Changes in storm hydrographs after roadbuilding and selective logging on a coastal watershed in northern California

Abstract

Abstract - The effects of road building and selective tractor harvesting on storm peak flows and storm volumes were assessed for a small (424 hectare) coastal watershed in Northern California. Two watersheds, the North and South Fork of Caspar Creek were calibrated from 1962 to 1967 while no treatments took place. Roads were then built on the South Fork, and the two watersheds were monitored until 1971. Between 1971 and 1973 the South Fork was selectively tractor logged, removing 60 percent of the timber volume. The storm flows were monitored until 1976. Only the very small (566 l/s or less) storm peaks or volumes (121 kiloliters or less) were increased after roadbuilding and logging. Roadbuilding alone significantly (p < 0.10) increased the small storm peaks approximately 20 percent, but did not affect the storm volumes. Logging increased both the peaks and volumes of the small storms by about 80 percent and 40 percent respectively. The large storm peaks and volumes were not significantly increased by either roads or logging, even though over 15 percent of the watershed was compacted in roads, skidtrails and landings. The increase in small storm peaks and volumes are not considered significant to the stream's stability or sediment regime

Citation

Wright, Kenneth A. 1985. Changes in storm hydrographs after roadbuilding and selective logging on a coastal watershed in northern California. M.S. thesis, Humboldt State University, Arcata, California. 55 p.