I believe it is the case that when the Sauk made the turn to the west at Darrington to flow down the North Fork Stillaguamish valley the Suiattle portion of the Sauk continued to flow to the Skagit.

CM-
No doubt that the mass spawning salmon -pinks, chums, and sockeye can move a lot of fine sediment. I don't think increased numbers pinks would help the Stillaguamish Chinook. The conditions on the Stillaguamish are such there is more or less steady stream of material moving downstream. With every freshet the redds are re-buried by fine sediment and with every flood event there is significant bed load scour; both minimizing egg survival. I remember 20 years ago during the spring watching the pits of steelhead redds filling with sand in matter of a few days.

The stream bed of the Stillaguamish has been so altered that currently there is a huge over-lap between the pink and Chinook spawning areas. During pink years as soon as a Chinook begins spawning it is immediately joined by dozens to hundreds of pinks. Guessing that the pinks are attracted to the disturbed gravel. Again 20 years ago while mapping Chinook redds on 16 mile section of the North Fork Stillaguamish on non-pink years weekly surveys are more than adequate to identify each Chinook redd; nearly every redd would still have a active spawning or broom tail female on it. Those females would typically remain on the redd for 10 days or so. On pink years it was necessary to survey 3 times a week to catch a chinook female on the redd. On big pink years there would be so much pink spawning on top of the Chinook redds that the only chance of being sure of identifying a Chinook redd was to catch the female on the redd. During those pink year's doubt that the female Chinook redd resident time was 3 days. The constant pink harassment would lead to exhaustion and death for the Chinook in that time.

Curt