg/yr of delivery that occur red within 10 m of a stream crossing. This is 76% of all sediment delivery and 57% of all sediment produced within 10 m of a stream crossing.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

10 Specific sediment due to road surface

- related sediment for the whole Center Horse and Morrell/Trail project area was 0.10 Mg/km 2 /yr, or 1% of the observed total average fine sediment yield for five nearby areas as determined by reservoir coring or suspended sediment extrapolations. Including sediment delivered to streams through other sources (landslides, gullies, an d fill erosion at drain points), the specific sediment for the whole project area was 0.21 Mg/km 2 /yr, or about 2% of the observed average fine sediment yield for the nearby areas. Some heavily impacted stream reaches had road sediment delivery values as hi gh as 4.9 Mg/km 2 /yr with only road surface fine sediment, or 18.1 Mg/km 2 /yr including mass wasting sediment. Reaches in Shanley, Little Shanley, Blacks Canyon, and lower Spring Creeks showed particularly high specific sediment values above 0.3 Mg/km 2 /yr, o r 3% to 19% above the reference sediment yield.

There were 18 landslides observed by field crews in the course of the inventory, with a total volume of

1319 m 3 (1726 yd 3 ). Of those, 10 were road related. It was conservatively estimated that 176 Mg of landslide derived sediment has been delivered to streams, which is roughly half the rate of that from road surfaces over 20 years (8.8 Mg/yr). It would take about eight years for the fine sediment delivery
from road surfaces to equal the tot al mass of delivered sediment from landslides. Calibrated stability index modeling with SINMAP conservatively showed that 6 km 2 (2 mi 2 ), or 3%, of the watershed area was put at higher risk of shallow landslide initiation by road drainage.

Gullies were obs erved at 33 locations by field crews, totaling 208 m 3 (272 yd 3 ) in volume, and all occurring in wet swales. It was estimated that these gullies delivered 217 Mg of sediment to the stream channel, equivalent to half the rate of that from road surfaces over 20 years (11 Mg/yr). It would take
about ten years for the fine sediment delivery from road surfaces to equal the total mass of delivered
sediment from gullies

. Of 3713 applicable drain points, 587 (16%) had an elevated risk of gullying. The Table A

. Summary of GRAIP

- predicted road risk predictions, Center Horse and Morrell/Trail project

area.

Impact/Risk Type GRAIP Predicted Risks

Road

- Stream Hydrologic Connectiv ity 4% of road length, 16 km; 6% of drain points connected

Fine Sediment Delivery 5% of sediment produced, 21.4 Mg/yr

Sediment in Streams 0.21 Mg/km 2 /yr; 2% of average sediment yield for nearby areas

Landslide Risk Estimated 176 Mg of sediment delivered to streams, 3% of
watershed area with elevated risk due to roads
Gully Risk Estimated 11 Mg/yr of sediment delivered to streams, 16% of all drain points exceed ESI crit threshold
Stream Crossing Risks

- plug potential 27 sites (23%) with elevated risk (SBI > 2)

- fill at risk 6843 m 3 fill at risk, average 60 m 3 per crossing

- diversion potential 61 sites (42%) with diversion potential

Drain Point Problems 811 drain points (16% of all drain points) with problems, 61 m 3
of fill erosion (2% of drain points), estimated 2.9 Mg/yr of fill

delivered to streamsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

11 critical gully initiation index (ESI) was found to be 14. The average ESI for the points without gullies was 9, while it was 11 for the points with gullies. The gully occurrence rate for drain points that fell above the ESI threshold was 1.0% versus 0.5% for points that fell below the ESI threshold.

There were 116 stream crossings with culverts (as opposed to bridges or fords) recorded. The average blocking index (SBI) for these points was a moderate to low 1.9. There were 25 crossings with an
elevated SBI of 3. Two cro ssings had an SBI of 4, which is the highest possible value. The total calculated volume of fill at risk in an overtopping type event was 6840 m 3 (8950 yd 3 ). There were 55 stream crossings with the potential to divert stream flow from a plugged culvert dow n the road and onto unchanneled hillslopes. There were 14 stream crossings with an SBI of 3 or 4 and diversion potential

, four of which were observed to have already failed or be at risk for imminent failure. There was a total
of 824 m 3 (1077 yd 3 ) of fill at risk at these points. Six overtopped crossings were observed, five due to sediment plugging and one due to wood plugging. Three of those were due to undersized pipes, and one
delivered 26 m 3 (910 ft 3 ) to streams.

Of the 5061 recorded drain points, 811 (16%) had one or more problem of some type (e.g. blocked or crushed culvert, excess puddling on the road surface). Sumps had the highest rate of problems, with 11 of 24 (46%), followed by ditch relief culverts (155 of 392, 40%). Fill erosion was recorded a t 83 drain points (2%), with a total volume of 85 m 3 (3000 ft 3 ). Fill erosion was most common at non

- engineered
drains with 28 instances and 23 m 3 (820 ft 3 ). Stream crossings had 44 m 3 (1550 ft 3 ) eroded from 4 of 146 crossings (2%). It was estimated that f ill erosion delivered 87 Mg of sediment to the stream channel, or about a quarter of the rate of the of road surface sediment over 20 years (4.4 Mg/yr). It would take
about four years for the fine sediment delivery from road surfaces to equal the total mas s of delivered
sediment from fill erosion

.



### Poorman Creek Summary

In the P oorman Creek area, there were 174 km (108 mi) of road and 2 190 drain points surveyed. Table B presents a summary of the findings for this project area. Hydrologic connectivity wa s fo und to be a relatively low 4.7% of all road length at 8 km out of 17 4 km ( 5 mi out of 10 6 mi). The model predicted

11.5 Mg/yr of delivered road surface fine sedimen t to stream channels, which is 4.6% of the 247 Mg generated annually by the road surface. Th is sediment was delivered through 97 of 2190 (4%) drain points. There was 5.6 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 49 % of all sediment delivery and 77 % of all sediment produced within 10 m of a stream crossing.

Specifi c sediment due to road surface

- related sediment for the whole Poorman Creek area was 0. 11 Mg/km 2 /yr, or 1 % of the observed total average fine sediment yield for five nearby areas as determined by reservoir coring or suspended sediment extrapolations. Inclu ding sediment delivered to streams through other sources (landslides, gullies, and fill erosion at drain points), the specific sediment for the whole project area was 0.1 9 Mg/km 2 /yr, or about 2 % of the observed average fine sediment yield for the nearby ar eas. The most heavily impacted stream reaches had road sedimen t delivery values as high

as 0.8 Mg/km 2 /yr with only road surface fine sediment, or 4.0 Mg/km 2 /yr including mass wasting

sediment.

There were 5 landslides observed by field crews in the course of the inventory, with a total volume of

252 m 3 (329 yd 3 ). All were road related. It was conservatively estimated that 91 Mg of landslide derived sediment has been delivered to streams, which is roughly half the rate of sediment from road surfacesSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

12 over 20 years (4.5 Mg/yr). It would take about 8 years for the fine sediment delivery from road surfaces to equal the total mass of delivered sediment from landslides. Calibrated stability index modeling with SINMAP conservatively showed that 3 km 2 (1 mi 2 ), or 2%, of the watershed area was put at higher risk of shallow landslide initiation by road drainage.

Gullies were observed at 7 locati ons by field crews, totaling 157 m 3 (206 yd 3 ) in volume, with none occurring in wet swales. It was estimated that these gullies delivered 4 Mg of sediment to the stream channel, which is negligible compared to the rate of road surfaces over 20 years (0.2 Mg/yr). It would
take less than one year for the fine sediment delivery from road surfaces to equal the total mass of
delivered sediment from gullies

. There were too few gullies to determine an ESI crit , suggesting that the gully initiation risks here may be very low. The average ESI across the Poorman Creek area was 8.

There were 2 9 stream crossings with culverts (as opposed to bridges or fords) recorded. The average blocking index (SBI) for these points was a moderate to low 1.7 . There were 5 crossings with an elevated SBI of 3. No crossings had an SBI of 4, which is the highest possible value. The total calculated v olume of fill at risk in an overtopping type event was 1 399 m 3 (1 83 0 yd 3 ). There were eight stream crossings with the potential to divert stream flow down the road and onto unchanneled hillslopes. There was one stream crossing with an SBI of 3 and diversio n potential . There was a total of 21 m 3 (27 yd 3 ) of fill at risk at this point. Two natural ford type crossings were observed to divert flow down the road, though no major erosion was observed at the time of the survey.

Of the 2190 recorded drain points, 270 (12%) had one or more problem of some type (e.g. blocked or crushed culvert, excess puddling on the road surface). Ditch relief culverts had the h ighest rate of problems, with 18 of 56 (32 %), followed by broad based dips ( 120 of 412 , 29%). Fill erosion was recorded at 22 drain point s (1%), with a total volume of 11 m 3 ( 400 ft 3 ). Fill erosion was most common at Table B

. Summary of GRAIP

- predicted road risk predictions, Poorman Creek area.

Impact/Risk Type GRAIP Predicted Risks

Road

- Strea m Hydrologic Connectivity 4.7% of road length, 8 km; 4% of drain points connected

Fine Sediment Delivery 4.6% of sediment produced, 11.5 Mg/yr

Sediment in Streams 0.19 Mg/km 2 /yr; 2% of average sediment yield for nearby areas

Landslide Risk Estimated 91 Mg of sediment delivered to streams, 2.2% of watershed area with possible elevated risk due to roads

Gully Risk Estimated 0.2 Mg/yr of sediment delivered to streams, too few gullies to determine ESI crit

Stream Crossing Risks

- plug potential 5 s ites (17%) with elevated risk (SBI > 2)

- fill at risk 1399 m 3 fill at risk, average of 48 m 3 per crossing

- diversion potential 8 sites (1 7 %) with diversion potential

Drain Point Problems 270 drain points (12% of all drain points) with prob lems, 11 m 3 of fill erosion (1% of drain points), estimated 0.2 Mg/yr of fill erosion

delivered to streamsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

13 non

- engineered drains with 16 instances and 8 m 3 ( 300 ft 3 ). It was estimated that fill erosion delivered 3 Mg of sediment to the stream channel, which is negligible compared the amount of road surface sediment over 20 years (0. 2 Mg/yr).



### Cold Creek Summary

In the Cold Creek area, there were 198 km (123 mi) of road and 3584 drain points surveyed. Table C presents a summary of the findings for this p roject area. Hydrologic connectivity was found to be a relatively low 4% of all road length at 9 km out of 198 km (6 mi out of 123 mi). The model predicted 9.8 Mg/yr of delivered road surface fine sediment to stream channels, which is 6% of the 162 Mg gene rated annually by the road surface. This sediment was delivered through 205 of 3584 (6%) drain points. There was 6.6 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 67% of all sediment delivery and 75% of all sediment produced wit hin 10 m of a stream crossing.

Specific sediment due to road surface

- related sediment for the whole Cold Creek area was 0.1 Mg/km 2 /yr, or 1% of the observed total average fin e sediment yield for five nearby areas as determined by reservoir coring or suspended sediment extrapolations. No other sources were observed to deliver sediment to streams. The most heavily impacted stream reaches had road sediment delivery values as high as 1.1 Mg/km 2 /yr.

There were 9 landslides observed by field crews in the course of the inventory, with a total volume of

175 m 3 (229 yd 3 ). Only one landslide was not road related. No landslide sediment was observed to have
been delivered to streams. Cali brated stability index modeling with SINMAP conservatively showed that Table C

. Summary of GRAIP

- predicted road risk predictions, Cold Creek area.

Impact/Risk Type GRAIP Predicted Risks

Road

- Stream Hydrologic Connectivity 4% of road length, 9 km; 6% of drain point s connected

Fine Sediment Delivery 4% of sediment produced, 9.8 Mg/yr

Sediment in Streams 0.10 Mg/km2/yr; 1% of average sediment yield for nearby areas

Landslide Risk No landslide sediment delivered to streams; 0.6% of watershed area with possible eleva ted risk due to roads

Gully Risk No gully sediment delivered to streams, too few gullies to
determine ESI crit Stream Crossing Risks

- plug potential 28 sites (39%) with elevated risk (SBI ≥ 2)

- fill at risk 2095 m 3 fill at risk, average of 31 m 3 per crossing

- diversion potential 39 (34%) sites with diversion potential

Drain Point Problems 284 drain point s (8% of all drain points) with problems, 3 m 3 of fill erosion (1% of drain points), estimated 0.005 Mg/yr of fill erosion

delivered to streamsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

14 0.6 km 2 (0.2 mi 2 ), or 0.6%, of the watershed area was put at higher risk of shallow landslide initiation by road drainage.

Gullies were observed at 3 locations by field crews, totaling 5 m 3 (7 yd 3 ) in volume, with none occurring in wet swales. No gullies were observed to deliver sediment to the stream channel in Cold Creek. There were too few gullies to determine an ESI crit , suggesting that the gully initiation risks here may be very
lo w. The average ESI across the Cold Creek area was 4.

There were 71 stream crossings with culverts (as opposed to bridges or fords) recorded. The average blocking index (SBI) for these points was a moderate to low 2.3. There were 26 crossings with an
eleva ted SBI of 3. Two crossings had an SBI of 4, which is the highest possible value. The total calculated volume of fill at risk in an overtopping type event was 2090 m 3 (2730 yd 3 ). There were 39 stream crossings with the potential to divert stream flow from a plugged culvert down the road and onto unchanneled hillslopes. There were 14 crossings with an SBI of 3 or 4 and diversion potential. There was
a total of 332 m 3 (434 yd 3 ) of fill at risk at these points. Of those 14 crossings, half received the stream
f low from the ditch, though this appeared to be intentional.

Of the 3584 recorded drain points, 284 (8%) had one or more problem of some type (e.g. blocked or crushed culvert, excess puddling on the road surface). Stream crossings had the highest rate of

p roblems, with 45 of 115 (39%), followed by ditch relief culverts (80 of 266, 30%). Fill erosion was recorded at 23 drain points (1%), with a total volume of 3 m 3 (110 ft 3 ). Fill erosion was most common at broad based dips with 18 instances and 3 m 3 (90 ft 3 ). It was estimated that fill erosion delivered 0.5 Mg of sediment to the stream channel, which is negligible compared the amount of road surface sediment over 20 years (0.005 Mg/yr).



### Jammer Roads Summary

Two complete jammer road complexes totaling 19 km (11 mi) of road and 325 drain points in the Center Horse project area were inventoried using the GRAIP method. These vegetated and shallow

- slope roads delivered 0.02 Mg/yr, which is 2% of the 1 Mg/yr generated on the road surfaces ( Table D ). If this
delive ry rate is applied to all jammer roads in the Center Horse and Morrell/Trail project area , then it can be expected that these roads deliver less than 1 M g/yr from the road surface. A small stream diversion was observed that resulted in two delivering gulli es (29 Mg) and two non

- engineered points with fill erosion, one of which delivered to the stream (23 Mg). There were no other observed instances of mass wasting, including anything not related to the stream crossing or any landslides.

We conducted a censu s of all of the stream crossings on jammer roads in the Center Horse and Morrell/Trail project area, for a total of 71 crossings. Streams were defined as continuous features with a bed, banks, and evidence of flow for some part of most years. There were 61 natural ford

- type crossings (no infrastructure) and ten crossings with culverts. Nine crossings (13%) were observed to have evidence of stream diversion or other problems. There were 31 crossings (44%) with fill erosion, totaling 207 m 3 (7300 ft 3 ), all of which was assumed to deliver (331 Mg). This was roughly equivalent to
that from road surfaces on non

- jammer roads in the Center Horse and Morrell/Trail project area over 20 years (17 Mg/yr).

The average volume of fill available to erode at each crossing was estimated to be 12 m 3 (16 yd 3 ) per crossing. Of this amount, an average of 3 m 3 (4 yd 3 ) per crossing has already been eroded, suggestingSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

15 that 25% of possible erosion has already occurred, and up to 75% remains (about 600 m 3 or 22,000 ft 3 ).
Differences in the shape and construction of each stream crossing, and the timing of high flows and transport capacity of the streams, suggest that each stream crossing will respond at a different rate, and may include some deposition. It was found that on hillslopes of greater than about 40%, every stream crossing in the Center Horse area had fill erosion, suggesting that the stream crossings on steeper slopes may be at higher risk of failure than those on lower slopes.



### Conclusions

Unde r the observed conditions, the GRAIP inventories in the Southwest Crown of the Continent suggest
low risk across the measured metrics when considered at the watershed scale. The Center Horse and Morrell/Trail project area had the most risk overall. There a re two other non

- watershed GRAIP sites in the northern Rockies; one site in the Clearwater National Forest ( Cissel et al. 2011A ), and one in the Gallatin National Forest ( Cissel et al. 2011B ) . Compared to these sites, these three watershed s fall within
the typical range for landslide risk, gully risk, stream crossing plugging potential and diversion potential, and drain point problems and fill erosion for both sites. The stream crossing fill at risk is slightly higher in the Center Horse and Morrell/Trail p roject area and Poorman Creek, but within the typical range in Col d Creek. The Clearwater site had much higher road surface sediment delivery and hydrologic connectivity, while this data is in range of the Gallatin site. Compared to a site in the Olympic N ational Forest in western Washington ( Cissel et al. 2011C ), which is considered to have high risk in all metrics, the Center Horse and Morrell/Trail project area has low to moderately low risk in all areas.

Although sediment delivery risk related to road s is low from the watershed perspective, several road segments were identified that may need treatment to minimize sediment delivery effects that are significant at the stream reach scale. Depending on downstream habitat and species presence, fine Table D

. Summary of observed and predicted jammer road risks.

Impact/Risk Type Predicted Risks

Complete Complex Inventory Fine Sediment Delivery 2% of sediment produced; 0.02 Mg/yr

Estimated Sediment Delivery for All Jammer
Roads 0.4 Mg/yr, using a delivery rate o f 0.001 Mg/yr/km

Gullies and Fill Erosion
Risks 29 Mg delivered to streams from gullies, 23 Mg delivered to streams from fill erosion, estimated 3 Mg/yr

Stream Crossing Survey Fill Erosion Risks,
Observed 44% of stream crossings with fill erosion, estimated 17 Mg/yr

delivered to streams

Fill Erosion Risks, Future
Estimated 25% of estimated risk has been realized, up to 75% (600 m 3 ) may remain

Other Problems 9 crossings (13%) with observed stream diversions or other problemsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

16 sediment delivery effects may be significant at a stream reach scale. Ongoing work comparing aquatic habitat conditions between managed and unmanaged reaches using PIBO data will help refine these questions.

Road maintenance level appears to have a small to moder ate effect on the various risk metrics. Higher maintenance levels (ML 3 and 4; more traffic, more frequent and more intense maintenance) had somewhat more sediment delivered from their road surfaces, but mass wasting risks were lower. Lower
maintenance lev el roads (ML 1 and 2; little to no traffic, little to no maintenance) had higher mass wasting risks. These relationships suggest that traffic has an important effect on road surface fine sediment production, but regular more intense maintenance can prevent mass wasting problems. On some lower maintenance level roads, it may be beneficial to treat spots that are at high risk of erosion.

The sediment delivery from fill erosion and mass wasting at jammer road

- stream intersections in the
Center Horse and Morre ll/Trail project area was on the same scale as the road surface fine sediment delivery from non

- jammer roads in the same area. The highly vegetated and low slope jammer road surfaces themselves did not appear to have significant impacts. Treatments to jamm er roads should be focused on the roads with stream crossings. However, the consequences of removing vegetation on the road surface to access the jammer road stream crossings may increase the contributions of their surface
fine sediment to streams. Data to be collected in the summer of 2014 may help to further understand the causes and distribution of erosion at stream crossings on jammer roads.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

17 

## 1.0 Background

The National Forest Transportation System represents a major public investment and provides ma ny benefits to forest managers and the public. Roads, however, also have negative effects on water quality, aquatic ecosystems, and other resources. There is currently a large backlog of unfunded maintenance, improvement, and decommissioning work needed o n National Forest roads. Critical components of the infrastructure (e.g., culverts) are also nearing or have exceeded their life

- expectancy, adding further risk and impacts to watershed and aquatic resources.

The Center Horse and Morrell/Trail project are a , and the Poorman Creek and Cold Creek watersheds are part of an ongoing collaborative project in the southwest Crown of the Continent of western Montana designed to assess the impacts of forest roads and jammer

- type logging roads on aquatic habitat.
Coll aborators include the Lolo, Helena, and Flathead National Forests; Wildlands CPR; the Clearwater Resource Council; The Wilderness Society; and many others. Cottonwood Creek within the Center Horse area is listed under a 1996 TMDL for sediment ( Montana Depa rtment of Environmental Quality 2008 ).

