THESIS

SEDIMENT PRODUCTION AND DELIVERY FROM HILLSLOPES AND FOREST ROADS IN THE SOUTHERN SIERRA NEVADA, CALIFORNIA

Submitted by

Allison K. Stafford Department of Forest, Rangeland, and Watershed Stewardship

In partial fulfillment of t he requirements

For the Degree of Master of Science Colorado State University Fort Collins, Colorado Spring 2011

Master’s Committee:

Advisor: Lee MacDonald

John Stednick Greg Buttersii ABSTRACT

SEDIMENT PRODUCTION AND DELIVERY FROM HILLSLOPES AND FOREST ROADS IN THE SOUTHERN SIERRA NEVADA, CALIFORNIA

Unpaved roads often are a major source of sediment to streams in forested watersheds, and an increase in sediment production and delivery can adversely affect the

overall health of a stream. Th e goal s of this study w ere to first quantify the effects of

climate and soil type on hillslope and road sediment production and delivery , and then

evaluate the effects of graveling, grading, and waterbar construction on road sediment production and deliver y. Sediment fences were used to collect 109 fence

- years of data from water years 2008 and 2009 in the more rain dominated José Basin (800

- 1200 m)

and 193 fence

- years of data in the snow dominated Kings River Experimental Watersheds (KREW) (1485

- 2420 m), b oth located in Sierra National Forest (SNF) in California. Detailed road surveys assessed road segment characteristics and road

- stream connectivity

. Mean hillslope sediment production in José Basin was 3.7 x 10 - 3 kg m - 2 yr - 1

, which was similar to the valu e of 4.1 x 10 - 3 kg m - 2 yr - 1 in KREW. Native surface road segments in José Basin had a mean sediment production rate of 1.8 kg m - 2 yr - 1 , and the estimated total sediment production from the 67 km of native surface roads is 680 metric tons per year. An est imated 30% of the native surface road length is connected to theiii

stream network, indicating that up to 210 metric tons of sediment may be delivered to streams each year. There was no significant difference in sediment production and delivery between road segments in the highly erodible Holland soil and road segments in

other soil types. Mean sediment production for the native surface road segments in the KREW watersheds was 0.13 kg m - 2 yr - 1 , which was more than an order of magnitude

lower than the mean va lue in José Basin , and road

- stream connectivity was o nly 3%. There was no significant difference in sediment production from native and gravel surface road segments in José Basin due to the high variability and the gravel segments still averaged 51% bare s oil

. The g ravel surface segments had shorter drainage features than native surface segments, but 40% of the gravel roads were connected as they tended to be closer to streams. Graveled roads in the Providence Creek watersheds produced 0.16 kg m - 2 yr - 1 , w hich was only 22% as much sediment as the native surface roads, and had 11% connectivity. In José Basin grading initially decreased the mean segment length from 65 m to 41 m, but one year after grading 22% of the waterbars had failed, leading to a 15%

in crease in mean segment length. Graded road segments in José Basin produced eight and three times more sediment per unit area than ungraded segments in WY2008 and WY2009, respectively, and this can be attributed to extensive rilling. Sediment production r ates decreased by 40

- 60% from the first to the second year after grading. Sediment production and delivery from forest roads can be reduced by: 1) using more than 30% gravel cover on native surface roads, 2) minimizing grading, and 3) improving the const ruction of waterbars to better withstand and direct overland flow.iv ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Lee MacDonald for his guidance, as well as Dr. John Stednick. I never could have completed this work without the astounding

su pport of friends and family. I would especially like to thank Abby Korte for her friendship and insight throughout this process. I am very grateful to Alan Gallegos, Sierra National Forest, and Carolyn Hunsaker and the Kings River Experimental

Watershed staff for their guidance, summer housing, and field support. I would also like to thank Drew Coe as well as numerous field assistants. This work has been supported by grants from the Sierra National Forest and the USDA Forest Service Region 5.v TA BLE OF CONTENTS

1. INTRODUCTION

................................ ................................ ................................ .............. 1 1.1. Literature cited

................................ ................................ ................................ ................. 7

2.EFFECTS OF CLIMATE AND SOIL TYPE ON HILLSLOPE AND NATIVE SURFACE ROAD SEDIMENT PRODUCTION AND DELIVERY

................................ ... 12 2.1. Introduction

................................ ................................ ................................ ...................... 14 2.2 Background

................................ ................................ ................................ ....................... 17 2.3. Objectives

................................ ................................ ................................ ........................ 20 2.4. Methods

................................ ................................ ................................ ............................ 21 2.4.1. Site description

................................ ................................ ................................ .............. 21 2.4.2. Precipitation

................................ ................................ ................................ .................. 23 2.4.3. Hillslope sediment production and characteristics

................................ ....................... 24 2.4.4. Road se diment production

................................ ................................ ............................ 26 2.4.5. Road segment characteristics

................................ ................................ ........................ 26 2.4.6. Road surveys

................................ ................................ ................................ ................. 27 2.4.7. Road sediment delivery

................................ ................................ ................................ . 28 2.4. 8. Comparison to WEPP:Road

................................ ................................ .......................... 29 2.4.9. Statistical analysis

................................ ................................ ................................ ......... 3 0 2.5. Results

................................ ................................ ................................ .............................. 31 2.5.1. Precipitation

................................ ................................ ................................ .................. 31 2.5.2. Hillslope characteristics and sediment production

................................ ....................... 33 2.5.3. Road segment characteristics and sediment production

................................ ............... 35 2.5.4. Road sediment delivery

................................ ................................ ................................ . 41 2.5.5. Modeling road sediment production and delivery in José Basin.

................................ . 43 2.5.5.1. Predicting sediment production from na tive surface segments in José Basin.

.......... 43 2.5.5.2. Total potential sediment produced and delivered from native surface segments in José Basin.

................................ ................................ ................................ ............................... 44 2.5.5.3. Comparison of WEPP:Road predictions to measured values in José Basin.

............. 45 2.6. Discussion

................................ ................................ ................................ ........................ 4 5 2.6.1. Effects of climate on sediment production

................................ ................................ ... 4 5 2.6.2. Predicting road sediment production in José Basin

................................ ...................... 49 2.7. Conclusions

................................ ................................ ................................ ...................... 53 2.8. Literature cited

................................ ................................ ................................ ................. 56 2.9. Tables

................................ ................................ ................................ ............................... 61 2.7. Figures

................................ ................................ ................................ .............................. 73

3. EFFECTS OF GRAVELING AND GRADING ON SEDIMENT PRODUCTION AND DELIVERY

................................ ................................ ................................ ............................. 93 3.1. Introduction

................................ ................................ ................................ ...................... 95vi

3.2 Background

................................ ................................ ................................ ....................... 98 3.2.1. Road sediment production an d delivery

................................ ................................ ...... 98 3.2.2. Effects of graveling on road sediment production and delivery

................................ 1 0 0 3.2.3. Effects of grading and waterbar installation on road sediment production and delivery

................................ ................................ ................................ ................................ .............. 1 01 3.3. Methods

................................ ................................ ................................ ......................... 1 03 3.3.1. Site description

................................ ................................ ................................ ........... 1 03 3.3.2. Precipitation

................................ ................................ ................................ ............... 1 05 3.3.3. Sediment production

................................ ................................ ................................ .. 1 06 3.3.4. Road segment characteristics

................................ ................................ ..................... 1 07 3.3.5. Rill volume and contribution to sediment erosion after grading

............................... 1 09 3.3.6. Sediment delivery

................................ ................................ ................................ ...... 1 09 3.3.7. Ro ad surveys

................................ ................................ ................................ .............. 1 11 3.3.8. Statistical analysis

................................ ................................ ................................ ...... 1 11 3.4. Results

................................ ................................ ................................ ........................... 1 12 3.4.1. Precipitation

................................ ................................ ................................ ............... 1 12 3.4.2. Effects of road surface type on road sediment production and delivery

.................... 1 14 3.4.2.1. Sediment production

................................ ................................ ............................... 1 14 3.4.2.2. Predicting sediment production for gravel surface roads in José Basin

................. 1 20 3.4.2.3. Sediment delivery

................................ ................................ ................................ ... 1 22 3.4.3. Effects of grading in José Basin

................................ ................................ ................. 1 26 3.4.3.1. Effects of grading on segment characteristics

................................ ........................ 1 26 3.4.3.2. Effects o f grading on sediment production

................................ ............................. 1 27 3.4.3.3. Rill erosion after grading

................................ ................................ ........................ 1 30 3.4.3.4. Effects of grading on road surface bulk density

................................ ..................... 1 31 3.4.3.5. Effects of grading on sediment delivery

................................ ................................ . 1 32 3.5. Discussion

................................ ................................ ................................ ..................... 1 33 3.5.1. Effects of graveling on sediment production and delivery

................................ ........ 1 33 3.5.2. Effects of grading and water bar installation in José Basin on sediment proudction and delivery

................................ ................................ ................................ ................................ 1 36 3.6. Conclusions

................................ ................................ ................................ ................... 1 40 3.7. Literature cited

................................ ................................ ................................ .............. 1 43 3.8. Tables

................................ ................................ ................................ ............................ 1 48 3.9. Figures

................................ ................................ ................................ ........................... 1 60

4. APPENDICES

................................ ................................ ................................ ................. 1 82 A. Hillslope characteristics and sediment production rates in José Basin, WY2008

- 2009

. 1 82 B. Hillslope characte ristics and sediment production rates in the Providence Creek watersheds, WY2004

- 2009

................................ ................................ ................................ .. 1 83 C. Hillslope characteristics and sediment production rates in the Providence Creek watersheds, WY2004

- 2009

................................ ................................ ................................ .. 1 84 D. Native surface road segment characteristics and sediment production rates in José Basin, WY2008

- 2009

................................ ................................ ................................ ...................... 1 85 E. Road segment characteristics and sediment production rates in the Providence Creek watersheds, WY2008

- 2009

................................ ................................ ................................ .. 1 86vii

F. Native surface road segment characteristics and sediment production rates in the Bull Creek watersheds, WY2008

- 2009

................................ ................................ ....................... 1 87 G. Gravel surface road segment characteristics and sedime nt production rates in José Basin, WY2008

- 2009

................................ ................................ ................................ ...................... 1 88 H. Road characteristics before, immediately after, and one year after grading

................... 1 89 H. Road segment characteristics and sediment production o ne and two years after grading in José Basin, WY2008 and WY2009

................................ ................................ ..................... 1 901. INTRODUCTION Increased sediment loading adversely impacts streams, as it can affect water quality, stream habitat, and aquatic ecosystems (Tagart, 1976; Cederholm et al., 198 1; Reid and Dunne, 1984; Bilby et al., 1989; Ziegler and Giambelluca, 1997; Kolka and Smidt, 2004). Inputs of fine sediment can decrease pool depth and abundance, and increase turbidity, both of which can alter the quality and quantity of habitat for

salm onids and limit reproduction (Harr and Nichols, 1993; Weaver and Hagans, 1999; Beechie et al., 2005). Increased sediment loading also affects aquatic organisms by altering the temperature and nutrient loads in the stream (Kolka and Smidt, 2004).

Addition ally, increased sediment delivery to reservoirs reduces the usable capacity and interferes with piping systems (Minear and Kondolf, 2009). The U.S. Environmental Protection Agency lists sediment as the most common impairment to water quality in

streams an d lakes in the United States (EPA, 2010). Hillslope sediment production rates in undisturbed forested watersheds are typically very low (MacDonald et al., 2003), as forests have a dense surface cover of vegetation and litter and a high porosity and infil tration rate (Dunne and Leopold, 1978). In contrast, unpaved roads have a low infiltration rate and little to no surface cover, so they often are a major sediment source in forested watersheds (Reid and Dunne, 1984; Swift, 1988; Bilby et al., 1989; Luce a nd Black, 1999; Ketcheson et al. 1999; Coe, 2006). Studies spanning a variety of differently designed and surfaced roads in rain, rain

- on

snow, and snow climates have found that road sediment production rates vary by two to three orders of magnitude due t o differences in climate, soil type, road surface type and design, and road maintenance practices such as grading (Megahan, 1974; Reid and2

Dunne, 1984; Kochenderfer and Helvey, 1987; Bilby et al., 1989; Burroughs and King, 1989; Luce and Black, 1999; Luce and Black, 2001; MacDonald et al., 2001; Ziegler et al., 2001; Appelboom et al., 2002; Clinton and Vose, 2003; Motha et al., 2004; Ramos

Scharrón and MacDonald, 2005; Barrett and Tomberlin, 2006; Coe, 2006; Forsyth et al., 2006; Sheridan and Noske, 2007; S ugden and Woods, 2007; Welsh, 2008). The large range found in these studies shows that road sediment production rates are case

- specific, and rates found in one location cannot necessarily be applied elsewhere. Road surface sediment production is the resul t of several erosional and transport processes. These include: 1) rainsplash detachment; 2) sheetwash; and 3) rill erosion (Zeigler et al., 2000). The absolute and relative magnitudes of these processes depend on

a number of location

- specific climatic an d road surface variables. Road runoff and sediment production may only be a concern if this material is delivered to a stream or other water body. Road sediment delivery is determined by the amount of runoff leaving

the road surface as well as the locati on of road drainage points relative to the stream network (Megahan and Ketcheson, 1996; Croke and Mockler, 2001; Croke et al., 2005; Croke and Hairsine, 2006; Lane et al., 2006). Climate is one of the most important controls on road sediment production, a s this affects the amount, type, and intensity of precipitation (MacDonald et al., 2001). Unpaved roads in rain dominated climates should produce much more sediment than comparable roads in snow dominated climates, as rainfall is more erosive than snow. In mountainous areas, the rain to snow ratio is largely driven by elevation. No one study has simultaneously measured and compared sediment production rates across rain, rain

-3

on

- snow, and snow dominated climates to quantify the effects of climate in one

g eographic area. Soil type is another important control on road sediment production, as this affects the particle

- size distribution and soil erodibility. Several studies have compared road sediment production and delivery between different soil types (R ice and Lewis, 1991; Luce and Black, 1999; Sugden and Woods, 2007), but no study has compared hillslope or road sediment production and delivery from the highly erosive Holland soil (USDA, 1983) to other soil types in California’s southern Sierra Nevada. The same factors controlling sediment production on native surface roads also control sediment production on gravel surface roads, but the relative magnitude of the various processes can differ greatly from native surface roads. Most studies have sho wn sediment production rates from gravel surface roads to be lower than values from comparable native surface roads, and this can be largely attributed to the protection from rainsplash and reductions in surface erodibility and overland flow velocities (Ko chenderfer and Helvey, 1987; Burroughs and King, 1989; Appelboom et al., 2002; Sheridan and Noske, 2003; Barrett and Tomberlin, 2006; Coe, 2006; Forsyth et al., 2006; Korte, in preparation). However, no study has directly compared the relative effects of graveling between rain and snow dominated climates in one geographic area. Grading is an important and common road maintenance technique when surface erosion hinders the road’s drivability. Grading is often paired with the construction or re

establishment of waterbars, which drain water off the road surface and reduce the contributing area of a road segment, thereby potentially decreasing sediment production and delivery. The surface disturbance due to grading increases the supply of material for4

transpor t, thus leading to an initial increase in sediment production (Megahan and Kidd, 1972; Megahan, 1974; Reid and Dunne, 1984; Megahan et al., 1986; Luce and Black, 1999; Ziegler et al., 2000; Ziegler et al., 2001; Appelboom et al., 2002; Ramos

- Scharrón

and M acDonald, 2005; Coe, 2006). Quantifying the amount and persistence of the increase in sediment production after grading is necessary for forest managers to determine the optimal frequency of grading versus maintaining the drivability of the road. Quanti fying the effect of grading on waterbar frequency and performance is necessary to determine how grading affects road sediment delivery to streams. The combination of grading and waterbar installation or maintenance may result in either an increase or decr ease in sediment delivery to the stream network, depending on whether delivery is reduced enough to outweigh the increase in sediment production; hence it is important that both aspects be examined. Forest managers need to identify the key variables fo r road sediment production and delivery to guide road construction and maintenance. Several studies have examined these key variables and attempted to predict road sediment production and delivery rates (Ziemer et al., 1991; Harden, 1992; Luce and Cundy, 1994; Elliot et al., 1999; Doten et al., 2006; Ramos

- Scharrón and MacDonald, 2007). As with the magnitude of sediment production, the controls on sediment production vary with location and climate, and this study will quantify these variables in José Basi n, a 78 km 2 rain dominated watershed in

the Sierra Nevada of California. The present study is building on previous work on road sediment production and delivery rates in the Sierra Nevada. The first of these studies was in the Eldorado

National Fore st in the northern Sierra Nevada (Coe, 2006). Sediment production rates5

were measured for three water years (WY2000 to WY2002) for 15 native surface road segments that were not recently graded, for 2

- 40 road segments graded within the past two years, and for 9

- 10 gravel surface road segments. Elevations were between 1000 and 1800 m, so the area has a highly variable mixture of rain and snow. Segment

- scale measurements and road surveys were used to determine the dominant controlling variables and predict road sediment production and delivery (Coe, 2006). The second study was in the higher elevation (1485

- 2420 m), rain

- on

- snow and snow dominated Kings River Experimental Watershed (KREW) in the Sierra National Forest (SNF) (Korte, in preparation). This st udy quantified sediment production rates from WY2004 through WY2006 for: 9

- 20 hillslopes; 23

- 34 native, gravel, and mixed surface road segments; and seven ditches adjacent to paved roads. This study also determined key variables for predicting sediment pr oduction and used road surveys to evaluate sediment delivery pathways and (Korte, in preparation). These data were combined with three additional years of monitoring under the present study to allow more direct comparisons between KREW and José Basin.

Th e overall goals of this study were to : 1) compare sediment production rates from hillslopes and forest roads in rain and snow dominated climates; 2) evaluate the effects of graveling and grading on road sediment production and delivery; and 3) predict

road sediment production rates in José Basin. Chapter 2 of this thesis quantifies the effects of elevation and soil type on sediment production and delivery by: 1) comparing sediment production rates from undisturbed hillslopes and native surface road segment s between the snow dominated KREW watersheds and the rain dominated José Basin; 2) comparing sediment production rates from hillslopes and native surface road segments on6

Holland soil and other, less erosive soils in José Basin; and 3) estimating sediment production and delivery from native surface roads in José Basin. Chapter 3 quantifies the effects of graveling, grading, and waterbar construction and maintenance on sediment production and delivery by: 1) comparing sediment production and delivery betwe en native and gravel surface roads; 2) estimating total sediment production and delivery from gravel surface roads in José Basin; and 3) quantifying the effect of grading and waterbar installation on road segment characteristics, road sediment production, and road sediment delivery in José Basin. Forest managers must constantly work to balance public accessibility and forest conservation. While roads are necessary for public accessibility and management activities, they may negatively affect water quality and stream health. The results of this study help quantify the variations in road sediment production and delivery from hillslopes and roads in different climates in the SNF, and guide management practices to

reduce road sediment contributions while main taining drivability.7

1.1. Literature cited Appelboom, T.W., G.M. Chescheir, R.W. Skaggs, and D.L. Hesterberg. 2002. Management practices for sediment reduction from forest roads in the coastal plains. American Society of Agricultural Engineers 45(2): 3 37

- 344. Barrett, B., and D. Tomberlin. 2008. Sediment production on forest road surfaces in California’s redwood region: results for HY2006 and HY2007. California Board of Forestry and Fire Protection

- Monitoring Study Group Meeting, February 13, 2008, Red ding, CA, USA. Beechie, T.J., C.N. Veldhuisen, E.M. Beamer, D.E. Schuett

- Hames, R.H. Conrad, and P. DeVries. 2005. Monitoring treatments to reduce sediment and hydrologic effects from roads. In: Monitoring Stream and Watershed Restoration , Roni, R. (ed.). America Fisheries Society, Bethesda, MD, USA. Pp. 35

- 65. Bilby, R.E., K. Sullivan, and S.H. Duncan. 1989. The generation and fate of road

surface sediment in forested watersheds of south

- western Washington. Forest Science 35: 453

- 468. Burroughs, E.R., and J.G. King. 1989. Reduction of soil erosion on forest roads. USDA Forest Service GTR

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- 261, Ogden, UT, USA. 21 pp. Cederholm, C.J., L.M. Reid, and E.O. Salo. 1981. Cumulative effects of logging road sediment on salmonids populations in the Clearwater River, Jefferson County, Washington. In: Salmon

- Spawning Gravel: A Renewable Resource in the Pacific Northwest? Washington Water Research Center, Pullman, WA, USA. Pp. 38

- 74. Clinton, B.D., and J.M. Vose. 2003. Differences in surface water quality draini ng four road surface types in the southern Appalachians. Southern Journal of Applied Forestry 27(2): 100

- 106. Coe, D. 2006. Sediment production and delivery from forest roads in the Sierra Nevada, California. M.S. thesis, Colorado State University, Fort C ollins, CO, USA. 107 pp. Croke, J.C., and P.B. Hairsine. 2006. Sediment delivery in managed forests: A review. Environmental Review 14: 59

- 87. Croke, J., and S. Mockler. 2001. Gully initiation and road

- to

- stream linkage in a forested catchment, southeast ern Australia. Earth Surface Processes and Landforms 26: 205

- 217. Croke, J., S. Mockler, P. Fogarty, and I. Takken. 2005. Sediment concentration changes in runoff pathways from a forest road network and the resultant spatial pattern of catchment connectiv ity. Geomorphology 68: 257

- 268.8

Doten, C.O., L.C. Bowling, J.S. Lanini, E.P. Maurer, and D.P. Lettenmaier. 2006. A spatially distributed model for the dynamic prediction of sediment erosion and transport in mountainous forested watersheds. Water Resources Research 42: 1

- 15. Dunne, T., and L. Leopold. 1978. Water in Environmental Planning . W.H. Freeman and Co., New York, NY, USA. Elliot, W.J., R.B. Foltz, and C.H. Luce. 1999. Modeling low

- volume road erosion. Transportation Research Record 1652: 244

- 249. EPA, 2010. What is sediment pollution? United States Environmental Protection Agency. <www.epa.gov/owow_keep/NPS/toolbox/other/KSMO_Sediment.pdf>. Forsyth, A.R., K.A. Bubb, and M.E. Cox. 2006. Runoff, sediment loss and water quality from forest roads in a southeast Queensland coastal plain Pinus plantation. Forest Ecology and Management 221: 194

- 206. Harden, C.P. 1992. Incorporating roads and footpaths in watershed

- scale hydrologic and soil erosion models. Physical Hydrology 13(4): 368

- 385. Harr, R.D., and R.A. Nichols. 1993. Stabilizing forest roads to help restore fish habitats: A northwest Washington example. Fisheries 18(4):18

- 22. Ketcheson, G.L., W.F. Megahan, and J.G. King. 1999. ―R1

- R4‖ and ―BOISED‖ sediment prediction model tests using forest roads in granitics. Journal of American Water Resources Association 35(1): 83

- 98. Kochenderfer, J.N., and J.D. Helvey. 1987. Using gravel to reduce soil losses from minimum

- standard forest roads. Journal of Soil and Water Conservation 42(1): 46

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Kol ka, R.K., and M.F. Smidt. 2004. Effects of forest road amelioration techniques on soil bulk density, surface runoff, sediment transport, soil moisture, and seedling growth. Forest Ecology and Management 202: 313

- 323. Korte, A. In preparation. Effects of s urface type on sediment production and delivery from forest roads in the Sierra Nevada, California. M.S. thesis, Colorado State University, Fort Collins, CO, USA. Lane, P.N.J., P.B. Hairsine, J.C. Croke, and I. Takken. 2006. Quantifying diffuse pathways for overland flow between the roads and streams of the Mountain Ash forests of central Victoria Australia. Hydrological Processes 20: 1875

- 1884. Luce, C.H., and T.A. Black. 1999. Sediment production from forest roads in western Oregon. Water Resources Res earch 35(8): 2561

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Luce, C.H., and T.A. Black. 2001. Effects of traffic and ditch maintenance on forest road sediment production. In: Proceedings of the Seventh Federal Interagency Sedimentation Conference . March 25

- 29, 2001. Reno, NV, USA. Pp. V67

- V 74. Luce, C.H. and T.W. Cundy. 1994. Parameter identification for a runoff model for forest roads. Water Resources Research 30(4): 1057

- 1069. MacDonald, L.H., D. Coe, and S. Litschert. 2003. Assessing cumulative watershed effects in the central Sierra Ne vada: Hillslope measurements and catchment

- scale modeling. In: Proceedings of the Sierra Nevada Science Symposium: Science for Management and Conservation PSW

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- 193. Pp. 149

- 157. MacDonald, L.H., R.W. Sampson, and D.M. Anderson. 2001. Runoff and road ero sion at the plot and road segment scale, St. John, U.S. Virgin Islands. Earth Surface Processes and Landforms 26: 1

- 22. Megahan, W.F. 1974. Erosion over time: A model. USDA Forest Service Research Paper INT

- 156, Ogden, UT, USA. 14 pp. Megahan, W.F., and G.L. Ketcheson. 1996. Predicting downslope travel of granitic sediments from forest roads in Idaho. Water Resources Bulletin 32(2): 371

- 382. Megahan, W.F., and W.J. Kidd. 1972. Effects of logging and logging roads on erosion and sediment deposition from s teep terrain. Journal of Forestry 70(3):136

- 141. Megahan, W.F., Seyedbagheri, K.A., and T.L. Mosko. 1986. Construction phase sediment budget for forest roads in granitic slopes in Idaho. In Drainage Basin Sediment Delivery , Hadley, R.F. (ed.). IAHS Publi cation 159: 31

- 39. Minear, J.T. and G.M. Kondolf. 2009. Estimating reservoir sedimentation rates at large spatial

- and temporal

- scales: a case study of California. Water Resources Research 45(12): W12502

- W12509. Motha, J.A., P.J. Wallbrink, P.B. Hairsine , and R.B. Grayson. 2004. Unsealed roads as suspended sediment sources in an agricultural catchment in south

