Hydraulic geometry of Green and Birkenhead rivers: Southwestern Coast Mountains, British Columbia

Green and Birkenhead Rivers are located in the southwestern Coast Mountains of British Columbia, and the drainage in both basins is still strongly controlled by glacial features left after the retreat of the Vashon ice sheet. River slopes are imposed on the upland streams while the slope of the main valley streams is at least partly imposed by the glacial topography. Discharge in the streams is dominated by snowmelt during the summer though peak daily discharges frequently occur in autumn during autumn storms. At-a-station hydraulic geometry curves were determined by least square regression analysis for five sections from Water Survey of Canada gauging records. Velocity shows a more rapid than usual rate of adjustment, and resistance decreases more rapidly than the average as discharge increases. Residual values appear to be distributed about the regression lines in a systematic manner suggesting that the channel form fluctuates systematically over time. Similar results were found for ten other sections in the southwestern Coast Mountains. Downstream hydraulic geometries were determined for Green River and Birkenhead River. Bankfull discharge was assumed to have a constant recurrence interval of 2.33 years for both basins. Channel width shows a greater than usual increase in the downstream direction while velocity appears to remain constant or decrease.Arts, Faculty ofGeography, Department ofGraduat