Rainfall-Runoff Prediction and the Effects of Logging: The Oregon Coast Range

摘要

Streamflow response to rainfall is controlled by the net water budget and the routing of rainfall to stream channels. In rain-dominated forested regions, including the Oregon Coast Range, water budget aspects of forest hydrology are better quantified than water routing. As a result, most of the commonly used forest hydrology models have been designed to assist in the analysis of seasonal or annual runoff volumes (Goldstein, et al. 1974; Troendle and Leaf, 1980; Silvey and Rosgen, 1981). The effects of timber harvesting on runoff volumes are reflected primarily through reductions in evapotranspirational demand and the corresponding increases in soil water content. The purposes of the report are to: (1) Describe the rainfall-runoff processes in the Oregon Coast Range, and review the results of studies in Western Oregon on the effects of timber harvesting on runoff. (2) Review and analyze available techniques for predicting the hydrologic effects of timber harvesting in rainfall-dominated regions. (3) Provide a review of the issue of sediment routing, channel stability, and the relationship between hydrology and channel morphology. (4) Provide additional analysis of the Alsea Watershed Study data (Harris, 1977) to better describe the effects of timber harvesting on high-flow durations and assess the potential for developing and validating simple storm-period rainfall-runoff prediction procedures.