- eastern Australia. Journal of Hydrology 286: 1

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Ramos

- Scharrón, C.E., and L.H. MacDonald. 2005. Measurement and prediction of sediment producti on from unpaved roads, St John, US Virgin Islands. Earth Surface Processes and Landforms 30: 1283

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Ramos

- Scharrón, C.E., and L.H. MacDonald. 2007. Development and application of a GIS

- based sediment budget model. Journal of Environmental Management 8 4: 157

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Renard, K.G., G.R. Foster, G.A. Weesies, D.K. McCool, and D.C. Yoder. 1997. Predicting soil erosion by water: A guide to conservation planning with the Revised Universal Soil Loss Equation (RUSLE). USDA Agricultural Handbook No 703. 324 pp. Rice, R.M., and J. Lewis. 1991. Estimating erosion risks associated with logging and forest roads in northwestern California. Water Resources Bulletin 27(5): 809

- 818. Sheridan, G.J., and P.J. Noske. 2007. A quantitative study of sediment delivery and stream pollution from different forest road types. Hydrological Processes 21: 387

- 398. Swift Jr., L.W. 1988. Forest access roads: Desig n, maintenance, and soil loss. In: Forest Hydrology and Ecology at Coweeta. Swank, W.T., and D.A. Crosley, Jr. (eds.). Springer

- Verlag, New York, USA. Pp. 313

- 324. Sugden, B.D., and S.W. Woods. 2007. Sediment production from forest roads in Western Mont ana. Journal of the American Water Resources Association 43(1): 193

- 206. Tagart, J.V. 1976. The survival from egg deposition to emergence of Coho salmon in the Clearwater River, Jefferson County, Washington. M.S. thesis, University of Washington, Seattle, WA, USA. 101 pp. USDA Forest Service. 1983. Soil survey of Sierra National Forest area, California. USDA Forest Service, Pacific Southwest Region: Auberry, Cascadel Point, Musick Mtn., and Shaver Lake Quadrangles. 1:24,000. Weaver, W., and D. Hagans. 1999. Storm

- proofing forest roads. In: Proceedings of the International Mountain Logging and 10 th Pacific Northwest Skyline Symposium , OSU Department of Forest Engineering and International Union of Forestry Research Organizations, Corvallis, OR, USA. Pp. 230

- 245. Welsh, M.J. 2008. Sediment production and delivery from forest roads and off

- highway vehicle trails in the upper South Platte River watershed, Colorado. M.S. thesis, Colorado State University, Fort Collins, CO, USA. 154 pp. Ziegler, A.D., and T. W. Giambelluca. 1997. Importance of rural roads as source areas for runoff in mountainous areas of northern Thailand. Journal of Hydrology 196 : 204

- 229. Ziegler, A.D., R.A. Sutherland, and T.W. Giambelluca. 2000. Partitioning total erosion on unpaved road s into splash and hydraulic components: The roles of interstorm surface preparation and dynamic erodibility. Water Resources Research 36(9): 2787

- 2791. Ziegler, A.D., R.A. Sutherland, and T.W. Giambelluca. 2001. Interstorm surface preparation and sedimen t detachment by vehicle traffic on unpaved mountain roads. Earth Surface Processes and Landforms 26: 235

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Ziemer, R.R., J. Lewis, R.M. Rice, and T.E. Lisle. 1991. Modeling the cumulative watershed effects of forest management strategies. Journal of E nvironmental Quality 20(1): 36

- 42.12

2. EFFECTS OF CLIMATE AND SOIL TYPE ON HILLSLOPE AND NATIVE SURFACE ROAD SEDIMENT PRODUCTION AND DELIVERY

ABSTRACT:

Sediment is the dominant non

- point source pollutant in streams, and unpaved

roads are often considered to be a major source of sediment in forested watersheds. The overall goal of this study was to assess sediment production and delivery from hillslopes and roads in two study areas in the southern Sierra Nevada of California. The first study area, José B asin, is a 78 km 2 rain dominated watershed, and the second was the Kings River Experimental Watershed (KREW), which contains two groups of four small, snow dominated watersheds. Sediment production was measured with sediment fences for two water years in José Basin, and up to six water years in KREW. The specific objectives were to: 1) quantify the effects of climate on sediment production and delivery rates from hillslopes and native surface road segments; 2) quantify the effects of soil type on

sediment production and delivery rates from hillslopes and native surface road segments in José Basin; and 3) estimate the total sediment production and delivery from native

surface roads in José Basin. In José Basin, the mean hillslope sediment production rate w as 3.7 x 10 - 3 kg m - 2

yr - 1 , and for native surface roads the value was 1.8 kg m - 2 yr - 1 , or nearly 500 times higher. Hillslope and road sediment production rates were not significantly different between the highly erodible Holland soils and other soil types . Rilled road segments produced significantly more sediment than segments without rills. Detailed road surveys and an empirical model indicate that native surface roads in José Basin produce 680 metric tons

yr - 1 of sediment and potentially deliver 210 me tric tons yr - 1 to the stream network. Much13

of this sediment is coming from a relatively few segments with extensive rilling that are

located close to a stream. At the higher elevation KREW sites the mean sediment production rates for hillslopes and road s were an order of magnitude lower than in José Basin. The potential increase in air temperatures due to climate change and the associated shift from snow to rain will increase hillslope road erosion rates as well as sediment delivery to streams. Managem ent practices to reduce road sediment production and delivery should focus in rain dominated climates where erosion rates are likely to be higher than in snow

dominated areas.14

2.1. Introduction Increased sediment loading to streams, rivers, and lakes is a major concern, as this can adversely affect water quality, stream habitat, and aquatic ecosystems (Bilby et al., 1989; Ziegler and Giambelluca, 1997; Kolka and Smidt, 2004). Fine sediment also can decrease pool depth and abundance, and increase the t urbidity of the stream (Beechie et al., 2005), both of which can alter the quality and quantity of habitat for salmonids and limit reproduction (Harr and Nichols, 1993; Weaver and Hagans, 1999; Beechie et al., 2005). Increased sediment loading affects aqu atic organisms by altering the temperature and nutrient loads in the stream (Kolka and Smidt, 2004). Sediment is the most common impairment to water quality in streams and lakes in the United States (EPA, 2010). Additionally, increased sediment delivery reduces reservoir capacity and can clog or damage pipes (Minear and Kondolf, 2009). Hillslope sediment production rates in undisturbed forested watersheds are typically very low (MacDonald et al., 2004), as forests have a dense surface cover of vegetatio n and litter and a high porosity and infiltration rate (Dunne and Leopold, 1978). These characteristics largely prevent soil detachment and overland flow (Dunne and Leopold, 1978). Surface disturbances such as fire, concentrated grazing, and road

constru ction can expose the mineral soil and greatly reduce the infiltration rate (MacDonald et al., 2001; Ramos

- Scharrón and MacDonald, 2005). This increases rainsplash erosion and the likelihood of erosive overland flow, which can detach soil particles and tr ansport them to the stream network. The surface of an unpaved road is typically dominated by exposed mineral soil, and in forested watersheds unpaved roads are often a major source of sediment to streams15

(Reid and Dunne, 1984; Swift, 1988; Bilby et al., 19 89; Luce and Black, 1999; Ketcheson et al. 1999; Coe, 2006). Unpaved roads can deliver a large amount of sediment to streams relative to their surface area even during low to moderate rainfall events due to their characteristically low infiltration rates (Ziegler and Giambelluca, 1997; Chappell et al., 1999; Ziegler et al., 2004; Cafferata et al., 2007). The amount of road sediment delivered to streams is determined by the amount of runoff leaving the road surface as well as the location of drainage poin ts relative to streams. While several studies have examined road sediment delivery pathways (Megahan and Ketcheson, 1996; Croke and Mockler, 2001; Croke et al., 2005; Croke and Hairsine, 2006; Lane et al., 2006), both road sediment production and sediment delivery are highly location

- specific, as they depend on variables such as climate, soil type, slope, and surface cover. Numerous attempts have been made to predict sediment production and delivery for a range of climates and types of roads, most notably by using the physically

- based WEPP:Road model. However, more accurate estimates may be obtained by measuring road segment characteristics and sediment production rates for a specific area or climate, and developing local empirical models. Alternatively, such data also can be used to test the validity of WEPP:Road or other models. Sediment production and delivery from forest roads has been monitored in the Sierra Nevada mountains in California by Colorado State University graduate students

since 1999. Th e first study in the Eldorado National Forest in the northern Sierra Nevada (Figure 2.1) measured sediment production rates from 15 native surface road segments that were not recently graded from water year (WY) 2000 to WY2002 (Coe, 2006). Elevations rang ed from 1000 to 1800 m, and the area has a mixed rain and snow climate.16

Mean annual sediment production from the native surface road segments varied from 0.22 to 0.81 kg m - 2 , and road surveys indicated that 25% of the road length was hydrologically connec ted to the stream network (Coe, 2006). . The second study was located further south in the Sierra National Forest (SNF) in the Kings River Experimental Watershed (KREW) (Figure 2.1). This study monitored sediment production from 9

- 18 undisturbed hillslop es and 11

- 22 native surface road segments from WY2004 to WY2006 (Korte, in preparation). Elevations ranged from 1485 to 2420 m, and the area is snow and rain

- on

- snow dominated. The mean sediment production rate on undisturbed hillslopes was 0.01 kg m - 2 y r - 1 (s.d. = 0.02 kg m - 2 yr - 1 ), and mean annual production rates for hillslopes in the mid

- elevation Providence Creek watersheds (1485

- 2005 m) were similar to the mean values for the upper elevation Bull Creek watersheds (2050

- 2420 m). The mean values for native surface road segments ranged from 0.0 to 6.2 kg m - 2 yr - 1 , and the overall mean road erosion rate of 0.74 kg m - 2

yr - 1 (s.d. = 1.2 kg m - 2 yr - 1 ) was comparable to the higher values from the Eldorado National Forest. In contrast to the hillslopes, the mean annual sediment production rate for the native surface road segments in the Providence Creek watersheds was 4

- 15 times the value for the Bull Creek watersheds. The high interannual variability and high variability among segments within a water year i ndicated a need for continued monitoring and data analysis. The present study continued monitoring sediment production rates from undisturbed hillslopes and road segments in the KREW watersheds, but the primary focus was shifted to José Basin, a 78 km 2 wat ershed located 20 km west of KREW. Road sediment production rates in José Basin are expected to be higher than values found by17

the two previous studies as the climate is rain rather than snow dominated. Hence the goals of this study were to measure sedim ent production and delivery from hillslopes and forest roads in José Basin from different soil types, and use these data to examine the effects of climate on sediment production and delivery.

2.2. Background

Water

- driven erosion at the road segment sca le depends on several interacting erosion and transport processes, including rainsplash, sheetwash, and rill erosion (Zeigler et al., 2000). Rainsplash detachment occurs when the impact from a falling raindrop detaches sediment particles (Zeigler et al., 2000). The rate of rainsplash detachment is highly dependent on the rainfall erosivity, which in turn is a function of the precipitation intensity and the drop size distribution (Lal, 1988; Renard et al., 1997). Snowfall has minimal erosive energy, as it is lighter and falls much more slowly than rain. Rainsplash is minimal on forested, undisturbed hillslopes, as the surface is protected by vegetation and litter (Dunne and Leopold, 1978), but it can play a major role in sediment production

from native su rface roads (Ziegler et al., 2000). In Thailand, which has a monsoonal rainfall climate, rainsplash detachment accounted for 38

- 45% of sediment production from the road surface, even though the surface was highly compacted (Ziegler et al., 2000).

When r ainfall intensity exceeds the infiltration capacity of a surface, water flows downslope as infiltration

- excess or Horton overland flow (HOF), which can result in sheetwash and/or rill erosion (Dunne and Leopold, 1978). Sheetwash occurs when water

flows ac ross the surface in a sheet, detaching and transporting sediment (Dunne and18

Leopold, 1978). Rill erosion is when water collects into channels due to the surface’s

micro

- topography. The concentrated flow can detach and transport sediment from the rill

bed and sides (Dunne and Leopold, 1978). Both sheetwash and rill erosion occur when the shear stress applied by the flow exceeds the resistance of the surface (Dunne and Leopold, 1978; Luce and Black, 1999; Croke and Hairsine, 2006). The shear stress of a given flow is given by τ = γdS (equation 2.1)

where τ is the shear stress ( Newtons m - 1 ), γ is the fluid density (Newtons m - 2 ), d is the depth of flow (m), and S is the surface slope (m m - 1 ). The depth of flow is a function of the duration and intensity of a given precipitation event relative to the infiltration rate. In the Sierra Nevada, snowmelt rates are typically much lower than rainfall intensities, allowing more time for the snowmelt to infiltrate and resulting in a much lower

likelihood of HOF. Infiltration rates on undisturbed, forested hillslopes are high, and HOF rarely occurs (Dunne and Leopold, 1978). Infiltration rates for unpaved roads tend to be very low; values in Idaho, Colorado, and Montana varied between 5 x 10 - 5 and 8.8 mm h - 1

with a geometric mean of 0.11 mm h - 1 (Luce and Cundy, 1994). Therefore, assuming a spatially uniform precipitation rate, the discharge from a road segment is directly proportional to the area of that segment, while the velocity of the flow is directly

proport ional to the slope of a road segment (Ramos

- Scharrón and MacDonald, 2007). The rainsplash detachment, shear stress of HOF, and resulting transport capacity are direct functions of the precipitation characteristics and the contributing area and slope of

a road segment (Anderson and MacDonald, 1998; MacDonald et al., 2004).19 As runoff becomes channelized into rills, the detachment and transport capacity increases because the flow is deeper and faster (Merz and Bryan, 1993; Brunton and Bryan, 2000). The exten t of rilling will vary with soil properties and precipitation characteristics (Brunton and Bryan, 2000). In Colorado, road sediment production was strongly related to rill density (R 2 = 0.57, p < 0.0001) (Welsh, 2008). In agricultural and burned areas, r ill erosion may be more important than sheetwash erosion (Pietraszek, 2006), but few data are available on the balance between sheetwash and rill erosion for unpaved roads. Soil type is another important control on road sediment production, as this affects the soil erodibility. Soil erodibility is one of the controlling factors in the Revised Universal Soil Loss Equation (RUSLE), and this is calculated from the soil texture, organic matter content, structure, and permeability (Renard et al., 1997). In Jo sé Basin, the soils in the Holland series are notably more erosive as the soil erodibility (K factor) in RUSLE is 0.28. This is higher than the values of 0.20 or less for all other soil types (USDA, 1983). Exposure of the sandy clay loam B horizon is tho ught to especially lead to surface erosion. This has led to more extensive rocking and other treatments on roads in Holland soils (A. Gallegos, pers. comm., USDA Forest Service, 2007).

Road

- stream connectivity determines the hydrologic effects of roads at the watershed scale (Wemple et al., 1996; La Marche and Lettenmaier, 2001; Bowling and Lettenmaier, 2001). Sediment from roads is contributed to the stream network when sediment produced exits the road surface and flows into a stream (Croke and Mockler, 2001), such as at stream crossings (Wemple et al., 1996; Croke and Mockler, 2001; Coe, 2006). Road

- stream crossings are rare in the two study areas, so most of the road

- stream20

connectivity is due to the concentrated runoff from a road extending to a strea m as evidenced by a sediment plume or small channel (Montgomery, 1994; Wemple et al., 1996; Croke and Mockler, 2001; La Marche and Lettenmaier, 2001; Bowling and Lettenmaier, 2001). Road sediment production and delivery modeling is necessary to estimate th e amount of sediment delivered from roads to streams, and modeling also can help direct management practices to those road segments with the highest potential for sediment delivery. The most common road sediment production and delivery model is WEPP:Road, a web

- based interface based on the Water Erosion Prediction Project (WEPP). This is designed to predict sediment production and delivery from road segments, compacted landings, compacted skid trails, and compacted foot, cattle, or off

road vehicle trails (Elliot, 1999). WEPP:Road is a process

- based model which only requires users to specify key variables, namely the climate, soil type, gravel cover, local topography, segment length, segment slope, road design, surface conditions, ditch conditions, and di stance to streams.

2.3. Objectives Given this background, t he specific objectives were to: 1) measure sediment production rates from undisturbed hillslopes and native surface road segments in KREW and José Basin; 2) use these data to quantify the effect s of climate on sediment production and delivery; 3) quantify the effects of soil type on hillslope and road sediment production and delivery in José Basin; 4) estimate the basin

- wide annual native surface road sediment production and delivery rate for Jos é Basin; and 5) compare the21

measured road sediment production rates to m odeled values using WEPP:Road. Working hypotheses were that r oad sediment production rates would be higher in rain dominated

climates than in sno w dominated climates, and higher on ro ads in Holland soils than other soil types. Sediment production rates from undisturbed hillslopes also were expected to be significantly less than values from native surface roads.

2.4. Methods 2.4.1. Site description

José Basin

José Basin is a 78 km 2 watershed in Sierra National Forest, located in the southern Sierra Nevada of California (Figure 2.1). Elevations range from 450 to 1950 m (Figure 2.2), although most of the study sites were located between 800 and 1200 m. The area

has a Mediterranean

- t ype climate with dry summers and wet winters. Most precipitation at the lower elevations falls as rain, and in the upper portions of the basin there is usually a seasonal snowpack and rain

- on

- snow events occur frequently due to diurnal and

seasonal fluctu ations (A. Gallegos, USFS, pers. comm., 2008). The middle and upper elevations in José Basin are dominated by conifers, particularly ponderosa pine ( Pinus ponderosa ) and incense cedar ( Libocedrus decurrens ). At lower elevations, brush stands are more co mmon, and these contain ceanothus ( Ceanothus spp.), manzanita ( Arctostaphylos spp.), and other species. Primary soil types are the Shaver, Tollhouse, Chawanakee, and Holland series (USDA, 1983). As stated earlier, Holland soils are regarded as being part icularly susceptible to surface erosion (A. Gallegos, USFS, pers. comm., 2007).22 There are 447 km of stream channels in José Basin and the drainage density is 5.7

km km - 2 (Figure 2.3) (SNF data base, accessed via A. Gallegos, 2007). The basin has an

exte nsive road network, with 159 km of mapped roads for a relatively high road density

of 2.0 km km - 2 (Figure 2.3) (SNF data base, accessed via A. Gallegos, 2007). The mean road width is approximately 2.6 m, indicating that roads occupy only 0.53% of the tota l surface area. Much of the basin is managed by the SNF, but there are extensive private land holdings. Road access is crucial in José Basin as there are scattered houses in some

areas , and the basin is heavily used for grazing, logging, and recreational uses such as hunting and off

- highway vehicles.

Providence and Bull Creek Watersheds, KREW The Kings River Experimental Watershed (KREW) is 20 km east of José Basin, and is also in the SNF (Figure 2.1). KREW contains two groups of four watersheds; the lower elevation group is the Providence Creek watersheds (1485 to 2005 m) (Figure 2.4a), and the higher elevation group is the Bull Creek watersheds (2050 to 2420 m) (Figure 2.4b). The eight watersheds range in size from 0.53 to 2.27 km 2 . Average annual precipitation is 1240 mm, with approximately 90% of the precipitation falling as snow, and the Bull Creek watersheds typically have a higher snow to rain ratio than the Providence Creek watersheds (Korte and MacDonald, 2007). Vegetation in the

Providence Creek watersheds is primarily Sierra mixed

- conifer forest, while the Bull

Creek watersheds have Sierra mixed

- conifer forest that grades into red fir ( Abies magnifica) at higher elevations . The KREW watersheds have primarily Gerle, Cagwin,23

and Shaver serie s soils, which are coarse sandy loam and loamy sand soils with granitic lithology (USDA, 1983)

.

2.4.2. Precipitation

José Basin Five tipping bucket rain gages were installed in José Basin (Figure 2.2), but equipment problems and vandalism meant that valid data were co llected from four rain gages in WY2008 and three gages in WY2009. Annual precipitation and annual erosivity were calculated using the RF program for each gage for WY2008 and WY2009 (Petkovsek, 2001). No correlation was found between elevation and annual precipitation or annual erosivity for either water year, so data from the nearest functioning rain gage were assigned to each site where sediment production was measured. The precipitation data from José Basin was put in historical context by using the

95 years of precipitation data from the Auberry climate station, which is the closest long

term station. The elevation of the Auberry station is 640 m and it is approximately 10 km west of José Basin (Figure 2.1). Annual precipitation from the rain gages in José Basin was compared to the long

- term mean annual precipitation and the measured precipitation at Auberry for WY2008 and WY2009.

Providence Creek and Bull Creek watersheds, KREW Precipitation data were collected at 15

- minute intervals at upper and lo wer

climate stations in both the Providence Creek and Bull Creek watersheds for WY2008 and WY2009 (Table 2.1). The precipitation gages in the Providence Creek watersheds2 4

are at 1750 m and 1985 m, while the gages in the Bull Creek watersheds are at 2195 m and 2463 m. Annual erosivity was calculated. Regression equations between elevation and either annual precipitation or annual erosivity were calculated separately for the Providence Creek and Bull Creek watersheds, and these equations were used to calcul ate the annual precipitation and erosivity for each of the hillslopes and road segments where sediment production was being monitored. In WY2009 the data for the lower Bull Creek precipitation gage were incomplete, so data from the upper gage were used fo r all of the

sites in the Bull Creek watersheds.

2.4.3. Hillslope sediment production and characteristics Hillslope sediment production and characteristics were measured for 9

- 18 undisturbed convergent hillslopes in KREW and 10 hillslopes in José Basin. Sediment production was measured by installing a sediment fence in each convergent swale (Figure 2.5). These were constructed of a geotextile fabric attached to 1.2 m long pieces of 1.3 cm diameter rebar that were pounded 0.3

- 0.5 m into the ground (Robic haud and Brown, 2002). The leading edge of the fabric was attached to the ground with landscape staples to prevent underflow. Annual sediment production was determined by removing and weighing the sediment captured in each fence to the nearest 0.5 kg. Two representative samples of this material were analyzed for percent moisture (Gardner, 1986) and percent organic matter (Ben

- dor and Banin, 1989). The mean moisture and organic matter values from each fence were used to convert the field weights to a dr y mass of mineral sediment. Annual25

sediment production was the dry mass of mineral sediment divided by the contributing

area. Hillslope characteristics were measured and related to sediment production (Table 2.2). The drainage area for each hillslope w as determined by walking and flagging the perimeter and then recording these points with a GPS and downloading these data into ArcMap. The axis and sideslope gradients were measured with a clinometer and the axis length was measured with a cloth tape. Th e dominant soil type was determined by digging a hole up to approximately one meter deep to observe whether there was the

distinctive red

- colored B horizon of a Holland soil. Soil type was grouped into either Holland or other. Other soil types included t he Shaver, Tollhouse, and Chawanakee series (USDA, 1983). The thickness of the O horizon was measured at three evenly

- spaced locations along each of three evenly

- spaced lateral transects. Percent cover was determined by classifying the surface at a minimu m of 100 systematically

- spaced points along the three transects using the categories listed in Table 2.2. Sediment production was measured for ten hillslopes in José Basin in WY2008 and WY2009 (Table 2.3). Three hillslopes were in Holland soil and seven hillslopes were in other soil types. Sediment production also was measured from 9

- 10 hillslopes in

the Providence Creek watersheds and 6

- 8 hillslopes in the Bull Creek watersheds in WY2008 and WY2009 (Table 2.4).26

2.4.4. Road sediment production

Sedi ment production from native surface road segments with a well

- defined drainage area and a single outlet was measured using sediment fences (Robichaud and Brown, 2002) (Figure 2.6). When necessary, additional fences were constructed directly downslope of t he original fence to increase storage capacity and catch efficiency. The sediment production rates were calculated in the same manner as described for the hillslopes, assuming that all the sediment was derived from the road.

Sediment fences in the Provi dence and Bull Creek watersheds were installed by Colorado State University students prior to the current study, and annual sediment production rates for road segments in the Providence Creek watersheds were measured for WY2008 and WY2009 (Table 2.4). In José Basin road sediment production was

measured from 5

- 12 segments in other soil types and 8

- 18 segments in Holland soil in WY2008 and WY2009 (Table 2.3). More than half of the sediment fences in José Basin overtopped in WY2008, and sediment production f rom overtopped fences were not included in the sample sizes or the mean sediment production rates.

2.4.5. Road segment characteristics Key characteristics were measured or classified for each road segment with a sediment fence (Table 2.5). The length of each segment was measured with a meter wheel. The active width is the width of the road that is regularly driven on, while the total width is the width from the bottom of the cutslope to the top of the fillslope. Road segment area was the segment lengt h times the active width. Segment slope was27

measured with a clinometer for each change of slope within the segment, and the segment slope was the length

- weighted slope. The percent surface cover was determined by classifying the surface at a

minimum of 100 systematically spaced points sampled along a zigzag transect on the active road surface. Each point was classified as bare soil, gravel (defined as rock with a secondary axis greater than 1.0 cm), litter, or live vegetation. Native surface segments

w ere defined by having less than 20% gravel cover. Traffic levels were estimated by determining the branch order of the road relative to a main road. The traffic level of each segment was classified as very low, indicating that vehicles very rarely travell ed on the road, low, medium, or high. Drain types and drain features were classified following the categories in Table 2.6. The elevation and location of the drainage point of each segment was determined using a GPS unit. The soil type of the segment wa s determined for each segment in José Basin by using soil maps and verifying the classification in the field. Soil types were grouped into either Holland or other, which included the Shaver, Tollhouse, and Chawanakee series (USDA, 1983). Road segment cha racteristics in the Providence and Bull Creek watersheds were measured by A. Korte (in preparation) prior to this study, though road surface cover was

re

- measured in summer 2009.

