Storm Runoff Response from Roadbuilding and Logging on Small Watersheds in the Oregon Coast Range PDF Download

Author: Frederic Shu-kong Hsieh
Publisher:
ISBN:
Category : Forest roads
Languages : en
Pages : 298

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Book Description
The effects of roadbuilding, logging and burning upon stream runoff responses to individual storms are evaluated for the Alsea experimental watersheds, located in the Oregon Coast Range, The parameters analyzed are peak discharge, induced peak discharge, time-to-peak, and storm-runoff volume. The volume parameter is further sub-divided into total, quick, delayed, rising limb and falling limb flows. The control-watershed approach and linear regression method are utilized in this study. Calibration of the main stations at Flynn Creek (502 acres) and Deer Creek (750 acres) started in 1958. That for subwatershed DC II (138 acres) and DC III (100 acres) started in 1962. Watershed treatments included differing amounts of roadbuilding in the summer of 1965 and logging in 1966. The percentages of each watershed area subject to roadbuilding and to logging, respectively, were: Deer Creek main station, 3.7% and 26% of area in roads and logging, respectively, DC II, 3.1% and 20%, and DC III, 12, 1% and 72%, One small portion on the main watershed also received burning treatment in 1967, Flynn Creek was preserved in its natural state as a control. Data were analyzed through 1968. The storm-runoff responses of the treated watershed were found to relate to the type of treatment applied and percent of area treated, Roadbuilding resulted in significant increases in peak and induced peak discharges on DC III, which was subjected to the most intensive treatment. Logging generally demonstrated a more pronounced effect on runoff than did roadbuilding, since more vegetation was removed. Although highly significant augmentations in peak and induced peak discharges were detected after logging on subwatershed III, only minor changes were observed at the main Deer Creek outlet, The time-to-peak parameter was generally not affected by the land manipulations in this study. Separation of the annual data into the assumed recharging and recharged periods, based on antecedent soil moisture conditions, was selected for seasonal comparison over the use of an arbitrary cutoff date. Changes in flow volume parameters due to roadbuilding were insignificant. Rising limb flow on DC III as well as at the Deer Creek main station was moderately increased after logging. Although an increase in delayed flow and a decrease in quick flow occurred at the main station, these are considered to be compensating errors. Effects on design floods after treatments were indicated by the sharp increases in peak discharges, based upon flood frequency and statistical analyses.