Interchannel hydraulic geometry and hydraulic efficiency of the anastomosing Columbia River, southeastern British Columbia, Canada

The morphodynamics of the anastomosing channel system of upper Columbia River in southeastern British Columbia, Canada. is examined using an adaptation of conventional hydraulic geometry termed 'interchannel hydraulic geometry'. Interchannel hydraulic geometry has some of the characteristics of downstream hydraulic geometry but differs in that it describes the general bankfull channel form and hydraulics of primary and secondary channels in the anastomosing channel system. Interchannel hydraulic geometry generalizes these relationships and as such becomes a model of the geomorphology of channel division and combination. Interchannel hydraulic geometry of upper Columbia River, based on field measurements of flow velocity and channel form at 16 test sections, is described well by simple power functions: w(bf)= 3.24Q(bf)(0.64); d(bf) = 1.04Q(hf)(0.19); v(bf) = 0.30Q(bf)(0.17). These results, with other related measurements of flow resistance, imply that channel splitting leads to hydraulic inefficiency (higher flow resistance) on the anastomosing Columbia River. Because these findings differ front those reported in studies elsewhere, we conclude that hydraulic efficiency does not provide a general explanation for anabranching in river channels. Copyright (C) 2003 John Wiley Sons, Ltd.