2.4.6. Road surveys Detailed road surveys were conducted on 10.9 km of roads in José Basin between 2007 and 2009 to: 1) determine how well the fenced segments represented the road network in José Basin; and 2) estimate total annual sediment production and delivery28

from native surface roads in José Basin. The detailed surveys meas ured or estimated the same characteristics as were observed on road segments with sediment fences (Table 2.5), with the exception that the percent bare soil and gravel on the surface of the road were estimated in the surveys rather than determined with cov er counts. The sections to be surveyed in José Basin were identified by breaking the road network into 269 sections that were 300 to 900 m long using ArcGIS, and selecting 20% of the road sections using a random number generator (Figure 2.7). The selecte d sections were surveyed unless they were paved or not accessible as they were on private land holdings. Surveys were conducted on all of the road segments in the Providence Creek and Bull Creek watersheds by A. Korte (in preparation) prior to the current study.

2.4.7. Road sediment delivery The potential for runoff and sediment to be delivered to the stream network for each monitored and surveyed road segment was evaluated by identifying and following any sediment plume or drainage rill, hereafter refe rred to as drainage features (Coe, 2006). The length and slope of each drainage feature was measured (Table 2.5). The roughness of the drainage pathway was classified from one to four, with class one being very smooth pathways and class four paths having some combination of live vegetation, large woody debris, or larger litter accumulations, such as pine cones, to disrupt the flow and effectively trap the runoff and sediment. The presence or absence of pushouts at the drainage point of the road segment was recorded (Table 2.5). Pushouts were classified as no longer intact either if they were filled with too much deposition for the water to continue to drain at that point, or the road29

drainage was no longer directed to the pushout. The presence or absen ce of large, round rocks used as armoring at the drainage point or a small channel over the road was also recorded. This drain armoring was classified as intact if it remained in the correct location to slow flow and trap sediment, and it also was noted w hether the armoring was buried under sediment. The locations of culverts were noted, and the percent of the culvert that was plugged with sediment or large woody debris was estimated. The presence and volume of scour at the downstream end of each culvert was measured. Each road segment was also put in a connectivity class according to the drainage feature length and whether it extended to within 10 m of a stream (Table 2.7). Segments with a connectivity class of one have very little potential to delive r runoff and sediment to a stream channel, while segments with a connectivity class of four have a high delivery potential.

2.4.8. Comparison to WEPP:Road The measured sediment production values for the native surface road segments in

José Basin in WY2 009 were compared to the values predicted by WEPP:Road (n = 43). The northing, westing, and elevation for each fence as demarcated by a GPS unit were entered into the PRISM model for calculating the mean monthly rainfall for each native surface segment wi th a sediment fence. Segments on Holland soil were classified as clay loam, while segments on other soil types were classified as loam. The road surface for each segment was classified as native. Percent rock was calculated from the cover counts

conduct ed on each monitored segment, and the road gradient, length, and width were all measured in the field. Insloped segments and segments that were a mixture of insloped30

and planar were classified as ―insloped with a bare ditch‖. Outsloped segments with

berm s and planar segments were classified as ―outslope, rutted‖ since these segments generally had at least some wheel ruts.

. Low and medium traffic levels were set as low, while very low traffic levels were set as none. The length of the simulated climate was set to one year. WEPP:Road was validated by comparing predicted rates to measured

values.

2.4.9. Statistical analysis The main dependent variable was the annual sediment production rate from hillslopes and native surface road segments (kg m - 2 yr - 1 ). Pairwise comparisons of hillslope and road segment sediment production rates for WY2008 and WY2009 were made between each of the study areas: José Basin, the Providence Creek watersheds, and the Bull Creek watersheds. The effect of soil type on hillslop e and road sediment production in José Basin also was evaluated by pairwise comparisons between Holland and other soil types for WY2008 and WY2009. The validity of each comparison was assessed by comparing other key variables (e.g., slope, area, percent b are soil) between

groups. ANOVA tables and regressions were used to assess the relationships between each independent variable and the measured sediment production rates from native surface road segments in José Basin from WY2008 and WY2009. A multivari ate linear regression model to predict sediment production from native surface road segments in José Basin was constructed using a backward elimination procedure and a selection31

criteria of α = 0.10. The multivariate model was evaluated by comparing predi cted sediment production rates to measured values.

2.5. Results 2.5.1. Precipitation

José Basin Mean annual precipitation for the past 95 years at the Auberry rain gage is 611 mm (California Department of Water Resources, 2010). In WY2008 the annual

pr ecipitation at Auberry was only 458 mm or 75% of the mean. Mean precipitation for the four functioning rain gages in José Basin in WY2008 was 519 mm (standard deviation (s.d.) = 50 mm), or approximately 60 mm more than at Auberry (Figure 2.8). Annual pre cipitation was not significantly correlated with elevation in José Basin for WY2008 (R 2 = 0.03, p = 0.84). The mean erosivity of the four gages in WY2008 was

630 MJ ha - 1 mm hr - 1 (s.d. = 90 MJ ha - 1 mm hr - 1 ). In WY2009 the annual precipitation at Auberry wa s 526 mm, or 86% of the mean. Mean precipitation for the three functioning rain gages in José Basin was 554 mm, which was 35 mm more than at Auberry, but the values in José Basin were more variable than in WY2008 as the standard deviation was 139 mm. Aga in the measured precipitation in José Basin was not significantly correlated with elevation (R 2 = 0.81, p = 0.29). The mean erosivity in WY2009 was 390 MJ ha - 1 mm hr - 1 (s.d. = 210 MJ ha - 1 mm hr - 1 ), or

38% less than the value in WY2008. T here was no signi ficant difference in annual precipitation between WY2008 and WY2009 (p = 0.66), but annual erosivity in WY2008 was significantly lower than the WY2009 value (p = 0.09).32

Providence Creek and Bull Creek watersheds, KREW Precipitation in the KREW watershed s falls largely as snow, although there can

be summer rain storms as well as rain

- on

- snow events. The mean annual precipitation for the four KREW stations is 1240 mm per year (Korte and MacDonald, 2007), or more than double the mean value for the Auberry station. In WY2008 the Providence Creek watersheds received 83% of the mean annual precipitation, as compared to annual precipitation measuring 75% of the mean value at Auberry. Total precipitation was only 913 mm at the lowest gage, while the other thre e gages all had very similar totals of 1116 to 1148 mm, regardless of elevation (Figure 2.9). Annual precipitation was assumed to be directly correlated with elevation in both the Providence Creek and the Bull Creek

watersheds in WY2008.

In WY2009 the me an precipitation at the Providence Creek rain gages was 962 mm (s.d. = 6 mm), or 78% of the mean annual precipitation for KREW (Figure 2.9). Precipitation at the upper Bull Creek rain gage was 1081 mm, which was only 12% more than the mean precipitation i n the Providence Creek watersheds. Again, a direct correlation was assumed between annual precipitation and elevation in the Providence Creek watersheds. However, the lower Bull Creek precipitation gage did not collect sufficient data due to equipment ma lfunctions, and so it was assumed that all sediment fences in the Bull Creek watersheds received the same precipitation as the Upper Bull Creek rain gage.33

2.5.2. Hillslope characteristics and sediment production

José Basin The mean contributing area o f the ten hillslopes with sediment fences in José Basin was 0.42 ha, but the standard deviation was relatively large at 0.32 ha (Table 2.8, Appendix A). The mean elevation of the ten sediment fences was 1100 m (s.d. = 107 m), and values ranged from 947 m to 1225 m. The hillslope surface areas were typically well covered, as litter covered more than half of the ground surface (mean = 56%, s.d. = 11%), while live vegetation averaged 25% (s.d. = 12%) and woody debris averaged 13% (s.d. = 7%). Percent bare s oil and rock accounted for only 4% and 2% of the surface on average, respectively. Seven hillslopes were classified as other soil types and only three hillslopes were in Holland soil. Hillslopes in Holland soils and other soil types were not significantl y different in area, slope, or surface cover. Mean hillslope sediment production in José Basin was 7.4 x 10 - 3 kg m - 2 (s.d. = 2.1

x 10 - 2 kg m - 2 ) in WY2008 (Table 2.8). The mean sediment production rate for the three hillslopes in Holland soil was only 6. 7 x 10 - 5 kg m - 2 (s.d. = 9.4 x 10 - 5 kg m - 2 ), or more than three orders of magnitude lower than the mean rate for other soil types (1.1 x 10 - 2 kg

m - 2 , s.d. = 2.5 x 10 - 2 kg m - 2 ) (Appendix A). The latter value was highly skewed by the sediment production rate for one hillslope, JHS10, which was an order of magnitude higher than any other hillslope. The relatively high variability and small number of hillslopes on Holland soil meant that there was no significant difference in hillslope sediment production rate s with soil type (p = 0.50). In WY2009 no sediment was produced from any of the hillslopes in José Basin, which exempl ifies the large potential34

inter annual variability of hillslope sediment production as well as the typically low

erosion rates found in fo rests with high percent surface cover.

Providence Creek and Bull Creek watersheds, KREW The mean elevation of the hillslope sediment fences in the Providence Creek watersheds was 1915 m (s.d. = 54 m) (Appendix B), or 815 m higher than the mean

elevation of the hillslope fences in José Basin, while the hillslope sediment fences in the

Bull Creek watersheds had a mean ele vation of 2320 m (s.d. = 131 m) (Appendix C). The mean area of the monitored hillslopes in the Providence Creek watersheds was 0.55 ha ( s.d. = 0.37 ha), which was only slightly larger than the mean area for hillslopes in José Basin. However, the mean area for the monitored hillslopes in the Bull Creek watersheds was nearly four times the mean value for the Providence Creek hillslopes (p < 0.0001). In WY2008 the mean sediment production rate for the ten hillslopes in the

Providence Creek watershed was 7.9 x 10 - 4 kg m - 2 (s.d. = 1.0 x 10 - 3 kg m - 2 ) (Appendix B), which was an order of magnitude lower than the mean value in José Basin. The me an sediment production rate for the four hillslopes in the Bull Creek watersheds was 58% of the value from the Providence Creek watersheds, but this difference was not significant (p = 0.43) (Appendix C). There was no significant difference in hillslope s ediment production between José Basin and either the Providence Creek or the Bull Creek watersheds in WY2008 (p ≥ 0.33). In WY2009 the mean hillslope sediment production rate in the Providence Creek

watersheds was 7.0 x 10 - 6 kg m - 2 (s.d. = 2.2 x 10 - 5 kg m - 2 ), which was two orders of35

magnitude lower than the value the previous year. The mean value in the Bull Creek watersheds was 54 times the mean value for the Providence Creek watersheds, but this difference was not significant (p = 0.23) (Table 2.8). T he high mean value for the Bull Creek hillslopes was largely due to one hillslope, BH1, which produced 2.5 x 10 - 3 kg m - 2

, and was one of only two hillslopes in the Bull Creek watersheds that produced sediment in WY2009. Similarly to WY2008, there was no s ignificant difference in sediment production between hillslopes in José Basin and hillslopes in either the Providence Creek or the Bull Creek watersheds in WY2009 (p ≥ 0.22 ).

2.5.3. Road segment characteristics and sediment production

José Basin

Native surface roads accounted for 7.2 km or 66% of the surveyed road length. The mean length of the 133 native surface segments was 82 m, but this varied widely with a standard deviation of 124 m. The median value of 51 m is perhaps a better representation of the native surface segments in José Basin, as the mean value was skewed by the longest segment, which was 1.2 kilometers long. When weighted by length, t he mean width of the native surface roads in José Basin was 2.5 m (s.d. = 0.5 m).

The mean length

- we ighted slope was 8% (s.d. = 4%). Seventy

- six percent of the segments were planar, and 21% were a combination of planar, outsloped with a berm, and insloped. The remaining segments were outsloped with a berm. The majority of the segments (65%) had either waterbars or dips as the main drainage feature, and none of the segments had diffuse drainage. Three of the native surface segments had stream crossings across road surface. Twenty

- nine percent of the native surface road length had36

fillslope erosion at the drainage point. Of the 10.8 km, 1.4 km did not have any waterbars or dips as part of their drainage system. Of the remaining 9.4 km, 51% of the road length had effective waterbars or dips, while the remaining 49% had ineffective waterbars or dips. T here were a total of 77 ineffective bars or dips on the 10.8 km of road, for a total of seven ineffective bars or dips per kilometer of native surface road. Segments were mostly bare, as the mean surface cover due to gravel, litter, or vegetation was only 8% (s.d. = 14%). Forty

- one percent of the surveyed road length had little to no traffic, while 26% was classified as having low traffic, and 33% was classified as having medium traffic. Thirty

- eight percent of the surveyed road length was on

Holland soil

. Rill erosion with a mean depth of at least five centimeters was observed on 45% of the native surface segments surveyed in José Basin. The mean segment length of the segments without rills was 61 m (s.d. = 50 m), while the value for segments with rills was nearly doub le at 116 m (s.d. = 114 m) (p = 0.004 ). The total rill length was 2.7 km, for an overall rill to road length ratio of 0.38. The mean rill length was 72 m (s.d. = 107 m)

and the mean rill volume was 5.7 m 3 (s.d. = 13.7 m 3 ). The mean slope weighted by

seg ment length for segments with rills was 10 %, while the mean slope for segments

with out rills was only 4 % (p < 0.0001 ). The mean elevation of the 34 native surface road segments with sediment fences in José Basin was 1056 m (s.d. = 82 m), a nd the range was from 913 m to 1254 m. The native surface road segments with sediment fences in José Basin had a mean length of 44 m (s.d. = 16 m), which is 51% of the mean length of the surveyed segments (p = 0.08). This significant difference is not su rprising given that the segments selected for37

monitoring are required to have a discrete top and bottom, and that very few of the monitored segments had broken waterbars in comparison to the surveyed segments. The mean slope of the native surface segment s with sediment fences in José Basin was 9% (s.d. = 3%), and the range was from 2% to 16%. The mean value of 9% is significantly higher than the mean slope of the surveyed segments (p < 0.0001). The much larger area but lower slope of the surveyed segmen ts resulted in a mean area*slope factor that was only 17% larger than the segments with sediment fences (p = 0.55). The segments with sediment fences in José Basin averaged 30% (s.d. = 15%) surface cover or 70% bare soil, and this was significantly less b are soil than the surveyed segments (p < 0.0001). Only 5% of the monitored segments had very little to no traffic, while 52% were characterized as having a low amount of traffic. The remaining 43% had a medium

traffic level. In WY2008 the mean sediment p roduction rate for the 12 native surface road segments in José Basin was 1.4 kg m - 2 (s.d. = 2.3 kg m - 2 ) (Figure 2.10). Production rates varied widely, with the lowest rate occurring on JNO6 (0.042 kg m - 2 ) and the highest on JBT14 (7.9 kg m - 2 ). Relatively few segments produced the majority of the sediment, with 25% of the road length monitored producing 75% of the sediment (Figure 2.11). In WY2009 the mean sediment production rate for the 29 native surface road segments in José Basin increased by 50% to 2. 1 kg m - 2 (s.d. = 3.1 kg m - 2 ) (Figure 2.10). Sediment production values varied by even more than in WY2008, as rates ranged from 0.0050 to 12.9 kg m - 2 . This high variability helps explain why sediment production from native surface road segments was not s ignificantly different between WY2008 and WY2009 despite the 50% increase (p = 0.51) (Figure 2.10). As in WY2009, r elatively38

few segments produced large amounts of sediment in WY2009, with 25% of the road length monitored producing 75% of the sediment (Fi gure 2.11). Stratification of the data by soil type showed that there were 21 road segments with sediment fences in Holland soil and 12 road segments in other soil types. The mean elevation of the Holland segments with sediment fences was 1109 m (s.d. = 6 6 m) , while the mean value for the segments in other soil was 982 m (s.d. = 52 m) (p < 0.0001). However, elevation within José Basin was not significantly correlated to sediment production (p = 0.92). The mean length and area of segments were similar for both soil types, while the mean slope of the segments in Holland soil was 10% (s.d. = 3%) as compared to the mean value of 8% (s.d. = 3%) for the segments in other soil, and this difference was nearly significant (p = 0.11). The segments in Holland soil averaged 65% bare soil, which was significantly less than the mean of 79% for the segments in other soil types (p = 0.0008). In WY2008 the mean sediment production rate for the five native surface segments in other soil types was 0.5 kg m - 2 (s.d. = 0.7 k g m - 2 ) (Figure 2.12). Mean sediment production for the eight road segments in Holland soil averaged 1.9 kg m - 2 , or nearly four times higher, but the standard deviation of 2.7 kg m - 2 was 42% larger than the mean (Appendix D). The small sample sizes and hi gh variability meant that road sediment production did not significantly differ by soil type for WY2008 (p = 0.28). In WY2009 the mean sediment production rate for the 12 native surface segments in other soil types was 2.7 kg m - 2 (s.d. = 4.1 kg m - 2 ), wh ich was 5.4 times higher than in WY2008 (p = 0.25) (Figure 2.12). Almost half of this increase is due to JNO3, which produced 12.9 kg m - 2 in WY2009. If this segment is excluded, the mean sediment39

production rate drops to 1.7 kg m - 2 (s.d. = 2.4 kg m - 2 ), a lthough this is still 3.4 times higher than the mean value from WY2008. The mean sediment production rate for the 18 road segments in Holland soil was 1.6 kg m - 2 yr - 1 , which was 16% lower than WY2008 (Figure 2.12). The explanation for the surprising cont rast between the increase in sediment production from WY2008 to WY2009 for segments in other soil types as compared to the decrease in values for segments in Holland soil is unknown. As in WY2008, road sediment production in WY2009 was not significantly d ifferent by soil type (p = 0.32). For the native surface segments in José Basin, sediment production was significantly correlated with segment slope (R 2 = 0.11; p = 0.03) (Figure 2.13). When sediment production was normalized by segment slope to accou nt for the significantly steeper segments in Holland soil than in other soil types, the road segments on Holland soil still did not produce significantly more sediment than the road segments on other soil types for WY2008 or WY2009 (p = 0.24 and p = 0.21, respectively).

Providence Creek and Bull Creek watersheds, KREW In the Providence Creek watersheds, the mean elevation of the six native surface road segments was 1859 (s.d. = 85 m), which is 800 m higher than the mean elevation of the native surface segm ents in José Basin. The mean area and slope of the segments with sediment fences in the Providence Creek watersheds generally were similar to the mean values in José Basin (Table 2.9). The main difference was that the native surface segments in the Provi dence Creek watersheds averaged only 48% bare soil (s.d. = 17%)40

as compared to 70% in José Basin (p < 0.0001). The remaining 52% was comprised of 35% litter (s.d. = 22%), 10% gravel (s.d. = 10%), and 7% live vegetation (s.d. = 6%).

In WY2008 the mean se diment production rate for the six native surface road segments in the Providence Creek watersheds was 0.12 kg m - 2 (s.d. = 0.14 kg m - 2 ) (Figure 2.10; Appendix E), and ranged over an order of magnitude from 0.01 to 0.4 kg

m - 2 . The mean rate was an order o f magnitude lower than mean rate from native surface segments in José Basin, but the mean rates were not significantly different (p = 0.22) due to the high variability between segments. The mean value of 0.14 kg m - 2 (s.d. = 0.12 kg m - 2 ) in WY2009 was v ery similar to the previous year (Figure 2.10). Similar to WY2008, the mean value in the Providence Creek watersheds was only 7% of the mean rate in José Basin. However, again due to high variability, there was no significant difference between values in the Providence Creek watersheds and José Basin (p = 0.14). In the Bull Creek watersheds, the mean elevation of the nine native surface road segments was 2292 m (s.d. = 62 m), 433 m higher than the mean elevation in the

Providence Creek watersheds. The me an length was 57 m (s.d. = 25 m), and this was significantly longer than the mean segment length in José Basin (p = 0.01) and nearly significantly longer than the mean segment length in the Providence Creek watersheds (p = 0.12). Mean segment slope in the Bull Creek watersheds was 9% (s.d. = 3%), which is

similar to the values in both José Basin and the Providence Creek watersheds. Percent bare soil for the native surface segments in the Bull Creek watersheds averaged 53% (s.d. = 21%), which was similar t o the mean value in the Providence Creek watersheds. However, the mean gravel cover of 7% (s.d. = 5%) was significantly more than the mean41

value of 2% in the Providence Creek watersheds (s.d. = 1%) (p = 0.001) and nearly significantly more than the mean g ravel cover of 4% in José Basin (s.d. = 8%) (p = 0.11). The mean road sediment production rate in the Bull Creek watersheds was 0.042 kg m - 2 (s.d. = 0.067 kg m - 2 ) in WY2008 (Appendix F), or 35% of the mean value from

the Providence Creek watersheds and on ly 3% of the mean value from José Basin. The differences between road sediment production in the Bull Creek watersheds and the Providence Creek watersheds and José Basin were nearly significant in WY2008 at p = 0.19 and p = 0.11, respectively.

In WY2009 the mean sediment production rate for native surface road segments in the Bull Creek watersheds was 0.23 kg m - 2 (s.d. = 0.27 kg m - 2 ), which was 5.5 times the value from WY2008; this increase was nearly identical to the increase for the hillslope sediment fences in the Bull Creek watersheds in WY2009. Unlike the previous year, road sediment production in the Bull Creek watersheds in WY2009 was 38% greater than in the Providence Creek watersheds, though this difference was not significant (p = 0.48). The m ean road sediment production of 0.23 kg m 2 in the Bull Creek watersheds was only 9% of the mean value for José Basin, and this difference was significant (p = 0.09).

2.5.4. Road sediment delivery

José Basin Forty

- five percent of the 7.2 km of surveyed n ative surface road length or 42% of the segments had no visible drainage feature (Figure 2.14). Sediment plumes accounted for the majority of the drainage features, although occasionally there was a drainage rill.42

Drainage features tended to be relativel y short, as only seven of the 57 segments, or 16% of the road length, had drainage features greater than 20 m long. The longest drainage feature in José Basin was 105 m long, and this came from a 246 m long segment. Forty

- six percent of the native surfa ce road length in José Basin had a connectivity class of one, while 30% of the road length was directly connected to the stream network (Figure 2.15). The relatively high connectivity given the average plume length of only 16 m can be explained by the pro ximity of many roads to the stream channel. Of the 14 surveyed segments that were connected to a stream, seven segments or 500 m of road had plume lengths of zero meters, as the discharge points were directly

into a stream. The effect of soil type on sed iment delivery was evaluated from the detailed data for 38 road segments prior to installing sediment fences. Thirteen of these segments were in other soil types, and 25 were on Holland soil. Twelve of the 13 segments in other soil types had a drainage f

eature, and the mean drainage feature length was 25 m (s.d. = 19 m) with a range of three to 60 m. Thirty percent of the road length on other soil types had a connectivity class of one, while 28% of the road length was connected to the stream (Figure 2.16 ). Similarly to the segments in other soil types, only two of the 25 segments in Holland soil had no visible drainage features. Also similarly to segments in other soil types, the mean drainage feature length for segments in Holland soil was 27 m (s.d. = 17 m) and values ranged from six to 65 m. The similarities in plume length between segments in other soil types and segments in Holland soil indicate that native surface segments on Holland soil are no more likely to have a longer drainage feature than43

s egments in other soil types. However, the percent of connected road length on Holland soil was 18%, which was slightly lower than the value for other soil types (Figure 2.16). This 10% difference is likely due to a higher proximity of other soil types to stream

channels than Holland soils.

Providence Creek watersheds In the Providence Creek watersheds, 27% of the 7.8 km of native surface road length had no visible drainage feature, and this is lower than the value of 45% for native surface segments in José Basin (Figure 2.14). However, only 3% of the native surface road length in the Providence Creek watersheds was directly connected to the stream network, which is only a tenth of the value for José Basin (Figure 2.15).

2.5.5. Modeling road sediment production and delivery in José Basin. 2.5.5.1. Predicting sediment production from native surface segments in José Basin The univariate analysis showed that sediment production was significantly and positively correlated with segment slope, the length of rills on the segment, and the volume of rills on the segment (Table 2.10). Rill length was the most significant variable (p = 0.0004) and explained 39% of the variability in annual road sediment production. The empirical multivariate model constructed u sing the survey data to predict sediment production from the native surface road segments in José Basin included rill length (R in m), area (A in m 2 ), percent Holland B horizon on the surface of the road segment (B), and annual precipitation (P in mm):

SP = 0.010 + 0.11*R

– 0.016*A

– 0.029*B + 0.0056*P (equation 2.2)44

where SP equals the sediment production rate in kg m - 2 yr - 1 (R = 0.59) (Table 2.11). The

model tended to over

- estimate the lower sediment production rates and under

- estimate the higher sediment production rates (Figure 2.17). The predicted sediment production

rates from the multivariate model again confirm that relatively few segments typically produce a large amount of sediment, as only 12% of the segments were predicted to have sediment production rates greater than 4 kg m - 2 yr - 1 . The variables included did make physical sense except that sediment production decreased with increasing segment area. Equation 2.2 could not be used to predict road sediment production for all the surveyed road segments because the surveys did not attempt to estimate the percent of

Holland B horizon on the road surface. The simplified equation used to predict road sediment production from the surveyed native surface segments was:

SP = 0.010

– 0.016*A + 0.0056*P + 0.11*R (equation 2.3),

which has an R 2 of 0.49.

2.5.5.2. Total potential sediment produced and delivered from native surface segments in

José Basin The road survey showed that 42% of the 159 km of roads in José Basin were

na tive surface, 18% were gravel surface, and 41% were paved. Mean annual precipitation for the seven gage

- years of data in José Basin was 534 mm. Using the characteristics measured in the random survey and equation 2.3, t he predicted mean sediment producti on rate for the 11 km of surveyed native surface roads in José Basin was 1.8 kg m - 2 yr - 1 . Given that there are an estimated 67 km of native surface roads in45

José Basin, the estimated total sediment production is approximately 680 metric tons per

water yea r, or 10 metric tons per kilometer of road length. The road survey showed that 30% of the native surface road length in José Basin was directly connected to a stream. Multiplying this percentage by the estimated total sediment production indicates that u p to 210 metric tons of sediment from native surface roads are being delivered each year to the stream network in José Basin.

