ABSTRACT: Changes in streamflow peaks following timber harvest of a coastal British Columbia watershed

CGRG Bibliography of Canadian Geomorphology
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Abstract

One of the concerns of land managers in coastal British Columbia, Canada, is the probability of increased streamflow peaks after forest harvesting, causing impairment of fish habitat and domestic water supplies caused by erosion and debris torrents. An examination was made of the effects of forest harvest on streamflow peaks for two distinct seasons, the late fall-winter season (November-March), when peak streamflow is generated by rain on a melting snowpack, and the summer season (mid June-November) when snowmelt has little, if any, influence on the hydrograph. Jamieson Creek and Elbow Creek basins were established in 1969 as treatment and control basins, respectively, of a paired-basin experiment in a drainage basin of the Vancouver, British Columbia, municipal water supply area. Changes in streamflow peaks following clear-cutting of 19.2% of Jamieson Creek experimental basin were determined. Winter storm peaks, which usually result from rain on melting snowpacks, showed a treatment-induced increase of a maximum 13.5%. There was no indication that the increases were limited to a particular storm-size class. Summer storm peaks showed no treatment-induced increase although both summer and winter storms showed significant post-treatment increase, presumably from changes in precipitation patterns resulting in storms of greater total precipitation. Peak winter flows were highly correlated with snowmelt rates. There was no difference in size of peak flow or in lag time between peak snowmelt and peak streamflow whether or not melt rates were greater in the forest than in the clearcut

Bibliography of Canadian Geomorphology