The fill slope and newly exposed bed are well covered by wild plants, which may encourage this bed relocation with erosion of the other bank. See bare bank above view center and Next. There are places on each curve where bank loss will be worse. This erosion is also at the greatest space between root wads, yet there was similar scour downstream with least spaces. Six months later, this cut was about doubled, with a vertical face back into valley base material.
Boulders are for protecting the bank and to brace the unsupported end.
Note depth of scour trench undercutting trunk and rocks which are sinking into the trench, with some rocks already lost. Sept. 99 Rosgen project with series of separated root wads. Note downstream erosion as eddy pit typical for any obstruction on a bank, see Next. Sod is hanging over the collapse, with boulders sinking into erosion trench. If the next root wad was there too, it was already gone.