2.5.5.3. Comparison of WEPP:Road predictions to measured values in José Basin WEPP:Road poorly predicted sediment production rat es for native surface road segments in José Basin (R 2 = 0.03, n = 43) (Figure 2.18). The general tendency was for

WEPP:Road to under

- predict annual sediment production, as the predicted sediment production rates were less than half of the measured values for 74% of the data. For 30% of the data the predicted sediment production rates were more than an order of magnitude

lower than the observed values.

2.6. Discussion 2.6.1. Effects of climate on sediment production The comparison of data between study sites provides a unique opportunity to evaluate the effect of elevation and climate on hillslope and road sediment production. There were no significant differences between hillslope sediment production rates in José Basin, the Providence Creek watershed s, or the Bull Creek watersheds in WY2008, and in WY2009 the highest elevation Bull Creek hillslopes produced the most sediment. The dense cover of vegetation and duff on the hillslopes protects the surface from rainsplash46

erosion and increases infiltrati on, reducing erosive overland flow. The ability of ground

cover to minimize surface erosion rates applies whether the surface is in a rain or snow

dominated area. Roads are more susceptible to rainsplash detachment and erosive overland flow,

and therefo re have much higher sediment production rates than hillslopes. The lack of cover on a native road surface also makes the surface more susceptible to an increase in

erosion with an increase in the ratio of rain to snow . Areas with much higher annual preci pitation and annual erosivities generally have much higher road sediment production rates. On the Olympic Peninsula mean annual precipitation is 6.4 times the value in José Basin, and the mean sediment production rate was 41 Mg km - 1 yr - 1 , or four times th e mean rate in José Basin (Table 2.12). The mean annual precipitation on St. John in the U.S. Virgin Islands is 1.5 to 2.3 times the value in José Basin, while road sediment production rates were 5

- 15 kg - 2 m - 2 yr - 1 (Ramos

- Scharrón and MacDonald, 2005) or 2.8 to 8.3 times the mean rate in José Basin (Table 2.12). The much higher erosion rates on St. John can be attributed to the annual erosivity on St. John being approximately 25 times higher than in José Basin (Ramos

- Scharrón and MacDonald, 2005), and th is

indicates the potentially greater usefulness of erosivity for predict ing erosion than total precipitation. In northwestern California, the Jackson Demonstration State Forest receives approximately 1400 mm yr - 1 of precipitation, which is twice the valu e for José Basin , but the annual erosivities are not as different (Renard et al., 1997) . As the road sediment production rates of 0.5 to 4 kg m - 2 yr - 1 (Barrett and Tomberlin, 2006) were similar to47

values in José Basin, and this again indicates the greater utility of erosivity relative to total precipitation

. In the Sierra, like many areas, an increase in elevation typically increases the amount of snow relative to rain. This decreases the erosivity, as snowfall has minimal erosive energy, precipitation intensities are lower, and snowmelt rates are low in comparison to rainfall intensities, resulting in less overland flow. Hence road sediment production rates are typically lower in areas with snow or mixed snow

- and

- rain. Mean annual precipitation in the Providence Creek watersheds in WY2008 and WY2009 was approximately twice the value in José Basin, but due to the preponderance of snow, the annual erosivity was much lower. This explains why the mean sediment production rate

in the Providence Creek water sheds for native surface roads was 0.13 kg m - 2 yr - 1 (s.d. = 0.13 kg m - 2 yr - 1 ), or just 7 % of the mean value in José Basin. In the higher elevation Bull Creek watersheds the mean road sediment production

rate in WY2008 was 35% of the value from the Provid ence Creek watersheds, while in WY2009 the mean road sediment production rate in the Bull Creek watersheds was 1.6 times the value in the Providence Creek watersheds. The higher sediment production in

the Bull Creek watersheds in WY2009 can be attributed to a relatively rare localized summer rainstorm, which can drastically increase the annual erosivity. Road sediment production rates in the Eldorado National Forest (ENF) (Figure 2.1), which has a mixed rain

- on

- snow climate, provide further insight into the role of elevation and climate on road sediment production. On the ENF annual precipitation was 2.5 times higher than in José Basin, but the study area was snow dominated and the mean road sediment production rate of 0.22 to 0.81 kg m - 2 yr - 1 (Coe, 2006 ) was only 12

- 45% of48

the mean value from José Basin. Similarly, annual precipitation in the Idaho batholith i s approximately 720 mm, with 60% fal ling as snow, and t he mean sediment production rate from native surface road segments was 0.48 kg m - 2 yr - 1 (Me gahan, 1974)

. This is very similar to the mean value f or the ENF but only 27% of the mean value from José

Basin. The lower road sediment production rate s on the ENF and the Idaho batholith can be explained by the lower erosivity due to the greater propor tion of snow. These comparisons to other studies in rain, rain

- on

- snow, and snow dominated climates suggest that road sediment production varies with annual precipitation in rain dominated areas , but that annual erosivity is a much better predictor of roa d erosion rates when the precipitation is a mixture of rain and snow

. The exact effect of potential global climate change on the amount of precipitation in the Southern Sierra is uncertain, but overall global warming is a potential outcome (IPCC, 2007). Warmer temperatures will increase the rain to snow ratio in the southern Sierra and other mountainous areas. This warming will increase sediment production from native surface roads in the KREW watersheds, which will reduce the current 10

- fold

difference in mean sediment production rates between the mixed

- climate Providence Creek watersheds and the rain dominated José Basin. The potential shift to more rain the Providence Creek watersheds also will likely increase sediment delivery by increasing

the amou nt of runoff and erosion from native surface road segments. Similar increases can be expected in other areas that are at or just above the rain

- snow boundary.49

2.6.2. Assessing and reducing road sediment production in José Basin

A crude estimate of the relative importance of unpaved roads to total sediment production in José Basin can be made by comparing the estimated hillslope sediment yields to the sediment production and delivery from native surface roads. The mean sediment production rate for hills lopes in José Basin was only 0.0037 kg m - 2 yr - 1 (s.d. = 0.015 kg m - 2 yr - 1 ). If this rate is multiplied by the area of the basin and 100% connectivity is assumed, the background sediment yield is 290 tons yr - 1

. Road surveys

and t he multivariate road sedim ent production model predicted that native surface roads would generate 680 tons of sediment per year. Since 30% of the native surface road length is connected to a stream, native surface segments in José Basin could deliver up to 210 tons of sediment per year to the stream network. This is 72% of the estimated hillslope sediment yield, indicating that road erosion is a major contributor of sediment to streams in José Basin, especially since they occupy less than one percent of the land area. Unpaved road s also have been identified as a major source of sediment in forested watersheds in other locations (Reid and Dunne, 1984; Swift, 1988; Bilby et al., 1989; Luce and Black, 1999; Ketcheson et al., 1999; Coe, 2006). On St. John, unpaved roads

delivered more sediment to the streams than all of the natural sources, including bank erosion, treethrow, and erosion from undisturbed hillslopes (Ramos

- Scharrón and MacDonald, 2005). In Australia unsealed roads and logging tracks were identified as the most hydrologi cally active areas within a logged forest, and these are often significant sediment sources (Croke and Hairsine, 2006). Because excessive sediment reduces water and habitat quality (Bilby et al., 1989; Ziegler and Giambelluca, 1997; Kolka and Smidt,50

2004) , forest managers need to consider means for reducing road sediment production and delivery. The results presented in this study can help guide best management practices for reducing road sediment production and delivery in José Basin. The significant var iables in the multivariate model for predicting sediment production from native surface road segments were rill length (m), annual precipitation (mm), segment area (m 2 ), and the percent Holland soil B horizon on the road surface (Table 2.11). The positive correlations of sediment production with rill length and annual precipitation make physical sense, and the former has direct implications for management. However, the negative coefficients for segment area and percent Holland soil B horizon merit further explanation. In WY2008 and WY2009 rilled segments respectively produced ten and six times more sediment per unit area than unrilled segments when normalized by slope (p <

0.0001 and p = 0.007 ) (Figure 2.19). Other studies have shown that surface runoff can detach and transport more sediment once it is channeled into a rill (Meyer et al., 1975; Loch and Donnellan, 1983; Poesen, 1987). These results indicate that rills are a major source of sediment from native surface road segments relative to rainsplas h and sheetwash erosion. Rilling readily occurs on native surface roads due to the depressions caused by tire tracks that concentrate the flow. The recognized management practice to reduce rilling and road sediment production is to restrict driving in we t conditions, and this study supports this practice. An analysis of the segments with rills versus segments without rills also can be used to pinpoint where rills are most likely to form, and hence when waterbars or the51

application of gravel could help mi nimize rilling . The mean segment area for rilled segments was 130 m 2 (s.d. = 50 m 2 ) as compared to 100 m 2 (s.d. = 40 m 2 ) for segments without rills. This was significant at p = 0.07, indicating that rills form on longer or wider segments. Rilled and unr illed segments were more clearly separated by the product of road segment area times segment slope, as the area*slope factor for rilled roads averaged 1330 m 2 m m - 1 (s.d. = 560 m 2 m m - 1 ) as compared to only 880 m 2 m m - 1 (s.d. =

560 m 2 m m - 1 ) for unrilled s egments (p = 0.02). This indicates that larger, steeper segments should be broken into smaller segments by installing waterbars when the area*slope factor exceeds about 1000 m 2 m m - 1

. Segment slope was a significant continuous variable in the univariate analysis, but

the R 2 was low and slope was not a significant variable in the multivariate model for predicting road sediment production. Figure 2.13 suggests a simple categorical

classification of sediment production versus slope, and Figure 2.20 shows t hat mean sediment production for segments with slopes greater than 7% was an order of magnitude higher than for segments with slopes less than 7% (p = 0.18 and 0.06 for WY2008 and

WY20 09, respectively) . This indicates that management practices to reduce s ediment production, such as graveling or installing waterbars, should focus on road segments that are steeper than 7%. The multivariate model predicted that road sediment production in José Basin is significantly correlated to annual precipitation (p = 0.0 6). Other studies also have shown that annual precipitation, or more importantly annual erosivity, is a significant variable in predicting road sediment production (Ramos

- Scharrón and MacDonald, 2005; Coe, 2006; Sugden and Woods, 2007; Welsh, 2008; Fu et al., 2010). This study shows that52

m anagement practices to reduce road sediment production are much more important in

rain dominated areas.

The multivariate model predict s a decrease in sediment production with

increa sing segment area, which is counter

- int uitive. However, this can be explained by the greater potential for sediment deposition on many of the larger segments. For segments with areas greater than 150 m 2 , the mean slope of the bottom ten meters averaged 6% (s.d. = 2%) as compared to 8% (s.d. = 3%) for the segments with areas less

than 100 m 2 , and this difference was significant at p = 0.04. Road segments with slopes less than 7% were already shown to have lower sediment producti on rates than segments steeper than 7%. These results indicate th at the flatter sections at the ends of the longer segments can act as de positional areas, and this can explain the negative correlation between segment area and sediment production in the multivariate model.

The multivari ate model also predicts a decreas e in sedi ment production with an increasing percent Holland B horizon on the road surface, but this is most likely a statistical artifact. As previously described, the Holland B horizon is a highly erodible layer, and in theory sediment production should increase with an increase in the percent B horizon. However, the univariate analysis did not find any correlation between sediment production and the percent B horizon, and there was no significant difference in sediment production between roads in Hollan d soil and roads in other soil types. According to the data gathered in this study, there is no clear justification for focusing

road sediment reduction efforts on Holland soils. The very large variability in sediment production rates between sites makes it inefficient to universally apply management practices to reduce road sediment53

production, as just a few segments often account for most of the road

- related sediment being delivered to the stream network. For example, segment JNO3 in José Basin had a

se diment production rate of 12.9 kg m 2 yr - 1 in WY2009, which was nearly an order of magnitude more than any of the other segments in either water year. JNO3 had an extensive rill system, with 53 m of rills on a 35 m long segment, giving it a higher rill

den sity than any other segment, and it had a moderate to high delivery potential. A best management practice to reduce sediment contributions from native surface road segments should begin with pinpointing the ―trouble‖ segments and road sections that are ap t to

deliver the most sediment to the stream network. The data collected in this thesis indicate that management efforts should focus on those segments with extensive rill erosion, segments with area*slope factors greater than 1000 m 2 m m - 1 , and segments with slopes greater than 7%. Sediment production on these segments can be redu ced through graveling or paving as examined in the next chapter. Sediment delivery can be reduced by installing waterbars that direct flow away from streams, which also will be examined in more detail in the following chapter.

2.7. Conclusions This project monitored hillslope and road sediment production in the low elevation José Basin (800

- 1200 m), the mid

- elevation Providence Creek watersheds (1485

- 2005 m), and the upper el evation Bull Creek watersheds (2050

- 2420 m) in the Sierra National Forest, California in WY2008 and WY2009. The mean hillslope sediment production rate in José Basin in WY2008 was 7.4 x 10 - 3 kg m - 2 . While sediment production rates for hillslopes in the P rovidence Creek and Bull Creek54

watersheds were at least an order of magnitude less than values from José Basin in WY2008, there was no significant difference in values between the three areas. In WY2009 none of the hillslopes in José Basin produced any se diment, and rates in the Bull Creek watersheds were higher than values in the Providence Creek watersheds

. According to these data, sediment production from hillslopes wa s not significantly higher in rain dominated areas than snow dominated areas, and thi s can be attributed to the

dense cover of vegetation and litter protecting the hillslope from rainsplash and erosive

overland flow. The mean road sediment production rate in José Basin was 1.8 kg m - 2 yr - 1 , with values from individual segments ranging fr om zero to 12.9 kg m - 2 yr - 1 . There was no significant difference in road sediment production between hillslopes and road segments in Holland soils and in other soil types. Thirty percent of the native surface road length in José Basin was directly connec ted to the stream network. While WEPP:Road performed poorly in predicting sediment production from native surface roads in José Basin, an empirical multivariate model predicted road sediment production to increase with increas ing in annual precipitation and total rill length on the road surface, and decrease with an increase in road segment area. Using this model, native surface roads in José Basin are estimated to produce 680 tons yr - 1 of

sediment , and up to 210 tons yr - 1 are deliver ed to the stream ne twork. In contrast, hillslopes, which occupy orders of magnitude more area than roads, are estimated to contribute 290 tons yr - 1 . This indicates that native surface roads are a major contributor

of sediment in José Basin.55 Mean road sediment production in the Providence Creek watersheds was 0.13 kg

m - 2 yr - 1 , which was more than an order of magnitude lower than in José Basin. Only 3% of the road length was connected to a stream, so road sediment delivery to streams is very low. Mean road sediment produc tion in the Bull Creek watersheds was similar to the

values from the Providence Creek watersheds. The results show that road sediment production is much higher in rain dominated areas than in snow dominated areas, as the

bare surface subjected to rainspla sh and higher rates of overland flow. Road sediment production rates in the Providence Creek watersheds would likely experience a ten

- fold increase if the dominant precipitation were to switch from snow to rain. Road sediment production was proportional to the total length of rills on a

segment , indicating the importance of rilling for road sediment production

. An important management implication is to restrict driving during wet conditions to reduce tire depressions, which in turn can reduce rilling and sediment production. Rilling was more extensive on longer, steeper segments, and erosion control efforts and best management practices should target these segments. Practices that aim to reduce sediment production and delivery such as graveling, paving, grading, and installing waterbars are examined in the following chapter.56

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2.9. Tables Table 2.1. Elevations and annual precipitation for WY2 008 and WY2009 for the four climate stations in the KREW watersheds. There are no data for the lower Bull Creek rain gage in WY2009. Annual precipitation (mm) Climate station Elevation (m) WY2008 WY2009 Lower Providence 1749 913 966 Upper Provide nce 1984 1148 958 Lower Bull 2194 1116

-- -- Upper Bull 2463 1133 1081 Mean (s.d.) 2098 (304) 1078 (110) 1002 (69)62

Table 2.2. Hillslope characteristics and surface cover categories measured for each hillslope with a sediment fence in José Basin. Th e O horizon depth was measured at nine systematically

- spaced points on each hillslope.

Hillslope characteristics Hillslope surface cover categories Dominant soil type (Holland, other) Bare soil

Area (m 2 ) Litter Axis length (m) Woody debris (>1 cm diame ter) Axis gradient (%) Live vegetation Mean right and left sideslope gradients (%) Rock (>1 cm diameter)

Presence of rills (Y/N) Bedrock Total rill length (m) Mean rill width (m) Mean rill depth (m) Shortest distance from rill to fence (m) O ho rizon depth (m)63

Table 2.3. Number of hillslopes and native surface road segments with valid sediment production data in Holland soil and other soil types in José Basin for WY2008 and WY2009.

Hillslopes Native surface road segments Water year Other soil types Holland soil Other soil types Holland soil 2008 7 3 5 8 2009 7 3 12 18 Totals 14 6 17 2664

Table 2.4. Number of hillslopes and native surface road segments with valid sediment production data in the Providence Creek and Bull Creek watersheds from WY2004 through WY2009.

Providence Creek watersheds Bull Creek watersheds Water year Hillslopes Native surface segments Hillslopes Native surface segments 2008 10 6 6 9 2009 10 6 6 9 Totals 59 55 34 4565

Table 2.5. Road segment characterist ics measured, estimated, or observed for each segment with a sediment fence and the surveyed road segments. ―/E‖ indicates that the characteristic was estimated rather than measured for the segments that were not monitored for sediment production.

Charac teristic Measured (M), estimated (E), or observed (O) Continuous variable

(C) or categorical group (G) Method of

measurement Segment length (m) M C Meter wheel Surface type (Native, gravel) O G Active width (m) M C Cloth tape Total width (m) M C Cloth tape Segment slope (%) M C Clinometer Bare soil (%) M / E C Cover count Gravel cover (%) M / E C Cover count Traffic level (Very low, low, medium) E G Evidence of past surface rocking (Y/N) O G Cutslope height (m) E C Cutslope gradient (%) M C C linometer Cutslope percent bare soil (%) E C Slope of upper hillslope (%) M C Clinometer Slope of lower hillslope (%) M C Clinometer Ditch width (m) M C Cloth tape Ditch slope (%) M C Clinometer Maximum rill length (m) M C Cloth tape Mean rill widt h (m) M C Ruler Mean rill depth (m) M C Ruler Drain type (see Table 2.6) O G Drain feature (see Table 2.6) O G Drain armoring (Y/N) O G Water cross armoring (Y/N) O G Armoring buried (Y/N) O G Armoring intact (Y/N) O G Pushout present (Y/N) O G Pushout effective (Y/N) O G Fillslope erosion (Y/N) O G Maximum fillslope rill depth (m) M C Ruler Multiple fillslope rills (Y/N) O G Drainage feature length (m) M C Cloth tape Drainage feature slope (%) M C Clinometer Drainage feature roughn ess (1,2,3,4) O C Connectivity class (1,2,3,4) O G Culvert present (Y/N) O G Culvert plugged (%) E C Scour at culvert outlet (Y/N) O G Volume of scour at culvert outlet (m 3 ) M C Cloth tape66

Table 2.6. Drain type and drain feature categories used to describe each road segment. Slashes indicate a mixture of types or features within a road segment. *Sediment production was not measured on segments that were either completely or partially outsloped or had any diffuse drainage.

Drain types Drain fe atures Insloped Diffuse* Outsloped (diffuse)* Dip Outsloped (with a berm) Pushout Planar Waterbar Through cut Stream crossing Insloped/Planar Cattle guard Insloped/Outsloped with a berm On segment deposition Outsloped with a berm/Planar Intersectio n Planar/Outsloped* Diffuse/Dip* Insloped/Outsloped/Planar* Diffuse/Waterbar* Diffuse/Pushout* Diffuse/Intersection* Diffuse/On segment deposition* Dip/Pushout Dip/On segment deposition Intersection/On segment deposition67

Table 2.7. Defini tions of connectivity classes and the associated potential for sediment to be delivered to the stream network. Connectivity Drainage Potential for class characteristics sediment delivery 1 Drainage feature <10 m long. Very low

2 Drainage feature <2 0 m long. Low/moderate

3 Drainage feature >20 m long but more than

10 m from a stream channel. Moderate/high

4 Drainage feature to within 10 m of a stream

channel, regardless of length. High68

Table 2.8. Mean elevation, area, and sediment production ra tes for hillslopes in José Basin and the Providence Creek and Bull Creek watersheds for WY2008 and WY2009. None of the monitored hillslopes in José Basin produced sediment in WY2009. Mean sediment production rate (kg m - 2 yr - 1 ) Study site Elevation ( m) Area (ha) WY2008 WY2009

Mean s.d. Mean s.d. n Mean s.d. n Mean s.d.

José Basin 1100 8104 0.42 0.32 10 7.4 x 10 - 3 2.1 x 10 - 2 10 0 0 Providence Creek watersheds 1915 54 0.55 0.37 10 7.9 x 10 - 4 1.0 x 10 - 3 11 7.0 x 10 - 6 2.2 x 10 - 5 Bull Creek waters heds 2320 131 2.08 0.84 4 4.6 x 10 - 4 9.1 x 10 - 4 7 3.8 x 10 - 4 9.5 x 10 - 469

Table 2.9. Mean elevation, area, slope, and sediment production rates for native surface road segments in José Basin and the Providence Creek and Bull Creek watersheds for WY2008 a nd WY2009.

Mean sediment production rate (kg m - 2 yr - 1 )

Basin or watersheds Elevation (m) Area

(m 2 ) Slope

(m m - 1 ) WY2008 WY2009 Mean s.d. Mean s.d. Mean s.d. n Mean s.d. n Mean s.d. José Basin 1056 82 115 44 9 3 12 1.4 2.3 29 2.1 3.1 Providence Creek watersheds 1859 85 102 36 10 3 6 0.12 0.14 6 0.14 0.12 Bull Creek watersheds 2292 62 117 48 9 3 9 0.042 0.067 9 0.23 0.2770

Table 2.10. Correlation coefficients, coefficients of determination, and p

- values for the site variables included in the univ ariate analysis of annual sediment production from native surface road segments in José Basin (n = 43). Values in bold are significant at p ≤ 0.10.

Variable r R 2 p

- value Length (m)

- 0.13 0.02 0.53 Area (m 2 )

- 0.14 0.02 0.65 Slope (m m - 1 ) 0.30 0.09 0.03 Area*Slope (m 2 m m - 1 ) 0.08 0.01 0.33 Annual precipitation (mm) 0.04 0.00 0.22 Annual erosivity (MJ ha - 1 mm hr - 1 )

- 0.01 0.00 0.35 Percent bare soil 0.27 0.07 0.15 Percent gravel cover

- 0.09 0.01 0.26 Percent Holland soil B horizon

- 0.10 0.01 0.72 Ele vation (m)

- 0.18 0.03 0.92 Rill length (m) 0.62 0.39 0.0004 Rill volume (m 3 ) 0.49 0.24 0.001671

Table 2.11. Coefficients and p

- values for significant variables in the multivariate model for predicting annual sediment production from native surface roa d segments in José Basin.

Variable Coefficient p

- value Rill length (m) 0.11 <0.0001 Segment area (m 2 )

- 0.016 0.02 Percent Holland soil B horizon on segment surface

- 0.029 0.03 Annual precipitation (mm) 0.0056 0.06 Intercept 0.01072

Table 2.12. Se diment production rates from five other studies in snow, mixed rain and snow, and rain climates. Data from the current study are in italics.

