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<br />0006G~ <br /> <br />. <br /> <br />. <br /> <br />ex i sted bet"een the cut and the uncut watershed~. Increases In size of <br /> <br />instantaneous peak flow appear related to the proportion of a watershed ,"here the soil <br /> <br />had been compacted during the logging and slash disposal. Size of'the peak flow <br /> <br />was increased mostly In the shelterwood cut watersheds where soils were compacted <br /> <br />on about 13 percent of the area, <br /> <br />The effect of soil 1'sturbances on peak flow may have significance for erosion <br /> <br />a nd culvert design in headwater areas and for sedi~ntation downstream. but Is <br /> <br />probably of 'lttle importance In flooding of lowlands downstream. Increases In annual <br /> <br /> <br />water yield under sustained yield forest management will not augment water supplies <br /> <br />appreciably In southwestern Oregon as a result of the study. <br /> <br /> <br />The results of the study as Indicated above do'not bear further comment <br /> <br />as the above statements ~ore or less give a review of the entire paper. <br /> <br />(10) Streamflow after Patch Lo in on Small dralna es within the Bul I Run Hunicl al <br />Watershed, Oreqon - U,S, Department of AgrIculture, Forest Service PNW-2 <br /> <br />As a result of this study, annual water yteld and the size of the peak flows <br /> <br />were not changed, but low flows decreased significantly after patch logging In <br /> <br />small watersheds. The research summary indicates that because of wetter soils <br /> <br />at the end of the growing season, logged watersheds Were hydrologically more <br /> <br />responsive to rainfall and exhIbited higher peak flows. This has caused the <br /> <br />1 <br /> <br />size of the peak flows in the fall to be greater the first year after timber <br /> <br />harvest In the Pacific Northwest, As revegetatIon proceeded/evapotranspiration <br /> <br />and fall peak flows tended toward their prelogging levels. After reviewing <br /> <br />the 1 iterature and apparently as a result of this review, it was stated that <br /> <br />~ ~~.:~ <br /> <br />the studies indicate the size of peak ftows may increase, decrease, or remain <br /> <br />unchanged after timber harvest, depending on what part or parts of the hydrologic <br /> <br />system are altered by timber harvest activity. <br /> <br />7 <br />