. Does harvest in west slope Douglas-fir increase peak flow in small forest streams?. Logging Environmental aspects; Forest influences; Stream measurements. flow, accounting for 56 percent of the variation; 6-hour intensity accounted for another 6 percent; 30-day antecedent pre- cipitation, an additional 4 percent; and day number of the streamflow peak, 2 percent. Total variation accounted for was 68 percent. The 30-day antecedent precipitation factor as an indicator of soil wetness might well be less variable after logging, as we have indicated that soils in clearcut areas tend to dry out les
. Does harvest in west slope Douglas-fir increase peak flow in small forest streams?. Logging Environmental aspects; Forest influences; Stream measurements. flow, accounting for 56 percent of the variation; 6-hour intensity accounted for another 6 percent; 30-day antecedent pre- cipitation, an additional 4 percent; and day number of the streamflow peak, 2 percent. Total variation accounted for was 68 percent. The 30-day antecedent precipitation factor as an indicator of soil wetness might well be less variable after logging, as we have indicated that soils in clearcut areas tend to dry out less than those under a complete forest cover. Similarly, after logging, we might expect streamflow to be more responsive to 6-hour intensity because more precipita- tion reaches the soil surface directly without first being intercepted by tree crowns. 30-Day Antecedent Precipitation Since the presence or absence of a forest cover could influence soil wetness through evapotranspiration processes but have little or no influence on either total precipitation the day of the storm or 6-hour precipitation intensity, we next examined the 30-day antecedent precipitation (an indicator of soil wetness) in relation to peak flow for the periods before and after logging for both the logged and unlogged watersheds (fig. 4). For the unlogged watershed, the regressions of peak flow to 30-day pre- cipitation for both the period before (line 1) and the period after (line 3) logging lOOr 90 80 - 70 - Line 1 unlogged watershed 1957-62 Line 2 clearcut watershed before logging 1957-62 Line 3 unlogged watershed 1965-69 Line 4 clearcut watershed after logging 1965-69. 8 16 24 32 30-DAY ANTECEDENT PRECIPITATION (INCHES) 40 Figure of 30-day antecedent precipitation on peak flows for logged and unlogged Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may n
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