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This supplemental material contains three figures and four tables. The figures show an example of a GPR (ground-penetrating radar) image showing how hydraulic radii and cross-sectional areas were estimated for the former channels (fig.S1), GPR images showing the internal structure of anabranching channels and floodplains of the middle Obra (Poland) and Sió Valleys (Hungary) (fig.S2), and aerial images of the South Saskatchewan River (Canada) (fig.S3). The tables show data describing the geometry of channels preserved in ancient rock records (Table S1), results of a statistical test applied to verify whether the values of sinuosities of channels preserved in the top parts of the modern floodplains are statistically different from sinuosities of channels preserved in ancient fluvial records (Table S2), values of manning n coefficients and standard errors (Table S3), estimations of palaeodischarges and standard errors (Tables S4). Data regarding channel geometry, age of former channels, values of Manning hydraulic roughness coefficients, and palaeodischarges were created by Słowik (2013, 2014), and Słowik et al., (2020, 2021). Information about how the values of roughness coefficients, palaeodischarges, and channel belt widths were estimated, and uncertainties of the estimations, are shown in the main body of our paper. |
