. Does harvest in west slope Douglas-fir increase peak flow in small forest streams?. Logging Environmental aspects; Forest influences; Stream measurements. THE STUDY AND ANALYSIS The data on which this report is based came from experimental watersheds on the Forest Service's H. J. Andrews Ex- perimental Forest, an area typical of much of the west slopes of the central Cascade Range. The results should be generally applicable to forested areas in the Pacific Northwest west of the Cascade crest and other areas where the soils are relatively deep and porous and where precipitation associate
. Does harvest in west slope Douglas-fir increase peak flow in small forest streams?. Logging Environmental aspects; Forest influences; Stream measurements. THE STUDY AND ANALYSIS The data on which this report is based came from experimental watersheds on the Forest Service's H. J. Andrews Ex- perimental Forest, an area typical of much of the west slopes of the central Cascade Range. The results should be generally applicable to forested areas in the Pacific Northwest west of the Cascade crest and other areas where the soils are relatively deep and porous and where precipitation associated with major storms occurs primarily from warm, moist, stable air- masses which produce large quantities of precipitation at low intensities. The results would not necessarily apply to areas where precipitation is frequently of high intensity nor to those drainages that have a maximum peak from snowmelt in the spring. The latter is highly variable depending on accumulated snow and season of melt. Characteristics of the watersheds on the H. J. Andrews Experimental Forest are described in an earlier publication (Rothacher et al. 1967). Briefly, these watersheds are 150 to 250 acres in size and originally supported a dense stand of old-growth Douglas-fir on steep, northwest- facing topography. They receive over 90 inches of precipitation annually. Most of the precipitation comes as rain during the months of October through April. Inten- sity is generally light; but long-duration, steady rains may total 5 to 6 inches or more in a day and over 30 inches a month. Most of the watersheds' area is below 3,000 feet, and temperatures are mild. Usually a snowpack will form after the first of the year at elevations above 3, 500 feet; but below this, snow typically comes and goes during the winter months depend- ing on frontal weather activity. Although rain alone can produce excessively high streamflow, most major floods occur as a rain-on-snow event associated with an extremely wet soil ma
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