Dominant precipitation Study Annual precipitation Annual sediment production

from native surface roads

mm kg m - 2 Mg km - 1

Snow Bull Creek watersheds 1000 0.13

Mixed rain and snow Providence Creek watersheds 1100 0.14

Coe, 2006 1300 0.32 1.6 Megahan, 1974 700 0.48

Rain José Basin 530 1.8 10

Barrett and Tomberlin, 2006 1400 0.5 to 4

Ramos

- Scharrón and MacDonald, 2005 900

- 1400 5 to 15 Reid and Dunne, 1984 3900 4173

2.10. Figures

Figure 2.1. Location of the national forests in California, including the Eldorado and the Sierra National Forest (SNF). Inset of the SNF shows Jos é Basin and the Kings River Experimental Watershed (KREW). X indicates the location of the Auberry precipitation gage (CA map from http://www.fs.fed.us/r5/forests.shtml ).74

Figure 2.2. Elevation con tours and the location of the five rain gages (JRG1

- JRG5) in José Basin (derived from digital elevation maps in the SNF data base, accessed via A. Gallegos, 2007).75

Figure 2.3. Roads (in black) and streams (in blue) in José Basin (data from the SNF da ta base, accessed via A. Gallegos, 2007). Colored areas in the background represent convergent areas that are likely wet or contain flow during the wet season from approximately October through May.76

Figure 2.4. The King’s River Experimental Waters hed (KREW) contains two sets of four watersheds. The lower elevation Providence Creek watersheds (a) have elevations ranging from 1485 to 2005 m, while the higher elevation Bull Creek watersheds (b) range from 2050 to 2420 m (Korte, 2005). Sediment fence s on roads are indicated by yellow circles, and sediment fences on hillslopes are indicated by yellow circles with attached contributing areas in blue (figures from Korte, in preparation).77

Figure 2.5. Sediment fences were installed on undisturbed, co nvergent swales in José Basin and the Providence Creek and Bull Creek watersheds. The fabric floor facilitates sediment removal and the accuracy of the measurement (photo by A. Korte).78

Figure 2.6. Sediment fences were installed at the drainage point of native surface road segments in José Basin as well as the Providence Creek and Bull Creek watersheds. This fence was installed just below a waterbar draining a native surface road segment in José Basin in summer 2007.79

Figure 2.7. Location of the road sections (in black) in José Basin that were randomly selected to be surveyed. The remainder of the road network is shown in grey.80

Figure 2.8. Annual precipitation for the rain gages in José Basin. Four rain gages functioned during WY2008 an d three gages in WY2009.81

Figure 2.9. Precipitation versus elevation for the Providence Creek and Bull Creek watersheds for (a) WY2008 and (b) WY2009.82

Figure 2.10. Mean sediment production rates for native surface road segments in José Basin, the Providence Creek watersheds, and the Bull Creek watersheds for WY2008 and WY2009. Error bars display one standard deviation.83

Figure 2.11. A relatively small proportion of the road length monitored produced 75% of the sediment in b oth WY2008 and WY2009.84

Figure 2.12. Mean sediment production rates for native surface road segments in José Basin in other soil types and in Holland soil for WY2008 and WY2009. Error bars indicate one standard deviation.85

Figure 2.13. Annual sedi ment production and segment slope were significantly correlated for native surface road segments in José Basin (p = 0.03).86

Figure 2.14. Cumulative proportion of road length by drainage feature length for native surface road segments in José Basin and the Providence Creek watersheds.87

Figure 2.15. Cumulative percent of road length by hydrologic connectivity class for native surface segments in José Basin and the Providence Creek watersheds.8 8

Figure 2.16. Cumulative percent of native surf ace road length in José Basin by hydrologic connectivity class for other soil types and Holland soil.89

Figure 2.17. Predicted versus measured sediment production rates using the empirical multivariate model developed for native surface road segments i n José Basin.90

Figure 2.18. Comparison of the predicted road sediment production using WEPP:Road to the values measured in José Basin (n = 43).91

Figure 2.19. Mean sediment production rates normalized by slope for native surface segments with and without rills in José Basin for WY2008 and WY2009 (p < 0.0001 and p = 0.007 , respectively). Error bars represent one standard deviation.92

Figure 2.20. Mean sediment production rates in José Basin for native surface segments with slopes less than and g reater than 7% for WY208 and WY2009 (p = 0.18 and 0.06, respectively).93

3. EFFECTS OF GRAVELING AND GRADING ON SEDIMENT PRODUCTION AND DELIVERY

ABSTRACT: Rocking, grading, and installing waterbars are common road maintenance techniques for unpaved roads, a nd these are intended to improve drivability and reduce both sediment production and sediment delivery to streams. A study in the Sierra National Forest, California was conducted to compare sediment production and delivery from: 1) native and gravel surfa ce road segments in the lower elevation José Basin (800

- 1200 m) and the higher elevation Providence Creek watersheds (1485

- 1205 m); and 2) ungraded and graded native surface road segments in José Basin. Sediment fences were

used to measure annual sediment production rates. Road segment characteristics such as segment length and slope were measured, and road sediment delivery was estimated by assessing each drainage feature. For water year (WY) 2004 through WY2006, the mean sediment production rate for g ravel surface segments was 0.23 kg m 2 yr - 1 in the Providence Creek watersheds, or

14

- 29% of the value for native surface segments, and this difference was significant. There was no significant difference in WY2007 due to very low precipitation and road

er osion rates, or in WY2008 and WY2009 due to very high sediment production rates from one gravel segment. In José Basin, gravel surface roads produced significantly more sediment than native surface segments in WY2008, and there was no significant

differen ce in WY2009. Gravel surface segments in José Basin have only 29% gravel cover on average, which is inadequate to significantly reduce rainsplash and sheetwash

erosion.94 Pre

- and post

- treatment surveys of approximately eight kilometers of roads in

José Ba sin indicated that grading and waterbar installation decreased the mean segment length from 65 to 41 m, but 22% of the waterbars that were installed or reconstructed failed within the first year after grading, resulting in a 15% increase in segment length. Rills developed on 31% of the segments within the first year after grading. Different comparisons in different years indicated that graded road segments produced 2.6 to 7.6 times more sediment than ungraded segments. Though grading reduced the length o f road directly connected to the stream network by half, the net result was a 20

- 320% increase in the estimated sediment delivery to streams. The results indicate that the frequency of grading should be reduced as much as possible to prevent an increase i n sediment delivery. Waterbars need to be compacted and high with adequate cross

- slope to direct water off the surface. Restricting traffic

under wet conditions can reduce the occurrence of waterbar failure and the need for grading.95

3.1. Introduction Increased sediment loading to streams, rivers, and lakes is a major concern, as this can adversely affect water quality, stream habitat, and aquatic ecosystems (Bilby et al., 1989; Ziegler and Giambelluca, 1997; Kolka and Smidt, 2004). The EPA lists sedi ment as the most common impairment to water quality in streams and lakes in the United States (EPA, 2010). Fine sediment also can decrease pool depth and abundance, and increase the turbidity of the stream (Beechie et al., 2005), both of which can alter t he quality and quantity of habitat for salmonids and limit reproduction (Harr and Nichols, 1993; Weaver and Hagans, 1999; Beechie et al., 2005). Increased sediment loading also can affect aquatic organisms by altering stream temperatures and nutrient load s (Kolka and Smidt, 2004). The U.S.D.A. Forest Service lists sediment as one of the primary impairments to water quality in North American forests, along with pathogenic organisms, organic material, nutrients, dissolved solids, and toxics (Brown and Binkl ey, 1994). Sediment loading in streams occurs when surfaces that are hydrologically connected to the stream erode. Hillslope sediment production rates in undisturbed forested watersheds are typically very low (MacDonald et al., 2004), as forests have a dense surface cover of vegetation and litter and a high porosity and infiltration rate. These characteristics largely prevent soil detachment and overland flow (Dunne and Leopold, 1978). Surface disturbances such as fire, concentrated grazing, or road

co nstruction can expose the mineral soil and reduce the infiltration rate (MacDonald et al., 2001; Ramos

- Scharrón and MacDonald, 2005). This can result in a higher likelihood96

for the occurrence of erosive overland flow, which can detach the exposed mineral soil particles and transport them to the stream network. Unpaved roads typically have a high percentage of exposed mineral soil that is susceptible to detachment and transport. In forested watersheds, unpaved roads are often a major source of sediment to streams (Reid and Dunne, 1984; Swift, 1988; Bilby et al., 1989; Luce and Black, 1999; Ketcheson et al. 1999; Coe, 2006). Roads can deliver a large amount of sediment to streams relative to their surface area even during low to moderate rainfall events (Z iegler and Giambelluca, 1997; Chappell et al., 1999; Ziegler et al., 2004; Cafferata et al., 2007). Road sediment production can vary greatly both inter

annually and among road segments, which are defined as sections of the road that have clearly defined contributing areas and discrete drainage points or are outsloped (Coe, 2006; Korte, in preparation). Rocking, grading, and installing waterbars are common treatments to reduce road sediment production, reduce road sediment delivery, and maintain road driva bility. Rocking reduces sediment production by covering the bare mineral soil, thereby reducing rainsplash detachment, and also reduces the velocity of overland flow, which further reduces detachment and sediment transport (Megahan et al., 1991; Poesen et al., 1994; Appelboom et al., 2002; Sheridan and Noske, 2007; Rivera et al., 2009). Grading, while maintaining drivability, typically increases the supply of finer soil particles that can be readily detached by rainsplash and sheetwash and thereby often i ncreases sediment production (Megahan and Kidd, 1972; Megahan, 1974; Reid and Dunne, 1984; Megahan et al., 1986; Luce and Black, 1999; Ziegler et al., 2000; Ziegler et al., 2001; Appelboom et al., 2002; Ramos

- Scharrón and MacDonald, 2005; Coe, 2006). If f low becomes97

concentrated, severe rilling may occur, which can increase sediment production and reduce road drivability. Installing waterbars reduces the contributing area of a road segment, which should decrease the amount of concentrated runoff and sedim ent production (Chapter 2). By altering segment length and drainage from a road, waterbar

construction and maintenance can reduce road

- stream connectivity and sediment delivery

to the stream network. These issues are of particular concern on National Fore st lands in the Sierra Nevada, and the present study follows from two earlier projects. The first study in the Eldorado National Forest in the northern Sierra Nevada (Figure 3.1) measured sediment production rates from 15 native surface road segments that were not recently graded, 2

- 40 recently graded road segments, and 9

- 10 ungraded gravel surface road segments from water year (WY) 2000 to 2002 (Coe, 2006). The second study was centered on the Kings River Experimental Watershed (KREW) in the Sierra Nation al Forest (SNF) in the southern Sierra Nevada (Figure 3.1). In this area precipitation falls mainly as snow, although occasional rain or rain

- on

- snow events may occur. From WY2004 to WY2006, sediment production was measured from

11

- 13 native surface, sev en gravel surface, and four mixed surface road segments as well as from seven ditches adjacent to paved roads (Korte, in preparation). Both of these studies also conducted extensive road surveys to characterize the road network and

evaluate road

- stream co nnectivity. This study continued the measurements of road sediment production from different road surface types in the KREW watersheds, but the primary focus was shifted to the lower elevation José Basin, which is also located in the SNF. José Basin is a 7898

km 2 watershed approximately 20 km west of KREW (Figure 3.1), and here the precipitation falls primarily as rain. The specific objectives of this portion of the study were to: 1) quantify the effect of road surface type on sediment production and delive ry in KREW under a range of climatic conditions; 2) quantify the effect of graveling on road sediment production and delivery in José Basin; 3) predict the total sediment delivered from gravel surface roads to the stream network in José Basin; 4) quantify the effect of grading and waterbar installation on road segment characteristics, road sediment production, and road sediment delivery in José Basin; and 5) quantify the effect of rill erosion on sediment production following grading in José Basin.

3.2. Ba ckground 3.2.1. Road sediment production and delivery Road surface sediment production is the result of several erosional and transport processes. These include: 1) rainsplash detachment, 2) sheetwash, and 3) rill erosion (Zeigler et al., 2000). Rainspla sh detachment occurs when the impact of a raindrop detaches fine sediment from the road surface (Zeigler et al., 2000). The rate of rainsplash detachment is highly dependent on the rainfall erosivity, which in turn is a function of the precipitation inten sity and the drop size distribution (Lal, 1988; Renard et al., 1997). When rainfall intensity exceeds the infiltration capacity of a surface, water flows downslope as infiltration

- excess or Horton overland flow (HOF) (Dunne and Leopold, 1978). Sheetwash and rill erosion occur when the shear stress applied by this overland flow exceeds the resistance of the surface (Dunne and Leopold, 1978).99 The amount of sheetwash and rill erosion is directly related to the force of the flow and the surface erodibility (Luce and Black, 1999; Croke and Hairsine, 2006). The force of a given flow is related to the depth and velocity of flow (Dunne and Leopold, 1978). The depth and velocity of flow are functions of the duration and intensity of a given precipitation event relative to the infiltration rate (Dunne and Leopold, 1978). Infiltration rates on unpaved roads tend to be very low due to compaction. Values in Idaho, Colorado, and Montana ranged from 5 x 10 - 5 to 8.8 mm h - 1 with a geometric

mean of 0.11 mm h - 1 (Luce an d Cundy, 1994). Given a spatially uniform precipitation rate and no contribution from the adjacent hillslope, the discharge from a road segment is a direct function of the area of that segment (Leopold et al., 1964). Given a discharge, the slope and roug hness of a road segment determines the flow velocity and hence the erosive energy of the discharge (Dunne and Leopold, 1978). Therefore the detachment, shear stress, and sediment transport capacity of overland flow are direct functions of the precipitatio n characteristics (Dunne and Leopold, 1978), the contributing area and slope of a road segment, and the road surface characteristics (Anderson and MacDonald, 1998; MacDonald et al., 2004; Coe, 2006). As the runoff becomes channelized into rills, the detach ment and transport capacity increases because the flow is deeper and faster (Merz and Bryan, 1993; Brunton and Bryan, 2000). It follows that the amount of rilling varies with precipitation characteristics and soil properties (Brunton and Bryan, 2000). Ro ad sediment production was found to be strongly related to rill density in Colorado (R 2 = 0.57, p < 0.0001) (Welsh, 2008), and on exposed hillslopes rill erosion can be the primary sediment source rather than sheetwash (Pietraszek, 2006). Excessive rillin g on unpaved roads reduces100

drivability and grading may be needed to restore a smooth, drivable surface. Excessive rill erosion following grading may result in the need for repetitive grading, and previous studies have not quantified the contribution of ri ll erosion to sediment production after grading. The effects of unpaved roads on runoff and erosion may not be a concern unless a road is hydrologically connected to a stream, lake, or other area of concern (Wemple et al., 1996; La Marche and Lettenmaier , 2001; Bowling and Lettenmaier, 2001). In some areas most of the connected segments are due to road

- stream crossings (Wemple et al., 1996; Croke and Mockler, 2001; Coe, 2006), but road

- stream crossings are not common

in either KREW or José Basin. In the se areas road

- stream connectivity is primarily due to HOF from the road surface forming a small channel or sediment plume that extends to the stream network (Montgomery, 1994; Wemple et al., 1996; Croke and Mockler, 2001; La Marche and Lettenmaier, 2001; B owling and Lettenmaier, 2001). The overall increase or decrease in sediment contributed to the stream after any type of road maintenance is therefore the combination of the impact on sediment production and the impact on sediment delivery.

3.2.2. Effects of graveling on road sediment production and delivery The same factors that affect sediment production on native surface roads also affect sediment production on gravel surface roads, as they are subject to the same set of runoff and erosional processes ( Sheridan and Noske, 2007). However, the relative magnitude of these processes will differ from native surface roads, so sediment production rates from gravel surface roads are typically lower than comparable native101

surface road segments. Much of this dif ference is due to the large reduction in both rainsplash and sheetwash erosion (Poesen et al., 1994; Megahan et al., 1991; Rivera et al., 2009). The reduction in rainsplash erosion is because the surface gravel shields the finer, more easily detached sed iment particles from raindrop impact. Graveling greatly reduces sheetwash erosion by reducing the velocity of flow over a road surface and shielding the finer particles from the shear stress of the overland flow. Graveling also can reduce the

amount of r unoff by providing a more porous surface (Appelboom et al., 2002) and possibly allowing more infiltration into the underlying native material by reducing compaction. The reduction in velocity also allows more time for water to infiltrate,

which will reduc e surface runoff. In Australia mean runoff ratios for gravel surface roads were only 0.55 as compared to 0.66 for native surface segments (Sheridan and Noske, 2007). In North Carolina, the runoff volume for older and newly graveled road segments respecti vely averaged 45% and 39% less than native surface road segments (Appelboom et al., 2002). This reduction in runoff will result in shorter drainage features, potentially reducing road

- stream connectivity.

3.2.3. Effects of grading and waterbar installati on on sediment production and delivery The effects of grading and waterbar installation are often believed to be beneficial in terms of reducing sediment delivery to streams, but this is a complex issue. Grading

disturbs the road surface and increases th e supply of material for transport, which can lead to an initial increase in sediment production (Megahan and Kidd, 1972; Megahan, 1974; Reid and Dunne, 1984; Megahan et al., 1986; Luce and Black, 1999; Ziegler et al.,102

2000; Ziegler et al., 2001; Appelboom et al., 2002; Ramos

- Scharrón and MacDonald, 2005; Coe, 2006). As the time since grading increases, the fine material on the road surface is eroded away and a coarser armor layer forms, which is more resistant to both rainsplash and sheetwash erosion (Zie gler et al., 2000; Ramos

- Scharrón and MacDonald, 2005). The resulting reduction in sediment production rates following grading has been modeled by the equation:

E t = E n + kSe - kt (equation 3.1)

where E t is the sediment pro duction rate (Mg km - 2 day - 1 ), E n is the sediment production rate that would be approached if no disturbance occurred (Mg km - 2 day - 1 ), k is an index of the decline in erosion following grading (days - 1 ), S is the total rate of material

available for erosion immediately after grading (Mg km - 2 day - 1 ), and t is the time since disturbance in days (Megahan, 1974). In the northern Sierra Nevada, road segments that were graded within the past two

years produced approximately twice as much sediment as segments that h ad not been recently graded (Coe, 2006). This increase was more prevalent at elevations below 1400 m, where a greater proportion of the precipitation fell as rain rather than snow (Coe, 2006). There was no apparent decline in sediment production between the first and the second year after grading (Coe, 2006). On St. John in the U.S. Virgin Islands, recently graded road segments produced 2.5 times more sediment per unit precipitation than comparable non

- graded roads (Ramos

- Scharrón and MacDonald, 2005). In the Oregon Coast Range, grading of ditches and cutslopes resulted in a seven

- fold increase in sediment production (Luce and Black, 1999).103 Waterbars are often constructed or rebuilt when grading occurs. Waterbars direct flow off the road surface, whic h should reduce sediment production by reducing the length and hence the contributing area of a segment. However, waterbars can fail due to flow depths that exceed the waterbar height, sediment deposition upslope of the waterbar, or rill erosion through t he waterbar. The strategic placement of waterbars can reduce

road

- stream connectivity by reducing the amount of runoff and sediment production from a single drainage point, directing flow off of the road where it can infiltrate, and disconnecting segments that would otherwise flow directly into a stream. There are very few data on the effects of waterbar failure on segment contributing length and sediment delivery, and this study will examine these effects in José Basin.

3.3. Methods 3.3.1. Site descrip tion Providence Creek watersheds, KREW The Kings River Experimental Watershed (KREW) contains four mid

- elevation (1485 to 2005 m) watersheds ranging from 0.49 km 2 to 1.32 km 2 within the Providence Creek watershed (Figure 3.2). The area has a Mediterranean

- type climate with dry summers and wet winters. Average annual precipitation is 1240 mm, with approximately 90% of the precipitation falling as snow (Korte and MacDonald, 2007). Vegetation is primarily Sierra mixed

- conifer forest (Eagan et al., 2007). T he area has a granitic lithology with coarse sandy loam and loamy sand soils of the Gerle, Cagwin, and Shaver

series (USDA, 1983; Korte and MacDonald, 2007).104 There are 12.6 kilometers of road in the Providence Creek watersheds, with half these being native surface. Th ere are 1.5 km of gravel surface roads and 1.9 km of paved roads, and the latter are generally insloped with ditches. The remaining roads are classified as mixed surface roads, as they are a complex intermixing of native surface, gravel, and old pavement. In recent years very little road maintenance work has been done in the Providence Creek watersheds. The majority of the graveling was done at least ten years ago, with only small patches of gravel or other maintenance practices being put into place on an as needed basis. No grading has been done in the Providence Creek watersheds in the past

ten years.

José Basin The primary study area was José Basin, and this is approximately 20 km west of KREW (Figure 3.1). Elevations range from 450 m to 1950 m, though most of the study sites were between 800 m and 1200 m elevation. Most precipitation at the lower elevations falls as rain, and in the upper portions of the basin there is usually a seasonal snowpack (A. Gallegos, USDA Forest Service, pers. comm., 2 008). Rain

- on

- snow events can occur at any elevation depending on the sequence of warm and cold storms and the diurnal fluctuations in temperature. There are 447 km of stream channels in José Basin and the drainage density is 5.7

km km - 2 (Figure 3.3). The basin has 159 km of mapped roads for a relatively high road density of 2.0 km km - 2 (Figure 3.3). Road drivability is crucial in José Basin, as there are scattered houses in some areas, and the basin is heavily used for grazing, logging, and105

recreation al uses such as hunting and off highway vehicles. Approximately one third of the unpaved roads in José Basin have at least 20% gravel cover. Road maintenance is relatively common in José Basin to maintain drivability.

Box

- drag grading is performed at l east annually or more by residents on at least one road section, and more intensive grading is done by Southern California Edison to maintain road access to its properties and power lines. Less frequent grading projects with

waterbar installation and reco nstruction are done on an as

- needed basis by the SNF to maintain drivability and decrease sediment delivery.

3.3.2. Precipitation

Providence Creek watersheds KREW staff operates two climate stations in the Providence Creek watersheds

— one at 1750 m and another at 1984 m. Fifteen

- minute precipitation data have been collected from water year 2004 (WY2004) through WY2009. Annual precipitation was calculated for both climate stations. Regression equations relating elevation to annual precipitation were de veloped for each water year and used to estimate the annual precipitation for each site where road sediment production was being measured.

José Basin Five tipping bucket rain gages were installed in José Basin, but equipment problems and vandalism mean t that valid data were obtained from four rain gages in WY2008 and three gages in WY2009. Annual precipitation and erosivity were calculated using the RF program for each gage for each year (Petkovsek, 2001). No106

correlation was found between elevation an d annual precipitation or erosivity for either water year, so data from the nearest functioning rain gage was assigned to each segment where sediment production was measured. The precipitation data from José Basin was put in historical context by using dat a from the Auberry climate station, which is the closest long

- term station. The Auberry station is at 640 m and about one kilometer west of José Basin (Figure 3.1). The mean annual precipitation at Auberry was calculated using the 95 year record. Annual precipitation in José Basin was compared to annual precipitation at Auberry for WY2008

and WY2009.

3.3.3. Sediment production Sediment production from discrete road segments was measured using sediment fences (Robichaud and Brown, 2002) (Figure 3.4). F ences were constructed of a geotextile fabric attached to 1

- 2 m long pieces of 1.3 cm diameter rebar pounded 0.3

- 0.5 m into the ground. The leading edge of the fabric was attached to the ground with landscape staples to prevent underflow. The captured se diment was removed during the dry season and weighed in the field to the nearest 0.5 kg. Two representative samples of about 500 g were collected to determine percent moisture (Gardner, 1986) and percent organic matter (Ben

- dor and Banin, 1989). The mean percent moisture and organic matter values were used to convert the field weights to a dry mass of mineral sediment. The annual sediment production rate (kg m - 2 yr - 1 ) was determined by dividing the calculated dry mass of mineral sediment by the contribut ing area of the road surface.107 In the Providence Creek watersheds, annual sediment production rates for native, gravel, and mixed surface road segments as well as ditches adjacent to paved roads were measured and calculated by A. Korte for WY2004 through WY2006 (in preparation). Sediment production continued to be monitored in the Providence Creek watersheds through WY2009, though the sample size for native surface segments decreased in

WY2007 due to the removal of seven sediment fences that were located on Southern California Edison land (Table 3.1). In José Basin, sediment production was measured in WY2008 and WY2009 from

13

- 30 native surface road segments that were not recently graded (―ungraded‖ segments),

5

- 11 gravel surface segments, and 3

- 24 nativ e surface segments for one and two water years after grading (Table 3.2). More than half of the sediment fences in José Basin overtopped in WY2008, and sediment production values from the overtopped fences

were excluded from all calculations. In WY2009 s ediment production was measured from six matched pairs of road segments, where one segment was graded in summer 2008 while the other segment was left ungraded. These pairs also were included in the larger pool of ungraded and graded segments (Table 3.2).

3.3.4. Road segment characteristics The key characteristics for each road segment with a sediment fence were measured or classified (Table 3.3) to help compare and explain sediment production and potential sediment delivery. The length of each segment was measured with a meter wheel. A cloth tape was used to measure the active width, which is the width of the road that is regularly driven on, and the total width, which was defined as the width from the108

bottom of the cutslope to the top of the fillslo pe. The area of the road segment was the segment length times the active width. A clinometer was used to measure the segment slope or each change of slope if the segment was not uniform, and the segment slope was then calculated as the length

- weighted sl ope. Percent surface cover was determined by classifying the surface at a minimum of 100 systematically spaced points sampled along a zigzag transect on the active road surface. Each point was classified as bare soil, gravel (rock with a secondary axis greater than one centimeter), litter, or live vegetation. Segments with less than 20% gravel cover were classified as native surface segments while segments with greater than 20% gravel cover were classified as gravel segments. Traffic was classified by determining the branch order of the road relative to a main road and visual inspection. Classes ranged from very low, indicating that vehicles very rarely travelled on the road, to low, medium, and high. Drain types and drain

features were classified fo llowing the categories in Table 3.4. The elevation and location of the drainage point of each segment was determined using a GPS unit. All road surveys in the Providence Creek watersheds were completed by A. Korte (in preparation) prior to this study.

Th e bulk density of 13 segments prior to grading was measured by the excavation method (Grossman and Reinsch, 2002). Three pits approximately 7 cm by 7 cm were dug on the road segment to the depth of the deepest rill. The excavated sediment was collected, dried for 24 hours at 105°C , and weighed. The volume of the pit was determined from the volume of 30 grade silicon sand used to fill each pit. The bulk density was calculated by dividing the mass of the excavated sediment by the pit volume,109

and then ave raging the three measurements. Bulk density was re

- measured immediately after grading using the same procedure and again one year after grading.

3.3.5. Rill volume and contribution to sediment erosion after grading Field observations confirmed that gra ding results in a planar road surface. The length and volume of rills that developed in the first year after grading was measured by placing a straight edge across the road surface and measuring the rill depth at 3

- 4 evenly spaced locations across the ril l. The cross

- sectional area at that location was the average depth times the rill width. The cross

- sectional area was measured for every major change in rill depth and/or width along the length of the rill, and the rill volume was calculated by:

(equation 3.2)

where a is equal to the cross

- sectional area (m 2 ) and l is equal to the rill length (m) represented by that cross

- section. Th e mass of sediment from rill erosion for each graded segment was calculated by multiplying the mean bulk density after grading by the total rill volume, and this value was compared to the mass of sediment captured by the corresponding sediment fence to det ermine the proportion derived from rill erosion (Pietraszek, 2006).

3.3.6. Sediment delivery The potential for runoff and sediment to be delivered to the stream network was evaluated for each monitored road segment by identifying and following any draina ge feature, such as a sediment plume or a rill originating from the drainage point of a road110

segment (Coe, 2006). The maximum length and mean slope of each drainage feature was measured in the same manner as for the road segments (Table 3.3). The roughne ss of the drainage pathway was classified on a scale of one to four, with class one being very smooth and class four having a large amount of live vegetation, logs, woody debris, or rocks trapping or dispersing the surface runoff and sediment. The presen ce or absence of pushouts at the drainage point of the road segment was observed (Table 3.3). Pushouts were classified as no longer intact if they were too filled with sediment for the water to drain, or if the surface drainage no longer directed

flow to the pushout. The presence or absence of large rocks to armor either the drainage point or the road surface at a stream crossing also was observed. This drain armoring was classified as intact if it was still in place, but it was also noted whether the ar moring was exposed or buried under deposited sediment. The locations of culverts were noted, and the percent of the cross

- sectional area that was plugged with sediment or large woody debris was estimated. The presence of scour at the downstream end of ea ch culvert was noted and measured if present. The connectivity class of each road segment was determined according to the length of the drainage feature and whether this extended to within 10 m of a defined channel (Table 3.5). Segments with a connectiv ity class of one have very little potential to deliver runoff and sediment to a stream channel, while segments with a connectivity class of four have a high potential. Road connectivity was evaluated for the Providence Creek watersheds prior to this study (A. Korte, in preparation). The potential amount of

road sediment contributed to the stream in the Providence Creek watersheds was estimated by multiplying the mean sediment production rate by the total length of the111

road of a given surface, the mean wid th of the road, and the percent directly connected. In José Basin, the potential amount of road sediment contributed to the stream was estimated using a multivariate model predicting sediment production and multiplying the total potential sediment product ion from gravel surface roads by the percent of road length directly connected to the stream.