The GRAIP data collection and analysis procedure provides land managers with field

- based data that captures the extent to which roads and associated features deliver uncharacteristic amounts of fine
sediment to the s tream network. GRAIP identified precise locations where sediment delivery was occurring, where drainage features were compromised, and where road maintenance or decommissioning was required. This detailed information can then be used to prioritize actions to minimize adverse watershed and aquatic impacts from roads.

All roads that were managed by the Forest Service or were otherwise located on public la nds were targeted for inventory in 2012 and 2013, including jammer

- type roads which were inventoried in 2 013

. Roads on existing geographic information system (GIS) layers were targeted for inventory (about 1280 km, 790 mi in all three areas ). However, some additional previously unmapped roads were found and
inventoried d uring the course of the study. J ammer

- t ype roads totaled 380 km (230 mi) in existing GIS layers, and these were sampled as opposed to completely inventoried . A total of 407 km (253 mi) of road was inventoried within the Center Horse and Morrell/Trail project area boundary. W ithin the

Poorman Cr eek area, 17 4 km (10 8 mi) were surveyed. Within Cold Creek, there were 198 km (123 mi) of road surveyed. In the Center Horse Morrell/Trail project area, 18 km (11 mi) of jammer roads were surveyed

. The majority of field work has been completed, and work in 2014 includes closer examination of jammer road stream crossings. Field work in 2012 began on June 5 and w as completed on October

16

. Work began in 2013 on June 5 and was completed on October 25. Two crews collected data by vehicle or by foot each season

.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

18 

## 2.0 Objectives and Methods

GRAIP is formulated to assess the geomorphic and hydrologic impacts of roads, their physical condition, and associated stream connections. It is a relatively intensive field

- based method that provides detailed information design ed to improve understanding of the effect of roads on sediment routing watershed processes. Specifically, th is project was designed to address the following in the three project areas :

 Identify the current level of fine sediment delivery from roads to stre ams compared to
reference.

 Identify the types and sources of road

- related sediment risk in the watershed.

 Select and prioritize future restoration actions to improve watershed conditions and move towards an ecologically and economically sustainable road sy stem.

 Establish a pre

- treatment condition for comparison to the same roads after treatments have been applied in certain areas.

 Compare GRAIP results with PIBO data for the watershed collected concurrently with the GRAIP inventory to investigate the abilit y to link instream condition with upslope processes. (This will be a separate report).

GRAIP is used to inventory and model the risk profile of each of the road segments and drain point features included in the study. The GRAIP system consists of a detaile d, field

- based road inventory protocol combined with a suite of GIS models. The inventory is used to systematically describe the hydrology and condition of a road system with Geographic Positioning System (GPS) technology and automated data forms ( Black et al. 2012 ). The GIS applications couple field data with GIS terrain analysis tools to analyze road

- stream hydrologic connectivity, fine sediment production and delivery, downstream sediment accumulation, stream sediment input, shallow landslide risk potent ial 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 ( Cissel et al. 2012 ).Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

19 

## 3.0 Study Areas

These three projects areas (Center Horse and Morrell/Trail, Poorman Creek, and Cold Creek) are the first
watershed

- scale GRAIP inventories to be completed in the U.S. Forest Service Northern Region (Region
1; Figure 1 ). Other inventorie s have been completed or are underway in Oregon, Washington, California and Idaho (Regions 6 , 5, and 4, respectively). Additionally, there is an ongoing region

- and western U.S.

- wide Legacy R oads monitoring project, encompassing eight sites in Region 1 whe re road decommissioning, storage, and storm damage risk reduction has been or will be implemented, including two sites within the Lolo National Forest (in the Fishtrap Creek watershed) and one site in the Flathead National Forest (at Hungry Horse Reservoir )

.



### Center Horse and Morrell/Trail Project Area

The Center Horse and Morrell/Trail project area is located within the Clearwater River w atershed, which is located east of Seeley Lake, MT, and drains into the Blackfoot River and then the Clark Fork River i n western Montana. The project area watersheds drain about 220 km 2 (80 mi 2 ; 53,100 aces), and the
Clearwater River drains about 3140 km 2 (1210 mi 2 ; 775,900 acres).

The project area covers two main geologic units ( Figure 2 ). Glacial deposits and other all uvium cover the valley bottoms (about 139 km 2 or 54 mi 2 ), and carbonates and quartzite of the Mesoproterozoic Belt Supergroup underlay the valley walls and ridges (131 km 2 or 51 mi 2 ). There are two faults in the area, running roughly northwest

- southeast ( L udington et al. 2005 ). Terrain in the project area is heavily influenced by Pleistocene glaciation, with steep valley walls and flat hummocky valley bottoms. Elevations in the project area range from 1230 m (4040 ft) to 2620 m (8600 ft), and inventoried ro ads range from 1270 m (4170 ft) to 2360 m (7740 ft). Average annual precipitation in the project area ranges from 460 mm/yr (18 in/yr) to 1880 mm/yr (74 in/yr; Montana Department of Environmental Quality

2011 ). Figure 1

. Location of these watershed inventories and Legacy Roads Monitoring Proje ct sites in Region 1.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

20 The Center Horse and Morrell/Trail pro ject area is comprised of primarily federally owned and managed land ( Figure 3 ). The Forest Service manages 240 km 2 (90 mi 2 , 59,300 acres, 94%); 7 km 2 (3 mi2, 1700 acres, 3%) is private; the remaining 9 km 2 (3 mi 2 , 2200 acres, 4%) managed by the Bureau of Land Management and the State of Montana. Figure 3

. Geology of the Center Horse and Morrell/Trail project

area. Figure 2

. Land ownership and all roads within the Center Horse and Morrell/Trail project area. The watershed boundary is buffered by 500 m (1640 ft).

Figure 4

. Elevation and location
of inventoried roads within the
Center Horse and Morrell

- Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

21 All roads on federal and state lands were inventoried, for a total of 407 km (253 mi), with the exception of jammer

- type logging roads (410 km, 250 mi), which were sampled in 2013 instead of fully
inventoried . Abo ut 30 km (19 mi) of road had been previously mapped, but was found to not exist on the ground. Conversely, about 20 km (12 mi) of road was inventoried that was not previously mapped ( Figure 4 ). About 10 km (6 mi) of mapped road had been recontoured, and wa s not inventoried.



### Poorman Creek

Poorman Creek is also located with in the Blackfoot River watershed, south of Lincoln, MT. The Poorman
Creek watershed drains about 100 km 2 (40 mi 2 , 26,000 acres). The Blackfoot River drains about 6200
km 2 (2400 mi 2 , 1.5 m illion acres).

Poorman Creek covers three main geologic units ( Figure 5 ). A lluvium cover s the lowest valley bottoms (about 8 km 2 or 3 mi 2 ). C arbonates of the Mesoproterozoic Belt Supergroup (85 km 2 or 33 mi 2 ) and igneous intrusive diorite of possibly Cr etaceous origin underlay the bulk of the rest of the watershe d ( 39
km 2 or 15 mi 2 ; Ludington et al. 2005 ). Terrain in Poorman Creek is not as heavily influenced by glaciation as the other two project areas

. Valley walls are shallower, and valley bottoms are less broad. The terrain is more dissected by streams. Elevations in the project area range from 1390 m ( 4550 ft) to 2 350 m ( 7720 ft), and inventoried roads range from 1 400 m (4 600 ft) to 23 40 m (7 670 ft). Average annual precipitation in the project area r anges from 490 mm/yr (19 in/yr) to 760 mm/yr ( 30 in/yr; Montana Department of Environmental Quality 2011 ).

The Poorman Creek area is comprised of primarily federally owned and managed land ( Figure 6 ). The Forest Service manages 96 km 2 ( 37 mi 2

, 23,600 acre s, 93 %); the remaining 9 km 2 (3 mi 2 , 2130 acres, 7 %) is private

. Figure 5

. Geology of the
Poorman Creek area. The
alluviu m shown in the southern side of the valley is probably actually located on the valley floor.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

22 All roads on federal and state lands were inventoried, for a total of 17 4 km ( 10 6 mi). About 47 km (2 9 mi) of road had been previously mapped, but was found to not exist on the ground. Man y of these may
be ATV trails. Conversely, about 20 km (12 mi) of road was inventoried that was not previously mapped ( Figure 7 ).

Figure 7

. Elevation and location of inventoried roads within the Poorman Creek area. Figure 6

. Land ownership
and all roads within the
Poorman Creek area. The watershed boundary is buffered by 500 m.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

23 

### Cold Creek

Cold Creek is located with in the Swan River watershed, and is located west of Condon, MT. The Swan

River drains i nto the Flathead River. The Cold Creek watershed drains about 90 km 2 (30 mi 2 , 21,000 acres), and the Swan River drains about 1810 km 2 (700 mi 2 , 448,000 acres)

.

Cold Creek covers two main geologic units ( Figure 8 ). Glacial deposits and other alluvium cove r the valley bottoms (about 28 km 2 or 11 mi 2 ), and carbonates and quartzite of the Mesoproterozoic Belt Supergroup underlay the higher elevations ( 104 km 2 or 40 mi 2 ; Ludington et al. 2005 ). Terrain in the project area is heavily influenced by Pleistocene g laciation, with steep valley walls and flat hummocky valley bottoms. The bulk of the roads in Cold Creek are in the hummocky zone. Elevations in the project area range from 1070 m ( 3520 ft) to 2 58 0 m (8 470 ft), and inventoried roads range from 1 080 m ( 3540 ft) to 1730 m ( 5670 ft). Average annual precipitation in the project area ranges from 560 mm/yr ( 22 in/yr) to 1830 mm/yr (72 in/yr; Montana Department of Environmental Quality 2011 ).

The Cold Creek area is comprised of primarily federally owned and mana ged land ( Figure 9 ). The Forest Service manages 116 km 2 ( 45 mi 2

, 28,660 acres, 93 %); the remaining 9 km 2 (3 mi 2 , 2130 acres, 7 %) is private

. Figure 8

. Geology of the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

24 All roads on federal and state lands were inventoried, for a total of 198 km ( 123 mi). About 27 km (17 mi) of roa d had been previously mapped, but was found to not exist on the ground. Conversely, the same length of road was inventoried that was not previously mapped (27 km or 17 mi; Figure 10 ). Some of this may be on private land.

Figure 9

. Land ownership and all roads within the Cold Creek area. The wa tershed boundary is buffered by 500 m.

Figure 10

. Elevation and location of inventoried roads within the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

25 

## 4.0 Results

A total of 10, 835 dra in points, 14, 912 road lines, and 3 110 other associated features (including 4 4 gullies, 32 landslides, and 18 80 photo points) were inventoried in nine months of field work over the
summers of 2012 and 2013 by two field crews. Each crew collected an average of 3 km (1.8 mi) of road per day. Data analysis provides specific information on the condition and function of 7 79 km ( 4 84 mi) of roads ( Figure s 4, 7, and 10 ). These results are for the non

- jammer roads in the three areas. Jammer
roads are discussed in in section 5.0

. GRAIP inventory and data modeling tools were used to characterize the following types of impacts and risks:

 Road

- stream hydrologic connectivity

 Fine sediment production and delivery

 Downstream sediment accumulation

 Shallow landslide risk

 Gull y initiation risk

 Stream crossing failure risk

 Drain point condition



### 4.1 Road

- Stream Hydrologic Connectivity

Roads can intercept shallow groundwater and convert it to surface runoff, resulting in local hydrologic impacts when that water is discharged dire ctly 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

inc rease peak flows ( Jones and Grant 1996 ).

Table 1

. Summary of effective road lengths by drain type for the Center Horse and Morrell/Trail Project Area . Sumps cannot be
stream connected, while streams crossings are stream connecte d by definition.

Drain Type All Drain Points Connected Drain Points Not Connected Drain Points % Length

Connected Count Average Contributing Length (m) ∑

Contributing Length (m) Count Average Contributing Length (m) ∑

Contributing Length (m) Count Average Contributing Length (m) ∑

Contributing Length (m)

Broad Based Dip 1413 110 157,650 42 110 4490 1371 110 153,160 3%

Diffuse Drain 931 90 84,710 11 60 700 920 90 84,010 0.8%

Ditch Relief

Culvert 392 60 24,160 30 30 1020 362 60 23,140 4%

Excavated
Stream Crossing 4 50 180 4 50 180 0 0 0 100%

Lead Off Ditch 135 70 9640 13 50 580 122 70 9050 6%

Non

- Engineered

Drain 1102 60 67,090 39 60 2300 1063 60 64,7 80 3%

Stream Crossing 146 40 5680 146 40 5680 0 0 0 100%

Sump 24 140 3280 0 0 0 24 140 3280 0%

Water Bar 914 60 54,850 29 50 1470 885 60 53,3780 3%

All Drains 5061 80 407,230 314 50 16,420 4747 80 390,800 4%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

26 The hydrologically

- connected portion of th e road system is calculated in GRAIP using field observations of connection at each drain point 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 chann el.



### Center Horse Morrell

- Trail Project Area

In the Center Horse and Morrell

- Trail project area, a total of 16.4 km (10.2 mi) out of 407 km (252 mi) of inventoried road (4%) was hydrologically connected to the stream network. Broad based dips and non

engin eered drains were the most common types of drainage features (1413 and 1102 features, respectively), and, along with diffusely draining road segments (931 features) and water bars (914 features), drained 90% (364 km, 226 mi) of the road network ( Table 1 ). The bulk of the hydrologic connectivity occurred at stream crossings and broad based dips. There were 146 stream crossings, and they drained 6 km (4 mi) of the road network, all of which was connected. The broad based dips drained 158 km (98 mi) of the roa d network, 4 km (2 mi) of which was connected to the stream network.



### Poorman Creek

In Poorman Creek , a total of 8.1 km ( 5.0 mi) out of 17 4 km ( 10 8 mi) of inventoried road ( 5 %) was hydrologically connected to the strea m network. Broad based dips ( 412 features), diffuse drains ( 417 features), non

- engineered drains ( 693 features), and water bars (549 features) were the most common types of drainage features , and drained 92 % ( 1 60 km, 100 mi) of the road network ( Table 2 ). The bulk of the hydrologic connectivity occurred at stream crossings , ditch relief culverts, and non

- engineered
drains . There were 53 stream crossings, and they drained 4 km ( 2 mi) of the road network, all of which
was connected. The ditch relief culverts drained 9 km (5 mi) of the road network, 2 km (1 mi) of which

Table 2

. Summary of effective road lengths by drain type for the Poorman Creek area. Sumps cannot be stream connected, while
streams crossings are s tream connected by definition.

Drain Type All Drain Points Connected Drain Points Not Connected Drain Points
% Length
Connected Count Mean Contributing Length (m) Σ

Contributing Length (m) Count Mean Contributing Length (m) Σ

Contributing Length (m) Count Mean Contributing Length (m) Σ

Contributing Length (m)

Broad Based Dip 412 120 49,750 8 120 930 404 120 48,820 2%

Diffuse Drain 417 110 47,210 2 50 100 415 110 47,110 0.2%

Ditch Relief
Culvert 56 160 8710 9 170 1550 47 150 7160 18%

Lead Off Ditch 8 120 950 0 0 0 8 120 950 0%

Non

- Engineered

Drain 693 60 42,830 24 70 1600 669 60 41,220 4%

Stream Crossing 53 70 3900 53 70 3900 0 0 0 100%

Sump 2 60 130 0 0 0 2 60 130 0%

Water bar 549 40 20,620 1 30 30 548 40 20,590 0.1%

All Drains 2190 80 174,090 97 80 8110 2093 80 165,980 5%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

27 were connected to the stream network. The non

- engineered drains drained 43 km (27 mi) of the road network, 2 km ( 1 mi) of which was connected to the stream network.



### Cold Creek

In the Cold Cree k area, a total of 8.7 km (5.4 mi) out of 198 km (123 mi) of inventoried road (4%) was hydrologically connected to the stream network. Broad based dips and non

- engineered drains were the most common types of drainage features ( 1050 and 1097 features, respe ctively), and, along with diffusely draining road segments ( 670 features) and ditch relief culverts ( 266 features), drained 90% ( 178 km, 111 mi) of the road network ( Table 3 ). The bulk of the hydrologic connectivity occurred at stream crossings , ditch reli ef culverts, and broad based dips. There were 115 stream crossings, and they
drained 4 km ( 3 mi) of the road network, all of which was connected. The ditch relief culverts (266 features) drained 17 km (10 mi) of the road network, 2 km (1 mi) of which was c onnected (13%). The broad based dips drained 70 km ( 44 mi) of the road network, 1 km ( 0.8 mi) of which was connected to
the stream network (2%)

.

Table 3

. Summary of effective road lengths by drain type for the Cold Creek area. Sump s cannot be stream connected, while streams crossings are stream connected by definition.

Drain Type All Drain Points Connected Drain Points Not Connected Drain

Points % Length

Connected
Count Mean Contributing Length (m) Σ

Contributing Length (m) Count Mean

Contributing Length (m) Σ

Contributing Length (m) Count Mean

Contributing Length (m) Σ

Contributing Length (m)

Broad Based Dip 1050 70 70,030 23 60 1320 1027 70 68,710 2%

Diffuse Drain 670 80 50,180 0 0 0 670 80 50,1 80 0%

Ditch Relief
Culvert 266 60 16,870 44 50 2240 222 70 14,630 13%

Lead Off Ditch 139 50 7110 9 40 360 130 50 6750 5%

Non

- Engineered

Drain 1097 40 41,270 10 40 360 1087 40 40,910 1%

Stream Crossing 115 40 4320 115 40 4320 0 0 0 100%

Sump 1 130 130 0 0 0 1 130 130 0%

Water Bar 246 30 7940 4 30 110 242 30 7830 1%

All Drains 3584 55 197,860 205 40 8720 3379 60 189,140 4%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

28 

### 4.2 Road Surface Fine Sediment Production and Delivery

Fine sediment production at a drain point ( ) is estimated with a base erosion rate and the properties of two flow paths along the road ( Luce and Black 1999, Cissel et al. 2012, Prasad 2007 ), as shown below.

is the base erosion rate 1 (kg/m)
is the road length (m) contributi ng to the drain point is the slope of the road contributing to the drain point (m/m)
is the vegetation cover factor for the flow path
is the road surfacing factor

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 either delivering or not delivering. No estimate of fractional delivery is made, because there is insignificant hillslope sediment storage in
locations where there is a clea r connection to the channel under most circumstances.

Delivery of fine sediment occurs through a mix of road drainage features, including broad based dips, diffuse road segments, ditch relief culverts, non

- engineered drains, water bars, and others ( Append ix A ).

In the t able s below , sediment delivery is broken out by drain type to assess their effectiveness in preventing sediment from entering the channel.



### Center Horse Morrell

- Trail Project Area

There were 5061 drain points observed in the Center Horse and Morrell/Trail Project Area , 314 of which
delivered sediment to stream channels ( Table 4 ) . Model predictions indicate that these points delivered
an estimated 21.4 Mg/yr, or 4% of the 456 Mg/yr generated on the road surfaces and ditches ( Figure

11 ). Broad based dips and non

- engineered drains delivered the most sediment ( 6.8 Mg/yr and 7.4 Mg/yr, respectively; Figure 12 ). There was 16.2 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 76 % of all sediment delivery and 57 % of all sedim ent produced within 10 m of a stream crossing (compared to the 4% delivery rate for all sediment). A map of the road surface sediment delivery and the accumulated sediment delivered through each drain point is shown for upper Little Shanley Creek and upper Black Canyon Creek in the Center Horse project area ( Figure 13 ).

The fraction of sediment produced and delivered from the road system can also be evaluated in the context of road length. Of the 407 km (252 mi) of total inventoried road length, 16.4 km (1 0.2 mi, 4%) deliver sediment to streams ( Table 4 ).

1 For this ana lysis, base erosion rates of 17 kg/meter of road elevation for open road s and 1 kg/meter of road

elevation for closed roads was used , based on observations at eight local sediment plots over two years ( Black and

Luce 2013 ). These numbers may be revised once more data can be collected. Sugden and Woods (2007) measured

erosion o n open roads in western Montana and found low to moderate rates that equate to GRAIP base rates of 7 kg/meter of road elevation for Belt geology and 11 kg/meter of road elevation for glacial till.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

29 Table 4

. Summary of sediment production and delivery at drain points in the Center Horse and Morrell/Trail Project

Area

.

