Sediment production from forest roads in areas affected by the August Complex fire in Northern California
Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences
Committee Chair Name
Dr. Andrew Stubblefield
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Second Committee Member Affiliation
Community Member or Outside Professional
Third Committee Member Name
Third Committee Member Affiliation
HSU Faculty or Staff
Wildfire activity is increasing in California and is an important factor affecting erosion rates. Landscapes recently affected by wildfire, areas that have been salvage logged after a fire, and unpaved forest roads are all major sources of sediment which can impair water quality and negatively impact many aquatic species. Therefore, this study was conducted to quantify erosion rates from native and gravel surfaced forest road segments after the August Complex fire, evaluate the impact of salvage logging activities on sediment production from roads, and understand the effect of soil burn severity on sediment production from these road segments. Finally, this study tested predictions of sediment production from the Water Erosion Prediction Project packages against observed sediment production.
Sediment fences were constructed at 44 sites to capture runoff from forest roads in recently burned area of California’s coastal mountains. Each site consisted of a hydrologically distinct road segment and a catchment area uphill that drained to the road segment. A survey was conducted of each site to determine the cover types on the road and catchment, the length and width of the road segment, and the slope of the road and catchment.
Salvage logging in the catchment was found to play a significant role in sediment production, but the presence or absence of logging activity was a more significant factor than the size of the logged area. The level of traffic from heavy logging trucks did not have a significant effect on sediment production during the period when logging occurred, but a delayed effect was seen the following year. The percentage of bare soil in the catchment was found to be a significant predictor of sediment production, as well as the percentage of the road surface covered with vegetation. The total sediment production for each site was significantly correlated with the area of the road surface but not the catchment area, indicating that the road surface is a more significant driver of sediment production or transport.
The WEPP model consistently overpredicted sediment production, with a median value of 47 times the observed values. However, WEPP predicted sediment loads are significantly correlated with observed sediment loads, indicating that WEPP is much more accurate at comparing sediment loads between sites than predicting sediment loads directly.
Gigone, Zachary J., "Sediment production from forest roads in areas affected by the August Complex fire in Northern California" (2022). Cal Poly Humboldt theses and projects. 597.