3.3.7. Road surveys Road surveys were conducted on 7.7 kilometers of roads in José Basin between 2007 and 2009 (Table 3.3). The sections to be surveyed were ide ntified after using

ArcGIS to break the road network into 269 sections that were 300 to 900 m in length. The sections were numbered and 20% of the sections were randomly selected (Figure 3.5). Each of the selected sections was surveyed following Tables 3 .3 to 3.5 unless it was paved or inaccessible because it was a private road. The percent bare soil and gravel surface were estimated for road sections surveyed that did not have sediment fences. Repeated road surveys also were conducted on approximately e ight kilometers of roads in José Basin that were graded in the summer of 2008 to determine the effect of grading on segment characteristics. The first survey was conducted prior to grading, and this was repeated immediately after grading and again in summ er 2009 to determine the changes that occurred over one water year.

3.3.8. Statistical analysis The main dependent variable was the annual sediment production rate from road segments (kg m - 2 yr - 1 ). Pairwise comparisons of road sediment production rates within a112

given water year were made between different road surface types in José Basin and in the Providence Creek watersheds. The effect of grading on road sediment production in José Basin was evaluated by pairwise comparisons for each water year. The validity of each comparison was assessed by comparing other key variables (e.g., segment slope, area, and percent bare soil) between groups. Pairwise comparisons also were made between bulk density values for each segment pre

- and post

- grading, and betwe en immediately

post

- grading and one year after grading. ANOVA tables were used to assess the relationships between each independent variable and the measured sediment production rates from gravel surface segments in José Basin. A multivariate linear regre ssion model to predict sediment production from gravel surface road segments in José Basin was constructed using ba ckward elimination procedures and a selection criteria of α = 0.10, and the validity of the model was assessed by comparing predicted sediment production rates to observed values.

3.4. Results 3.4.1. Precipitation Precipitation in the KREW watersheds fal ls largely as snow, though there is the potential for both rain and rain on snow events. Mean annual precipitation is approximately 1240 mm per year (Figure 3.6). In WY2004 annual precipitation in the Providence Creek watersheds was only 72% of normal, w hile annual precipitation was

141% of normal in WY2005 and 163% of normal in WY2006. WY2007 was the driest year with only 62% of the mean annual precipitation. WY2008 and WY2009 were 17% and 22% below normal, respectively.113 Mean annual precipitation for the Auberry rain gage is only 611 mm (California Department of Water Resources, 2010), or 49% of the mean annual precipitation for the Providence Creek watersheds. In WY2008 the annual precipitation at Auberry was only 458 mm or 75% of the mean, and this is consistent with the below normal precipitation in the Providence Creek watersheds. Mean precipitation for the four functioning rain gages in José Basin was 519 mm (standard deviation (s.d.) = 50 mm), or approximately 60 mm more than at Auberry (Table 3.6). Annual precipitation was not significantly correlated with elevation in José Basin for WY2008 (R 2 = 0.03, p = 0.84). The mean erosivity of the four gages in WY2008 was 630 MJ ha - 1 mm hr - 1 (s.d. = 90 MJ ha - 1 mm hr - 1 ). Erosivity was not correlated w ith elevation in WY2008 (R 2 = 0.008, p = 0.91 ). In WY2009 the annual precipitation at Auberry was 526 mm, or 86% of the mean. Mean precipitation for the three functioning rain gages in José Basin was 554 mm, which was 35 mm more than at Auberry, but the values in José Basin were more variable than in WY2008 as the standard deviation was 139 mm. Again the measured precipitation in José Basin was not significantly correlated with elevation (R 2 = 0.81, p = 0.29). There was no significant difference in ann ual precipitation between WY2008 and WY2009 in José Basin (p = 0.66). The mean erosivity in WY2009 was only 390 MJ ha - 1 mm hr - 1 (s.d. = 210 MJ ha - 1 mm hr - 1 ), and erosivity was again not correlated with elevation in WY2009 (R 2 = 0.15, p = 0.74 ). Erosivity in WY2009 was 38% of, and significantly less than, the erosivity in WY2008 (p = 0.09).114

3.4.2. Effects of road surface type on road sediment production and delivery 3.4.2.1. Sediment production

Providence Creek watersheds

The 6

- 13 native surface road segments with sediment fences had a mean elevation of 1860 m (s.d. = 85 m) and a range of 1750 m to 1960 m. Mean segment length was 45 m (s.d. = 13 m), and the mean slope was 10% (s.d. = 3%) (Appendix E). The segments averaged 49% bare soil (s.d. = 22%), while the remaining cover consisted of duff (mean = 35%, s.d. = 22%), gravel (mean = 10%, s.d. = 22%), and live vegetation (mean = 7%, s.d. = 6%). In WY2004 the mean sediment production rate of the 11 native surface road segments in the Providence Creek watersheds was 0.30 kg m - 2 yr - 1 (s.d. = 0.38 kg m - 2 yr -

1 ) (Figure 3.7; Appendix E). In WY2005 two more segments were monitored, and the mean sediment production rate was nearly three times greater than the prior year (p = 0.25). This increase can be attr ibuted to the 95% increase in precipitation (Figure 3.6) rather than the additional segments, as the two new segments had smaller sediment production rates than the mean value for the remaining 11 segments. Precipitation and mean sediment production was h igher in WY2006 than any of the other five years, as the mean production rate for the 13 native surface segments was 1.8 kg m - 2 yr - 1 (s.d. = 1.8 kg m - 2 yr - 1 ) (Figure 3.7). In WY2007 precipitation was lower than in any other year and the mean sediment prod uction rate for the six remaining native surface segments was only 0.039 kg m - 2 yr - 1 (s.d.= 0.091) or 2% of the value in WY2006 (p = 0.0019) (Figure 3.7). This was the lowest value for the six years of monitoring.115

Sediment production rates were similar f or the final two water years, averaging 0.12 and 0.14 kg m - 2 yr - 1 , respectively (s.d. = 0.14 and 0.12 kg m - 2 yr - 1 ). The seven gravel surface segments in the Providence Creek watersheds had 32% gravel cover on average (s.d. = 8%), which was more than thre e times the amount of gravel on the native surface segments. Consequently, the gravel surface segments averaged only 19% (s.d. = 9%) bare soil as compared to 48% for the native surface segments. The remaining road surface was covered with duff (mean = 40 %, s.d. = s.d. = 14%) and vegetation (mean = 10%, s.d. = 8%). The gravel surface segments had similar segment areas and slopes as the native surface segments (Appendix E). Mean annual sediment production for the seven gravel surface segments in the

Provid ence Creek watersheds in WY2004 and WY2005 was respectively 13% and 17% of the mean rate for the native surface segments, and this difference was significant (p = 0.017 and 0.045) (Figure 3.7). In WY2006 the mean sediment production rate from gravel surfa ce segments was 29% of the mean rate from native surface segments, which was a smaller but still significant difference compared to the native surface segments (p = 0.018). In WY2007 and WY2009 the mean sediment production rate from gravel surface

segment s was equal to the mean rate from native surface segments, while in WY2008 the mean sediment production rate from gravel surface segments was 49% of the mean rate from native surface segments (p = 0.30).

The inter annual pattern for sediment production rate s from gravel surface segments was generally very similar to the pattern for values from native surface segments. In WY2004 the mean sediment production rate for the gravel surface segments was 0.04 kg m - 2 yr - 1 , while in WY2005 and WY2006 the mean value w as 3.5116

and 3.7 times larger, respectively. This is similar to the 2.8

- and 2.2

- fold increases for the mean values from native surface segments for the same two water years. Similar to the native surface segments, the mean sediment production rate for gra vel surface segments was highest in WY2006, the wettest year, and lowest in WY2007, the driest year. A different pattern was only evident in WY2008 and WY2009, when sediment production rates from native surface segments were nearly equal while there was a 2.5

- fold increase in mean sediment production for the gravel surface segments. The four mixed surface road segments in the Providence Creek watersheds averaged 23% bare soil (s.d. = 15%), 21% gravel (s.d. = 8%), 21% pavement (s.d. = 7%), and 38% duff (s .d. = 19%). Their mean length was 95 m (s.d. = 38 m), or 2.1 times the mean length of the native surface segments, while their mean slope was 10% (s.d. = 1%), which was the same value as the native surface segments (Appendix E). Sediment production from the four mixed surface road segments tended to be binary, with PM1 and PM5 having sediment production rates typically one to three orders of magnitude higher than PM3 and PM4. Rills at least 8 m long formed on the two segments with higher sediment produc tion rates, though a rill that was 16 m long and 0.8 m deep also formed on PM4. Mean annual sediment production rates from mixed surface segments were 43

- 62% that of native surface segments from WY2004 to WY2007. In WY2008 the mean annual sediment produc tion rate for mixed surface roads was 0.31 kg

m - 2 yr - 1 (s.d. = 0.26 kg m - 2 yr - 1 ), or 4.3 times that of the native surface segments. Though precise measurements were not taken, a significant amount of erosion was observed at the knickpoint of the largest r ill on PM1, which had a sediment production rate of 0.58 kg m 2 yr - 1 , or 1.7 times any of the native surface segments in that year (Appendix E). In117

WY2009 the mean sediment production rates from native, gravel, and mixed surface segments were nearly ident ical (Figure 3.7). The ditches with sediment fences were on insloped, paved road segments that averaged 90 m long (s.d. = 50 m), twice as long as the native and gravel surface road segments. The mean segment slope was 7% (s.d. = 3%), which is slightly lower than the mean slope of 8

- 11% for the three other surface types. In each segment the ditches extended the entire length of the segment, and the mean ditch width was 1.0 m (s.d. = 0.2 m). In each year, the mean sediment production from the ditche s was at least an order of magnitude lower than the mean values for any of the other three road surface types (Figure 3.7). The six

- year average was only 0.020 kg m - 2 yr - 1 (s.d. = 0.090 kg m - 2 yr - 1 ), but in the wettest year (WY2006) this more than quadrup led to 0.090 kg m - 2 yr - 1 (s.d. = 0.22 kg m - 2 yr - 1 ). The interannual variations were similar to the other road surface types,

as the values increased from WY2004 to WY2006. The smallest value was in the driest year (WY2007), when none of the ditches produ ced any sediment.

José Basin The number of native surface road segments with valid sediment production measurements ranged from 13 in WY2008 to 30 in WY2009. The mean elevation of these segments was 1056 m (s.d. = 83 m), 800 m lower than the mean elevat ion of the native surface segments in the Providence Creek watersheds. Mean segment area was

115 m 2 (s.d. = 44 m 2 ), which is less than the value of 168 m 2 for native surface segments

in the Providence Creek watersheds (p = 0.37 ). Mean segment slope was 9 % (s.d. = 4%),118

which is very similar to the mean value of 8% for the Providence Creek watersheds. Other than elevation, the only other major difference was that the native surface segments in José Basin averaged 70% bare soil (s.d. = 15%), as compared to 48% (s.d. = 17%) bare soil for the native surface segments in the Providence Creek watersheds (p < 0.0001). In WY2008 the mean sediment production rate for the native surface segments in José Basin was 1.4 kg m - 2 yr - 1 , but this was highly variable as t he standard deviation was 2.2 kg m - 2 yr - 1 (Figure 3.8; Appendix D). This is 2.5 times the mean value for the native surface segments in the Providence Creek watersheds, but the true difference would be even greater since 19 of the 32 sediment fences in Jo sé Basin overtopped. In WY2009 the mean sediment production rate for the 30 native surface segments in José Basin was 2.0 kg m - 2 yr - 1 (s.d. = 3.1 kg m - 2 yr - 1 ), or 43% higher than in WY2008 (Figure 3.8), even though the mean precipitation was only 6% grea ter (Table 3.6). The coefficient of variation was nearly identical at 155%. In WY2009 the mean sediment production from native surface road segments in José Basin was 14 times the mean value

from the Providence Creek watersheds. This ratio is believed t o be more representative than in WY2008 as no sediment fences overtopped. The number of gravel surface segments in José Basin with valid sediment production values ranged from five in WY2008 to 11 in WY2009. The mean area of the gravel surface road segmen ts was 114 m 2 (s.d = 44 m 2 ), and this was only nearly identical to the mean value for native surface segments in José Basin. However, the mean slope of the gravel surface segments was 13% (s.d. = 3%) as compared to 9% (s.d. = 3%) for the

native surface se gments, and this difference was significant (p = 0.0001). As expected, the gravel surface segments averaged 29% gravel (s.d. = 7%) and 51% bare soil (s.d. =119

12%) as compared to 4% gravel (s.d. = 8%) and 70% bare soil (s.d. = 15%) for the native

surface se gments (p < 0.0001 in each case). The remaining cover was mostly duff (mean = 19%) and only 1% live vegetation. The mean elevation of the graveled segments was 70 m higher than the mean elevation of the native surface segments (p = 0.0040), but this

diff erence is not believed to have a significant effect on sediment production (Chapter 2). In WY2008 the mean sediment production for gravel surface segments in José Basin was 3.6 kg m - 2 yr - 1 (s.d. = 1.9 kg m - 2 yr - 1 ), or 2.6 times the value for native surface segments (p = 0.06) (Figure 3.8, Appendix G). All five segments had sediment production rates greater than 1.0 kg m - 2 yr - 1 . JGH5 had a sediment production rate of 6.6 kg m - 2 yr - 1 , which was the highest sediment production rate for a gravel surface segme nt. JGH5 had only 23% gravel cover, as compared to 27

- 40% gravel cover for the other four segments with valid sediment data. In WY2009 the mean sediment production for gravel surface segments was only 0.7 kg m - 2 yr - 1 (s.d. = 1.0 kg m - 2 yr - 1 ), or 35% of the value for the native surface segments (Figure 3.8). The value of 0.7 kg m - 2 yr - 1 also was only 19% of the value for WY2008. Sediment production from the five segments with valid data in WY2008 produced only

2

- 51% as much sediment in WY2009, despite t he lack of a significant difference in annual precipitation. The low sediment production from gravel segments in WY2009 can probably be attributed to their location within José Basin, as eight of the 11 gravel segments were located near JRG2, which had an annual erosivity of only 160 MJ ha - 1 mm

hr - 1 . This was 290 MJ ha - 1 mm hr - 1 less than the WY2009 values for any of the other gages. Sediment production for each of these eight segments was less than 1.0 kg m - 2 yr 1 , while each of the remaining three segm ents were located near JRG4, which had an120

annual erosivity of 570 MJ ha - 1 mm hr - 1 in WY2009, and they each produced more than 1.0 kg m - 2 yr - 1 and. In WY2008 the mean sediment production rate for gravel surface segments in

José Basin was 60 times the mean v alue for the Providence Creek watersheds, and in

WY2009 there was a five

- fold difference (Figure 3.9). These large differences can be largely attributed to the difference in elevation and thus climate, as the mean length of the gravel surface segments in José Basin was 20% less than the gravel segments in the Providence Creek watersheds (p = 0.44). The mean slope was only slightly steeper at 13% (s.d. = 3%) as compared to 11% (s.d. = 6%) for the gravel segments in the Providence Creek watersheds (p = 0.21 ). The gravel surface segments in José Basin did average 51% bare soil, which was much more than the mean value of 19% for the Providence Creek watersheds (p = 0.0001), but the gravel surface segments in both areas averaged 29% gravel cover.

3.4.2.2. Pre dicting sediment production for gravel surface segments in José Basin Univariate analyses showed that annual sediment production from the gravel surface road segments in José Basin (n = 16) was significantly related to segment slope, segment area times slo pe (A*S), annual precipitation, annual erosivity, and percent bare soil (Table 3.7). The positive correlations between road sediment production and annual erosivity, annual precipitation, and the percent bare soil make physical sense. Annual erosivity ha d the strongest relationship with an R 2 of 0.45 (p < 0.01), and annual precipitation was also marginally significant at p = 0.08. The negative correlations between road sediment production and segment slope and area*slope did not make121

physical sense, and may be due to the location of longer, steeper fences in areas with higher annual erosivities. The multivariate model predicted annual sediment production from segment area (A in m 2 ), segment slope (S in m m - 1 ), percent bare (B), annual precipitation (P in mm), annual erosivity (E in MJ ha - 1 mm hr - 1 ), and segment area times slope (AS in m 2 m m - 1 ) (Table 3.8):

SP = 17

– 0.11*A

– 0.83*S + 5.63*B + 0.009*E+ 0.006*AS (equation 3.3) where SP is sediment production (kg m - 2 ) (Figure 3.10). The coefficients for most of these variables make physical sense, as sediment production is predicted to increase with increasing percent bare soil, erosivity, and segment area times slope. The negative relationship with area also was observed for native surface segments, as longer segments tended to have a flatter depositional area at the bottom. The predicted decrease in sediment production with an increase in slope does not make physical sense and is likely a statistical artifact. Therefore the multivariate model for pred icting sediment production from gravel surface segments in José Basin is:

SP =

- 1.3

– 0.005*A + 0.004*E + 4.4*B

– 0.0003*AS (equation 3.4). This explains 57% of the variability in sediment production from gravel surface segments (Figure 3.10). The applic ation of this model to the 2.5 km of surveyed gravel surface segments in José Basin yields a predicted sediment production rate of seven tons per year, or 2.8 tons per kilometer. On this basis the 29 km of gravel surface roads in José Basin are predicted to produce approximately 80 tons of sediment each year. In comparison, the multivariate model for predicting sediment production from native surface segments predicted that monitored native surface segments produced 10 tons per122

kilometer, and the 67 km of native surface roads in José Basin are predicted to produce 680 tons of sediment each year.

3.4.2.3. Sediment delivery

Providence Creek watersheds Fifty

- five percent of the 13.9 km of roads in the Providence Creek watersheds are

native surface. Draina ge features were present for 114 segments or 74% of the native surface road length, and the remaining 31 segments had no visible signs of sediment discharge. The mean length of the 114 drainage features was 20.4 m (s.d. = 14.6 m), but the mean was highly skewed by six drainage features over 50 m in length. The longest drainage feature was 94 m and this emanated from an 84 m long segment. Despite the frequency of drainage features, only eight segments or 4% of the native surface road length was directly connected to a stream (Figure 3.11). Multiplying the mean sediment production rate from native surface roads by the total native surface road length, the mean road width, and the percent that is directly connected to a stream, the potential sediment deliv ered from native surface roads in the Providence Creek watersheds was 470 kg yr - 1 . This is 35% of the total potential sediment delivered to streams from roads (Table 3.9). Only 11% of the roads in the Providence Creek watersheds are gravel surface.

Drai nage features were present for 76% of the gravel surface road length, which is very similar to the 74% value for native surface roads. The mean length of the drainage features was 16.5 m (s.d. = 15.9), which was 19% less than the mean length from the

nati ve surface roads (p = 0.21). There were fewer long drainage features, as drainage123

features longer than 20 m were found for only 21% of the road length. The longest plume was 88 m long from a 51 m segment, but this was the only drainage feature from a

gra vel surface road that was longer than 30 m. Eleven percent of the gravel surface road length was directly connected to the stream network as compared to 4% for the native surface roads (Figure 3.11). Gravel surface segments are estimated to contribute j ust 60 kg yr - 1 to the stream network in the Providence Creek watersheds, which is only 4% of the total estimated sediment delivery from roads (Table 3.9).

Mixed surface roads accounted for 20% of the road network in the Providence

Creek watersheds. Draina ge features were present for 71% of the road length, and this was similar to native and gravel surface roads. The mean length of the 33 drainage features was 20.9 m (s.d. = 15.6 m), which again is nearly equal to the value for native

surface roads. The m ixed surface roads, like native surface roads, had several longer drainage features, with 29% of the road length having drainage features longer than 25 m. Three segments had drainage features between 30 m and 40 m long, and one 34 m long segment had a dr ainage feature that was 90 m long. Thirty

- one percent of the mixed surface roads were directly connected to the stream network, and this was eight and three times more than the native and gravel surface roads, respectively (Figure 3.11; Table 3.9). The high sediment production rate and high connectivity means that mixed surface roads are estimated to contribute nearly 800 kg yr - 1 of sediment to streams in the Providence Creek watersheds, or 59% of the total (Table 3.9). Graveling all of the native surfa ce roads in the Providence Creek watersheds could reduce their sediment production by 78%.124 Fifteen percent of the Providence Creek road network is paved, and the paved roads are typically insloped with adjacent ditches. Only 21% of the paved road length had a sediment plume or rill, and three of the six drainage features were less than 10 m long. The longest drainage feature was nearly 43 m long, and this discharged from an 81 m long segment. Surprisingly, 16% of the paved roads were directly connecte d to the stream network, which was four times the rate of native surface roads (Figure 3.11). Since the sediment production rates are lower for ditches than any of the three road surface types, the ditches are estimated to contribute only 23 kg yr - 1 of se diment to the stream network,

or 1% of the total.

José Basin The road survey showed that 42% of the 159 km of roads in José Basin were native surface, 18% were gravel surface, and 41% were paved. Only 52 native surface segments, or 54% of the surveyed na tive surface road length, had a drainage feature (Figure 3.12). Drainage features from native surface road segments in José Basin were typically short, as only four segments had drainage features longer than 30 m. The mean length was 13.6 m (s.d. = 17.8 m), or 33% less than the mean length of drainage features from native surface roads in the Providence Creek watersheds. The longest drainage feature was 105 m and emanated from a 246 m long segment. Thirty percent of the native surface road length was d irectly connected to the stream network, which is nearly an order of magnitude more than in the Providence Creek watersheds (Figure 3.13). The higher connectivity in José Basin is because many125

of the roads are located near streams; the mean drainage featu re length of the connected segments was only 6.1 m (s.d. = 10.8 m). Gravel surface roads accounted for 41% of the road length surveyed in José Basin. Eighty

- four percent of the gravel surface road length had a drainage feature as compared to 54% for the native surface roads (Figure 3.12). Drainage feature lengths for the gravel surface segments were typically short, as 87% of the gravel surface road length had drainage features less than 10 m long. The longest drainage feature was only 22 m long, and t his came from a 45 m long segment. The connectivity classes for gravel surface roads also had a binary distribution, as 55% of the road length had a connectivity class of one and 40% of the road length was directly connected to the stream network (Figure 3.13).

3.4.2.4. Total potential sediment delivered from gravel surface segments in José Basin As calculated in the previous chapter using the multivariate model for predicting sediment production from native surface roads,, native surface roads are esti mated to contribute 210 tons of sediment per year to the stream network in José Basin (Table 3.9). This is 87% of the total potential sediment delivered from roads to streams (Table 3.9), and more than two orders of magnitude more than native surface segm ents in the Providence Creek watersheds. Native surface segments in José Basin are estimated to

contribute As calculated using the multivariate model for predicting sediment production from gravel surface roads, the 29 km of gravel surface roads in José Basin are predicted to produce 80 tons of sediment per year. Since 40% of the gravel surface segments are126

connected, up to 32 tons yr - 1 of sediment are delivered to the stream network from gravel surface roads. This is just 13% of the estimated sediment delivery from native surface segments. Since the gravel surface segments in José Basin have comparable sediment production rates and a 33% higher connectivity, most of the eight

- fold difference in sediment delivery between gravel and native surface roads is due to the much greater amount of native surface roads (67 km vs. 29 km). The remaining 3.2

- fold difference is due to differences in the derived models as well as differences in the representativeness of the monitored segments to all of the native and gravel surface segments in José Basin.

3.4.3. Effects of grading in José Basin 3.4.3.1. Effects of grading on segment characteristics Approximately eight kilometers were graded along six different roads in José Basin in summer 2008. Prior to grading , the mean length of the 124 segments was 65 m, but the variability was very high as the standard deviation was 104 m (Figure 3.14; Appendix H). Thirteen segments were greater than 100 m long, and the longest was 1124

m. There were 109 waterbars on these road segments, but the field assessment indicated that only 53% of the waterbars were functioning properly. Waterbar failure was due to

on

- segment deposition on the upslope side of the waterbar, rill erosion through the waterbar, and flow depth that exce eded the height of the waterbar. During grading 128 waterbars were either installed or reconstructed, and this decreased the mean segment length from 65 m to 41 m (Figure 3.14). Segment length

became much more uniform as the overall standard deviation d ropped from 104 m to 26 m. Only six segments were longer than 100 m, and the longest segment was 175 m.127 The repeat survey one year after grading showed an overall increase in mean segment length of 15% to 47 m, and a 31% increase in the overall standard deviation. The increase in mean segment length was true for all six roads. The increase in mean length and standard deviation was due to the failure of 28 waterbars, or 22% of the 128

waterbars installed or reconstructed in summer 2008. Waterbar failur e resulted in ten segments that were more than 100 m long and two segments longer than 200 m. Waterbar failure was again due to on

- segment deposition, rill erosion, and flow depths exceeding the height of the waterbar.

3.4.3.2. Effects of grading on sedi ment production The ungraded and graded native surface segments in José Basin had similar lengths and areas (Figure 3.15), but the two groups differed in slope and surface cover. The ungraded segments had an average of 9% slope (s.d. = 4%), while the grad ed segments averaged 14% slope, and this difference was highly significant (p < 0.0001) (Figure 3.15). The ungraded segments had 71% bare soil on average (s.d. = 15%), and the graded segments had 81% bare soil (s.d. = 14%). This significant difference (p = 0.0048) is due to the blading technique used in grading, which scrapes accumulated duff and vegetation growth off of the road surface. The ungraded and graded segments had only 4% and 5% gravel cover, respectively (s.d. = 8% and 6%).

