The length and volume of granitic sediment deposits were measured annually over a 4.5-year period below 6.6 km of forest roads constructed on headwater watersheds in the mountains of Idaho. Sediment deposits were identified by source of runoff, location of the deposit terminus, and various site factors including descriptors of hillside sediment storage capacity. Prediction equations were developed using linear regression for travel distance of sediment originating from fill slopes, rock drains, and culverts, with r2 values ranging from 0.70 for fill slopes to 0.91 for culverts.Cumulative volume of erosion and length of obstructions on the hillside were statistically significant variables in the equation for fills and rock drains; hillside gradient and runoff source area also appeared in the equation for culverts. Sensitivity analysis showed that the volume of erosion was the most sensitive variable in all cases. A dimensionless relationship relating the volume of sediment storage on slopes to sediment travel distance was also developed. This study makes it possible for land managers to assess the risk of sediment delivery to channels from alternative road designs, locations, and erosion control practices and provides a means to evaluate the cumulative effects of past road construction on sedimentation.(KEY TERMS: erosion; sedimentation; land use planning; forest hydrology; forest roads; granitic soil; sediment budgets; sediment delivery.)

Erosion and sedimentation data from research watersheds in the Silver Creek Study Area in central Idaho were used to test the prediction of logging road erosion using the R1-R4 sediment yield model, and sediment delivery using the "BOISED" sediment yield prediction model. Three small watersheds were instrumented and monitored such that erosion from newly constructed roads and sediment delivery to the mouths of the watersheds could be measured for four years following road construction. The errors for annual surface erosion predictions for the two standard road tests ranged from +3 1.2 tihalyr (+15 percent) to -30.3 tfhalyr (-63 percent) with an average of zero tihalyr and a standard deviation of the differences of 18.7 t/halyr. The annual prediction errors for the three watershed scale tests had a greater range from -40.8 t/ha/yr (-70 percent) to +65.3 t/halyr (+38 percent) with a mean of -1.9 tlhalyr and a standard deviation of the differences of 25.2 tiha/yr. Sediment yields predicted by BOISED (watershed scale tests) were consistently greater (average of 2.5 times) than measured sediment yields. Hilislope sediment delivery coefficients in BOISED appear to be overly conservative to account for average site conditions and road locations, and thus over-predict sediment delivery. Mass erosion predictions from BOISED appear to predict volume well (465 tonnes actual versus 710 tonnes predicted, or a 35 percent difference) over 15 to 20 years, however mass wasting is more episodic than the model predicts.(KEY TERMS: sediment model; BOISED; erosion; sediment prediction; test.) JAWRAKetcheson, Megahan, and King

No abstract

A federal, state, and private partnership leveraged resources and employed a long-term, systematic approach to improve aquatic habitat degraded by decades of intensive forest management in Finney Creek, a tributary to the Skagit River of Northwest Washington State. After more than a decade of work to reduce sediment sources and the risk of landslides within the watershed, log jam installation commenced in 1999 and progressed downstream through 2010. Log jam design was adapted as experience was gained. A total of 181 log jams, including 60 floating log ballasted jams, were constructed along 12 km of channel. The goal was to alter hydraulic processes that affect aquatic habitat formation along 39 km of stream with emphasis on 18.5 km of lower Finney Creek. Aquatic habitat surveys over a five-year period show an increase in the area of large pools and an accompanying increase in residual and maximum pool depth in the lower river reach. Channel cross sections show a generally deeper channel at the log jams, better channel definition in the gravel deposits at the head of the log jams, and improved riffle and thalweg development below the log jams. Stream temperature in the upper river decreased by 1.0°F in the first three years, and 1.1°F in the lowest treated reach over nine years. There is a trend of less stream heating over the restoration time period. Photo points show that riparian vegetation is recolonizing gravel bars.

The United States and other countries spend millions of dollars annually on storm damage repairs. Most of this work is to repair existing roads and transportation facilities. Large amounts of repair work have been done on the low-volume road network of the U.S. Department of Agriculture Forest Service over the past three decades, particularly in the Pacific Northwest. Agencies cannot afford to build roads to be 100% storm resistant, or stormproof, but they can be made more storm resistant. Measures can be taken to reduce the risk of storm damage from any given event. The objectives of this paper are to identify the assessment process and discuss treatments that can be used to reduce road damage and environmental impacts. Storm damage risk reduction first involves an assessment of any given road, the natural setting, the value of the road, traffic use, and design standards. Because resources are always limited, roads in areas of high risk, in steep terrain, or in areas subject to flooding, and the most important roads, from both the infrastructure and environmental standpoints, should be prioritized for preventative work. Storm damage risk reduction measures include many maintenance, drainage improvement, and structural tasks. Roadway surface drainage structures such as ditches, cross drains, and rolling dips need to be clean, properly armored, and properly spaced to prevent the concentration of water. Drainage-crossing structures such as bridges, fords, and culverts need to have adequate capacity or at least be clear of debris, well armored, scour resistant, and functioning properly. Trash racks can be added. Marginally stable road cuts and fills can be modified and reinforced with vegetation or soil bioengineering treatments. Staying current with road maintenance is critical for proper road function during storms.