River and riparian dynamics and black cottonwoods in the Kootenay River Basin, British Columbia and Montana

The black cottonwood, Populus trichocarpa, provides the foundation for the riparian woodlands throughout southern British Columbia (B.C.) and western Montana (MT). To study the interaction of riparian dynamics and cottonwood ecology, the present study investigated the influence of the extreme 1995 Elk River flood on the riparian zone and cottonwood ecology, and the effects of flood flow attenuation by the Libby Dam on riparian processes and cottonwoodland ecology of the Kootenai(y) River. Four river reaches were studied: the free-flowing Elk River near Fernie, B.C., the free-flowing Upper Kootenay River, B.C., upstream from the Koocanusa Reservoir, the free-flowing Fisher River, MT, near the Kootenai junction, and the flow-attenuated Lower Kootenai River near Libby, MT.;The studies demonstrate that black cottonwoods require a dynamic hydrologic and geomorphic system with periodic flood events for continued replenishment. The observed loss of cottonwood recruitment along the Lower Kootenai River is thus the consequence of the flood flow attenuation due to the operation of the Libby Dam. (Abstract shortened by UMI.).