Drain Type Count Σ
Sediment
Production (kg/yr) Σ

Sediment Delivery (kg/yr) %

Sediment Delivery Length

Connected (m) % Length
Connected

Broad Based Dip 1413 163,010 6860 4% 4490 3%

Diffuse Drain 931 104,870 1010 1% 700 1%

Ditch Relief Culvert 392 13,400 830 6% 1020 4%

E xcavated Stream Crossing 4 110 110 100% 180 100%

Lead Off Ditch 135 7800 810 10% 580 6%

Non

- Engineered Drain 1102 97,430 7410 8% 2300 3%
Stream Crossing 146 3140 3140 100% 5670 100%
Sump 24 1520 0 0% 0 0%

Water Bar 914 64,920 1190 2% 1470 3%
Discharg e at Stream Crossings* 241 28,280 16,170 57% 10,150 60%

All Drains 5061 456,200 21,360 5% 16,420 4%

* includes stream crossings, excavated stream crossings, and any other drain point within 10 m of stream crossings

Figure 11

. Percent total sediment delivered to streams by percent of drain points. 4% of all drain points deliver
100% of the delivered sediment. Figure 12

. Sediment production and delivery by drain point type.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

30 Figure 13

. Fine sediment delivery to channels by road segment and drain poi nt in the upper Little Shanley and Black Canyon Creeks area. The road lines are colored to indicate the mass of fine sediment delivered to channels.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

31 

### Poorman Creek

Th ere were 2190 drain points observed in the Poorman Creek area

, 97 of which delivered sediment to
stream channels ( Table 5 ) . Model predictions indicate that these points delivered an estimated 11.5 Mg/yr, or 5 % of the 247 Mg/yr generated on the road surface s and ditches ( Figure 1 4 ). N on

- engineered
drains and stream crossings delivered the most sediment ( 4 .4 Mg/yr and 4 .0 Mg/yr, respectively; Figure

15 ). A map of the road surface sediment delivery and the accumulated sediment delivered through each drain poin t is shown for the central part of the Poorman Creek area ( Figure 16 ).

There was 5.6 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 49 % of all sediment delivery and 77 % of all sediment produced within 10 m of a st ream crossing (c om pared to the

5 % delivery rate for all sediment).

T he fraction of sediment produced and delivered from the road system can also be evaluated in the context of road length. Of the 1 7 4 km ( 108 mi) of total inventoried road length, 8.1 km (5.0 mi, 5 %)
deliv er sediment to streams ( Table 2 ). Table 5 . Summary of sediment production and delivery at drain points in the Poorman Creek area.

Drain Type Count Σ
Sediment
Production (kg/yr) Σ

Sediment
Delive ry (kg/yr) %

Sediment Delivery Length

Connected (m) % Length
Connected

Broad Based Dip 412 70,320 2280 3% 930 2%

Diffuse Drain 417 47,010 160 0.3% 100 0.2%

Ditch Relief Culvert 56 7960 670 8% 1550 18%

Lead Off Ditch 8 710 0 0% 0 0%

Non

- Engineered Dra in 693 77,330 4420 6% 1600 4%
Stream Crossing 53 3960 3960 100% 3900 100%
Sump 2 80 0 0% 0 0%

Water bar 549 40,060 20 0.04% 30 0.1%

Discharge at Stream Crossings* 75 7260 5600 77% 4580 87%

All Drains 2190 247,420 11,500 5% 8110 5%

* includes stream c rossings and any other drain point within 10 m of stream crossingsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

32 Figure 14

. Percent total sediment delivered to streams by percent of drain points . 3% of all drain points deliver 100% of
the delivered sediment. Figure 15

. Sediment production and delivery by drain point type.

Figure 16

. Fine sediment delivery to channels by road segment and drain po int in central roaded portion of the Cold Creek area.
The road lines are colored to indicate the mass of fine sediment delivered to channels.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

33 

### Cold Creek

There were 3584 drain points observed in the Cold Creek area

, 205 of which delivered sediment to
stream channels ( Table 6 ) . Model predictions indicate that these points delivered an estimated 9.8 Mg/ yr, or 4 % of the 162 Mg/yr generated on the road surfaces and ditches ( Figure 17 ). Broad based dips and stream crossings delivered the most ( 3.3 Mg/yr and 3.8 Mg/yr, respectively; Figure 18 ). A map of the road surface sediment delivery and the accumulated sediment delivered through each drain point is
shown for the central part of the Cold Creek area ( Figure 19 ).

Table 6

. Summary of sediment production and delivery at drain points in the Cold Creek area.

Drain Type Count Σ
Sediment
Production (kg/yr) Σ

Sediment Delivery (kg/yr) %

Sediment Delivery Length

Connected (m) % Length
Connected

Broad Based Dip 1050 64,750 3350 5% 1320 2%

Diffuse Drain 670 30,070 0 0% 0 0%

Ditch Relief Culvert 266 12,750 1780 14% 2240 13%

Lead Off Ditch 1 39 5000 200 4% 360 5%

Non

- Engineered Drain 1097 377,340 300 1% 360 1%
Stream Crossing 115 3840 3840 100% 4320 100%
Sump 1 110 0 0% 0 0%

Water Bar 246 7590 350 5% 110 1%
Discharge at Stream Crossings* 180 8760 6570 75% 5210 75%

All Drains 3584 161,840 9810 6% 8720 4%

* includes stream crossings and any other drain point within 10 m of stream crossings

Figure 17

. Percent total sediment delivered to strea ms by percent of drain points. 6 % of all drain points deliver
100% of the delivered sediment. Figure 18

. Sediment production and delivery by drain point
type.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

34 There was 6.6 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 6 7 % of all sediment delivery and 75 % of all sediment produ ced within 10 m of a st ream crossing (compared to the

4 % delivery rate for all sediment).

T he fraction of sediment produced and delivered from the road system can also be evaluated in the context of road length. Of the 198 km ( 123 mi) of total inventori ed road length, 8.7 km (5.4 mi, 4 %) deliver sediment to streams ( Table 3 ). Figure 19

. Fine sediment delivery to channels by road segment and drain point in the central roaded portion of the
Cold Creek area. The road lines are colored to indicate the mass of fine sediment delivered to channels.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

35 

### 4.3 Downstream Sediment Accumulation

Road surface derived fine sediment enters the stream network below connected drain points. Road

related sediment accumulates in streams and is routed through the network. GRAIP calculates two
measures of road sediment for each stream segment. The first measure, sediment accumulation ( Figure s 20, 23, and 26 , below ), is the mass of road

- related sediment that passes through each stream segment

per y ear. In the absence of detailed information on sediment routing, the assumption is that road
surface

- related fine sediment has a residence time of less than one year. The second measure, specific sediment accumulation ( Figures 21, 24, a n d 26 , below ), is th e mass of road

- related sediment normalized by the contributing area. In this metric, area is used as a proxy for discharge, allowing us to compare the sediment impacts to channel segments with differing contributing areas.

Observed annual sediment yields for nearby areas ( Table 7 ) range from 2.8 Mg/km 2 /yr to 122.6 Mg/km 2 /yr. Time

- scales and data types varied. Not including the outlying data from Gibson Reservoir, the measured average sediment yield for nearby areas was 9.2 Mg/km 2 /yr, similar to short

- term rates for the northern Rocky Mountains as reported by Kirchner (2001).



### Center Horse Morrell

- Trail Project Area

Road surface

- related sediment at the mouth of the various creeks within the Center Horse and Morrell

Trail project area ranged from 0.0 3 Mg/yr ( Lost Creek) to 11.6 Mg/yr (Cottonwood Creek; Figure 20 ; Table 8 ). Specific sediment ranged from 0.01 Mg/km 2 /yr (North Fork Cottonwood Creek ) to 1.80 Mg/km 2 /yr (Little Shanley Creek). Using the total road surface sediment delivered and the drainage area for the whole Center Horse and Morrell/Trail project a re a, the specific sediment was 0.10 Mg/km 2 /yr ( Figure 21 )

.

Including the sediment from road

- related landslides (not including cutslope failures), gullies, and fill erosion at drain points (see Sections 4.4, 4.5, and 4.7 ), in addition to that from the road surface, the
total annual road sediment accumulation at the mouth of the various creeks within the Center Horse Table 7

. Observed annual sediment yields for nearby areas. Sampling methods and time scales vary.

Location Citation Length of

Record Type of Data Specific Sedim ent (Mg/km 2 /yr)

North Fork Blackfoot River, MT Lolo National Forest

2009 18 years Suspended sediment 2.8

Blackfoot River at Bonner, MT USGS 2012; Lambing

and Sando 2008 15 of 22

years Suspended sediment 7.5

Nevada Creek Reservoir, MT USDA 1978 36 years Reservoir core samples 7.7
Lower Willow Creek Reservoir, MT USDA 1978 11 years Reservoir core samples 11.9
Flathead Lake, MT Hoffman et al. 2006 7600 years Seismic survey 16.3
Gibson Reservoir, MT USDA 1978 43 years Reservoir core samples 122.6

Average , no outlier 9.2Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

36 and Morrell

- Tra il project area ranged from 0.03 Mg/yr ( Lost Creek) to 20.5 Mg/yr (Cottonwood Creek). Specific sediment with mass wa sting sedime nt ranged from 0.01 Mg/km 2 /yr (North Fork Cottonwood Creek) to 1.80 Mg/km 2 /yr (Little Shanley Creek) with large increases in some other areas (Cottonwood, Shanley, Spring , and Blind Canyon Creeks ). Using the total sediment including mass wasting delivered and the drainage area for the whole Center Horse and Morrell/Trail project ar ea, the specific sediment

was 0.21 Mg/km 2 /yr ( Figure 22 )

.

At the stream reach scale, road sediment impacts may be more pronounced due to high local delivery rates from gullies, landslides, road fill or surface erosion, and due to limitatio ns on available transport energy. Reaches in lower Spring, Black Canyon, Shanley, and Little Shanley Creeks may be in this group ( Figure 22 ).

Road

- related sediment both with and without mass wasting range d from about 0. 1 % to about 20 % of
the estimated ave rage annual observed sediment yield for this geographic region. Using the total sediment delivered and the drainage area for the whole Center Horse and Morrell/Trail project area, the specific sediment was 1 % of the estimated average annual observed sedime nt yield with road

- surface sediment only, and 2% of the estimated average annual observed sediment yield including mass wasting
sediment. Table 8

. Project area streams and sediment accumulation and specific sediment accumulation at th e stream mouth, calculated using only road surface

- related sediment and all road sediment sources (landslides, gullies, and fill erosion at drain points).

Stream Name Road Surface
Sediment at
Mouth (Mg/yr) Specific Road

Surface Sediment at Mouth (Mg/km 2 /y r) All Road

Sediment at
Mouth (Mg/yr) All Specific Road

Sediment at
Mouth (Mg/km 2 /yr)

Shanley Creek 0.8 0.06 3.0 0.21

Lost Creek 0.03 0.03 0.03 0.03 Dry Cottonwood Creek 0.3 0.05 0.3 0.05 Black Canyon Creek 2.4 0.43 2.4 0.43

Cottonwood Creek 11.6 0.19 20.5 0.33 Spring Creek 2.2 0.17 11.0 0.88 Little Shanley Creek 7.3 1.80 7.3 1.80

North Fork Cottonwood
Creek 0.3 0.01 0.3 0.01

Morrell Creek 3.6 0.05 3.9 0.06

Trail Creek 1.6 0.03 4.1 0.08 Swamp Creek 0.3 0.03 0.4 0.04
Blind Canyon Creek 0.9 0.04 3 .3 0.14

Center Horse and Morrell/Trail Project

Area 21.4 0.10 45.2 0.21Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

37 Figure 20

. Sediment accumulation from all road

- related sediment sources (road surface, gull ies, landslides, and fill erosion) in the Center Horse and Morrell/Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

38 Figure 21

. Specific sediment from road surface sediment in the Center Horse and Morrell/Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

39 Figure 22

. Specific sediment from all road

- related sediment sources (road surface, gullies, landslides, and fill erosion) in the Center Horse and Morrell/Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

40 

### Poorman Creek

Road surface

- related sediment at the mouth of the two named creeks within the Poorm an Creek area ranged from 0.1 Mg/yr (Canyon Creek) to 0.8 Mg/yr (South Fork Poorman Creek; Figure 23 ; Table 9 ). Specific sediment ranged from 0.0 4 Mg/km 2 /yr ( Canyon Creek ) to 0.05 Mg/km2/yr ( South Fork Poorman
Creek ). Using the total road surface sediment delivered and the drainage area for the whole Poorman
Creek area, the specific sediment was 0. 11 Mg/km 2 /yr ( Figure 24 )

.

Including the sediment from road

- related landslides (no t including cutslope failures), gullies, and fill erosion at drain points (see Sections 4.4, 4.5, and 4.7 ), in addition to that from the road surface, the
total annual road sediment accumulation at the mouth of Poorman Creek was 19.6 Mg/yr. Specific

sedime nt with mass wasting sediment for the en tire Poorman Creek area was 0.19 Mg/km 2 /yr ( Figure

25 )

.

At the stream reach scale, road sediment impacts may be more pronounced due to high local delivery rates from gullies, landslides, road fill or surface erosion , and due to limitations on available transport energy. Reaches in upper Poorman Creek may be in this group ( Figure 25 ).

Road

- related sediment both wit h and without mass wasting ranges from about 0. 4 % to about 0.5 % of the estimated average annual observed sediment yield for this geographic region. Using the total sediment delivered and the drainage area for the whole Poorman Creek area, the specific sediment is

1 % of the estimated average annual observed sediment yield with road

- surface sediment only, and 2 % of the estimated average annual observed sediment yield including mass wasting sediment. Table 9

. Project area streams and sediment accumulation and specific sediment accumulation at the stream mouth, calculated using only road surface

- related sediment and all road sediment sources (landslides, gullies, and fill erosion at drain points).

Stream Name Road
Surface
Sediment
at Mouth (Mg/yr) Specific Road

Surface
Sediment at
Mouth (Mg/km 2 /yr) All Road

Se diment
at Mouth (Mg/yr) All Specific

Road
Sediment at
Mouth (Mg/km 2 /yr)

South Fork Poorman Creek 0.8 0.05 1.1 0.03
Canyon Creek 0.1 0.04 0.1 0.04
Poorman Creek (Project Area) 11.5 0.11 19.6 0.19Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

41 Figure 23

. Sediment accumulation from all road

- related sediment s ources (road surface, gullies, landslides, and fill erosion) in
the Poorman Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

42Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

43 Figure 25

. Specific sediment from all road

- related sediment sources (road surface, gullies, landslides, and fill erosion) in the
Poorman Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

44 

### Cold Creek

Road surface

- related sediment at the mouth of the two forks of Cold Creek ranged from 0.4 Mg/yr ( No rth Fork Cold Creek ) to 3.8 Mg/yr (South Fork Cold Creek ; Figure 26 ; Table 10 ). Specific sediment ranged from 0.04 Mg/km2/yr ( North Fork Cold Creek ) to 0.14 Mg/km2/yr ( South Fork Cold Creek). Using the total road surface sediment delivered and the drainage area for the whole Cold Creek area, the specific sediment was 0.10 Mg/km2/yr ( Figure 27 )

. There were no instances of delivering gullies or landslides, and only two instances of delivering fill erosion, totaling roughly 0.02 Mg/yr, so mass wasting

was not routed downstream in Cold Creek.

Table 10

. Project area streams and sediment accumulation and specific sediment accumulation at the stream mouth, calculated using onl y road surface

- related sediment. There was no mass wasting that w as observed to deliver sediment to the stream in Cold Creek.

Name Road Surface
Sediment at
Mouth (Mg/yr) Specific Road

Surface Sediment at Mouth (Mg/km2/yr) Additional
Sediment from Mass Wasting at Mouth (Mg/yr)

South Fork Cold Creek 3.8 0.14 0

North Fo rk Cold Creek 0.4 0.04 0
Cold Creek (Main Stem) 8.7 0.09 0
Cold Creek Project

Area 9.8 0.10 0

At the stream reach scale, road sediment impacts may be more pronounced due to high local delivery

rates

, road surface erosion, and due to limitations on avai lable transport energy. Reaches in the South
Fork Cold Creek may be in this group ( Figure 27 ).

Road

- related sediment ranged from about 0. 4 % to about 1.5 % of the estimated average annual observed sediment yield for this geographic region. Using the total s ediment delivered and the drainage
area for the whole Cold Creek area, the specific sediment was 1% of the estimated average annual observed sediment yield.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

45 Figure 26

. Sediment accumulation from the road surface in the Cold Creek area. There were no instances of mass was ting that were
observed to deliver sediment to streams in Cold Creek.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

46 Figure 27

. Specific sediment from road surface sediment in the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

47 

### 4.4 Landslides

At each landslide location , the type, locatio n, and volume are observed. Landslides can be determined to be connected to the channel network if an associated drain point above the landslide is connected to the channel network, if an associated road surface flow path that would be expected to intercep t the landslide sediment is connected to the network, or if the landslide is observed in the field to be
connected to the network. In most cases, shallow landslides initiate during large storm events when soils become saturated, and deliver sediment to the channel over a limited time frame. This represents a pulsed as opposed to chronic sediment input to the streams. Delivered landslide masses are distributed over a 20 year time span in order to compare their approximate magnitude with that of the road surf ace fine sediment (a chronic sediment source). Twenty years is used because, in most places, that is roughly the maximum age of a feature still easily observable in the field. In any given year, the amount of
sediment delivered to streams from landslides i s likely to be higher or lower than the rate we calculate.

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

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

and locally calibrated to known locations of landslides (where available) . SINMAP has its basis in the infinite plane slope stability model and produces raster grids that illustrate slope stability based on hillslope and specific catchment area at each DEM gr id cell. Un

- roaded and roaded risk grids are subjected to a series of mathematical operations that result in grids that show the important changes to landslide risk due to the presence of the roads. These change grids are compared to the natural
landslide risk grid to show how the roads affect slope stability in the context of the background risks (i.e. the risks without the influence of road drainage). Important grid cell changes are those un

- roaded to roaded differences that show a risk change from stable to unstable, or the areas that were unstable
without roads and became less stable after road construction.



### Center Horse Morrell

- Trail Project Area

Existing Landslides

The Center Horse and Morrell/Trail project area has a low incidence of road

- related sha llow landsliding. Most road miles are located on the shallow slopes of the glaciated valley bottoms. Landslide volume was estimated for all landslides visible from the road greater than a minimum threshold of six feet in slope length and slope width. The i nventory recorded 18 landslides ( Table 11 ), totaling 1319 m 3 (1726 yd 3 ). There were nine landslides estimated to be less than five years of age, three between five and ten years old, and six landslides were between ten and 15 years old. There were ten that were related to the road in some way; road

- related landslides totaled 307 m 3 (402 yd 3 ). Including non

- road related landslides, there were nine cutslope failures (257 m 3 , 336 yd 3 ), four hillslope failures (614 m 3 , 803 yd 3 ), and five fillslope failures (449 m 3 , 587 yd 3 ). Figure 28 shows the locations of the observed landslides in the Spring Creek area of the Center Horse and Morrell/Trail project area.

There were two landslides (11%) found to be stream connected; one road related fillslope failure and

one n on

- road related cutslope failure. The cutslope failure may not be fully connected due to the common removal of eroded cutslope material during road maintenance and uncertainty surrounding timing and discharge of intercepting flow paths. The stream in which the fillslope failure discharged may
lead to a lake.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

48 Using a bulk density for road fill of 1.6 Mg/m 3 ( Madej 2001 ), the total mass of sediment generated was expected to be 2111 Mg, wi th 176 Mg delivering to streams, not including the cutslope failure. T his is
about 10% of all landslide

- generated mass ( Table 11 ). Over a 20

- year period, about 8.8 Mg/yr (again without the cutslope failure) have been delivered to streams. This is roughly half the rate of the annual road surface fine sediment delivery. It wou ld take about eight years for the fine sediment delivery from road surfaces to equal the total mass of delivered sediment from landslides. Estimates here do not account for partial delivery of landslide sediments (i.e. not all sediment from a road related landslide is likely to be delivered, even if some of the sediment is), so actual volumes may be lower.

Table 11

. Number and types of observed landslides, as well as masses and volumes of sediment generated

and delivered to the stre am channel network in the Center Horse and Morrell/Trail project area.

