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River classifications provide useful frameworks to understand complex fluvial landscapes and to manage freshwater ecosystems. Alluvial floodplains for rivers in low-relief glacially conditioned catchments of southern Ontario (Canada) are classified and tested using a sequence of multivariate statistical analyses. An original dataset of 109 floodplain sites is investigated using k-means clustering, principal component analysis, and discriminant analysis statistical approaches. Four primary floodplain types are proposed representing basic morphological, stratigraphical, and sedimentological characteristics. Classifications are successfully discriminated by two principal dimensions: (1) stream power-resistance; and (2) floodplain sedimentology. The latter is most efficiently represented by the availability of alluvial sand, and specifically a new variable defined as floodplain sand equivalent (FSE). Floodplain types are generally consistent with previous river classifications, however the glacial legacy requires refined classifications which account for inherited cobble bed materials and patterns of sand supply. Representing the residual variability of stream power-resistance correlations, a third explanatory dimension of sediment transport is suggested, and may explain some within-class variability in channel morphology. Balancing the opposing concepts of fluvial process domains and landform continuums, the potential for transitional floodplain types is also explored. The proposed first-order alluvial floodplain classifications provide a basis from which to further investigate geomorphological diversity within the context of complex glacial legacy effects in low-relief settings. Future research to reveal the spatial arrangement and linkages of distinct morphological groups within a regional landscape mosaic is expected to provide insights into patterns of post-glacial fluvial adjustment.

River valleys in the Humber River drainage basin have derived most of their morphology from processes occurring over the last 13 000 14C BP. Some of the valley reaches possess very distinct characteristics in terms of plan-view morphology, such as valley meandering and loop features along the valley sides. In this study, the valley morphology and stratigraphy of the upper Humber River basin are examined in order to assess the character of post-glacial valley evolution. Existing knowledge of late Wisconsinan and Holocene events has been considered to place this valley evolution into a regional context. Radiocarbon dating and digital elevation models suggest that the majority of valley incision occurred during or soon after regional deglaciation. Looping valley features and terrace patterns indicate that most valley morphology can be attributed to larger ancestral rivers. Although direct melt-water contributions are expected due to deglaciation, it is suggested that other processes due to the climatic and hydrogeologic effects of fluctuating proglacial lake levels also played a role.La morphologie des vallées dans le bassin de la rivière Humber découle essentiellement des processus ayant agi durant les derniers 13 000 14C BP. Certains segments de vallées présentent des caractéristiques uniques, particulièrement en ce qui a trait à la morphologie en plan : les boucles et les méandres. Dans cette étude, l’évolution des vallées du bassin de la rivière Humber au cours de l’Holocène et à la fin du Wisconsinien est étudiée de façon à déterminer les changements morphologiques et leur évolution vers leur forme actuelle. Des datations au 14C et des modèles d’élévation de terrain indiquent que la majeure partie de l’incision des vallées s’est produite durant ou peu après la déglaciation régionale. Les composantes des méandres de vallées et les patrons des terrasses fluviatiles indiquent que la morphologie actuelle des vallées est attribuable à des rivières ancestrales plus larges. Outre le rôle attendu des apports en eau de fonte associés à la déglaciation soient attendues, il est probable que les effets climatiques et hydrogéologiques des changements du niveau d’eau des lacs proglaciaires aient aussi joué un rôle dans l’évolution des vallées du bassin de la rivière Humber