If you look at the shoreline shrubs, you will notice at the top of each plant clusters of debris that attached themselves when the river rose up into the vegetation. The shrubs acted like filters gathering needles, leaves and smaller twigs. Often these debris pods can be seen higher up in trees and shrubs giving a good indication of how high the river had risen during a past freshet, or release from a dam above. In this instance, all runoff upstream in the mountains (Oregon Coast Range).
SwittersB & Exploring 