Location Count Volume (yd 3 ) Volume

(m 3 ) Mass

Produced (Mg) Mass

Delivered (Mg) Average Delivery

Rate Over 20 Years (Mg/yr) Road Related

Cutslope 9 336 257 411 109 5.4

Not Road Related 3 156 119 190 109 5.4

Road Related 6 180 138 221 0 0
Fillslope 5 587 449 718 176 8.8

Not Road Related 3 421 322 515 0 0

Road Related 2 166 127 203 176 8.8 Hillslope 4 803 614 982 0 0

Not Road Related 2 747 571 914 0 0

Road Re lated 2 55 42 68 0 0

Totals, Not Considering Cutslope Failures 1700 176 8.8

Totals 18 1726 1319 2111 284 14.2

Not Road Related 8 1324 1012 1620 109 5.4

Road Related 10 402 307 491 176 8.8

Figure 28

. Observed landslides in the Spring
Creek are a of the
Center Horse and Morrell/Trail project

area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

49 Changes to Landslide Risk Due to Roads

SIMNAP c alibrati on was completed using eight known locations of landslides in the local area obtained from forest personnel ( S. Hendrickson, personal communication 2013 ). Figures 29 and 30 illustrate the risk and change in risk in the area. SINMAP was calibrated and run i nitially to determine the intrinsic stability of the slopes over which the road traverses and to identify locations that are at a high risk of failure without the road ( Figure 29 ).

A second calibrated stability index run was performed to address the eff ects of road water contribution to drain points. In Figure 30 , the areas in the Spring Creek drainage in the southern part of the project area where the road changed the risk from the stable category (stable, moderately stable, quasi

- stable
from Figure 2 9

, above) to the unstable category (lower threshold, upper threshold, defended) are shown in red. These are areas where road drainage was installed over naturally stable slopes, and the added water moved the area into the unstable category. The orange cells are areas where the risk increased (became less stable) after road construction, and the terrain was unstable prior to road construction. This is due to the installation of road drainage over naturally unstable slopes. Risk may not extend as far downslope as is shown. Figure 29

. Natural slope stability in the Spring Creek drainage of the Center Horse and Morrell/Trail project area. The yellow, blue, and green cells are generally considered t o be stable, while the pink, red, and dark tan cells are generally considered to be unstable. The star indicates a stream

- connected landslide in a creek that discharges into a lake.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

50 Figure 30 also shows the locations of observed landslides. Over the whole area, nine of the 18 landslides (50%) occurred on destabilized slopes. As shown and described above, some of these points are fillslope or cutslope failures, and may n ot correlate well with the SINMAP risk which is designed to predict hillslope risks rather than risks within the road prism. Additionally, there were only eight calibration landslide points; a good calibration dataset should include at least 50 points. Gi ven these considerations, there is a reasonably high level of correlation between observed and expected landslide locations.

Of the 216 km 2 ( 83 mi 2 ) that comprise the Center Horse and Morrell/Trail project area, 2.6 km 2 (1 mi 2

, 1%) was stable before road construction and is now unstable, and 3.7 km 2 (1.4 mi 2 , 2 %) was unstable before road construction and is now less stable due to road drainage ( Table 12 ). This is a total of 6.3 km 2
(2.4 mi 2

, 3 %) of the watershed that has experienced an increase in landslide risk due to road hydrology. This can be compared to 7.8% of the North Fork Siuslaw River watershed in western Oregon that experienced an increase in landslide ri sk due to roads, and has a high incidence of road related shallow landsliding.

Table 12

. Landslide risk changes in the Center Horse and Morrell/Trail project area

by category and area.

Total Area of Watershed (m 2 ) 215,620,000 100% Area Stable Before Roads, Now Unstable (m 2 ) 2,646,600 1% Area Unstable Before Roads, Now Less Stable (m 2 ) 3,686,400 2%
Total Area Affected by Roads (m 2 ) 6,336,000 3% Figure 30

. Changes in slope stability risk in th e Spring Creek drainage of the Center Horse and Morrell/Trail project area. The red and orange areas are where the risk increased.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

51 

### Poorman Creek

Existing Landslides

The Poorman Creek area has a low incidence of road

- related shallow landsliding. Hillslopes in Poorman Creek are generally shallow . Landsl ide volume was estimated for all landslides visible from the road greater than a minimum threshold of six feet in slope length and slope width. The inventory recorded
five landslides ( Table 1 3 ), totaling 252 m 3 ( 329 yd 3 ). Three landslides were estimated to be less than five years of age, and two landslides were between ten and 15 years old. All five were related to the road in

some way

. T here were three cutslope failures ( 95 m 3

, 124 yd 3 ), one hillslope failure ( 153 m 3

, 200 yd 3 ),
and one fillslope failure ( 4 m 3

, 5 yd 3 ). Figure 31 shows the locations of the observed landslides in the
Poorman Creek area.

Table 13

. Number and types of observed landslides, as well as masses and volumes of sediment generated and delivered to the stream cha nnel network in the Poorman Creek

area.

Location* Count Volume

(yd 3 ) Volume

(m 3 ) Mass
Produced (Mg) Mass
Delivered (Mg) Average

Delivery Rate

Over 20 Years (Mg/yr)

Cutslope 3 124 95 152 91 4.5
Fillslope 1 5 4 6 0 0
Hillslope 1 200 153 245 0 0

Total 5 329 252 403 91 4.5

* all observed landslides were road related

Figure 31

. Observed landslides in the Poorman Creek area. The dotted line was collected in 2014.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

52 There was one landslide that was found to be stream connected. This cutslope failure occurred directly above a culvert, and the culvert was connected to a stream. Though it is likely that s ome sediment from
this failure moved across the road and was not delivered, or was re moved by maintenance equipment, observations suggest that most of the sediment entered the culvert and therefore delivered to the

stream.

Using a bulk density for road fi ll of 1.6 Mg/m 3 ( Madej 2001 ), the total mass of sediment gene rated was expected to be 403 Mg , with 91 Mg delivering to streams. T his is about 20 % of all landslide

- generated mass ( Table 1 3 ). Over a 20

- year period, about 4.5 Mg/yr have been delivered to stre ams. This is roughly
half the annual road surface fine sediment delivery rate

. It would take about 8 years for the fine sediment delivery from road surfaces to equal the total mass of delivered sediment from landslides. Estimates here do not account for p artial delivery of landslide sediments (i.e. not all sediment from a road related landslide is likely to be delivered, even if some of the sediment is), so actual volumes may
be lower

.

Changes to Landslide Risk Due To Roads

SIMNAP c alibration was complete d using the same eight known locations of landslides in the Center Horse and Morrell/Trail project area obtained from forest personnel ( S. Hendrickson, personal

communication 2013 ). Figures 32 and 33 illustrate the risk and change in risk in the area. SINM AP was calibrated and run initially to determine the intrinsic stability of the slopes over which the road traverses and to identify locations that are at a high risk of failure without the road ( Figure 32 ).

F igure 32

. Natural slope stability in the central part of the Poorman Creek area. The yellow, blue, and green cells are generally considered to be stable, while the pink, red, and dark tan cells are generally
considered to be unstab le . The dotted line was collected in 2014.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

53 A second calibrated stability index run wa s performed to address the effects of road water contribution to drain points. In Figure 33 , the areas in the central portion of the Poorman Creek area where the road changed the risk from the stable category (stable, moderately stable, quasi

- stable from F igure 32

, above) to the unstable category (lower threshold, upper threshold, defended) are shown in red. These are areas where road drainage was installed over naturally stable slopes, and the added water moved the area into the unstable category. The oran ge cells are areas where the risk increased (became less stable) after road construction, and the terrain was unstable prior to road construction. This is due to the installation of road drainage over naturally unstable slopes. Risk may not extend as far d ownslope as
is shown.

Figure 33 also shows the locations of observed landslides. Over the whole area, the only landslide that occurred over a destabilized slope was the hillslope failure. F illslope and cutslope failures may not
correlate well with the SIN MAP risk which is designed to predict hillslope risks rather than risks within the road prism. Additionally, there were only eight calibration landslide points , and they were located in somewhat dissimilar geology in a relatively spatially distant locale ; a good calibration dataset should include at least 50 poin ts and be within a nearby area of similar soils and geology . Given these considerations, it is reasonable to expect poor correlation between observed and expected landslide
locations.

Of the 130 k m 2 ( 50 mi 2 ) that comprise the Poorman Creek area, 1.4 km 2 ( 0.5 mi 2 , 1%) was stable before
road construct ion and is now unstable, and 1.5 km 2 (0.6 mi 2 , 1 %) was unstable before road construction and is now less stable due to road drainage ( Table 12 ). This is a total of 2.9 km 2 (1.1 mi 2

, 2 %) of the watershed that has experienced an increase in landslide risk due to road hydrology. This can be Figure 33

. Changes in slope stability risk in the central part of the Poorman Creek area. The red and orange areas are where the risk increased. The dotted line was collected in 2014.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

54 compared to 7.8% of the North Fork Siuslaw River watershed in western Oregon that experienced an
increase in landslide risk due to roads, and has a high incidence of road related shallow landsliding.

Table 14

. Landslide risk changes in the Poorman Creek area by category and area.

Total Area of Watershed (m 2 ) 130,484,000 100%

Area Stable Before R oads, Now Unstable (m 2 ) 1,351,1 00 1% Area Unstable Before Roads, Now Less Stable (m 2 ) 1 ,519,560 1%
Total Area Affected by Roads (m 2 ) 2,870,670 2%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

55 

### Cold Creek

Existing Landslides

The Cold Creek area has a low incidence of road

- related shallow landslidi ng ( Figure 34 )

. Most road miles are located on the shallow slopes of the glaciated valley bottom. Landslide volume was estimated for all landslides visible from the road greater than a minimum threshold of six feet in slope length and slope
width. The inve ntory recorded nine landslides ( Table 1 5 ), totaling 175 m 3 ( 229 yd 3 ). Two landslides were estimated to be less than five years of age, one landslide was estimated to be between five and ten years old, and six landslides were between ten and 15 years old or older

. There were eight that were related to the road in some way; road

- related landslides totaled 141 m 3 ( 184 yd 3 ). Including the non

road related landslide , there were five cutslope failures ( 80 m 3

, 105 yd 3

, and four fillslope failures ( 94

m 3

, 123 yd 3 ).

Figure 34 shows the locations of each of the observed landslides in the Cold Creek area. No landslides
were found to be connected to the stream network. Using a bulk density for road fill of 1.6 Mg/m 3
( Madej 2001 ), the total mass of sediment gene rated was expected to be 280 Mg ( Table 1 5 ).

Fi gure 34

. Observed landslides in the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

56 Changes to Landslide Risk Due To Roads

SIMNAP c alibration was completed using the same eight known locations of landslides in the Center Horse and Morrell/Trail proje ct area obtained from forest personnel ( S. Hendrickson, personal

communication 2013 ). Figures 35 and 36 illustrate the risk and change in risk in the area. SINMAP was

Table 15

. Number and types of observed landslides, as well as masses and volumes of sediment generated in the Cold Creek area.

Location Count Volume (yd3) Volume

(m3) Mass
Produced (Mg) Ma ss

Delivered (Mg) Road Related

Cutslope 5 105 80 129 0

Road Related 5 105 80 129 0 Fillslope 4 123 94 151 0

Not Road Related 1 44 34 54 0

Road Related 3 79 60 97 0

Totals, Not Considering Cutslope Failures 151 0

Totals 9 229 175 280 0

Not Road Related 1 44 34 54 0

Road Related 8 184 141 225 0

Figure 35

. Natural slope stability in the Cold Creek area. The yellow, blue, and green cells are generally considered to be stable, while the pink, red, and dark tan cells are generally considered to be unstable.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

57 calibrated and run initially to determine the intrinsic stability of the slopes over whic h the road traverses and to identify locations that are at a high risk of failure without the road ( Figure 35 ).

A second calibrated stability index run was performed to address the effects of road water contribution to drain points. In Figure 36 , the are as in the Cold Creek area where the road changed the risk from the stable category (stable, moderately stable, quasi

- stable from Figure 35 , above) to the unstable category (lower threshold, upper threshold, defended) are shown in red. These are areas where road drainage was installed over naturally stable slopes, and the added water moved the area into the unstable category. The orange cells are areas where the risk increased (became less stable) after road construction, and the terrain was unstable prior t o road construction. This is due to the installation of road drainage over naturally unstable slopes. Risk may not extend as far downslope as is shown. The areas of elevated risk may be limited to the upper part of the road network, where valley walls are steeper. Most of the road network in the Cold Creek area is in the lower part of the watershed, where hillslopes are generally very shallow.

Figure 36 also shows the locations of observed landslides. Over the whole area, the only landslide that
occurred ov er a destabilized slope was a cutslope failure. There were no observed hillslope failures, and
f illslope and cutslope failures may not correlate well with the SINMAP risk which is designed to predict hillslope risks rather than risks within the road pri sm. Additionally, there were only eight calibration Figure 36

. Changes in slope stability risk in the central part of the Cold Creek area. The red and orange
areas are where the risk increased.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

58 landslide points , and they were located in a relatively spatially distant locale ; a good calibration dataset should include at least 50 poin ts and be nearby to the area of interest . Given these considera tions, it is reasonable to expect poor correlation between observed and expected landslide locations.

Of the 101 km 2 ( 39 mi 2 ) that comprise the Cold Creek area, 0.3 km 2 ( 0. 1 mi 2

, 0.3 %) was stable before
road construct ion and is now unstable, and 0.3 km 2 ( 0.1 mi 2 , 0.3 %) was unstable before road construction and is now less stable due to road drainage ( Table 16 ). This is a total of 0.6 km 2 ( 0.3 mi 2

, 0.6 %) of the watershed that has experienced an increase in landslide risk due to road hydrology. This
can be c ompared to 7.8% of the North Fork Siuslaw River watershed in western Oregon that experienced an increase in landslide risk due to roads, and has a high incidence of road related shallow landsliding.

Table 16

. Landslide risk changes in the Cold Creek area by category and area.

Total Area of Watershed (m 2 ) 100,642,000 100% Area Stable Before Roads, Now Unstable (m 2 ) 308,900 0.3% Area Unstable Before Roads, Now Less Stable (m 2 ) 338,000 0.3%
Total Area Affected by Roads (m 2 ) 646,90 0 0.6%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

59 

### 4.5 Gullies and Gully Initiation Risk

Gullying at drain points below roads can be a substantial source of sediment to stream channels. At each gully location we measured or estimated the volume of the gully, and observed properties such as its location, any other contributing factors such as groundwater interception, and whether or not it was associated in any way with the road. To distinguish between road

- related gullies and natural incipient channel heads, we mapped features as a gully if the y occurred below the road drain points, but were absent on the uphill side of the road. A gully was defined as a linear erosional feature at least ten feet long and six inches deep. Gullies can be determined to be connected to the stream channel network if an associated drain point that discharges through the gully is connected to the channel. This mass is both pulsed (as the gully initiates) and chronic (as continued erosion by road surface

- derived water), but it is not known what proportion belongs to eac h category. Delivered gully masses are distributed over a 20 year time span in order to compare their magnitude with that of the road surface fine sediment (a chronic sediment source). Twenty years is used because, in most places, that is roughly the maxim um

age of a feature still easily observable in the field. In any given year, the amount of sediment delivered
to streams from gullies is likely to be higher or lower than the rate we calculate.

Gully initiation occurs when the shear stress applied by runo ff 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 drain point.

is the contributing road length at the drain point (m)
is the slope of the hillslope below the drain point (%)

Calculated ESI values are compared to a calibrated critical ESI threshold (ESI crit ) to identify areas with a high risk of gully formation (i.e., where ESI > ESI crit ). Calibrations are completed using a logistical regression technique (local fit, locfit) in the R statistical computing environment and a length

- slope plot of the drain points with and without gullies ( Figure 38

, below ). An easy way to conceptualize this is to think of these distributions as densities. That is, while the density of non

- gully drain points decreases as ESI gets larger, the density of gullied points increases relative to the non

- gullied drain points. For more information on ESI in GRAIP, see Cissel et al. (2012) , specifically, pages 105

- 109 and page 126.

Diffuse drain points, stream crossings, and drain points that do not have an associated road surface flow path (i.e. orphan drain points, Appendix A ) are not included in the ESI analysis, because these types of drain points do not behave in such a way that the ESI is a useful metric. Diffuse points represent a road segment that does not concentrate flow, and so does not pose a gully risk. Streams have their own, and
often non

- road related, controls on their propensity to incise, and so cannot be treated the same as other drain points. Orphan drain points have a contributing length of zero, and so have an ESI of zero, which throws off a meaningful averag e.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

60 

### Center Horse Morrell

- Trail Project Area

Existing Gullies

The Center Horse and Morrell/Trail project area has a medium to low incidence of road related gullies. There were 33 gullies observed during the course of the survey, with a total volume of 20 8 m 3 (272 yd 3

, Table 1 7 ). There were 13 gullies that occurred only on the hillslope (44 m 3 , 58 yd 3 ), four that occurred only on the fillslope (2 m 3 , 3 yd 3 ), and ten that occurred on both the fillslope and hillslope below a drain point (131 m 3 , 172 yd 3 ). Al l 33 gullies occurred in wet swales. Three gullies were no longer actively eroding, while 30 were actively eroding. Figure 37 shows the locations of the gullies in the western portion of the Center Horse area, as well as gully initiation risk information ( see below).

There were ten gullies (30%) that were determined to be connected to the channel. Using a bulk density for road fill of 1.6 Mg/m 3 ( Madej 2001 ), the mass of sediment generated at all connected gullies was 217 Mg ( Table 1 8 ). This was 65% of the mass generated at all gullies. Over a 20 year period, 11 Mg/yr of sediment was delivered to stream channels, or roughly half of the rate of road surface fine sediment delivered to stream channels annually. It would take about ten years for the fine sedime nt delivery from Figure 37

. Locations of observed gullies and ESI risk at drain points, western portion of the

Center Horse area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

61 road surfaces to equal the total mass of delivered sediment from gullies. Actual annual sediment delivery from gullies is likely higher or lower than these estimates in any given year.

Gully Initiation Risk

The ESI crit was empirically derived for the Center Horse and Morrell/Trail project area using inventoried gullies, and is the ESI value above which the risk of gully formation increases significantly ( Figure 38 )

. Here, ESI crit = 14, as the risk of gully formation roughly doubles above that value ( Table 1 9 ). There was one orphan drain point with a gully, and seven gullies without an associated drain point. Table 17

. Inventoried gullie s in the Center Horse and Morrell/Trail project area.

Location of Gully Count Volume (yd 3 ) Volume

(m 3 ) Number That Occur

in Wet Swale Average Delivery Rate

Over 20 Years (Mg/yr) Activity of Gully

Above Road 6 39 30 6 0

Not Active 1 1.8 1.4 1 0

Still Eroding 5 38 29 5 0
Fillslope 4 2.7 2.1 4 9

Not Active 2 1.3 1.0 2 9

Still Eroding 2 1.4 1.1 2 0
Hillslope 13 58 44 13 0

Still Eroding 13 58 44 13 0

Fill and Hill 10 172 131 10 2

Still Eroding 10 172 131 10 2

Totals 33 272 208 33 11

Table 18

. Sediment masses produced and delivered by active gullies in the Center Horse and Morrell/Trail project area.

Mass Produced (Mg) Mass Delivered

(Mg) % Sediment

Delivery Average Delivery Rate Over 20

Years (Mg/yr)

Fillslope 3 0 0% 0
Hillslope 71 45 64% 2
Fillslope and Hillslope 210 172 82% 9

Totals 332 217 65% 11Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

62 The average ESI across the Center Horse and Morrell/Trail project area was 9, with an average contributing road length of 85 m (280 ft, Table 20 ). There were 587 (16%) non

- diffuse non

- stream crossing non

- orphan drain points w here ESI exceeded ESI crit , leaving 3126 drain points (84%) with an ESI value below the threshold. Of the drain points with gullies, six (26%) had an ESI value in excess of ESI crit . This leaves 17 gullied drain points (74%) with an ESI that fell under the critical threshold. The gully rate for all points above ESI crit was 1.0%, and it was 0.5% for points below ESIcrit ( Table 1 9 ). Drain points that had gullies drained 1.8 km (1.1 mi) of road length. The average ESI of drain points with gullies was 11,
while the average ESI of drain points without gullies was 9. The average contributing length at drain points with gullies was 77 m (250 ft), and similarly 85 m (280 ft) at drain points without gullies. Figure 37 shows the distribution of gully risk in the weste rn portion of the Center Horse area.

Table 19

. Distribution of drain points by ESI value, Center Horse and Morrell/Trail
project area. ESI crit = 14. Eight observed gullies did not have an associated drain point

or occurred below an orphan drain point, and so are not counted.

< ESIcrit > ESIcrit

ESI Value < 14 14

- 50 50

- 100 > 100

# Sites With Gullies 17 4 2 0

# Sites Without Gullies 3109 440 106 35

% of Total With Gullies 74% 17% 9% 0%

% of Total Without Gullies 84% 12% 3% 1% Gully Rate (# Gullied / # Total in %) 0.5% 1.0%

Table 20

. Further distribution information of drain points by ESI value.

