Road Surface Erosion on the Jackson Demonstration State Forest: Results of a Pilot Study

This paper presents results of a 3 year pilot study of surface erosion on forest roads in the Jackson Demonstration State Forest in California’s coastal redwood region. Ten road segments representing a range of surface, grade, and ditch conditions were selected for the study. At each segment, settling basins with tipping buckets were installed to measure coarse sediment and total runoff. Laboratory analysis of Total Suspended Solids (TSS) samples from the runoff provided estimates of fine sediment production. Although the limited scope of our study prevented statistical analysis of site variables, several lessons emerged that may be useful to future studies. Total sediment production (fine and course) ranged from negligible (0.02 kg/m/yr) to more than 4.5 kg/m/yr, and varied greatly from year to year on most sites, in some cases by an order of magnitude. The share of TSS in yearly total sediment production also varied greatly from year to year. While site characteristics offer partial explanations of the results for each site, we found large variations among sites with similar characteristics. Lastly, the study required significant effort but was useful in providing site specific results; the variability in site characteristics adds to the challenge of understanding sediment production from forest roads.