In WY2008 the 13 ungraded native surface segments in José Basin had a mean sediment production rate of 1.4 kg m - 2 yr - 1 , but the data were highly skewed as indicated by the high standard deviation of 2.2 kg m - 2 yr - 1 (Figure 3.8; Appendix D). One ungraded segment (JNO6) did not produce any sediment and 11 of the 13 ungraded segments had128

sediment production rates less than 2 kg m - 2 yr - 1 , but one segment (JBT14) produced nearly 7.9 kg m - 2 yr - 1

. In WY2008, valid sediment production data were obtained from only three of the

ni ne graded segments in WY2008, as the sediment eroded from the other six segments overtopped the sediment fences. The mean sediment production rate for these three segments was 10.6 kg m - 2 yr - 1 (s.d. = 3.9 kg m - 2 yr - 1 ), or 7.7 times higher than the mean

va lue for the ungraded segments (p < 0.0001) (Figure 3.8; Appendix I). The range of values was from 6.1 to 13.0 kg m - 2 yr - 1

. In WY2009 the mean sediment production rate from the 30 ungraded native surface segments was 2.0 kg m - 2 yr - 1 (s.d. = 3.1 kg m - 2 yr - 1 ), or 43% higher than in WY2008 (Figure 3.8). One third of the segments had sediment production rates greater than 2 kg m - 2 yr - 1 . The sediment production rate for JNO3 was 12.9 kg m - 2 yr - 1 , which was the highest sediment production rate for an ungraded n ative surface road segment in

either WY2008 or WY2009. In WY2009 the mean sediment production for the 24 graded segments was 5.1 kg

m - 2 yr - 1 (s.d. = 4.9 kg m - 2 yr - 1 ), which is 2.6 times the mean value for the ungraded native surface segments (p = 0.0007 ) (Figure 3.8). Nine of the 24 graded segments had sediment production rates greater than 5 kg m - 2 yr - 1 . The sediment production rate for JBT19 was 20.4 kg m - 2 yr - 1 , which was the highest rate among the 297 segment

- years of data collected in this study b etween WY2004 and WY2009. Sediment production from the ungraded and graded road segments was significantly related to segment slope (R 2 = 0.36, p < 0.0001) (Figure 3.16). After normalizing sediment production by segment slope to account for the difference s in129

slopes between the ungraded and graded road segments, the graded road segments still produced 4.2 times more sediment per unit area than the ungraded segments in WY2008 (p = 0.01) and 1.6 times more sediment in WY2009 (p = 0.06) (Figure 3.17).

With respect to the six matched pairs of graded and ungraded segments (Table 3.10), the graded segments generally produced about five times more sediment than the ungraded segments (Figure 3.18). In one case, the graded segment generated 4.1 kg m 2

yr - 1 while t he ungraded segment produced no sediment. For the other five pairs the graded segments produced three to nine times more sediment than the ungraded segments. The graded segments did have 21% more area, 1% higher slope, and 40% more bare soil (Table 3.10) , but these differences only account for 42% of the observed differences using equation 3.4. The third comparison between graded and ungraded road segments was for four segments with one year of data prior to grading (WY2008) and one year of data after

gra ding (WY2009). Sediment production for segments JBT2 and JBT4 was three and nearly seven times greater in the year after grading, which is much more than the overall increase in sediment production of 47% for ungraded segments from WY2008 to

WY2009. In c ontrast, sediment production for segments JBT1 and JNU1 was much lower for the year after grading than the year before grading (Figure 3.19). The largest decline was for JNU1, which was graded by Southern California Edison, while the other three segments were graded by SNF. This variability is not readily explained, and indicates the need for sufficient replication in order to detect a significant effect. The change in sediment production after grading was evaluated over time for the

three native surfac e road segments graded in summer 2007. Sediment production130

decreased sharply from the first to the second year after grading for all three segments (Figure 3.20), as the mean value dropped from 10.6 kg m - 2 yr - 1 (s.d. = 3.9 kg m - 2 yr - 1 ) in the first year a fter grading to 5.3 kg m - 2 yr - 1 (s.d. = 3.9 kg m - 2 yr - 1 ) in the second year, or a mean decline of 52%. This decline occurred despite the 47% increase in sediment production for ungraded, native surface segments from WY2008 to WY2009.

3.4.3.3. Rill eros ion after grading Rills at least five centimeters deep formed on 31% of the 172 graded road segments within one year after grading. The length of the segments with newly

- formed rills ranged from 16 m to 243 m (mean = 55 m, s.d. = 45 m), and the mean lengt h of the segments with rills was 28% longer than the segments without rills (p = 0.03) (Table 3.11). The segments with rills had a significantly higher mean slope of 11% (s.d. = 4%) as compared to the mean slope of 8% for segments without rills (p = 0.000 4) (Table 3.11). The amount of bare soil was very similar for the segments with and without rills, but the segments with rills had a mean gravel cover of only 7% (s.d. = 11%), which was half of the mean value for the segments without rills (p = 0.017) (Ta ble 3.11). The mean total rill length for the 53 segments with rills was 19.2 m and the standard deviation was relatively high at 27.5 m. The mean was skewed by two segments with more than 110 m of rills. If these two segments are excluded, the mean ri ll length is 9.7 m. The mean rill volume for the 53 segments was 0.22 m 3 (s.d. = 0.41 m 3 ), while the

median was 0.08 m 3 . A survey of 17 segments in summer 2008 showed a mean road segment length above the rill initiation point of 9.0 m (s.d. = 7.1) and a range of 0 m to 24 m. Rills beginning at the very top of the segment were likely headcut after initiation.131

The slope of the road above the rill initiation point also was highly variable, as this ranged from three to 24% (mean = 13%, s.d. = 7%). For the area above the rill, the visually estimated percent bare soil ranged from 65

- 100% and the percent gravel cover

was from 0

- 35%. Rills formed in the first wet season after grading on all three segments with valid sediment production values. Rill volume w as measured on two of these segments, and

the mean value was 0.15 m 3 (s.d. = 0.05 m 3 ). The estimated mass of rill erosion was 196 kg or 46% of the measured sediment production on segment JBT8, and 319 kg or 49% of the measured sediment production on JBT9 (Table 3.12). In WY2009, 19 of the 24 graded segments with sediment fences developed rills. The 19 segments with rills had a mean sediment production rate of 2.1 kg m - 2 yr - 1 (s.d. = 2.3 kg m - 2 yr - 1 ), which was slightly higher than the mean value for the five graded road segments without rills (mean = 1.9 kg m - 2 yr - 1 , s.d. = 1.4 kg m - 2 yr - 1 ). The mean estimated mass of rill erosion from the 19 segments with rills was 98% (s.d. = 115%) of the measured sediment production (Table 3.12), but in six cases the estimated rill erosion was more than the measured sediment production. The high values may be partially due to deposition of the eroded sediment before reaching the sediment fence. Hence the median value of 47% may more accurately indicate the proportion of sediment that is due to rill erosion, and this value is very similar to the mean value in WY2008.

3.4.3.4. Effects of grading on road surface bulk density The mean bulk density for the 13 native surface road segments in José Basin immediately before grading was 1.56 g cm - 3 (s.d. = 0.17 g cm - 3 ). Immediately after132

grading the mean bulk density was 1.52 g cm - 3 (s.d. = 0.20 g cm - 3 ), which is only marginally lower (p = 0.66). The pairwise comparison for segments prior to and after grading showed that the mean bulk density for four segments decreased, the values for six segments stayed approximately equal, and the values for the remaining three segments increased (Figure 3.21). One year after grading the mean bulk density for the same 13 segments was 1.5 4

g cm - 3 (s.d. = 0.19 g cm - 3 ). Again, the pairwise comparison shows considerable variation among segments as bulk density decreased on three segments, increased on five segments, and was effectively unchanged for the other five segments (Figure 3.21).

3.4.3.5. Effects of grading on sediment delivery The survey of approximately six kilometers of road prior to grading showed that 32% of the road length was directly connected to the stream network, while 41% of the surveyed length had no visible drainage feature. The mean drainage feature length was 14 m, but this was highly variable as the standard deviation was 18 m.

Road

- stream connectivity decreased by more than half one year after grading, as only 13% of the surveyed road length was directly connec ted to a stream (Figure 3.22). This decrease is largely due to the breaking up of longer, hydrologically connected segments into shorter segments with no drainage feature.133

3.5. Discussion 3.5.1. Effects of graveling on sediment production and deli very Graveling is typically successful at reducing road sediment production in the Providence Creek watersheds, but there was considerable variability in the magnitude of its effectiveness between segments and between years. This variability can be attrib uted to variations in climate, surface cover, ad hoc maintenance, and segment characteristics. Over the six years of monitoring the mean sediment production rate for gravel surface segments was only 22% of the mean value for native surface segments. In WY2004 and WY2005 the gravel segments produced only 13

- 17% as much sediment as the native surface segments, but this value increased to 29% in WY2006, which was the wettest year in the study (Figure 3.7). In WY2007, which was a very dry year, there was

no significant difference in sediment production between the gravel and native surface segments (Figure 3.7). However, one segment, PG3, produced 0.23 kg m - 2 in WY2007, which was more than an order of magnitude greater than any other gravel surface

segment in WY2007. The cause of this high value is unknown, as this segment did not produce significantly more sediment than the other gravel surface segments in any of the other five years of monitoring. If this datum from segment PG3 is excluded, the mean

sed iment production from the gravel surface segments in WY2007 was again 18% of the mean value from the native surface segments, or very similar to the values from WY2004

and WY2005. In WY2008 and WY2009 there was no significant difference in the mean

sedim ent production rate between the native and gravel surface road segments. The sediment production from gravel surface segments among sites varied widely, with134

values ranging from zero to 0.3 kg m - 2 in WY2008 and 0.01 to 0.4 kg m - 2 in WY2009. In both years the sediment production from one graveled segment (PG2) was two to three times higher than any of the other graveled segments. The sediment fence for this segment was constructed 10

- 15 meters downslope of the road, and rilling between the

fence and the r oad probably increased the amount of sediment captured in the sediment fence. If this segment is excluded, the mean sediment production from gravel surface segments in WY2008 was 18% of the mean value for native surface segments, which again is nearly ide ntical to values in WY2004 and WY2005, and this difference was nearly significant (p = 0.12). In WY2009 there was some ad hoc road maintenance on two gravel surface segments, PG1 and the afore

- mentioned PG2. This included digging trenches for drainage an d filling deep ruts with logs, and the sediment production from these two segments was respectively 2.6 and 5.3 times the mean value of 0.08 kg m - 2 (s.d. = 0.07 kg

m - 2 ) from the other five gravel segments. The increased sediment production for these

two s egments indicates that even small disturbances to the road surface can increase road sediment production. A third gravel segment, PG7, had a sediment production rate that was an order of magnitude higher than the maximum value for the other four untreated gravel surface segments (0.19 kg m - 2 versus 0.05 kg m - 2 ). As with segment PG3 in WY2007, segment PG7 did not produce more sediment in the other five water years than the mean value from the other gravel segments. The increase in sediment production

from this segment may be due to concentrated flow in the tire treads observed on this segment, or possibly cutslope erosion. The outliers in WY2007 and WY2009 serve as135

reminders that there is a great deal of uncertainty in predicting road sediment production, and the inclusion or omission of one or two sites can greatly alter the results. Gravel should reduce road sediment production by protecting the underlying road surface from rainsplash and reducing shear stress by slowing overland flow velocities.

The fi ve

- fold reduction in sediment production on the gravel segments in the Providence Creek watersheds was surprising as the percent gravel cover averaged only 29% and was generally only one rock deep. However, the runoff rates in the Providence Creek

watersh eds are generally low as the area is snow dominated, and a thin gravel layer may be relatively effective in reducing road surface runoff. As runoff rates increase, the effectiveness of this thin layer of gravel may be expected to decline, as the runoff is able to erode through, or detach and transport, the thin gravel layer. Sediment production from gravel surface roads was much higher in the rain

dominated José Basin than in the Providence Creek watersheds. Mean annual sediment production for gravel se gments in José Basin were 60 and 5 times higher in WY2008 and WY2009, respectively. This difference is consistent with the 12

- 13 fold difference in mean sediment production between the native surface segments in José Basin and the native surface segments in the Providence Creek watersheds (Chapter 2). Unlike the Providence Creek watersheds, graveling was not successful in reducing road sediment production in José Basin, even though the mean gravel cover was 29% in each study area. The two

- year mean sedi ment production rate for the gravel segments in José Basin was nearly equal to the mean value for the native surface segments. The muted effect of graveling in José Basin can be attributed to higher annual erosivities and the average of 51% bare soil on t he road surface as compared to only 18%136

bare soil for the gravel segments in the Providence Creek watersheds. The lower percent bare soil for the gravel segments in the Providence Creek watersheds can be attributed to the denser forest cover at the higher elevations and the very low traffic levels, resulting in 40% litter cover. Like gravel, litter can protect the surface from rainsplash detachment and can slow the flow velocity, reducing sheetwash and rill erosion. To be effective the gravel must be si zed so that it is not easily detached by rainsplash or overland flow, and have interlocking faces rather than rounded. It also should cover the entire travelway and any inside ditch. The highest shear stress can be approximated from the rainfall intensit y, contributing area, and slope, as road surface infiltration is negligible (Luce and Black, 1999). The ineffectiveness of graveling in José Basin indicates the need for more than 30% gravel cover and a gravel cover that is more resistant to the predicted shear stress based on the design rainfall intensity. With climate change the amount and intensity of rainfall in the Providence Creek watersheds may increase, and the existing gravel cover can be expected to be less effective in reducing road sediment pr oduction.

3.5.2. Effects of grading and waterbar installation in José Basin on sediment production and delivery Grading is a routine maintenance technique for increasing drivability, but the results show that this greatly increases sediment production and can lead to an increase in the amount of sediment delivered to the stream network. In José Basin graded roads produced eight and three times more sediment per unit area than the ungraded road segments in WY2008 and WY2009, respectively. Among the matche d pairs grading137

increased sediment production by three to nine times. A smaller increase was measured in the northern Sierra Nevada, where recently

- graded road segments produced approximately two times more sediment per unit erosivity (p = 0.02) (Coe, 200 6), and in the U.S. Virgin Islands, where graded segments produced 2.5 times more sediment per unit precipitation than comparable ungraded road segments (Ramos

- Scharrón and MacDonald, 2005). As with graveling, the effects of grading appear to vary with climate as this affects the amount and type of precipitation. In the Eldorado National Forest, graded segments produced eight times more sediment than ungraded segments at elevations below 1400 m (p = 0.0008), while at elevations above 1400 m there was no significant difference in sediment production between graded and ungraded roads (Coe, 2006). The large difference found at the more rain dominated lower elevations is directly comparable to the large differences observed in José Basin, which also is belo w 1400 m. Since no grading was done in the KREW watersheds, it is not possible to determine how the grading effect would differ with elevation and climate, but the six

- year record of road sediment production in the KREW watersheds would provide an excelle nt opportunity to quantify the effects of grading. The results indicate that whenever possible, the frequency of grading should be reduced to decrease the frequency of the increase in sediment production. Furthermore, the effect of grading is of particu lar concern in wetter, rain dominated areas because the potential increase in sediment production is likely to be higher than in higher elevation,

snowmelt dominated areas.138 While grading usually increases sediment production, it can decrease sediment

deli very by the associated installation and repair of waterbars. Waterbars can both reduce sediment production by breaking up longer segments, and reduce sediment delivery by directing road discharge onto hillslopes and away from the streams. In José Basin, 32% of the road length was connected to the stream prior to grading, while after grading only 13% of the road length was connected. This 2.5

- fold decrease in delivery did not fully compensate for the three to eight

- fold increase in sediment production, su ggesting that grading would result in a potential 20

- 320% increase in sediment delivery. Grading may have been more successful in reducing road sediment delivery in José Basin if less than 22% of the newly installed and repaired waterbars had not failed the first year after grading. The failure of the waterbars was due to wheel ruts or rill erosion through the waterbars, sediment deposition upslope of the waterbar, and flow depths that exceeded the height of the waterbar. The management implications ar e that waterbars should: 1) be as high and as densely compacted as possible while continuing to allow traffic in order to maximize the likelihood that they will be effective over time; and 2) they must have a sufficient cross

- slope gradient to carry the se diment off the road instead of allowing it to accumulate on the road upslope of the waterbar. Restricting driving in wet conditions will also reduce waterbar failure, as this is will greatly reduce the chance of wheel ruts cutting through the waterbar. The larger increases in sediment production relative to the decrease in sediment delivery suggest that grading should be minimized in José Basin. A reduction in the frequency of grading to reduce sediment production rates also was recommended for

roads o n St. John (Ramos

- Scharrón and MacDonald, 2005), state forest roads in Oregon139

(Mills et al., 2007), and roads in western Montana (Sugden and Woods, 2007). The need for grading also can be reduced by restricting road use and construction during wet periods , as this reduces rut formation and helps maintain the drivability of the road (Barrett and Conroy, 2002; Sugden and Woods, 2007).

3.5.3. Monitoring and management The relative variability in sediment production between years and between sites

can be us ed to help determine the most efficient strategy for measuring road sediment production

— is it better to monitor more sites for fewer years, or fewer sites for more years? The mean annual sediment production from gravel surface segments for the six

years o f monitoring in the Providence Creek watersheds ranged from 0.04 kg m - 2 to 0.15 kg m - 2 , and the coefficient of variation for the mean annual sediment production was 1.2. These annual mean values were very similar to the annual mean values of 0.01 kg m - 2 t o 0.21 kg m - 2 measured for gravel road segments in the Idaho batholith (Burroughs and King, 1989). The coefficient of variation between sites within years varied from 0.8 to 2.2 and averaged 1.4 (s.d. = 0.5). Sediment production from native surface segm ents in the Providence Creek watersheds was skewed, as the overall mean was 0.72 kg m - 2 yr - 1

, while the median was only 0.21 kg m - 2 yr - 1 . In the northern Sierra Nevada, mean erosion rates were also skewed by a select few gravel surface segments, so that t he median value for the 30 segment

- years was 0.0009 kg m - 2 yr - 1 while the mean value was over an order of magnitude higher at 0.12 kg m - 2 yr - 1 (Coe, 2006). The slightly higher coefficient of variation between sites than between years in the Providence Cre ek watersheds suggests140

that the most efficient strategy for measuring road sediment production may be to have more sites with fewer years of monitoring, although multiple years are needed to capture at least some of the interannual variability and more ext reme values. The skew and high inter

- site variability also indicates that it is often just a few segments that contribute the highest sediment yields to the stream, and so practices to reduce road sediment delivery first need to pinpoint segments with hi gh sediment production and delivery potential. As previously discussed, the higher

- producing segments are typically larger, steeper segments with extensive rilling. These types of segments that feed into stream crossings or are in close proximity to stre ams should be the highest priority for treatment. Segments with cutslope erosion and segments with tire treads that can concentrate overland flow also should be targeted. Sediment reduction strategies should focus on rocking and/or outsloping these segme nts, and reducing the accumulation and delivery of overland flow by outsloping or installing waterbars.

3.6. Conclusions Sediment production and delivery from forest roads was monitored for 249 road

segment

- years in the southern Sierra Nevada of Califor nia. From WY2004 through WY2009, sediment production rates were monitored on native, gravel, and mixed surface roads, as well as from ditches adjacent to paved roads in the Providence Creek watersheds (1485 m to 2005 m) of the Kings River Experimental Wat ershed. For two water years, sediment production rates also were monitored from native surface, gravel surface, and recently

- graded road segments in José Basin, which is a lower elevation, rain dominated watershed. Road characteristics were surveyed in t he two areas, and potential141

delivery was determined by surveying drainage features leaving the road surface and determining road

- stream connectivity. In the Providence Creek watersheds, graveling was typically successful at reducing road sediment productio n, but this difference was sometimes muted by individual segments with high values. Graveling all of the native surface roads in the Providence Creek watersheds could reduce their sediment production by 78%. In contrast, the gravel surface segments in Jo sé Basin did not produce significantly less sediment than the native surface segments. The thin gravel layer found in the study areas is less or ineffective at reducing road sediment production in wet years and areas with higher annual erosivity. To be e ffective, the gravel segments in José Basin will need more than 30% gravel cover and gravel that is either deeper or larger. The graded road segments in José Basin produced three to eight times more sediment than ungraded segments. Rill erosion is estim ated to account for approximately half of the sediment produced in the first year after grading. Grading initially decreased the mean segment length by 37%, but mean segment length increased 15% in the first year after grading due to the failure of 22% of the constructed and reinstalled waterbars. The large increase in sediment production coupled with the smaller decrease in connectivity resulted in an estimated 20

- 320% increase in sediment delivery in the year after grading. The frequency of grading shou ld be reduced as much as possible in José Basin to decrease the occurrence of a sediment pulse to the stream network. Waterbars of adequate height and cross

- slope must be constructed or repaired during grading to reduce delivery. Perhaps the most benefic ial best management practice to reduce sediment142

production from roads is to restrict traffic under wet conditions, as this will reduce waterbar failure and the need for grading.143

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3.8. Tables Table 3.1. Number of native, gravel, and mixed surface road segments and ditches adjacent to paved roads that were monitored for sediment production in the Providence Creek watersheds from WY2004 to WY2009. Water year 200 4 2005 2006 2007 2008 2009 Total s Native surface road segments 11 13 13 6 6 6 55 Gravel surface road segments 7 7 7 7 7 7 42 Mixed surface road segments 4 4 4 4 4 4 24 Ditches adjacent to paved roads 7 7 7 7 7 7 42149

Table 3.2. Number of native, gravel, and graded road segments in José Basin with valid sediment production values in WY2008 and WY2009. Water year 2008 2009 Totals Native surface road segments 13 30 43 Gravel surface road segments 5 11 16 First year post

- grading 3 24 27 Second year post

- grading 0 3 3150

Table 3.3. Road segment characteristics measured, estimated, or o bserved for each segment with a sediment fence and the surveyed road segments. /E indicates that the characteristic was estimated rather than measured in the surveys conducted on segments that were not monitored for sediment production.

Characteristic Me asured (M), estimated (E), or observed (O) Continuous (C)

or categorical group (G) Method of

measurement Length (m) M C Meter wheel Surface type (Native, Gravel) O G Active width (m) M C Cloth tape Total width (m) M C Cloth tape Slope (%) M C Clinome ter Bare soil (%) M / E C Cover count Gravel cover (%) M / E C Cover count Traffic level (Very low, Low, Medium) E G Evidence of past surface rocking (Y/N) O G Cutslope height (m) E C Cutslope gradient (%) M C Clinometer Cutslope percent bare soi l (%) E C Slope of upper hillslope (%) M C Clinometer Slope of lower hillslope (%) M C Clinometer Ditch width (m) M C Cloth tape Ditch slope (%) M C Clinometer Rill length (m) M C Cloth tape Rill width (m) M C Ruler Rill depth (m) M C Ruler Drain type (see Table 3.4) O G Drain feature (see Table 3.4) O G Drain armoring (Y/N) O G Water cross armoring (Y/N) O G Armoring buried (Y/N) O G Armoring intact (Y/N) O G Pushout present (Y/N) O G Pushout effective (Y/N) O G Fillslope erosion ( Y/N) O G Maximum fillslope rill depth (m) M C Ruler Multiple fillslope rills (Y/N) O G Drainage feature length (m) M C Cloth tape Drainage feature slope (%) M C Clinometer Drainage feature roughness (1,2,3,4) O C Connectivity class (1,2,3,4) O G Culvert present (Y/N) O G Culvert plugged (%) E C Scour at culvert outlet (Y/N) O G Volume of scour at culvert outlet (m 3 ) M C Cloth tape151

Table 3.4. Drain type and drain feature categories used to describe each road segment. Slashes indicate a mi xture of types or features within a road segment where flow was restricted to one discrete drainage point by berms and/or the cutslope.

Drain types Drain features Insloped Diffuse Outsloped (diffuse) Dip Outsloped (with a berm) Pushout Planar Waterba r Through cut Stream crossing Insloped/Planar Cattle guard Insloped/Outsloped with a berm On segment deposition Outsloped with a berm/Planar Intersection Planar/Outsloped Diffuse/Dip Insloped/Outsloped/Planar Diffuse/Waterbar Diffuse/Pushout Diff use/Intersection Diffuse/On segment deposition Dip/Pushout Dip/On segment deposition Cattle guard/Pushout Intersection/On segment deposition152

Table 3.5. Definition of each connectivity class and the associated potential for runoff and sediment to be delivered to the stream network. Connectivity Definition Potential for class sediment delivery 1 Drainage feature <10 m long. Very low

2 Drainage feature <20 m long. Low/moderate

3 Drainage feature >20 m long but more than 10 m from a strea m channel. Moderate/high

4 Drainage feature to within 10 m of a stream channel, regardless of length. High153

Table 3.6. Elevation and annual precipitation and erosivity for the functioning rain gages in José Basin in WY2008 and WY2009.

– indicates that t he gage did not collect valid data for that water year. Rain gage Elevation (m) Precipitation (mm) Erosivity (MJ ha - 1 mm hr - 1 ) WY2008 WY2009 WY2008 WY2009 JRG1 1050 462

-- 674

-- JRG2 1100 581 403 732 160 JRG3 1120 501

-- 522

-- JRG4 1250

-- 677

- - 568 JRG5 1000 533 582 603 449 Mean (s.d.) 1100 (90) 519 (50) 554 (139) 633 (91) 393 (210)154

Table 3.7. Correlation coefficients, coefficients of determination, and p values for the regressions between key site variables and annual sediment production f rom gravel surface road segments in José Basin. Values in bold are significant at p ≤ 0.10.