Contributing Length (m) Average ESI Where ESI > ESIcrit Total

Number Total Average Total Per cent

Drain Points With Gullies 1770 77 11 6 26% 23

Drain Points Without Gullies 315,070 85 9 581 16% 3690

All Drain Points 316,840 85 9 587 16% 3713 Figure 38

. Length

- slope plot that shows the distribution of gullied and non

- gullied drain points. Notice that there a re more non

gullied points towards the center of the graph. As the ESI gets larger (upper right part of the distribution), there are fewer non

gullied points, but there are relatively more gullied points. Above the blue ESI crit = 14 line,
there is a 1.0% c hance of a point being gullied, while below the ESI crit line, there is a
0.5% chance.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

63 

### Poorman Creek

Existing Gullies

The Poorman Creek area has a low incidence of road related gullies. There were four gullies observed during the course of the survey, with a total vo lume of 151 m 3 ( 197 yd 3

, Table 21 ). There were two gullies that occurred only on the hillslope ( 150 m 3

, 196 yd 3 ), and two that occurred only on the fillslope ( 0.7 m 3

, 0.9 yd 3 ). No gullies occurred in wet swales. The gullies located on the hillslope were no longer actively eroding, while both gullies that occurred on the fillslope were actively eroding. Figure 3 9 shows the locations of the gullies in the central portion of the Poorman Creek area, as well as gully initiation

Table 21

. Inventoried gullies in the Poorma n Creek area.

Location of Gully

Count Volume (yd 3 ) Volume

(m 3 ) Number That

Occur in Wet
Swale Average Delivery

Rate Over 20 Years (Mg/yr) Activity of Gully

Fill and Hill 1 0.3 0.2 0 0.02

Still Eroding 1 0.3 0.2 0 0.02

Fillslope 4 9 7 0 0.2

Still Eroding 4 9 7 0 0.2

Hillslope 2 196 150 0 0

Not Active 2 196 150 0 0

Totals 7 206 157 0 0.2

Figure 39

. Locations of observed gullies and ESI risk at drain points, central portion of the Poorman Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

64 risk information (see below). No g ullies were determined to be connected to the channel. Using a bulk density for road fill of 1.6 Mg/m 3 ( Madej 2001 ), the mass of sediment generated at all gullies was 241 Mg.

There were two gullies (29 %) that were determined to be connected to the channel . Using a bulk density for road fill of 1.6 Mg/m 3 ( Madej 2001 ), the mass of sediment generated at all connected gullies was 4 Mg ( Table 22 ). This was 2 % of the mass generated at all gullies. Over a 20 year period, 0.2 Mg/yr of

sediment was delivered to str eam channels , which is insignificant compared to the rate of road surface fine sediment delivered to stream channels annually. It would take less than one year for the fine sediment delivery from road surfaces to equal the total mass of delivered sediment from gullies. Actual annual sediment delivery from gullies is likely higher or lower than these estimates in any given year.

Gully Initiation Risk

In the Poorman Creek area , t here were too few gullies to determine an ESI crit , suggesting that the gully initiation risks here may be very low. The average ESI across the Poorman Creek area was 8 , with an average contributing road length of 7 9 m (2 59 ft, Table 2 3 ). Drain points that had gullies drained 1.2 km ( 0 .8 mi) of road length. Figure 39 shows the distribution of gully risk in the central portion of the
Poorman Creek area.

Table 23

. Drain point and ESI statistics for the Poorman Creek area

Contributi ng Length (m) Average

ESI Total
Number Total Average

Drain Points With Gullies 1222 204 5 6

Drain Points Without Gullies 172864 79 8 2184

All Drain Points 174086 79 8 2190 Table 22

. Sediment masses produced and delivered by active gullies in the Poorman Creek area.

Mass
Produ ced (Mg) Mass

Delivered (Mg) % Sediment

Delivery Average Delivery

Rate Over 20 Years (Mg/yr)

Fillslope 11 4 31% 0.2
Hillslope 240 0 0% 0
Fillslope and Hillslope 0.3 0.3 100% 0.02

Totals 252 4 2% 0.2Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

65 

### Cold Creek

Existing Gullies

The Cold Creek area has a low incidence of road related gullies. There were three gullies observed during the course of the survey, with a total volume of 5 m 3 ( 7 yd 3

, Table 24 ). There were two gullies that occurred only on the hillslope ( 4 m 3

, 5 yd 3 ), and two that occurred only on the fillslope ( 2 m 3

, 2 yd 3 ).

No gullies occurred in wet swales. All gullies were actively eroding. Figure 40 shows the locations of the gullies in the Cold Creek area, as well as gully initiation risk information (see below). No gullies were determined to be connected to the channel. Using a bulk density for road fill of 1.6 Mg/m 3 ( Madej

2001 ), the mass of sediment generated at all gullies was 9 Mg.

Table 24

. Inventoried gullies in the Cold Creek area.

Location of Gully

Count Volume (yd3) Volume

(m3) Mass

Produced (Mg) % Sediment

Delivery Number That

Occur in Wet
Swale Activity of Gully

Fillslope 1 2 2 2 0% 0

Still Eroding 1 2 2 2 0% 0 Hillslope 2 5 4 6 0% 0

Still Eroding 2 5 4 6 0% 0

Totals 3 7 5 9 0% 0

Figure 40

. Locations of observed gullies and ESI risk at drain points, central portion of the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

66 Gully Initiation Risk

In the Cold Creek area , there were too few gullies to determine an ESI crit , suggesting that the gully initiation risks here may be very low. The average ESI across the Cold Creek area was 4 , with an average contributing road length of 55 m ( 180 ft, Table 2 5 ). Drain points that had gullies drained 0.2 km ( 0 .1 mi) of road length. Figure 40 shows the distribution of gully risk in the Cold Creek area.

Table 25

. Drain point and ESI statistics for the Cold Creek area.

Contributing Len gth (m) Average ESI Total
Number Total Average

Drain Points With Gullies 157 52 4.3 3

Drain Points Without Gullies 197,699 55 4.0 3581

All Drain Points 197,856 55 4 .0 3584Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

67 

### 4.6 Stream Crossing Failure Risk

Besides contributing fine sediment to st reams 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
ch aracterizes 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. The SBI is out of a range of one to four, where one suggests low risk of blockage, and four suggests a high risk of blockage.

The risk of 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. We calculated the fill material that would likely be excavated in an overtopping type failure. We modeled the prism of fill at risk as bounded at the base by an area 1.2 times the channel width, with side slopes climbing to the road surface at a slope of 33%.

Another consequence of concern at failed stream crossings is the diversion of stream flow onto road surfaces and unchanneled hillslopes. Once a crossing becomes occluded and begins to act as a dam,
failure can occur in one of 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 crossing in one or more directions, the flo w may be diverted down the road and ditch and onto adjacent hillslopes, where it can cause gullying and/or landsliding ( Furniss et al. 199 7

, Best et al. 1995 ). In these situations, volumes of sediment far exceeding those at the crossing can be at
risk. GRA IP 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.

The highest risk crossings in the se are as have high SBI and diversion pote ntial in one or both directions

. These are generally the crossings that should be addressed first.



### Center Horse Morrell

- Trail Project Area

Field crews recorded 150 stream crossings in the Center Horse and Morrell/Trail p roject area. Only the 116 crossings with a culvert were included in the SBI calculations. The 34 crossings that did not have a culvert were bridges (seven crossings), were natural fords (23), or were excavated crossings (four), and
were not included. Risk of pipe plugging is not a factor at these crossings.

Figure 41

. Distribution of SBI values for the Center Horse and Morrell/Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

68 The SBI values for the Center Horse and Morrell/Trail project area had an average of 1.9 for the 116 stream crossings. There were two stream crossings with an SBI of 4, 25 crossings with an SBI of 3, 53 crossings with an SBI of 2, and 36 crossings with an SBI of 1 ( Figure 41 ). Of the crossings with values of three and four, 24 of 27 had a pipe diameter to channel width ratio of 0.5 or less (small pipe, large stream), and 14 had a pipe that was 1/3 or l ess than the width of the stream, and seven pipes were partially or totally blocked. Six crossings with an SBI of 2 had a pipe that was half the width of the
channel.

The total fill volume at risk for all the stream crossings was 6844 m 3 (8951 yd 3 ). Fill volumes ranged from

5 m 3 (7 yd 3 ) to 875 m 3 (1144 yd 3 ), and had a mean volume of 60 m 3 (78 yd 3 ). This is similar to previous findings for the middle Blackfoot River at 38 stream crossings, which had an average of 116 tons of fill per crossing ( Montana Depa rtment of Environmental Quality 2008 ). Overtopping

- type fill failure will not occur at bridges, so no fill volume risk was calculated at these locations. In the Center Horse and Morrell/Trail project area, 55 of 146 stream crossings (38%) had the potential to divert streamflow down
the road in one or more directions. Bridges also had no diversion potential.

There were 14 crossings with an SBI of 3 or 4 and diversion potential ( Figure 42 ). There was a total of

824 m 3 (1077 yd 3 ) of fill at risk at these poi nts. T wo have more than 100 m 3 of fill at risk , and four had some major issue (e.g. observed overtopping) or were at imminent risk of a major issue (e.g. partial blockage or sediment plume moving downstream to the pipe). These crossings should have the hi ghest priority for risk reduction treatments. The 13 crossings with a high SBI but no diversion had 1028 m 3 Figure 42

. T he stream crossings with the highest risk of plugging and the most severe consequences of failure in the Center Horse and Morrell/Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

69 (1345 yd 3 ) of fill at risk, and the 47 crossings with diversion but a low SBI had 1835 m 3 (2400 yd 3 ) of fill at
risk

.

Several stream crossings were observed to have overtopped or diverted flow in the course of the survey. Two crossings, along road 4353 (Morrell Creek) and road 602 (Shanley Creek), were plugged by sediment, but the water from both diversions infiltrated before connecting to a stream. These crossings had SBIs of 1 and 2. One crossing, along road 17506 (Blind Canyon Creek), was plugged by sediment and connected, but had minimal erosion and had an SBI of 2. Two crossings, along road 16654 (connecting
Morrell Creek roads with Trail Creek r oads) and along road 4359 (minor Morrell Creek tributary), were plugged by sediment and delivered to a stream, but had minimal erosion. These crossings had SBI values of 3 and 4 (orange dots on Figure 42 ). One diversion, along road 56079 (Spring Creek, Fig ure 43 ), was plugged by wood and diverted roughly 100 m down the road. The resulting erosion of the road surface
delivered about 910 ft 3 (25.6 m 3 , 41.0 Mg) to Spring Creek (accounted for in the fill erosion piece,

Section 4.7 ). That particular crossing pip e had an SBI value of 3 (orange dot on Figure 42 ). The diversion was repaired by a passing fire crew.

Figure 43

. Spring Creek diversion that delivered 41 Mg of sediment to the stream.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

70 

### Poorman Creek

Field crews recorded 53 stream crossings in the Poorman Creek area. Only the 29 crossings with a
culvert were included in the SBI calcu lations. The 2 4 crossings that did not have a culvert were bridges ( eight crossings) or were natural fords ( 16) and were not included. Risk of pipe plugging is not a factor at these crossings.

The SBI values for the Poorman Creek area had an average of 1 .7 for the 29 stream crossings. There

were no stream crossings with an SBI of 4, five crossings with an SBI of 3, nine crossings with an SBI of 2,
and 15 crossings with an SBI of 1 ( Figure 44 ). All five o f the cr ossings with values of three had a pipe
diam eter to channel width ratio of 0. 4 or less (small pipe, large stream), and two had a pipe that was 1/3
or less than the width of the stream

. Two crossing s with an SBI of 2 had a pipe that wa s half the width of
the channel.

The total fill volume at risk for all the stream crossings was 1399 m 3 ( 1830 yd 3 ). Fill volumes ranged from

6 m 3 ( 8 yd 3 ) to 318 m 3 ( 416 yd 3 ), and had a mean volume of 48 m 3 ( 63 yd 3 ). This is similar to previous findings for the middle Blackfoot River at 38 stream crossings, which had an average of 116 tons of fill per crossing ( Montana Department of Environmental Quality 2008 ). Overtopping

- type fill failure will not occur at bridges, so no fill volume risk was calculated at these locations. In the Poorman Creek area, eight of 53 stream crossings ( 15 %) , including three natural fords, had the potential to divert streamflow
down the road in one or more directions. Bridges also had no diversion potential.

Figure 45

. The stream crossings with the highest risk of plugging and the
most severe consequences
of failure in the Poorman
Creek area. Figure 44

. Distribution of SBI values for
the Poorman Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

71 There was one crossing with an SBI of 3 and diversion potential ( Figure 45 ). There wa s a total of 21 m 3
( 27 yd 3 ) of fill at risk at this point. There were no problems already apparent at this location. The three crossings with a high SBI but no diversion had 582 m 3 ( 761 yd 3 ) of fill at risk, and the seven crossings
with diversion but a low SBI had 142 m 3 ( 186 yd 3 ) of fill at risk.

There were two natural ford type crossings in the western portion of the Poorman Creek area on road

1842

- A2 that were observed to divert flow down the road, though no major erosion was obs erved at the
time of the survey ( Figure 46 ).

Figure 46

. S tream diversion at a natural ford in the western portion of the Poorman Creek area. No major erosion was observed.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

72 

### Cold Creek

Field crews recorded 115 stream crossings in the Cold Creek area. Only the 71 crossings with a culvert
were included in the SBI calculations. The 42 crossings that did not have a culvert were bridges ( six

crossi ngs), nat ural fords ( 3 6) or log culverts (two) and were not included. Risk of pipe plugging is not a
factor at bridges and fords, and log culverts are generally considered to be blocked by design.

The SBI values for the Cold Creek area had an average of 2.3 for the 71 stream crossings. There were

two stream crossings with an SBI of 4, 26 crossings with an SBI of 3, 31 crossings with an SBI of 2, and 12 crossings with an SBI of 1 ( Figure 47 ). Of the 26 crossings with an SBI of 3, 17 had a pipe diameter to
channel width ratio of 0. 5 or less (small pipe, large stream), and five had a pipe that was 1/3 or less than
the width of the stream

. Nine crossing s with an SBI of 2 had a pipe that wa s half the width of the
channel.

The total fill volume at risk for all the st ream crossings was 2095 m 3 ( 2740 yd 3 ). Fill volumes ranged from

4 m 3 ( 5 yd 3 ) to 268 m 3 ( 351 yd 3 ), and had a mean volume of 31 m 3 ( 41 yd 3 ). This is similar to previous findings for the nearby middle Blackfoot River at 38 stream crossings, which had an avera ge of 116 tons Figure 47

. Distribution of SBI values
for the Col d Creek area.

Figure 48

. The stream crossings with the highest risk of plugging and the
most severe consequences
of failure in the Cold Creek

area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

73 of fill per crossing ( Montana Department of Environmental Quality 2008 ). Overtopping

- type fill failure will not occur at bridges, so no fill volume risk was calculated at these locations. In the Cold Creek area,
39 of all 115 stream crossing s ( 34 %)

, had the potential to divert streamflow down the road in one or
more directions.

There were 14 crossing s with an SBI of 3 or 4 and diversion potential ( Figure 48 ). There was a total of

332 m 3 ( 434 yd 3 ) of fill at risk at this points. Of those 14 c rossings, half received the stream flow from the ditch, though this appeared to be intentional (streams were intercepted by the ditch and discharged through the next culvert down road 90509) . No other problem s were already apparent at these
location s . The 14 crossings with a high SBI but no diversion had 427 m 3 ( 558 yd 3 ) of fill at risk, and the 25 crossings with diversion but a low SBI had 234 m 3 ( 306 yd 3 ) of fill at risk.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

74 

### 4.7 Drain Point Condition and Fill Erosion

The GRAIP inventory involves an assess ment 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 i nsufficiently 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 cons idered problematic if they have excess deposition or gullying. Non

engineered features are almost always a problem due to a blocked ditch, a gully, or a broken outside berm, but are not considered problematic if they occur due to an outsloped road and do n ot have any fill erosion. Stream crossings culverts are considered a problem if they are blocked by sediment or wood, crushed or rusted significantly, incising, scouring, losing much water from flow around the pipe, or have a high SBI with diversion potent ial ( see Section 4.6 for more detail on SBI and diversion). 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.

If a drain point is observed to have fill erosion, the volume is estimated. Fill erosion can be determined to be connected to the stream channel network if its associated drain point is co nnected to the channel. This mass of sediment may be pulsed (if the fill failure happens at once), chronic (if the fill gradually erodes), or pulsed and then chronic (initial failure, followed by more gradual erosion); it is unknown what proportion of this mass belongs to each category. Delivered masses of fill erosion are distributed over a 20 year time span in order to compare their magnitude with that of the road surface fine sediment (a chronic sediment source). Twenty years is used because, in most pla ces, that is roughly the maximum age of a feature still easily observable in the field. In any given year, the amount of sediment delivered to streams from gullies is likely to be higher or lower than the rate we calculate.

Table 26

. Drain point condition problems and fill erosion below drain points, Center Horse and Morrell/Trail project area.

Drain Type Count Problems Fill Erosion

Number % of Total Number % of Total

Broad Based Dip 1413 387 27% 6 0.4%

Diffuse Drain 931 0 0% 13 1%

Ditch Relief Culvert 392 155 40% 11 3%
Excavated Stream Crossing 4 0 0% 0 0%

Lead Off Ditch 135 1 0.7% 0 0%

Non

- Engineered Drain 1102 113 10% 28 3%
Stream Crossing 146 44 30% 4 3%
Sump 24 11 46% 0 0%

Water Bar 914 100 11% 21 2%

All Drains 506 1 811 16% 83 2%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

75 

### Center Horse Morrell

- Trail Project Area

Within the Center Horse and Morrell/Trail project area, 16% of all drain points (811 of 5061) had one or more problem of some type ( Table 26 ; Figures 49 and 50 ). Sumps had the highest rate of problem s (11 of 24, 46%), followed by ditch relief culverts (155 of 392, 40%), stream crossings (44 of 146, 30%), and broad based dips (387 of 1413, 27%). Diffuse road segments (931 features total) and excavated stream crossings (four features total) did not have any problems. Water bars had problems at 100 of 914 locations (11%) and non

- engineered drain s had problems at 113 of 1102 locations (10%).

Fill erosion was present at 2% of all drain points, totaling 85 m 3 (3000 ft 3 ; Table 27 ). Fill erosion was

most co mmon at non

- engineered drains, with 28 of 1102 (3%) eroding 23 m 3 (820 ft 3 ). Water bars had fill erosion at 21 of 914 locations (2%; 8 m 3 ; 280 ft 3 ); diffuse drains at 13 of 931 locations (1%; 2 m 3 ; 80
ft 3 ); and ditch relief culverts at 11 of 392 locations (3%; 4 m 3 ; 150 ft 3 ). Stream crossings had the most
mass of fill erosion of 44 m 3 (1550 ft 3 ) eroded from four crossings. More than half of this mass was from the Spring Creek flow diversion. Using the same bulk density as above, fill erosion at drain point s that were connected to the stream channel network totaled 87 Mg, most of which occurred at stream crossings (70 Mg) and non

- engineered drains (13 Mg). This was 64% of the sediment produced by fill erosion at drain points. Over a 20 year period, 4.4 Mg/yr of sediment were delivered to stream channels, or roughly one quarter of the rate of road surface fine sediment delivered to stream channels annually. It would take about four years for the fine sediment delivery from road surfaces to equal the Figure 49

. Specific drain point problems by drain type i n the Center Horse and Morrell/Trail project area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

76 total mass of delivered sediment from fill erosion

. Actual annual sediment delivery from fill erosion is likely higher or lower than these estimates in any given year, and when the largest failures occur, they are often repaired and quickly become difficult to recor d accurately.

Figure 50

. Drain point problems in the Spring Creek watershed.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

77 Table 27

. Fill erosion below drain points, volumes and masses, Center Horse and Morrell/Trail project area.

Drain Type Count Number

With

Fill

Erosion % of

Total Total

Volume Mass

Sediment

Produced (M g) Mass

Sediment

Delivered (Mg) %

Sediment
Delivery Average

Delivery Rate

Over 20 Years (Mg/yr) (m 3 ) (ft 3 )

Broad Based Dip 1413 6 0.4% 4 140 6 2 30% 0.1

Diffuse Drain 931 13 1% 2 80 3 0 0% 0

Ditch Relief Culvert 392 11 3% 4 150 7 0.1 2% 0.01

E xcavated Stream
Crossing 4 0 0% 0 0 0 0 0% 0

Lead Off Ditch 135 0 0% 0 0 0 0 0% 0

Non

- Engineered Drain 1102 28 3% 23 820 37 13 36% 1
Stream Crossing 146 4 3% 44 1550 70 70 100% 4
Sump 24 0 0% 0 0 0 0 0% 0

Water Bar 914 21 2% 8 280 13 2 15% 0.1

All Dr ains 5061 83 2% 85 3000 136 87 64% 4Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

78 

### Poorman Creek

Within the Poorman Creek are a, 12 % of all drain points ( 270 of 2190 ) had one or more problem of some type ( Table 28 ; Figures 51 and 52 ). Ditch relief culverts had the highest rate of problems ( 18 of 56

, 32 %), followed by broad based di ps ( 120 of 412

, 29 %) ; sumps had a rate of 50%, but there were only two

Table 28

. Drain point condition problems and fill erosion below drain points, Poorman Creek area.

