The paraglacial geomorphology of the Fraser Lowland, southwest British Columbia and northwest Washington

• We reinterpret maps of the Fraser Lowland in the light of paraglaciation.
• The landsystem has transitioned from glacial through marine to fluvial over time.
• Major drivers of the transitions are relative sea level and sediment source changes.
• Sediment wave and exhaustion models are useful to describe paraglacial transitions.
• Anthropogenic activity has already impacted the incidence of natural hazards.

The Fraser Lowland is interpreted as a complex paraglacial landsystem in the sense that all its landform units, landform and sediment associations, and thus the whole landsystem have been modified by nonglacial processes conditioned by glaciation. The late Pleistocene and Holocene processes of modification include slope erosion, glacimarine, marine, glacifluvial, fluvial, glacilacustrine, lacustrine, organic, mass movement, and aeolian. This complex paraglacial landsystem has transitioned from proglacial through marine to its present dominantly fluvial character. Landforms representative of each sediment redistribution process are described and a conceptual model is developed with relative sea level and sediment source changes as the primary drivers. The sediment wave and sediment exhaustion models are compared and illustrated in the context of this paraglacial land system. Anthropogenic modification during the past century (the Anthropocene) has complicated the paraglacial story and is shown to impact the incidence of natural hazards, especially in the context of hydroclimate change.