Validation of Baer-Babinet's Law using modern Landsat retrievals

Aakash Manapat 

In this study, I use a modern river erosion dataset created by Langhorst and Pavelsky (LP) in 2023 (LP 2023) to validate the long-standing contention behind Baer-Babinet's Law (BBL). This law postulates that rivers preferentially erode the right bank of rivers in the Northern Hemisphere and the left bank in the Southern Hemisphere, as a result of the Coriolis Force. Albert Einstein also published on this work in 1926. Since then, some modern authors have argued this effect is small and that local factors dominate the preferential erosion of rivers.

The LP 2023 dataset, derived from Landsat observations, validates BBL, and thus Einstein's theory. Interestingly, preferential riverbank erosion is observed for both large and slow moving rivers as well as small and fast moving rivers. This is inconsistent with conventional Geophysical Fluid Dynamics (GFD) theory, assessed via the Rossby number. Instead, a new scaling law is derived. Tentatively named the Babinet-Baer-Einstein (BBE) number, this number captures that BBL is consistent across all problem scales in LP 2023. The BBE number modifies the Rossby number by incorporating the effects of river depth and meander wavelength. Analysis of BBE reveals that it can be reduced to being purely a function of latitude, and is nearly independent of streamflow. This analysis indicates preferential erosion only ceases for rivers within 1-2° of the Equator.