As I am and old guy I can remember when Quigg Bros. dredged the Chehalis at what is now Friends Landing and barged it down stream. That is why the old docks existed to tie up the barges. Year after year they dredged and gravel migration from upstream filled it right back. When forced to stop they simply moved into an off chanell egress and dredged forward and the waste filled in behind which in the end left the lake at the landing.

Because it is only seen at low tide and not always exposed most do not realize the huge amount of gravel that moves downstream each year. It is way way more than most folks realize and I think your right SG it is fascinating.