Variable r R 2 p value Length (m)

- 0.40 0.17 0.12 Area (m 2 )

- 0.42 0.17 0.11 Slope (%)

- 0.48 0.23 0.06 Area*slope (m 2 )

- 0.54 0.29 0.03 Percent bare soil 0.48 0.23 0.06 Percent gravel cover

- 0.05 0.00 0.90 Elevation (m)

- 0.40 0.16 0.13 Annual precipitation (mm) 0.44 0.20 0.08 Erosivity (MJ ha - 1 mm hr - 1 ) 0.67 0.45 <0.01 Rill length (m)

- 0.37 0.14 0.15 Rill volume (m 3 )

- 0.29 0.09 0.27155

Table 3.8. Signi ficance of the variables in the multivariate model for predicting sediment production from gravel surface road segments in José Basin.

Variable p value Annual erosivity (MJ ha - 1 mm hr - 1 ) 0.0003 Segment area (m 2 ) 0.0004 Segment slope (%) 0.0008 Segment area*slope (m 2 m m - 1 ) 0.0014156

Table 3.9. Mean sediment production rate, road length, mean width, and proportion of the road surface directly connected to the stream network for native, gravel, mixed surface roads, and road ditches in the Providence Cre ek watersheds. *The potential sediment delivered and the proportion of total potential delivered sediment in José Basin were predicted by the multivariate models, rather than by using mean sediment production rates.

Mean sediment production rate (kg m - 2 yr - 1 ) Road

length (km) Mean road

width (m) Proportion

connected Potential

sediment delivery (kg yr - 1 ) Proportion of

total potential delivered sediment Providence Creek watersheds Native surface roads 0.78 7.6 2.2 0.04 470 0.35 Gravel surface roads 0.16 1.5 2.3 0.11 60 0.04 Mixed surface roads 0.35 2.8 2.6 0.31 800 0.59 Ditches adjacent to paved roads 0.02 2.1 3.5 0.16 20 0.02 Total sediment contribution from roads 1,350 José Basin Native surface roads 1.7 67 2.6 0.30 210,000 0.88 Gravel s urface roads 1.6 29 2.6 0.40 30,000 0.13 Total sediment contribution from roads 240,000157

Table 3.10. Characteristics of and sediment production rates for the six matched pairs of ungraded and graded road segments i n José Basin.

Road segment Ungra ded

or Graded Length

(m) Width

(m) Area

(m 2 ) Slope

(%) A*S Percent

bare soil Percent

gravel Sediment

production rate (kg m - 2 yr - 1 ) JNH5 Ungraded 36 2.5 89 12 1068 66 1 0.0 JNH4 Graded 44 2.6 114 13 1482 84 2 4.1 JPS15 Ungraded 31 2.7 84 4 336 73 0 0. 2 JPS16 Graded 45 3.4 153 5 765 94 0 0.7 JPS18 Ungraded 70 2.4 168 8 1344 46 0 0.1 JPS17 Graded 85 2.4 204 10 2040 78 0 0.6 JPS19 Ungraded 28 2.5 70 10 700 49 0 0.2 JPS20 Graded 16 2.7 43 10 430 94 0 0.8 JPS21 Ungraded 28 2.2 62 10 620 54 1 0.3 JPS2 2 Graded 32 2.8 90 10 900 82 1 3.0 JNH11 Ungraded 30 3 90 10 900 73 10 0.4 JPS23 Graded 29 2.7 78 13 1014 73 13 1.7 Mean (s.d.) Ungraded 37 (16) 2.6 (0.3) 94 (38) 9 (3) 828 (355) 60 (12) 2 (4) 0.2 (0.1)

Graded 42 (24) 2.8 (0.3) 114 (58) 10 (3) 1105 ( 572) 84 (8) 3 (5) 1.8 (1.4)158

Table 3.11. Segment and rill characteristics for 119 unrilled road segments and 53 rilled road segments one year after gradin g, and the p values for each comparison.

Segment Segment Percent Percent Drainage Ineffective Rill Rill length slope bare gravel feature length bars/dips length volume (m) (%) (m) per km (m) (m 3 ) No rills present (5,144 m) Mean 43 8 82 14 10 2.3

-- -- s.d. 27 4 19 18 14

-- -- Rills present (2,934 m) Mean 55 11 86 7 17 5.5 19 0.22 s.d. 4 5 4 12 11 15 28 0.41 p values 0.03 0.0004 0.19 0.02 0.01

-- --159

Table 3.12. Rill volume, bulk density, rill erosion, measured sediment production, and the ratio of rill erosion relative to the mass of sediment collected in the sediment fence. All se gments were graded one year earlier, and NA indicates that no rill erosion was present.

Year Road Rill Bulk Rill Sediment Ratio of rill erosion graded segment volume density mass production to sediment

(m 3 ) (g cm - 3 ) (kg) (kg) production

2008 JBT 8 0.12 1.69 196 428 0.46 JBT9 0.18 1.74 319 658 0.48

2009 JBT1 0.04 1.66 66 89 0.74 JBT2 0.81 1.66 1344 1025 1.31 JBT3 0.08 1.79 141 470 0.30 JBT4 0.1 1.79 178 818 0.22 JBT5 0.21 1.8 380 622 0.61 JBT6 0.07 1.3 87 76 1.14 JB T7 0.17 1.57 260 831 0.31 JBT11 0.91 1.56 1421 2480 0.57 JBT12 0.7 1.32 922 433 2.13 JBT13 NA 1.38 NA 258 NA JBT14 0.11 1.38 157 333 0.47 JBT17 0.46 2.34 1089 862 1.26 JBT18 3.05 1.37 4184 1375 3.04 JBT19 4.44 1.61 7140 1549 4.61 JBT20 NA 1 .75 NA 201 NA JBT21 0.34 1.33 456 1090 0.42 JNH4 0.06 1.35 84 367 0.23 JNH6 0.14 1.35 189 553 0.34 JNU1 NA 1.29 NA 10 NA JNU2 NA 1.59 NA 115 NA PS16 0.01 1.16 16 103 0.16 PS17 NA 1.43 NA 132 NA PS20 NA 1.43 NA 34 NA PS22 0.06 1.67 99 269 0.37 PS23 0.04 1.52 55 136 0.40 Mean 0.58 1.55 894 567 0.93 s.d. 1.11 0.24 1706 565 1.10160

3.9. Figures

Figure 3.1. Location of the national forests in California, including the Eldorado and the Sierra National Forest (SNF). Inset is Sierra Na tional Forest, showing José Basin and the Kings River Experimental Watersheds (KREW). X indicates the location of the Auberry precipitation gage (CA map from http://www.fs.fed.us/r5/forests.shtml).161

Figure 3.2. Map of the four Providence Creek watersh eds in the Kings River Experimental Watersheds (KREW) and the sediment fences used to monitor hillslope and road sediment production. Contributing areas for the hillslope sediment fences are shown in blue. The sediment fences along the main east

- west roa d in the upper part of the map are measuring sediment production from the ditches adjacent to this insloped, paved road. (Map courtesy A. Korte).162

Figure 3.3. Roads (in black) and streams (in blue) in José Basin.163

Figure 3.4. One or more sediment fences were installed at the drainage point of road segments in José Basin and the Providence Creek watersheds. The fence in the foreground was installed in summer 2007 in José Basin just below a waterbar draining a native surface roa d segment, and the second fence was added in summer 2008 to prevent overtopping.164 Figur e 3.5. Twenty percent of the road network in José Basin was randomly selected and surveyed. Selected sections are black and the remainder of the road network is shown in grey.165

Figure 3.6. Mean annual precipitation for the Providence Creek watersheds for WY2004 to WY2009. Error bars represent one standard deviation.166

Figure 3.7. Mean annual sediment production in the Providence Creek watersheds for WY2004 t hrough WY2009 for native, gravel, and mixed surface road segments as well as ditches adjacent to paved, insloped road segments. Error bars represent one standard deviation.167

Figure 3.8. Mean sediment production rates in José Basin for WY2008 and WY20 09 for ungraded native surface road segments, gravel surface road segments, and road segments one and two water years after grading, respectively. Error bars indicate one standard deviation.Figure 3.9. Mean sediment production rate for native and gra vel surface road segments

in José Basin and the Providence Creek watersheds for WY2008 and WY2009. Error bars indicate one standard deviation.169

Figure 3.10. Observed versus predicted sediment production rates (kg m - 2 yr - 1 ) for gravel surface segments in José Basin. Line shows a 1:1 relationship.170

Figure 3.11. Hydrologic connectivity classes for native, gravel, and mixed surface road segments in the Providence Creek watersheds as well as ditches adjacent to paved roads. 1 indicates a drainage feat ure less than 10 m long and at least 10 m from a stream channel, and 4 indicates that a segment is connected to the stream channel.171

Figure 3.12. Cumulative proportion of road length versus drainage feature length for native and gravel surface roads in José Basin.172

Figure 3.13. Hydrologic connectivity classes for native and gravel surface roads in José Basin. 1 indicates a drainage feature less than 10 m long and at least 10 m from a stream channel, and 4 indicates a segment is connected to the s tream channel.173

Figure 3.14. Mean segment lengths for six roads in José Basin prior to grading, immediately after grading, and one water year after grading. Error bars indicate one standard deviation. The standard deviation on 9S307 prior to grading w as 300 m.174

Figure 3.15. Box and whisker plots of a) segment areas and b) segment slopes for the ungraded and graded road segments with valid sediment production data in José Basin. Boxes represent the 25% and 75% quartiles, lines represent the medians , plus signs represent the means, and the whiskers represent minimums and maximums.175

Figure 3.16. Annual sediment production versus segment slope for the ungraded and graded native surface segments in José Basin for WY2008 and WY2009.176

Figure 3.17. Mean sediment production rates normalized by slope for ungraded and graded segments in WY2008 and WY2009. The differences were significant for both WY2008 (p = 0.01) and WY2009 (p = 0.04).177

Figure 3.18. Sediment production for WY2009 for each of the six matched pairs of ungraded and graded segments in José Basin.17 8

Figure 3.19. Annual sediment production for four segments in José Basin for the year prior to grading (WY2008) and the year after grading (WY2009).179

Figure 3.20. Sediment productio n rates in the first and second water year after grading for three segments in José Basin.180

Figure 3.21. Mean bulk density for 13 road segments prior to grading, immediately after grading, and one year after grading. Error bars display one standard d eviation.181

Figure 3.22. Hydrologic connectivity classes for six kilometers of road in José Basin prior to grading and one year after grading. 1 indicates a drainage feature less than 10 m long and at least 10 m from a stream channel, and 4 indicates a segment is connected to the stream channel.182

5. Appendices Appendix A. Characteristics and sediment production rates for hillslopes in José Basin by soil type.

Hillslope Axis Area Axis Mean Fence Sediment

length slope side slope elevation production rate (m) (m 2 ) (%) (%) (m) (kg m - 2 yr - 1 ) Hillslopes in Holland soil WY2008 WY2009 JHS4 117 5500 25 11 1037 0.0002 0.0000 JHS7 84 3200 38 20 1225 0.0000 0.0000 JHS9 134 6700 31 13 1174 0.0000 0.0000 Mean 112 5100 31 14 1145 0.00 01 0.0000 s.d. 23 1600 6 5 87 0.0001 0.0000 Hillslopes in other soil types JHS1 120 3600 55 45 1167 0.0014 0.0000 JHS2 67 1100 55 38 1165 0.0009 0.0000 JHS3 249 11700 20 13 947 0.0001 0.0000 JHS5 82 3000 33 9 1133 0.0000 0.0000 JHS8 96 4200 50 27 12 06 0.0000 0.0000 JHS10 84 1300 30 15 979 0.0668 0.0000 JHS11 67 1200 25 20 962 0.0045 0.0000 Mean 109 3700 38 24 1080 0.0105 0.0000 s.d. 62 3600 14 13 108 0.0249 0.0000183

Appendix B. Area, elevation, and sediment production rates for hillslopes in th e Providence Creek watersheds for WY2004 through WY2009. ―NA‖ indicates that the fence did not collect valid data for that water year or was not yet constructed. ―**‖ indicates missing data for that water year.

Hillslope Area

(m 2 ) Fence

elevation (m) Sediment production rate (kg m - 2 yr - 1 )

WY2004 WY2005 WY2006 WY2007 WY2008 WY2009 PH1 3973 1970 0.0000 0.0000 0.0127 0.0000 0.0001 0.0000 PH2 3922 1973 0.0000 0.0000 0.0178 0.0000 0.0000 0.0000 PH3 4109 1914 0.0000 0.0000 0.1142 0.0000 0.0013 0.0000 PH4 14738 1925 0.0000 0.0000 0.0251 0.0000 0.0000 0.0001 PH5 6078 1904 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 PH6 7124 1916 0.0000 0.0006 0.0072 0.0000 0.0001 0.0000 PH7 12194 1942 0.0000 0.0000 0.0180 0.0000 ** 0.0000 PH8 4201 1960 0.0000 0.0015 0 .0919 0.0000 0.0030 0.0000 PH9 2986 1957 0.0000 0.0046 0.0523 0.0000 0.0005 0.0000 PH10 1814 1808 NA 0.0000 0.0230 0.0000 0.0008 ** PH11 1504 1833 NA 0.0000 0.0000 0.0000 0.0020 0.0000 Mean 5700 1918 0.0000 0.0006 0.0329 0.0000 0.0008 0.0000 s.d. 4200 54 0.0000 0.0014 0.0378 0.0000 0.0010 0.0000184

Appendix C. Area, elevation, and sediment production rates for hillslopes in the Bull Creek watersheds for WY2004 through WY2009. ―NA‖ indicates that the fence was not yet constructed or did not collect va lid data for that water year. ―**‖ indicates missing data.

Hillslope Area

(m 2 ) Fence

elevation (m) Sediment production rate (kg m - 2 yr - 1 )

WY2005 WY2006 WY2007 WY2008 WY2009 BH1 14892 2294 0.0023 0.0002 0.0000 0.0000 ** BH2 12606 2332 0.0029 0.003 7 0.0001 0.0018 0.0025 BH4 26186 2252 0.0017 0.0003 0.0000 ** 0.0000 BH5 22726 2361 0.0019 0.0022 0.0000 ** 0.0000 BH6 18562 2414 0.0013 0.0008 0.0000 0.0000 0.0001 BH7 38445 2426 0.0002 0.0001 0.0000 0.0000 0.0000 BH8 12182 ** NA 0.0000 0.0000   BH9 18235 **  NA 0.0014 0.0000 ** 0.0000 Mean 20500 2347 0.0017 0.0011 0.0000 0.0005 0.0004 s.d. 8700 68 0.0009 0.0013 0.0000 0.0009 0.0010185

Appendix D. Characteristics and sediment production rates for native surface road segments in Holland soil and other soil types in José Basin for WY2008 and WY2009. ―NA‖ indicates that the fence did not collect valid data for that water year, the fence was not yet constructed, or the segment was graded. ―**‖ indicates missing data. Segment Length Area Slope Fence elevation Sediment production rate

(m) (m 2 ) (%) (m) (kg m - 2 yr - 1 ) Native surface road segments in Holland soil WY2008 WY2009 JBT1 44 96 9 986 3.8 NA JBT14 43 91 10 1018 7.9 NA JNH5 36 89 12 1181 0.1 0.0 JNH7 32 96 2 1083 0.2 0.0 JNH8 30 59 14 101 4 1.7 0.1 JNH10 37 99 10 1124 0.2 0.1 JNH12 50 125 10 1141 0.1 0.4 JNH13 60 168 8 1137 1.5 0.1 JNH3 40 99 16 1215 NA 4.9 JNH6 29 75 10 1102 NA 7.4 JNH9 37 99 15 1025 NA 2.1 JNH11 30 90 12 1176 NA 0.4 JNH14 71 200 10 1137 NA 3.6 JPS11 40 120 10 101 4 NA 5.2 JPS12 36 72 6 1134 NA 0.0 JPS14 53 164 12 1093 NA 2.9 JPS15 31 84 5 1129 NA 0.2 JPS18 70 168 9 1114 NA 0.1 JPS19 28 70 10 1105 NA 0.2 JPS21 28 62 12 1087 NA 0.3 Mean 42 108 10 1109 1.9 1.6 s.d. 13 38 3 65 2.7 2.3 Native surface road segme nts in other soil types JNO4 56 151 4 1011 0.1 0.1 JNO6 31 83 5 982 0.0 0.1 JNO8 37 100 6 958 0.1 0.0 JNO9 32 102 11 920 0.6 4.2 JNU1 28 65 10 1102 NA 1.7 JNO1 48 115 4 ** NA 0.1 JNO3 35 76 11 1015 NA 12.9 JNO5 50 156 14 960 NA 1.3 JNO7 35 94 11 970 NA 8.7 JPS1 45 167 10 913 NA 3.0 JPS3 80 208 8 1034 NA 0.1 JPS4 51 153 3 968 NA 1.6 JPS5 88 246 10 954 NA 0.6 Mean 45 127 8 979 0.2 2.6 s.d. 17 48 3 47 0.3 3.9186

Appendix E. Characteristics and sediment production rates for native, gravel, and mi xed surface road segments as well as ditches adjacent to paved roads in the Providence Creek watersheds for WY2004 through WY2009. ―NA‖ indicates that the fence was not yet constructed or was removed for that water year. Segment Length

(m) Area (m 2 ) Slop e (%) Elevation

(m) Sediment production rate (kg m - 2 yr - 1 )

WY2004 WY2005 WY2006 WY2007 WY2008 WY2009 Native surface road segments PN1 35.0 95 6 1859 0.00 0.00 0.19 NA NA NA PN2 52.6 140 9 1846 0.52 1.90 3.99 NA NA NA PN3 23.9 69 4 1837 0.08 0.10 1.24 NA NA NA PN4 70.3 232 4 1865 0.12 0.93 0.89 NA NA NA PN5 139.3 514 7 1869 0.97 1.75 2.22 NA NA NA PN6 31.1 87 12 1961 0.17 0.12 0.89 0.00 0.21 0.24 PN7 54.9 179 7 1964 0.11 0.51 2.69 NA NA NA PN8 46.8 150 13 1747 1.07 4.24 6.17 0.22 0.04 0.29 PN 9 40.7 148 7 1770 0.04 0.00 0.32 0.00 0.01 0.01 PN10 49.3 164 9 1844 0.15 0.03 0.35 0.00 0.02 0.23 PN11 31.7 94 13 1878 0.11 0.19 0.69 0.00 0.08 0.06 PN12 36.3 98 11 1838 NA 0.75 3.42 NA NA NA PN13 68.0 218 7 1952 NA 0.24 0.51 0.01 0.37 0.03 Mean 52 1 68 8 1864 0.30 0.83 1.81 0.04 0.12 0.14 s.d. 30 115 3 66 0.38 1.21 1.81 0.09 0.14 0.12 Gravel surface road segments PG1 54.3 174 11 1965 0.14 0.30 1.02 0.02 0.02 0.21 PG2 26.0 73 19 1964 0.07 0.18 0.65 0.02 0.28 0.42 PG3 71.4 255 5 1748 0.00 0.04 0.16 0.23 0.00 0.01 PG4 67.3 244 3 1761 0.01 0.01 0.07 0.01 0.00 0.02 PG5 21.5 80 14 1766 0.03 0.12 0.87 0.00 0.03 0.09 PG6 67.1 239 13 1838 0.03 0.12 0.09 0.00 0.05 0.09 PG7 39.9 134 14 1871 0.02 0.20 0.74 0.00 0.02 0.19 Mean 50 171 11 1845 0.04 0.14 0.5 2 0.04 0.06 0.15 s.d. 21 78 6 93 0.05 0.10 0.40 0.09 0.10 0.14 Mixed surface road segments PM1 90.5 434 9 1822 0.19 0.79 2.63 0.07 0.58 0.16 PM3 150.7 652 9 1738 0.00 0.00 0.01 0.00 0.02 0.00 PM4 64.3 312 10 1760 0.02 0.21 0.37 0.00 0.18 0.01 PM5 75. 6 288 12 1841 0.34 0.43 1.48 0.00 0.44 0.36 Mean 95 422 10 1790 0.14 0.36 1.12 0.02 0.30 0.13 s.d. 38 167 1 49 0.16 0.34 1.19 0.03 0.26 0.17 Ditches adjacent to paved roads PDi1 80.8 372 6 1941 0.000 0.014 0.018 0.000 0.011 0.004 PDi2 178.6 925 9 1948 0.000 0.000 0.000 0.000 0.000 0.000 PDi3 36.8 162 4 1910 0.000 0.000 0.000 0.000 0.000 0.000 PDi4 116.8 594 10 1891 0.000 0.014 0.064 0.000 0.001 0.002 PDi5 45.9 237 4 1894 0.000 0.000 0.000 0.000 0.017 0.004 PDi6 57.9 311 11 1758 0.010 0.020 0.581 0. 000 0.046 0.031 PDi7 110.3 467 7 1822 0.000 0.000 0.000 0.000 0.000 0.001 Mean 90 438 7 1880 0.001 0.007 0.095 0.000 0.011 0.006 s.d. 50 258 3 68 0.003 0.008 0.216 0.000 0.017 0.011187

Appendix F. Characteristics and sediment production rates for nati ve surface road segments in the Bull Creek watersheds for WY2005 through WY2009. Segment Length Area Slope Fence elevation Sediment production rate (kg m - 2 yr - 1 )

(m) (m 2 ) (%) (m) WY2005 WY2006 WY2007 WY2008 WY2009 BN1 33.9 88 13 2237 0.33 0.09 0.00 0.0 9 0.39 BN2 58.5 152 10 2245 0.28 0.11 0.00 0.04 0.68 BN3 54.2 201 5 2251 0.11 0.18 0.00 0.01 0.06 BN4 112.8 384 8 2248 0.56 0.56 0.00 0.03 0.24 BN5 76.5 252 10 2285 0.17 0.02 0.00 0.00 0.00 BN6 47.5 176 7 2374 0.03 0.00 0.00 0.00 0.03 BN7 36.6 149 8 2403 0.17 0.08 0.00 0.00 0.05 BN8 67.8 251 12 2247 0.30 0.04 0.00 0.20 0.62 BN9 29.4 92 4 2340 0.00 0.00 0.00 0.00 0.00 Mean 57.5 194 9 2292 0.22 0.12 0.00 0.04 0.23 s.d. 26.0 92 3 64 0.17 0.18 0.00 0.07 0.27188

Appendix G. Characteristics and sediment production rates for gravel surface segments in José Basin for WY2008 and WY2009. ―NA‖ indicates that the fence did not collect valid sediment production data for that year.

Segment Length Area Slope Fence elevation Sediment production rate (kg m - 2 yr - 1 ) ID (m) (m 2 ) (%) (m) WY2008 WY2009 JGH3 37 89 12 1106 3.4 1.1 JGH4 22 57 14 1080 3.5 1.4 JGH5 26 66 10 1071 6.6 3.4 JGH6 55 137 9 1115 3.3 0.1 JGH10 39 119 12 1219 1.4 0.0 JGH7 80 192 17 1071 NA 0.3 JGH8 60 173 11 1115 NA 0.3 JGH9 45 112 16 1164 NA 0.1 JGH11 29 68 15 1199 NA 0.6 JGH12 49 114 20 1134 NA 0.3 JGH13 25 55 19 1108 NA 0.1 Mean 42 107 14 1126 3.6 0.7 s.d. 18 46 4 50 1.9 1.0Appendix H. Mean segment characteristics and waterbar data for six different road sections in José Basin pr ior to,

immediately after, and one water year following grading.

Prior to grading Immediately after grading One year after grading Segment length Waterbars Segment length Segment length Waterbars Road n Total Mean s.d. n % failed n Total Mean s.d

. n Total Mean s.d. Total % failed 9S61 71 3657 52 31 72 33 99 3670 37 20 83 3646 44 25 74 19 9S307 13 1864 143 302 17 82 44 1858 42 29 38 1841 45 38 10 50 9S304 21 1216 58 33 0 0 24 1239 52 33 23 1294 56 37 3 33 9S304A 4 225 56 37 6 83 6 220 37 14 9 2 22 25 10 32 25 9S61B 4 253 63 10 3 33 6 201 34 13 5 235 47 27 4 0 9S307A 11 860 78 71 11 64 18 847 47 37 14 840 60 57 5 0 Total 124 8075 65 104 109 47 197 8035 41 26 172 8078 47 34 128 22190

Appendix I. Characteristics and sediment production rates for road segments one and two years after grading in José Basin. * indicates that the production data are from WY2008, while all of the other data are from WY2009. Fence Length Area Slope Fence elevation Sediment production rate

(m) (m 2 ) (%) (m) (kg m - 2 yr - 1 ) One water year after grading JBT8* 32 70 6 1013 6.1 JBT9* 23 51 5 1007 12.8 JBT10* 24 60 8 988 13.0 JBT1 44 96 3 980 0.9 JBT2 46 150 6 982 6.8 JBT3 47 107 4 1002 4.4 JBT4 32 83 7 1036 9.9 JBT5 39 113 9 1034 5.5 JBT6 60 145 3 979 0.5 JBT7 41 1 19 3 969 7.0 JBT11 83 200 4 993 12.4 JBT12 56 118 7 1018 3.7 JBT13 37 82 5 1019 3.2 JBT14 43 91 2 1032 3.7 JBT17 25 69 14 1004 12.5 JBT18 49 147 60 998 9.4 JBT19 30 76 15 1009 20.4 JBT20 23 64 20 1022 3.1 JBT21 58 151 13 1022 7.2 JNH4 41 90 9 1 254 4.1 JNU1 28 65 1 1134 0.2 JNU2 29 67 3 1144 1.7 JPS16 45 153 2 1112 0.7 JPS17 85 204 5 1101 0.6 JPS20 16 43 8 1105 0.8 JPS22 32 90 3 1155 3.0 JPS23 29 78 5 1191 1.7 Mean 41 103 9 1048 5.7 s.d. 17 43 11 74 5.1 Two water years after grading JB T8 32 70 17 1156 2.4 JBT9 23 51 18 918 5.1 JBT10 24 60 14 847 8.2 Mean 26 60 16 974 5.3 s.d. 5 10 2 162 2.9