THE NATURE AND TIMING OF POSTGLACIAL INCISION OF THE NICOLA RIVER, BRITISH COLUMBIA

Nicola valley, between Merritt and Spences Bridge in interior British Columbia is abundant in paraglacial river terraces formed as rivers incise through glacially deposited sediment. Whilst abundant, terrace formative processes, controls and ages in the valley remain unknown.

Preliminary mapping of the area was completed utilising aerial photography and DEMs to isolate preliminary terrace polygons. Fieldwork comprised of mapping terrace polygons, stratigraphic logging and sample collection for optical dating. Samples for optical dating comprise overbank fluvial sand found above river gravel representing the top of river terraces.

Elevation data collected at each terrace through differential GPS allows for interpolation and correlation of terrace levels across the Nicola. Optical dating of terrace overbank sand will elucidate numerous ages of floodplain abandonment (terrace formation). Dates will then be used in conjunction with elevation data to calculate the varying rates of valley incision through the paraglacial period. Tephra samples within terrace stratigraphy will also be dated, as an evaluation of optical dating techniques. Stratigraphic logs of each sample site will allow for stratigraphy to be compared between terraces both in the Nicola and surrounding valley reaches.

Resulting ages will be compared to similar, local terrace studies to begin differentiating local versus regional controls on terrace formation. Distinct post-glacial climate phases provide insight into expected past-incisional regimes, comparing terrace formative ages with such periods will further aid disentangling local versus regional controls.

This study aims to enhance the understanding of southern British Columbia’s deglacial response, specifically, post-glacial fluvial adjustment. Societally, it bears significance given that understanding sedimentation is crucial for agriculture, dredging and the salmon fishing industry in the region.