This study uses digital elevation models and ground-penetrating radar to
quantify the relation between the surface morphodynamics and subsurface
sedimentology in the sandy braided South Saskatchewan River, Canada. A
unique aspect of the methodology is that both digital elevation model
and ground-penetrating radar data were collected from the same locations
in 2004, 2005, 2006 and 2007, thus enabling the surface morphodynamics
to be tied explicitly to the associated evolving depositional product.
The occurrence of a large flood in 2005 also allowed the influence of
discharge to be assessed with respect to the processproduct
relationship. The data demonstrate that the morphology of the study
reach evolved even during modest discharges, but more extensive erosion
was caused by the large flood. In addition, the study reach was
dominated by compound bars before the flood, but switched to being
dominated by unit bars during and after the flood. The extent to which
the subsurface deposits (the product') were modified by the surface
morphodynamics (the process') was quantified using the changes in
radar-facies recorded in sequential ground-penetrating radar surveys.
These surveys reveal that during the large flood there was an increase
in the proportion of facies associated with bar margin accretion and
larger dunes. In subsequent years, these facies became truncated and
replaced with facies associated with smaller dune sets. This analysis
shows that unit bars generally become truncated more laterally than
vertically and, thus, they lose the high-angle bar margin deposits and
smaller scale bar-top deposits. In general, the only fragments that
remain of the unit bars are dune sets, thus making identification of the
original unit barform problematic. This novel data set has implications
for what may ultimately become preserved in the rock record.