Calculation of river width in relation to contributing area
It's a function of flow volume rather than catchment area. The flow rate can be vary by an order of 10 to 100 for the same catchment area, https://www.google.com/search?q=average+river+width+based+on+flow+volume&amp;tbm=isch There's so many variables like flow speed, inclination, bedrock type, flow rate.
This document includes the river width, it says there are too many variables.
https://www.nature.com/articles/s41598-019-44347-4
https://link.springer.com/article/10.1007/s11629-014-3265-0
here's a cool reference:
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082027
Did you know that a given type of rock gives mountains with all the same slope angles, i.e. there are mountains with ravines averaging 23 or 14 or 33 or 50% for the same mountain group, and screes inclines are rarely an irregular mix.