Lights Creek and Indian Creek Plumas National Forest, California
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Moonlight Fire GRAIP Watershed Roads Assessment Lights Creek and Indian Creek Plumas National Forest, California July, 2015 Natalie Cabrera1, Richard Cissel2, Tom Black2, and Charlie Luce3 1Hydrologic Technician 2Hydrologist 3Research Hydrologist U.S. Forest Service Rocky Mountain Research Station 322 E. Front St, Suite 401 Boise, ID 83702 Moonlight Fire GRAIP Watershed Roads Assessment Lights Creek and Indian Creek, Plumas National Forest, California Table of Contents Acknowledgments........................................................................................................................... 5 Executive Summary ......................................................................................................................... 6 1.0 Background ........................................................................................................................ 10 2.0 Objectives and Methods .................................................................................................... 12 3.0 Study Area .......................................................................................................................... 15 4.0 Results ................................................................................................................................ 26 4.1 Road-Stream Hydrologic Connectivity ........................................................................... 26 4.2 Fine Sediment Production and Delivery ......................................................................... 30 4.3 Downstream Sediment Accumulation ........................................................................... 35 4.4 Landslide Risk ................................................................................................................ 40 Existing Landslides ................................................................................................................ 40 Changes to Landslide Risk Due to Roads .............................................................................. 45 4.5 Gullies and Gully Initiation Risk ...................................................................................... 51 Existing Gullies ...................................................................................................................... 51 Gully Initiation Risk ............................................................................................................... 54 4.6 Stream Crossing Failure Risk .......................................................................................... 58 4.7 Drain Point Condition and Fill Erosion ........................................................................... 62 5.0 Comparison to Other Studies ............................................................................................ 67 6.0 Summary and Conclusions ................................................................................................. 71 References .................................................................................................................................... 78 Appendix A: Glossary of Selected Terms ...................................................................................... 83 Appendix B: Additional Maps ....................................................................................................... 85 -2- Moonlight Fire GRAIP Watershed Roads Assessment Lights Creek and Indian Creek, Plumas National Forest, California List of Figures Figure 1. Location of watershed inventories and Legacy Roads Monitoring Project ................... 16 Figure 2. Photo showing red oxidized soil with lack of vegetation from severe. ......................... 18 Figure 3. Close up of same area in Figure 2. Note gullying is active in these bare areas. ............ 18 Figure 4. Study area showing Lights Creek and Indian Creek watersheds, major ....................... 19 Figure 5. Geology of the Lights Creek and Indian Creek watersheds. .......................................... 21 Figure 6. Elevation and location of inventoried roads within the Lights Creek and. ................... 24 Figure 7. Land ownership and all roads within the Lights Creek and Indian Creek. .................... 25 Figure 8. Cutslope rills and road surface gullies that increased and expanded ........................... 27 Figure 9. Road segments within 50 feet of stream channels in the east central ......................... 27 Figure 10. There is a higher probability of stream connection at the same drain ....................... 29 Figure 11. Probability of stream connection decreased with increasing drain point. ................. 29 Figure 12. Sediment production and delivery by drain point. ..................................................... 31 Figure 13. Fine sediment delivery to channels by road segment and drain point. ...................... 32 Figure 14. Percent total sediment delivered to streams by percent of drain. ............................. 32 Figure 15. Normalized sediment production and delivery by road surface condition. ............... 34 Figure 16. Sediment accumulation from roads to streams in the Lights Creek Watershed. ....... 38 Figure 17. Specific sediment from roads to streams in the Lights Creek Watershed. ................. 39 Figure 18. Cutslope failure type landslide in earthflow terrain. .................................................. 42 Figure 19. Fillslope failure type landslides in earthflow terrain. .................................................. 42 Figure 20. Locations of observed landslides interacting with the road prism in ......................... 43 Figure 21. GRAIP observed landslides interacting with the road prism within ............................ 44 Figure 22. SINMAP generated calibration graph. Points that lie to the right of the .................... 45 Figure 23. Natural slope stability in the south central portion of the Lights Creek ..................... 46 Figure 24. The most significant slope stability risk changes due to the roads in the................... 47 Figure 25. Changes in slope stability risk in the south central portion of the Lights ................... 48 Figure 26. Areas of naturally high risk and risk changes, south central portion of the ............... 49 Figure 27. Gully below the outlet of a ditch relief culvert............................................................ 52 Figure 28. Locations of observed gullies and ESI risk at drain points, in southeast ..................... 53 Figure 29. Length-slope plot that shows the distribution of gullied and non-gullied .................. 55 Figure 30. Calibration graph from the R local fit calibration. Gully probability is a ..................... 55 Figure 31. SBI values for the stream crossings in the northeastern part of the Lights ................ 58 Figure 32. Distribution of SBI values for the Lights Creek and Indian Creek watersheds. ........... 59 Figure 33. The stream crossings with the highest risk of plugging and the most. ....................... 61 Figure 34. Number of problems by drain point type in the Lights Creek and .............................. 64 Figure 35. Locations of problems by drain point type in the southeast portion. ........................ 65 Figure 36. Problems with ditch relief culverts. The left culvert is rusted through....................... 66 -3- Moonlight Fire GRAIP Watershed Roads Assessment Lights Creek and Indian Creek, Plumas National Forest, California List of Tables Table 1. Summary of effective road lengths by drain point type. Sumps. .................................... 28 Table 2. Summary of sediment production and delivery at drain points. .................................... 31 Table 3. Sediment production and delivery by surface type (top), and normalized ..................... 33 Table 4. Study area streams and sediment accumulation and specific sediment ........................ 37 Table 5. Number and types of observed landslides, as well as masses and ................................. 40 Table 6. Landslide risk changes in the Lights Creek and Indian Creek watersheds ...................... 49 Table 7. Inventoried gullies in the Lights Creek and Indian Creek watersheds ............................ 51 Table 8. Sediment masses produced and delivered by active gullies in the Lights Creek ............ 52 Table 9. Active road surface gullies, production and delivery to streams, Lights Creek .............. 53 Table 10. Distribution of drain points by ESI value, Lights Creek and Indian Creek ..................... 54 Table 11. Further distribution information of drain points by ESI value. ..................................... 56 Table 12 .Maximum contributing road segment length for a given average hillslope ................ 57 Table 13. Drain point condition problems and fill erosion below drain points, Lights Creek ....... 62 Table 14. Fill erosion below drain points, volumes and masses, Lights Creek and Indian ........... 63 -4- Moonlight Fire GRAIP Watershed Roads Assessment Lights Creek and Indian Creek, Plumas National Forest, California Acknowledgments We would like to thank the field crew members Casey Delay, Travis Dickinson, Logan Fusso, Jessica Jamsgard, Jonathan O’Connell, Austin Maphis, Orion Moonie, and Henry Ross for carefully and diligently collecting these data. We would also like to thank the Mt. Hough Ranger District, Plumas National Forest for providing equipment, office space, logistical support, vehicles and bunkhouse space. Thanks to Plumas Fire Engine 22 Captain Tommy Brenzovich