Count Problems Fill Erosion

Number % of Total Number % of Total

Broad B ased Dip 412 120 29% 2 0.5%

Diffuse Drain 417 0 0% 1 0.2%

Ditch Relief Culvert 56 18 32% 1 2%

Lead Off Ditch 8 0 0% 0 0%

Non

- Engineered Drain 693 63 9% 16 2%
Stream Crossing 53 7 13% 0 0%
Sump 2 1 50% 0 0%

Water bar 549 61 11% 2 0.4%

All Drains 21 90 270 12% 22 1%

Figure 51

. Specific drain point problems by drain type in the Poorman Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

79 sumps recorded. Diffuse road segments ( 417 features total) and lead off ditches ( eight features) did not have any problems. Stream crossings had problems at seven o f 53 locations (13 %), w ater bars had problems at 61 of 549 locations (11%) and non

- engineered drain s had problems at 6 3 of 693 locations ( 9 %).

Table 29

. Fill erosion below drain points, volumes and masses, Poorman Creek area.

Drain Type Count Number
With
Fil l

Erosion % of

Total Total Volume Mass

Sediment
Produced (Mg) Mass

Sediment
Delivered (Mg) %

Sediment Delivery Average

Delivery

Rate O ver 20 Years (Mg/yr) (m 3 ) (ft 3 )

Broad Based Dip 412 2 0 .5 % 1 50 2 0 .5 20% 0.02

Diffuse Drain 417 1 0 .2 % 0.1 10 0.2 0 0% 0

Ditch Relief Culvert 56 1 2% 0.3 10 0.5 0 0% 0

Lead Off Ditch 8 0 0% 0 0 0 0 0% 0

Non

- Engineered Drain 693 16 2% 8 300 13 3 22% 0.1
Stream Crossing 53 0 0% 0 0 0 0 0% 0
Sump 2 0 0% 0 0 0 0 0% 0

Water bar 549 2 0 .4 % 1 40 2 0 0% 0

All Drai ns 2190 22 1% 11 400 18 3 .4 19% 0.2

Figure 52

. Drain point problems in the western half of the Poorman Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

80 Fill erosion was present at 1 % of all drain points, totaling 11 m 3 ( 403 ft 3 ; Table 29 ). Fill erosion was most

common at non

- engineered drains, with 16 of 693 (2 %) eroding 8 m 3 ( 296 ft 3 ). Water bars had fill

erosion at two of 549 locations ( 0.4 %; 1 m 3 ; 40 ft 3 ); broad based dips at two of 412 locations (0.5 %; 1

m 3 ; 50 ft 3 ); and ditch relief culverts at 1 of 56 locations (2%; 0.3 m 3 ; 12 ft 3 ). Non

- engineered drains had
the most mass of fill erosion . Using the sa me bulk density as above, fill erosion at drain points that were
connected to the stream channel network totaled 3 .4 Mg, 3 Mg of which occurred at non

- engineered
drains

. This was 19 % of the sediment produced by fill erosion at drain points. Over a 20 year period, 0.2 Mg/yr of sediment were delivered to stream channels, which is negligible compared to other sources. Actual annual sediment delivery from fill erosion is likely higher or lower than these estimates in any given year, and when the largest failure s occur, they are often repaired and quickly become difficult to record accurately.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

81 

### Cold Creek

Within the Cold Creek area, 8 % of all drain points ( 284 of 3584 ) had one or more problem of some type ( Table 30 ; Figures 53 and 54 ). Stream crossings had the highest rate of problems ( 45 of 115

, 39 %), followed by ditch relief culverts ( 80 of 266

, 30%). Diffuse road segments ( 670 features total) , lead off

Table 30

. Drain point condition problems and fill erosion below drain points, Cold Creek area.

Drain Type Count Problems Fill Erosion

Number % of Total Number % of Total

Broad Based Di p 1050 14 1% 18 2%

Diffuse Drain 670 0 0% 0 0%

Ditch Relief Culvert 266 80 30% 1 0.4%

Lead Off Ditch 139 0 0% 0 0%

Non

- Engineered Drain 1097 127 12% 3 0.3%
Stream Crossing 115 45 39% 1 1%
Sump 1 0 0% 0 0%

Water Bar 246 18 7% 0 0%

All Drains 3584 28 4 8% 23 1%

Figure 53

. Specific drain point problems by drain type in the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

82 ditches (139 features total), and sumps ( one feature total) did not have any problems. N on

- engineered
drain s had problems at 127 of 1097 locations ( 12 %) , w ater bars had problems at 18 of 246 locations ( 7 %) , and broad based dips had problems at 14 of 1050 locations (1%).

Table 31

. Fill erosion below drain points, volumes and masses, Cold Creek area.

Drain Type C ount Number
With
Fill

Erosion % of

Total Total
Volume Mass

Sediment
Produced (Mg) Mass
Sediment
Delivered (Mg) %
Sediment Delivery Average

Delivery

Rate Over

20 Years (Mg/yr) (m3) (ft3)

Broad Based Dip 1050 18 2% 3 90 4 0 0% 0

Diffuse Drain 670 0 0% 0 0 0 0 0% 0

Ditch Relief Culvert 266 1 0.4% 0.03 1 0.05 0 0% 0

Lead Off Ditch 139 0 0% 0 0 0 0 0% 0

Non

- Engineered Drain 1097 3 0.3% 0.4 20 1 0.2 33% 0.02
Stream Crossing 115 1 1% 0.2 10 0.3 0.3 100% 0.05
Sump 1 0 0% 0 0 0 0 0% 0

Water Bar 246 0 0% 0 0 0 0 0% 0

All Drains 3584 23 1% 3 114 5 0.5 10% 0.005

Figure 54

. Drain point probl ems in the Cold Creek area.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

83 Fill erosion was present at 1 % of all drain points, totaling 3 m 3 ( 110 ft 3 ; Table 31 ). Fill erosion was most

common at broad based dips , with 18 of 1050 ( 2 %) eroding 3 m 3 ( 90 ft 3 ). Non

- engine ered drains had fill

erosion at 3 of 1097 locations (0.3 %; 0.4 m 3 ; 20 ft 3 ); stream crossings at 1 of 115 locations (1%; 0.2 m 3 ; 10 ft 3 ) ; and ditch relief culverts at 1 of 266 locations (0.4 %; 0.03 m 3 ; 1 ft 3 ). Broad based dips had the
most mass of fill ero sion. Using the same bulk density as above, fill erosion at drain points that were
connected to the stream channel network totaled 0.5 Mg, which occurred at stream crossings ( 0.3 Mg)
and non

- engineered drains ( 0.2 Mg). This was 10 % of the sediment produced by fill erosion at drain points. Over a 20 year period, 0.005 Mg/yr of sediment were delivered to stream channels, which is negligible compared to other sources . Actual annual sediment delivery from fill erosion is likely higher or
lower than these estima tes in any given year, and when the largest failures occur, they are often repaired and quickly become difficult to record accurately.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

84 

### 4.8 Risks by Maintenance Level

Sediment production and delivery, connected length of road, drain point problems, and fill erosion were analyzed by road maintenance level for the three areas. Gully and landslide risks were analyzed for the Center Horse and Morrell/ Trail project area. Poorman Creek and Cold Creek did not have enough gullies or landslides for this analysi s. R oad surface fine sediment delivery risks were hypothesized to be higher on roads that received more maintenance (Maintenance Levels 3 and 4), and lower on roads that received less maintenance (ML 1 and 2), due to the positive correlation of maintenance level with traffic. Mass wasting risks and other infrastructure problems were hypothesized to be higher on roads that received less maintenance (ML 1 and 2), as many of these issues may be preventable. Unclassified roads are usually small and seldom used, and are generally equivalent to ML 1 or 2. Appendix A shows
these risks for each of the three areas and summarized for all three.

For all three areas, there was roughly twice as much total sediment delivery on the ML 3 roads as on any of the ML 1 or 2 or unclassified roads ( Figure 55 , note the logarithmic scale )

. Sediment production, as well, was higher on the higher maintenance level roads. Specific sediment delivery (delivery normalized by length of road in each ML category) was almost five times higher on the ML 3 roads than any of the
ML 1 or 2 or unclassified roads. For sediment delivery as a percentage of production , each maintenance level was roughly equivalent , though the ML 3 roads had the highest percent , suggesting that the higher delivery on th e higher maintenance levels was due to the higher production

. Figure 55

. Sediment delivery risks for all three areas. Note that the logarithmic scale begins at 10 . Only the Center Horse and Morrell/Trail project area had ML 4 roads, so these were omitted from thes e graphs. Specific sediment is normalized by road length in each ML category.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

85 In the Center Horse and Morrell/Trail project area, there were more landslides with more mass on the
lower maintenance level roads than the higher ( Figure 56 )

. The number, mass, and deliver ed mass of gullies exhibited a similar pattern in this area

. This pattern is stronger when the delivered mass from gullies is normalized by total road length in each ML category, with a roughly ten

- fold difference
between the unclassified and ML 1 roads a nd the M L 2, 3, and 4 roads. Fill erosion mass, delivered mass, specific delivered mass, and percent mass delivered were also higher on the lower maintenance level
roads in all three areas ( Figure 57 ) . Regular maintenance may address the road problems that lead to mass wasting. An alternative hypothesis is that the higher maintenance level roads tend to cross less steep slopes in the valley bottom, which is less conducive to mass wasting. In the Center Horse and Morrell/Trail project area, the average slope that the ML 4 roads traversed was about half of the average slope that the ML 1, 2, and 3 roads traversed. Figure 57

. Gully and landslide risks for the Center Horse and Morrell/Trail project area. Note the logarithmic scale. The

other two areas did not have e nough gullies or landslides for this analysis.

Figure 56

. Fill erosion total mass and delivered mass for all three project areas. Note the change in axis scale for Specific Fill Erosion Delivery on the left graph.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

86 Drain point problems did not fit the expected pattern, as although there were more drain points with problems on the lower maintenance level roads , the higher maintenance level roads had a higher percentage of drain points with problems ( Figure 58 ). Heavier traffic may result in wear on infrastructure that outpaces the effects of neglect on the lower maintenance level roads , though given enough time , the effects of neglect may be larger

. Additionally, different types of drain points preferentially occur on the different maintenance levels, and each type of drain point has a different overall problem rate.

Figure 58

. Drain point problems for all three project areas.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

87 

## 5.0 Jammer Road Inventory and Observations

J ammer roads are decades

- old closely

- spaced unsurfaced logging roads built to a low standard that contour along the hillslope roughly every 30 m (100 ft) of slope length. In the Center Horse and Morrell/Trail project area, there were 380 km (230 mi) of jamm er roads concentrated in 20 to 25 complexes that encompass 0.25 mi 2 to 1 mi 2 each ( Figure 5 9 )

. This is about the same total length as there were regular, non

- jammer roads.

Though these roads were generally un maintained since they were in use as logging r oads, the risk s they

may pose to aquatic systems in the future were unknown. On the one hand, most of these roads were heavily vegetated and initially appear ed to be stable; on the other hand, infrastructure along these
roads was old and likely to fail or to have already failed. Prior field observations suggested that most of the sediment delivery and mass wasting risks from jammer roads occurred at stream crossings. In order to evaluate these risks, we inventoried two complexes in the Center Horse project area using GRAIP ( section 5.1 , below) , and conducted a census of every jammer road

- stream intersection in both project

areas ( section 5.2 . below)

.



### 5.1 Complete Complex Inventory

Two complete jammer road complexes totaling 18. 5 km in the Center Horse proj ect area were inventoried using the GRAIP method. The eas tern complex was located in upper Black Canyon (13.3 km, Figure 59

. Jammer road locations in the Center Horse and Morrell/Trail project area, with the complete surveyed complexes and the stream crossings that we surv eyed.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

88 8.3 mi ) , and the western complex was located on the south face of Morrell Mountain ( 5.1 km, 3.2 mi; Figure 5 9 ). The Black Canyon complex may b e treated at some point in the future, and the GRAIP
method will be used to monitor the outcomes of the treatment.

There w ere 325 drainage points recorded. Drainage on these roads occurred mostly through diffuse road segments (158 points) and non

- engineered drains ( 124 points ). Most of the road surfaces were undrivable and covered in grass, herbaceous vegetation, or small to medium sized trees ( 17.9 of 18.4 km; 97%). Table 32

. Summary of sediment production and delivery at drain points on the jammer road complexes that were

invento ried with GRAIP in the Center Horse and Morrell/Trail Project Area.

Drain Point Type Count Sediment
Production (kg/yr) Sediment

Delivery (kg/yr) %

Sediment Delivery Length

Connected (m) % Length

Connected

Broad Based Dip 28 90 0 0% 0 0%

Diffuse Drain 15 8 560 2 0.4% 20 0.1%

Ditch Relief Culvert 1 0 0 0% 0 0%

Lead Off Ditch 0 0 0 0% 0 0%

Non

- Engineered Drain 124 350 6 2% 50 1%
Stream Crossing 9 10 10 100% 100 100%
Sump 0 0 0 0% 0 0%

Water Bar 5 8 0 0% 0 0%

All Drains 325 1020 18 2% 160 1%

Figure 60

. Fine sediment delivery to channels by road segment and drain point in the upper Black Canyon jammer road complex. The road lines and drain points
are colored to indicate the mass of fine
sediment delivered to chan nels.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

89 Overall, both complexes had very low sediment production and delivery ( Table 32 ). Roads were highly vegetated and had low slopes. Sediment production totaled 1 Mg /yr for both complexes. There were no delivering drain points in the Morrell Mountain complex. In the Black Canyon complex, there was 0.02 Mg /yr of fine sediment delivered from the road surface to the stream from 0.2 km of road length ( 2% of all sediment produced from 1% of total length; Figure 60 ). An e stimate of total road surface fine sediment delivery for the Center Horse and Morrell/Trail project area was made by applying the road surface delivery rate from these two complexes to the entire length of jammer roads ( Table 33 ). The
estimated total road surface fine sediment delivery was 0.4 Mg/yr.

Table 33

. Estimation of sediment delivery from road surfaces for all jammer roads in the Center Horse and Morrell/Trail project area, based on the road surface sediment delivery rate pe r kilometer from the inventoried complexes.

Length of Road Surveyed (km | mi) 19 11
Total Length of Jammer Roads in Center Horse and Morrell/Trail (km | mi) 376 234

Total Road Surface Sediment Delivery (Mg/yr) 0.02

Road Surface Delivery Rate for Surv eyed Roads (Mg/yr/km) 0.001

Estimated Road S urface Delivery for All Jammer Roads (Mg/yr) 0.4

In the Black Canyon complex, there was a natural ford stream diversion from a two foot wide side

channel onto the road. As a result of this diversion, t here were two gullies observed

, totaling 29 Mg ( Figure 61 ; Table 3 4 ). Both gullies delivered their sediment to the stream. Also as a result of the stream
diversion , there were two non

- engineered drains observed to have fill erosion totaling 25 Mg. One of

Figure 61

. Fill e rosion a nd gullies in the Black Canyon jammer road complex. All mass wasting was due to a diverted stream crossing. There was no other mass wasting observed in either inventoried jammer complex.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

90 the t wo drain points with fill erosion delivered to the stream, totaling 23 Mg. This m ass wasting totaled 53 Mg, with 51 Mg delivered to the stream. Averaged over 20 years, the mass wasting delivery totaled 3 Mg/yr. There were no other observed instances of ma ss wasting, including landslides

, in either complex.

Table 34

. Mass wasting masses and delivery for the observed mass wasting in the Black Canyon jammer complex. No mass wasting was observed in the Morrell Mountain complex.

Landsl ide Mass (Mg) 0 Gully Mass (Mg) 29 Fill Erosion Mass (Mg) 25 Total Mass Wasting (Mg) 53 Mass Wasting Delivery (Mg) 51
Mass Wasting Delivery Over 20 Years (Mg/yr) 3

The Black Canyon complex was chosen for this inventory because it was thought to have a high rate of and potential for sediment delivery and other problems . Based on other field observations at other complexes , as well as the stream diversion in the Black Canyon complex , most delivery of sediment from jammer roads probably occurs at stream crossings when the fill ero des into the stream or diverts down
the road (see below). Other mass wasting, particularly that delivers to the stream channel

, is probably

rare.

Other than sediment from stream crossing

- related erosion, jammer roads in the Ce nter Horse and Morrell/Trail project area are probably not a major sediment source. Non

- stream crossing r isks are
observed and estimated to be very low. However, it is unknown what the response of these roads may be after a forest fire. Without vegetation , there may be a greater sediment supply, more runoff , and a greater chance of mass wasting. Stream crossings risks are evaluated in the following section.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

91 

### 5.2 Stream Crossing Survey

Prior field observations suggested that most of the risk present on th e jammer roads in the Center Horse and Morrell/Trail project area occurred at stream crossings. In order to evaluate this risk, we conducted a census of all of the stream crossings on jammer roads in the area ( Figure 59 ) . Crews followed streams up to each consecutive stacked road until the stream channel head was reached or there were no more upslope roads. Streams were defined as continuous features with a bed, banks, and evidence of flow for some part of most years. No mini mum size was used in this defini tion because even small features can cause problems under the right conditions. TauDEM 4.0 ( http://hydrology.usu .edu/taudem/taudem4.0 ) was used to model the probable stream location s. There were a number of model ed streams that were not present in the fiel d, and streams that were found in the field that were not present in the model.

There were 71 stream crossings on jammer roads surveyed in the course of the census. There were 61
natural ford

- type crossings (no infrastructure) and ten crossings with cu lverts. Some of the natural fords may have been log culverts at one time, but the evidence has likely decomposed. Observations at each crossing included channel width, presence of problems such as a blocked culvert or scoured road, volume of fill erosion, and presence of stream diversion. Fill erosion risks were further analyzed to evaluate the rough probability and amount of remaining risk.

Figure 62

. Stream crossings with observed fill erosion on jammer roads in the Center Horse and Morrell/Trail project area. The largest fill erosion volume was due to a

stream diversion.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

92 There were 31 stream crossings with fill erosion (44% of all crossings on jammer roads), totaling 207 m 3
(7310 ft 3

, 331 Mg; Figure 62 ; Table 35 ) . One crossing in lower Black Canyon in the Center Horse project

area with a stream diversion had more than half of the total fill erosion ( 3980 ft 3 , 113 m 3 , 180 Mg). Most crossings with fill erosion had under 300 ft 3 (10 m 3 , 15 Mg)

. The average fill erosion per crossing was 100
ft 3 ( 3 m 3

, 5 Mg). Without the largest outlier volume of fill erosion, the average fill erosion per crossing

was 50 ft 3 (1 m 3 , 2 Mg). Since this fill erosion occurred at stream crossings, all of it deliver ed to the stream. Averaged over 20 years, the fill erosion totaled 17 Mg/yr, which is roughly equivalent to the road surface fine sediment delivery for the non

- jammer roads in the Center Horse and Morrell/Trail project area. Without the largest outlier mas s of fill erosion, the delivery rate over 20 years was 8 Mg/yr.

Table 35

. Fill erosion statistics for the jammer road stream crossings
observed in the Center Horse and Morrell/Trail project area.

