Rivers have a heritage but no beginning.
Luna Leopold and William Bull, from their classic paper “Base level, aggradation, and grade.” Proceedings of the American Philosophical Society 123.3 (1979): 168-202.
That’s the juicy pull quote, but it’s maybe too cryptic. Here’s more context:
Through geologic time even the first incipient channel system appearing on an emerging landmass changes in form, drainage network, and gradient as relief increases. There is continual modification, but at any stage the existing system is different from that which existed at a previous state, but has been influenced by that earlier stage.
(Apologies if that’s behind a paywall, I’m writing this sitting on a university campus and I can never tell when stuff like this is more broadly publicly available.)
I met Luna Leopold only once at a GSA meeting in San Diego, probably 1979, before a Perose Conference where I met King Hubbard, who was by that time Gandolf the White. Bill Bull was in the Subsidence Research Project in the USGS before my time in the project. I took Bill’s field geomorph course at U of A, where we mostly went on field trips on the weekends, between Christmas and New Year’s to the Pinacates, and over spring break to the San Andreas. He went off to New Zealand for several years but had returned before we visited. He had extolled the virtues of studying geomorph in such a tectonically active area. Wish I’d had a few days in the field with him there.
A variation of “no man ever steps in the same river twice”?