Figure S1. Example of river cross-section geometry. (a) shows the river
center line in red and ICESat-2 global geolocated photon (ATL03)
measured heights. (b) shows the exposed topography of the river channel
measured by ICESat-2 ALT03 in low-flow seasons, shown in gray points.
The solid red line is the smoothed values of ICESat-2 ALT03. The
submerged topography is delineated under the assumption that the channel
cross-section geometry follows the power law relationship described in
(Lawrence, 2007), shown in a solid blue line. The parameters that need
to be optimized are submerged depth (distance between ICESat-2
measurements and river bed) and beta (shape parameter).
Figure S2