[Insert Figures 2 and 3]
For deep beds \(d_{b}^{*}\) (\(>3.1\)), FR appears to be the best representation distribution of the empirical RTDs, consistent with Grant et al. (2020) who found that FR was a close approximation of the RTD predicted by the bedform pumping model in a quasi-infinite streambed (Figure \(2\) in their paper).