Number Surveyed 71

Number With Fi ll Erosion 31

% Fill Erosion 44% Volume Fill Erosion (ft 3 ) 7310 Volume Fill Erosion (m 3 ) 207 Mass Fill Erosion (Mg) 331

Fill Erosion Delivery Over 20 Years (Mg/yr) 17

Mean Fill Erosion Per Crossing (m 3 ) 3

Estimated Mean Total Original Fill Volume at Each Crossing (m 3 ) 12

% of Estimated Original
Fill Volume Eroded (m 3 ) 25 %

The volume of fill was estimated at each crossing as being bounded at the base by an area 1.2 times the channel width, with side slopes climbing to the road surface at a slope of 33%. We assumed a road width of 14 ft, and a fill depth of five feet. The slope of the hillslope was used to determine the length of the crossing bottom according to the slopes given by Megahan (1976), modified to account for the
narrower road. The estima ted average volume of fill at each crossing was 12 m 3 (420 ft 3 ; Figure 62 ). Using the average volume of fill erosion per crossing, it is estimated that about 25 % of the possible fill erosion has already been eroded, with 75 % (about 600 m 3 or 22 ,000 ft 3 ) re maining. Much of the
observed fill erosion included volumes eroded from stream diversion s , so the observed fill erosion volume may be larger than the estimated available volume. There may be more than 75 % of the available fill remaining. However, the proce ss of the stream channel cutting through what amounts to a flat step in its longitudinal profile takes time, and will happen episodically during high flow events. Each stream crossing will respond at a different rate due to the available transport capacity of the stream, and may include some deposition

.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

93 In order to prioritize the stream crossings with the greatest risk of future fill erosion, we used a logistical regression technique (local fit, locfit) in the R statistical computing environment that comp ared the stream crossings in the Center Horse project area with fill erosion to those without, according to the slope of the hillslope on which the stream runs ( Figure 63 ). The sample includes all crossings with fill erosion, but may be too small to draw b road conclusions. It was found that on hillslopes of greater than about 40%, every stream crossin g in the Center Horse area had fill erosion

. Figure 63

. Probability graph o utput from the local fit regression in R. Fill Erosion Probability is a yes/no field (specific volumes are not accounted for). Though fill erosion occurs throughout the slope range, above about 40% slope

, all have fill erosion.

Figure 64

. Stream crossings on jammer roads with problems, including observed overtopping, diversion, and culvert problems.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

94 Other problems were observed at the inventoried jammer road stream crossings. Five of the crossings (7%) had ev idence of current or recent stream diversions ( Figure 64 ; Table 36 ). Ten natural ford type crossings were observed to have one direction of possible diversion (two of them already had diversions observed). One other crossing with a culvert and one diversio n direction was observe d to have been overtopped in the past. Four other crossings (6%) were observed to have other problems, including scoured road surfaces above the crossings and blocked or failing culverts

. This is nine crossings in total,

or 13%.

Tab le 36

. Stream crossings on jammer roads with problems in the Center Horse and Morrell/Trail project area.

Number of Crossings With
Stream Diversion Evidence 5

% of Crossings With Stream
Diversion Evidence 7%

Number of Crossings With
Other Problems 4

% of Crossings With Problems 6%Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

95 

## 6.0 Summary and Conclusions

Field inventory and modeling anal ysis of the public roads in the Center Horse and Morrell/Trail project area, the Poorman Creek watershed area, and the Cold Creek watershe d area in the Southwest Crown of
the Continent in western Montana using the GRAIP model provided detailed, site specific data on
sediment

- related watershed impacts from roads. Impacts are both chronic, in terms of annual sediment input to streams, and puls ed, such as during storm events when road connectivity to the channel networks is at its maximum. Inventory data was collected on 769 km ( 478 mi) of road, including 10,759 drain points, by two field crews during the summer months of 2012 and 2013 (June to October). Additionally, jammer

- type logging roads were sample d and their road

- stream intersections were surveyed in the Center Horse and Morrell/Trail project area.

The GRAIP model was used to predict sediment risk and sediment

- related impacts from roads. The model predicts road to stream hydrologic connectivity, sediment delivery to streams, downstream sediment accumulation, risks of shallow landslides caused by roads, gully initiation risk below drain points, and risks to road

- stream crossings ( Table s 37 , 38, and 39 ). Inventory data is also used to locate and describe problems with existing drain points. In addition, GRAIP model data will be compared to in

stream PIBO monitoring for these project area s in a separate document.



### Center Horse and Morrell/Tr ail Project Area Summary

In the Center Horse and Morrell/Trail project area, there were 407 km (253 mi) of road and 5061 drain points surveyed. Table 3 7 presents a summary of the findings for this project area. Hydrologic connectivity was found to be a rel atively low 4% of all road length at 16 km out of 407 km (10 mi out of 252 mi). The model predicted 21 .4 Mg/yr of delivered road surface fine sediment to stream channels,

which is 5 % of the 456 Mg generated annually by the road surface. This sediment was d elivered through 314 of 5061 (6%) drain points. There was 16.2 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 76 % of all sediment delivery and 57 % of all sediment produced within 10 m of a stream crossing.

Specific sediment due to road surface

- related sediment for the whole Center Horse and Mo rrell/Trail project area was 0.10 Mg/km 2 /yr, or 1 % of the observed total average fine sediment yield for five nearby areas as determined by reservoir coring or suspended sediment extrapolati ons. Including sediment delivered to streams through other sources (landslides, gullies, and fill erosion at drain points), the specific sediment fo r the whole project area was 0.21 Mg/km 2 /yr, or about 2% of the observed average fine sediment yield for the nearby areas. Some heavily impacted stream reaches had road sediment delivery values as high as 4.9 Mg/km 2 /yr with only road surface fine sediment, or 18.1 Mg/km 2 /yr including mass wasting sediment. Reaches in Shanley, Little Shanley, Blacks Canyon, and

l ower Spring Creeks showed particularly high specific sediment values above 0. 3 Mg/km 2 /yr, or 3% to

19 % above the reference sediment yield.

There were 18 landslides observed by field crews in the course of the inventory, with a total volume of

1319 m 3 (172 6 yd 3 ). Of those, 10 were road related. It was conservatively estimated that 176 Mg of landslide derived sediment has been delivered to streams, which is roughly half the rate of that from road surfaces over 20 years (8.8 Mg/yr). It would take about eight years for the fine sediment delivery from road surfaces to equal the total mass of delivered sediment from landslides. Calibrated stabilitySouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

96 index modeling with SINMAP conservatively showed that 6 km 2 (2 mi 2 ), or 3%, of the watershed area was put at higher risk of shallow landslide initiation by road drainage.

Gullies were observed at 33 locations by field crews, totaling 208 m 3 (272 yd 3 ) in volume, and all occurring in wet swales. It was estimated that these gullies delivered 217 Mg of sedi ment to the stream channel, equivalent to half the rate of that from road surfaces over 20 years (11 Mg/yr). It would take
about ten years for the fine sediment delivery from road surfaces to equal the total mass of delivered
sediment from gullies

. Of 3713 applicable drain points, 587 (16%) had an elevated risk of gullying. The critical gully initiation index (ESI) was found to be 14. The average ESI for the points without gullies was 9, while it was 11 for the points with gullies. The gully occurrence rate for drain points that fell above the ESI threshold was 1.0% versus 0.5% for points that fell below the ESI threshold.

There were 116 stream crossings with culverts (as opposed to bridges or fords) recorded. The average blocking index (SBI) for these poin ts was a moderate to low 1.9. There were 25 crossings with an elevated SBI of 3. Two crossings had an SBI of 4, which is the highest possible value. The total calculated volume of fill at risk in an overtopping type event was 6840 m 3 (8950 yd 3 ). There were 55 stream crossings with the potential to divert stream flow from a plugged culvert down the road and onto unchanneled hillslopes. There were 1 4 stream crossings with an SBI of 3 or 4 and diversion potential

, four of which were observed to have already fa iled or be at risk for imminent failure

. There was a total
of 824 m 3 (1077 yd 3 ) of fill at risk at these points. Six overtopped crossings were observed, five due to sediment plugging and one due to wood plugging. Three of those were due to undersi zed pipes , and one
delivered 2 6 m 3 (910 ft 3 ) to streams. Table 37

. Summary of GRAIP

- predicted road risk predictions, Center Horse and Morrell/Trail
project area.

Impact/Risk Type GRAIP Predicted Risks

Road

- Stream Hydrologic Connec tivity 4% of road length, 16 km; 6% of drain points connected

Fine Sediment Delivery 5% of sediment produced, 21.4 Mg/yr

Sediment in Streams 0.21 Mg/km 2 /yr; 2% of average sediment yield for nearby areas

Landslide Risk Estimated 176 Mg of sediment delive red to streams, 3% of
watershed area with elevated risk due to roads
Gully Risk Estimated 11 Mg/yr of sediment delivered to streams, 16% of all drain points exceed ESI crit threshold
Stream Crossing Risks

- plug potential 27 sites (23%) with elevat ed risk (SBI > 2)

- fill at risk 6843 m 3 fill at risk, average 60 m 3 per crossing

- diversion potential 61 sites (42%) with diversion potential

Drain Point Problems 811 drain points (16% of all drain points) with problems, 61 m 3
of fill erosion ( 2% of drain points), estimated 2.9 Mg/yr of fill

delivered to streamsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

97 Of the 5061 recorded drain points, 811 (16%) had one or more problem of some type (e.g. blocked or crushed culvert, excess puddling on the road surface). Sumps had the highest rate of problems, with 11
of 24 (46%), followed by ditch relief culverts (155 of 392, 40%). Fill erosion was recorded at 83 drain points (2%), with a total volume of 85 m 3 (3000 ft 3 ). Fill erosion was most common at non

- engineered
drains with 28 instances and 23 m 3 (820 ft 3 ). Stream cro ssings had 44 m 3 (1550 ft 3 ) eroded from 4 of 146 crossings (2%). It was estimated that fill erosion delivered 87 Mg of sediment to the stream channel, or about a quarter of the rate of the of road surface sediment over 20 years (4.4 Mg/yr). It would take

a bout four years for the fine sediment delivery from road surfaces to equal the total mass of delivered
sediment from fill erosion

.



### Poorman Creek Summary

In the Poorman Creek area, there were 174 km (108 mi) of road and 2190 drain points surveyed. Table B presents a summary of the findings for this project area. Hydrologic connectivity was found to be a relatively low 4.7% of all road length at 8 km out of 174 km (5 mi out of 106 mi). The model predicted 11.5 Mg/yr of delivered road surface fine sediment to stream channels, which is 4.6% of the 247 Mg generated annually by the road surface. This sediment was delivered through 97 of 2190 (4%) drain points. There was 5.6 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 49% of all

sedim ent delivery and 77% of all sediment produced within 10 m of a stream crossing.

Specific sediment due to road surface

- related sediment for the whole Poorman Creek area was 0.11 Mg/km 2 /yr, or 1% of the observed total average fine sediment yield for five nearby areas as determined by reservoir coring or suspended sediment extrapolations. Including sediment delivered to streams through other sources (landslides, gullies, and fill erosion at drain points), the specific sediment for the Table 38

. Summary of GRAIP

- predicted road risk predictions, Poorman Creek area.

Impact/Risk Type GRAIP Predicted Risks

Road

- Stream Hydrologic Connect ivity 4.7% of road length, 8 km; 4% of drain points connected

Fine Sediment Delivery 4.6% of sediment produced, 11.5 Mg/yr

Sediment in Streams 0.19 Mg/km 2 /yr; 2% of average sediment yield for nearby areas

Landslide Risk Estimated 91 Mg of sediment deliv ered to streams, 2.2% of watershed area with possible elevated risk due to roads

Gully Risk Estimated 0.2 Mg/yr of sediment delivered to streams, too few gullies to determine ESI crit

Stream Crossing Risks

- plug potential 5 sites (17%) with elev ated risk (SBI > 2)

- fill at risk 1399 m 3 fill at risk, average of 48 m 3 per crossing

- diversion potential 8 sites (1 7 %) with diversion potential

Drain Point Problems 270 drain points (12% of all drain points) with problems, 11 m 3 of
fill erosion (1% of drain points), estimated 0.2 Mg/yr of fill erosion

delivered to streamsSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

98 whole project are a was 0.19 Mg/km 2 /yr, or about 2% of the observed average fine sediment yield for the nearby areas. The most heavily impacted stream reaches had road sediment delivery values as high as 0.8 Mg/km 2 /yr with only road surface fine sediment, or 4.0 Mg/km 2 /yr i ncluding mass wasting
sediment.

There were 5 landslides observed by field crews in the course of the inventory, with a total volume of

252 m 3 (329 yd 3 ). All were road related. It was conservatively estimated that 91 Mg of landslide derived
sediment has be en delivered to streams, which is roughly half the rate of sediment from road surfaces over 20 years (4.5 Mg/yr). It would take about 8 years for the fine sediment delivery from road surfaces to equal the total mass of delivered sediment from landslides. C alibrated stability index modeling with SINMAP conservatively showed that 3 km 2 (1 mi 2 ), or 2%, of the watershed area was put at higher risk of shallow landslide initiation by road drainage.

Gullies were observed at 7 locations by field crews, totaling 15 7 m 3 (206 yd 3 ) in volume, with none occurring in wet swales. It was estimated that these gullies delivered 4 Mg of sediment to the stream channel, which is negligible compared to the rate of road surfaces over 20 years (0.2 Mg/yr). It would
take less than one year for the fine sediment delivery from road surfaces to equal the total mass of
delivered sediment from gullies

. There were too few gullies to determine an ESI crit , suggesting that the gully initiation risks here may be very low. The average ESI acro ss the Poorman Creek area was 8.

There were 29 stream crossings with culverts (as opposed to bridges or fords) recorded. The average blocking index (SBI) for these points was a moderate to low 1.7. There were 5 crossings with an elevated
SBI of 3. No cro ssings had an SBI of 4, which is the highest possible value. The total calculated volume of fill at risk in an overtopping type event was 1399 m 3 (1830 yd 3 ). There were eight stream crossings with the potential to divert stream flow down the road and onto unchanneled hillslopes. There was one stream crossing with an SBI of 3 and diversion potential . There was a total of 21 m 3 (27 yd 3 ) of fill at risk at this point. Two natural ford type crossings were observed to divert flow down the road, though no major e rosion was observed at the time of the survey.

Of the 2190 recorded drain points, 270 (12%) had one or more problem of some type (e.g. blocked or crushed culvert, excess puddling on the road surface). Ditch relief culverts had the highest rate of problems , with 18 of 56 (32%), followed by broad based dips (120 of 412, 29%). Fill erosion was recorded at 22 drain points (1%), with a total volume of 11 m 3 (400 ft 3 ). Fill erosion was most common at

non

- engineered drains with 16 instances and 8 m 3 (300 ft 3 ). It was estimated that fill erosion delivered 3 Mg of sediment to the stream channel, which is negligible compared the amount of road surface sediment over 20 years (0.2 Mg/yr).



### Cold Creek Summary

In the Cold Creek area, there were 198 km ( 123 mi) of road an d 3584 drain points surveyed. Table 39 presents a summary of the findings for this project area. Hydrologic connectivity wa s found to be a relatively low 4 % of all road length at 9 km out of 198 km ( 6 mi out of 123 mi). The model predicted 9 .8 Mg/yr of del ivered road surface fine sediment to stream channels, which is 6 % of the 162 Mg generated annually by the road surface. This sediment was delivered through 205 of 3584 ( 6 %) drain points. There

was 6.6 Mg/yr of delivery that occurred within 10 m of a stream crossing. This is 67 % of all sediment delivery and 75 % of all sediment produced within 10 m of a stream crossing.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

99 Specific sediment due to road surface

- related sediment for the whole Cold Creek area was 0. 1 Mg/km 2 /yr, or 1 % of the observed total average fine sediment yield for five nearby areas as determined by reservoir coring or suspended sediment extrapolations. No other sources were observed to deliver
sediment to streams

. The most heavily impacted stream reaches had road sediment delivery values as
h igh as 1.1 Mg/km 2 /yr.
There were 9 landslides observed by field crews in the course of the inventory, with a total volume of

175 m 3 ( 2 29 yd 3 ). Only one landslide was not road related. No landslide sediment was observed to have
been delivere d to streams. Ca librated stability index modeling with SINMAP conservatively showed that

0.6 km 2 ( 0.2 mi 2 ), or 0.6 %, of the watershed area was put at higher risk of shallow landslide initiation by road drainage.

Table 39

. Summary of GRAIP

- predicte d road risk predictions, Cold Creek area.

Impact/Risk Type GRAIP Predicted Risks

Road

- Stream Hydrologic Connectivity 4% of road length, 9 km; 6% of drain points connected

Fine Sediment Delivery 4% of sediment produced, 9.8 Mg/yr

Sediment in Streams 0. 10 Mg/km2/yr; 1% of average sediment yield for nearby areas

Landslide Risk No landslide sediment delivered to streams; 0.6% of watershed area with possible elevated risk due to roads

Gully Risk No gully sediment delivered to streams, too few gullies to
d etermine ESI crit Stream Crossing Risks

- plug potential 28 sites (39%) with elevated risk (SBI ≥ 2)

- fill at risk 2095 m 3 fill at risk, average of 31 m 3 per crossing

- diversion potential 39 (34%) sites with diversion potential

Drain Point Problems 284 drain point s (8% of all drain points) with problems, 3 m 3 of fill erosion (1% of drain points), estimated 0.005 Mg/yr of fill erosion

delivered to streams

Gullies were observed at 3 locations by field crews, totaling 5 m 3 (7 yd 3 ) in volume, with none occurring in wet swales. No gullies were observed to de liver sediment to the stream channel in Cold Creek. There were too few gullies to determine an ESI crit , suggesting that the gully initiation risks here may be very
low. The average ESI across the Cold Creek area was 4

.

There were 71 stream crossings with culverts (as opposed to bridges or fords) recorded. The average blocking index (SBI) for these points was a moderate to low 2.3 . There were 26 crossings with an
elevated SBI of 3. Two crossings had an SBI of 4, which is the highest possible value. The tota l calculated volume of fill at risk in an overtopping type event was 2090 m 3 ( 2730 yd 3 ). There were 39 stream crossings with the potential to divert stream flow from a plugged culvert down the road and onto unchanneled hillslopes. There were 14 crossings w ith an SBI of 3 or 4 and diversion potential. There was
a total of 332 m 3 (434 yd 3 ) of fill at risk at these point s

. Of those 14 crossings, half received the stream flow from the ditch, though this appeared to be intentional.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

100 Of the 3584 recorded drain po ints, 2 84 (8 %) had one or more problem of some type (e.g. blocked or crushed culvert, excess puddling on the road surface). Stream crossings had the highest rate of problems, with 45 of 115 ( 39 %), followed by ditch relief culverts ( 80 of 266

, 30 %). Fill er osion was
recorded at 23 drain points (1%), with a total volume of 3 m 3 ( 110 ft 3 ). Fill erosion was most common at broad based dips with 1 8 instances and 3 m 3 ( 90 ft 3 ). It was estimated that fill erosion delivered 0.5 Mg of sediment to the stream channel, which is negligible compared the amount of road surface sediment over 20 years ( 0.005 Mg/yr).



### Jammer Roads Summary

Two complete jammer road complexes totaling 1 9 km (11 mi) of road and 325 drain points in the Center Horse project area were inventoried usi ng the GRAIP method. These vegetated and shallow

- slope roads delivered 0.02 Mg/yr, which is 2% of the 1 Mg/yr generated on the road surfaces ( Table 40 )

. If this delivery rate is applied to all jammer roads, then it can be expected that these roads deliver less than 1 Mg/yr from the road surface. A a small stream diversion was observed that resulted in two delivering gullies (29 Mg) and two non

- engineered points with fill erosion, one of w hich delivered to the stream (23 Mg). There were no other observed ins tances of mass wasting, including anything not related to the

stream crossing or any landslides.

Table 40

. Summary of observed and predicted jammer road risks.

Impact/Risk Type Predicted Risks

Complete Complex Inventory

Fin e Sediment Delivery 2% of sediment produced; 0.02 Mg/yr

Estimated Sediment Delivery for All Jammer
Roads 0.4 Mg/yr, using a delivery rate of 0.001 Mg/yr/km

Gullies and Fill Erosion
Risks 29 Mg delivered to streams from gullies, 23 Mg delivered to

str eams from fill erosion, estimated 3 Mg/yr

Stream Crossing Survey Fill Erosion Risks,
Observed 44% of stream crossings with fill erosion, estimated 17 Mg/yr

delivered to streams

Fill Erosion Risks, Future
Estimated 25% of estimated risk has been re alized, up to 75% (600 m 3 ) may remain

Other Problems 9 crossings (13%) with observed stream diversions or other problems

W e conducted a census of all of the stream crossings on jammer roads in the Center Horse and Morrell/Trail project area, for a tot al of 71 crossings. Streams were defined as continuous features with a bed, banks, and evidence of flow for some part of most years. There were 61 natural ford

- type crossings (no infrastructure) and ten crossings with culverts. Nine crossings (13%) were ob served to have evidence of stream diversion or other problems. There were 31 crossings (44%) with fill erosion,Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

101 totaling 2 07 m 3 (7300 ft 3 ), all of which was assumed to deliver (331 Mg)

. This was roughly equivalent to
that from road surfaces on non

- jammer r oads in the Center Horse and Morrell/Trail project area over 20 years (17 Mg/yr ).

