| Popis: |
Forest roads are a source of concern regarding the addition of chronic amounts of fine sediment into forest streams. Fine sediment in chronic amounts from forest roads can degrade aquatic habitat and impact salmonids. Research results show that the sediment from individual road segments is largely controlled by the amount of runoff from that road segment, which, in turn, is largely controlled by the nature of the interaction between the road segment and the hillslope where the road is located. The objective of this research is to better understand the hydrology of individual road segments in forested watersheds and the factors that influence runoff from these road segments. To better understand the hydrology of individual road segments, rainfall/runoff relationships were measured for 14 road segments in the Oregon Coast Range. For five of the road segments the road ditch was divided to allow runoff from the road surface to be measured on one side and intercepted hillslope water to be measured on the other side. In addition, 96 road segments in an 824 ha watershed were instrumented with either capacitance rods or crest gauges to observe the variability in the hydrology of individual road segments at a watershed scale. All road segments showed one of two types of hydrology: either ephemeral hydrology, where runoff occurred only in direct response to rainfall, or intermittent hydrology, where runoff occurred throughout most of the rainy, winter period. The type of hydrology was driven by whether or not the road incepted subsurface flow. Patterns of hydrology at the scale of individual road segments was observed at a watershed scale |
