Trees and terrain: Floodplain characteristics and riparian cottonwood forests along southern Alberta rivers

This study investigated floodplain characteristics and associated cottonwood (Populus sp.) forests along the three southern tributaries of the Oldman River: the St. Mary, Belly and Waterton Rivers. Using topographic maps and aerial photographs, I measured floodplain widths, sinuosity and longitudinal profiles, and mapped land cover types along these rivers. The analyses revealed an association between the width of the floodplain and cottonwood forest abundance. Sparse cottonwood groves occurred along the confined St. Mary River reach, whereas cottonwood groves were extensive along the Belly River, which had a broad floodplain. Both width and cottonwood abundance were variable along the Waterton River. The floodplain width and associated cottonwood abundance influence the vulnerability of these riparian woodlands to human alteration and consequently the river valley characteristics should be considered in river resource management.