The average volume of fill available to erode at each crossing was estimated to be 12 m 3 (16 yd 3 ) per crossing. Of this amount, an average of 3 m 3 (4 yd 3 ) per crossing has a lready been eroded, suggesting
that 25% of possible erosion has already occurred, and up to 75% remains (about 600 m 3 or 22,000 ft 3 )

. Differences in the shape and construction of each stream crossing, and the timing of high flows and transport capacity of the streams

, suggest that each stream crossing will respond at a different rate, and may include some deposition. I t was found that on hillslopes of greater than about 40%, every stream crossing in the Center Horse area had fill erosion, suggesting that th e stream crossings on steeper slopes may be at higher risk of failure than those on lower slopes.



### Conclusions

Under the observed conditions, the GRAIP inventories in the Southwest Crown of the Continent suggest
low risk across the measured metrics when co nsidered at the watershed scale. The Center Horse and Morrell/Trail project area had the most risk overall. There are two other non

- watershed GRAIP sites in the northern Rockies; one site in the Clearwater National Forest ( Cissel et al. 2011A ), and one in the Gallatin National Forest ( Cissel et al. 2011B ) . Compared to these sites, the se three watershed s fall within the typical range for landslide risk, gully risk, stream crossing plugging potential and diversion potential, and drain point problems and fill erosion for both sites. The stream crossing fill at risk is slightly higher in the Center Horse and Morrell/Trail project area and Poorman Creek, but within the typical range in Col d
Creek . The Clearwater site had much higher road surface sediment delivery and hydrologic connectivity, while this data is in range of the Gallatin site. Compared to a site in the Olympic National Forest in western Washington ( Cissel et al. 2011C ), which is considered to have high risk in all metrics, the Center
Horse and Morrel l/Trail project area has low to mo derately low risk in all areas.

Although sediment delivery risk related to roads is low from the watershed perspective, several road segments were identified that may need treatment to minimize sediment delivery effects t hat are significant at the stream reach scale. Depending on downstream habitat and species presence, fine sediment delivery effects may be significant at a stream reach scale. Ongoing work comparing aquatic habitat conditions between managed and unmanaged reaches using PIBO data will help refine these questions.

Road maintenance level appears to have a small to moderate effect on the various risk metrics. Higher maintenance levels (ML 3 and 4; more traffic, more frequent and more intense maintenance) had

s omewhat more sediment delivered from their road surfaces, but mass wasting risks were lower. Lower maintenance level roads ( ML 1 and 2; little to no traffic, little to no maintenance) had higher mass wasting risks. These relationships suggest that traffic has an important effect on road surface fine sediment production, but regular more intense maintenance can prevent mass wasting problems. On
some lower maintenance level roads, it may be beneficial to treat spots that are at high risk of erosion.

The sedi ment delivery from fill erosion and mass wasting at jammer road

- stream intersections in the Center Horse and Morrell/Trail project area was on the same scale as the road surface fine sediment delivery from non

- jammer roads in the same area. The highly vege tated and low slope ja mmer road
surfaces themselves did not appear to have significant impacts. Treatments to jammer roads should beSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

102 focused on the roads with stream crossings. However, t he consequences of removing vegetation on the
road surface to access the jammer road stream crossings may increase the contributions of their surface
fine sediment to streams

. Data to be collected in the summer of 2014 may help to further understand the causes and distribution of erosion at stream crossings on jammer roads.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

103 

## References

Best, D. W., Kelsey, H. M., Hagans, D.K. and Alpert, M. 1995. Role of fluvial hillslope erosion and road construction in the sediment budget of Garret Creek, Humboldt County, California. In Geomorphic Process and Aquatic Habitat in the Redw ood Creek Basin, Northwestern California. Nolan, K. M., Kelsey, H. M., and Marron, D. C. editors. USGS professional paper #1454. pp: m1

- m9.

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.

Black, T. A. and Luce, C. H. 2013. Measuring Water and Sediment Discharge from a Road Plot with a Settling Basin and Tipping Bucket. Gen. Tech. Rep. RMRS

- GTR

- 287. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Cissel, R. M., Black, T. B., and Luce, C. H. 2011A. Legacy Roads and Trail Monitoring Proj ect, Road Decommissioning in the Lolo Creek Watershed, Clearwater National Forest. USDA Forest Service Rocky Mountain Research Station, Boise Aquatic Science Lab.

Cissel, R. M., Black, T. B., and Luce, C. H. 2011B. Legacy Roads and Trail Monitoring Projec t, Road Decommissioning in the Mill Creek Watershed, Gallatin National Forest. USDA Forest Service Rocky Mountain Research Station, Boise Aquatic Science Lab.

Cissel, R., Black, T., Luce, C., and Staab, B. 2011C. Legacy Roads and Trails Monitoring Project , Storm Damage Risk Reduction in the Skokomish River Watershed, Olympic National Forest. USDA Forest Service Rocky Mountain Research Station, Boise Aquatic Science Lab.

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. 2012A. 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.

Flanagan, S. A., Furniss, M. J., Theisen, S., Love, M., Moore, K., and Ory, J. 1998. Methods for Inventory and Environmental Risk Assessment of Road Drainage Crossings. USDA Forest Service Technology and Development Program 9877

- 1809

- SDTDC 45pp

Fly, C.M., Grover

- Weir, K., Thornton, J., Black, T.A., and Luce, C.M. 2010. Bear Valley Road Inventory (GRAIP) Report; Bear Valley Category 4b Assessment, Boise National Forest. USDA Forest Service,
Boise National Forest.

Furniss, M. J ., Love, M., and Fla nagan, S. A . 1997. Diversion Potential at Road Stream Crossings. USDA Forest Service Technology and Development Program 9777

- 1814

- SDTDC 12pp.

Hofmann, M. H., Hendrix, M. S., Moore, J. N., and Sperazza , M. 2006. Late Pleistocene His t or y of
Sediments in Fla thead Lake, MT: Evidence from High

- resolution Seismic Reflection Interpretation. Sedimentary Geology. Vol. 184, pp:111

- 131.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

104 Istanbulluoglu, E., Tarboton, D.G., Pack, R.T., and Luce, C.H. 2003. A sediment transport model for incision of gullies on steep to pography. Water Resources Research. Vol. 39, No. 4, pp: 1103

- 1117.

Jones, J. A., and Grant, G. E. 1996. Peak flow responses to clear

- cutting and roads in small and large basins, western Cascades, Oregon, Water Resour. Res. Vol. 32, pp: 959

- 974.

Kirchner , J. W., Finkel, R. C., Riebe, C. S., Granger, D. E., Clayton, J. L., King, J. G., and Megahan, W. F. 2001. Mountain Erosion Over 10 yr, 10 ky, and 10 my Time Scales. Geology. Vol. 29, No. 7, pp:591

- 594.

Lambing, J. H., and Sando, S. K. 2008. Estimated Lo ads of Suspended Sediment and Selected Trace Elements Transported through Milltown Reservoir in the Upper Clark Fork Basin, Montana, Water

Years 2004

- 07. U.S. Geological Survey Scientific Investigations Report 2008

- 5080.

Lolo National Forest Soil and Wate r Program. 2009. Unpublished stream gage data from the North Fork Blackfoot River located at 47.103N,

- 112.961W. Missoula, MT.

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.

Ludington, S., Moring, B. C., Miller, R.J., Flynn, K.S., and Hopkins, M. J. 2005. Western States Geology shapefiles. Accessed online in 2009 from http://pubs.usgs.gov/of/2005/1305.

Madej, M. A. 2001. Erosion and Sediment Delivery Follow ing Removal of Forest Roads, Earth Surface Landforms and Processes, Vol. 26, No. 2, pp: 175

- 190.

Megahan, W.F. 1976. Tables for geometry for low

- standard roads for watershed manag ement considerations, slope sta king, and end areas. Gen. Tech. Rep. INT

- 32. U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station.

Moll, J. 1997. Glossary of Water/Road Interaction Terminology for Water/Road Interaction Technology Series. USDA Forest Service Technology and Development P rogram 9777

- 1806

- SDTDC 14pp.

Montana Department of Environmental Quality. 2008. Middle Blackfoot

- Nevada Creek Total Maximum Daily Loads and Water Quality Improvement Plan. Accessed online April 18 th , 2013 from http://www.deq.mt.gov/wqinfo/tmdl/finalreport s.mcpx.

Montana Department of Environmental Quality. 2011. Montana Average Annual Precipitation 1981

– 2010 shapefiles. Accessed online April 4, 2013 from http://nris.mt.gov/nsdi/nris/mdb/mt_1981

- 2010_AveAnnPrecip.zip.

Pack, R. T., Tarboton, D.G., Goodwi n, C.N. and Prasad, A.. 2005. SINMAP 2. A Stability Index Approach to Terrain Stability Hazard Mapping, technical description and user ’ s guide for version 2.0, Utah State University.

Prasad, A. 2007. A tool to analyze environmental impacts of road on fore st watersheds. MS Thesis. Utah State University, USA.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

105 Sugden, B. D. and S. W.Woods 2007. Sediment production from forest roads in Western Montana.
Journal of the American Water Resources Association . Vol. 43 , No. 1

, pp: 193

- 206

.

U.S. Department of Agr iculture. 1978. Sediment Deposition in U.S. Reservoirs: Summary of Data Reported Through 1975. Miscellaneous Publication Number 1362. Compiled by F. E. Dendy and W. A. Champion. Agricultural Research Service, USDA Sedimentation Laboratory, Oxford, MS.

U.S . Geological Survey. 2012. National Water Information System data available on the World Wide Web (USGS Water Data for the Nation) for USGS Station 12340000 Blackfoot at Bonner. Accessed April, 2013, at URL http://waterdata.usgs.gov/nwis/.

Wemple, B. C., Jones, J. A., and Grant, G. E. 1996. Channel network extension by logging roads in two basins, western Cascades, Oregon, Water Resources Bulletin. Vol. 32, pp: 1195

- 1207.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

106 

## Appendix A: Road R isks by Maintenance Level Table Road risk table for all three project areas, broken out by road maintenance level. There were not enough gullies or landslide s in Poo rman Creek or Cold Creek t o

perform this analysis, so they are omitted. See section 4.8 for more information.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

107 

## Appendix B : Glossary of Selected Terms

Below is a list of terms, mostly of drainage point types, but also of some other commonly used terms, for the purpose of clarification. Adapted from Black, et al. (2012), Fly, et al (2010), and Moll (1997).

Broad based dip. Constructed: Gr ade reversal designed into the road for the purpose of draining water from the road surface or ditch (also called dip, sag, rolling grade, rolling dip, roll and go, drainage dip, grade dip). Natural: A broad based dip point is collected at the low point wh ere two hillslopes meet, generally in a natural swale or valley. This is a natural low point in the road that would cause water on the surface of the road to drain out of the road prism.
Cross drain. This is not a feature collected specifically in GRAIP, and it can refer to a number of other drainage features. It is characterized by any structure that is designed to capture and remove water from the road surface or ditch. Ditch relief culverts, waterbars, and broad based dips can all be called
cross drains

. Diffuse drain. This is a point that is characterized by a road segment that does not exhibit concentrated flow off the road. Outsloped roads or crowned roads often drain half or all of the surface 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. A drop of water that lands on a diffuse road segment will not flow down the road or into the ditch, b ut more or less perpendicular to the centerline off the road surface and out of the road prism. Also called sheet drainage or inter

- rill flow.
Ditch relief culvert. This drain point is characterized by a conduit under the road surface, generally
made of me tal, cement, or wood, for the purpose of removing ditch water from the road prism. This feature drains water from the ditch or inboard side of the road, and not from a continuous stream
channel. Flow path. This is the course flowing water takes, or would t ake if present, within the road prism. It is where water is being concentrated and flowing along the road from the place where it enters the road prism, to where it leaves the road prism. This can be either on the road surface, or in the ditch.
Lead off di tch. This drain point is characterized by a ditch that moves flow from the roadside ditch and leads it onto the hillslope. Occurs most often on sharp curves where the cutslope switches from one side of the road to the other. Also known as a daylight ditch, mitre drain, or a ditch out (though this term can also describe other types of drainage features). Mg, megagrams. This unit is equivalent to 1 metric tonne, 1000 kg, and 1,000,000 g. Equivalent to 2204 lbs, and 10% larger than 1 U.S. short ton (2000 lbs)

. Non

- engineered drainage. This drain point describes any drainage feature where water leaves the road surface in an unplanned manner. This can occur where a ditch is dammed by debris, and the water from the ditch flows across the road, where a gully crosse s the road, where a wheel rut flow path is diverted off the road due to a slight change in road grade, or where a berm is broken and water flows through. This is different from a diffuse drain point, which describes a long section of road that sheds water without the water concentrating, whereas this point describes a single point where a concentrated flow path leaves the road. Orphan drain point. This is any drain point that does not drain any water from the road at the time of data collection. Examples in clude a buried ditch relief culvert, or a water bar that has been installed on a road that drains diffusely. Stream crossing. This drain point is characterized by a stream channel that intersects the road. This feature may drain water from the ditch or roa d surface, but its primary purpose is to route stream water under or over the road via a culvert, bridge, or ford. A stream for the purposes of GRAIP has an armoredSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

108 channel at least one foot wide with defined bed and banks that is continuous above and belo w the road and shows evidence of flow for at least some part of most years. Sump. Intentional: A closed depression where water is intentionally sent to infiltrate. Unintentional: Any place where road water enters and infiltrates, such as a cattle guard wit h no outlet, or a low point
on a flat road.
Waterbar. This drain point is characterized by any linear feature that is perpendicular to the road that drains water from the road surface and/or ditch out of the road prism or into the ditch. Waterbars may

be c onstructed by dipping the grader blade for a short segment, or adding a partly buried log or rubber belt across the road. Some road closure features may also act as a waterbar, such as a tank trap (also known as a closure berm or Kelly hump). Cattle guards that have an outlet that allows water to flow out are also considered to be water bars. These features may also be known as scratch ditches if they drain
water into the ditch.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

109 

## Appendix C : GRAIP Data Management Plan

Project Title: A new model of water shed

- scale aquatic monitoring from the Crown of the Continent: Quantifying the benefits of watershed restoration in the face of climate change

Data Input

- New Collection

1 General Description Road Inventory data and output from the Geomorphic Road Analys is and Inventory Package (GRAIP) Budget

Format Grids, and shapefiles Data Processing & Scientific
Workflow See The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 1 Data Collection Method and Volume 2: Office Procedures. Rocky Mountain

R esearch Station General Technical Report RMRS

GTR

- 280WWW http://www.treesearch.fs.fed.us/pubs/40654 and

281WWW http://www.treesearch.fs.fed.us/pubs/40655

Protocols See The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 1 Data Collection Met hod and Volume 2: Office Procedures. Rocky Mountain Research Station General Technical Report RMRS

GTR

- 280WWW and 281WWW Backup and Storage The original input data were copied to a local PC at RMRS Boise and backed up on second hard

- drive
and a local ser ver. QA/QC See field and office manuals above

Metadata With each output file

Volume Estimate 2 GB Archive Orgs Final data to be archived on DVD at RMRS Boise and sent to GNLCC web portal for archiving. Access and Sharing Data will be shared with pa rtners and cooperators as it is collected, analyzed, and published.

Exclusive Use We request a maximum of a two year extension following the conclusion of the funding period to write manuscripts and publish our results. During
this time data will be share d with cooperators and upon request with non

- project related researchers and data and project managers. After the extension period, no restrictions to the data

access.Southwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

110 Restrictions We do not anticipate restrictive use of the data after publication. Prop er reference to source required.

Citation TBD

TBD NA

Contact Tom Black USD A Forest Service Rocky Mountain Research Station, Boise. tblack@fs.fed,us



### Data Inputs

1 Elevation data (DEM) Description 30 meter DEM

Format Raster Data

- Grid

Data Processin g & Scientific
Workflow Use as acquired, resampled to 5 meter using bilinear resampling

Source National Elevation Dataset (NED)

Protocols See The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 2: Office Procedures. Rocky Mountain Researc h Station General Technical Report RMRS

- GTR

- 281WWW Backup and Storage The original input data were copied to a local PC at RMRS Boise and backed up on second hard

- drive
and a local server.

Volume Estimate 50 MB Access and Sharing Free

Restrictions Unrestricted use

2 GRAIP Road Inventory Field Data Description A GPS referenced field inventory documenting the hydrology and geomorphology of the road
network

Format ArcGIS 9.3 shapefiles Data Processing & Scientific
Workflow These files have been e xported from the GPS device, differentially corrected in Pathfinder Office, edited to minimize GPS errors in road alignment and combined and exported as shapefiles. See The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 1 Data
Collection Me thod and Volume 2: Office Procedures. Rocky Mountain Research Station General Technical Report RMRS

- GTR

- 280WWWSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

111 and 281WWW

Protocols Data is collected following the protocol in the field manual by persons receiving a two week intensive training course tea ching the material in the Field manual, (see above). Backup and Storage The original input data were exported from field devices to a field laptop. Files are then copied to a PC at RMRS Boise and backed up on second hard

drive and a local server. QA/Q C Field and Office QA/QC documented in the manuals, see above

Metadata With each file and directory

Volume Estimate 5

- 20 MB



### Data Outputs

1 GRAIP Model Output Shapefiles Description Road line, Drain point and stream shapefiles that
contain observed and modeled sediment production, delivery and other geomorphic and hydrologic attribute data.

Format ArcGIS 9.3 shapefiles Data Processing & Scientific
Workflow See office manuals

Protocols See office manuals Backup and Storage Files are produced on a PC at RMRS Boise and backed up on second hard

- drive and a local server. QA/QC See office manuals

Metadata Associated with each file and directory

Volume Estimate 10

- 50 MB Archive Orgs Final data to be archived on DVD at RMRS Boise
and sent to GNLCC web portal for archiving. Access and Sharing Data will be shared with partners and cooperators as it is collected, analyzed, and published.

Exclusive Use We request a maximum of a two year extension following the conclusion of the funding period to

write ma nuscripts and publish our results. During this time data will be shared with cooperators and upon request with non

- project related researchers and data and project managers. After the extension period, no restrictions to the data

access.
Restrictions We do not anticipate restrictive use of the data after publication. Proper reference to source required.

Citation TBDSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

112 Digital Object Identified (DOI) Link TBD

Contact Tom Black USD A Forest Service Rocky Mountain Research Station, Boise. tblack@fs.fed,us

2 GRAIP Model Intermediate and Output GRIDS Description GRAIP uses various grids created by the programs
TauDEM to route sediment and create a channel network. The program SinMap makes slope stability predictions from the DEM. These grids
are called on and updated by GRAIP.

Format ArcGIS 9.3 grids Data Processing & Scientific
Workflow See office manuals

Protocols See office manuals Backup and Storage Files are produced on a PC at RMRS Boise and backed up on second hard

- drive and a local server. QA/QC See office manuals

Metadata Associated with each directory and in the office
manual

Volume Estimate 20

- 50 MB Archive Orgs Final data to be archived on DVD at RMRS Boise and sent to GNLCC web portal for archiving. Access and Sharing Data will be s hared with partners and cooperators as it is collected, analyzed, and published.

Exclusive Use We request a maximum of a two year extension following the conclusion of the funding period to write manuscripts and publish our results. During
this time data will be shared with cooperators and upon request with non

- project related researchers and data and project managers. After the extension period, no restrictions to the data

access.
Restrictions We do not anticipate restrictive use of the data after publi cation. Proper reference to source required.

Citation TBD Digital Object Identified (DOI) Link TBD

Contact Tom Black USD A Forest Service Rocky Mountain Research Station, Boise. tblack@fs.fed,us



### Software

1 GRAIP Description GRAIP is a free software package that runs as anSouthwest Crown of the Continent GRAIP Watersh eds Roads Assessment Blackfoot and Swan River Watersheds; Lolo, Helena, and Flathead National Forests; Montana

113 extension in ArcGIS 9.3 (at present). It performs
the calculations of road sediment and routes the sediment to streams in addition to calculating a variety of road hydro

- geomorphic risk metrics.

Restrictions This software is in th e public domain.

Fees Free Source/Link http://www.neng.usu.edu/cee/faculty/dtarb/graip/

2 TauDEM Description TauDEM is a tool that runs in Arc GIS to calculate hydrologic attributes of a landscape using a DEM

Restrictions This software is in the pu blic domain.

Fees Free Source/Link http://www.neng.usu.edu/cee/faculty/dtarb/graip/

3 SINMAP 2.0 Description GRAIP

Restrictions This software is in the public domain.

Fees Free Source/Link http://www.neng.usu.edu/cee/faculty/dtarb/graip/

4 ArcG IS 9.3 Description Geographic Information System Software

Restrictions This software is available for purchase form ESRI

Fees TBD Source/Link http://www .ESRI.com