Reducing Sediment Production from Forest Roads during Wet-Weather Hauling

Abstract

Forest roads produce fine sediment with traffic during wet weather. If the forest road is connected to a stream, it can be a source of turbidity and fine sediment, which may be detrimental to aquatic organisms, especially salmonids. The goal of this work was to investigate turbid runoff during wet-weather use from the pavement of forest roads designed to reduce sediment production. This research tested alternatives for road pavements that were designed specifically to minimize turbid runoff caused by subgrade mixing during wet-weather hauling. Alternative designs of the pavement for unbound aggregate roads influenced the production of sediment, but results were not consistent; the pavement treatments produced different results across different research locations. There was no statistically significant treatment effect. This factor suggested that fine sediment in surface runoff did not originate from the subgrade but rather from the surface aggregate. Road managers who want to minimize the production of sediment from forest roads should be concerned with the unbound aggregate pavement rather than the subgrade. Road segments that developed ruts produced considerably more sediment than road segments where ruts did not form. Thus, to minimize sediment production during wet-weather hauling, managers should design the aggregate pavement to resist rut formation and with consideration of the availability of fine sediment in the aggregate.