Influence of log truck traffic and road hydrology on sediment yield in western Oregon

Graduation date: 2015An understanding of the factors that influence surface erosion from roads is necessary to prevent and mitigate sediment production from forest roads. This study investigated the impacts of log truck traffic and road hydrology on sediment yield from ten forest road segments in the foothills of the Cascade Mountains of western Oregon.\ud The hydrology of individual road segments was classified as either "ephemeral" or "intermittent." Ephemeral hydrology occurs when Hortonian overland flow from the road surface is the primary source of runoff. Intermittent hydrology occurs when subsurface flow from the adjacent hillslope is intercepted by the road ditch and is a significant component of the road runoff. Data for sediment yield calculations were collected using a Turbidity Threshold Sampling (TTS) system that used in situ measurements of turbidity and discharge to calculate runoff and sediment yield for each road segment. A linear mixed effects model was fit to log transformed estimates of sediment yield.\ud Storm runoff volumes and log truck traffic were significant predictors of median sediment yield (t=17.05, DF=148, p