After reading about the Red River case, the question occurred to me; can you have boundary change due to accretion after an Avulsion has occurred? It would seem that it couldn't. After the Avulsion the boundary is locked into its pre-Avulsion configuration, how can any accretion to new course of a river change that?
I'm sure like everything else with riparian boundary theory...it depends. I have never seen the outcome of an accretive vs. avulsive case that made any sense at all.
But I avoid reading ANYTHING that has to do with the Red River boundary between Oklahoma and Texas. There has been continuing litigation of one sort or the other for 200 years.
The river actually is owned by Oklahoma. That took the first 100 years to prove. Now I believe Texas had established the vegetation line or high bank to settle ownerships on the south side of the river. Now I guess the BLM is refuting the Texas definition and establishing their own high bank.
You may want to check the history of the Ohio, Indiana, Kentucky Boundary, including this agreement www.nytimes.com/1981/10/21/us/kentucky-indiana-and-ohio-end-river-boundary-dispute.html
and https://supreme.justia.com/cases/federal/us/444/335/case.html
One man's accretion is another man's avulsion, is it not?
They're not making any more dirt (even if it's covered with water) the only difference is; where we draw the lines on top of it.
The answer is very dependent upon the history of the change of the conditions, but generally, after an avulsive event where the waterway has chosen a new channel, the boundary becomes fixed at the last pre-avulsive natural channel. However, if the waterway moves back to that last natural pre-avulsive channel and then slow and imperceptible accretion and erosion resume from that point, the boundaries can become ambulatory once again.